Aerosol-generating system and aerosol-generating device with a resistive and an inductive heating arrangement

Abstract

There is provided an aerosol-generating device comprising a chamber for receiving at least a portion of an aerosol-generating article. The aerosol-generating device comprises an inductor element disposed adjacent to the chamber or in the chamber; a resistive heating element disposed adjacent to the chamber or in the chamber; at least one power supply for providing electrical power to the inductor element and resistive heating element; and control circuitry configured to control the supply of power from the at least one power supply to the inductor element and the resistive heating element. The control circuitry is configured to provide a first current to the inductor element, such that the inductor element generates an alternating magnetic field within the chamber. The control circuitry is further configured to provide a second current to the resistive heating element for heating the chamber.

Description

[0001] AEROSOL-GENERATING SYSTEM AND AEROSOL-GENERATING DEVICE WITH A RESISTIVE AND AN INDUCTIVE HEATING ARRANGEMENT

[0002] The present disclosure relates to an aerosol-generating system and an aerosolgenerating device for generating an aerosol from an aerosol-forming substrate.

[0003] It is known to evolve an aerosol from an aerosol-forming substrate of an aerosol-generating article by the application of heat to the substrate, without burning or combustion of the substrate. The aerosol-generating article may be cylindrical, like a cigarette, and the aerosolforming substrate may comprise tobacco material. It is known to apply heat to such an aerosol-generating article to heat the aerosol-forming substrate of the article using a heat source that is external to the aerosol-generating article.

[0004] However, an external heat source will tend to heat the aerosol-forming substrate unevenly. The aerosol-forming substrate closest to the heat source will be heated more than the aerosol-forming substrate in the centre of the aerosol-generating article, further from the heat source.

[0005] It is also known to heat the aerosol-forming substrate of such an article using a heat source located within the interior of the aerosol-forming substrate. In some aerosolgenerating systems the internal heat source is heated inductively using an induction coil positioned externally of the aerosol-generating article and a susceptor material located within a central region of the aerosol-generating article. Internally heating the aerosol-forming substrate avoids heat having to traverse through a wrapper to reach the aerosol-forming substrate. However, internally heating the aerosol-forming substrate also results in the aerosol-forming substrate being heated in a non-uniform manner, with heating of the substrate being greatest at or closest to the internal heat source and reducing with increasing distance away from the internal heat source into the substrate.

[0006] Non-uniform heating of the aerosol-forming substrate can mean that not all of the available volatile material is released from the aerosol-forming substrate. This is because increasing the level of heat applied to the substrate in order to fully extract the volatile material from the aerosol-forming substrate when using either external heating or internal heating of the substrate may result in unintended and undesired burning of the substrate close to the heat source, which can give rise to the generation of undesirable compounds and flavours.

[0007] It is therefore desired to provide an aerosol-generating system and an aerosolgenerating device that uniformly heats an aerosol-forming substrate to efficiently release the available volatile material from the aerosol-forming substrate.

[0008] According to the present disclosure, there is provided an aerosol-generating device. The aerosol-generating device may comprise a chamber for receiving at least a portion of an aerosol-generating article. The aerosol-generating device may comprise an inductor element disposed adjacent to the chamber or in the chamber. The aerosol-generating device may comprise a resistive heating element disposed adjacent to the chamber or in the chamber. The aerosol-generating device may comprise at least one power supply for providing electrical power to the inductor element and resistive heating element. The aerosolgenerating device may comprise control circuitry configured to control the supply of power from the at least one power supply to the inductor element. The aerosol-generating device may comprise control circuitry configured to control the supply of power from the at least one power supply to the resistive heating element. The control circuitry may be configured to provide a first current to the inductor element. The control circuitry may be configured to provide the first current to the inductor element such that the inductor element generates an alternating magnetic field within the chamber. The control circuitry may be configured to provide a second current to the resistive heating element. The control circuitry may be configured to provide the second current to the resistive heating element for heating the chamber.

[0009] According to a first aspect of the disclosure, there is provided an aerosol-generating device comprising: a chamber for receiving at least a portion of an aerosol-generating article; an inductor element disposed adjacent to the chamber or in the chamber; a resistive heating element disposed adjacent to the chamber or in the chamber; at least one power supply for providing electrical power to the inductor element and resistive heating element; and control circuitry configured to control the supply of power from the at least one power supply to the inductor element and the resistive heating element, wherein the control circuitry is configured to provide a first current to the inductor element, such that the inductor element generates an alternating magnetic field within the chamber, and wherein the control circuitry is configured to provide a second current to the resistive heating element for heating the chamber.

[0010] Advantageously using a separate inductor element and resistive heating element to provide inductive heating and resistive heating respectively means that the characteristics, shapes and materials of the inductor element and the resistive heating element may be individually adapted and optimised to more efficiently heat an aerosol-forming substrate. For example, the inductor element may be optimised for inductive heating and the resistive heating element may be optimised for resistive heating.

[0011] The first current may be an alternating current. The alternating current may have a first frequency. The control circuitry may be configured so that the inductor element is not supplied with the second current. The control circuitry may be configured so that the inductor element is not supplied with a direct current. The control circuitry may be configured so that the inductor element is solely supplied with the first current. Advantageously, this may provide minimal resistive heating of the inductor element, which may reduce the risk of a peripheral portion of an aerosol-forming substrate being overheated or burnt.

[0012] When supplied with the first current, the inductor element may generate an alternating magnetic field within the chamber to inductively heat one or more susceptors within an aerosol-generating article when the aerosol-generating article is received within the chamber. Advantageously, the aerosol-forming substrate within the aerosol-generating article may therefore be efficiently heated both externally and internally.

[0013] The aerosol-forming article may comprise the one or more susceptors. The one or more susceptors may be in the form of at least one strip or at least one rod or at least one particle. Advantageously, the construction of the aerosol-generating device may be simplified, as it is not required that the aerosol-generating device comprise a susceptor element. The one or more susceptors may be in the form of elongated particles. The elongated particles may be aligned with a longitudinal direction of the aerosol-generating article. The elongated particles may be aligned with a longitudinal direction of the aerosolforming substrate. The one or more susceptors may be in the form of one or more strips of susceptor material. The aerosol-generating article may comprise one or more strips of aerosol-forming substrate laminated with one on more strips of susceptor material. For example, the aerosol-generating article may comprise one or more strips of tobacco material laminated with one on more strips of susceptor material.

[0014] The aerosol-generating device may comprise the one or more susceptors. The one or more susceptors may be in the form of at least one blade or at least one pin. Advantageously, the one or more susceptors may be reused with multiple aerosol-forming articles. The one or more susceptors may be configured to be inserted into the aerosolgenerating substrate when the aerosol-generating article is received in the chamber. Advantageously, this may allow for a simpler and more sustainable form of aerosol-forming article to be used.

[0015] The second current may be a direct current. The control circuitry may be configured so that the resistive heating element is not supplied with the first current. The control circuitry may be configured so that the resistive heating element is not supplied with an alternating current. The control circuitry may be configured so that the resistive heating element is solely supplied with the second current. Advantageously, this may mean that the resistive heating element has no magnetic interaction with the inductor element.

[0016] The power supply may comprise a first DC power source. Advantageously, a range of suitable DC power sources may be suitable for use in the aerosol-generating device. The first DC power source may be a battery. The control circuitry may comprise a DC / AC converter connected to the first DC power source. Advantageously, a single DC power source may therefore be used to supply both the resistive heating element and the inductor element with power.

[0017] The DC / AC converter may include a Class-E power amplifier including a first transistor switch and an LC load network.

[0018] The control circuitry may be configured to provide the second current to the resistive heating element such that the resistive heating element is heated to at least 80°C. Advantageously, heating the resistive heating element to at least 80°C may ensure that the resistive heating element adequately heats the aerosol-forming substrate such that vapour may be produced. The control circuitry may be configured to provide the second current to the resistive heating element such that the resistive heating element is heated to no more than 210°C. Advantageously, heating the resistive heating element to no more than 210°C may ensure that the resistive heating element does not burn or scorch the aerosol-forming substrate, as this may otherwise produce undesirable compounds, creating an aerosol with a burnt taste for the user.

[0019] The control circuitry may be configured to provide the first current to the inductor element and the second current to the resistive heating element at different times.

[0020] For example, the control circuitry may be configured to provide the first current to the inductor element and then subsequently the second current to the resistive heating element. The control circuitry may be configured to provide the first current to the inductor element for a first time period. The control circuitry may be configured to provide the second current to the resistive heating element for a second time period after the first time period. Advantageously, the aerosol-forming substrate may be non-uniform, and heating the aerosol-forming substrate via inductive heating then subsequently by resistive heating may heat different portions of the aerosol-forming substrate at different times. As the aerosolforming substrate may be non-uniform, this may result in aerosol with aerosol characteristics being produced at different times.

[0021] The control circuitry may be configured to provide the second current to the resistive heating element and then subsequently the first current to the inductor element. The control circuitry may be configured to provide the second current to the resistive heating element for a first time period. The control circuitry may be configured to provide the first current to the inductor element for a second time period after the first time period. Advantageously, the aerosol-forming substrate may be non-uniform, and heating the aerosol-forming substrate via resistive heating then subsequently by inductive heating may heat different portions of the aerosol-forming substrate at different times. As the aerosol-forming substrate may be non-uniform, this may result in aerosol with aerosol characteristics being produced at different times. The control circuitry may be configured to detect when the user takes a puff on the system. For example, the control circuitry may be coupled to a pressure sensor, the pressure sensor configured to detect a pressure drop when the user takes a puff on the system. The control circuitry may be configured to supply power to the inductor element or the resistive heating element, or the inductor element and the resistive heating element, when the pressure sensor detects a pressure drop when the user takes a puff on the system. For example, the control circuitry may be configured to start the first time period in response to the user taking a puff on the system.

[0022] The control circuitry may comprise a user-activatable trigger. For example, the user- activatable trigger may comprise a button or a switch. The control circuitry may be configured to start the first time period in response to the user-activatable trigger being activated.

[0023] The control circuitry may be configured to end the first time period and start the second time period in response to: a predetermined number of puffs on the system being taken; or a predetermined time from a first puff on the system passing; or the user-activatable trigger being activated; or a combination of any one or more of the above.

[0024] The control circuitry may be configured to provide the first current to the inductor element and the second current to the resistive heating element in an alternating sequence. Advantageously, it may be beneficial to alternate inductive and resistive heating in order to avoid overheating of any part of the aerosol-forming substrate.

[0025] The control circuitry may comprise a microcontroller. The control circuitry may be configured to receive an inductor feedback signal from the inductor element and a resistive heating feedback signal from the resistive heating element. For example, the microcontroller may be configured to receive an inductor feedback signal from the inductor element and a resistive heating feedback signal from the resistive heating element.

[0026] The inductor feedback signal may comprise at least one of a voltage, a current or a conductance. For example, the inductor feedback signal may comprise a voltage and a current. The resistive heating feedback signal may comprise at least one of a voltage, a current or a conductance. For example, the resistive heating feedback signal may comprise a voltage and a current.

[0027] The control circuitry may be configured to provide the first current to the inductor element based on the inductor feedback signal. The control circuitry may be configured to provide the second current to the resistive heating element based on the resistive heating feedback signal. The inductor feedback signal may be dependent on a temperature of the susceptor. The resistive heating feedback signal may be dependent on a temperature of the resistive heating element. The control circuitry may be configured to adjust the first current provided to the inductor element dependent on the inductor feedback signal. The control circuitry may be configured to determine a temperature of the inductor element dependent on the inductor feedback signal. The control circuitry may be configured to adjust the first current provided to the inductor element dependent on the inductor feedback signal to maintain the temperature of the susceptor element at a susceptor target temperature or to follow a susceptor target temperature profile.

[0028] The control circuitry may be configured to adjust the second current provided to the resistive heating element dependent on the resistive heating feedback signal. The control circuitry may be configured to determine a temperature of the resistive heating element dependent on the resistive heating feedback signal. The control circuitry may be configured to adjust the second current provided to the resistive heating element dependent on the resistive heating feedback signal to maintain the temperature of the resistive heating element at a resistive heating target temperature or to follow a resistive heating target temperature profile.

[0029] When an alternating magnetic field is generated by supplying an alternating current in the inductor coil, the alternating magnetic field may induce an induced alternating current in the resistive heating element. Therefore, when the first current is supplied to the inductor element at the same time as the second current is supplied to the resistive heating element, the induced alternating current in the resistive heating element may affect the resistive heating feedback signal provided to the control circuitry. For example, the induced alternating current in the resistive heating element may modify the resistive heating feedback signal provided to the control circuitry. This may affect the ability of the control circuitry to accurately determine the temperature of the resistive heating element, and therefore affect the ability of the control circuitry to maintain the temperature of the resistive heating element at the resistive heating target temperature or to follow the resistive heating target temperature profile.

[0030] Therefore, the control circuitry may be configured to prevent the supply of the second current to the resistive heating element when the first current is supplied to the inductor element. For example, the control circuitry may be configured to prevent the supply of the direct current to the resistive heating element when the alternating current is supplied to the inductor element. Advantageously, when the control circuitry is configured to prevent the supply of the second current to the resistive heating element when the first current is supplied to the inductor element, the induced alternating current does not affect the resistive heating feedback signal. Therefore the control circuitry can more accurately determine the temperature of the resistive heating element. Similarly, the control circuitry may be configured to prevent the supply of the first current to the inductor element when the second current is supplied to the resistive heating element. The control circuitry may be configured to prevent simultaneous supply of the first current to the inductor element and the second current to the resistive heating element.

[0031] The control circuitry may be configured to provide the first current to the inductor element during on periods, and prevent the first current from being provided to the inductor element during off periods. The control circuitry may be configured to alternate the on periods with the off periods.

[0032] Specifically, the microcontroller may be configured to supply a switching voltage to the DC / AC converter in order to control the first current provided to the inductor element. In particular, the microcontroller may be configured to supply the switching voltage to a Field Effect Transistor of the DC / AC converter in order to control the first current provided to the inductor element. The switching voltage may have a rectangular profile. The switching voltage may comprise alternating on periods wherein the first current is provided to the inductor element, and off periods where the first current is prevented from being provided to the inductor element.

[0033] The temperature of the susceptor element may be controlled by adjusting the length of the on periods. For example, the control circuitry may be configured to adjust the length of the on periods to maintain the temperature of the susceptor element at the susceptor target temperature or to follow the susceptor target temperature profile.

[0034] The control circuitry may be configured to provide the first current to the inductor element in one or more pulses during each of the on periods. The pulses may comprise a plurality of separate pulses. The control circuitry may be configured to prevent the supply of the first current to the inductor element when not during the pulses.

[0035] The control circuitry may be configured to adjust the pulses during each of the on periods to control the temperature of the susceptor element. For example, the control circuitry may be configured to use pulse-width modulation to control the temperature of the susceptor element. The control circuitry may be configured to adjust one or more of a duration of each of the pulses, a number of each of the pulses, or a time gap between adjacent pulses during each of the on periods to control the temperature of the susceptor element. For example, the control circuitry may be configured to adjust the pulses during each of the on periods to maintain the temperature of the susceptor element at the susceptor target temperature or to follow the susceptor target temperature profile.

[0036] The pulses may occupy a proportion of each of the on periods. For example, the pulses may occupy 100% of each on period such that the first current is supplied to the inductor element during each on period for the entirety of each on period. As another example, the pulses may occupy 50% of each on period such that the first current is supplied to the inductor element during each on period for half the duration of each on period. The control circuitry may be configured to adjust the proportion of each of the on periods occupied by the pulses to control the temperature of the susceptor element. For example, the control circuitry may be configured to adjust the proportion of each of the on periods occupied by the pulses to maintain the temperature of the susceptor element at the susceptor target temperature or to follow the susceptor target temperature profile.

[0037] The on periods may be between 3000 milliseconds and 1 millisecond in length. The on periods may be between 500 milliseconds and 1 millisecond in length. Preferably, the on periods are between 100 milliseconds and 5 milliseconds in length. Preferably still, the on periods are between 50 milliseconds and 10 milliseconds in length. Even more preferably, the on periods are about 20 milliseconds in length.

[0038] The off periods may be between 3000 milliseconds and 1 millisecond in length. The off periods may be between 500 milliseconds and 1 millisecond in length. Preferably, the off periods are between 200 milliseconds and 10 milliseconds in length. Preferably still, the off periods are between 100 milliseconds and 50 milliseconds in length. Even more preferably, the off periods are about 70 milliseconds in length.

[0039] The control circuitry may be configured to provide the second current to the resistive heating element during the off periods. In particular, the control circuitry may be configured to provide the second current to the resistive heating element only during the off periods.

[0040] The temperature of the resistive heating element may be controlled by adjusting the length of the off periods. For example, the control circuitry may be configured to adjust the length of the off periods to maintain the temperature of the resistive heating element at the resistive heating target temperature or to follow the resistive heating target temperature profile.

[0041] The control circuitry may be configured to provide the second current to the resistive heating element in one or more pulses during each of the off periods. The pulses may comprise a plurality of separate pulses. The control circuitry may be configured to prevent the supply of the second current to the resistive heating element when not during the pulses.

[0042] The control circuitry may be configured to adjust the pulses during each of the off periods to control the temperature of the resistive heating element. For example, the control circuitry may be configured to use pulse-width modulation to control the temperature of the resistive heating element. The control circuitry may be configured to adjust one or more of a duration of each of the pulses, a number of each of the pulses, or a time gap between adjacent pulses during each of the off periods to control the temperature of the resistive heating element. For example, the control circuitry may be configured to adjust the pulses during each of the off periods to maintain the temperature of the resistive heating element at the resistive heating target temperature or to follow the resistive heating target temperature profile.

[0043] The pulses may occupy a proportion of each of the off periods. For example, the pulses may occupy 100% of each off period such that the second current is supplied to the resistive heating element during each off period for the entirety of each off period. As another example, the pulses may occupy 50% of each off period such that the second current is supplied to the resistive heating element during each off period for half the duration of each off period. The control circuitry may be configured to adjust the proportion of each of the off periods occupied by the pulses to control the temperature of the resistive heating element. For example, the control circuitry may be configured to adjust the proportion of each of the off periods occupied by the pulses to maintain the temperature of the resistive heating element at the resistive heating target temperature or to follow the resistive heating target temperature profile.

[0044] The control circuitry may be configured to provide the second current to the resistive heating element for reduced time periods. Each of the reduced time periods may be shorter than each of the off periods. The control circuitry may be configured to adjust the length of the reduced time periods to control the temperature of the resistive heating element. Advantageously, by providing the second current to the resistive heating element during the off periods but for reduced time periods shorter than the off periods, the control circuitry may avoid any overlap between the first current being provided to the inductor element and the second current being provided to the resistive heating element. As the alternating current induced in the resistive heating element may not instantaneously drop to zero when the first current applied to the inductor element is stopped, including time gaps between the reduced time periods and the periods when the first current is provided to the inductor element may advantageously reduce noise in the resistive heating feedback signal resulting from any alternating current induced in the resistive heating element. Also advantageously, the temperature of the resistive heating element may be controlled by adjusting the length of the reduced time periods. For example, the control circuitry may be configured to adjust the length of the reduced time periods to maintain the temperature of the resistive heating element at the resistive heating target temperature or to follow the resistive heating target temperature profile. The temperature of the resistive heating element may be controlled by adjusting the length of time gaps between the reduced time periods and the on periods. For example, the control circuitry may be configured to adjust the length of time gaps between the reduced time periods and the on periods to maintain the temperature of the resistive heating element at the resistive heating target temperature or to follow the resistive heating target temperature profile. This allows the control circuitry to maintain the temperature of the resistive heating element at the resistive heating target temperature, or to follow the resistive heating target temperature profile, using pulse-width modulation. The controller may be configured to perform a calibration process prior to alternating the on periods with the off periods. The controller may be configured to perform the calibration process immediately after the aerosol-generating device is switched on. The calibration process may comprise supplying the first current to the inductor element to determine at least one calibration variable of the susceptor element, such as a conductance value or a resistance value. In particular, the controller may be configured to perform the calibration process prior to supplying the second current to the resistive heating element.

[0045] The control circuitry may be configured to provide the first current to the inductor element and the second current to the resistive heating element simultaneously. Advantageously, in this way a larger amount of heat energy can be transferred to the aerosolforming substrate to generate a larger volume of aerosol, without either the susceptor or the resistive heating element reaching a temperature at which any part of the aerosol-generating article might combust. This may be particularly beneficial after start-up of the aerosolgenerating system or use of the aerosol-generating system in a cold environment, for example.

[0046] There are many possible ways to combine the inductive heating of the susceptor and the heating of the resistive heating element. For example, the inductive heating of the susceptor may be controlled to follow a particular profile over the course of a usage session and the resistive heating of the resistive heating element may be controlled to follow a different profile over the course of the usage session. The profiles may be chosen to provide consistent aerosol delivery over the course of the usage session as well as providing heating of substantially all of the aerosol-forming substrate.

[0047] The control circuitry may be configured to adjust the first current provided to the inductor element to maintain the temperature of the susceptor at a target temperature or to follow a target temperature profile. For example, the control circuitry may be configured to adjust an amplitude of the first current provided to the inductor element to maintain the temperature of the susceptor element at the susceptor target temperature or to follow the susceptor target temperature profile.

[0048] The control circuitry may be configured to adjust the second current provided to the resistive heating element to maintain the temperature of the resistive heating element at a target temperature or to follow a target temperature profile. For example, the control circuitry may be configured to adjust an amplitude of the second current provided to the resistive heating element to maintain the temperature of the resistive heating element at the resistive heating target temperature or to follow the resistive heating target temperature profile. The control circuitry may be configured to alter a magnitude of the alternating current during operation of the device to adjust an amount of heat generated in the susceptor by the inductor element as a result of the alternating current.

[0049] The control circuitry may be configured to adjust the frequency of the alternating current during operation of the device to adjust an amount of heat generated in the susceptor by the inductor element as a result of the alternating current.

[0050] The inductor element may at least partially surround the chamber. Advantageously, this may result in efficient heating of the susceptor element by the inductor element. The inductor element may surround the chamber.

[0051] The resistive heating element may at least partially surround the chamber. Advantageously, this may result in efficient heating of a periphery of the aerosol-forming substrate by the resistive heating element. The resistive heating element may surround the chamber.

[0052] The inductor element and the resistive heating element may surround the same longitudinal portion of the chamber.

[0053] The resistive heating element may be configured to heat a periphery of the chamber. Advantageously, if the inductor element and susceptor is configured to heat a central portion of the aerosol-forming substrate, this arrangement may ensure that no portion of the aerosolforming substrate is overheated.

[0054] The resistive heating element may extend from a first end of the chamber to a second end of the chamber.

[0055] When an alternating magnetic field is generated in the chamber by an alternating current in the inductor coil, depending on the configuration of the adjacent resistive heating element, the alternating magnetic field may induce an alternating current in an adjacent resistive heating element. The resistive heating element may be configured such that a total current induced in the resistive heating element by the alternating magnetic field is substantially zero.

[0056] The resistive heating element may comprise at least one primary portion. The resistive heating element may comprise at least one secondary portion. The resistive heating element may be configured such that a current induced in the at least one primary portion by the alternating magnetic field is approximately equal and opposite in direction to a current induced in the at least one secondary portion by the alternating magnetic field.

[0057] The resistive heating element may form an electrical pathway from a positive terminal of the control circuitry to a negative terminal of the control circuitry. The at least one primary portion may extend along the electrical pathway towards the negative terminal of the control circuitry in a clockwise direction about the chamber when viewed from the first end of the chamber. The second current may be considered to flow from the positive terminal of the control circuitry to a negative terminal of the control circuitry. The at least one primary portion may be arranged such that the second current flows in the at least one primary portion in a clockwise direction about the chamber when viewed from the first end of the chamber.

[0058] The at least one secondary portion may extend along the electrical pathway towards the negative terminal of the control circuitry in an opposite direction to the at least one primary portion when viewed from the first end of the chamber. For example, the at least one secondary portion may extend along the electrical pathway towards the negative terminal of the control circuitry in an anti-clockwise direction when viewed from the first end of the chamber.

[0059] The at least one secondary portion may be arranged such that the second current flows in the at least one secondary portion in an opposite direction to the second current in the at least one primary portion when viewed from the first end of the chamber. For example, the at least one secondary portion may be arranged such that the second current flows in the at least one secondary portion in an anti-clockwise direction about the chamber when viewed from the first end of the chamber.

[0060] A cumulative length of the at least one primary portion may be substantially equal to a cumulative length of the at least one secondary portion.

[0061] An alternating current induced in a resistive heating element may be particularly disadvantageous as the control circuitry would require filters to ensure the induced alternating current in the resistive heating element does not cause damage to any electronic components electrically connected to the resistive heating element. Advantageously, in the above arrangement, the resistive heating element is arranged such that any alternating current induced in resistive heating element in a direction towards the negative terminal of the control circuitry is equal to the current induced in resistive heating element in a direction towards the positive terminal of the control circuitry. As a result, the total alternating current induced in the resistive heating element between the positive terminal and the negative terminal of the control circuitry is at least significantly reduced, and is approximately zero. This minimising of total alternating current induced in the resistive heating element between the positive terminal and the negative terminal of the control circuitry means that filters to ensure the induced alternating current in the resistive heating element does not cause damage to any electronic components electrically connected to the resistive heating element are not required. This may therefore significantly reduce the complexity of the control circuitry.

[0062] The at least one primary portion may be integrally formed with the at least one secondary portion. The resistive heating element may comprise exactly one primary portion. The resistive heating element may comprise exactly one secondary portion. The primary portion and the secondary portion may extend from adjacent to the first end of the chamber to adjacent to a second end of the chamber.

[0063] The primary portion and the secondary portion may be electrically connected to the power supply at the second end of the chamber. A first end of the primary portion may be electrically connected to the positive terminal of the control circuitry. A first end of the secondary portion may be electrically connected to the negative terminal of the control circuitry.

[0064] The primary portion and the secondary portion may be directly connected to one another adjacent to the first end of the chamber. In particular, a second end of the primary portion opposite to the first end of the primary portion may be directly connected to a second end of the secondary portion opposite to the first end of the secondary portion.

[0065] The primary portion may be integrally formed with the secondary portion.

[0066] The primary portion and the secondary portion may be co-wound about the chamber such that the primary portion and the secondary portion are substantially parallel to one another. The primary portion and the secondary portion may be helically co-wound about the chamber.

[0067] Advantageously, this arrangement allows for a straightforward implementation of the above concept, and provides two co-wound portions in which the total induced alternating current between the positive terminal and the negative terminal of the control circuitry is at least significantly reduced, and is approximately zero.

[0068] The resistive heating element may be arranged in a serpentine shape. The resistive heating element may comprise two filaments arranged in a serpentine shape such that the two filaments are arranged substantially parallel to each other. In this arrangement, the resistive heating element may comprise a plurality of alternating primary portions and secondary portions as described above.

[0069] Advantageously, this arrangement allows for an implementation of the above concept in which the total induced alternating current in the serpentine resistive heating element between the positive terminal and the negative terminal of the control circuitry is at least significantly reduced, and is approximately zero.

[0070] The resistive heating element may be folded or curved to at least partially surround the chamber. Advantageously, the resistive heating element may therefore be printed onto a substantially flat and planar substrate prior to folding or curving to at least partially surround the chamber. This may provide a simple and reliable method of manufacture of the aerosolgenerating device. For example, the resistive heating element may be printed onto a substantially flat and planar polyimide substrate. The inductor element may be an inductor coil. The inductor coil may be a helical coil. The resistive heating element may be a resistive heating coil. The resistive heating coil may be a helical coil. The resistive heating coil and the inductor coil may be co-wound. Advantageously, this may result in a space-efficient arrangement in which the two separate heating systems may be positioned adjacent to the aerosol-forming substrate when the aerosol-forming article is received in the chamber.

[0071] The resistive heating coil may be wound about a winding axis. The inductor coil may be wound about the same winding axis as the resistive heating coil.

[0072] The aerosol-generating device may further comprise a jacket. The jacket may at least partially define the chamber.

[0073] The resistive heating element may be positioned on an outer surface of the jacket. The resistive heating coil may be wound around the outer surface of the jacket. Advantageously, the resistive heating element does not contact an outer surface of the aerosol-forming article when the aerosol-forming article is received in the chamber. This may protect the resistive heating element from damage during insertion of the aerosol-forming article into the chamber, and reduce the likelihood of overheating of the aerosol-forming article when the second current is supplied to the resistive heating element.

[0074] The inductor element may be positioned on the outer surface of the jacket. The inductor coil may be wound around the outer surface of the jacket. Advantageously, the inductor element does not contact the outer surface of the aerosol-forming article when the aerosol-forming article is received in the chamber. This may protect the inductor element from damage during insertion of the aerosol-forming article into the chamber.

[0075] The jacket may be a thermally conductive jacket. The thermal conductivity of the thermally conductive jacket may be at least 20 Wm’1K’1, preferably at least 30 Wm’1K’1, preferably still at least 40 Wm’1K’1, and even more preferably approximately 80 Wm’1K’1. Advantageously, a thermally conductive jacket ensure that heat is efficiently transferred from the resistive heating element to the aerosol-forming substrate.

[0076] The jacket may comprise an electrically insulating material. The jacket may consist of an electrically insulating material. The jacket may comprise a material having a relative magnetic permeability between 0.9 and 1.1 , preferably between 0.99 and 1.01. The jacket may therefore comprise a material which is substantially transparent to the alternating magnetic field. Advantageously, the jacket may therefore not substantially affect the alternating magnetic field induced within the chamber by the inductor element.

[0077] The jacket may comprise a ceramic. The ceramic may comprise alumina. Advantageously alumina has been found to possess suitable thermal properties to ensure that heat is efficiently transferred from the resistive heating element to the aerosol-forming substrate. The ceramic may comprise aluminium nitrate. Advantageously aluminium nitrate has been found to possess suitable thermal properties to ensure that heat is efficiently transferred from the resistive heating element to the aerosol-forming substrate.

[0078] The jacket may comprise a circular cross section. The jacket may comprise a substantially cylindrical shape. Advantageously, a cylindrical aerosol-forming article may therefore be easily inserted into the chamber by the user in any of 360 degrees of orientations.

[0079] The aerosol-generating device may further comprise a housing. The housing may at least partially surround the chamber. The jacket may be received in the housing.

[0080] The inductor element may be disposed within the housing. The inductor element may be disposed within the housing such that the inductor element at least partially surrounds the jacket and the resistive heating element. Advantageously, the jacket and the resistive heating element may therefore be manufactured together as a resistive heating assembly, which may be insertable into the housing during manufacture. This may allow for a degree of modularity during manufacture, in that different resistive heating assemblies may be inserted into different housing comprising different inductor elements. Furthermore, the resistive heating assembly may be replaceable from the housing comprising the inductor element.

[0081] The jacket may comprise a longitudinal axis. The jacket may comprise an inner surface. The inner surface may define the chamber. The jacket may comprise at least one groove defined on an inner surface of the jacket. The at least one groove may extend parallel to the longitudinal axis.

[0082] An airflow channel may be defined between the aerosol-generating article and the jacket when the aerosol-generating article is received in the chamber. The airflow channel may extend from a distal end of the jacket to a proximal end of the jacket.

[0083] The airflow channel may be defined between the aerosol-generating article and the at least one groove.

[0084] An airflow pathway may be defined from the distal end of the jacket, through the airflow channel to the proximal end of the jacket, and from a proximal end of the aerosolgenerating article, through the aerosol-generating article to a distal end of the aerosolgenerating article when the aerosol-generating article is received in the chamber. Advantageously, this may provide a straightforward airflow pathway solution which does not require airflow inlets defined through the housing.

[0085] The resistive heating coil may be wound around a winding axis coincident with the longitudinal axis of the jacket. The inductor coil may be wound around the winding axis coincident with the longitudinal axis of the jacket.

[0086] The inductor element may extend between a first end and a second end. An electrical resistance between the first end and the second end of the inductor element may be less than 250 milliohms, and preferably less than 150 milliohms, and preferably still approximately 100 milliohms. Advantageously, a relatively low electrical resistance ensures that minimal power is dissipated in the inductor element as heat, as the inductor element may not be configured to resistively heat the aerosol-forming substrate.

[0087] The resistive heating element may extend between a first end and a second end. An electrical resistance between the first end and the second end of the resistive heating element may be between 100 milliohms and 2000 milliohms, and preferably between 150 milliohms and 1500 milliohms, and preferably still between 200 milliohms and 1000 milliohms. Advantageously, a relatively high electrical resistance ensures that maximal power is dissipated in the resistive heating element as heat, as the resistive heating element may be configured to resistively heat the aerosol-forming substrate.

[0088] The electrical resistance of the resistive heating element may be greater than the electrical resistance of the inductor element. The electrical resistance of the resistive heating element may be at least 2 times greater than the electrical resistance of the inductor element. The electrical resistance of the resistive heating element may be at least 5 times greater than the electrical resistance of the inductor element. The electrical resistance of the resistive heating element may be at least 10 times greater than the electrical resistance of the inductor element.

[0089] The inductor element may comprise a first filament. The first filament may comprise a first cross sectional area.

[0090] The first cross sectional area may be defined in a first plane. The first cross sectional area may be perpendicular to the direction of extension of the first filament. The first cross sectional area may be perpendicular to the direction of extension of the first filament between the first end and the second end of the inductor element. The normal to the first plane defining the first cross sectional area may be perpendicular to the axis of winding. The first cross sectional area may be substantially constant between the first end and the second end of the inductor element. Advantageously, this arrangement may ensure that no portion of the inductor element between the first end and the second end of the inductor element generates more heating via resistive heating than any other portion.

[0091] The first cross sectional area may be perpendicular to the direction of flow of the first current. The first cross sectional area may be substantially rectangular in shape. Advantageously, a rectangular cross section has been found to increase the efficiency of the inductor element and reduce capacitive losses in the inductor element. Moreover, the size of the aerosol-generating device may therefore be reduced by using a rectangular cross section for the inductor element. The first cross sectional area may have a first width and a first thickness. The first width may be greater than the first thickness. The first width may be at least 5 times greater than the first thickness. For example, the first width may be at least 10 times greater than the first thickness. Preferably, the first width is at least 15 times greater than the first thickness. The first width may be between 0.1 millimetres and 5 millimetres. For example, the first width may be between 0.5 millimetres and 4 millimetres. Preferably, the first width is between 1 millimetre and 3 millimetres. The first thickness may be between 0.02 millimetres and 1 millimetre. The first thickness may be between 0.05 millimetres and 0.5 millimetres. Preferably, the first thickness is between 0.05 millimetres and 0.2 millimetres. The first width may be parallel to the longitudinal axis of the jacket. The first width may be parallel to the winding axis of the inductor coil. The first thickness may be perpendicular to the longitudinal axis of the jacket. The first thickness may be perpendicular to the winding axis of the inductor coil. Advantageously this shape and these dimensions of the inductor element have been found to provide minimal heating of the inductor element via resistive heating and provide strong coupling between the susceptor element and the inductor element. This results in more efficient heating of the susceptor element by the inductor element.

[0092] The resistive heating element may comprise a second filament. The second filament may comprise a second cross sectional area. The second cross sectional area may be defined in the first plane. The second cross sectional area may be defined in the same plane as the first cross sectional area. The second cross sectional area may be perpendicular to the direction of extension of the second filament. The second cross sectional area may be perpendicular to the direction of extension of the second filament between the first end and the second end of the resistive heating element. The normal to the first plane defining the second cross sectional area may be perpendicular to the axis of winding. The second cross sectional area may be substantially constant between the first end and the second end of the resistive heating element. The first cross sectional area may be greater than the second cross sectional area. The first cross sectional area may be at least 5 times greater than the second cross sectional area. For example, the first cross sectional area may be at least 10 times greater than the second cross sectional area. Preferably, the first cross sectional area is at least 15 times greater than the second cross sectional area. Preferably still, the first cross sectional area is at least 20 times greater than the second cross sectional area. Advantageously, a large ratio of first to second cross sectional areas means that resistive heating in the inductor element is reduced, and the majority of resistive heating occurs in the resistive heating element as intended.

[0093] The second cross sectional area may be perpendicular to the direction of flow of the second current. The second cross sectional area may be substantially circular in shape. The second cross sectional area may have a diameter between 0.1 millimetres and 0.4 millimetres. Advantageously this shape and these dimensions of the resistive heating element have been found to enable suitable heating of the resistive heating element via resistive heating. This results in more efficient heating of the periphery of the aerosol-forming substrate by the resistive heating element.

[0094] Preferably, the second cross sectional area is substantially rectangular in shape. Advantageously, a rectangular cross section has been found to increase the efficiency of the resistive heating element because a rectangular cross section provides a greater contact area with a periphery of the aerosol-forming substrate or the jacket. The second cross sectional area may have a second width and a second thickness. The second width may be greater than the second thickness. The second width may be at least 5 times greater than the second thickness. For example, the second width may be at least 10 times greater than the second thickness. Preferably, the second width is at least 25 times greater than the second thickness. The second width may be between 0.1 millimetres and 5 millimetres. For example, the second width may be between 0.2 millimetres and 2 millimetres. Preferably, the second width is between 0.5 millimetres and 0.7 millimetres. The second thickness may be between 0.005 millimetres and 0.5 millimetres. The second thickness may be between 0.01 millimetres and 0.1 millimetres. Preferably, the second thickness is between 0.02 millimetres and 0.05 millimetres. The second width may be parallel to the longitudinal axis of the jacket. The second width may be parallel to the winding axis of the inductor coil. The second thickness may be perpendicular to the longitudinal axis of the jacket. The second thickness may be perpendicular to the winding axis of the inductor coil. Advantageously this shape and these dimensions of the resistive heating element have been found to provide efficient resistive heating of a periphery of the aerosol-forming substrate.

[0095] The inductor element may comprise metal. The inductor element may comprise copper. The inductor element may comprise consist of copper. Advantageously, copper has been found to provide minimal heating of the inductor element via resistive heating and provide strong coupling between the susceptor element and the inductor element. This results in more efficient heating of the susceptor element by the inductor element.

[0096] The resistive heating element may comprise metal. The resistive heating element may comprise stainless steel. The resistive heating element may consist of stainless steel. Advantageously, stainless steel has been found to be a durable material with a resistivity suitable for maximising the heating of the resistive heating element via resistive heating. This results in more efficient heating of the periphery of the aerosol-forming substrate by the resistive heating element.

[0097] The inductor element may comprise a different material to the resistive heating element. The inductor element may consist of a different material to the resistive heating element.

[0098] According to a second aspect of the disclosure, there is provided an aerosolgenerating device comprising: a chamber for receiving at least a portion of an aerosol-generating article; an inductor element disposed adjacent to the chamber or in the chamber; and a resistive heating element disposed adjacent to the chamber or in the chamber; wherein the inductor element comprises a first filament comprising a first cross sectional area, the first cross sectional area defined in a first plane, wherein the resistive heating element comprises a second filament comprising a second cross sectional area, the second cross sectional area also defined in the first plane, and wherein the first cross sectional area is greater than the second cross sectional area.

[0099] The aerosol-generating device according to the second aspect may comprise any of the features described with respect to the first aspect of the disclosure.

[0100] For example, the inductor element may at least partially surround the chamber. Advantageously, this may result in efficient heating of the susceptor element by the inductor element. The inductor element may surround the chamber.

[0101] The resistive heating element may at least partially surround the chamber. Advantageously, this may result in efficient heating of a periphery of the aerosol-forming substrate by the resistive heating element. The resistive heating element may surround the chamber.

[0102] The inductor element and the resistive heating element may surround the same longitudinal portion of the chamber.

[0103] The resistive heating element may be configured to heat a periphery of the chamber. Advantageously, if the inductor element and susceptor is configured to heat a central portion of the aerosol-forming substrate, this arrangement may ensure that no portion of the aerosolforming substrate is overheated.

[0104] The inductor element may be an inductor coil. The inductor coil may be a helical coil. The resistive heating element may be a resistive heating coil. The resistive heating coil may be a helical coil. The resistive heating coil and the inductor coil may be co-wound. Advantageously, this may result in a space-efficient arrangement in which the two separate heating systems may be positioned adjacent to the aerosol-forming substrate when the aerosol-forming article is received in the chamber.

[0105] The resistive heating coil may be wound about a winding axis. The inductor coil may be wound about the same winding axis as the resistive heating coil.

[0106] The aerosol-generating device may further comprise a jacket. The jacket may at least partially define the chamber.

[0107] The resistive heating element may be positioned on an outer surface of the jacket. The resistive heating coil may be wound around the outer surface of the jacket. Advantageously, the resistive heating element does not contact an outer surface of the aerosol-forming article when the aerosol-forming article is received in the chamber. This may protect the resistive heating element from damage during insertion of the aerosol-forming article into the chamber, and reduce the likelihood of overheating of the aerosol-forming article when the second current is supplied to the resistive heating element.

[0108] The inductor element may be positioned on the outer surface of the jacket. The inductor coil may be wound around the outer surface of the jacket. Advantageously, the inductor element does not contact the outer surface of the aerosol-forming article when the aerosol-forming article is received in the chamber. This may protect the inductor element from damage during insertion of the aerosol-forming article into the chamber.

[0109] The jacket may be a thermally conductive jacket. The thermal conductivity of the thermally conductive jacket may be at least 20 Wm’1K’1, preferably at least 30 Wm’1K’1, preferably still at least 40 Wm’1K’1, and even more preferably approximately 80 Wm’1K’1. Advantageously, a thermally conductive jacket ensure that heat is efficiently transferred from the resistive heating element to the aerosol-forming substrate.

[0110] The jacket may comprise an electrically insulating material. The jacket may consist of an electrically insulating material. The jacket may comprise a material having a relative magnetic permeability between 0.9 and 1.1 , preferably between 0.99 and 1.01. The jacket may therefore comprise a material which is substantially transparent to the alternating magnetic field. Advantageously, the jacket may therefore not substantially affect the alternating magnetic field induced within the chamber by the inductor element.

[0111] The jacket may comprise a ceramic. The ceramic may comprise alumina. Advantageously alumina has been found to possess suitable thermal properties to ensure that heat is efficiently transferred from the resistive heating element to the aerosol-forming substrate. The ceramic may comprise aluminium nitrate. Advantageously aluminium nitrate has been found to possess suitable thermal properties to ensure that heat is efficiently transferred from the resistive heating element to the aerosol-forming substrate.

[0112] The jacket may comprise a circular cross section. The jacket may comprise a substantially cylindrical shape. Advantageously, a cylindrical aerosol-forming article may therefore be easily inserted into the chamber by the user in any of 360 degrees of orientations.

[0113] The aerosol-generating device may further comprise a housing. The housing may at least partially surround the chamber. The jacket may be received in the housing.

[0114] The inductor element may be disposed within the housing. The inductor element may be disposed within the housing such that the inductor element at least partially surrounds the jacket and the resistive heating element. Advantageously, the jacket and the resistive heating element may therefore be manufactured together as a resistive heating assembly, which may be insertable into the housing during manufacture. This may allow for a degree of modularity during manufacture, in that different resistive heating assemblies may be inserted into different housing comprising different inductor elements. Furthermore, the resistive heating assembly may be replaceable from the housing comprising the inductor element.

[0115] The jacket may comprise a longitudinal axis. The jacket may comprise an inner surface. The inner surface may define the chamber. The jacket may comprise at least one groove defined on an inner surface of the jacket. The at least one groove may extend parallel to the longitudinal axis.

[0116] An airflow channel may be defined between the aerosol-generating article and the jacket when the aerosol-generating article is received in the chamber. The airflow channel may extend from a distal end of the jacket to a proximal end of the jacket.

[0117] The airflow channel may be defined between the aerosol-generating article and the at least one groove.

[0118] An airflow pathway may be defined from the distal end of the jacket, through the airflow channel to the proximal end of the jacket, and from a proximal end of the aerosolgenerating article, through the aerosol-generating article to a distal end of the aerosolgenerating article when the aerosol-generating article is received in the chamber. Advantageously, this may provide a straightforward airflow pathway solution which does not require airflow inlets defined through the housing.

[0119] The resistive heating coil may be wound around a winding axis coincident with the longitudinal axis of the jacket. The inductor coil may be wound around the winding axis coincident with the longitudinal axis of the jacket.

[0120] The inductor element may extend between a first end and a second end. An electrical resistance between the first end and the second end of the inductor element may be less than 250 milliohms, and preferably less than 150 milliohms, and preferably still approximately 100 milliohms. Advantageously, a relatively low electrical resistance ensures that minimal power is dissipated in the inductor element as heat, as the inductor element may not be configured to resistively heat the aerosol-forming substrate.

[0121] The resistive heating element may extend between a first end and a second end. An electrical resistance between the first end and the second end of the resistive heating element may be between 100 milliohms and 2000 milliohms, and preferably between 150 milliohms and 1500 milliohms, and preferably still between 200 milliohms and 1000 milliohms. Advantageously, a relatively high electrical resistance ensures that maximal power is dissipated in the resistive heating element as heat, as the resistive heating element may be configured to resistively heat the aerosol-forming substrate.

[0122] The electrical resistance of the resistive heating element may be greater than the electrical resistance of the inductor element. The electrical resistance of the resistive heating element may be at least 2 times greater than the electrical resistance of the inductor element. The electrical resistance of the resistive heating element may be at least 5 times greater than the electrical resistance of the inductor element. The electrical resistance of the resistive heating element may be at least 10 times greater than the electrical resistance of the inductor element.

[0123] The first cross sectional area may be perpendicular to the direction of extension of the first filament. The first cross sectional area may be perpendicular to the direction of extension of the first filament between the first end and the second end of the inductor element. The normal to the first plane defining the first cross sectional area may be perpendicular to the axis of winding. The first cross sectional area may be substantially constant between the first end and the second end of the inductor element. Advantageously, this arrangement may ensure that no portion of the inductor element between the first end and the second end of the inductor element generates more heating via resistive heating than any other portion.

[0124] The first cross sectional area may be perpendicular to the direction of flow of the first current. The first cross sectional area may be substantially rectangular in shape. Advantageously, a rectangular cross section has been found to increase the efficiency of the inductor element and reduce capacitive losses in the inductor element. Moreover, the size of the aerosol-generating device may therefore be reduced by using a rectangular cross section for the inductor element. The first cross sectional area may have a first width and a first thickness. The first width may be greater than the first thickness. The first width may be at least 5 times greater than the first thickness. For example, the first width may be at least 10 times greater than the first thickness. Preferably, the first width is at least 15 times greater than the first thickness. The first width may be between 0.1 millimetres and 5 millimetres. For example, the first width may be between 0.5 millimetres and 4 millimetres. Preferably, the first width is between 1 millimetre and 3 millimetres. The first thickness may be between 0.02 millimetres and 1 millimetre. The first thickness may be between 0.05 millimetres and 0.5 millimetres. Preferably, the first thickness is between 0.05 millimetres and 0.2 millimetres. The first width may be parallel to the longitudinal axis of the jacket. The first width may be parallel to the winding axis of the inductor coil. The first thickness may be perpendicular to the longitudinal axis of the jacket. The first thickness may be perpendicular to the winding axis of the inductor coil. Advantageously this shape and these dimensions of the inductor element have been found to provide minimal heating of the inductor element via resistive heating and provide strong coupling between the susceptor element and the inductor element. This results in more efficient heating of the susceptor element by the inductor element.

[0125] The second cross sectional area may be perpendicular to the direction of extension of the second filament. The second cross sectional area may be perpendicular to the direction of extension of the second filament between the first end and the second end of the resistive heating element. The normal to the first plane defining the second cross sectional area may be perpendicular to the axis of winding. The second cross sectional area may be substantially constant between the first end and the second end of the resistive heating element. The second cross sectional area may be perpendicular to the direction of flow of the second current. The second cross sectional area may be substantially circular in shape. The second cross sectional area may have a diameter between 0.1 millimetres and 0.4 millimetres. Advantageously this shape and these dimensions of the resistive heating element have been found to enable suitable heating of the resistive heating element via resistive heating. This results in more efficient heating of the periphery of the aerosol-forming substrate by the resistive heating element.

[0126] Preferably, the second cross sectional area is substantially rectangular in shape. Advantageously, a rectangular cross section has been found to increase the efficiency of the resistive heating element because a rectangular cross section provides a greater contact area with a periphery of the aerosol-forming substrate or the jacket. The second cross sectional area may have a second width and a second thickness. The second width may be greater than the second thickness. The second width may be at least 5 times greater than the second thickness. For example, the second width may be at least 10 times greater than the second thickness. Preferably, the second width is at least 25 times greater than the second thickness. The second width may be between 0.1 millimetres and 5 millimetres. For example, the second width may be between 0.2 millimetres and 2 millimetres. Preferably, the second width is between 0.5 millimetres and 0.7 millimetres. The second thickness may be between 0.005 millimetres and 0.5 millimetres. The second thickness may be between 0.01 millimetres and 0.1 millimetres. Preferably, the second thickness is between 0.02 millimetres and 0.05 millimetres. The second width may be parallel to the longitudinal axis of the jacket. The second width may be parallel to the winding axis of the inductor coil. The second thickness may be perpendicular to the longitudinal axis of the jacket. The second thickness may be perpendicular to the winding axis of the inductor coil. Advantageously this shape and these dimensions of the resistive heating element have been found to provide efficient resistive heating of a periphery of the aerosol-forming substrate.

[0127] The first cross sectional area may be at least 5 times greater than the second cross sectional area. For example, the first cross sectional area may be at least 10 times greater than the second cross sectional area. Preferably, the first cross sectional area is at least 15 times greater than the second cross sectional area. Preferably still, the first cross sectional area is at least 20 times greater than the second cross sectional area. Advantageously, a large ratio of first to second cross sectional areas means that resistive heating in the inductor element is reduced, and the majority of resistive heating occurs in the resistive heating element as intended.

[0128] The inductor element may comprise metal. The inductor element may comprise copper. The inductor element may comprise consist of copper. Advantageously, copper has been found to provide minimal heating of the inductor element via resistive heating and provide strong coupling between the susceptor element and the inductor element. This results in more efficient heating of the susceptor element by the inductor element.

[0129] The resistive heating element may comprise metal. The resistive heating element may comprise stainless steel. The resistive heating element may consist of stainless steel. Advantageously, stainless steel has been found to be a durable material with a resistivity suitable for maximising the heating of the resistive heating element via resistive heating. This results in more efficient heating of the periphery of the aerosol-forming substrate by the resistive heating element.

[0130] The inductor element may comprise a different material to the resistive heating element. The inductor element may consist of a different material to the resistive heating element.

[0131] The aerosol-generating device may comprise at least one power supply for providing electrical power to the inductor element and resistive heating element. The aerosolgenerating device may comprise control circuitry configured to control the supply of power from the at least one power supply to the inductor element and the resistive heating element.

[0132] The control circuitry may be configured to provide a first current to the inductor element, such that the inductor element generates an alternating magnetic field within the chamber.

[0133] The control circuitry may be configured to provide a second current to the resistive heating element for heating the chamber.

[0134] The resistive heating element may extend from a first end of the chamber to a second end of the chamber.

[0135] When an alternating magnetic field is generated in the chamber by an alternating current in the inductor coil, depending on the configuration of the adjacent resistive heating element, the alternating magnetic field may induce an alternating current in an adjacent resistive heating element. The resistive heating element may be configured such that a total current induced in the resistive heating element by the alternating magnetic field is substantially zero.

[0136] The resistive heating element may comprise at least one primary portion. The resistive heating element may comprise at least one secondary portion. The resistive heating element may be configured such that a current induced in the at least one primary portion by the alternating magnetic field is approximately equal and opposite in direction to a current induced in the at least one secondary portion by the alternating magnetic field.

[0137] The resistive heating element may form an electrical pathway from a positive terminal of the control circuitry to a negative terminal of the control circuitry. The at least one primary portion may extend along the electrical pathway towards the negative terminal of the control circuitry in a clockwise direction about the chamber when viewed from the first end of the chamber.

[0138] The second current may be considered to flow from the positive terminal of the control circuitry to a negative terminal of the control circuitry. The at least one primary portion may be arranged such that the second current flows in the at least one primary portion in a clockwise direction about the chamber when viewed from the first end of the chamber.

[0139] The at least one secondary portion may extend along the electrical pathway towards the negative terminal of the control circuitry in an opposite direction to the at least one primary portion when viewed from the first end of the chamber. For example, the at least one secondary portion may extend along the electrical pathway towards the negative terminal of the control circuitry in an anti-clockwise direction when viewed from the first end of the chamber.

[0140] The at least one secondary portion may be arranged such that the second current flows in the at least one secondary portion in an opposite direction to the second current in the at least one primary portion when viewed from the first end of the chamber. For example, the at least one secondary portion may be arranged such that the second current flows in the at least one secondary portion in an anti-clockwise direction about the chamber when viewed from the first end of the chamber.

[0141] A cumulative length of the at least one primary portion may be substantially equal to a cumulative length of the at least one secondary portion.

[0142] An alternating current induced in a resistive heating element may be particularly disadvantageous as the control circuitry would require filters to ensure the induced alternating current in the resistive heating element does not cause damage to any electronic components electrically connected to the resistive heating element. Advantageously, in the above arrangement, the resistive heating element is arranged such that any alternating current induced in resistive heating element in a direction towards the negative terminal of the control circuitry is equal to the current induced in resistive heating element in a direction towards the positive terminal of the control circuitry. As a result, the total alternating current induced in the resistive heating element between the positive terminal and the negative terminal of the control circuitry is at least significantly reduced, and is approximately zero. This minimising of total alternating current induced in the resistive heating element between the positive terminal and the negative terminal of the control circuitry means that filters to ensure the induced alternating current in the resistive heating element does not cause damage to any electronic components electrically connected to the resistive heating element are not required. This may therefore significantly reduce the complexity of the control circuitry.

[0143] The at least one primary portion may be integrally formed with the at least one secondary portion.

[0144] The resistive heating element may comprise exactly one primary portion. The resistive heating element may comprise exactly one secondary portion. The primary portion and the secondary portion may extend from adjacent to the first end of the chamber to adjacent to a second end of the chamber.

[0145] The primary portion and the secondary portion may be electrically connected to the power supply at the second end of the chamber. A first end of the primary portion may be electrically connected to the positive terminal of the control circuitry. A first end of the secondary portion may be electrically connected to the negative terminal of the control circuitry.

[0146] The primary portion and the secondary portion may be directly connected to one another adjacent to the first end of the chamber. In particular, a second end of the primary portion opposite to the first end of the primary portion may be directly connected to a second end of the secondary portion opposite to the first end of the secondary portion.

[0147] The primary portion may be integrally formed with the secondary portion.

[0148] The primary portion and the secondary portion may be co-wound about the chamber such that the primary portion and the secondary portion are substantially parallel to one another. The primary portion and the secondary portion may be helically co-wound about the chamber.

[0149] Advantageously, this arrangement allows for a straightforward implementation of the above concept, and provides two co-wound portions in which the total induced alternating current between the positive terminal and the negative terminal of the control circuitry is at least significantly reduced, and is approximately zero.

[0150] The resistive heating element may be arranged in a serpentine shape. The resistive heating element may comprise two filaments arranged in a serpentine shape such that the two filaments are arranged substantially parallel to each other. In this arrangement, the resistive heating element may comprise a plurality of alternating primary portions and secondary portions as described above.

[0151] Advantageously, this arrangement allows for an implementation of the above concept in which the total induced alternating current in the serpentine resistive heating element between the positive terminal and the negative terminal of the control circuitry is at least significantly reduced, and is approximately zero. The resistive heating element may be folded or curved to at least partially surround the chamber. Advantageously, the resistive heating element may therefore be printed onto a substantially flat and planar substrate prior to folding or curving to at least partially surround the chamber. This may provide a simple and reliable method of manufacture of the aerosolgenerating device. For example, the resistive heating element may be printed onto a substantially flat and planar polyimide substrate.

[0152] According to a third aspect of the disclosure, there is provided an aerosol-generating device comprising: a chamber for receiving at least a portion of an aerosol-generating article; an inductor element disposed adjacent to the chamber or in the chamber; and a resistive heating element disposed adjacent to the chamber or in the chamber; wherein the inductor element comprises copper, and wherein the resistive heating element comprises stainless steel.

[0153] The aerosol-generating device according to the third aspect may comprise any of the features described with respect to the first and second aspects of the disclosure.

[0154] For example, the inductor element may at least partially surround the chamber. Advantageously, this may result in efficient heating of the susceptor element by the inductor element. The inductor element may surround the chamber.

[0155] The resistive heating element may at least partially surround the chamber. Advantageously, this may result in efficient heating of a periphery of the aerosol-forming substrate by the resistive heating element. The resistive heating element may surround the chamber.

[0156] The inductor element and the resistive heating element may surround the same longitudinal portion of the chamber.

[0157] The resistive heating element may be configured to heat a periphery of the chamber. Advantageously, if the inductor element and susceptor is configured to heat a central portion of the aerosol-forming substrate, this arrangement may ensure that no portion of the aerosolforming substrate is overheated.

[0158] The inductor element may be an inductor coil. The inductor coil may be a helical coil. The resistive heating element may be a resistive heating coil. The resistive heating coil may be a helical coil. The resistive heating coil and the inductor coil may be co-wound. Advantageously, this may result in a space-efficient arrangement in which the two separate heating systems may be positioned adjacent to the aerosol-forming substrate when the aerosol-forming article is received in the chamber.

[0159] The resistive heating coil may be wound about a winding axis. The inductor coil may be wound about the same winding axis as the resistive heating coil. The aerosol-generating device may further comprise a jacket. The jacket may at least partially define the chamber.

[0160] The resistive heating element may be positioned on an outer surface of the jacket. The resistive heating coil may be wound around the outer surface of the jacket. Advantageously, the resistive heating element does not contact an outer surface of the aerosol-forming article when the aerosol-forming article is received in the chamber. This may protect the resistive heating element from damage during insertion of the aerosol-forming article into the chamber, and reduce the likelihood of overheating of the aerosol-forming article when the second current is supplied to the resistive heating element.

[0161] The inductor element may be positioned on the outer surface of the jacket. The inductor coil may be wound around the outer surface of the jacket. Advantageously, the inductor element does not contact the outer surface of the aerosol-forming article when the aerosol-forming article is received in the chamber. This may protect the inductor element from damage during insertion of the aerosol-forming article into the chamber.

[0162] The jacket may be a thermally conductive jacket. The thermal conductivity of the thermally conductive jacket may be at least 20 Wm’1K’1, preferably at least 30 Wm’1K’1, preferably still at least 40 Wm’1K’1, and even more preferably approximately 80 Wm’1K’1. Advantageously, a thermally conductive jacket ensure that heat is efficiently transferred from the resistive heating element to the aerosol-forming substrate.

[0163] The jacket may comprise an electrically insulating material. The jacket may consist of an electrically insulating material. The jacket may comprise a material having a relative magnetic permeability between 0.9 and 1.1 , preferably between 0.99 and 1.01. The jacket may therefore comprise a material which is substantially transparent to the alternating magnetic field. Advantageously, the jacket may therefore not substantially affect the alternating magnetic field induced within the chamber by the inductor element.

[0164] The jacket may comprise a ceramic. The ceramic may comprise alumina. Advantageously alumina has been found to possess suitable thermal properties to ensure that heat is efficiently transferred from the resistive heating element to the aerosol-forming substrate. The ceramic may comprise aluminium nitrate. Advantageously aluminium nitrate has been found to possess suitable thermal properties to ensure that heat is efficiently transferred from the resistive heating element to the aerosol-forming substrate.

[0165] The jacket may comprise a circular cross section. The jacket may comprise a substantially cylindrical shape. Advantageously, a cylindrical aerosol-forming article may therefore be easily inserted into the chamber by the user in any of 360 degrees of orientations.

[0166] The aerosol-generating device may further comprise a housing. The housing may at least partially surround the chamber. The jacket may be received in the housing. The inductor element may be disposed within the housing. The inductor element may be disposed within the housing such that the inductor element at least partially surrounds the jacket and the resistive heating element. Advantageously, the jacket and the resistive heating element may therefore be manufactured together as a resistive heating assembly, which may be insertable into the housing during manufacture. This may allow for a degree of modularity during manufacture, in that different resistive heating assemblies may be inserted into different housing comprising different inductor elements. Furthermore, the resistive heating assembly may be replaceable from the housing comprising the inductor element.

[0167] The jacket may comprise a longitudinal axis. The jacket may comprise an inner surface. The inner surface may define the chamber. The jacket may comprise at least one groove defined on an inner surface of the jacket. The at least one groove may extend parallel to the longitudinal axis.

[0168] An airflow channel may be defined between the aerosol-generating article and the jacket when the aerosol-generating article is received in the chamber. The airflow channel may extend from a distal end of the jacket to a proximal end of the jacket.

[0169] The airflow channel may be defined between the aerosol-generating article and the at least one groove.

[0170] An airflow pathway may be defined from the distal end of the jacket, through the airflow channel to the proximal end of the jacket, and from a proximal end of the aerosolgenerating article, through the aerosol-generating article to a distal end of the aerosolgenerating article when the aerosol-generating article is received in the chamber. Advantageously, this may provide a straightforward airflow pathway solution which does not require airflow inlets defined through the housing.

[0171] The resistive heating coil may be wound around a winding axis coincident with the longitudinal axis of the jacket. The inductor coil may be wound around the winding axis coincident with the longitudinal axis of the jacket.

[0172] The inductor element may extend between a first end and a second end. An electrical resistance between the first end and the second end of the inductor element may be less than 250 milliohms, and preferably less than 150 milliohms, and preferably still approximately 100 milliohms. Advantageously, a relatively low electrical resistance ensures that minimal power is dissipated in the inductor element as heat, as the inductor element may not be configured to resistively heat the aerosol-forming substrate.

[0173] The resistive heating element may extend between a first end and a second end. An electrical resistance between the first end and the second end of the resistive heating element may be between 100 milliohms and 2000 milliohms, and preferably between 150 milliohms and 1500 milliohms, and preferably still between 200 milliohms and 1000 milliohms. Advantageously, a relatively high electrical resistance ensures that maximal power is dissipated in the resistive heating element as heat, as the resistive heating element may be configured to resistively heat the aerosol-forming substrate.

[0174] The electrical resistance of the resistive heating element may be greater than the electrical resistance of the inductor element. The electrical resistance of the resistive heating element may be at least 2 times greater than the electrical resistance of the inductor element. The electrical resistance of the resistive heating element may be at least 5 times greater than the electrical resistance of the inductor element. The electrical resistance of the resistive heating element may be at least 10 times greater than the electrical resistance of the inductor element.

[0175] The inductor element may comprise a first filament. The first filament may comprise a first cross sectional area.

[0176] The first cross sectional area may be defined in a first plane. The first cross sectional area may be perpendicular to the direction of extension of the first filament. The first cross sectional area may be perpendicular to the direction of extension of the first filament between the first end and the second end of the inductor element. The normal to the first plane defining the first cross sectional area may be perpendicular to the axis of winding. The first cross sectional area may be substantially constant between the first end and the second end of the inductor element. Advantageously, this arrangement may ensure that no portion of the inductor element between the first end and the second end of the inductor element generates more heating via resistive heating than any other portion.

[0177] The first cross sectional area may be perpendicular to the direction of flow of the first current. The first cross sectional area may be substantially rectangular in shape. Advantageously, a rectangular cross section has been found to increase the efficiency of the inductor element and reduce capacitive losses in the inductor element. Moreover, the size of the aerosol-generating device may therefore be reduced by using a rectangular cross section for the inductor element. The first cross sectional area may have a first width and a first thickness. The first width may be greater than the first thickness. The first width may be at least 5 times greater than the first thickness. For example, the first width may be at least 10 times greater than the first thickness. Preferably, the first width is at least 15 times greater than the first thickness. The first width may be between 0.1 millimetres and 5 millimetres. For example, the first width may be between 0.5 millimetres and 4 millimetres. Preferably, the first width is between 1 millimetre and 3 millimetres. The first thickness may be between 0.02 millimetres and 1 millimetre. The first thickness may be between 0.05 millimetres and 0.5 millimetres. Preferably, the first thickness is between 0.05 millimetres and 0.2 millimetres. The first width may be parallel to the longitudinal axis of the jacket. The first width may be parallel to the winding axis of the inductor coil. The first thickness may be perpendicular to the longitudinal axis of the jacket. The first thickness may be perpendicular to the winding axis of the inductor coil. Advantageously this shape and these dimensions of the inductor element have been found to provide minimal heating of the inductor element via resistive heating and provide strong coupling between the susceptor element and the inductor element. This results in more efficient heating of the susceptor element by the inductor element.

[0178] The resistive heating element may comprise a second filament. The second filament may comprise a second cross sectional area. The second cross sectional area may be defined in the first plane. The second cross sectional area may be defined in the same plane as the first cross sectional area. The second cross sectional area may be perpendicular to the direction of extension of the second filament. The second cross sectional area may be perpendicular to the direction of extension of the second filament between the first end and the second end of the resistive heating element. The normal to the first plane defining the second cross sectional area may be perpendicular to the axis of winding. The second cross sectional area may be substantially constant between the first end and the second end of the resistive heating element. The first cross sectional area may be greater than the second cross sectional area. The first cross sectional area may be at least 5 times greater than the second cross sectional area. For example, the first cross sectional area may be at least 10 times greater than the second cross sectional area. Preferably, the first cross sectional area is at least 15 times greater than the second cross sectional area. Preferably still, the first cross sectional area is at least 20 times greater than the second cross sectional area. Advantageously, a large ratio of first to second cross sectional areas means that resistive heating in the inductor element is reduced, and the majority of resistive heating occurs in the resistive heating element as intended. The second cross sectional area may be perpendicular to the direction of flow of the second current. The second cross sectional area may be substantially circular in shape. The second cross sectional area may have a diameter between 0.1 millimetres and 0.4 millimetres. Advantageously this shape and these dimensions of the resistive heating element have been found to enable suitable heating of the resistive heating element via resistive heating. This results in more efficient heating of the periphery of the aerosol-forming substrate by the resistive heating element.

[0179] Preferably, the second cross sectional area is substantially rectangular in shape. Advantageously, a rectangular cross section has been found to increase the efficiency of the resistive heating element because a rectangular cross section provides a greater contact area with a periphery of the aerosol-forming substrate or the jacket. The second cross sectional area may have a second width and a second thickness. The second width may be greater than the second thickness. The second width may be at least 5 times greater than the second thickness. For example, the second width may be at least 10 times greater than the second thickness. Preferably, the second width is at least 25 times greater than the second thickness. The second width may be between 0.1 millimetres and 5 millimetres. For example, the second width may be between 0.2 millimetres and 2 millimetres. Preferably, the second width is between 0.5 millimetres and 0.7 millimetres. The second thickness may be between 0.005 millimetres and 0.5 millimetres. The second thickness may be between 0.01 millimetres and 0.1 millimetres. Preferably, the second thickness is between 0.02 millimetres and 0.05 millimetres. The second width may be parallel to the longitudinal axis of the jacket. The second width may be parallel to the winding axis of the inductor coil. The second thickness may be perpendicular to the longitudinal axis of the jacket. The second thickness may be perpendicular to the winding axis of the inductor coil. Advantageously this shape and these dimensions of the resistive heating element have been found to provide efficient resistive heating of a periphery of the aerosol-forming substrate.

[0180] The inductor element may comprise consist of copper. Advantageously, copper has been found to provide minimal heating of the inductor element via resistive heating and provide strong coupling between the susceptor element and the inductor element. This results in more efficient heating of the susceptor element by the inductor element.

[0181] The resistive heating element may consist of stainless steel. Advantageously, stainless steel has been found to be a durable material with a resistivity suitable for maximising the heating of the resistive heating element via resistive heating. This results in more efficient heating of the periphery of the aerosol-forming substrate by the resistive heating element.

[0182] The inductor element may comprise a different material to the resistive heating element. The inductor element may consist of a different material to the resistive heating element.

[0183] The aerosol-generating device may comprise at least one power supply for providing electrical power to the inductor element and resistive heating element. The aerosolgenerating device may comprise control circuitry configured to control the supply of power from the at least one power supply to the inductor element and the resistive heating element.

[0184] The control circuitry may be configured to provide a first current to the inductor element, such that the inductor element generates an alternating magnetic field within the chamber.

[0185] The control circuitry may be configured to provide a second current to the resistive heating element for heating the chamber.

[0186] The resistive heating element may extend from a first end of the chamber to a second end of the chamber.

[0187] When an alternating magnetic field is generated in the chamber by an alternating current in the inductor coil, depending on the configuration of the adjacent resistive heating element, the alternating magnetic field may induce an alternating current in an adjacent resistive heating element. The resistive heating element may be configured such that a total current induced in the resistive heating element by the alternating magnetic field is substantially zero.

[0188] The resistive heating element may comprise at least one primary portion. The resistive heating element may comprise at least one secondary portion. The resistive heating element may be configured such that a current induced in the at least one primary portion by the alternating magnetic field is approximately equal and opposite in direction to a current induced in the at least one secondary portion by the alternating magnetic field.

[0189] The resistive heating element may form an electrical pathway from a positive terminal of the control circuitry to a negative terminal of the control circuitry. The at least one primary portion may extend along the electrical pathway towards the negative terminal of the control circuitry in a clockwise direction about the chamber when viewed from the first end of the chamber.

[0190] The second current may be considered to flow from the positive terminal of the control circuitry to a negative terminal of the control circuitry. The at least one primary portion may be arranged such that the second current flows in the at least one primary portion in a clockwise direction about the chamber when viewed from the first end of the chamber.

[0191] The at least one secondary portion may extend along the electrical pathway towards the negative terminal of the control circuitry in an opposite direction to the at least one primary portion when viewed from the first end of the chamber. For example, the at least one secondary portion may extend along the electrical pathway towards the negative terminal of the control circuitry in an anti-clockwise direction when viewed from the first end of the chamber.

[0192] The at least one secondary portion may be arranged such that the second current flows in the at least one secondary portion in an opposite direction to the second current in the at least one primary portion when viewed from the first end of the chamber. For example, the at least one secondary portion may be arranged such that the second current flows in the at least one secondary portion in an anti-clockwise direction about the chamber when viewed from the first end of the chamber.

[0193] A cumulative length of the at least one primary portion may be substantially equal to a cumulative length of the at least one secondary portion.

[0194] An alternating current induced in a resistive heating element may be particularly disadvantageous as the control circuitry would require filters to ensure the induced alternating current in the resistive heating element does not cause damage to any electronic components electrically connected to the resistive heating element. Advantageously, in the above arrangement, the resistive heating element is arranged such that any alternating current induced in resistive heating element in a direction towards the negative terminal of the control circuitry is equal to the current induced in resistive heating element in a direction towards the positive terminal of the control circuitry. As a result, the total alternating current induced in the resistive heating element between the positive terminal and the negative terminal of the control circuitry is at least significantly reduced, and is approximately zero. This minimising of total alternating current induced in the resistive heating element between the positive terminal and the negative terminal of the control circuitry means that filters to ensure the induced alternating current in the resistive heating element does not cause damage to any electronic components electrically connected to the resistive heating element are not required. This may therefore significantly reduce the complexity of the control circuitry.

[0195] The at least one primary portion may be integrally formed with the at least one secondary portion.

[0196] The resistive heating element may comprise exactly one primary portion. The resistive heating element may comprise exactly one secondary portion. The primary portion and the secondary portion may extend from adjacent to the first end of the chamber to adjacent to a second end of the chamber.

[0197] The primary portion and the secondary portion may be electrically connected to the power supply at the second end of the chamber. A first end of the primary portion may be electrically connected to the positive terminal of the control circuitry. A first end of the secondary portion may be electrically connected to the negative terminal of the control circuitry.

[0198] The primary portion and the secondary portion may be directly connected to one another adjacent to the first end of the chamber. In particular, a second end of the primary portion opposite to the first end of the primary portion may be directly connected to a second end of the secondary portion opposite to the first end of the secondary portion.

[0199] The primary portion may be integrally formed with the secondary portion.

[0200] The primary portion and the secondary portion may be co-wound about the chamber such that the primary portion and the secondary portion are substantially parallel to one another. The primary portion and the secondary portion may be helically co-wound about the chamber.

[0201] Advantageously, this arrangement allows for a straightforward implementation of the above concept, and provides two co-wound portions in which the total induced alternating current between the positive terminal and the negative terminal of the control circuitry is at least significantly reduced, and is approximately zero.

[0202] The resistive heating element may be arranged in a serpentine shape. The resistive heating element may comprise two filaments arranged in a serpentine shape such that the two filaments are arranged substantially parallel to each other. In this arrangement, the resistive heating element may comprise a plurality of alternating primary portions and secondary portions as described above.

[0203] Advantageously, this arrangement allows for an implementation of the above concept in which the total induced alternating current in the serpentine resistive heating element between the positive terminal and the negative terminal of the control circuitry is at least significantly reduced, and is approximately zero.

[0204] The resistive heating element may be folded or curved to at least partially surround the chamber. Advantageously, the resistive heating element may therefore be printed onto a substantially flat and planar substrate prior to folding or curving to at least partially surround the chamber. This may provide a simple and reliable method of manufacture of the aerosolgenerating device. For example, the resistive heating element may be printed onto a substantially flat and planar polyimide substrate.

[0205] According to the present disclosure, there is also provided an aerosol-generating system. The aerosol-generating system may comprise an aerosol-generating device according to the present disclosure. For example, the aerosol-generating system may comprise an aerosol-generating device according to the first, second or third aspects of the present disclosure. The aerosol-generating system may comprise an aerosol-generating article comprising an aerosol-generating substrate. The aerosol-generating article may be received in the chamber of the aerosol-generating device.

[0206] According to a fourth aspect of the disclosure, there is provided an aerosol-generating system comprising: an aerosol-generating device according to any preceding aspect of the present disclosure; and an aerosol-generating article comprising an aerosol-generating substrate, wherein the aerosol-generating article is received in the chamber of the aerosolgenerating device.

[0207] The aerosol-generating article may comprise one or more susceptors. The aerosolgenerating article may comprise one or more susceptors as described above with respect to the first aspect of the disclosure. For example, the one or more susceptors may be in the form of at least one strip or at least one rod or at least one particle. The one or more susceptors may be in the form of elongated particles. The elongated particles may be aligned with a longitudinal direction of the aerosol-generating article. The elongated particles may be aligned with a longitudinal direction of the aerosol-forming substrate. The one or more susceptors may be in the form of one or more strips of susceptor material. The aerosolgenerating article may comprise one or more strips of aerosol-forming substrate laminated with one on more strips of susceptor material. For example, the aerosol-generating article may comprise one or more strips of tobacco material laminated with one on more strips of susceptor material.

[0208] The aerosol-generating device may comprise one or more susceptors. The aerosolgenerating device may comprise one or more susceptors as described above with respect to the first aspect of the disclosure. For example, the one or more susceptors may be configured to be inserted into the aerosol-generating substrate when the aerosol-generating article is received in the chamber.

[0209] In operation, the one or more susceptors may be heated by the inductor element. The aerosol-generating substrate may comprise tobacco material.

[0210] As described above with respect to the first aspect, an airflow channel may be defined between the aerosol-generating article and the jacket, the airflow channel extending from a distal end of the jacket to a proximal end of the jacket. The airflow channel may be defined between the aerosol-generating article and the at least one groove. An airflow pathway may be defined from the distal end of the jacket, through the airflow channel to the proximal end of the jacket, and from a proximal end of the aerosol-generating article, through the aerosolgenerating article to a distal end of the aerosol-generating article.

[0211] As used herein, the term “aerosol-generating article” refers to an article comprising an aerosol-forming substrate that is capable of releasing volatile compounds that can form an aerosol. An aerosol-generating article may be disposable.

[0212] According to the present disclosure, there is also provided a method of controlling an aerosol-generating system to generate an aerosol. The aerosol-generating system may comprise any aerosol-generating system according to the present disclosure. For example, the aerosol-generating system may comprise an aerosol-generating article comprising an aerosol-generating substrate. The aerosol-generating system may comprise an aerosolgenerating device. The aerosol-generating device may be according to any previous aspect to the present disclosure. For example, the aerosol-generating device may comprise a chamber for receiving at least a portion of an aerosol-generating article. The aerosolgenerating device may further comprise an inductor element disposed adjacent to the chamber or in the chamber. The aerosol-generating device may further comprise a resistive heating element disposed adjacent to the chamber or in the chamber. The aerosolgenerating device may further comprise at least one power supply for providing electrical power to the inductor element and resistive heating element. The aerosol-generating device may further comprise control circuitry configured to control the supply of power from the at least one power supply to the inductor element and the resistive heating element. The method may comprise the step of: providing a first current to the inductor element, such that the inductor element generates an alternating magnetic field within the chamber. The method may comprise the step of: providing a second current to the resistive heating element to resistively heat the resistive heating element.

[0213] According to a fifth aspect of the disclosure, there is provided a method of controlling an aerosol-generating system to generate an aerosol, the system comprising: an aerosol-generating article comprising an aerosol-generating substrate, and an aerosol-generating device, the aerosol-generating device comprising a chamber for receiving at least a portion of an aerosol-generating article; the aerosol-generating device further comprising: an inductor element disposed adjacent to the chamber or in the chamber; a resistive heating element disposed adjacent to the chamber or in the chamber; at least one power supply for providing electrical power to the inductor element and resistive heating element; and control circuitry configured to control the supply of power from the at least one power supply to the inductor element and the resistive heating element, wherein the method comprises the steps of: providing a first current to the inductor element, such that the inductor element generates an alternating magnetic field within the chamber, and providing a second current to the resistive heating element to resistively heat the resistive heating element.

[0214] Providing the first current to the inductor element, such that the inductor element generates the alternating magnetic field within the chamber, may comprise heating the one or more susceptors by the inductor element. Advantageously, the aerosol-forming substrate within the aerosol-generating article may therefore be efficiently heated both externally and internally.

[0215] The method may further comprise adjusting the first current provided to the inductor element to adjust an amount of heating provided by inductive heating. The method may further comprise adjusting the second current provided to the resistive heating element to adjust an amount of heating provided by resistive heating. Advantageously, the method may therefore avoid overheating or underheating of any part of the aerosol-forming substrate, resulting in more efficient aerosol generation without burning of the aerosol-forming substrate.

[0216] The first current may be an alternating current. The alternating current may have a first frequency. The method may further comprise not providing the inductor element with the second current. The method may further comprise not providing the inductor element a direct current. The method may further comprise solely supplying the inductor element with the first current. Advantageously, this may provide minimal resistive heating of the inductor element, which may reduce the risk of a peripheral portion of an aerosol-forming substrate being overheated or burnt.

[0217] The aerosol-forming article may comprise the one or more susceptors. The one or more susceptors may be in the form of at least one strip or at least one rod or at least one particle. Advantageously, the construction of the aerosol-generating device may be simplified, as it is not required that the aerosol-generating device comprise a susceptor element. The one or more susceptors may be in the form of elongated particles. The elongated particles may be aligned with a longitudinal direction of the aerosol-generating article. The elongated particles may be aligned with a longitudinal direction of the aerosolforming substrate. The one or more susceptors may be in the form of one or more strips of susceptor material. The aerosol-generating article may comprise one or more strips of aerosol-forming substrate laminated with one on more strips of susceptor material. For example, the aerosol-generating article may comprise one or more strips of tobacco material laminated with one on more strips of susceptor material.

[0218] The aerosol-generating device may comprise the one or more susceptors. The one or more susceptors may be in the form of at least one blade or at least one pin. Advantageously, the one or more susceptors may be reused with multiple aerosol-forming articles. The one or more susceptors may be configured to be inserted into the aerosolgenerating substrate when the aerosol-generating article is received in the chamber. Advantageously, this may allow for a simpler and more sustainable form of aerosol-forming article to be used.

[0219] The second current may be a direct current. The method may further comprise not providing the resistive heating element with the first current. The method may further comprise not providing the resistive heating element an alternating current. The method may further comprise solely supplying the resistive heating element with the second current. Advantageously, this may mean that the resistive heating element has no magnetic interaction with the inductor element.

[0220] The power supply may comprise a first DC power source. Advantageously, a range of suitable DC power sources may be suitable for use in the aerosol-generating device. The first DC power source may be a battery. The control circuitry may comprise a DC / AC converter connected to the first DC power source. The method may further comprise to supplying both the resistive heating element and the inductor element with power from the first DC power source. Advantageously, a single DC power source may therefore be used to supply both the resistive heating element and the inductor element with power.

[0221] The DC / AC converter may include a Class-E power amplifier including a first transistor switch and an LC load network. The method may further comprise providing the second current to the resistive heating element such that the resistive heating element is heated to at least 80°C. Advantageously, heating the resistive heating element is heated to at least 80°C may ensure that the resistive heating element adequately heats the aerosol-forming substrate such that vapour may be produced. The method may further comprise providing the second current to the resistive heating element such that the resistive heating element is heated to no more than 210°C. Advantageously, heating the resistive heating element to no more than 210°C may ensure that the resistive heating element does not burn or scorch the aerosol-forming substrate, as this may otherwise produce undesirable compounds, creating an aerosol with a burnt taste for the user.

[0222] The method may further comprise providing the first current to the inductor element and the second current to the resistive heating element at different times.

[0223] The method may further comprise providing the first current to the inductor element and then subsequently the second current to the resistive heating element. The method may further comprise providing the first current to the inductor element for a first time period. The method may further comprise providing the second current to the resistive heating element for a second time period after the first time period. Advantageously, the aerosol-forming substrate may be non-uniform, and heating the aerosol-forming substrate via inductive heating then subsequently by resistive heating may heat different portions of the aerosolforming substrate at different times. As the aerosol-forming substrate may be non-uniform, this may result in aerosol with aerosol characteristics being produced at different times.

[0224] The method may further comprise providing the second current to the resistive heating element and then subsequently the first current to the inductor element. The method may further comprise providing the second current to the resistive heating element for a first time period. The method may further comprise providing the first current to the inductor element for a second time period after the first time period. Advantageously, the aerosolforming substrate may be non-uniform, and heating the aerosol-forming substrate via resistive heating then subsequently by inductive heating may heat different portions of the aerosol-forming substrate at different times. As the aerosol-forming substrate may be non- uniform, this may result in aerosol with aerosol characteristics being produced at different times.

[0225] The method may further comprise detecting when the user takes a puff on the system. For example, the control circuitry may be coupled to a pressure sensor, the pressure sensor configured to detect a pressure drop when the user takes a puff on the system. The method may further comprise supplying power to the inductor element or the resistive heating element, or the inductor element and the resistive heating element, when the pressure sensor detects a pressure drop when the user takes a puff on the system. For example, the method may further comprise starting the first time period in response to the user taking a puff on the system.

[0226] The control circuitry may comprise a user-activatable trigger. For example, the user- activatable trigger may comprise a button or a switch. The method may further comprise starting the first time period in response to the user-activatable trigger being activated.

[0227] The method may further comprise ending the first time period and starting the second time period in response to: a predetermined number of puffs on the system being taken; or a predetermined time from a first puff on the system passing; or the user-activatable trigger being activated; or a combination of any one or more of the above.

[0228] The method may further comprise providing the first current to the inductor element and the second current to the resistive heating element in an alternating sequence. Advantageously, it may be beneficial to alternate inductive and resistive heating in order to avoid overheating of any part of the aerosol-forming substrate.

[0229] The method may further comprise the control circuitry receiving an inductor feedback signal from the inductor element and a resistive heating feedback signal from the resistive heating element. For example, the method may further comprise the microcontroller receiving an inductor feedback signal from the inductor element and a resistive heating feedback signal from the resistive heating element. The inductor feedback signal may comprise at least one of a voltage, a current or a conductance. For example, the inductor feedback signal may comprise a voltage and a current. The resistive heating feedback signal may comprise at least one of a voltage, a current or a conductance. For example, the resistive heating feedback signal may comprise a voltage and a current.

[0230] The method may further comprise the control circuitry providing the first current to the inductor element based on the inductor feedback signal. The method may further comprise the control circuitry providing the second current to the resistive heating element based on the resistive heating feedback signal. The inductor feedback signal may be dependent on a temperature of the susceptor. The resistive heating feedback signal may be dependent on a temperature of the resistive heating element.

[0231] The method may further comprise adjusting the first current provided to the inductor element dependent on the inductor feedback signal. The method may further comprise determining a temperature of the inductor element dependent on the inductor feedback signal. The method may further comprise adjusting the first current provided to the inductor element dependent on the inductor feedback signal to maintain the temperature of the susceptor element at a susceptor target temperature or to follow a susceptor target temperature profile. The method may further comprise adjusting the second current provided to the resistive heating element dependent on the resistive heating feedback signal. The method may further comprise determining a temperature of the resistive heating element dependent on the resistive heating feedback signal. The method may further comprise the adjusting the second current provided to the resistive heating element dependent on the resistive heating feedback signal to maintain the temperature of the resistive heating element at a resistive heating target temperature or to follow a resistive heating target temperature profile.

[0232] When an alternating magnetic field is generated by supplying an alternating current in the inductor coil, the alternating magnetic field may induce an induced alternating current in the resistive heating element. Therefore, when the first current is supplied to the inductor element at the same time as the second current is supplied to the resistive heating element, the induced alternating current in the resistive heating element may affect the resistive heating feedback signal provided to the control circuitry. For example, the induced alternating current in the resistive heating element may modify the resistive heating feedback signal provided to the control circuitry. This may affect the ability of the method to accurately determine the temperature of the resistive heating element, and therefore affect the ability of the method to maintain the temperature of the resistive heating element at the resistive heating target temperature or to follow the resistive heating target temperature profile.

[0233] Therefore, the method may further comprise preventing the supply of the second current to the resistive heating element when the first current is supplied to the inductor element. For example, the method may further comprise preventing the supply of the direct current to the resistive heating element when the alternating current is supplied to the inductor element. Advantageously, when the method further comprises preventing the supply of the second current to the resistive heating element when the first current is supplied to the inductor element, the induced alternating current does not affect the resistive heating feedback signal. Therefore the method can more accurately determine the temperature of the resistive heating element.

[0234] Similarly, the method may further comprise preventing the supply of the first current to the inductor element when the second current is supplied to the resistive heating element. The method may further comprise preventing simultaneous supply of the first current to the inductor element and the second current to the resistive heating element.

[0235] The method may further comprise providing the first current to the inductor element during on periods, and preventing the first current from being provided to the inductor element during off periods. The method may further comprise alternating the on periods with the off periods.

[0236] Specifically, the method may further comprise supplying a switching voltage to the DC / AC converter in order to control the first current provided to the inductor element. In particular, the method may further comprise supplying the switching voltage to a Field Effect Transistor of the DC / AC converter in order to control the first current provided to the inductor element. The switching voltage may have a rectangular profile. The switching voltage may comprise alternating on periods wherein the first current is provided to the inductor element, and off periods where the first current is prevented from being provided to the inductor element.

[0237] The method may further comprise controlling the temperature of the susceptor element by adjusting the length of the on periods. For example, the method may further comprise adjusting the length of the on periods to maintain the temperature of the susceptor element at a susceptor target temperature or to follow a susceptor target temperature profile. For example, by using pulse-width modulation.

[0238] The method may further comprise providing the first current to the inductor element in one or more pulses during each of the on periods. The pulses may comprise a plurality of separate pulses. The method may further comprise preventing the supply of the first current to the inductor element when not during the pulses.

[0239] The method may further comprise adjusting the pulses during each of the on periods to control the temperature of the susceptor element. For example, the method may further comprise using pulse-width modulation to control the temperature of the susceptor element. The method may further comprise adjusting one or more of a duration of each of the pulses, a number of each of the pulses, or a time gap between adjacent pulses during each of the on periods to control the temperature of the susceptor element. For example, the method may further comprise adjusting the pulses during each of the on periods to maintain the temperature of the susceptor element at the susceptor target temperature or to follow the susceptor target temperature profile.

[0240] The pulses may occupy a proportion of each of the on periods. For example, the pulses may occupy 100% of each on period such that the first current is supplied to the inductor element during each on period for the entirety of each on period. As another example, the pulses may occupy 50% of each on period such that the first current is supplied to the inductor element during each on period for half the duration of each on period. The method may further comprise adjusting the proportion of each of the on periods occupied by the pulses to control the temperature of the susceptor element. For example, the method may further comprise adjusting the proportion of each of the on periods occupied by the pulses to maintain the temperature of the susceptor element at the susceptor target temperature or to follow the susceptor target temperature profile.

[0241] The on periods may be between 500 milliseconds and 1 millisecond in length. Preferably, the on periods are between 100 milliseconds and 5 milliseconds in length. Preferably still, the on periods are between 50 milliseconds and 10 milliseconds in length. Even more preferably, the on periods are about 20 milliseconds in length.

[0242] The off periods may be between 500 milliseconds and 1 millisecond in length. Preferably, the off periods are between 200 milliseconds and 10 milliseconds in length. Preferably still, the off periods are between 100 milliseconds and 50 milliseconds in length. Even more preferably, the off periods are about 70 milliseconds in length.

[0243] The method may further comprise providing the second current to the resistive heating element during the off periods. In particular, the method may further comprise providing the second current to the resistive heating element only during the off periods.

[0244] The method may further comprise controlling the temperature of the resistive heating element by adjusting the length of the off periods. For example, the method may further comprise adjusting the length of the off periods to maintain the temperature of the resistive heating element at a resistive heating target temperature or to follow a resistive heating target temperature profile. For example, by using pulse-width modulation.

[0245] The method may further comprise providing the second current to the resistive heating element in one or more pulses during each of the off periods. The pulses may comprise a plurality of separate pulses. The method may further comprise preventing the supply of the second current to the resistive heating element when not during the pulses.

[0246] The method may further comprise adjusting the pulses during each of the off periods to control the temperature of the resistive heating element. For example, the method may further comprise using pulse-width modulation to control the temperature of the resistive heating element. The method may further comprise adjusting one or more of a duration of each of the pulses, a number of each of the pulses, or a time gap between adjacent pulses during each of the off periods to control the temperature of the resistive heating element. For example, the method may further comprise adjusting the pulses during each of the off periods to maintain the temperature of the resistive heating element at the resistive heating target temperature or to follow the resistive heating target temperature profile.

[0247] The pulses may occupy a proportion of each of the off periods. For example, the pulses may occupy 100% of each off period such that the second current is supplied to the resistive heating element during each off period for the entirety of each off period. As another example, the pulses may occupy 50% of each off period such that the second current is supplied to the resistive heating element during each off period for half the duration of each off period. The method may further comprise adjusting the proportion of each of the off periods occupied by the pulses to control the temperature of the resistive heating element. For example, the method may further comprise adjusting the proportion of each of the off periods occupied by the pulses to maintain the temperature of the resistive heating element at the resistive heating target temperature or to follow the resistive heating target temperature profile.

[0248] The method may further comprise providing the second current to the resistive heating element for reduced time periods. The reduced time period may be shorter than the off periods. Advantageously, by providing the second current to the resistive heating element during the off periods but for reduced time periods shorter than the off periods, the control circuitry may avoid any overlap between the first current being provided to the inductor element and the second current being provided to the resistive heating element. As the alternating current induced in the resistive heating element may not instantaneously drop to zero when the first current applied to the inductor element is stopped, including time gaps between the reduced time periods and the periods when the first current is provided to the inductor element may advantageously reduce noise in the resistive heating feedback signal resulting from any alternating current induced in the resistive heating element. Also advantageously, the method may further comprise controlling the temperature of the resistive heating element by adjusting the length of the reduced time periods. For example, the method may further comprise adjusting the length of the reduced time periods to maintain the temperature of the resistive heating element at the resistive heating target temperature or to follow the resistive heating target temperature profile. The method may further comprise controlling the temperature of the resistive heating element by adjusting the length of time gaps between the reduced time periods and the on periods. For example, the method may further comprise adjusting the length of time gaps between the reduced time periods and the on periods to maintain the temperature of the resistive heating element at the resistive heating target temperature or to follow the resistive heating target temperature profile. This allows the control circuitry to maintain the temperature of the resistive heating element at the resistive heating target temperature, or to follow the resistive heating target temperature profile, using pulse-width modulation.

[0249] The method may further comprise performing a calibration process prior to alternating the on periods with the off periods. The method may further comprise performing the calibration process immediately after the aerosol-generating device is switched on. The calibration process may comprise supplying the first current to the inductor element to determine at least one calibration variable of the susceptor element, such as a conductance value or a resistance value. In particular, the method may further comprise performing the calibration process prior to supplying the second current to the resistive heating element.

[0250] The method may further comprise providing the first current to the inductor element and the second current to the resistive heating element simultaneously. Advantageously, this mode of operation may supply maximal power to the aerosol-forming substrate to quickly heat the aerosol-forming substrate. This may be particularly beneficial after start-up of the aerosol-generating system or use of the aerosol-generating system in a cold environment, for example.

[0251] The method may further comprise, following activation of the device, initially providing the first current to the inductor element, and subsequently providing the second current to the resistive heating element. Advantageously, the aerosol-forming substrate may be non- uniform, and heating the aerosol-forming substrate via inductive heating then subsequently by resistive heating may heat different portions of the aerosol-forming substrate at different times. As the aerosol-forming substrate may be non-uniform, this may result in aerosol with aerosol characteristics being produced at different times.

[0252] The method may further comprise adjusting a frequency of the first current during operation of the device to adjust the amount of heat provided by inductive heating.

[0253] The method may further comprise adjusting the first current provided to the inductor element to maintain the temperature of the susceptor at a target temperature or to follow a target temperature profile. For example, the method may further comprise adjusting an amplitude of the first current provided to the inductor element to maintain the temperature of the susceptor element at the susceptor target temperature or to follow the susceptor target temperature profile.

[0254] The method may further comprise adjusting the second current provided to the resistive heating element to maintain the temperature of the resistive heating element at a target temperature or to follow a target temperature profile. For example, the method may further comprise adjusting an amplitude of the second current provided to the resistive heating element to maintain the temperature of the resistive heating element at the resistive heating target temperature or to follow the resistive heating target temperature profile.

[0255] Advantageously, the temperature profiles of the resistive heating element and the inductor element may be independently controlled.

[0256] According to a sixth aspect of the disclosure, there is provided an aerosol-generating device comprising: a chamber for receiving at least a portion of an aerosol-generating article; an internal heater; an external heater; at least one power supply for providing electrical power to the internal heater and the external heater; and control circuitry configured to control the supply of power from the at least one power supply to the internal heater and the external heater, wherein the control circuitry is further configured to prevent the supply of power to one of the external heater or the internal heater when power is supplied to the other of the external heater or the internal heater. Advantageously, by preventing the supply of power to one of the external heater or the internal heater when power is supplied to the other, the aerosol-generating device may utilise energy stored in the at least one power supply in a more efficient manner, which may allow for a longer aerosol-generating experience for a user. It has been found that simultaneous supply from a power supply to two separate internal and external heaters is detrimental to the efficiency of the at least one power supply.

[0257] The control circuitry may be configured to prevent the supply of power to the external heater when power is supplied to the internal heater. The control circuitry may be configured to control the supply of power to the external heater dependent on a power supply profile supplied to the internal heater. For example, the control circuitry may be configured to prevent the supply of power to the external heater when power is supplied to the internal heater, and not prevent the supply of power to the external heater when power is not supplied to the internal heater. In other words, the control circuitry may be configured to allow the supply of power to the external heater when power is not supplied to the internal heater.

[0258] The control circuitry may be configured to prevent the supply of power to the internal heater when power is supplied to the external heater. The control circuitry may be configured to control the supply of power to the internal heater dependent on a power supply profile supplied to the external heater. For example, the control circuitry may be configured to prevent the supply of power to the internal heater when power is supplied to the external heater, and not prevent the supply of power to the internal heater when power is not supplied to the external heater. In other words, the control circuitry may be configured to allow the supply of power to the internal heater when power is not supplied to the external heater.

[0259] The internal heater may be configured to generate heat from an internal location within the chamber. The internal heater may be configured to heat the aerosol-generating article from an internal location within the aerosol-generating article when at least a portion of the aerosol-generating article is received within the chamber. In particular, the internal heater may be configured to heat the aerosol-generating article from an internal location within the aerosol-forming substrate when at least a portion of the aerosol-generating article is received within the chamber.

[0260] The external heater may be configured to generate heat from an external location outside of the chamber. The external heater may be configured to heat the aerosolgenerating article from an external location outside of the aerosol-generating article when at least a portion of the aerosol-generating article is received within the chamber. In particular, the external heater may be configured to heat the aerosol-generating article from an external location outside of the aerosol-generating substrate when at least a portion of the aerosolgenerating article is received within the chamber.

[0261] The control circuitry may be configured to provide a first current to the internal heater. The control circuitry may be configured to provide a second current to the external heater.

[0262] The power supply may comprise a first DC power source. Advantageously, a range of suitable DC power sources may be suitable for use in the aerosol-generating device. The first DC power source may be a battery. The control circuitry may comprise a DC / AC converter connected to the first DC power source. Advantageously, a single DC power source may therefore be used to supply both the external heater and the internal heater with power.

[0263] The DC / AC converter may include a Class-E power amplifier including a first transistor switch and an LC load network.

[0264] The control circuitry may be configured to provide the first current to the internal heater and the second current to the external heater at different times.

[0265] For example, the control circuitry may be configured to provide the first current to the internal heater and then subsequently the second current to the external heater. The control circuitry may be configured to provide the first current to the internal heater for a first time period. The control circuitry may be configured to provide the second current to the external heater for a second time period after the first time period. Advantageously, the aerosolforming substrate may be non-uniform, and heating the aerosol-forming substrate internally then subsequently externally may heat different portions of the aerosol-forming substrate at different times. As the aerosol-forming substrate may be non-uniform, this may result in aerosol with aerosol characteristics being produced at different times.

[0266] The control circuitry may be configured to provide the second current to the external heater and then subsequently the first current to the internal heater. The control circuitry may be configured to provide the second current to the external heater for a first time period. The control circuitry may be configured to provide the first current to the internal heater for a second time period after the first time period. Advantageously, the aerosol-forming substrate may be non-uniform, and heating the aerosol-forming substrate via resistive heating then subsequently by inductive heating may heat different portions of the aerosol-forming substrate at different times. As the aerosol-forming substrate may be non-uniform, this may result in aerosol with aerosol characteristics being produced at different times.

[0267] The control circuitry may be configured to detect when the user takes a puff on the system. For example, the control circuitry may be coupled to a pressure sensor, the pressure sensor configured to detect a pressure drop when the user takes a puff on the system. The control circuitry may be configured to supply power to the internal heater or the external heater, or the internal heater and the external heater, when the pressure sensor detects a pressure drop when the user takes a puff on the system. For example, the control circuitry may be configured to start the first time period in response to the user taking a puff on the system.

[0268] The control circuitry may comprise a user-activatable trigger. For example, the user- activatable trigger may comprise a button or a switch. The control circuitry may be configured to start the first time period in response to the user-activatable trigger being activated.

[0269] The control circuitry may be configured to end the first time period and start the second time period in response to: a predetermined number of puffs on the system being taken; or a predetermined time from a first puff on the system passing; or the user-activatable trigger being activated; or a combination of any one or more of the above.

[0270] The control circuitry may be configured to provide the first current to the internal heater and the second current to the external heater in an alternating sequence. Advantageously, it may be beneficial to alternate internal and external heating in order to avoid overheating of any part of the aerosol-forming substrate.

[0271] The control circuitry may comprise a microcontroller. The control circuitry may be configured to receive an internal heating feedback signal from the internal heater and an external heating feedback signal from the external heater. For example, the microcontroller may be configured to receive an internal heating feedback signal from the internal heater and an external heating feedback signal from the external heater.

[0272] The internal heating feedback signal may comprise at least one of a voltage, a current or a conductance. For example, the internal heating feedback signal may comprise a voltage and a current. The external heating feedback signal may comprise at least one of a voltage, a current or a conductance. For example, the external heating feedback signal may comprise a voltage and a current.

[0273] The control circuitry may be configured to provide the first current to the internal heater based on the internal heating feedback signal. The control circuitry may be configured to provide the second current to the external heater based on the external heating feedback signal. The internal heating feedback signal may be dependent on a temperature of a component of the internal heater. The external heating feedback signal may be dependent on a temperature of a component of the external heater.

[0274] The control circuitry may be configured to adjust the first current provided to the internal heater dependent on the internal heating feedback signal. The control circuitry may be configured to determine a temperature of the component of the internal heater dependent on the internal heating feedback signal. The control circuitry may be configured to adjust the first current provided to the internal heater dependent on the internal heating feedback signal to maintain the temperature of the component of the internal heater at an internal heater target temperature or to follow an internal heater target temperature profile.

[0275] The control circuitry may be configured to adjust the second current provided to the external heater dependent on the external heating feedback signal. The control circuitry may be configured to determine a temperature of the external heater dependent on the external heating feedback signal. The control circuitry may be configured to adjust the second current provided to the external heater dependent on the external heating feedback signal to maintain the temperature of the component of the external heater at an external heater target temperature or to follow an external heater target temperature profile.

[0276] The control circuitry may be configured to provide the first current to the internal heater during on periods, and prevent the first current from being provided to the internal heater during off periods. The control circuitry may be configured to provide the second current to the external heater during off periods, and prevent the second current from being provided to the external heater during on periods. The control circuitry may be configured to alternate the on periods with the off periods.

[0277] The microcontroller may be configured to supply a switching voltage to a control circuitry component in order to control the first current provided to the internal heater. Specifically, in embodiments as described below in which the internal heater comprises an inductor element, the microcontroller may be configured to supply a switching voltage to the DC / AC converter in order to control the first current provided to the internal heater. In particular, the microcontroller may be configured to supply the switching voltage to a Field Effect Transistor of the DC / AC converter in order to control the first current provided to the internal heater.

[0278] The microcontroller may be configured to supply a switching voltage to a control circuitry component in order to control the second current provided to the external heater. Specifically, in embodiments as described below in which the external heater comprises an inductor element, the microcontroller may be configured to supply a switching voltage to the DC / AC converter in order to control the second current provided to the external heater. In particular, the microcontroller may be configured to supply the switching voltage to a Field Effect Transistor of the DC / AC converter in order to control the second current provided to the external heater.

[0279] The switching voltage may have a rectangular profile.

[0280] The switching voltage may comprise alternating on periods wherein the first current is provided to the internal heater, and off periods where the first current is prevented from being provided to the internal heater. The control circuitry may be configured to prevent the supply of the second current to the external heater during the on periods. The switching voltage may comprise alternating off periods wherein the second current is provided to the external heater, and on periods where the second current is prevented from being provided to the external heater. The control circuitry may be configured to prevent the supply of the first current to the internal heater during the on periods.

[0281] The temperature of the component of the internal heater may be controlled by adjusting the length of the on periods. For example, the control circuitry may be configured to adjust the length of the on periods to maintain the temperature of the component of the internal heater at the internal heater target temperature or to follow the internal heater target temperature profile.

[0282] The control circuitry may be configured to provide the first current to the internal heater in one or more pulses during each of the on periods. The pulses may comprise a plurality of separate pulses. The control circuitry may be configured to prevent the supply of the first current to the internal heater when not during the pulses.

[0283] The control circuitry may be configured to adjust the pulses during each of the on periods to control the temperature of the component of the internal heater. For example, the control circuitry may be configured to use pulse-width modulation to control the temperature of the component of the internal heater. The control circuitry may be configured to adjust one or more of a duration of each of the pulses, a number of each of the pulses, or a time gap between adjacent pulses during each of the on periods to control the temperature of the component of the internal heater. For example, the control circuitry may be configured to adjust the pulses during each of the on periods to maintain the temperature of the component of the internal heater at the internal heater target temperature or to follow the internal heater target temperature profile.

[0284] The pulses may occupy a proportion of each of the on periods. For example, the pulses may occupy 100% of each on period such that the first current is supplied to the internal heater during each on period for the entirety of each on period. As another example, the pulses may occupy 50% of each on period such that the first current is supplied to the internal heater during each on period for half the duration of each on period. The control circuitry may be configured to adjust the proportion of each of the on periods occupied by the pulses to control the temperature of the component of the internal heater. For example, the control circuitry may be configured to adjust the proportion of each of the on periods occupied by the pulses to maintain the temperature of the component of the internal heater at the internal heater target temperature or to follow the internal heater target temperature profile.

[0285] The on periods may be between 3000 milliseconds and 1 millisecond in length. The on periods may be between 500 milliseconds and 1 millisecond in length. Preferably, the on periods are between 100 milliseconds and 5 milliseconds in length. Preferably still, the on periods are between 50 milliseconds and 10 milliseconds in length. Even more preferably, the on periods are about 20 milliseconds in length.

[0286] The off periods may be between 3000 milliseconds and 1 millisecond in length. The off periods may be between 500 milliseconds and 1 millisecond in length. Preferably, the off periods are between 200 milliseconds and 10 milliseconds in length. Preferably still, the off periods are between 100 milliseconds and 50 milliseconds in length. Even more preferably, the off periods are about 70 milliseconds in length.

[0287] The control circuitry may be configured to provide the second current to the external heater during the off periods. In particular, the control circuitry may be configured to provide the second current to the external heater only during the off periods.

[0288] The temperature of the component of the external heater may be controlled by adjusting the length of the off periods. For example, the control circuitry may be configured to adjust the length of the off periods to maintain the temperature of the component of the external heater at the external heater target temperature or to follow the external heater target temperature profile.

[0289] The control circuitry may be configured to provide the second current to the external heater in one or more pulses during each of the off periods. The pulses may comprise a plurality of separate pulses. The control circuitry may be configured to prevent the supply of the second current to the external heater when not during the pulses.

[0290] The control circuitry may be configured to adjust the pulses during each of the off periods to control the temperature of the component of the external heater. For example, the control circuitry may be configured to use pulse-width modulation to control the temperature of the component of the external heater. The control circuitry may be configured to adjust one or more of a duration of each of the pulses, a number of each of the pulses, or a time gap between adjacent pulses during each of the off periods to control the temperature of the component of the external heater. For example, the control circuitry may be configured to adjust the pulses during each of the off periods to maintain the temperature of the component of the external heater at the external heater target temperature or to follow the external heater target temperature profile.

[0291] The pulses may occupy a proportion of each of the off periods. For example, the pulses may occupy 100% of each off period such that the second current is supplied to the external heater during each off period for the entirety of each off period. As another example, the pulses may occupy 50% of each off period such that the second current is supplied to the external heater during each off period for half the duration of each off period. The control circuitry may be configured to adjust the proportion of each of the off periods occupied by the pulses to control the temperature of the component of the external heater. For example, the control circuitry may be configured to adjust the proportion of each of the off periods occupied by the pulses to maintain the temperature of the component of the external heater at the external heater target temperature or to follow the external heater target temperature profile.

[0292] The control circuitry may be configured to provide the second current to the external heater for reduced time periods. Each of the reduced time periods may be shorter than each of the off periods. The control circuitry may be configured to adjust the length of the reduced time periods to control the temperature of the component of the external heater. Advantageously, by providing the second current to the external heater during the off periods but for reduced time periods shorter than the off periods, the control circuitry may avoid any overlap between the first current being provided to the internal heater and the second current being provided to the external heater.

[0293] As the first current supplied from the power supply may not instantaneously drop to zero when the first current applied to the internal heater is stopped, including time gaps between the reduced time periods and the periods when the first current is provided to the internal heater may advantageously ensure that the first current and second current are not simultaneously supplied to the internal and external heaters respectively, which may have a negative impact on the power supply, for example this may reduce the operational life of the power supply.

[0294] Also advantageously, the temperature of the component of the external heater may be controlled by adjusting the length of the reduced time periods. For example, the control circuitry may be configured to adjust the length of the reduced time periods to maintain the temperature of the component of the external heater at the external heater target temperature or to follow the external heater target temperature profile. The temperature of the component of the external heater may be controlled by adjusting the length of time gaps between the reduced time periods and the on periods. For example, the control circuitry may be configured to adjust the length of time gaps between the reduced time periods and the on periods to maintain the temperature of the component of the external heater at the external heater target temperature or to follow the external heater target temperature profile. This allows the control circuitry to maintain the temperature of the component of the external heater at the external heater target temperature, or to follow the external heater target temperature profile, using pulse-width modulation.

[0295] The controller may be configured to perform a calibration process prior to alternating the on periods with the off periods. The controller may be configured to perform the calibration process immediately after the aerosol-generating device is switched on. In particular, the controller may be configured to perform the calibration process prior to supplying the second current to the external heater.

[0296] The control circuitry may be configured to adjust the first current provided to the internal heater to maintain the temperature of the component of the internal heater at the internal heater target temperature or to follow the internal heater target temperature profile. For example, the control circuitry may be configured to adjust an amplitude of the first current provided to the internal heater to maintain the temperature of the component of the internal heater at the internal heater target temperature or to follow the internal heater target temperature profile.

[0297] The control circuitry may be configured to adjust the second current provided to the external heater to maintain the temperature of the component of the external heater at the external heater target temperature or to follow the external heater target temperature profile. For example, the control circuitry may be configured to adjust an amplitude of the second current provided to the external heater to maintain the temperature of the component of the external heater at the external heater target temperature or to follow the external heater target temperature profile.

[0298] At least a portion of the internal heater may at least partially surround the chamber. Advantageously, this may result in efficient heating of the aerosol-generating article by the internal heater. At least a portion of the internal heater may surround the chamber

[0299] The external heater may at least partially surround the chamber. Advantageously, this may result in efficient heating of a periphery of the aerosol-forming substrate by the external heater. The external heater may surround the chamber.

[0300] The inductor element and the resistive heating element may surround the same longitudinal portion of the chamber.

[0301] The external heater may be configured to heat a periphery of the chamber. Advantageously, if the internal heater is configured to heat a central portion of the aerosolforming substrate, this arrangement may ensure that no portion of the aerosol-forming substrate is overheated.

[0302] The external heater may extend from a first end of the chamber to a second end of the chamber.

[0303] The aerosol-generating device may further comprise a jacket. The jacket may at least partially define the chamber.

[0304] The external heater may be positioned on an outer surface of the jacket. The external heater may be wound around the outer surface of the jacket. Advantageously, the external heater does not contact an outer surface of the aerosol-forming article when the aerosolforming article is received in the chamber. This may protect the external heater from damage during insertion of the aerosol-forming article into the chamber, and reduce the likelihood of overheating of the aerosol-forming article when the second current is supplied to the external heater.

[0305] At least a portion of the internal heater may be positioned on the outer surface of the jacket. At least a portion of the internal heater may be wound around the outer surface of the jacket. Advantageously, the portion of the internal heater does not contact the outer surface of the aerosol-forming article when the aerosol-forming article is received in the chamber. This may protect the portion of the internal heater from damage during insertion of the aerosol-forming article into the chamber.

[0306] The jacket may be a thermally conductive jacket. The thermal conductivity of the thermally conductive jacket may be at least 20 Wm’1K’1, preferably at least 30 Wm’1K’1, preferably still at least 40 Wm’1K’1, and even more preferably approximately 80 Wm’1K’1. Advantageously, a thermally conductive jacket ensure that heat is efficiently transferred from the resistive heating element to the aerosol-forming substrate.

[0307] The jacket may comprise an electrically insulating material. The jacket may consist of an electrically insulating material. The jacket may comprise a material having a relative magnetic permeability between 0.9 and 1.1 , preferably between 0.99 and 1.01. The jacket may therefore comprise a material which is substantially transparent to the alternating magnetic field. Advantageously, the jacket may therefore not substantially affect the alternating magnetic field induced within the chamber by the inductor element.

[0308] The jacket may comprise a ceramic. The ceramic may comprise alumina. Advantageously alumina has been found to possess suitable thermal properties to ensure that heat is efficiently transferred from the resistive heating element to the aerosol-forming substrate. The ceramic may comprise aluminium nitrate. Advantageously aluminium nitrate has been found to possess suitable thermal properties to ensure that heat is efficiently transferred from the resistive heating element to the aerosol-forming substrate.

[0309] The jacket may comprise a circular cross section. The jacket may comprise a substantially cylindrical shape. Advantageously, a cylindrical aerosol-forming article may therefore be easily inserted into the chamber by the user in any of 360 degrees of orientations.

[0310] The aerosol-generating device may further comprise a housing. The housing may at least partially surround the chamber. The jacket may be received in the housing.

[0311] The portion of the internal heater may be disposed within the housing. The portion of the internal heater may be disposed within the housing such that the portion of the internal heater at least partially surrounds the jacket and the external heater. Advantageously, the jacket and the external heater may therefore be manufactured together as a external heater assembly, which may be insertable into the housing during manufacture. This may allow for a degree of modularity during manufacture, in that different external heater assemblies may be inserted into different housing comprising different portions of the internal heater. Furthermore, the external heater assembly may be replaceable from the housing comprising the portion of the internal heater. The jacket may comprise a longitudinal axis. The jacket may comprise an inner surface. The inner surface may define the chamber. The jacket may comprise at least one groove defined on an inner surface of the jacket. The at least one groove may extend parallel to the longitudinal axis.

[0312] An airflow channel may be defined between the aerosol-generating article and the jacket when the aerosol-generating article is received in the chamber. The airflow channel may extend from a distal end of the jacket to a proximal end of the jacket.

[0313] The airflow channel may be defined between the aerosol-generating article and the at least one groove.

[0314] An airflow pathway may be defined from the distal end of the jacket, through the airflow channel to the proximal end of the jacket, and from a proximal end of the aerosolgenerating article, through the aerosol-generating article to a distal end of the aerosolgenerating article when the aerosol-generating article is received in the chamber. Advantageously, this may provide a straightforward airflow pathway solution which does not require airflow inlets defined through the housing.

[0315] The external heater may be wound around a winding axis coincident with the longitudinal axis of the jacket. The portion of the internal heater may be wound around the winding axis coincident with the longitudinal axis of the jacket.

[0316] In an embodiment of the sixth aspect, the internal heater may comprise an inductor element and the external heater may comprise a resistive heating element. The inductor element may be disposed adjacent to the chamber. The inductor element may be configured to generate an alternating magnetic field within the chamber when supplied with an alternating current. The resistive heating element may be disposed adjacent to the chamber. The resistive heating element may be configured to be resistively heated when supplied with a direct current.

[0317] The first current may be an alternating current. The alternating current may have a first frequency. The control circuitry may be configured so that the inductor element is not supplied with the second current. The control circuitry may be configured so that the inductor element is not supplied with a direct current. The control circuitry may be configured so that the inductor element is solely supplied with the first current. Advantageously, this may provide minimal resistive heating of the inductor element, which may reduce the risk of a peripheral portion of an aerosol-forming substrate being overheated or burnt.

[0318] When supplied with the first current, the inductor element may generate an alternating magnetic field within the chamber to inductively heat one or more susceptors within an aerosol-generating article when the aerosol-generating article is received within the chamber. Advantageously, the aerosol-forming substrate within the aerosol-generating article may therefore be efficiently heated both externally and internally. The aerosol-forming article may comprise the one or more susceptors. The one or more susceptors may be in the form of at least one strip or at least one rod or at least one particle. Advantageously, the construction of the aerosol-generating device may be simplified, as it is not required that the aerosol-generating device comprise a susceptor element. The one or more susceptors may be in the form of elongated particles. The elongated particles may be aligned with a longitudinal direction of the aerosol-generating article. The elongated particles may be aligned with a longitudinal direction of the aerosolforming substrate. The one or more susceptors may be in the form of one or more strips of susceptor material. The aerosol-generating article may comprise one or more strips of aerosol-forming substrate laminated with one on more strips of susceptor material. For example, the aerosol-generating article may comprise one or more strips of tobacco material laminated with one on more strips of susceptor material.

[0319] The aerosol-generating device may comprise the one or more susceptors. The one or more susceptors may be in the form of at least one blade or at least one pin. Advantageously, the one or more susceptors may be reused with multiple aerosol-forming articles. The one or more susceptors may be configured to be inserted into the aerosolgenerating substrate when the aerosol-generating article is received in the chamber. Advantageously, this may allow for a simpler and more sustainable form of aerosol-forming article to be used.

[0320] The second current may be a direct current. The control circuitry may be configured so that the resistive heating element is not supplied with the first current. The control circuitry may be configured so that the resistive heating element is not supplied with an alternating current. The control circuitry may be configured so that the resistive heating element is solely supplied with the second current. Advantageously, this may mean that the resistive heating element has no magnetic interaction with the inductor element.

[0321] The control circuitry may be configured to provide the second current to the resistive heating element such that the resistive heating element is heated to at least 80°C. Advantageously, heating the resistive heating element to at least 80°C may ensure that the resistive heating element adequately heats the aerosol-forming substrate such that vapour may be produced. The control circuitry may be configured to provide the second current to the resistive heating element such that the resistive heating element is heated to no more than 210°C. Advantageously, heating the resistive heating element to no more than 210°C may ensure that the resistive heating element does not burn or scorch the aerosol-forming substrate, as this may otherwise produce undesirable compounds, creating an aerosol with a burnt taste for the user.

[0322] When an alternating magnetic field is generated by supplying an alternating current in the inductor element, the alternating magnetic field may induce an induced alternating current in the resistive heating element. Therefore, when the first current is supplied to the inductor element at the same time as the second current is supplied to the resistive heating element, the induced alternating current in the resistive heating element may affect the resistive heating feedback signal provided to the control circuitry. For example, the induced alternating current in the resistive heating element may modify the resistive heating feedback signal provided to the control circuitry. This may affect the ability of the control circuitry to accurately determine the temperature of the resistive heating element, and therefore affect the ability of the control circuitry to maintain the temperature of the resistive heating element at the external heater target temperature or to follow the external heater target temperature profile.

[0323] Advantageously, when the control circuitry is configured to prevent the supply of the second current to the resistive heating element when the first current is supplied to the inductor element, the induced alternating current does not affect the resistive heating feedback signal. Therefore the control circuitry can more accurately determine the temperature of the resistive heating element.

[0324] Similarly, the control circuitry may be configured to prevent the supply of the first current to the inductor element when the second current is supplied to the resistive heating element. The control circuitry may be configured to prevent simultaneous supply of the first current to the inductor element and the second current to the resistive heating element.

[0325] When an alternating magnetic field is generated in the chamber by an alternating current in the inductor coil, depending on the configuration of the adjacent resistive heating element, the alternating magnetic field may induce an alternating current in an adjacent resistive heating element. The resistive heating element may be configured such that a total current induced in the resistive heating element by the alternating magnetic field is substantially zero.

[0326] The resistive heating element may comprise at least one primary portion. The resistive heating element may comprise at least one secondary portion. The resistive heating element may be configured such that a current induced in the at least one primary portion by the alternating magnetic field is approximately equal and opposite in direction to a current induced in the at least one secondary portion by the alternating magnetic field.

[0327] The resistive heating element may form an electrical pathway from a positive terminal of the control circuitry to a negative terminal of the control circuitry. The at least one primary portion may extend along the electrical pathway towards the negative terminal of the control circuitry in a clockwise direction about the chamber when viewed from the first end of the chamber.

[0328] The second current may be considered to flow from the positive terminal of the control circuitry to a negative terminal of the control circuitry. The at least one primary portion may be arranged such that the second current flows in the at least one primary portion in a clockwise direction about the chamber when viewed from the first end of the chamber.

[0329] The at least one secondary portion may extend along the electrical pathway towards the negative terminal of the control circuitry in an opposite direction to the at least one primary portion when viewed from the first end of the chamber. For example, the at least one secondary portion may extend along the electrical pathway towards the negative terminal of the control circuitry in an anti-clockwise direction when viewed from the first end of the chamber.

[0330] The at least one secondary portion may be arranged such that the second current flows in the at least one secondary portion in an opposite direction to the second current in the at least one primary portion when viewed from the first end of the chamber. For example, the at least one secondary portion may be arranged such that the second current flows in the at least one secondary portion in an anti-clockwise direction about the chamber when viewed from the first end of the chamber.

[0331] A cumulative length of the at least one primary portion may be substantially equal to a cumulative length of the at least one secondary portion.

[0332] An alternating current induced in a resistive heating element may be particularly disadvantageous as the control circuitry would require filters to ensure the induced alternating current in the resistive heating element does not cause damage to any electronic components electrically connected to the resistive heating element. Advantageously, in the above arrangement, the resistive heating element is arranged such that any alternating current induced in resistive heating element in a direction towards the negative terminal of the control circuitry is equal to the current induced in resistive heating element in a direction towards the positive terminal of the control circuitry. As a result, the total alternating current induced in the resistive heating element between the positive terminal and the negative terminal of the control circuitry is at least significantly reduced, and is approximately zero. This minimising of total alternating current induced in the resistive heating element between the positive terminal and the negative terminal of the control circuitry means that filters to ensure the induced alternating current in the resistive heating element does not cause damage to any electronic components electrically connected to the resistive heating element are not required. This may therefore significantly reduce the complexity of the control circuitry.

[0333] The at least one primary portion may be integrally formed with the at least one secondary portion.

[0334] The resistive heating element may comprise exactly one primary portion. The resistive heating element may comprise exactly one secondary portion. The primary portion and the secondary portion may extend from adjacent to the first end of the chamber to adjacent to a second end of the chamber.

[0335] The primary portion and the secondary portion may be electrically connected to the power supply at the second end of the chamber. A first end of the primary portion may be electrically connected to the positive terminal of the control circuitry. A first end of the secondary portion may be electrically connected to the negative terminal of the control circuitry.

[0336] The primary portion and the secondary portion may be directly connected to one another adjacent to the first end of the chamber. In particular, a second end of the primary portion opposite to the first end of the primary portion may be directly connected to a second end of the secondary portion opposite to the first end of the secondary portion.

[0337] The primary portion may be integrally formed with the secondary portion.

[0338] The primary portion and the secondary portion may be co-wound about the chamber such that the primary portion and the secondary portion are substantially parallel to one another. The primary portion and the secondary portion may be helically co-wound about the chamber.

[0339] Advantageously, this arrangement allows for a straightforward implementation of the above concept, and provides two co-wound portions in which the total induced alternating current between the positive terminal and the negative terminal of the control circuitry is at least significantly reduced, and is approximately zero.

[0340] The resistive heating element may be arranged in a serpentine shape. The resistive heating element may comprise two filaments arranged in a serpentine shape such that the two filaments are arranged substantially parallel to each other. In this arrangement, the resistive heating element may comprise a plurality of alternating primary portions and secondary portions as described above.

[0341] Advantageously, this arrangement allows for an implementation of the above concept in which the total induced alternating current in the serpentine resistive heating element between the positive terminal and the negative terminal of the control circuitry is at least significantly reduced, and is approximately zero.

[0342] The resistive heating element may be folded or curved to at least partially surround the chamber. Advantageously, the resistive heating element may therefore be printed onto a substantially flat and planar substrate prior to folding or curving to at least partially surround the chamber. This may provide a simple and reliable method of manufacture of the aerosolgenerating device. For example, the resistive heating element may be printed onto a substantially flat and planar polyimide substrate.

[0343] The inductor element may be an inductor coil. The inductor coil may be a helical coil. The resistive heating element may be a resistive heating coil. The resistive heating coil may be a helical coil. The resistive heating coil and the inductor coil may be co-wound. Advantageously, this may result in a space-efficient arrangement in which the two separate heating systems may be positioned adjacent to the aerosol-forming substrate when the aerosol-forming article is received in the chamber.

[0344] The resistive heating coil may be wound about a winding axis. The inductor coil may be wound about the same winding axis as the resistive heating coil.

[0345] The inductor element may comprise a first filament. The first filament may comprise a first cross sectional area.

[0346] The first cross sectional area may be defined in a first plane. The first cross sectional area may be perpendicular to the direction of extension of the first filament. The first cross sectional area may be perpendicular to the direction of extension of the first filament between the first end and the second end of the inductor element. The normal to the first plane defining the first cross sectional area may be perpendicular to the axis of winding. The first cross sectional area may be substantially constant between the first end and the second end of the inductor element. Advantageously, this arrangement may ensure that no portion of the inductor element between the first end and the second end of the inductor element generates more heating via resistive heating than any other portion.

[0347] The first cross sectional area may be perpendicular to the direction of flow of the first current. The first cross sectional area may be substantially rectangular in shape. Advantageously, a rectangular cross section has been found to increase the efficiency of the inductor element and reduce capacitive losses in the inductor element. Moreover, the size of the aerosol-generating device may therefore be reduced by using a rectangular cross section for the inductor element. The first cross sectional area may have a first width and a first thickness. The first width may be greater than the first thickness. The first width may be at least 5 times greater than the first thickness. For example, the first width may be at least 10 times greater than the first thickness. Preferably, the first width is at least 15 times greater than the first thickness. The first width may be between 0.1 millimetres and 5 millimetres. For example, the first width may be between 0.5 millimetres and 4 millimetres. Preferably, the first width is between 1 millimetre and 3 millimetres. The first thickness may be between 0.02 millimetres and 1 millimetre. The first thickness may be between 0.05 millimetres and 0.5 millimetres. Preferably, the first thickness is between 0.05 millimetres and 0.2 millimetres. The first width may be parallel to the longitudinal axis of the jacket. The first width may be parallel to the winding axis of the inductor coil. The first thickness may be perpendicular to the longitudinal axis of the jacket. The first thickness may be perpendicular to the winding axis of the inductor coil. Advantageously this shape and these dimensions of the inductor element have been found to provide minimal heating of the inductor element via resistive heating and provide strong coupling between the susceptor element and the inductor element. This results in more efficient heating of the susceptor element by the inductor element.

[0348] The resistive heating element may comprise a second filament. The second filament may comprise a second cross sectional area. The second cross sectional area may be defined in the first plane. The second cross sectional area may be defined in the same plane as the first cross sectional area. The second cross sectional area may be perpendicular to the direction of extension of the second filament. The second cross sectional area may be perpendicular to the direction of extension of the second filament between the first end and the second end of the resistive heating element. The normal to the first plane defining the second cross sectional area may be perpendicular to the axis of winding. The second cross sectional area may be substantially constant between the first end and the second end of the resistive heating element. The first cross sectional area may be greater than the second cross sectional area. The first cross sectional area may be at least 5 times greater than the second cross sectional area. For example, the first cross sectional area may be at least 10 times greater than the second cross sectional area. Preferably, the first cross sectional area is at least 15 times greater than the second cross sectional area. Preferably still, the first cross sectional area is at least 20 times greater than the second cross sectional area. Advantageously, a large ratio of first to second cross sectional areas means that resistive heating in the inductor element is reduced, and the majority of resistive heating occurs in the resistive heating element as intended.

[0349] The second cross sectional area may be perpendicular to the direction of flow of the second current. The second cross sectional area may be substantially circular in shape. The second cross sectional area may have a diameter between 0.1 millimetres and 0.4 millimetres. Advantageously this shape and these dimensions of the resistive heating element have been found to enable suitable heating of the resistive heating element via resistive heating. This results in more efficient heating of the periphery of the aerosol-forming substrate by the resistive heating element.

[0350] Preferably, the second cross sectional area is substantially rectangular in shape. Advantageously, a rectangular cross section has been found to increase the efficiency of the resistive heating element because a rectangular cross section provides a greater contact area with a periphery of the aerosol-forming substrate or the jacket. The second cross sectional area may have a second width and a second thickness. The second width may be greater than the second thickness. The second width may be at least 5 times greater than the second thickness. For example, the second width may be at least 10 times greater than the second thickness. Preferably, the second width is at least 25 times greater than the second thickness. The second width may be between 0.1 millimetres and 5 millimetres. For example, the second width may be between 0.2 millimetres and 2 millimetres. Preferably, the second width is between 0.5 millimetres and 0.7 millimetres. The second thickness may be between 0.005 millimetres and 0.5 millimetres. The second thickness may be between 0.01 millimetres and 0.1 millimetres. Preferably, the second thickness is between 0.02 millimetres and 0.05 millimetres. The second width may be parallel to the longitudinal axis of the jacket. The second width may be parallel to the winding axis of the inductor coil. The second thickness may be perpendicular to the longitudinal axis of the jacket. The second thickness may be perpendicular to the winding axis of the inductor coil. Advantageously this shape and these dimensions of the resistive heating element have been found to provide efficient resistive heating of a periphery of the aerosol-forming substrate.

[0351] The inductor element may comprise metal. The inductor element may comprise copper. The inductor element may comprise consist of copper. Advantageously, copper has been found to provide minimal heating of the inductor element via resistive heating and provide strong coupling between the susceptor element and the inductor element. This results in more efficient heating of the susceptor element by the inductor element.

[0352] The resistive heating element may comprise metal. The resistive heating element may comprise stainless steel. The resistive heating element may consist of stainless steel. Advantageously, stainless steel has been found to be a durable material with a resistivity suitable for maximising the heating of the resistive heating element via resistive heating. This results in more efficient heating of the periphery of the aerosol-forming substrate by the resistive heating element.

[0353] The inductor element may comprise a different material to the resistive heating element. The inductor element may consist of a different material to the resistive heating element.

[0354] In a further embodiment of the sixth aspect, the internal heater may comprise an internal resistive heating element and the external heater may comprise an external resistive heating element.

[0355] The internal resistive heating element may be disposed within the chamber. The internal resistive heating element may comprise at least one pin configured to be inserted into the aerosol-generating substrate when the aerosol-generating article is received in the chamber. The internal resistive heating element may comprise at least one blade configured to be inserted into the aerosol-generating substrate when the aerosol-generating article is received in the chamber. The internal resistive heating element may be configured to be resistively heated when supplied with a direct current.

[0356] The external resistive heating element may be disposed adjacent to the chamber. The external resistive heating element may be configured to be resistively heated when supplied with a direct current. The external resistive heating element may be folded or curved to at least partially surround the chamber. Advantageously, the external resistive heating element may therefore be printed onto a substantially flat and planar substrate prior to folding or curving to at least partially surround the chamber. This may provide a simple and reliable method of manufacture of the aerosol-generating device. For example, the external resistive heating element may be printed onto a substantially flat and planar polyimide substrate.

[0357] The external resistive heating element may be wound about a winding axis. The external resistive heating element may comprise a filament. The filament may comprise a cross sectional area. The cross sectional area may be defined in a first plane. The cross sectional area may be perpendicular to the direction of extension of the filament. The cross sectional area may be perpendicular to the direction of extension of the filament between the first end and the second end of the external resistive heating element. The normal to the first plane defining the cross sectional area may be perpendicular to the axis of winding. The cross sectional area may be substantially constant between the first end and the second end of the resistive heating element.

[0358] The cross sectional area may be perpendicular to the direction of flow of the second current. The cross sectional area may be substantially circular in shape. The cross sectional area may have a diameter between 0.1 millimetres and 0.4 millimetres. Advantageously this shape and these dimensions of the external resistive heating element have been found to enable suitable heating of the external resistive heating element via resistive heating. This results in more efficient heating of the periphery of the aerosol-forming substrate by the external resistive heating element.

[0359] Preferably, the cross sectional area is substantially rectangular in shape. Advantageously, a rectangular cross section has been found to increase the efficiency of the external resistive heating element because a rectangular cross section provides a greater contact area with a periphery of the aerosol-forming substrate or the jacket. The cross sectional area may have a width and a thickness. The width may be greater than the thickness. The width may be at least 5 times greater than the thickness. For example, the width may be at least 10 times greater than the thickness. Preferably, the width is at least 25 times greater than the thickness. The width may be between 0.1 millimetres and 5 millimetres. For example, the width may be between 0.2 millimetres and 2 millimetres. Preferably, the width is between 0.5 millimetres and 0.7 millimetres. The thickness may be between 0.005 millimetres and 0.5 millimetres. The thickness may be between 0.01 millimetres and 0.1 millimetres. Preferably, the thickness is between 0.02 millimetres and 0.05 millimetres. The width may be parallel to the longitudinal axis of the jacket. The thickness may be perpendicular to the longitudinal axis of the jacket.. Advantageously this shape and these dimensions of the external resistive heating element have been found to provide efficient resistive heating of a periphery of the aerosol-forming substrate. In this further embodiment, the first current may be a direct current. The control circuitry may be configured so that the internal resistive heating element is not supplied with the second current. The control circuitry may be configured so that the internal resistive heating element is solely supplied with the first current.

[0360] In this further embodiment, the second current may also be a direct current. The control circuitry may be configured so that the external resistive heating element is not supplied with the first current. The control circuitry may be configured so that the external resistive heating element is solely supplied with the second current.

[0361] Advantageously, this may mean when the first and second current are supplied in an alternating fashion, power is supplied from the power supply to only one of the internal resistive heating element and the external resistive heating element at any one time. As above, this may advantageously ensure that the power supply is utilized optimally and efficiently.

[0362] The control circuitry may be configured to provide the second current to the external resistive heating element and the first current to the internal resistive heating element such that the external resistive heating element and the internal resistive heating element are heated to at least 80°C. Advantageously, heating the external resistive heating element and the internal resistive heating element to at least 80°C may ensure that the external resistive heating element and the internal resistive heating element adequately heat the aerosolforming substrate such that vapour may be produced. The control circuitry may be configured to provide the second current to the external resistive heating element and the first current to the internal resistive heating element such that the external resistive heating element and the internal resistive heating element are heated to no more than 210°C. Advantageously, heating the external resistive heating element and the internal resistive heating element to no more than 210°C may ensure that the external resistive heating element and the internal resistive heating element do not burn or scorch the aerosol-forming substrate, as this may otherwise produce undesirable compounds, creating an aerosol with a burnt taste for the user.

[0363] The external resistive heating element may comprise metal. The external resistive heating element may comprise stainless steel. The external resistive heating element may consist of stainless steel. Advantageously, stainless steel has been found to be a durable material with a resistivity suitable for maximising the heating of the external resistive heating element via resistive heating. This results in more efficient heating of the periphery of the aerosol-forming substrate by the external resistive heating element.

[0364] The internal resistive heating element may comprise metal. The internal resistive heating element may comprise stainless steel. The internal resistive heating element may consist of stainless steel. Advantageously, stainless steel has been found to be a durable material with a resistivity suitable for maximising the heating of the internal resistive heating element via resistive heating. This results in more efficient heating of the inner portion of the aerosol-forming substrate by the internal resistive heating element.

[0365] In a further embodiment still of the sixth aspect, the internal heater may comprise an internal resistive heating element and the external heater may comprise an external inductive heating element.

[0366] The internal resistive heating element may be disposed within the chamber. The internal resistive heating element may comprise at least one pin configured to be inserted into the aerosol-generating substrate when the aerosol-generating article is received in the chamber. The internal resistive heating element may comprise at least one blade configured to be inserted into the aerosol-generating substrate when the aerosol-generating article is received in the chamber. The internal resistive heating element may be configured to be resistively heated when supplied with a direct current.

[0367] In this further embodiment, the first current may be a direct current. The control circuitry may be configured so that the internal resistive heating element is not supplied with the second current. The control circuitry may be configured so that the internal resistive heating element is solely supplied with the first current.

[0368] In this further embodiment, the second current may be an alternating current. The control circuitry may be configured so that the external inductive heating element is not supplied with the first current. The control circuitry may be configured so that the external inductive heating element is solely supplied with the second current.

[0369] Advantageously, this may mean when the first and second current are supplied in an alternating fashion, power is supplied from the power supply to only one of the internal resistive heating element and the external inductive heating element at any one time. As above, this may advantageously ensure that the power supply is utilized optimally and efficiently.

[0370] The external inductive heating element may be disposed adjacent to the chamber. The external inductive heating element may comprise an inductor element and a susceptor element. The susceptor element may comprise a susceptor sleeve disposed adjacent to the chamber. The susceptor element may at least partially surround the chamber. The susceptor element may at least partially surround the jacket. The susceptor element may be located on an outer surface of the jacket.

[0371] The inductor element may comprise an inductor coil. The inductor coil may be a helical coil. The inductor element may at least partially surround the susceptor element. The inductor element may be configured to generate an alternating magnetic field in the region of the susceptor element when supplied with an alternating current. The alternating magnetic field may heat the susceptor element. Advantageously, the aerosol-forming substrate within the aerosol-generating article may therefore be efficiently heated both externally and internally.

[0372] The second current may be an alternating current. The alternating current may have a first frequency. The control circuitry may be configured so that the inductor element is not supplied with the first current. The control circuitry may be configured so that the inductor element is not supplied with a direct current. The control circuitry may be configured so that the inductor element is solely supplied with the second current. Advantageously, this may provide minimal resistive heating of the inductor element, which may reduce the risk of a portion of the housing of the aerosol-generating device heating in an undesired fashion.

[0373] The inductor element may comprise a first filament. The first filament may comprise a first cross sectional area. The first cross sectional area may be defined in a first plane. The first cross sectional area may be perpendicular to the direction of extension of the first filament. The first cross sectional area may be perpendicular to the direction of extension of the first filament between the first end and the second end of the inductor element. The normal to the first plane defining the first cross sectional area may be perpendicular to the axis of winding. The first cross sectional area may be substantially constant between the first end and the second end of the inductor element. Advantageously, this arrangement may ensure that no portion of the inductor element between the first end and the second end of the inductor element generates more heating via resistive heating than any other portion.

[0374] The first cross sectional area may be perpendicular to the direction of flow of the second current. The first cross sectional area may be substantially rectangular in shape. Advantageously, a rectangular cross section has been found to increase the efficiency of the inductor element and reduce capacitive losses in the inductor element. Moreover, the size of the aerosol-generating device may therefore be reduced by using a rectangular cross section for the inductor element. The first cross sectional area may have a first width and a first thickness. The first width may be greater than the first thickness. The first width may be at least 5 times greater than the first thickness. For example, the first width may be at least 10 times greater than the first thickness. Preferably, the first width is at least 15 times greater than the first thickness. The first width may be between 0.1 millimetres and 5 millimetres. For example, the first width may be between 0.5 millimetres and 4 millimetres. Preferably, the first width is between 1 millimetre and 3 millimetres. The first thickness may be between 0.02 millimetres and 1 millimetre. The first thickness may be between 0.05 millimetres and 0.5 millimetres. Preferably, the first thickness is between 0.05 millimetres and 0.2 millimetres. The first width may be parallel to the longitudinal axis of the jacket. The first width may be parallel to the winding axis of the inductor coil. The first thickness may be perpendicular to the longitudinal axis of the jacket. The first thickness may be perpendicular to the winding axis of the inductor coil. Advantageously this shape and these dimensions of the inductor element have been found to provide minimal heating of the inductor element via resistive heating and provide strong coupling between the susceptor element and the inductor element. This results in more efficient heating of the susceptor element by the inductor element.

[0375] The control circuitry may be configured to provide the first current to the internal resistive heating element such that the internal resistive heating element is heated to at least 80°C. Advantageously, heating the internal resistive heating element to at least 80°C may ensure that the internal resistive heating element adequately heats the aerosol-forming substrate such that vapour may be produced. The control circuitry may be configured to provide the first current to the internal resistive heating element such that the internal resistive heating element is heated to no more than 210°C. Advantageously, heating the internal resistive heating element to no more than 210°C may ensure that the internal resistive heating element does not burn or scorch the aerosol-forming substrate, as this may otherwise produce undesirable compounds, creating an aerosol with a burnt taste for the user.

[0376] The inductor element may comprise metal. The inductor element may comprise copper. The inductor element may comprise consist of copper. Advantageously, copper has been found to provide minimal heating of the inductor element via resistive heating and provide strong coupling between the susceptor element and the inductor element. This results in more efficient heating of the susceptor element by the inductor element.

[0377] The internal resistive heating element may comprise metal. The internal resistive heating element may comprise stainless steel. The internal resistive heating element may consist of stainless steel. Advantageously, stainless steel has been found to be a durable material with a resistivity suitable for maximising the heating of the internal resistive heating element via resistive heating. This results in more efficient heating of the inner portion of the aerosol-forming substrate by the internal resistive heating element.

[0378] There is also provided according to a seventh aspect of the present disclosure, an aerosol-generating system comprising an aerosol-generating device according to the sixth aspect of the present disclosure, and aerosol-generating article comprising an aerosolgenerating substrate, wherein the aerosol-generating article is received in the chamber of the aerosol-generating device. The aerosol-generating article may comprise any aerosolgenerating article according to the fourth aspect of the present disclosure.

[0379] According to an eighth aspect of the disclosure, there is provided a method of controlling an aerosol-generating system to generate an aerosol, the system comprising: an aerosol-generating article comprising an aerosol-forming substrate, and an aerosol-generating device, the aerosol-generating device comprising a chamber for receiving at least a portion of an aerosol-generating article; the aerosol-generating device further comprising: an internal heater; an external heater; at least one power supply for providing electrical power to the internal heater and the external heater; and control circuitry configured to control the supply of power from the at least one power supply to the internal heater and the external heater, wherein the method comprises the steps of: providing electrical power to the internal heater, such that the internal heater heats the aerosol-forming substrate from an internal location within the aerosol-forming substrate, providing electrical power to the external heater, such that the external heater heats the aerosol-forming substrate from an external location outside of the aerosol-forming substrate, and preventing the supply of power to one of the external heater or the internal heater when power is supplied to the other of the external heater or the internal heater.

[0380] Advantageously, by preventing the supply of power to the external heater when power is supplied to the internal heater, the aerosol-generating device may utilise energy stored in the at least one power supply in a more efficient manner, which may allow for a longer aerosol-generating experience for a user. It has been found that simultaneous supply from a power supply to two separate internal and external heaters is detrimental to the efficiency of the at least one power supply.

[0381] The aerosol-generating device may comprise any aerosol-generating device according to the sixth aspect of the present disclosure.

[0382] Providing electrical power to the internal heater may comprise providing a first current to the internal heater.

[0383] Providing electrical power to the external heater may comprise providing a second current to the external heater.

[0384] The method may comprise preventing the supply of power to the external heater when power is supplied to the internal heater. The method may comprise controlling the supply of power to the external heater dependent on a power supply profile supplied to the internal heater. For example, the method may comprise preventing the supply of power to the external heater when power is supplied to the internal heater, and not preventing the supply of power to the external heater when power is not supplied to the internal heater. In other words, the method may comprise allowing the supply of power to the external heater when power is not supplied to the internal heater.

[0385] The method may comprise preventing the supply of power to the internal heater when power is supplied to the external heater. The method may comprise controlling the supply of power to the internal heater dependent on a power supply profile supplied to the external heater. For example, the method may comprise preventing the supply of power to the internal heater when power is supplied to the external heater, and not preventing the supply of power to the internal heater when power is not supplied to the external heater. In other words, the method may comprise allowing the supply of power to the internal heater when power is not supplied to the external heater.

[0386] The method may further comprise providing the first current to the internal heater and the second current to the external heater at different times.

[0387] For example, the method may further comprise providing the first current to the internal heater and then subsequently the second current to the external heater. The method may further comprise providing the first current to the internal heater for a first time period. The method may further comprise providing the second current to the external heater for a second time period after the first time period. Advantageously, the aerosol-forming substrate may be non-uniform, and heating the aerosol-forming substrate internally then subsequently externally may heat different portions of the aerosol-forming substrate at different times. As the aerosol-forming substrate may be non-uniform, this may result in aerosol with aerosol characteristics being produced at different times.

[0388] The method may further comprise providing the second current to the external heater and then subsequently the first current to the internal heater. The method may further comprise providing the second current to the external heater for a first time period. The method may further comprise providing the first current to the internal heater for a second time period after the first time period. Advantageously, the aerosol-forming substrate may be non-uniform, and heating the aerosol-forming substrate via resistive heating then subsequently by inductive heating may heat different portions of the aerosol-forming substrate at different times. As the aerosol-forming substrate may be non-uniform, this may result in aerosol with aerosol characteristics being produced at different times.

[0389] The method may further comprise detecting when the user takes a puff on the system. For example, the control circuitry may be coupled to a pressure sensor, the method comprising detecting a pressure drop when the user takes a puff on the system. The method may further comprise supplying power to the internal heater or the external heater, or the internal heater and the external heater, when the pressure sensor detects a pressure drop when the user takes a puff on the system. For example, the method may further comprise starting the first time period in response to the user taking a puff on the system.

[0390] The control circuitry may comprise a user-activatable trigger. For example, the user- activatable trigger may comprise a button or a switch. The method may further comprise starting the first time period in response to the user-activatable trigger being activated.

[0391] The method may further comprise ending the first time period and starting the second time period in response to: a predetermined number of puffs on the system being taken; or a predetermined time from a first puff on the system passing; or the user-activatable trigger being activated; or a combination of any one or more of the above.

[0392] The method may further comprise providing the first current to the internal heater and the second current to the external heater in an alternating sequence. Advantageously, it may be beneficial to alternate internal and external heating in order to avoid overheating of any part of the aerosol-forming substrate.

[0393] The control circuitry may comprise a microcontroller. The method may further comprise receiving an internal heating feedback signal from the internal heater and an external heating feedback signal from the external heater. The internal heating feedback signal may comprise at least one of a voltage, a current or a conductance. For example, the internal heating feedback signal may comprise a voltage and a current. The external heating feedback signal may comprise at least one of a voltage, a current or a conductance. For example, the external heating feedback signal may comprise a voltage and a current.

[0394] The method may further comprise providing the first current to the internal heater based on the internal heating feedback signal. The method may further comprise providing the second current to the external heater based on the external heating feedback signal. The internal heating feedback signal may be dependent on a temperature of a component of the internal heater. The external heating feedback signal may be dependent on a temperature of a component of the external heater.

[0395] The method may further comprise adjusting the first current provided to the internal heater dependent on the internal heating feedback signal. The method may further comprise determining a temperature of the component of the internal heater dependent on the internal heating feedback signal. The method may further comprise adjusting the first current provided to the internal heater dependent on the internal heating feedback signal to maintain the temperature of the component of the internal heater at an internal heater target temperature or to follow an internal heater target temperature profile.

[0396] The method may further comprise adjusting the second current provided to the external heater dependent on the external heating feedback signal. The method may further comprise determining a temperature of the external heater dependent on the external heating feedback signal. The method may further comprise adjusting the second current provided to the external heater dependent on the external heating feedback signal to maintain the temperature of the component of the external heater at an external heater target temperature or to follow an external heater target temperature profile.

[0397] The method may further comprise providing the first current to the internal heater during on periods, and preventing the first current from being provided to the internal heater during off periods. The method may further comprise providing the second current to the external heater during off periods, and preventing the second current from being provided to the external heater during on periods. The method may further comprise alternating the on periods with the off periods.

[0398] The method may further comprise supplying a switching voltage to a control circuitry component in order to control the first current provided to the internal heater. Specifically, in embodiments as described below in which the internal heater comprises an inductor element, the method may further comprise supplying a switching voltage to the DC / AC converter in order to control the first current provided to the internal heater. In particular, the method may further comprise supplying the switching voltage to a Field Effect Transistor of the DC / AC converter in order to control the first current provided to the internal heater.

[0399] The method may further comprise supplying a switching voltage to a control circuitry component in order to control the second current provided to the external heater. Specifically, in embodiments as described below in which the external heater comprises an inductor element, the method may further comprise supplying a switching voltage to the DC / AC converter in order to control the second current provided to the external heater. In particular, the method may further comprise supplying the switching voltage to a Field Effect Transistor of the DC / AC converter in order to control the second current provided to the external heater.

[0400] The switching voltage may have a rectangular profile.

[0401] The switching voltage may comprise alternating on periods wherein the first current is provided to the internal heater, and off periods where the first current is prevented from being provided to the internal heater. The control circuitry may be configured to prevent the supply of the second current to the external heater during the on periods.

[0402] The switching voltage may comprise alternating off periods wherein the second current is provided to the external heater, and on periods where the second current is prevented from being provided to the external heater. The control circuitry may be configured to prevent the supply of the first current to the internal heater during the on periods.

[0403] Specifically, the method may further comprise supplying a switching voltage to the DC / AC converter in order to control the first current provided to the internal heater. In particular, the method may further comprise supplying the switching voltage to a Field Effect Transistor of the DC / AC converter in order to control the first current provided to the internal heater. The switching voltage may have a rectangular profile. The switching voltage may comprise alternating on periods wherein the first current is provided to the internal heater, and off periods where the first current is prevented from being provided to the internal heater.

[0404] The temperature of the component of the internal heater may be controlled by adjusting the length of the on periods. For example, the method may further comprise adjusting the length of the on periods to maintain the temperature of the component of the internal heater at the internal heater target temperature or to follow the internal heater target temperature profile.

[0405] The method may further comprise providing the first current to the internal heater in one or more pulses during each of the on periods. The pulses may comprise a plurality of separate pulses. The method may further comprise preventing the supply of the first current to the internal heater when not during the pulses.

[0406] The method may further comprise adjusting the pulses during each of the on periods to control the temperature of the component of the internal heater. For example, the method may further comprise using pulse-width modulation to control the temperature of the component of the internal heater. The method may further comprise adjusting one or more of a duration of each of the pulses, a number of each of the pulses, or a time gap between adjacent pulses during each of the on periods to control the temperature of the component of the internal heater. For example, the method may further comprise adjusting the pulses during each of the on periods to maintain the temperature of the component of the internal heater at the internal heater target temperature or to follow the internal heater target temperature profile.

[0407] The pulses may occupy a proportion of each of the on periods. For example, the pulses may occupy 100% of each on period such that the first current is supplied to the internal heater during each on period for the entirety of each on period. As another example, the pulses may occupy 50% of each on period such that the first current is supplied to the internal heater during each on period for half the duration of each on period. The method may further comprise adjusting the proportion of each of the on periods occupied by the pulses to control the temperature of the component of the internal heater. For example, the method may further comprise adjusting the proportion of each of the on periods occupied by the pulses to maintain the temperature of the component of the internal heater at the internal heater target temperature or to follow the internal heater target temperature profile.

[0408] The on periods may be between 3000 milliseconds and 1 millisecond in length. The on periods may be between 500 milliseconds and 1 millisecond in length. Preferably, the on periods are between 100 milliseconds and 5 milliseconds in length. Preferably still, the on periods are between 50 milliseconds and 10 milliseconds in length. Even more preferably, the on periods are about 20 milliseconds in length.

[0409] The off periods may be between 3000 milliseconds and 1 millisecond in length. The off periods may be between 500 milliseconds and 1 millisecond in length. Preferably, the off periods are between 200 milliseconds and 10 milliseconds in length. Preferably still, the off periods are between 100 milliseconds and 50 milliseconds in length. Even more preferably, the off periods are about 70 milliseconds in length. The method may further comprise providing the second current to the external heater during the off periods. In particular, the method may further comprise providing the second current to the external heater only during the off periods.

[0410] The temperature of the component of the external heater may be controlled by adjusting the length of the off periods. For example, the method may further comprise adjusting the length of the off periods to maintain the temperature of the component of the external heater at the external heater target temperature or to follow the external heater target temperature profile.

[0411] The method may further comprise providing the second current to the external heater in one or more pulses during each of the off periods. The pulses may comprise a plurality of separate pulses. The method may further comprise preventing the supply of the second current to the external heater when not during the pulses.

[0412] The method may further comprise adjusting the pulses during each of the off periods to control the temperature of the component of the external heater. For example, the method may further comprise using pulse-width modulation to control the temperature of the component of the external heater. The method may further comprise adjusting one or more of a duration of each of the pulses, a number of each of the pulses, or a time gap between adjacent pulses during each of the off periods to control the temperature of the component of the external heater. For example, the method may further comprise adjusting the pulses during each of the off periods to maintain the temperature of the component of the external heater at the external heater target temperature or to follow the external heater target temperature profile.

[0413] The pulses may occupy a proportion of each of the off periods. For example, the pulses may occupy 100% of each off period such that the second current is supplied to the external heater during each off period for the entirety of each off period. As another example, the pulses may occupy 50% of each off period such that the second current is supplied to the external heater during each off period for half the duration of each off period. The method may further comprise adjusting the proportion of each of the off periods occupied by the pulses to control the temperature of the component of the external heater. For example, the method may further comprise adjusting the proportion of each of the off periods occupied by the pulses to maintain the temperature of the component of the external heater at the external heater target temperature or to follow the external heater target temperature profile.

[0414] The method may further comprise providing the second current to the external heater for reduced time periods. Each of the reduced time periods may be shorter than each of the off periods. The method may further comprise adjusting the length of the reduced time periods to control the temperature of the component of the external heater. Advantageously, by providing the second current to the external heater during the off periods but for reduced time periods shorter than the off periods, the control circuitry may avoid any overlap between the first current being provided to the internal heater and the second current being provided to the external heater.

[0415] As the first current supplied from the power supply may not instantaneously drop to zero when the first current applied to the internal heater is stopped, including time gaps between the reduced time periods and the periods when the first current is provided to the internal heater may advantageously ensure that the first current and second current are not simultaneously supplied to the internal and external heaters respectively, which may have a negative impact on the power supply, for example this may reduce the operational life of the power supply.

[0416] Also advantageously, the temperature of the component of the external heater may be controlled by adjusting the length of the reduced time periods. For example, the method may further comprise adjusting the length of the reduced time periods to maintain the temperature of the component of the external heater at the external heater target temperature or to follow the external heater target temperature profile. The temperature of the component of the external heater may be controlled by adjusting the length of time gaps between the reduced time periods and the on periods. For example, the method may further comprise adjusting the length of time gaps between the reduced time periods and the on periods to maintain the temperature of the component of the external heater at the external heater target temperature or to follow the external heater target temperature profile. This allows the control circuitry to maintain the temperature of the component of the external heater at the external heater target temperature, or to follow the external heater target temperature profile, using pulse-width modulation.

[0417] The method may further comprise performing a calibration process prior to alternating the on periods with the off periods. The method may further comprise performing the calibration process immediately after the aerosol-generating device is switched on. In particular, the method may further comprise performing the calibration process prior to supplying the second current to the external heater.

[0418] The method may further comprise adjusting the first current provided to the internal heater to maintain the temperature of the component of the internal heater at the internal heater target temperature or to follow the internal heater target temperature profile. For example, the method may further comprise adjusting an amplitude of the first current provided to the internal heater to maintain the temperature of the component of the internal heater at the internal heater target temperature or to follow the internal heater target temperature profile.

[0419] The method may further comprise adjusting the second current provided to the external heater to maintain the temperature of the component of the external heater at the external heater target temperature or to follow the external heater target temperature profile. For example, the method may further comprise adjusting an amplitude of the second current provided to the external heater to maintain the temperature of the component of the external heater at the external heater target temperature or to follow the external heater target temperature profile.

[0420] In an embodiment of the eighth aspect, the internal heater may comprise an inductor element and the external heater may comprise a resistive heating element. The inductor element may be disposed adjacent to the chamber. The inductor element may be configured to generate an alternating magnetic field within the chamber when supplied with an alternating current. The resistive heating element may be disposed adjacent to the chamber. The resistive heating element may be configured to be resistively heated when supplied with a direct current.

[0421] Providing electrical power to the internal heater may comprise supplying an alternating current to the inductor element. The alternating current may have a first frequency. The method may further comprise not supplying the inductor element with the second current. The method may further comprise not supplying the inductor element with a direct current. The method may further comprise solely supplying the inductor element with the first current. Advantageously, this may provide minimal resistive heating of the inductor element, which may reduce the risk of a peripheral portion of an aerosol-forming substrate being overheated or burnt.

[0422] When supplied with the first current, the inductor element may generate an alternating magnetic field within the chamber to inductively heat one or more susceptors within an aerosol-generating article when the aerosol-generating article is received within the chamber. Advantageously, the aerosol-forming substrate within the aerosol-generating article may therefore be efficiently heated both externally and internally.

[0423] The aerosol-forming article may comprise the one or more susceptors. The one or more susceptors may be in the form of at least one strip or at least one rod or at least one particle. Advantageously, the construction of the aerosol-generating device may be simplified, as it is not required that the aerosol-generating device comprise a susceptor element. The one or more susceptors may be in the form of elongated particles. The elongated particles may be aligned with a longitudinal direction of the aerosol-generating article. The elongated particles may be aligned with a longitudinal direction of the aerosolforming substrate. The one or more susceptors may be in the form of one or more strips of susceptor material. The aerosol-generating article may comprise one or more strips of aerosol-forming substrate laminated with one on more strips of susceptor material. For example, the aerosol-generating article may comprise one or more strips of tobacco material laminated with one on more strips of susceptor material. The aerosol-generating device may comprise the one or more susceptors. The one or more susceptors may be in the form of at least one blade or at least one pin. Advantageously, the one or more susceptors may be reused with multiple aerosol-forming articles. The one or more susceptors may be configured to be inserted into the aerosolgenerating substrate when the aerosol-generating article is received in the chamber. Advantageously, this may allow for a simpler and more sustainable form of aerosol-forming article to be used.

[0424] Providing electrical power to the external heater may comprise supplying an direct current to the resistive heating element. The method may further comprise not supplying the resistive heating element with the first current. The method may further comprise not supplying the resistive heating element with an alternating current. The method may further comprise solely supplying the resistive heating element with the second current.. Advantageously, this may mean that the resistive heating element has no magnetic interaction with the inductor element.

[0425] The method may further comprise providing the second current to the resistive heating element such that the resistive heating element is heated to at least 80°C. Advantageously, heating the resistive heating element to at least 80°C may ensure that the resistive heating element adequately heats the aerosol-forming substrate such that vapour may be produced. The method may further comprise providing the second current to the resistive heating element such that the resistive heating element is heated to no more than 210°C. Advantageously, heating the resistive heating element to no more than 210°C may ensure that the resistive heating element does not burn or scorch the aerosol-forming substrate, as this may otherwise produce undesirable compounds, creating an aerosol with a burnt taste for the user.

[0426] When an alternating magnetic field is generated by supplying an alternating current in the inductor element, the alternating magnetic field may induce an induced alternating current in the resistive heating element. Therefore, when the first current is supplied to the inductor element at the same time as the second current is supplied to the resistive heating element, the induced alternating current in the resistive heating element may affect the resistive heating feedback signal provided to the control circuitry. For example, the induced alternating current in the resistive heating element may modify the resistive heating feedback signal provided to the control circuitry. This may affect the ability of the control circuitry to accurately determine the temperature of the resistive heating element, and therefore affect the ability of the control circuitry to maintain the temperature of the resistive heating element at the external heater target temperature or to follow the external heater target temperature profile. Advantageously, when the method comprises preventing the supply of the second current to the resistive heating element when the first current is supplied to the inductor element, the induced alternating current does not affect the resistive heating feedback signal. Therefore the method can more accurately determine the temperature of the resistive heating element.

[0427] Similarly, the method may further comprise preventing the supply of the first current to the inductor element when the second current is supplied to the resistive heating element. The method may further comprise preventing simultaneous supply of the first current to the inductor element and the second current to the resistive heating element.

[0428] When an alternating magnetic field is generated in the chamber by an alternating current in the inductor coil, depending on the configuration of the adjacent resistive heating element, the alternating magnetic field may induce an alternating current in an adjacent resistive heating element. The resistive heating element may be configured such that a total current induced in the resistive heating element by the alternating magnetic field is substantially zero, as described with respect to the sixth aspect of the present disclosure.

[0429] In a further embodiment of the eighth aspect, the internal heater may comprise an internal resistive heating element and the external heater may comprise an external resistive heating element.

[0430] In this further embodiment, the first current may be a direct current, such that providing electrical power to the internal heater may comprise providing a direct current to the internal resistive heating element. The method may further comprise not supplying the internal resistive heating element with the second current. The method may further comprise solely supplying the internal resistive heating element with the first current.

[0431] In this further embodiment, the second current may also be a direct current, such that providing electrical power to the external heater may comprise providing a direct current to the external resistive heating element. The method may further comprise not supplying the external resistive heating element with the first current. The method may further comprise solely supplying the external resistive heating element with the second current.

[0432] Advantageously, this may mean when the first and second current are supplied in an alternating fashion, power is supplied from the power supply to only one of the internal resistive heating element and the external resistive heating element at any one time. As above, this may advantageously ensure that the power supply is utilized optimally and efficiently.

[0433] The method may further comprise providing the second current to the external resistive heating element and the first current to the internal resistive heating element such that the external resistive heating element and the internal resistive heating element are heated to at least 80°C. Advantageously, heating the external resistive heating element and the internal resistive heating element to at least 80°C may ensure that the external resistive heating element and the internal resistive heating element adequately heat the aerosolforming substrate such that vapour may be produced. The method may further comprise providing the second current to the external resistive heating element and the first current to the internal resistive heating element such that the external resistive heating element and the internal resistive heating element are heated to no more than 210°C. Advantageously, heating the external resistive heating element and the internal resistive heating element to no more than 210°C may ensure that the external resistive heating element and the internal resistive heating element do not burn or scorch the aerosol-forming substrate, as this may otherwise produce undesirable compounds, creating an aerosol with a burnt taste for the user.

[0434] In a further embodiment still of the eighth aspect, the internal heater may comprise an internal resistive heating element and the external heater may comprise an external inductive heating element.

[0435] The internal resistive heating element may be disposed within the chamber. The internal resistive heating element may comprise at least one pin configured to be inserted into the aerosol-generating substrate when the aerosol-generating article is received in the chamber. The internal resistive heating element may comprise at least one blade configured to be inserted into the aerosol-generating substrate when the aerosol-generating article is received in the chamber. The internal resistive heating element may be configured to be resistively heated when supplied with a direct current.

[0436] In this further embodiment, the first current may be a direct current, such that providing electrical power to the internal heater may comprise providing a direct current to the internal resistive heating element. The method may further comprise not supplying the internal resistive heating element with the second current. The method may further comprise solely supplying the internal resistive heating element with the first current.

[0437] In this further embodiment, the second current may be an alternating current, such that providing electrical power to the external heater may comprise providing an alternating current to the external inductive heating element. The method may further comprise not supplying the external inductive heating element with the first current. The method may further comprise solely supplying the external inductive heating element with the second current.

[0438] Advantageously, this may mean when the first and second current are supplied in an alternating fashion, power is supplied from the power supply to only one of the internal resistive heating element and the external inductive heating element at any one time. As above, this may advantageously ensure that the power supply is utilized optimally and efficiently. The method may further comprise providing the first current to the internal resistive heating element such that the internal resistive heating element is heated to at least 80°C. Advantageously, heating the internal resistive heating element to at least 80°C may ensure that the internal resistive heating element adequately heats the aerosol-forming substrate such that vapour may be produced. The method may further comprise providing the first current to the internal resistive heating element such that the internal resistive heating element is heated to no more than 210°C. Advantageously, heating the internal resistive heating element to no more than 210°C may ensure that the internal resistive heating element does not burn or scorch the aerosol-forming substrate, as this may otherwise produce undesirable compounds, creating an aerosol with a burnt taste for the user.

[0439] As used herein, the term “aerosol-generating device” is used to describe a device that interacts with an aerosol-forming substrate to generate an aerosol. Preferably, the aerosol-generating device is a smoking device that interacts with an aerosol-forming substrate to generate an aerosol that is directly inhalable into a user’s lungs thorough the user's mouth.

[0440] As used herein, the term “aerosol-forming substrate” refers to a substrate consisting of or comprising an aerosol-forming material that is capable of releasing volatile compounds upon heating to generate an aerosol.

[0441] Preferably, the aerosol-forming substrate is a solid aerosol-forming substrate. However, the aerosol-forming substrate may comprise both solid and liquid components. Alternatively, the aerosol-forming substrate may be a liquid aerosol-forming substrate.

[0442] Preferably, the aerosol-forming substrate comprises nicotine. More preferably, the aerosol-forming substrate comprises tobacco. Alternatively or in addition, the aerosolforming substrate may comprise a non-tobacco containing aerosol-forming material.

[0443] If the aerosol-forming substrate is a solid aerosol-forming substrate, the solid aerosolforming substrate may comprise, for example, one or more of: powder, granules, pellets, shreds, strands, strips or sheets containing one or more of: herb leaf, tobacco leaf, tobacco ribs, expanded tobacco and homogenised tobacco.

[0444] Optionally, the solid aerosol-forming substrate may contain tobacco or non-tobacco volatile flavour compounds, which are released upon heating of the solid aerosol-forming substrate. The solid aerosol-forming substrate may also contain one or more capsules that, for example, include additional tobacco volatile flavour compounds or non-tobacco volatile flavour compounds and such capsules may melt during heating of the solid aerosol-forming substrate.

[0445] Optionally, the solid aerosol-forming substrate may be provided on or embedded in a thermally stable carrier. The carrier may take the form of powder, granules, pellets, shreds, strands, strips or sheets. The solid aerosol-forming substrate may be deposited on the surface of the carrier in the form of, for example, a sheet, foam, gel or slurry. The solid aerosol-forming substrate may be deposited on the entire surface of the carrier, or alternatively, may be deposited in a pattern in order to provide a non-uniform flavour delivery during use.

[0446] In a preferred embodiment, the aerosol-forming substrate comprises homogenised tobacco material. As used herein, the term “homogenised tobacco material” refers to a material formed by agglomerating particulate tobacco.

[0447] Preferably, the aerosol-forming substrate comprises a gathered sheet of homogenised tobacco material. As used herein, the term “sheet” refers to a laminar element having a width and length substantially greater than the thickness thereof. As used herein, the term “gathered” is used to describe a sheet that is convoluted, folded, or otherwise compressed or constricted substantially transversely to the longitudinal axis of the aerosolgenerating article. Preferably, the aerosol-forming substrate comprises an aerosol former. As used herein, the term “aerosol former” is used to describe any suitable known compound or mixture of compounds that, in use, facilitates formation of an aerosol and that is substantially resistant to thermal degradation at the operating temperature of the aerosolgenerating article.

[0448] Suitable aerosol-formers are known in the art and include, but are not limited to: polyhydric alcohols, such as propylene glycol, triethylene glycol, 1 ,3-butanediol and glycerine; esters of polyhydric alcohols, such as glycerol mono-, di- or triacetate; and aliphatic esters of mono-, di- or polycarboxylic acids, such as dimethyl dodecanedioate and dimethyl tetradecanedioate. Preferred aerosol formers are polyhydric alcohols or mixtures thereof, such as propylene glycol, triethylene glycol, 1 ,3-butanediol and, most preferred, glycerine.

[0449] The aerosol-forming substrate may comprise a single aerosol former. Alternatively, the aerosol-forming substrate may comprise a combination of two or more aerosol formers.

[0450] As used herein, the term “susceptor” refers to an element comprising a material that is capable of converting the energy of a magnetic field into heat. When a susceptor is located in an alternating magnetic field, the susceptor is heated. Heating of the susceptor may be the result of at least one of hysteresis losses and eddy currents induced in the susceptor, depending on the electrical and magnetic properties of the susceptor material.

[0451] As used herein, the term “inductively couple” refers to the heating of a susceptor when penetrated by an alternating magnetic field. The heating may be caused by the generation of eddy currents in the susceptor. The heating may be caused by magnetic hysteresis losses.

[0452] As used herein, the term “puff” means the action of a user drawing an aerosol into their body through their mouth or nose. As used herein when referring to an aerosol-generating device, the terms “upstream” and “downstream” are used to describe the relative positions of components, or portions of components, of the aerosol-generating device in relation to the direction in which air flows through the aerosol-generating device during use thereof. Aerosol-generating devices according to the invention may comprise a proximal end through which, in use, an aerosol exits the device. The proximal end of the aerosol-generating device may also be referred to as the mouth end or the downstream end. The mouth end is downstream of the distal end. The distal end of the aerosol-generating device may also be referred to as the upstream end. Components, or portions of components, of the aerosol-generating device may be described as being upstream or downstream of one another based on their relative positions with respect to the airflow path of the aerosol-generating device. As used herein when referring to an aerosol-generating article, the terms “upstream” and “downstream” are used to describe the relative positions of components, or portions of components, of the aerosolgenerating article in relation to the direction in which air flows through the aerosol-generating article during use thereof. Aerosol-generating articles according to the invention may comprise a proximal end through which, in use, an aerosol exits the article. The proximal end of the aerosol-generating article may also be referred to as the mouth end or the downstream end. The mouth end is downstream of the distal end. The distal end of the aerosol-generating article may also be referred to as the upstream end. Components, or portions of components, of the aerosol-generating article may be described as being upstream or downstream of one another based on their relative positions between the proximal end of the aerosol-generating article and the distal end of the aerosol-generating article. The front of a component, or portion of a component, of the aerosol-generating article is the portion at the end closest to the upstream end of the aerosol-generating article. The rear of a component, or portion of a component, of the aerosol-generating article is the portion at the end closest to the downstream end of the aerosol-generating article.

[0453] The invention is defined in the claims. However, below there is provided a non- exhaustive list of non-limiting examples. Any one or more of the features of these examples may be combined with any one or more features of another example, embodiment, or aspect described herein.

[0454] Example Ex1 . An aerosol-generating device comprising: a chamber for receiving at least a portion of an aerosol-generating article; an inductor element disposed adjacent to the chamber or in the chamber; a resistive heating element disposed adjacent to the chamber or in the chamber; at least one power supply for providing electrical power to the inductor element and resistive heating element; and control circuitry configured to control the supply of power from the at least one power supply to the inductor element and the resistive heating element, wherein the control circuitry is configured to provide a first current to the inductor element, such that the inductor element generates an alternating magnetic field within the chamber, and wherein the control circuitry is configured to provide a second current to the resistive heating element for heating the chamber.

[0455] Example Ex2. The aerosol-generating device according to Example Ex1 , wherein the first current is an alternating current.

[0456] Example Ex3. The aerosol-generating device according to Example Ex1 or Ex2, wherein the control circuitry is configured so that the inductor element is not supplied with the second current.

[0457] Example Ex4. The aerosol-generating device according to any preceding Example, wherein the control circuitry is configured so that the inductor element is not supplied with a direct current.

[0458] Example Ex5. The aerosol-generating device according to any preceding Example, wherein the control circuitry is configured so that the inductor element is solely supplied with the first current.

[0459] Example Ex6. The aerosol-generating device according to any preceding Example, wherein the second current is a direct current.

[0460] Example Ex7. The aerosol-generating device according to any preceding Example, wherein the control circuitry is configured so that the resistive heating element is not supplied with the first current.

[0461] Example Ex8. The aerosol-generating device according to any preceding Example, wherein the control circuitry is configured so that the resistive heating element is not supplied with an alternating current.

[0462] Example Ex9. The aerosol-generating device according to any preceding Example, wherein the control circuitry is configured so that the resistive heating element is solely supplied with the second current.

[0463] Example Ex10. The aerosol-generating device according to any preceding Example, wherein the power supply comprises a first DC power source.

[0464] Example Ex11. The aerosol-generating device according to Example Ex10, wherein the first DC power source is a battery.

[0465] Example Ex12. The aerosol-generating device according to Example Ex10 or Ex11 , wherein the control circuitry comprises a DC / AC converter connected to the first DC power source. Example Ex13. The aerosol-generating device according to Example Ex12, wherein the DC / AC converter includes a Class-E power amplifier including a first transistor switch and an LC load network.

[0466] Example Ex14. The aerosol-generating device according to any preceding Example, wherein the control circuitry is configured to provide the second current to the resistive heating element such that the resistive heating element is heated to at least 80°C.

[0467] Example Ex15. The aerosol-generating device according to any preceding Example, wherein the control circuitry is configured to provide the second current to the resistive heating element such that the resistive heating element is heated to no more than 210°C.

[0468] Example Ex16. The aerosol-generating device according to any preceding Example, wherein the control circuitry is configured to provide the first current to the inductor element and the second current to the resistive heating element at different times.

[0469] Example Ex17. The aerosol-generating device according to any preceding Example, wherein the control circuitry is configured to provide the first current to the inductor element and the second current to the resistive heating element in an alternating sequence.

[0470] Example Ex18. The aerosol-generating device according to any preceding Example, wherein the control circuitry is configured to adjust an amplitude of the first current provided to the inductor element to maintain the temperature of the susceptor element at a susceptor target temperature or to follow a susceptor target temperature profile.

[0471] Example Ex19. The aerosol-generating device according to any preceding Example, wherein the control circuitry is configured to adjust an amplitude of the second current provided to the resistive heating element to maintain the temperature of the resistive heating element at the resistive heating target temperature or to follow the resistive heating target temperature profile.

[0472] Example Ex20. The aerosol-generating device according to any preceding Example, wherein the control circuitry is configured to prevent the supply of the second current to the resistive heating element when the first current is supplied to the inductor element.

[0473] Example Ex21. The aerosol-generating device according to any preceding Example, wherein the control circuitry is configured to prevent the supply of the first current to the inductor element when the second current is supplied to the resistive heating element.

[0474] Example Ex22. The aerosol-generating device according to any preceding Example, wherein control circuitry is configured to prevent simultaneous supply of the first current to the inductor element and the second current to the resistive heating element.

[0475] Example Ex23. The aerosol-generating device according to any preceding Example, wherein the control circuitry is configured to provide the first current to the inductor element during on periods, and prevent the first current from being provided to the inductor element during off periods.

[0476] Example Ex24. The aerosol-generating device according to Example Ex23, wherein the control circuitry is configured to provide the first current to the inductor element in one or more pulses during each of the on periods, and wherein the control circuitry is configured to adjust the pulses during each of the on periods to control the temperature of the susceptor element.

[0477] Example Ex25. The aerosol-generating device according to Example Ex24, wherein the pulses occupy a proportion of each of the on periods, and wherein the control circuitry is configured to adjust the proportion of each of the on periods occupied by the pulses to control the temperature of the susceptor element.

[0478] Example Ex26. The aerosol-generating device according to any one of Examples Ex23 to Ex25, wherein the control circuitry is configured to adjust the length of the on periods to maintain the temperature of the susceptor element at a susceptor target temperature or to follow a susceptor target temperature profile.

[0479] Example Ex27. The aerosol-generating device according to any one of Examples Ex23 to Ex26, wherein the control circuitry is configured to provide the second current to the resistive heating element during the off periods.

[0480] Example Ex28. The aerosol-generating device according to Example Ex27, wherein the control circuitry is configured to adjust the length of the off periods to maintain the temperature of the resistive heating element at a resistive heating target temperature or to follow a resistive heating target temperature profile.

[0481] Example Ex29. The aerosol-generating device according to Example Ex27 or Ex28, wherein the control circuitry is configured to provide the second current to the resistive heating element in one or more pulses during each of the off periods, and wherein the control circuitry is configured to adjust the pulses during each of the off periods to control the temperature of the susceptor element.

[0482] Example Ex30. The aerosol-generating device according to Example Ex29, wherein the pulses occupy a proportion of each of the off periods, and wherein the control circuitry is configured to adjust the proportion of each of the off periods occupied by the pulses to control the temperature of the susceptor element.

[0483] Example Ex31. The aerosol-generating device according to Example Ex27 or Ex28, wherein the control circuitry is configured to provide the second current to the resistive heating element during the off periods for reduced time periods shorter than each of the off periods.

[0484] Example Ex32. The aerosol-generating device according to Example Ex31 , wherein the control circuitry is configured to adjust the length of the reduced time periods to maintain the temperature of the resistive heating element at a resistive heating target temperature or to follow a resistive heating target temperature profile.

[0485] Example Ex33. The aerosol-generating device according to Example Ex31 , wherein the control circuitry is configured to adjust the length of time gaps between the reduced time periods and the on periods to maintain the temperature of the resistive heating element at a resistive heating target temperature or to follow a resistive heating target temperature profile.

[0486] Example Ex34. The aerosol-generating device according to any of Examples Ex1 to Ex19, wherein the control circuitry is configured to provide the first current to the inductor element and the second current to the resistive heating element simultaneously.

[0487] Example Ex35. The aerosol-generating device according to any preceding Example, wherein the inductor element surrounds the chamber.

[0488] Example Ex36. The aerosol-generating device according to any preceding Example, wherein the resistive heating element surrounds the chamber.

[0489] Example Ex37. The aerosol-generating device according to any preceding Example, wherein the resistive heating element is configured to heat a periphery of the chamber.

[0490] Example Ex38. The aerosol-generating device according to any preceding Example, wherein the resistive heating element is configured such that a total current induced in the resistive heating element by the alternating magnetic field is substantially zero.

[0491] Example Ex39. The aerosol-generating device according to any preceding Example, wherein the resistive heating element comprises at least one primary portion and at least one secondary portion.

[0492] Example Ex40. The aerosol-generating device according to Example Ex39, wherein the resistive heating element is configured such that a current induced in the at least one primary portion by the alternating magnetic field is approximately equal and opposite in direction to a current induced in the at least one secondary portion by the alternating magnetic field.

[0493] Example Ex41. The aerosol-generating device according to Example Ex39 or Ex40, wherein the at least one primary portion is arranged such that the second current flows in the at least one primary portion in a clockwise direction about the chamber when viewed from the first end of the chamber, and the at least one secondary portion is arranged such that the second current flows in the at least one secondary portion in an anti-clockwise direction about the chamber when viewed from the first end of the chamber, and wherein a cumulative length of the at least one primary portion is substantially equal to a cumulative length of the at least one secondary portion.

[0494] Example Ex42. The aerosol-generating device according to any one of Examples Ex39 to Ex41 , wherein the resistive heating element comprises exactly one primary portion and exactly one secondary portion.

[0495] Example Ex43. The aerosol-generating device according to Example Ex42, wherein the primary portion is integrally formed with the secondary portion.

[0496] Example Ex44. The aerosol-generating device according to any one of Examples Ex39 to Ex41 , wherein the resistive heating element is arranged in a serpentine shape, and is folded or curved to at least partially surround the chamber.

[0497] Example Ex45. The aerosol-generating device according to Example Ex44, wherein the resistive heating element comprises two filaments arranged in a serpentine shape such that the two filaments are arranged substantially parallel to each other and the resistive heating element comprises a plurality of alternating primary portions and secondary portions.

[0498] Example Ex46. The aerosol-generating device according to any preceding Example, wherein the inductor element is an inductor coil.

[0499] Example Ex47. The aerosol-generating device according to Example Ex45, wherein the inductor coil is a helical coil.

[0500] Example Ex48. The aerosol-generating device according to any preceding Example, wherein the resistive heating element is a resistive heating coil.

[0501] Example Ex49. The aerosol-generating device according to Example Ex48, wherein the resistive heating coil is a helical coil.

[0502] Example Ex50. The aerosol-generating device according to any preceding Example, wherein the inductor element is an inductor coil, and the resistive heating element is a resistive heating coil.

[0503] Example Ex51. The aerosol-generating device according to Example Ex50, wherein the resistive heating coil and the inductor coil are co-wound.

[0504] Example Ex52. The aerosol-generating device according to Example Ex50 or Ex51 , wherein the resistive heating coil is wound about a winding axis, and the inductor coil is wound about the same winding axis.

[0505] Example Ex53. The aerosol-generating device according to any preceding Example, wherein the aerosol-generating device further comprises a jacket, the jacket defining the chamber. Example Ex54. The aerosol-generating device according to Example Ex53 when dependent on Ex48, wherein the resistive heating coil is wound around an outer surface of the jacket.

[0506] Example Ex55. The aerosol-generating device according to Example Ex53 or Ex54 when dependent on Ex46, wherein the inductor coil is wound around the outer surface the jacket.

[0507] Example Ex56. The aerosol-generating device according to any one of Examples Ex53 to Ex55, wherein the jacket is a thermally conductive jacket.

[0508] Example Ex57. The aerosol-generating device according to any one of Examples Ex53 to Ex56, wherein the thermal conductivity of the thermally conductive jacket is at least 20 Wm’1K’1, preferably at least 30 Wm’1K’1, preferably still at least 40 Wm’1K’ 1, and even more preferably approximately 80 Wm’1K’1.

[0509] Example Ex58. The aerosol-generating device according to any one of Examples Ex53 to Ex57, wherein the jacket comprises a ceramic.

[0510] Example Ex59. The aerosol-generating device according to Example Ex58, wherein the ceramic is alumina or aluminium nitrate.

[0511] Example Ex60. The aerosol-generating device according to any one of Examples Ex53 to Ex59, wherein the jacket comprises a circular cross section.

[0512] Example Ex61 . The aerosol-generating device according to any one of Examples Ex53 to Ex60, wherein the jacket comprises a substantially cylindrical shape.

[0513] Example Ex62. The aerosol-generating device according to any one of Examples Ex53 to Ex61 , wherein the jacket comprises a longitudinal axis.

[0514] Example Ex63. The aerosol-generating device according to Example Ex62, wherein the jacket comprises an inner surface, the inner surface defining the chamber.

[0515] Example Ex64. The aerosol-generating device according to Example Ex63, wherein the jacket comprises at least one groove defined on an inner surface of the jacket.

[0516] Example Ex65. The aerosol-generating device according to Example Ex64, wherein the at least one groove extends parallel to the longitudinal axis.

[0517] Example Ex66. The aerosol-generating device according to any one of Examples Ex53 to Ex65 when dependent on Example Ex48, wherein the resistive heating coil is wound around a winding axis coincident with the longitudinal axis of the jacket.

[0518] Example Ex67. The aerosol-generating device according to any one of Examples Ex53 to Ex66 when dependent on Example Ex46, wherein the inductor coil is wound around the winding axis coincident with the longitudinal axis of the jacket.

[0519] Example Ex68. The aerosol-generating device according to any preceding Example, wherein the aerosol-generating device further comprises a housing, the housing at least partially surrounding the chamber. Example Ex69. The aerosol-generating device according to Example Ex68 when dependent on Ex48, wherein the jacket is received in the housing.

[0520] Example Ex70. The aerosol-generating device according to Example Ex69, wherein the inductor element is disposed within the housing, such that the inductor element at least partially surrounds the jacket and the resistive heating element.

[0521] Example Ex71. The aerosol-generating device according to any preceding Example, wherein the inductor element extends between a first end and a second end.

[0522] Example Ex72. The aerosol-generating device according to Example Ex71 , wherein an electrical resistance between the first end and the second end of the inductor element is less than 250 milliohms, and preferably less than 150 milliohms, and preferably still approximately 100 milliohms.

[0523] Example Ex73. The aerosol-generating device according to any preceding Example, wherein the resistive heating element extends between a first end and a second end.

[0524] Example Ex74. The aerosol-generating device according to Example Ex73, wherein an electrical resistance between the first end and the second end of the resistive heating element is between 100 milliohms and 2000 milliohms, and preferably between 150 milliohms and 1500 milliohms, and preferably still between 200 milliohms and 1000 milliohms.

[0525] Example Ex75. The aerosol-generating device according to any preceding Example, wherein the electrical resistance of the resistive heating element is greater than the electrical resistance of the inductor element.

[0526] Example Ex76. The aerosol-generating device according to Example Ex75, wherein the electrical resistance of the resistive heating element is at least 2 times greater than the electrical resistance of the inductor element.

[0527] Example Ex77. The aerosol-generating device according to any preceding Example, wherein the inductor element comprises a first filament, the first filament comprising a first cross sectional area.

[0528] Example Ex78. The aerosol-generating device according to Example Ex77, wherein the first cross sectional area is defined in a first plane.

[0529] Example Ex79. The aerosol-generating device according to Example Ex77 or Ex78, wherein the first cross sectional area is perpendicular to the direction of extension of the first filament.

[0530] Example Ex80. The aerosol-generating device according to any one of Examples Ex77 to Ex79, wherein the first cross sectional area is perpendicular to the direction of extension of the first filament between the first end and the second end of the inductor element. Example Ex81 . The aerosol-generating device according to any one of Examples Ex77 to Ex80, wherein the first cross sectional area is substantially constant between the first end and the second end of the inductor element.

[0531] Example Ex82. The aerosol-generating device according to any one of Examples Ex77 to Ex81 , wherein the first cross sectional area is perpendicular to the direction of flow of the first current.

[0532] Example Ex83. The aerosol-generating device according to any one of Examples Ex77 to Ex82, wherein the first cross sectional area is substantially rectangular in shape.

[0533] Example Ex84. The aerosol-generating device according to any one of Examples Ex77 to Ex83, wherein the first cross sectional area has a first width and a first thickness, wherein the first width is greater than the first thickness.

[0534] Example Ex85. The aerosol-generating device according to Example Ex84, wherein the first width is at least 15 times greater than the first thickness.

[0535] Example Ex86. The aerosol-generating device according to Example Ex84 or Ex85, wherein the first width is between 1 millimetre and 3 millimetres.

[0536] Example Ex87. The aerosol-generating device according to any one of Examples Ex84 to Ex86, wherein the first thickness is between 0.05 millimetres and 0.2 millimetres.

[0537] Example Ex88. The aerosol-generating device according to any one of Examples Ex84 to Ex87 when dependent on Example Ex62, wherein the first width is parallel to the longitudinal axis of the jacket.

[0538] Example Ex89. The aerosol-generating device according to any one of Examples Ex84 to Ex88 when dependent on Example Ex67, wherein the first width is parallel to the winding axis of the inductor coil.

[0539] Example Ex90. The aerosol-generating device according to any one of Examples Ex84 to Ex89 when dependent on Example Ex62, wherein the first thickness is perpendicular to the longitudinal axis of the jacket.

[0540] Example Ex91 . The aerosol-generating device according to any one of Examples Ex84 to Ex90 when dependent on Example Ex67, wherein the first thickness is perpendicular to the winding axis of the inductor coil.

[0541] Example Ex92. The aerosol-generating device according to any preceding Example, wherein the resistive heating element comprises a second filament, the second filament comprising a second cross sectional area.

[0542] Example Ex93. The aerosol-generating device according to Example Ex92, wherein the second cross sectional area is defined in the first plane. Example Ex94. The aerosol-generating device according to Example Ex92 or Ex93, wherein the second cross sectional area is perpendicular to the direction of extension of the second filament.

[0543] Example Ex95. The aerosol-generating device according to any one of Examples Ex92 to Ex94, wherein the second cross sectional area is perpendicular to the direction of extension of the second filament between the first end and the second end of the resistive heating element.

[0544] Example Ex96. The aerosol-generating device according to any one of Examples Ex92 to Ex95, wherein the second cross sectional area is substantially constant between the first end and the second end of the resistive heating element.

[0545] Example Ex97. The aerosol-generating device according to any one of Examples Ex92 to Ex96, wherein the second cross sectional area is perpendicular to the direction of flow of the second current.

[0546] Example Ex98. The aerosol-generating device according to any one of Examples Ex92 to Ex97, wherein the second cross sectional area is substantially rectangular in shape.

[0547] Example Ex99. The aerosol-generating device according to any preceding Example, wherein the inductor element comprises metal, and preferably comprises copper.

[0548] Example Ex100. The aerosol-generating device according to any preceding Example, wherein the inductor element consists of copper.

[0549] Example Ex101. The aerosol-generating device according to any preceding Example, wherein the resistive heating element comprises metal, and preferably comprises stainless steel.

[0550] Example Ex102. The aerosol-generating device according to any preceding Example, wherein the resistive heating element consists of stainless steel.

[0551] Example Ex103. The aerosol-generating device according to any preceding Example, wherein the inductor element comprises a different material to the resistive heating element.

[0552] Example Ex104. The aerosol-generating device according to any preceding Example, wherein the inductor element consists of a different material to the resistive heating element.

[0553] Example Ex105. An aerosol-generating device comprising: a chamber for receiving at least a portion of an aerosol-generating article; an inductor element disposed adjacent to the chamber or in the chamber; and a resistive heating element disposed adjacent to the chamber or in the chamber; wherein the inductor element comprises a first filament comprising a first cross sectional area, the first cross sectional area defined in a first plane, wherein the resistive heating element comprises a second filament comprising a second cross sectional area, the second cross sectional area also defined in the first plane, and wherein the first cross sectional area is greater than the second cross sectional area.

[0554] Example Ex106. An aerosol-generating device comprising: a chamber for receiving at least a portion of an aerosol-generating article; an inductor element disposed adjacent to the chamber or in the chamber; and a resistive heating element disposed adjacent to the chamber or in the chamber; wherein the inductor element comprises copper, and wherein the resistive heating element comprises stainless steel.

[0555] Example Ex107. An aerosol-generating system comprising: an aerosol-generating device according to any preceding Example; and an aerosol-generating article comprising an aerosol-generating substrate, wherein the aerosol-generating article is received in the chamber of the aerosol-generating device.

[0556] Example Ex108. The aerosol-generating system according to Example Ex107, wherein the aerosol-generating article comprises one or more susceptors.

[0557] Example Ex109. The aerosol-generating system according to Example Ex107 or Ex108, wherein the aerosol-generating device comprises one or more susceptors.

[0558] Example Ex110. The aerosol-generating system according to Example Ex109, wherein the one or more susceptors are configured to be inserted into the aerosol-generating substrate when the aerosol-generating article is received in the chamber.

[0559] Example Ex111. The aerosol-generating system according to any one of Examples Ex107 to Ex110, wherein, in operation, the one or more susceptors are heated by the inductor element.

[0560] Example Ex112. The aerosol-generating system according to any one of Examples Ex107 to Ex111 , wherein the aerosol-generating substrate comprises tobacco material.

[0561] Example Ex113. The aerosol-generating system according to any one of Examples Ex107 to Ex112, wherein an airflow channel is defined between the aerosolgenerating article and a jacket, the airflow channel extending from a distal end of the jacket to a proximal end of the jacket. Example Ex114. The aerosol-generating system according to Example Ex113, wherein the airflow channel is defined between the aerosol-generating article and at least one groove.

[0562] Example Ex115. The aerosol-generating system according to Examples Ex113 or Ex114, wherein an airflow pathway is defined from a distal end of the jacket, through the airflow channel to a proximal end of the jacket, and from a proximal end of the aerosol-generating article, through the aerosol-generating article to a distal end of the aerosol-generating article.

[0563] Example Ex116. A method of controlling an aerosol-generating system to generate an aerosol, the system comprising: an aerosol-generating article comprising an aerosol-generating substrate, and an aerosol-generating device, the aerosol-generating device comprising a chamber for receiving at least a portion of an aerosol-generating article; the aerosol-generating device further comprising: an inductor element disposed adjacent to the chamber or in the chamber; a resistive heating element disposed adjacent to the chamber or in the chamber; at least one power supply for providing electrical power to the inductor element and resistive heating element; and control circuitry configured to control the supply of power from the at least one power supply to the inductor element and the resistive heating element, wherein the method comprises the steps of: providing a first current to the inductor element, such that the inductor element generates an alternating magnetic field within the chamber, and providing a second current to the resistive heating element to resistively heat the resistive heating element.

[0564] Example Ex117. The method according to Example Ex116, wherein the aerosolgenerating article comprises one or more susceptors.

[0565] Example Ex118. The method according to Example Ex116 or Ex117, wherein the aerosol-generating device comprises one or more susceptors.

[0566] Example Ex119. The method according to any one of Examples Ex116 to Ex118, wherein the one or more susceptors are configured to be inserted into the aerosolgenerating substrate when the aerosol-generating article is received in the chamber.

[0567] Example Ex120. The method according to any one of Examples Ex116 to Ex119, wherein providing the first current to the inductor element, such that the inductor element generates the alternating magnetic field within the chamber, comprises heating the one or more susceptors by the inductor element.

[0568] Example Ex121. The method according to any one of Examples Ex 116 to Ex120, wherein the method further comprises adjusting the first current provided to the inductor element to adjust an amount of heating provided by inductive heating.

[0569] Example Ex122. The method according to any one of Examples Ex116 to Ex121 , wherein the method further comprises adjusting the second current provided to the resistive heating element to adjust an amount of heating provided by resistive heating.

[0570] Example Ex123. The method according to any one of Examples Ex116 to Ex122, wherein the method further comprises adjusting an amplitude of the first current provided to the inductor element to maintain the temperature of the susceptor element at the susceptor target temperature or to follow the susceptor target temperature profile.

[0571] Example Ex124. The method according to any one of Examples Ex116 to Ex123, wherein the method further comprises adjusting an amplitude of the second current provided to the resistive heating element to maintain the temperature of the resistive heating element at the resistive heating target temperature or to follow the resistive heating target temperature profile.

[0572] Example Ex125. The method according to any one of Examples Ex116 to Ex124, wherein the method further comprises preventing the supply of the second current to the resistive heating element when the first current is supplied to the inductor element.

[0573] Example Ex126. The method according to any one of Examples Ex116 to Ex125, wherein the method further comprises preventing the supply of the first current to the inductor element when the second current is supplied to the resistive heating element.

[0574] Example Ex127. The method according to any one of Examples Ex116 to Ex126, wherein the method further comprises preventing simultaneous supply of the first current to the inductor element and the second current to the resistive heating element.

[0575] Example Ex128. The method according to any one of Examples Ex116 to Ex127, wherein the method further comprises providing the first current to the inductor element during on periods, and preventing the first current from being provided to the inductor element during off periods.

[0576] Example Ex129. The method according to Example Ex128, wherein the method further comprises adjusting the length of the on periods to maintain the temperature of the susceptor element at the susceptor target temperature or to follow the susceptor target temperature profile.

[0577] Example Ex130. The method according to Example Ex128 or Ex129, wherein the method further comprises providing the first current to the inductor element in one or more pulses during each of the on periods, and wherein the method further comprises adjusting the pulses during each of the on periods to control the temperature of the susceptor element.

[0578] Example Ex131. The method according to Example Ex130, wherein the pulses occupy a proportion of each of the on periods, and wherein the method further comprises adjusting the proportion of each of the on periods occupied by the pulses to control the temperature of the susceptor element.

[0579] Example Ex132. The method according to any one of Examples Ex128 to Ex131 , wherein the method further comprises providing the second current to the resistive heating element during the off periods.

[0580] Example Ex133. The method according to Example Ex132, wherein the method further comprises adjusting the length of the off periods to maintain the temperature of the resistive heating element at a resistive heating target temperature or to follow a resistive heating target temperature profile.

[0581] Example Ex134. The method according to Example Ex132 or Ex133, wherein the method further comprises providing the second current to the resistive heating element in one or more pulses during each of the off periods, and wherein the method further comprises adjusting the pulses during each of the off periods to control the temperature of the resistive heating element.

[0582] Example Ex135. The method according to Example Ex134, wherein the pulses occupy a proportion of each of the off periods, and wherein the method further comprises adjusting the proportion of each of the off periods occupied by the pulses to control the temperature of the resistive heating element.

[0583] Example Ex136. The method according to Example Ex132 or Ex133, wherein the method further comprises providing the second current to the resistive heating element during the off periods for reduced time periods shorter than the off periods.

[0584] Example Ex137. The method according to Example Ex136, wherein the method further comprises adjusting the length of the reduced time periods to maintain the temperature of the resistive heating element at a resistive heating target temperature or to follow a resistive heating target temperature profile.

[0585] Example Ex138. The method according to Example Ex136, wherein the method may comprises adjusting the length of time gaps between the reduced time periods and the on periods to maintain the temperature of the resistive heating element at a resistive heating target temperature or to follow a resistive heating target temperature profile.

[0586] Example Ex139. The method according to any one of Examples Ex116 to Ex124, wherein the method further comprises providing the first current to the inductor element and the second current to the resistive heating element simultaneously.

[0587] Example Ex140. The method according to any one of Examples Ex116 to Ex139, wherein the method further comprises, following activation of the device, initially providing the first current to the inductor element, and subsequently providing the second current to the resistive heating element.

[0588] Example Ex141. The method according to any one of Examples Ex116 to Ex139, wherein the method further comprises, following activation of the device, initially providing the second current to the resistive heating element, and subsequently providing the first current to the inductor element.

[0589] Example Ex142. The method according to any one of Examples Ex116 to Ex141 , wherein the method further comprises adjusting a frequency of the first current during operation of the device to adjust the amount of heat provided by inductive heating.

[0590] Example Ex143. The method according to any one of Examples Ex116 to Ex142, wherein the method further comprises adjusting the first current provided to the inductor element to maintain the temperature of a susceptor at a target temperature or to follow a target temperature profile.

[0591] Example Ex144. An aerosol-generating device comprising: a chamber for receiving at least a portion of an aerosol-generating article; an internal heater; an external heater; at least one power supply for providing electrical power to the internal heater and the external heater; and control circuitry configured to control the supply of power from the at least one power supply to the internal heater and the external heater, wherein the control circuitry is further configured to prevent the supply of power to one of the external heater or the internal heater when power is supplied to the other of the external heater or the internal heater.

[0592] Example Ex145. The aerosol-generating device according to Example Ex144, wherein the control circuitry is configured to prevent the supply of power to the external heater when power is supplied to the internal heater.

[0593] Example Ex146. The aerosol-generating device according to Example Ex144 or Ex145, wherein the control circuitry is configured to prevent the supply of power to the external heater when power is supplied to the internal heater. Example Ex147. The aerosol-generating device according to any one of Examples Ex144 to Ex146, wherein the internal heater is configured to heat the aerosolgenerating article from an internal location within the aerosol-generating article when at least a portion of the aerosol-generating article is received within the chamber.

[0594] Example Ex148. The aerosol-generating device according to any one of Examples Ex144 to Ex147, wherein the external heater is configured to heat the aerosolgenerating article from an external location outside of the aerosol-generating article when at least a portion of the aerosol-generating article is received within the chamber.

[0595] Example Ex149. The aerosol-generating device according to any one of Examples Ex144 to Ex148, wherein the control circuitry is configured to provide a first current to the internal heater, and wherein the control circuitry is configured to provide a second current to the external heater.

[0596] Example Ex150. The aerosol-generating device according to Example Ex149, wherein control circuitry is configured to provide the first current to the internal heater and the second current to the external heater at different times.

[0597] Example Ex151. The aerosol-generating device according to Example Ex149 or Ex150, wherein the control circuitry is configured to provide the first current to the internal heater and then subsequently the second current to the external heater.

[0598] Example Ex152. The aerosol-generating device according to any one of Examples Ex149 to Ex151 , wherein the control circuitry is configured to provide the first current to the internal heater for a first time period, and wherein the control circuitry is configured to provide the second current to the external heater for a second time period after the first time period.

[0599] Example Ex153. The aerosol-generating device according to Example Ex149 or Ex150, wherein the control circuitry is configured to provide the second current to the external heater and then subsequently the first current to the internal heater.

[0600] Example Ex154. The aerosol-generating device according to any one of Examples Ex149, Ex150 or Ex153, wherein the control circuitry is configured to provide the second current to the external heater for a first time period, and wherein the control circuitry is configured to provide the first current to the internal heater for a second time period after the first time period.

[0601] Example Ex155. The aerosol-generating device according to any one of Examples Ex149 to Ex154, wherein the control circuitry is configured to provide the first current to the internal heater and the second current to the external heater in an alternating sequence. Example Ex156. The aerosol-generating device according to any one of Examples Ex149 to Ex155, wherein the control circuitry is configured to provide the first current to the internal heater based on an internal heating feedback signal, and wherein the control circuitry is configured to provide the second current to the external heater based on an external heating feedback signal.

[0602] Example Ex157. The aerosol-generating device according to any one of Examples Ex149 to Ex156, wherein the internal heater comprises an inductor element and the external heater comprises a resistive heating element.

[0603] Example Ex158. The aerosol-generating device according to any one of Examples Ex149 to Ex156, wherein the internal heater comprises an internal resistive heating element and the external heater comprises an external resistive heating element.

[0604] Example Ex159. The aerosol-generating device according to any one of Examples Ex149 to Ex156, wherein the internal heater comprises an internal resistive heating element and the external heater comprises an external inductive heating element.

[0605] Example Ex160. An aerosol-generating system comprising: an aerosol-generating device according to any of Examples Ex144 to Ex159; and an aerosol-generating article comprising an aerosol-generating substrate, wherein the aerosol-generating article is received in the chamber of the aerosol-generating device.

[0606] Example Ex161. A method of controlling an aerosol-generating system to generate an aerosol, the system comprising: an aerosol-generating article comprising an aerosol-forming substrate, and an aerosol-generating device, the aerosol-generating device comprising a chamber for receiving at least a portion of an aerosol-generating article; the aerosol-generating device further comprising: an internal heater; an external heater; at least one power supply for providing electrical power to the internal heater and the external heater; and control circuitry configured to control the supply of power from the at least one power supply to the internal heater and the external heater, wherein the method comprises the steps of: providing electrical power to the internal heater, such that the internal heater heats the aerosol-forming substrate from an internal location within the aerosol-forming substrate, providing electrical power to the external heater, such that the external heater heats the aerosol-forming substrate from an external location outside of the aerosol-forming substrate, and preventing the supply of power to one of the external heater or the internal heater when power is supplied to the other of the external heater or the internal heater.

[0607] Example Ex162. The method according to Example Ex161 , wherein the method comprises preventing the supply of power to the external heater when power is supplied to the internal heater.

[0608] Example Ex163. The method according to Example Ex161 or Ex162, wherein the method comprises preventing the supply of power to the internal heater when power is supplied to the external heater.

[0609] Example Ex164. The method according to any one of Examples Ex161 to Ex 163, wherein providing electrical power to the internal heater comprises providing a first current to the internal heater, and wherein providing electrical power to the external heater comprises providing a second current to the external heater.

[0610] Example Ex165. The method according to Example Ex164, wherein the method further comprises providing the first current to the internal heater and the second current to the external heater at different times.

[0611] Example Ex166. The method according to Example Ex164 or Ex 165, wherein the method further comprises providing the first current to the internal heater and then subsequently the second current to the external heater.

[0612] Example Ex167. The method according to any one of Examples Ex164 to Ex 166, wherein the method further comprises providing the first current to the internal heater for a first time period, and wherein the method further comprises providing the second current to the external heater for a second time period after the first time period.

[0613] Example Ex168. The method according to Example Ex164 or Ex 165, wherein the method further comprises providing the second current to the external heater and then subsequently the first current to the internal heater.

[0614] Example Ex169. The method according to Example Ex164, Ex 165 or Ex168, wherein the method further comprises providing the second current to the external heater for a first time period, and wherein the method further comprises providing the first current to the internal heater for a second time period after the first time period.

[0615] Example Ex170. The method according to any one of Examples Ex164 to Ex 169, wherein the method further comprises providing the first current to the internal heater and the second current to the external heater in an alternating sequence.

[0616] Example Ex171. The method according to any one of Examples Ex164 to Ex 170, wherein the method further comprises providing the first current to the internal heater based on the internal heating feedback signal, and wherein the method further comprises providing the second current to the external heater based on the external heating feedback signal.

[0617] Example Ex172. The method according to any one of Examples Ex161 to Ex 171 , wherein the internal heater comprises an inductor element and the external heater comprises a resistive heating element.

[0618] Example Ex173. The method according to any one of Examples Ex161 to Ex 171 , wherein the internal heater comprises an internal resistive heating element and the external heater comprises an external resistive heating element.

[0619] Example Ex174. The method according to any one of Examples Ex161 to Ex 171 , wherein the internal heater comprises an internal resistive heating element and the external heater comprises an external inductive heating element.

[0620] The invention is further described, by way of example only, with reference to the accompanying drawings in which:

[0621] Figure 1 shows a side cross-sectional view of an aerosol-generating device according to a first embodiment;

[0622] Figure 2 shows an axial cross-sectional view of the aerosol-generating device of Figure 1 along line 1-1 ;

[0623] Figure 3 shows a perspective view of the heating assembly of the aerosol-generating device of Figures 1 and 2;

[0624] Figure 4 shows a side cross-sectional view of an aerosol-generating system comprising the aerosol-generating device of Figures 1 and 2;

[0625] Figure 5 shows a side cross-sectional view of an aerosol-generating device according to a second embodiment;

[0626] Figure 6 shows a side cross-sectional view of an aerosol-generating system comprising the aerosol-generating device of Figure 5;

[0627] Figure 7 shows a side cross-sectional view of an aerosol-generating device according to a third embodiment;

[0628] Figure 8 shows an axial cross-sectional view of the aerosol-generating device of Figure 7 along line 401-401 ;

[0629] Figure 9 shows a side cross-sectional view of an aerosol-generating device according to a fourth embodiment;

[0630] Figure 10 shows an axial cross-sectional view of the aerosol-generating device of Figure 9 along line 201-201 ;

[0631] Figure 11 shows a schematic of an inductor element from the aerosol-generating device of Figure 9; Figures 12A and 12B show a further arrangement of an inductor element and a coiled resistive heating element for use in an aerosol-generating device according to the present invention;

[0632] Figures 13A, 13B and 13C show a further arrangement of an inductor element and a serpentine resistive heating element for use in an aerosol-generating device according to the present invention;

[0633] Figures 13D and 13E show a further arrangement of a serpentine resistive heating element for use in an aerosol-generating device according to the present invention;

[0634] Figure 14 is a block diagram showing an inductive heating arrangement of the aerosol-generating devices described in relation to Figures 1 to 11 ;

[0635] Figure 15 is a schematic diagram showing inductive heating electrical circuitry of the aerosol-generating devices described in relation to Figures 1 to 11 ;

[0636] Figure 16 is a schematic diagram showing resistive heating electrical circuitry of the aerosol-generating devices described in relation to Figures 1 to 11 ;

[0637] Figure 17 illustrates the application of DC current to the resistive heating element over a first phase of operation and the application of AC current to the inductor element over a second phase of operation.

[0638] Figure 18 is a block diagram showing a further inductive heating arrangement of the aerosol-generating devices described in relation to Figures 1 to 11 ;

[0639] Figure 19 illustrates a scheme of switching voltages to control the DC current supplied to the resistive heating element and the AC current supplied to the inductor element;

[0640] Figure 20 illustrates the resultant DC current to the resistive heating element and AC current to the inductor element resulting from the switching voltages illustrated in Figure 19.

[0641] Figure 21 shows a side cross-sectional view of an aerosol-generating device according to an embodiment of the sixth aspect of the present disclosure;

[0642] Figure 22 shows an axial cross-sectional view of the aerosol-generating device of Figure 21 along line 1101-1101 ;

[0643] Figure 23 shows a side cross-sectional view of an aerosol-generating device according to a further embodiment of the sixth aspect of the present disclosure;

[0644] Figure 24 shows an axial cross-sectional view of the aerosol-generating device of Figure 23 along line 1201-1201 ;

[0645] Figure 25 is a block diagram showing a heating arrangement of the aerosolgenerating device described in relation to Figures 23 and 24;

[0646] Figure 26 illustrates a scheme of switching voltages to control the DC current supplied to the internal resistive heating element and the DC current supplied to the external resistive heating element; Figure 27 illustrates the resultant DC current supplied to the internal resistive heating element and the DC current supplied to the external resistive heating element resulting from the switching voltages illustrated in Figure 26.

[0647] Figures 1 and 2 show an aerosol-generating device 10 in accordance with a first embodiment. Figure 1 shows a side cross-sectional view of the aerosol-generating device 10. Figure 2 shows an axial cross-sectional view of the aerosol-generating device 10 of Figure 1 along line 1-1. The aerosol-generating device 10 comprises a housing 12 defining a chamber 16 for receiving a portion of an aerosol-generating article. The chamber 16 comprises an open end 18 through which an aerosol-generating article may be inserted into the chamber 16 and a closed end 20 opposite the open end 18. A cylindrical wall 22 of the chamber 16 extends between the open end 18 and the closed end 20.

[0648] The cylindrical wall 22 of the chamber 16 is at least partially defined by an inner surface of a jacket 60 which is received in the housing 12. The jacket is substantially cylindrical in shape and comprises a circular cross section. The jacket 60 is hollow, and is open at a distal end and a proximal end of the jacket 60. The jacket 60 preferably comprises a ceramic, preferably still alumina or aluminium nitrate. An inner surface of the jacket 60 defines a lumen 28 in which a portion of an aerosol-generating article is received when the aerosol-generating article is inserted into the chamber 16.

[0649] The aerosol-generating device 10 also comprises an inductor element 24. The inductor element 24 is formed of a helical coil comprising a plurality of windings 26 disposed adjacent to and surrounding the chamber 16. The aerosol-generating device 10 also comprises a resistive heating element 44. The resistive heating element 44 is also formed of a helical coil comprising a plurality of windings 46 disposed adjacent to and surrounding the chamber 16. The plurality of windings 26 of the inductor element 24 and the plurality of windings 46 of the resistive heating element 44 are positioned on an outer surface of the jacket 60. The jacket 60 is a thermally conductive heating jacket, such that when the resistive element 44 is heated, heat is transferred from the resistive element 44 to the inner surface of a heating jacket 60. Advantageously, direct contact between the jacket 60 and an aerosolgenerating article facilitates the transfer of heat from the jacket 60 to the aerosol-generating article.

[0650] The inductor element 24 and the resistive heating element 44 are wound on the outer surface of the jacket 60 helically about a central axis 36 of the aerosol-generating device 10. The central axis 36 of the aerosol-generating device 10 is coincident with a longitudinal axis of the jacket 60. Together, the jacket 60, the inductor element 24 and the resistive heating element 44 form a heating assembly. The heating assembly is shown in Figure 3. As shown in Figure 3, the inductor element 24 and the resistive heating element 44 are co-wound about each other. The jacket 60 further comprises a plurality of grooves or airflow channels 62 extending in a longitudinal direction along the inner surface of the jacket 60. The longitudinal direction is parallel to the central axis 36. Each airflow channel 62 is defined in the inner surface of the jacket 60, and extends in a straight line from a distal end of the jacket 60 to a proximal end of the jacket 60. Advantageously, the plurality of airflow channels 62 allow for air to flow from the distal end of the jacket 60 to a proximal end of the jacket 60 the portion of the aerosol-generating article is received by the lumen 28 when the aerosol-generating article is inserted into the chamber 16.

[0651] The housing 12 also defines a plurality of protrusions 38 extending into the chamber 16 from the closed end 20 of the chamber 16. As will be further described below, the plurality of protrusions 38 function to maintain a gap between an end of an aerosolgenerating article and the closed end 20 of the chamber 16 when the aerosol-generating article is fully inserted into the chamber 16. In the embodiment shown in Figures 1 and 2, the housing 12 defines three protrusions 38 spaced equidistantly about the central axis 36 of the aerosol-generating device 10. The skilled person will appreciate that the housing 12 may define more or fewer protrusions 38 and the arrangement of the protrusions 38 at the closed end 20 of the chamber 16 may be varied.

[0652] The aerosol-generating device 10 also comprises control circuitry 40 and a power supply 42 connected to the inductor element 24 and to the resistive heating element 44. The control circuitry 40 is configured to provide an alternating electric current from the power supply 42 to the inductor element 24 to generate an alternating magnetic field. The control circuitry 40 is also configured to provide a direct electric current from the power supply 42 to the resistive heating element 44 to generate heating in the resistive heating element 44 by Joule, or resistive, heating.

[0653] Figure 3 shows a perspective view of the heating assembly as described with respect to Figures 1 and 2. The jacket 60 is shown as translucent to display the plurality of airflow channels 62 extending from the distal end of the jacket 60 to the proximal end of the jacket 60.

[0654] The inductor element 24 is formed of a single filament, the single filament comprising copper. The inductor element 24 has a substantially rectangular cross section perpendicular to the direction of flow of alternating current through the inductor element 24. The rectangular cross section of the inductor element 24 is substantially constant in size and shape for substantially the entire length of the inductor element 24. In this embodiment, the cross section of the inductor element 24 has a width parallel to the central axis 36 and the longitudinal axis of the jacket 60. The width of the cross section of the inductor element 24 is between 1 millimetre and 3 millimetres. In this embodiment, the cross section of the inductor element 24 has a thickness perpendicular to the central axis 36 and the longitudinal axis of the jacket 60. The thickness of the cross section of the ...

Claims

Claims1 . An aerosol-generating device comprising: a chamber for receiving at least a portion of an aerosol-generating article; an inductor element at least partially surrounding the chamber; a resistive heating element at least partially surrounding the chamber; at least one power supply for providing electrical power to the inductor element and resistive heating element; and control circuitry configured to control the supply of power from the at least one power supply to the inductor element and the resistive heating element, wherein the control circuitry is configured to provide a first current to the inductor element, such that the inductor element generates an alternating magnetic field within the chamber for heating one or more susceptors within the aerosol-generating article when the aerosol-generating article is received in the chamber, wherein the control circuitry is configured to provide a second current to the resistive heating element for heating the chamber, and wherein the inductor element at least partially surrounds or is co-wound with the resistive heating element.

2. The aerosol-generating device according to claim 1 , wherein the first current is an alternating current.

3. The aerosol-generating device according to claim 1 or 2, wherein the second current is a direct current.

4. The aerosol-generating device according to any preceding claim, wherein the control circuitry is configured so that the inductor element is not supplied with the second current, and wherein the control circuitry is configured so that the resistive heating element is not supplied with the first current.

5. The aerosol-generating device according to any preceding claim, wherein the resistive heating element is configured to heat a periphery of the chamber.

6. The aerosol-generating device according to any preceding claim, wherein the aerosol-generating device further comprises a jacket, the jacket defining the chamber.

7. The aerosol-generating device according to claim 6, wherein the resistive heating element is positioned on an outer surface of the jacket.

8. The aerosol-generating device according to claim 6 or 7, wherein the resistive heating element is a resistive heating coil.

9. The aerosol-generating device according to claim 8, wherein the resistive heating coil is wound around the outer surface of the jacket.

10. The aerosol-generating device according to claim 8 or 9, wherein the inductor element is an inductor coil.

11. The aerosol-generating device according to claim 10, wherein the inductor coil is wound around the outer surface the jacket.

12. The aerosol-generating device according to claim 10, wherein the resistive heating coil and the inductor coil are co-wound.

13. The aerosol-generating device according to any one of claims 6 to 12, wherein the aerosol-generating device further comprises a housing, the housing at least partially surrounding the chamber, wherein the jacket is received in the housing, and wherein the inductor element is disposed within the housing, such that the inductor element at least partially surrounds the jacket and the resistive heating element.

14. The aerosol-generating device according to any one of claims 6 to 13, wherein the jacket comprises an electrically insulating material.

15. The aerosol-generating device according to any one of claims 6 to 14, wherein the jacket consists of an electrically insulating material.

16. The aerosol-generating device according to any one of claims 6 to 15, wherein the jacket comprises a material having a relative magnetic permeability at between 0.9 and 1.1 , preferably between 0.99 and 1.01.

17. The aerosol-generating device according to any one of claims 6 to 16, wherein the jacket comprises a material which is substantially transparent to the alternating magnetic field.

18. The aerosol-generating device according to any one of claims 6 to 17, wherein the jacket comprises a ceramic.

19. The aerosol-generating device according to any one of claims 6 to 18, wherein the jacket comprises alumina or alumina nitrate.

20. The aerosol-generating device according to any one of claims 6 to 19, wherein the jacket is a thermally conductive jacket and wherein the thermal conductivity of the thermally conductive jacket is at least 20 Wm’1K’1, preferably at least 30 Wm’1K’1, preferably still at least 40 Wm’1K’1, and even more preferably approximately 80 Wrrr 1K’1.

21. The aerosol-generating device according to any one of claims 6 to 20, wherein the jacket comprises an inner surface, the inner surface defining the chamber.

22. The aerosol-generating device according to claim 21 , wherein the jacket comprises at least one groove defined on an inner surface of the jacket.

23. The aerosol-generating device according to claim 22, wherein the at least one groove extends parallel to a longitudinal axis of the jacket.

24. The aerosol-generating device according to any preceding claim, wherein the inductor element comprises a first filament, the first filament comprising a first cross sectional area, wherein the first cross sectional area is perpendicular to the direction of flow of the first current, and wherein the first cross sectional area is substantially rectangular in shape, and wherein the resistive heating element comprises a second filament, the second filament comprising a second cross sectional area, wherein the second cross sectional area is perpendicular to the direction of flow of the second current, and wherein the second cross sectional area is substantially rectangular in shape.

25. The aerosol-generating device according to any preceding claim, wherein the control circuitry is configured to prevent the supply of the second current to the resistive heating element when the first current is supplied to the inductor element.

26. The aerosol-generating device according to any preceding claim, wherein the resistive heating element is configured such that a total current induced in the resistive heating element by the alternating magnetic field is substantially zero.

27. The aerosol-generating device according to any preceding claim, wherein the resistive heating element comprises at least one primary portion and at least one secondary portion, wherein the at least one primary portion is arranged such that the second current flows in the at least one primary portion in a clockwise direction about the chamber when viewed from the first end of the chamber, and the at least one secondary portion is arranged such that the second current flows in the at least one secondary portion in an anti-clockwise direction about the chamber when viewed from the first end of the chamber, and wherein a cumulative length of the at least one primary portion is substantially equal to a cumulative length of the at least one secondary portion.

28. The aerosol-generating device according to any preceding claim, wherein the aerosol-generating device comprises the one or more susceptors.

29. The aerosol-generating device according claim 28, wherein the one or more susceptors are configured to be inserted into an aerosol-generating substrate within the aerosol-generating article when the aerosol-generating article is received in the chamber.

30. The aerosol-generating device according claim 29, wherein the one or more susceptors are in the form of at least one blade or at least one pin.

31. The aerosol-generating device according to any one of claims 1 to 27, wherein the aerosol-forming article comprises the one or more susceptors.

32. An aerosol-generating system comprising: an aerosol-generating device according to any preceding claim; and an aerosol-generating article comprising an aerosol-generating substrate, wherein the aerosol-generating article is received in the chamber of the aerosol-generating device.

33. The aerosol-generating system according to claim 32, wherein the aerosol-forming article comprises the one or more susceptors.

34. The aerosol-generating system according to claim 32, wherein the aerosolgenerating device comprises one or more susceptors.

35. The aerosol-generating system according to claim 34, wherein the one or more susceptors are configured to be inserted into the aerosol-generating substrate when the aerosol-generating article is received in the chamber.

36. The aerosol-generating system according to any one of claims 32 to 35, wherein, in operation, the one or more susceptors are heated by the inductor element.

37. The aerosol-generating system according to any one of claims 32 to 36, wherein the aerosol-generating substrate comprises tobacco material.

38. The aerosol-generating system according to any one of claim 32 to 37, wherein an airflow channel is defined between the aerosol-generating article and a jacket, the airflow channel extending from a distal end of the jacket to a proximal end of the jacket.

39. The aerosol-generating system according to claim 38, wherein the airflow channel is defined between the aerosol-generating article and at least one groove.

40. The aerosol-generating system according to claim 39, wherein an airflow pathway is defined from a distal end of the jacket, through the airflow channel to a proximal end of the jacket, and from a proximal end of the aerosol-generating article, through the aerosol-generating article to a distal end of the aerosol-generating article.

41. A method of controlling an aerosol-generating system to generate an aerosol, the system comprising: an aerosol-generating article comprising an aerosol-generating substrate, and an aerosol-generating device, the aerosol-generating device comprising a chamber for receiving at least a portion of an aerosol-generating article; the aerosol-generating device further comprising: an inductor element at least partially surrounding the chamber; a resistive heating element at least partially surrounding the chamber;at least one power supply for providing electrical power to the inductor element and resistive heating element; control circuitry configured to control the supply of power from the at least one power supply to the inductor element and the resistive heating element, and wherein the inductor element at least partially surrounds or is co-wound with the resistive heating element, wherein the method comprises the steps of: providing a first current to the inductor element, such that the inductor element generates an alternating magnetic field within the chamber for heating one or more susceptors within the aerosol-generating article when the aerosol-generating article is received in the chamber, and providing a second current to the resistive heating element to resistively heat the resistive heating element.

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