Aerosol-generating device with power control

Abstract

An aerosol-generating device (12) comprising a cavity (41) configured to removably receive at least a portion of an aerosol-generating article. The aerosol-generating device (12) comprises an inductor (42) configured to generate an alternating magnetic field in the cavity (41) to heat a susceptor in an aerosol-generating article received in the cavity. The aerosol-generating device (12) comprises a power supply (44) for supplying power to the inductor (42) and power control electronics (43) configured to control the supply of power from the power supply (44) to the inductor (42) to generate an alternating magnetic field in the cavity. The power control electronics (43) are configured to operate in a puff mode. In the puff mode, the power control electronics (43) are configured to detect a puff when at least a portion of the aerosol-generating article is received in the cavity; supply power to the inductor during the puff, wherein the power control electronics (43) are configured to supply a first amount of power to the inductor (42); and, after a predetermined time interval during the puff, to supply a second amount of power to the inductor (42), wherein the second amount of power is less than the first amount of power.

Description

[0001] FTR3819 / PCT (P / 90042. W001)

[0002] 1

[0003] AEROSOL-GENERATING DEVICE WITH POWER CONTROL

[0004] The present invention relates to an aerosol-generating device and an aerosol-generating system comprising an aerosol-generating device. In particular, the invention relates to the control of the supply of power in the aerosol-generating device.

[0005] Some known aerosol-generating systems comprise an aerosol-generating device and an aerosol-generating article comprising an aerosol-forming substrate configured to be heated by the aerosol-generating device.

[0006] In some of these known systems, the aerosol-generating device comprises a power supply, such as a battery, power control electronics, and an inductor comprising an inductor coil, and the aerosol-generating article comprises a susceptor element. The inductor coil generates an alternating magnetic field when it is supplied with an alternating current, and the susceptor element is heated when it is arranged in the alternating magnetic field. The alternating magnetic field penetrates the susceptor element, heating the susceptor element, which in turn heats the aerosol-forming substrate in the aerosol-generating article, releasing volatile components which condense to form an aerosol, which is inhalable by a user.

[0007] Different types of aerosol-generating articles and aerosol-forming substrates are also known. Some known aerosol-generating system comprise an article holding a solid aerosol-forming substrate. Some known aerosol-generating systems comprise an article in the form of a cartridge holding a liquid aerosol-forming substrate. Therefore, it is known that different types of aerosol-forming substrate can require different heating arrangements and regimes to generate an optimal aerosol. For example, susceptor elements and inductors may have different sizes and different positionings within different aerosol-generating systems. Depending on the sizes and configurations of the inductor and susceptor elements, different quantities and qualities of aerosol production may be achieved. If an aerosolgenerating device is used interchangeably with different aerosol-generating articles and aerosolforming substrates, at least on of the aerosol-generating articles may not be sufficiently heated to generate a desirable aerosol because of the different heating arrangements. Increasing the level of power applied to the substrate may result in overheating the substrate, which may lead unintended and undesired burning of the substrate or generation of undesirable aerosol components.

[0008] It would be desirable to provide an aerosol-generating device that is configured to generate a desirable aerosol without overheating the substrate. It would be desirable to provide an aerosolgenerating device that is configured to be used with different types of aerosol-generating articles and aerosol-forming substrates. It would be desirable to provide an aerosol-generating device that is capable of generating an optimal aerosol from different types of aerosol-generating articles and aerosol-forming substrates.

[0009] According to the present disclosure there is provided an aerosol-generating device. The aerosol-generating device may comprise a cavity configured to removably receive at least a portion of an aerosol-generating article. The aerosol-generating article may comprise an aerosol-forming substrate for producing an aerosol. The aerosol-generating device may comprise an inductor configured to generate an alternating magnetic field in the cavity to heat a susceptor in an aerosol- generating article received in the cavity. The aerosol-generating device may comprise a power supply for supplying power to the inductor. The aerosol-generating device may comprise power control electronics configured to control the supply of power from the power supply to the inductor to generate an alternating magnetic field in the cavity. The power control electronics may be configured to operate in a puff mode, in which the power control electronics may be configured to detect a puff when at least a portion of the aerosol-generating article is received in the cavity. In the puff mode, the power control electronics may be configured to supply power to the inductor during the puff, wherein the power control electronics are configured to supply a first amount of power to the inductor. In the puff mode, the power control electronics may be configured to, after a predetermined time interval during the puff, supply a second amount of power to the inductor, wherein the second amount of power is less than the first amount of power.

[0010] Thus, the aerosol-generating device may be configured to supply a lower amount of power after a predetermined time interval during the puff. Advantageously, the aerosol-generating device may supply sufficient power to overcome the system inertia at the start of a puff, when the aerosolgenerating device, or aerosol-generating article, or an aerosol-generating system comprising the aerosol-generating device and article are cool. Advantageously, reducing the power supplied during the puff may avoid the aerosol-forming substrate from being overheated. Advantageously, reducing the power during a puff may prevent overheating of the susceptor and the aerosol-forming substrate. Overheating is undesirable because it can lead to the generation of undesirable aerosols forming which may have undesirable flavours, for example. Advantageously, the initial higher power allows the device to quickly heat the susceptor and therefore bring the susceptor to the desired temperature more quickly, to prevent a delay in aerosol being generated, which may be unsatisfactory for a user. Advantageously, the puff mode may allow the aerosol-generating device to accurately control when power is supplied to the inductor.

[0011] As used herein, the term “puff’ is used to describe the action of a user generating aerosol using an aerosol-generating device. The user may carry out this action by drawing air through the aerosol-generating system comprising the aerosol-generating device by inhalation. The user of the aerosol-generating system may draw on an air outlet of an airflow path through the aerosol-generating system to receive and inhale aerosol generated by the aerosol-generating system. The term “puff mode” may refer to a mode of operation of the aerosol-generating device in which the power control electronics are configured to detect a puff, and in response to a detected puff to supply power to the inductor. In other words, in the puff mode the device may be configured to heat an aerosol-generating article received in the cavity when a puff is detected.

[0012] The power control electronics may be configured to detect a start of the puff and supply the first amount of power in response to the start of the puff. The first amount of power may be a maximum power level supplied the inductor. For example, the greatest amount of power supplied to the inductor during the puff is preferably supplied at the start of the puff. Therefore, the first amount of power may be configured to heat the susceptor to reach a vaporisation temperature of the aerosol-forming substrate quickly. The power control electronics may be configured to detect an end of the puff, and in response stop the supply of power to the inductor. In the puff mode, the aerosol-generating device may be configured to only heat the inductor during a puff. In the puff mode, when no puff is detected the power control electronics may be configured to prevent supply of power to the inductor. Advantageously, this may prevent overheating of the aerosol-forming substrate, wasting power and wasting aerosol-forming substrate. The aerosol-generating device being configured to operate in the puff mode may be particularly suitable for aerosol-generating articles comprising a liquid aerosol-forming substrate.

[0013] Preferably, the power control electronics may be configured to discontinuously decrease supply of power from the first amount of power to the second amount of power. For example, the power control electronics may be configured to reduce the supply of power from the first amount of power to the second amount of power in a step-wise manner.

[0014] The power control electronics may be configured to decrease the supply of power using at least 2, at least 3 or at least 4 discontinuous decreases of power supplied between the first amount of power and the second amount of power.

[0015] The power control electronics may be configured to continuously decrease the supply of power to the inductor. The power control electronics may be configured to continuously decrease the supply of power from the first amount of power to the second amount of power. In other words, the power control electronics may be configured to decrease the amount of power supplied to the inductor as a gradual ramp down.

[0016] The second amount of power may be less than 90 percent of the first amount of power, for example less than 80 percent, less than 70 percent, less than 60 percent or less than 50 percent of the first amount of power.

[0017] Preferably, the first amount of power is supplied at a first duty cycle and the second amount of power is supplied at a second duty cycle, wherein the second duty cycle is lower than the first duty cycle. Advantageously, modifying the duty cycle between the first duty cycle and a second duty cycle may be a simple implementation for the power control electronics to vary the power supplied to the inductor.

[0018] The first duty cycle may be between 100 percent and 60 percent, preferably between 100 percent and 70 percent, preferably between 100 percent and 80 percent, most preferably between 100 percent and 90 percent.

[0019] The second duty cycle may be between 90 percent and 20 percent, preferably between 90 percent and 30 percent, preferably between 90 percent and 40 percent, most preferably between 90 percent and 50 percent. Optionally, the second duty cycle may be between 80 percent and 50 percent, preferably between 70 percent and 50 percent.

[0020] The duty cycle may be adjusted by altering the pulse width, or the frequency of the pulses or both.

[0021] The predetermined time interval may be 5000 milliseconds or less, for example 4000 milliseconds or less, for example 3000 milliseconds or less, for example 2000 milliseconds or less, for example 1000 milliseconds or less. The predetermined time interval may be at least 100 milliseconds, for example at least 200 milliseconds, for example at least 300 milliseconds, for example at least 400 milliseconds, for example at least 500 milliseconds, for example at least 1000 milliseconds. The predetermined time interval may be between 5000 milliseconds and 100 milliseconds, for example, between 3000 milliseconds and 200 milliseconds, for example between 2000 milliseconds and 300 milliseconds, for example between 2000 and 300 milliseconds. Preferably, the predetermined time interval between the first amount of power being supplied to the inductor and the second amount of power being supplied to the inductor is between 50 percent and 95 percent of a duration of the puff. The predetermined time internal may be about 60 percent, about 80 percent, about 85 percent, or about 90 percent of the duration of the puff. The power control electronics may be configured to detect the puff. The power control electronics may be configured to monitor an electrical quantity. The electrical quantity response to the supply of power to the inductor may be monitored. The power control electronics may be configured to detect whether the monitored electrical quantity meets a predetermined condition that indicates a puff, for example the start of a puff. The monitored electrical quantity may be a temperature of the susceptor. The monitored electrical quantity may be proportional or inversely proportional to a temperature of the susceptor. For example, a change in the monitored electrical quantity may indicate a change of the temperature of the susceptor. During a puff, when an at least a portion of the aerosol-generating article is received in the cavity, the air may be drawn across, through or past the susceptor. The air flowing across, through or past the susceptor may have a cooling effect on the susceptor. Therefore, the predetermined condition may indicate that the susceptor has cooled due to a puff. Advantageously, the aerosol-generating device may provide reliable puff sensing without delay. Advantageously, monitoring and controlling the supply of power based on when a puff is detected reduces the risk of overheating the susceptor and forming undesirable aerosols, for example aerosols having an undesirable flavour. This may be particularly useful for a device configured to receive more than one type of aerosol-generating article because different types of aerosol-generating article may have different properties and so may have a higher risk of overheating at least one of the types of aerosol-generating article. Advantageously, the device of the present disclosure may not require a separate, additional, component for puff detection, for example a physical additional puff sensor, such as a pressure sensor. The benefit of not requiring a physical additional puff sensor is that space is saved within the aerosol-generating device, which can reduce the size of the device such that it is more comfortable and convenient for a user to use. It may also reduce the cost of manufacturing the aerosol-generating device because a physical additional puff sensor may not be required.

[0022] The monitored electrical quantity may be any suitable electrical quantity. The predetermined condition may be a change in the monitored electrical quantity. The monitored electrical quantity may be dependent on an interaction between an alternating magnetic field generated in the cavity by the inductor and the susceptor. The monitored electrical quantity may be a quantity selected from the list consisting of; electrical conductance, apparent electrical conductance, electrical resistance, apparent electrical resistance, inductance, current, voltage, frequency, and phase. As used herein, the term "inductance" refers to the imaginary part of a complex impedance defined as the ratio of the supplied AC voltage to the measured AC current. Inductance, generally speaking, includes the property of an electric circuit to be susceptible to exterior electromagnetic influences. The property may be an equivalent resistance of an inductor. As used herein, the term "equivalent resistance" refers to the real part of a complex impedance defined as the ratio of the supplied AC voltage to the measured AC current. Accordingly, the "equivalent resistance" may also be denoted as the resistive load of the inductor.

[0023] Such electrical quantities may be monitored directly or determined in real time by monitoring other parameters and applying an appropriate calculation. As an example, apparent conductance of the inductor may be calculated by the formula o = l / V, where o is apparent conductance of the inductor, I is current delivered to the inductor, and V is voltage across the inductor. Thus, if power is delivered at constant voltage, the apparent conductance may be determined in real time by monitoring the current and applying the formula. Both current and voltage may be monitored, and monitored values of both of these parameters used to calculate the apparent conductance. Apparent resistance is the inverse of apparent conductance, and can be calculated using the formula p = V / l, where p is the apparent resistance. As used herein apparent conductance may also be referred to as electrical conductance. The predetermined condition may be the monitored electrical quantity reaching a predetermined value. The predetermined condition may be the monitored electrical quantity rising or falling by a predetermined amount over a predetermined period of time. The predetermined condition may be an increase in the electrical conductance of the susceptor. The predetermined condition may be an increase in the apparent electrical conductance of the susceptor of between 0.1 and 200 percent, for example between 0.5 percent and 150 percent, for example between 1 and 100 percent, for example between 2 and 50 percent. The predetermined condition may comprise an increase in the electrical conductance, for example an increase of 1 percent.

[0024] The power control electronics may comprise a puff sensor configured to detect the puff. The puff sensor may be any suitable sensor configured to detect a user taking a puff on the aerosolgenerating device. For example, the puff sensor may comprise at least one of an airflow sensor or a pressure sensor. Advantageously, the puff sensor may be used to detect the start of a puff. The puff sensor may be configured to detect the end of a puff.

[0025] The aerosol-generating device may comprise an air inlet, and air outlet and an airflow path defined between the air inlet and the air outlet. Preferably, the puff sensor may be situated in the airflow path.

[0026] The aerosol-generating device may be configured to be used with different types of aerosolgenerating article. The cavity may be configured to receive different types of aerosol-generating articles. The cavity may be configured to removably receive at least a portion of a first aerosolgenerating article, the first aerosol-generating article comprising a first susceptor element, and a first aerosol-forming substrate. The cavity may be configured to removably receive at least a portion of a second aerosol-generating article, separately from the first aerosol-generating article, the second aerosol-generating article comprising a second susceptor element, and a second aerosol-forming substrate, the second aerosol-forming substrate being different from the first aerosol-forming substrate. In other words, the cavity may be configured to receive, individually, not simultaneously, at least a portion of the first aerosol-generating article, and at least a portion of the second aerosolgenerating article. In other words, the cavity is not configured to receive both at least a portion of the first aerosol-generating article and at least a portion of the second aerosol-generating article at the same time.

[0027] Advantageously, the cavity being configured to removably receive both the first and second aerosol-generating articles means that the device is suitable for use with more than one type of aerosol-generating article. Advantageously, this gives a user flexibility to use different aerosolgenerating articles with the same aerosol-generating device.

[0028] The first aerosol-forming substrate may be a liquid aerosol-forming substrate. The second aerosol-forming substrate may be a solid aerosol-forming substrate.

[0029] The power control electronics may be configured to operate the device in a continuous mode. Preferably, in the continuous mode the power control electronics are configured to supply power to the inductor to generate an alternating magnetic field in the cavity. Preferably, in the continuous mode, the power control electronics are configured to supply power to the inductor independently of a puff being detected.

[0030] Preferably, in the continuous mode the power control electronics are configured to supply power to the inductor to continuously generate an alternating magnetic field in the cavity. Preferably, in the continuous mode the power control electronics are configured to supply power to the inductor to generate an alternating magnetic field in the cavity to continuously heat a susceptor of an aerosolgenerating article that is at least partially received in the cavity. Preferably, in the continuous mode the power control electronics are configured to supply power to the inductor to continuously heat the aerosol-forming substrate.

[0031] The strength of the alternating magnetic field generated in the continuous mode may remain constant. For example, in the continuous mode the power control electronics may be configured to supply power to the inductor with a constant duty cycle. The strength of the alternating magnetic field generated in the continuous mode may vary over time. Typically, the continuous heating mode may be most suitable for use with solid aerosol-forming substrates.

[0032] In the continuous mode, the power control electronics may be configured to continuously heat the second susceptor element to generate an aerosol from the second aerosol-forming substrate, when the second aerosol-generating article is received in the cavity.

[0033] Advantageously, the provision of the power control electronics being configured to operate the device in a continuous mode may allow the device to adequately heat an aerosol-forming substrate that requires sustained heating to form a desirable aerosol.

[0034] Preferably, the power control electronics are configured to operate the device in the puff mode and the continuous mode. Preferably, the power control electronics are configured to implement the puff mode or the continuous mode, in response to a user selection. For example, after inserting at least a portion of an aerosol-generating article into the cavity, a user may select operation in the continuous mode or the puff mode, and in response to the user selection, the power control electronics may be configured to implement the puff mode or continuous mode. The aerosol-generating device may comprise a switch actuatable by a user to select the puff mode or the continuous mode. The user may actuate the switch to select the puff mode or the continuous mode and in response to the user selection, the power control electronics may be configured to implement the puff mode or the continuous mode.

[0035] Advantageously, this may allow the user to control the mode in which the device operates thereby controlling their usage of the device.

[0036] The power control electronics may be configured to determine whether an aerosol-generating article is received in the cavity. The power control electronics may be configured to identify an aerosolgenerating article received in the cavity.

[0037] The power control electronics may be configured to determine whether an aerosol-generating article is received in the cavity in an article detection mode. The power control electronics may be configured to identify an aerosol-generating article received in the cavity in an article detection mode. The article detection mode may be triggered or engaged when the aerosol-generating device is turned on by a user. In some embodiments, the article detection mode may be triggered or engaged when the aerosol-generating device is extracted from a power charging unit. In some of these embodiments, the aerosol-generating device may be configured to detect the extraction of the device from a power charging unit.

[0038] The power control electronics may be configured to supply power to the inductor in probing pulses, and determine from the probing pulses at least one property of the inductor that changes when a susceptor of an aerosol-generating article is received in the cavity. The power control electronics may be configured to supply power to the inductor in probing pulses when the power control electronics are in the article detection mode.

[0039] In some embodiments, the power control electronics are configured to determine when at least a portion the first aerosol-generating article comprising the first susceptor and the first aerosol-forming substrate is received in the cavity based on the determined property of the inductor. When it is determined that the first aerosol-generating article is received in the cavity, the power control electronics may be configured to operate the device in the puff mode. In the puff mode the power control electronics may be configured to supply power to the inductor to generate an alternating magnetic field in the cavity to heat the first susceptor element to generate an aerosol from the first aerosol-forming substrate.

[0040] In some embodiments, the power control electronics are configured to determine when at least a portion the second aerosol-generating article having the second susceptor and the second aerosolforming substrate is received in the cavity based on the determined property of the inductor. When it is determined that the second aerosol-generating article is received in the cavity, the power control electronics may be configured to operate the device in the continuous mode. In the continuous mode the power control electronics may be configured to supply power to the inductor to generate an alternating magnetic field in the cavity to heat the second susceptor element to generate an aerosol from the second aerosol-forming substrate. Advantageously, determining the type of aerosol-generating article received in the cavity, and controlling the aerosol-generating device based on the detected type of aerosol-generating article, enables the aerosol-generating device to optimise the experience for a user of the aerosol-generating device based on the type of aerosol-generating article that is used with the aerosol-generating device. Such operation also enables the aerosol-generating device to automatically provide the appropriate operating regime, such as continuous heating and puff-on-demand, for the type of aerosol-generating article that is received in the cavity, ensuring that a user does not accidentally select the incorrect regime and ultimately generate a suboptimal aerosol.

[0041] The power control electronics are configured to control the supply of power to the inductor. The power control electronics may be configured to control the supply of power to the inductor by controlling the supply of an alternating current to the inductor. The alternating current supplied to the inductor coil may have a frequency of between about 100 kilohertz (kHz), and about 30 megahertz (MHz) ), or between 1 megahertz (MHz) and 20 megahertz (MHz), or greater than 5 megahertz (MHz), or between 5 megahertz (5 MHz) and 15 megahertz (15 MHz) or around 6.78 megahertz (MHz).

[0042] In some preferred embodiments, the power control electronics comprise a controller. The controller may comprise a microprocessor, which may be a programmable microprocessor, a microcontroller, or an application specific integrated chip (ASIC) or other electronic circuitry capable of providing control.

[0043] The power control electronics may be configured to supply an alternating current to the inductor continuously following activation of the aerosol-generating system. The power control electronics may be configured to supply current to the inductor intermittently, such as on a puff by puff basis.

[0044] The power control electronics may comprise further electronic components. The power control electronics may comprise a DC / AC inverter, which may comprise a Class-D or Class-E power amplifier.

[0045] The aerosol-generating device may comprise a DC power supply. The DC power supply may comprise at least one of a battery and a capacitor. The DC power supply may be a battery. The battery may be any suitable type of battery. The battery may be a Lithium based battery, for example a Lithium-Cobalt, a Lithium-lron-Phosphate, a Lithium Titanate, or a Lithium-Polymer battery. The battery may be a Nickel metal hydride battery or a Nickel cadmium battery. The DC power supply may be another form of charge storage device, such as a capacitor. In some embodiments, the DC power supply has a DC supply voltage in the range of about 2.5 Volts to about 4.5 Volts, and a DC supply current in the range of about 1 Amp to about 10 Amps (corresponding to a DC power supply in the range of about 2.5 Watts to about 45 Watts).

[0046] The DC power supply and the power control electronics may be configured to operate at high frequency. The DC power supply and the power control electronics may be configured to supply a high frequency oscillating current to the inductor. As used herein, the term “high frequency oscillating current” means an oscillating current having a frequency of between about 100 kilohertz and about 30 megahertz. The high frequency oscillating current may have a frequency of from about 1 megahertz to about 30 megahertz, preferably from about 1 megahertz to about 10 megahertz and more preferably from about 5 megahertz to about 8 megahertz.

[0047] The power control electronics may be configured to control the supply of power to the inductor in any suitable way. In some embodiments, the power control electronics are configured to control the supply of power to the inductor in pulses. Where the power control electronics are configured to control the supply of power to the inductor in pulses, the power control electronics may be configured to control the supply of power to the inductor by pulse width modulation.

[0048] The aerosol-generating device may be configured to generate an aerosol from an aerosolforming substrate, during a usage session.

[0049] As used herein, the term “usage session” may refer to a period in which a series of puffs are applied by a user to extract aerosol from an aerosol-forming substrate.

[0050] The power control electronics may be configured to detect one or more puffs taken during the usage session. For example, the power control electronics may be configured to detect a first puff and a second puff. For example, two puffs taken in series during a usage session.

[0051] The power control electronics may be configured to supply a different amount of power to the inductor during the first puff compared to the amount of power supplied to the inductor during the second puff. Advantageously, this may allow the amount of power suppled to the inductor during the usage session to vary depending on the number of puffs taken. Advantageously, this may allow a lower amount of power to be supplied when the device is already hot compared to the amount of power supplied at the start of the usage session when the device is cooler.

[0052] Preferably, the power control electronics are configured to supply a high first amount of power to the inductor during the first puff and supply a low first amount of power to the inductor during the second puff, wherein the low first amount of power is lower than the high first amount of power.

[0053] Preferably, the power control electronics may be configured to supply a high second amount of power to the inductor during the first puff, and supply a low second amount of power to the inductor during the second puff, wherein the low second amount of power is lower than the high second amount of power.

[0054] The inductor of the aerosol-generating device may comprise an inductor coil. The inductor may have any suitable configuration to generate an alternating magnetic field in the cavity. The inductor may be arranged in any suitable location to generate an alternating magnetic field in the cavity.

[0055] The inductor may be located in or around the cavity. The inductor may comprise an inductor coil that circumscribes the cavity.

[0056] The inductor may have any suitable form. The inductor may be a tubular inductor coil. The inductor may be a planar inductor coil. The inductor may be a flat inductor coil. Preferably, the inductor is a tubular coil that circumscribes the cavity.

[0057] The inductor coil may have any suitable number of turns. The inductor may be formed from any suitable material. The inductor may be formed from at least one of: silver, gold, aluminium, brass, zinc, iron, nickel, and alloys of thereof, and electrically conductive ceramics, such as yttrium-doped zirconia, indium tin oxide, and yttrium doped titanate.

[0058] According to the present disclosure there is provided an aerosol-generating system. The aerosol-generating system may comprise an aerosol-generating device as described in herein. The aerosol-generating system may comprise an aerosol-generating article as described in herein. The aerosol-generating article may comprise an aerosol-forming substrate for producing an aerosol. The aerosol-generating article may comprise a susceptor configured to heat the aerosol-forming substrate.

[0059] The aerosol-generating system may comprise a first aerosol-generating article. The first aerosol-generating article comprising a first susceptor and a first aerosol-forming substrate. The aerosol-generating system may comprise a second aerosol-generating article. The second aerosolgenerating article may comprise a second susceptor and a second aerosol-forming substrate. The second aerosol-generating article may be received separately from the first aerosol-generating article. Preferably, the second aerosol-forming substrate is different from the first aerosol-forming substrate.

[0060] The aerosol-generating system may be a handheld aerosol-generating system. The aerosolgenerating system may be a handheld aerosol-generating system configured to allow a user to draw on a mouthpiece end to draw an aerosol through the air outlet. The aerosol-generating system may have a size comparable to a conventional cigar or cigarette. The aerosol-generating system may have a total length between about 25 millimetres and about 150 millimetres. The aerosol-generating system may have an external width or diameter between about 5 millimetres and about 30 millimetres.

[0061] The aerosol-forming substrate may form one of a plurality of component parts of the aerosolgenerating article. In some embodiments, the aerosol-forming substrate alone may form the aerosolgenerating article.

[0062] The first aerosol-forming substrate is preferably different to the second aerosol-forming substrate. For example, the first aerosol-forming substrate may have a different composition, quantity, state or aerosol-former compared to the second aerosol-forming substrate. Preferably, the first aerosolforming substrate is a liquid aerosol-forming substrate. Preferably, the second aerosol-forming substrate is a solid aerosol-forming substrate. Any description of an aerosol-forming substrate may equally be applied to the first aerosol forming substrate, the second aerosol-forming substrate, or both the first and second aerosol-forming substrates.

[0063] The aerosol-forming substrate may take any suitable form. Preferably, the aerosol-forming substrate may be a solid aerosol-forming substrate. The aerosol-forming substrate may be a liquid aerosol-forming substrate. The aerosol-forming substrate may comprise both solid and liquid components. The aerosol-forming substrate may comprise a solid. The aerosol-forming substrate may comprise a liquid. The aerosol-forming substrate may comprise a gel. The aerosol-forming substrate may comprise any combination of two or more of a solid, a liquid and a gel.

[0064] The aerosol-forming substrate may comprise nicotine, a nicotine derivative, or a nicotine analogue. The aerosol-forming substrate may comprise one or more nicotine salts. The one or more nicotine salts may be selected from the list consisting of nicotine citrate, nicotine lactate, nicotine pyruvate, nicotine bitartrate, nicotine pectates, nicotine alginates, and nicotine salicylate.

[0065] The aerosol-forming substrate may comprise tobacco. Alternatively or in addition, the aerosolforming substrate may comprise a non-tobacco material or tobacco-substitute material containing aerosol-forming material.

[0066] Where the aerosol-forming substrate is a solid aerosol-forming substrate or comprises a solid aerosol-forming substrate, the solid aerosol-forming 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.

[0067] 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.

[0068] In some embodiments, the solid aerosol-forming substrate comprises homogenised tobacco material. As used herein, the term “homogenised tobacco material” refers to a material formed by agglomerating particulate tobacco.

[0069] The solid aerosol-forming substrate may comprise 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 aerosol-generating article.

[0070] The aerosol-forming substrate may comprise one or more botanicals, and / or one or more pharmaceutical agents.

[0071] Where the aerosol-forming substrate is a liquid aerosol-forming substrate or comprises a liquid aerosol-forming substrate, the liquid aerosol-forming substrate may comprise nicotine. The nicotine containing liquid aerosol-forming substrate may be a nicotine salt matrix. The liquid aerosol-forming substrate may comprise plant-based material. The liquid aerosol-forming substrate may comprise tobacco. The liquid aerosol-forming substrate may comprise a tobacco-containing material containing volatile tobacco flavour compounds, which are released from the aerosol-forming substrate upon heating. The liquid aerosol-forming substrate may comprise homogenised tobacco material. The liquid aerosol-forming substrate may comprise a non-tobacco-containing material. The liquid aerosol-forming substrate may comprise homogenised plant-based material.

[0072] Where the aerosol-forming substrate comprises a liquid or a gel, the liquid may be located inside a container, or cartridge, or porous body. Where the aerosol-forming substrate is a liquid aerosol-forming substrate, the aerosol-generating article comprising the liquid aerosol-forming substrate may comprise a liquid reservoir configured to hold the liquid aerosol-forming substrate.

[0073] Where the aerosol-forming substrate comprises a liquid or a gel, in some embodiments, the aerosol-generating article may comprise an absorbent carrier. The aerosol-forming substrate may be coated on or impregnated into the absorbent carrier. For example, the nicotine compound and the aerosol-former may be combined with water as a liquid formulation. The liquid formulation may, in some embodiments, further comprise a flavourant. Such a liquid formulation may then be absorbed by the absorbent carrier or coated onto the surface of the absorbent carrier. The absorbent carrier may be a sheet or tablet of cellulosic-based material onto which the nicotine compound and the aerosol former may be coated or absorbed. The absorbent carrier may be a metallic, polymer or vegetal foam having liquid retaining and capillary properties and onto which the liquid or gel aerosol-forming substrate is coated or absorbed.

[0074] The aerosol-forming substrate may comprise an aerosol former. As used herein, an “aerosol former” refers to any suitable known compound or mixture of compounds that, in use, facilitates formation of a dense and stable aerosol and that is substantially resistant to thermal degradation at the operating temperature of the aerosol-generating article. Suitable aerosol-formers are well known in the art and include, but are not limited to: polyhydric alcohols, such as 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 triethylene glycol, 1 ,3-butanediol and glycerine.

[0075] 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.

[0076] Preferably, the first aerosol-generating article comprises a first susceptor. Preferably, the second aerosol-generating article comprises a second susceptor. Preferably, the first susceptor is different to the second susceptor.

[0077] For example, the first susceptor may have a different form or be formed from a different material to the second susceptor. This may allow the most suitable susceptor to be selected for the aerosol-forming substrate of the aerosol-forming article.

[0078] The length of the second susceptor may be different from the length of the first susceptor. The width of the second susceptor may be different from the width of the first susceptor. The thickness of the second susceptor may be different from the thickness of the first susceptor.

[0079] The second susceptor may be formed from a different material than the first susceptor.

[0080] The second susceptor may have a different form or shape to the first susceptor. In some embodiments, the second susceptor is in the form of a strip, and the first susceptor is in the form of a mesh.

[0081] An electrical property of the second susceptor may be different to an electrical property of the first susceptor. A magnetic property of the second susceptor may be different to a magnetic property of the first susceptor. The electrical resistance of the second susceptor may be different to the electrical resistance of the first susceptor. The electrical resistance of the second susceptor at room temperature (i.e. at 20 degrees Celsius) may be different to the electrical resistance of the first susceptor at room temperature (i.e. at 20 degrees Celsius). The second susceptor may be arranged in the second aerosol-generating article such that when the second aerosol-generating article is received in the cavity of the aerosol-generating device, the second susceptor is arranged in the cavity at a different location to the location of the first susceptor in the cavity when the first aerosol-generating article is received in the cavity. The second susceptor may be arranged in the second aerosol-generating article such that when the second aerosolgenerating article is received in the cavity of the aerosol-generating device, the second susceptor is arranged in the cavity at a different orientation to the orientation of the first susceptor in the cavity when the first aerosol-generating article is received in the cavity.

[0082] Any description of the susceptor may equally be applied to the first susceptor, the second susceptor, or both the first and second susceptors. The susceptor of an aerosol-generating article may have any suitable form and be formed from any suitable material.

[0083] Preferably, the susceptor comprises an electrically conductive material. For example, the susceptor may comprise a metallic material. The metallic material may be, for example, one of aluminium, nickel, iron, or alloys thereof, forexample, carbon steel or ferritic stainless steel. Aluminium has an electrical resistivity of about 2.65 x 10'08Ohm-meter, measured at room temperature (20°C), and a magnetic permeability of about 1 .256 x 10'06Henry per meter. Likewise, ferritic stainless steel has an electrical resistivity of about 6.9 x 10'07Ohm-meter, measured at room temperature (20°C), and a magnetic permeability in a range of 1 .26 x 10'03Henry per meter to 2.26 x 10'03Henry per meter.

[0084] Preferably, the susceptor comprises a magnetic material that is heatable by penetration with a varying or alternating magnetic field. The magnetic material may be a ferromagnetic material, such as ferrite, ferritic iron, a ferromagnetic alloy, a ferromagnetic steel, or a ferromagnetic stainless steel such as SAE 400 series stainless steels, SAE type 409, 410, 420 or 430 stainless steels.

[0085] As used herein, “magnetic material” refers to a material which is able to interact with a magnetic field, including both paramagnetic and ferromagnetic materials.

[0086] In some preferred embodiments, the susceptor comprises at least about 5 percent, or at least about 20 percent, or at least about 50 percent, or at least about 90 percent of ferromagnetic or paramagnetic materials on a dry weight basis.

[0087] The susceptor may have any suitable form. The susceptor may be one of a particulate susceptor, or a susceptor filament, or a susceptor mesh, or a susceptor wick, or a susceptor pin, or a susceptor rod, or a susceptor blade, or a susceptor strip, or a susceptor sleeve, or a susceptor cup or a cylindrical susceptor, or a planar susceptor. For example, the susceptor may be an elongate susceptor strip having a length in a range of 8 millimetres to 16 millimetres, or 10 millimetres to 14 millimetres, or 12 millimetres. The susceptor strip may have a width in a range of 2 millimetres to 6 millimetres, or 4 millimetres 10 millimetres to 5 millimetres. The susceptor strip may have a thickness in a range of 0.03 millimetres to 0.15 millimetres, or 0.05 millimetres to 0.09 millimetres.

[0088] According to the present disclosure there is provided a method for controlling the supply of power to an aerosol-generating article, wherein at least a portion of the aerosol-generating article is removably received in a cavity of an aerosol-generating device. The method may comprise detecting a puff when at least a portion of the aerosol-generating article is received in the cavity. The method may comprise, during the puff, supplying first amount of power to the inductor; and after a predetermined time interval during the puff, supplying a second amount of power to the inductor, wherein the second amount of power is less than the first amount of power.

[0089] As used herein, “aerosol-generating system” refers to a system that interacts with an aerosolforming substrate to generate an aerosol. Preferably, the aerosol-generating system is a system that interacts with an aerosol-forming substrate to generate an inhalable aerosol that is directly inhalable into a user’s lungs thorough the user's mouth. As used herein, an aerosol-generating system comprises an aerosol-generating article and an aerosol-generating device

[0090] As used herein, “aerosol-forming substrate” refers to a substrate capable of releasing volatile compounds that can form an aerosol. Such volatile compounds may be released by heating the aerosol-forming substrate. In this disclosure, an aerosol-forming substrate refers to aerosol-forming substrates in any form, such as solid aerosol-forming substrates and liquid aerosol-forming substrates.

[0091] As used herein, “aerosol-generating article” refers to an article comprising an aerosol-forming substrate. An aerosol-generating article is typically configured for use with an aerosol-generating device, which cooperate to generate an aerosol from the aerosol-forming substrate. An aerosolgenerating article may be disposable.

[0092] The aerosol-generating article may be a cartridge. As used herein, “cartridge” refers to an article comprising an aerosol-forming substrate. A cartridge typically comprises a liquid aerosolforming substrate stored in a reservoir.

[0093] As used herein, “aerosol-generating device” refers to a device that is configured to interact with an aerosol-forming substrate or an aerosol-generating article comprising an aerosol-forming substrate to generate an aerosol. Typically, an aerosol-generating device is a portable device. Typically, an aerosol-generating device is a handheld device.

[0094] As used herein, “length” refers to the maximum dimension of a feature in a longitudinal direction of the feature.

[0095] As used herein, “width” or “diameter” refers to the maximum dimension of a feature in a transverse direction of the feature. The transverse direction is perpendicular to the longitudinal direction.

[0096] As used herein, “thickness” and “depth” refer to the maximum dimension of a feature in a direction perpendicular to the longitudinal direction of the feature and perpendicular to the transverse direction of the feature.

[0097] As used herein, the term “duty cycle” means the percentage of the ratio of pulse duration, or pulse width to the total period over which the pulses are supplied. For example, the “duty cycle” of pulses of electrical current is the percentage of the ratio of pulse duration, or pulse width to the total period over which the pulses of current are supplied

[0098] As used herein, “alternating current” refers to a current that periodically reverses direction. The alternating current may have any suitable frequency. Suitable frequencies for the alternating current may be between 100 kilohertz (kHz) and 30 megahertz (MHz). Where the at least one inductor coil is a tubular inductor coil, the alternating current may have a frequency of between 500 kilohertz (kHz) and 30 megahertz (MHz). Where the at least one inductor coil is a flat coil, the alternating current may have a frequency of be-tween 100 kilohertz (kHz), and 1 megahertz (MHz).

[0099] 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.

[0100] Ex1 . An aerosol-generating device comprising: a cavity configured to removably receive at least a portion of an aerosol-generating article; an inductor configured to generate an alternating magnetic field in the cavity to heat a susceptor in an aerosol-generating article received in the cavity; a power supply for supplying power to the inductor; and power control electronics configured to control the supply of power from the power supply to the inductor to generate an alternating magnetic field in the cavity, and wherein the power control electronics are configured to operate in an puff mode, in which the power control electronics are configured to: detect a puff when at least a portion of the aerosol-generating article is received in the cavity; supply power to the inductor during the puff, wherein the power control electronics are configured to supply a first amount of power to the inductor; and after a predetermined time interval during the puff, to supply a second amount of power to the inductor, wherein the second amount of power is less than the first amount of power.

[0101] Ex2. The aerosol-generating device according to example Ex1 , wherein the power control electronics are configured to detect a start of the puff and supply the first amount of power in response to the start of the puff.

[0102] Ex3. The aerosol-generating device according to example Ex1 or Ex2, wherein the first amount of power is a maximum power level supplied the inductor.

[0103] Ex4. The aerosol-generating device according to any one of examples Ex1 to Ex3, wherein the power control electronics are configured to detect an end of the puff, and in response stop the supply of power to the inductor.

[0104] Ex5. The aerosol-generating device according to any preceding example, wherein in the puff mode, when no puff is detected the power control electronics are configured to prevent supply of power to the inductor.

[0105] Ex6. The aerosol-generating device according to any preceding example, wherein the power control electronics are configured to discontinuously decrease supply of power from the first amount of power to the second amount of power.

[0106] Ex7. The aerosol-generating device according to any preceding example, wherein the power control electronics are configured to decrease the supply of power using at least 2, at least 3 or at least 4 stepwise decreases of power level between the first amount of power and the second amount of power. Ex8. The aerosol-generating device according to any one of examples Ex1 to Ex5, wherein the power control electronics are configured to continuously decrease the supply of power from the first amount of power to the second amount of power.

[0107] Ex9. The aerosol-generating device according to any preceding example, wherein the second amount of power is less than 80 percent, less than 70 percent, less than 60 percent or less than 50 percent of the first amount of power.

[0108] Ex10. The aerosol-generating device according to any preceding example, wherein the first amount of power corresponds to a first duty cycle and the second amount of power corresponds to a second duty cycle, wherein the second duty cycle is lower than the first duty cycle.

[0109] Ex11. The aerosol-generating device according to example Ex10, wherein the first duty cycle is between 100 percent and 60 percent, preferably between 95 percent and 70 percent, most preferably between 90 percent and 80 percent.

[0110] Ex12. The aerosol-generating device according to example Ex10 or Ex11 , wherein the second duty cycle is between 70 percent and 40 percent, preferably between 70 percent and 50 percent, most preferably between 60 percent and 50 percent.

[0111] Ex13. The aerosol-generating device according to any preceding example, wherein the time interval is between 5000 milliseconds and 200 milliseconds, for example, between 3000 milliseconds and 300 milliseconds, for example between 2000 milliseconds and 500 milliseconds.

[0112] Ex14. The aerosol-generating device according to any preceding example, wherein the power control electronics comprise a puff sensor configured to detect the puff, and optionally wherein the puff sensor comprises at least one of an airflow sensor and a pressure sensor.

[0113] Ex15. The aerosol-generating device according to any preceding example, wherein the power control electronics are configured detect a first puff and a second puff after the first puff, and wherein the power control electronics are configured to supply a high first amount of power to the inductor during the first puff; and supply a low first amount of power to the inductor during the second puff; wherein the low first amount of power is less than the high first amount of power.

[0114] Ex16. The aerosol-generating device according to example Ex15, wherein the power control electronics are configured to supply a high second amount of power to the inductor during the first puff; and supply a low second amount of power to the inductor during the second puff; wherein the low second amount of power is less than the high second amount of power.

[0115] Ex17. The aerosol-generating device according to any preceding example, wherein the cavity is configured to: removably receive at least a portion of a first aerosol-generating article, the first aerosolgenerating article comprising a first susceptor element, and a first aerosol-forming substrate; and removably receive at least a portion of a second aerosol-generating article, separately from the first aerosol-generating article, the second aerosol-generating article comprising a second susceptor element, and a second aerosol-forming substrate, the second aerosol-forming substrate being different from the first aerosol-forming substrate. Ex18. The aerosol-generating device according to any preceding example, wherein: in the puff mode the power control electronics are configured to supply power to the inductor to generate an alternating magnetic field in the cavity to heat the first susceptor element to generate an aerosol from the first aerosol-forming substrate; and the power control electronics are configured to operate the device in a continuous mode, in the continuous mode the power control electronics are configured to supply power to the inductor to generate an alternating magnetic field in the cavity to continuously heat the second susceptor element to generate an aerosol from the second aerosol-forming substrate, when the second aerosolgenerating article is received in the cavity.

[0116] Ex19. An aerosol-generating system comprising: an aerosol-generating device according to any one of examples Ex1 to Ex18; a first aerosol-generating article, the first aerosol-generating article comprising a first susceptor, and a first aerosol-forming substrate; and a second aerosol-generating article, the second aerosol-generating article comprising a second aerosol-forming substrate, separately from the first aerosol-generating article, the second aerosol-generating article comprising a second susceptor and a second aerosol-forming substrate, the second aerosol-forming substrate being different from the first aerosol-forming substrate.

[0117] Ex20. The aerosol-generating system according to example Ex19, wherein the first aerosol-forming substrate is a liquid aerosol-forming substrate.

[0118] Ex21. The aerosol-generating system according to example Ex19 or Ex20, wherein the second aerosol-forming substrate is a solid aerosol-forming substrate.

[0119] Ex22. A method for controlling the supply of power to an aerosol-generating article, wherein at least a portion of the aerosol-generating article is removably received in a cavity of an aerosol-generating device, the method comprising: detecting a puff when at least a portion of the aerosol-generating article is received in the cavity; and during the puff, supplying first amount of power to the inductor; and after a predetermined time interval during the puff, supplying a second amount of power to the inductor, wherein the second amount of power is less than the first amount of power.

[0120] Examples will now be further described with reference to the figures in which:

[0121] Figure 1 shows a schematic illustration of a first aerosol-generating article for an aerosolgenerating system according to an embodiment of the disclosure;

[0122] Figure 2 shows a schematic illustration of a device of an aerosol-generating system according to an embodiment of the disclosure;

[0123] Figure 3 shows a schematic illustration of an aerosol-generating system according to an embodiment of the present disclosure, the aerosol-generating system comprising the aerosolgenerating article of Figure 1 , and the aerosol-generating device of Figure 2;

[0124] Figure 4 shows a schematic illustration of a second aerosol-generating article for an aerosolgenerating system according to an embodiment of the disclosure; Figure 5 shows a schematic illustration of the aerosol-generating system of Figure 3, the aerosol-generating system comprising the aerosol-generating article of Figure 4, and the aerosolgenerating device of Figure 2;

[0125] Figure 6 shows a circuit diagram of the aerosol-generating device of Figure 2; and

[0126] Figure 7 illustrates an example of a power profile, showing a duty cycle against time elapsed during use of the aerosol-generating system of Figure 3.

[0127] An example of an aerosol-generating system 10 according to the present disclosure is shown in Figures 1-5. The aerosol-generating system 10 comprises an aerosol-generating device 12, and two aerosol-generating articles, a first aerosol-generating article 14 comprising a first aerosol-forming substrate 26 and a first susceptor 31 , and a second aerosol-generating article 114, in the form of a cartridge, the second aerosol-generating article 114 comprising a second aerosol-forming substrate 126 and a second susceptor 131 .

[0128] Figure 1 shows a schematic illustration of the first aerosol-generating article 14 of the aerosolgenerating system 10. The first aerosol-generating article 14 is in the form of a cartridge. The cartridge 14 comprises a cartridge housing 16, which is substantially tubular, defining an inner passage 19.

[0129] The housing 16 defines a liquid reservoir 25 that is configured to hold the first aerosol-forming substrate 26. In this embodiment, the first aerosol-forming substrate comprises a liquid aerosolforming substrate of one of the types described above. The inner passage 19 extends centrally through the liquid reservoir 25 such that the liquid reservoir 25 is a substantially annular reservoir.

[0130] The cartridge 14 comprises a mouth end 20 and a connection end 21. At the mouth end 20, the cartridge 14 comprises an air outlet 22, in the form of an opening at one end of the inner passage 19, At the connection end 21 , the cartridge 14 comprises an air inlet 35, in the form of an opening at the opposite end of the inner passage 19 to the air outlet 22.

[0131] The cartridge 14 further comprises a heater assembly 30. The heater assembly 30 is generally in the form of a flat, planar sheet. The heater assembly 30 comprises a heating element 31 , in the form of the first susceptor 31 , and a wicking element 32 arranged in fluid communication with the first susceptor 31. In this embodiment, the first susceptor 31 comprises a sintered mesh formed from ferritic stainless steel filaments and austenitic stainless steel filaments. The wicking element 32 comprises a porous body of rayon filaments.

[0132] The heater assembly 30 is arranged to extend across the inner passage 19, with the first susceptor 31 arranged in the inner passage 19. The wicking element 32 extends outwardly beyond the first susceptor 31 at opposing ends, with each end extending through the housing 16 and into reservoir 25. In use, the first aerosol-forming substrate 26 held in the reservoir 25 comes into contact with the ends of the wicking element 32 of the heater assembly 30, and is drawn by capillary action through the wicking element 32 and onto the first susceptor 31 in the inner passage 19.

[0133] Figure 2 shows a schematic illustration of the aerosol-generating device 12 of the aerosolgenerating system 10. The aerosol-generating device 12 comprises a connection end 38 and a distal end opposite the connection end 38. The aerosol-generating device 12 comprises a device housing 40, which defines a cavity 41 at the connection end 38. The cavity 41 is open end at the connection end 38 of the aerosol-generating device 12, and is substantially at the opposite end.

[0134] The cavity 41 is configured to receive the connection end 21 of the first aerosol-generating article 14. The cavity 41 is also configured to receive a connection end 121 of the second aerosolgenerating article 114, which is described in more detail below with reference to Figures 4, and 5.

[0135] The aerosol-generating device 12 further comprises an inductor comprising an inductor coil 42. In this embodiment, the inductor coil 42 is a helical coil circumscribing a portion of the cavity 41 , and has a circular cross-section when viewed parallel to the longitudinal axis of the aerosol-generating device 12. In this embodiment, the inductor coil 42 is formed from litz wire. The litz wire comprises 2000 strands of copper wire, each individual wire having a circular cross-section with a diameter of 20 microns (pm), and being coated in an electrically insulating layer of polyurethane. The litz wire is a multi stage litz wire, in which bundles of the individual wires are twisted together in multiple stages. The litz wire has a four stage bundling construction. In a first bundling stage, sixteen of the individual copper wires are bundled or twisted together, in a second bundling stage, five of the first bundles are bundled ortwisted together, in a third bundling stage, five of the second bundles are bundled ortwisted together, and in a fourth bundling stage, five of the third bundles are bundled or twisted together to form the multi stage litz wire. The litz wire has a circular cross-section and a length of lay of about 16 millimetres (mm). It will be appreciated that alternatively, the inductor coil could be made with a copper wire having a round circular section.

[0136] In order to generate the required alternating magnetic field in the cavity 41 to heat a susceptor of an aerosol-generating article received in the cavity 41 , the inductor coil 42 is driven during use with a high frequency alternating current, typically at frequencies over 5 megahertz (MHz), and often at frequencies of around 6.78 megahertz (MHz). The inductor coil 42 is formed from a litz wire to reduce the high frequency losses that would arise due to the skin effect at such high frequencies in a single stranded wire of similar diameter. The relatively small diameter of the individual wires of the litz wire is required to avoid skin effect losses at the high operating frequencies, the relatively high number of wires is required to achieve a low resistance for the coil, and the relatively large number of bundling stages is required to keep the number of wires per stage low, to reduce skin effect losses in each bundle at the high operating frequencies.

[0137] The inductor coil 42 is arranged such that when the connection end 21 of the first aerosolgenerating article 14 is received in the cavity 41 of the aerosol-generating device 12, as shown in Figure 3, the inductor coil 42 is aligned with the susceptor 31 of the first aerosol-generating article 14.

[0138] The aerosol-generating device 12 further comprises power control electronics 43 and a DC power supply 44. The DC power supply 44 comprises a rechargeable lithium ion battery, which is rechargeable via an electrical connector (not shown) at a distal end of the aerosol-generating device 12, opposite the connection end 38. The power control electronics 43 comprise a controller (not shown) that is connected to the power supply 44, and to the inductor coil 42, such that the power control electronics 43 are able to control a supply of power to the inductor coil 42 from the DC power supply 44. The controller of the power control electronics 43, and the DC power supply 44 are configured to supply an alternating current to the inductor coil 42.

[0139] The controller of the power control electronics may be a microcontroller, preferably a programmable microcontroller. The controller is programmed to regulate the supply of power from the DC power supply 44 to the inductor 42 in order to control the temperature of the susceptor 31 .

[0140] In this embodiment, the first susceptor 31 , the inductor coil 42, and a portion of the power control electronics 43 together form an inductive heating arrangement 45 when the first susceptor 31 is received in the cavity 41 of the aerosol-generating device 12. In this embodiment, the inductor coil 42, and a portion of the power control electronics 43 together form the inductive heating arrangement 45 when the first susceptor 31 is not received in the cavity 41 of the aerosol-generating device 12. It will be appreciated that in other embodiments, the power control electronics may not form part of the inductive heating arrangement. In these embodiments, the inductive heating arrangement may comprise inductive heating electronics connected to the power control electronics. In these embodiments, the susceptor, the inductor coil, and the inductive heating electronics may form the inductive heating arrangement when the susceptor is received in the cavity of the aerosol-generating device, and the inductor coil, and the inductive heating electronics may form the inductive heating arrangement when the susceptor is not received in the cavity of the aerosol-generating device.

[0141] When an alternating current is supplied to the inductor coil 42, the inductor coil 42 generates an alternating magnetic field in the cavity 41. When the connection end 21 of the first aerosolgenerating article 14 is received in the cavity 41 of the aerosol-generating device 12, the alternating magnetic field generated by the inductor coil 42 is generated in the region of the first susceptor 31 , which is aligned with the inductor coil 42.

[0142] The aerosol-generating device 12 further comprises a flux concentrator 46, which partially surrounds the inductor coil 42 and is configured to attenuate the alternating magnetic field generated by the inductor coil 42 in the direction radially outwardly from the device. This may reduce interference between the alternating magnetic field and other nearby electronic devices and reduce the risk of the alternating magnetic field inductively heating nearby objects outside of the aerosol-generating system.

[0143] The power control electronics 43 are configured to control power supplied from the power supply 44 to the inductor coil 42 to generate an alternating magnetic field in the cavity 41 . The power supply electronics are configured to operate in a puff mode, wherein the power control electronics 43 are configured to detect a puff when at least a portion of the aerosol-generating article is received in the cavity 41 . In the puff mode, the power control electronics 43 are configured to supply power to the inductor coil 42 during the puff.

[0144] The power control electronics 43 are configured to supply a power to the inductor coil 42 and to monitor an electrical quantity response to the power. The power in this example may have a duty cycle of 30 percent or less and it is configured to heat the susceptor to a temperature of between 20 and 200 degrees Celsius. The power control electronics 43 are configured to detect whether the monitored electrical quantity meets a predetermined condition that indicates the start of a puff. In this example, the electrical quantity is apparent electrical conductance of the inductive heating arrangement 45. In this example, the predetermined condition is that the apparent electrical conductance increases by at least 1 percent. If the monitored electrical quantity meets this predetermined condition that indicates a puff, the power control electronics 43 are configured to supply a first amount of power to the inductor coil 42 and after a predetermined time interval during the puff, to supply a second amount of power to the inductor. The second amount of power is less than the first amount of power. The power control electronics 44 are configured to detect a start of the puff and supply the first amount of power in response to the start of the puff. The power control electronics 44 are also configured to detect an end of the puff, and in response stop the supply of power to the inductor coil 42.

[0145] Figure 3 shows the first aerosol-generating article 14 in use with the aerosol-generating device 12, with the connection end 21 of the first aerosol-generating article 14 received in the cavity 41 of the aerosol-generating device 12.

[0146] As shown in Figure 3, when the connection end 21 of the cartridge 14 is received in the cavity 41 , the inductor coil 42 is aligned with the heater assembly 30 of the first aerosol-generating article 14, such that the inductor coil 42 is aligned with the first susceptor 31 . When the connection end 21 of the cartridge 14 is received in the cavity 41 , the alternating magnetic field generated by the inductor coil 42 is generated in the region of the first susceptor 31 .

[0147] Also as shown in Figure 3, when the connection end 21 of the cartridge 14 is received in the device cavity 41 , an air inlet 48, and air gap 49 are defined between the first cartridge housing 18 and the device housing 38 to enable ambient air to be drawn into the aerosol-generating system 10. The air gap 49 extends the length of the connection end 21 of the cartridge 14 and the length of the device cavity 41 to the air inlet 35 of the cartridge 14.

[0148] An airflow path is defined through the aerosol-generating system 10 when the connection end 21 of the cartridge 14 is received in the cavity 41 . The airflow path comprises the air inlet 48, the air gap 49, the air inlet 35, the inner passage 19, and the air outlet 22.

[0149] A user may draw on the mouth end 20 of the cartridge 14 and draw ambient air into the aerosolgenerating system 10 at the air inlet 48, through the airflow path, and out of the aerosol-generating system 10 at the air outlet 22. Air drawn through the inner passage 19 over the cartridge 14 flows over the first susceptor 31 . In use, the connection end 21 of the cartridge 12 is inserted into the device cavity 41 of the device 12.

[0150] The power control electronics 43 determine that the cartridge 14 is received in the cavity 41 , as described in more detail below, and supply power from the DC power supply 44 to the inductive heating arrangement 45 in the puff mode.

[0151] When a user takes a puff on the mouth end 20 of the cartridge 14, air is drawn into the aerosolgenerating system 10 at the air inlet 48, through the air gap 49. The user’s puff is detected by the power control electronics 43 and the controller of the power control electronics 43 determines that a puff has been taken on the aerosol-generating system 10. In the puff mode when the first aerosol-generating article 14 is received in the cavity 41 , the power control electronics 43, on detecting the puff, supply power to the inductor during the puff by causing an alternating current from the power supply 44 to be supplied to the inductor coil 42, which generates an alternating magnetic field in the cavity 41 .

[0152] The first susceptor 31 of the cartridge 14 is penetrated by the alternating magnetic field and is heated by Joule heating through induction of eddy currents in the susceptor, and through hysteresis losses. On initial detection of the puff, the power control electronics 43 are configured to supply a first amount of power to the inductor. The first amount of power in this embodiment is maximum power that is supplied to the inductor coil 42, first amount of power has a duty cycle of 95 percent. After a predetermined time interval during the puff, of around 2000 milliseconds, the power control electronics 43 are configured to supply a second, lower, amount of power to the inductor, which has a duty cycle of around 50 percent. The power control electronics 43 may control the provision of power to the inductor coil 42 by adjusting the duty cycle of the switching transistor of a DC / AC inverter. For example, during heating, at the start of the puff the DC / AC inverter generates alternating current that supplies power to the inductor coil 42 with a duty cycle of about 95 percent, which heats the susceptor 31 . After a predetermined amount of time, for example 2000 milliseconds, the duty cycle of the switching transistor is reduced. For example, the duty cycle of the switching transistor may be reduced to about 50 percent to provide the second amount of power to the inductor coil 42 during the puff.

[0153] The heated first susceptor 31 heats liquid first aerosol-forming substrate 26 drawn from the reservoir 25 by the wicking element 32 to the first susceptor 31 , and the heated aerosol-forming substrate 26 releases volatile compounds as a vapour into the inner passage 19 of the cartridge 14. The vapour is entrained in airflow through the inner passage 19, cools as it is drawn along the inner passage 19, and condenses to form an aerosol. The aerosol is drawn out of the aerosol-generating system 10 at the air outlet 22, of the cartridge 14, where it is inhaled by the user.

[0154] The power control electronics 43 are configured to detect an end of the puff, and in response stop the supply of power to the inductor coil 42.

[0155] Figure 4 shows a schematic illustration of the second aerosol-generating article 114 of the aerosol-generating system 10.

[0156] The second aerosol-generating article 114 comprises a mouth end 120 and a connection end 121.

[0157] At the mouth end 120, the second aerosol-generating article 114 comprises a mouthpiece element 115, and a hollow tubular segment 117. The mouthpiece element 115 is arranged at a location immediately downstream of the hollow tubular segment 117, such that an upstream end of the mouthpiece element 115 abuts the downstream end of the hollow tubular segment 117.

[0158] The mouthpiece element 115 is provided in the form of a cylindrical plug of low-density cellulose acetate. The mouthpiece element 115 has a length of about 12 millimetres, and an external diameter of about 7.25 millimetres.

[0159] The hollow tubular segment 117 is provided in the form of a hollow cylindrical tube made of cellulose acetate. The hollow tubular segment 117 defines an internal cavity that is substantially empty, and so substantially unrestricted airflow is enabled along the internal cavity. The hollow tubular segment 17 has a length of about 8 millimetres, an external diameter of about 7.25 millimetres, and an internal diameter (DSTS) of about 3.25 millimetres. A thickness of a peripheral wall of the hollow tubular segment 17 is about 2 millimetres.

[0160] At the connection end 121 , the second aerosol-generating article 114 comprises a rod of the second aerosol-forming substrate 126. In this embodiment, the rod of the second aerosol-forming substrate 126 comprises a solid aerosol-forming substrate of one of the types described above. The rod of the second aerosol-forming substrate 126 has an external diameter of about 7.25 millimetres and a length of about 12 millimetres.

[0161] At the connection end 121 , the second aerosol-generating article 114 further comprises the second susceptor 131 , in the form of an elongate susceptor element within the rod of the second aerosol-forming substrate 126. The second susceptor 131 is provided in the form of a strip and has a length of about 10 millimetres, a thickness of about 60 micrometres, and a width of about 4 millimetres.

[0162] In more detail, the second susceptor 131 is arranged substantially longitudinally within the rod of the second aerosol-forming substrate 126, such as to be approximately parallel to the longitudinal direction of the rod of the second aerosol-forming substrate 126. The second susceptor 131 is positioned in a radially central position within the rod of the second aerosol-forming substrate 126 and extends effectively along the longitudinal axis of the rod. The second susceptor 131 extends substantially from an upstream end to a downstream end of the rod of the second aerosol-forming substrate 126. In effect, the second susceptor 131 has the same length as the rod of the second aerosol-forming substrate 126.

[0163] At the connection end 121 , the second aerosol-generating article 114 further comprises an upstream element 133 located immediately upstream of the rod of the second aerosol-forming substrate 126. The upstream element 133 is in longitudinal alignment with the rod of the second aerosol-forming substrate 126. A downstream end of the upstream element 133 abuts an upstream end of the rod of the second aerosol-forming substrate 126. This arrangement advantageously prevents the second susceptor 131 from being dislodged. Further, this arrangement ensures that the consumer cannot accidentally contact the second susceptor 131 after use, when it has been heated. The upstream element 133 is provided in the form of a cylindrical plug of cellulose acetate circumscribed by a stiff wrapper. The upstream element 133 has a length of about 5 millimetres. An upstream end 135 of the upstream element 133 is open to enable air to be drawn into the second aerosol-generating article 114 through the upstream end.

[0164] Figure 5 shows the second aerosol-generating article 114 in use with the aerosol-generating device 12, with the connection end 121 of the second aerosol-generating article 114 received in the cavity 41 of the aerosol-generating device 12.

[0165] The inductor coil 42 is arranged such that when the connection end 121 of the second aerosolgenerating article 114 is received in the cavity 41 of the aerosol-generating device 12, as shown in Figure 5, the inductor coil 42 is aligned with the second susceptor 131 of the second aerosolgenerating article 114. The inductor coil 42 has a similar length to the second susceptor 131 , such that the alternating magnetic field generated by the inductor coil 42 penetrates the length of the second susceptor 131 , when the second susceptor 131 is received in the cavity 41 . In contrast, the first susceptor 31 has a length that is about half the length of the second susceptor 131. Accordingly, the inductor coil 42 has a length that is larger than the length of the first susceptor 31 . The alternating magnetic field generated by the inductor coil 42 penetrates the length of the first susceptor 31 , although the efficiency of the coupling between the inductor coil 42 and the first susceptor 31 is less than that between the inductor coil 42 and the second susceptor 131 in the second aerosol-generating article 114, as more energy is dissipated in the inductor coil 42 when it is coupled with the first susceptor 31 compared to when it is coupled with the second susceptor 131. In order to ensure that the aerosol-generating system 10 operates with an acceptable efficiency (i.e. with minimal losses) when used with the first aerosolgenerating article 14, it is particularly advantageous to use a litz wire to form the inductor coil 42 in this system.

[0166] Although in this embodiment the first susceptor 31 has a length that is about half the length of the second susceptor 131 , it will be appreciated that in other embodiments the first susceptor may have a length that is less than half the length of the second susceptor, or a length that is greater than half the length of the second susceptor. For example, the first susceptor may have a length that is a third the length of the second susceptor, or a quarter the length of the second susceptor. For example, the first susceptor may have a length that is two thirds the length of the second susceptor, or three quarters the length of the second susceptor.

[0167] In this embodiment, the second susceptor 131 , the inductor coil 42, and a portion of the power control electronics 43 together form an inductive heating arrangement 45 when the second susceptor 131 is received in the cavity 41 of the aerosol-generating device 12. In this embodiment, the inductor coil 42, and a portion of the power control electronics 43 together form the inductive heating arrangement 45 when the second susceptor 131 is not received in the cavity 41 of the aerosolgenerating device 12.

[0168] As shown in Figure 5, in use, when the connection end 121 of the second aerosol-generating article 114 is received in the cavity 41 , the upstream end 135 of the upstream element 133 of the second aerosol-generating article 114 abuts the closed end of the cavity 41 of the aerosol-generating device 12.

[0169] Also as shown in Figure 5, when the connection end 121 of the second aerosol-generating article 114 is received in the cavity 41 , an air inlet 48, and air gap 49 are defined between an outer surface of the second aerosol-generating article 114 and the device housing 40 to enable ambient air to be drawn into the aerosol-generating system 10.

[0170] An airflow path is defined through the aerosol-generating system 10 when the connection end 121 of the second aerosol-generating article 114 is received in the cavity 41. The airflow path comprises the air inlet 48, the air gap 49, and the second aerosol-generating article 114.

[0171] A user may draw on the mouth end 120 of the second aerosol-generating article 114, and draw ambient air into the aerosol-generating system 10 at the air inlet 48, through the airflow path, and out of the aerosol-generating system 10 at the mouthpiece element 115. Ambient air enters the aerosolgenerating system 10 at the air inlet 48, between the second aerosol-generating article 114 and the device housing 40, through the air gap 49, and into the second aerosol-generating article 114 at the upstream end 135 of the upstream element 133. Air flows through the second aerosol-generating article 114, from the upstream end to the downstream end, through the upstream element 133, through the second aerosol-forming substrate 126, through the hollow tubular segment 117, and out of the aerosol-generating system 10 at the mouthpiece element 115.

[0172] In use, the connection end 121 of the second aerosol-generating article 114 is inserted into the cavity 41 of the aerosol-generating device 12. The power control electronics 43 determine that the second aerosol-generating article 114 is received in the cavity 41 , as described in more detail below, and supply power from the DC power supply 44 to the inductive heating arrangement 45 in a second mode, which in this embodiment is a continuous mode.

[0173] In the continuous mode the power control electronics 43 are configured to supply power to the inductor to generate an alternating magnetic field in the cavity 41. In this example, in the continuous mode, the power control electronics are configured to supply power to the inductor independently of a puff being detected to generate an alternating magnetic field in the cavity 41 to continuously heat the second susceptor 131 of the second aerosol-generating article 114 that is at least partially received in the cavity 41 .

[0174] The power control electronics 43 cause an alternating current from the power supply 44 to be supplied to the inductor coil 42, which generates an alternating magnetic field in the cavity 41 . The second susceptor 131 of the second aerosol-generating article 114 is penetrated by the alternating magnetic field and is heated by Joule heating through induction of eddy currents in the susceptor, and through hysteresis losses. The heated second susceptor 131 heats the second aerosol-forming substrate 126, which releases volatile compounds in a vapour. When a user takes a puff on the mouthpiece element 115 of the second aerosol-generating article 114, air is drawn into the aerosolgenerating system 10 at the air inlet 48, through the air gap 49, and into the second aerosol-generating article 114 at the upstream end 135 of the upstream element 133. The vapour from the heated second aerosol-forming substrate 126 is entrained in the airflowthrough the second aerosol-forming substrate 126, and cools and condenses into an aerosol as it is drawn along the second aerosol-generating article 114 to the mouthpiece element 115. The aerosol is drawn out of the aerosol-generating system 10 at the mouthpiece element 115, where it is inhaled by the user.

[0175] Figure 6 shows further details of the inductive heating arrangement 45 used to generate an alternating magnetic field within the cavity 41 of the aerosol-generating device 12. According to the present embodiment, the inductive heating arrangement 45 comprises a DC / AC inverter which is connect to the DC power supply 44, shown in Figures 2, 3, and 5. The DC / AC inverter includes a Class-E power amplifier which in turn includes the following components: a transistor switch 51 comprising a Field Effect Transistor (FET), for example a Metal-Oxide-Semiconductor Field Effect Transistor (MOSFET), a transistor switch supply circuit indicated by the arrow 52 for supplying the switching signal (gate-source voltage) to the transistor switch 51 , and an LC load network 53 comprising a shunt capacitor C1 and a series connection of a capacitor C2 and inductor L2. The inductor L2 corresponds to the inductor coil 42 shown in Figures 2, 3, and 5 used to generate an alternating magnetic field within the cavity 41 . In addition, there is provided a choke L1 for supplying a DC supply voltage +V_DC from the DC power supply 44. Also shown in Figure 6 is the ohmic resistance R representing the total equivalent resistance or total resistive load 54, which - in use of the system, when the aerosol-generating article 14 is inserted in the cavity 41 of the aerosol-generating device 12 - is the sum of the ohmic resistance of the inductor coil 42, marked as L2, and the ohmic resistance of the susceptor 31 . Otherwise, in case no article is inserted in the cavity 41 , the equivalent resistance or resistive load 54 only corresponds to the ohmic resistance of the inductor coil 42.

[0176] Further details of the inductive heating arrangement 45 according to the present embodiment, in particular with regard to its working principles, are disclosed, for example, in WO 2015 / 177046 A1.

[0177] The power control electronics 43 of the aerosol-generating device 12 are configured to detect insertion of an aerosol-generating article into the cavity 41 . The power control electronics 43 are also configured to identify the type of aerosol-generating article received in the cavity 41 , and to adapt the heating process to the type of aerosol-generating article that is received in the cavity 41 .

[0178] Detection of insertion of an aerosol-generating article in the cavity 41 , and identification of the type of aerosol-generating article received in the cavity 41 is realized via the inductive heating arrangement 45 itself. Advantageously, this avoids the need for separate sensors. Detection of an aerosol-generating article received in the cavity 41 , and identification of the type of aerosol-generating article received in the cavity 41 is achieved by detecting at least one property of the inductive heating arrangement 45 that changes when a susceptor of an aerosol-generating article is received in the cavity 41 .

[0179] Detection of insertion of an aerosol-generating article, and identification of the type of aerosolgenerating article received in the cavity 41 is achieved by detection of a change in at least one property of the inductive heating arrangement 45 due to the presence of the susceptor when an aerosolgenerating article is received in the cavity 41 .In the present embodiment, the conductance of the total resistive load 54 of the inductive heating arrangement 45 is used as a property of the inductive heating arrangement 45 that is monitored to detect insertion of an aerosol-generating article into the cavity 41 , and to determine the type of aerosol-generating article that is received in the cavity 41 . The value of the conductance of the total resistive load 54 of the inductive heating arrangement 45 depends on the presence of a susceptor of an aerosol-generating article in the cavity 41 , in close proximity to the inductor coil 42.

[0180] When an aerosol-generating article is inserted in the cavity 41 of the aerosol-generating device 12, the conductance of the total resistive load 54 of the inductive heating arrangement 45 comprises the combination of the conductance of the inductor coil 42 and the conductance of the susceptor of the aerosol-generating article. Whereas, when an aerosol-generating article is not received in the cavity 41 of the aerosol-generating device 12, the conductance of the total resistive load 54 of the inductive heating arrangement 45 comprises the conductance of the inductor coil 42 only, without the conductance of a susceptor. The difference in the conductance of the total resistive load 54 of the inductive heating arrangement 45 when an aerosol-generating article is received in the cavity 41 compared to when an aerosol-generating article is not received in the cavity 41 may be detected via the DC current l_DC provided from the DC power supply 44 to the inductive heating arrangement 45, that is, to the LC load network 53. For this, the power control electronics 43 comprise a current measurement device 55 arranged in series connection between the DC power supply 44 and the LC load network 53. Accordingly, when an aerosol-generating article is inserted into the cavity 41 of the aerosol-generating device 12, the presence of the susceptor of the aerosol-generating article in the cavity 41 decreases the conductance of the total resistive load 54 of the inductive heating arrangement 44. This in turn causes a decrease in the DC current feeding the inductive heating arrangement 45. The change in the DC current l_DC is detected by the current measurement device 55, which in turn is used to determine that an aerosol-generating article is received in the cavity 41 , and also to determine the type of aerosol-generating article received in the cavity 41 . When it is determined that a known type of aerosol-generating article is received in the cavity 41 , this triggers a signal to activate a heating operation of the inductive heating arrangement 45 that is specifically configured for heating the type of aerosol-generating article that is received in the cavity 41. The power control electronics 43 are configured to perform different heating operations of the inductive heating arrangement 45 for different types of aerosol-generating article, and different signals are triggered when it is determined that different types of aerosol-generating article are received in the cavity 41 .

[0181] The power control electronics 43 are configured to operate the aerosol-generating device 12 in an article detection mode before it is determined that an aerosol-generating article is received in the cavity 41. This reduces power consumption compared to continuous operation in a heating mode. The article detection mode is triggered when the aerosol-generating device 12 is turned on by a user. The article detection mode is a pulsed mode, in which the power control electronics 43 supply power to the inductive heating arrangement 45 from the DC power supply 44 in a series of probing pulses. For this, the power control electronics 43 comprise a switch 56 that is arranged and configured to control a supply of power from the DC power supply 44 to the inductive heating arrangement 45. In the present embodiment, the switch 56 is arranged in series connection between the DC power supply 44 and the LC load network 53. During the article detection mode, the switch 56 is intermittently opened and closed such as to generate probing pulses for intermittently powering on the inductive heating arrangement 45. In contrast, during some heating modes of the aerosol-generating device 12, the switch 56 may be permanently closed to continuously apply a DC voltage from the DC power supply 44 to the inductive heating arrangement 45.

[0182] As shown in Figure 6, the switch 56 and the current measurement device 55 are both part of a control circuit which also includes a microprocessors?. The microprocessors? is configured to control the switch 56 used to generate the probing pulses for intermittently powering on the inductive heating arrangement 45, to read out the measurement device 55 for measuring the current l_DC supplied from the DC power supply to the inductive heating arrangement 45, and to control the transistor switch driver circuit 52 of the inductive heating arrangement 45. In the article detection mode, the microprocessor 57 starts driving the switch 56 by closing it for a pre-determined closing time interval, thereby generating a probing pulse, which is a current pulse having a pulse duration T1 , corresponding to the closing time interval. The pulse duration T1 of the probing pulse may be in a range between 1 microsecond and 500 microseconds, in particular between 10 microseconds and 300 microseconds, preferably between 15 microseconds and 120 microseconds, most preferably between 30 microseconds to 100 microseconds. At the end of the closing time interval, the microprocessor 57 opens the switch 56 again for a pre-determined opening time interval, thereby interrupting the current passage to the inductive heating arrangement 45. The opening time interval corresponds to the time interval between two consecutive probing pulses, which may be in a range between 50 milliseconds and 2 seconds, in particular between 100 milliseconds and 2 seconds, preferably between 500 milliseconds and 1 second. Closing and opening of the switch 56 may occur at regular time intervals such as to generate periodic probing pulses for periodically powering on the inductive heating arrangement 45. Thus, the sum of the closing time interval and the opening time interval, or the sum of the pulse duration and the time interval between two consecutive power pulses corresponds to the periodicity of the probing pulse series.

[0183] Figure 7 illustrates an example of a power profile, showing a duty cycle against time elapsed during use of an aerosol-generating system. In particular, a duty cycle against time elapsed during use of the aerosol-generating device 12 when the first aerosol-generating article 14 is received in the cavity 41 , during a usage session in the puff mode. The usage session may last for a predetermined amount of time, or a predetermined number of puffs, for example for 5 minutes or for 6 puffs. The graph of Figure 7 illustrates two puffs taken during a usage session.

[0184] In the puff mode a user puffs on the aerosol-generating system 10 as shown in Figure 3. At the start of the puff, the power control electronics 43 are configured to supply a maximum power to the inductor coil 42, in this example the power is supplied with a first duty cycle 205 of 95 percent. The first duty cycle 205 heats the first susceptor 31 of the aerosol-generating system 10 to quickly heat the first aerosol-generating substrate 26 to generate an aerosol for user inhalation. As the puff progresses, the duty cycle is reduced to avoid overheating the first susceptor 31 . As shown in Figure 7, the duty cycle is reduced discontinuously, in a step-wise manner. However, it should be appreciated that the duty cycle could alternatively be reduced continuously. After approximately 2000 milliseconds, the duty cycle is reduced to a second duty cycle 215 of 50 percent. Between the first 205 and second 215 duty cycles, the duty cycle is reduced in a stepwise manner to 85 percent at 500 milliseconds, to 75 percent at 1000 milliseconds, to 65 percent at 1500 milliseconds. At the end of the puff, at 3000 milliseconds, the duty cycle is reduced to 0, stopping power being supplied to the inductor coil 42.

[0185] The system is now between puffs. In this example, there are no puffs between 3000 milliseconds to 30000 milliseconds. When the user is not puffing, no power is supplied to the inductor, so the duty cycle is zero. At 30000 milliseconds, a second puff is detected. When the puff is detected, the power control electronics 43 are configured to supply powerto the inductor coil 42. In this example, the power control electronics are configured to supply the same amount of power to the inductor during the first puff and the second puff, which gives a first duty cycle for the second puff 305 of 95 percent. However, it should be appreciated that in other embodiments the first duty cycle of the second puff may be different to the first duty cycle of the second puff. For example, the second duty cycle of the second puff may be lower than the second duty cycle of the first puff. In the second puff, again the duty cycle is reduced to avoid overheating the first susceptor 31 , as the puff progresses. As shown in Figure 7, the duty cycle of the second puff is also reduced discontinuously, in a step-wise manner. After approximately 32000 milliseconds, approximately 2000 milliseconds after the start of the second puff, the duty cycle of the second puff is reduced to a second duty cycle of the second puff 315 of 50 percent, which is the same as the second duty cycle of the first puff 215. However, it should be appreciated that in other embodiments the second duty cycle of the second puff may be different to the second duty cycle of the first puff.

[0186] It will be appreciated that the above described examples are exemplary, and other embodiments with different features are envisaged in this disclosure. For example, it is envisaged that in some embodiments, the inductor coil 42 may have a different form, such as a flat coil, and the aerosolgenerating device 12 may be provided with more than one inductor coil 42. It is also envisaged that the article detection mode may be triggered, for example, by extracting the aerosol-generating device 12 from a power charging unit. For this, the aerosol-generating device 12 may be configured to detect the extraction of the device from a power charging unit.

[0187] For the purpose of the present description and of the appended claims, except where otherwise indicated, all numbers expressing amounts, quantities, percentages, and so forth, are to be understood as being modified in all instances by the term "about". Also, all ranges include the maximum and minimum points disclosed and include any intermediate ranges therein, which may or may not be specifically enumerated herein. In this context, therefore, a number A is understood as A ± 10 % of A. Within this context, a number A may be considered to include numerical values that are within general standard error for the measurement of the property that the number A modifies. The number A, in some instances as used in the appended claims, may deviate by the percentages enumerated above provided that the amount by which A deviates does not materially affect the basic and novel characteristic(s) of the claimed invention. Also, all ranges include the maximum and minimum points disclosed and include any intermediate ranges therein, which may or may not be specifically enumerated herein.

Claims

CLAIMS1 . An aerosol-generating device comprising: a cavity configured to removably receive at least a portion of an aerosol-generating article comprising an aerosol-forming substrate; an inductor configured to generate an alternating magnetic field in the cavity to heat a susceptor in an aerosol-generating article received in the cavity; a power supply for supplying power to the inductor; and power control electronics configured to control the supply of power from the power supply to the inductor to generate an alternating magnetic field in the cavity, and wherein the power control electronics are configured to operate in a puff mode, in which the power control electronics are configured to: detect a puff when at least a portion of the aerosol-generating article is received in the cavity; supply power to the inductor during the puff, wherein the power control electronics are configured to supply a first amount of power to the inductor; and after a predetermined time interval during the puff to supply a second amount of power to the inductor, wherein the second amount of power is less than the first amount of power.

2. The aerosol-generating device according to claim 1 , wherein the power control electronics are configured to detect a start of the puff and supply the first amount of power in response to the start of the puff, and wherein the first amount of power is a maximum power level supplied the inductor.

3. The aerosol-generating device according to any preceding claim, wherein in the puff mode, the power control electronics are configured to detect an end of the puff, and in response stop the supply of power to the inductor.

4. The aerosol-generating device according to any preceding claim, wherein in the puff mode, when no puff is detected the power control electronics are configured to prevent supply of power to the inductor.

5. The aerosol-generating device according to any preceding claim, wherein the power control electronics are configured to discontinuously decrease supply of power from the first amount of power to the second amount of power.

6. The aerosol-generating device according to any one of claims 1 to 4, wherein the power control electronics are configured to continuously decrease the supply of power from the first amount of power to the second amount of power.

7. The aerosol-generating device according to any preceding claim, wherein the second amount of power is less than 90 percent, less than 80 percent, less than 70 percent, less than 60 percent or less than 50 percent of the first amount of power.

8. The aerosol-generating device according to any preceding claim, wherein the first amount of power is supplied at a first duty cycle and the second amount of power is supplied a second duty cycle, wherein the second duty cycle is lower than the first duty cycle.

9. The aerosol-generating device according to any preceding claim, wherein the time interval is between 5000 milliseconds and 200 milliseconds, for example, between 3000 milliseconds and 300 milliseconds, for example between 2000 milliseconds and 500 milliseconds.

10. The aerosol-generating device according to any preceding claim, wherein the power control electronics comprise a puff sensor configured to detect the puff, and optionally wherein the puff sensor comprises at least one of an airflow sensor and a pressure sensor.11 . The aerosol-generating device according to any preceding claim, wherein the power control electronics are configured detect a first puff and a second puff after the first puff, and wherein the power control electronics are configured to supply a high first amount and a high second amount of power to the inductor during the first puff; and supply a low first amount and a low second amount of power to the inductor during the second puff; wherein the low first amount of power is less than the high first amount of power and the low second amount of power is less than the high second amount of power.

12. The aerosol-generating device according to any preceding claim, wherein the cavity is configured to: removably receive at least a portion of a first aerosol-generating article, the first aerosolgenerating article comprising a first susceptor element, and a first aerosol-forming substrate; and removably receive at least a portion of a second aerosol-generating article, separately from the first aerosol-generating article, the second aerosol-generating article comprising a second susceptor element, and a second aerosol-forming substrate, the second aerosol-forming substrate being different from the first aerosol-forming substrate.

13. The aerosol-generating device according to claim 12, wherein: in the puff mode the power control electronics are configured to supply power to the inductor to generate an alternating magnetic field in the cavity to heat the first susceptor element to generate an aerosol from the first aerosol-forming substrate; and the power control electronics are configured to operate the device in a continuous mode, wherein in the continuous mode the power control electronics are configured to supply power to the inductor to generate an alternating magnetic field in the cavity to continuously heat the second susceptor element to generate an aerosol from the second aerosol-forming substrate, when the second aerosol-generating article is received in the cavity.

14. An aerosol-generating system comprising: an aerosol-generating device according to any one of claims 1 to 13; a first aerosol-generating article, the first aerosol-generating article comprising a first susceptor, and a first aerosol-forming substrate; and a second aerosol-generating article, the second aerosol-generating article comprising a second aerosol-forming substrate, separately from the first aerosol-generating article, the second aerosol-generating article comprising a second susceptor, and a second aerosol-forming substrate, the second aerosol-forming substrate being different from the first aerosol-forming substrate.

15. An aerosol-generating system according to claim 14, wherein the first aerosol-forming substrate is a liquid aerosol-forming substrate, and the second aerosol-forming substrate is a solid aerosol-forming substrate.

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