Aerosol generation system having multiple modes of operation

Abstract

The inductively heated aerosol generation system includes an inductive heating arrangement having an inductor and a susceptor, a power supply for supplying power to the inductive heating arrangement, and a controller configured to control the power supplied from the power supply to the inductive heating arrangement and to monitor electrical control parameters. The controller is configured to operate the aerosol generation system in a plurality of operating modes, the plurality of operating modes including at least a calibration mode, a heating mode, a recalibration mode, and a safety mode. By switching between the plurality of operating modes, the system enables consistent and reliable generation of aerosols using inductive heating, even when the susceptor is a disposable component of the inductive heating arrangement.

Description

[Technical field]

[0001] The present disclosure relates to an inductively heated aerosol generating system configured to be controlled in multiple operational modes. [Background technology]

[0002] An increasing number of aerosol generating systems, such as e-cigarettes and heated tobacco systems, comprise an induction heating arrangement configured to heat an aerosol-forming substrate to generate an aerosol. The induction heating arrangement typically comprises an inductor inductively coupled to a susceptor. The inductor generates an alternating magnetic field that causes heating of the susceptor. Typically, the susceptor is in direct contact with the aerosol-forming substrate, and heat is transferred from the susceptor to the aerosol-forming substrate primarily by conduction. The temperature of the susceptor needs to be controlled to provide optimal aerosol generation, both in terms of the amount of aerosol generated and in terms of its composition.

[0003] Induction heating arrangements provide contactless heating of the susceptor. This is beneficial in many situations, particularly where the susceptor is provided in a separate system component from the inductor. For the same reasons, it is desirable to monitor and control the susceptor temperature without requiring a direct electrical connection to the susceptor and without requiring a separate dedicated temperature sensor connected to the susceptor. Difficulties in accurately monitoring the susceptor temperature can lead to overheating risks. It is desirable to provide an inductively heated aerosol generation system configured to provide improved temperature determination and fault mitigation. Summary of the Invention

[0004] According to one embodiment of the present invention, there is provided an inductively heated aerosol generation system comprising an inductor and a susceptor, a power supply for supplying power to the inductive heating arrangement, and a controller configured to control the power supplied from the power supply to the inductive heating arrangement. The controller may also be configured to monitor an electrical control parameter. The controller may be configured to operate the aerosol generation system in a plurality of operating modes. The plurality of operating modes preferably includes, for example, a calibration mode for determining a target value of the electrical control parameter. The plurality of operating modes preferably includes a heating mode, in which power is supplied to the inductor to maintain the susceptor at an operating temperature. The operating temperature is preferably maintained by controlling the power supplied to the inductor with reference to a target value of the electrical control parameter. The plurality of operating modes preferably includes, for example, a recalibration mode for periodically or intermittently re-determining the target value of the electrical control parameter. The plurality of operating modes preferably includes a safety mode, for example, a mode in which the controller adjusts the power provided to the inductive heating arrangement in response to one or more predetermined criteria, for example one or more predetermined safety criteria being met.

[0005] Thus, there may be provided an inductively heated aerosol generation system comprising an induction heating arrangement having an inductor and a susceptor, a power supply for supplying power to the induction heating arrangement, and a controller configured to control the power supplied from the power supply to the induction heating arrangement and to monitor electrical control parameters. The controller is configured to operate the aerosol generation system in a plurality of operating modes, the plurality of operating modes including at least: a calibration mode for determining target values ​​for electrical control parameters; a heating mode in which power is supplied to an inductor to maintain the susceptor at an operating temperature, the operating temperature being maintained by controlling the power supplied to the inductor with reference to a target value of an electrical control parameter; a recalibration mode for periodically or intermittently re-determining the target values ​​of the electrical control parameters; and and a safety mode for adjusting the power provided to the induction heating arrangement in response to one or more predetermined criteria being met.

[0006] The multiple operating modes may further include a pre-heat mode for raising the temperature of the susceptor to a predetermined temperature before operating in a different operating mode, such as a calibration mode or a heating mode.

[0007] The ability to operate in multiple operating modes allows the controller to determine the control parameters and more precisely control the temperature of the susceptor and ensure that the temperature is precisely controlled over the duration of a use session in which the user is generating aerosols. The controller can be programmed with instructions to operate according to different modes having different operating objectives. For example, the objective of the calibration mode may be to determine the relationship between the monitorable control parameters and the temperature of the remote susceptor, and the objective of the heating mode may be to maintain the temperature of the susceptor as close as possible to a desired operating temperature during use of the system. The objective of the recalibration mode may be, among other things, to verify or correct the relationship between the control parameters and the temperature of the susceptor without unnecessarily interrupting the heating mode. The objective of the preheat mode may be to raise the temperature of the susceptor to an operating temperature, either as a prerequisite for the calibration mode or the heating mode. The objective of the safety mode is primarily to react to one or more signals or criteria that may indicate a potential fault or abnormal condition, particularly when there is a risk of an overheating event. The safety mode may also be a recovery mode in which corrective action is taken to correct a potential fault condition, for example, by initiating a calibration mode or a recalibration mode. By having the ability to operate in multiple modes and being configured to switch between modes as needed, the aerosol generating system according to the present invention can provide a more reliable and consistent user experience. The advantages can be particularly evident in an aerosol generating system comprising an aerosol generating device and an aerosol generating article configured to be consumed using the device. Such an aerosol generating article may be a disposable article or may be provided with an integral susceptor. Variations in such articles, for example in the dimensions and position of the susceptor, and the difficulty of repeatedly positioning such articles in the same exact position within the aerosol generating device, make it difficult to control the aerosol generation. An aerosol generating system configured to operate in multiple operating modes as described herein can significantly improve the user experience and reduce the risk of overheating failure occurring.

[0008] At least a portion of the susceptor is preferably configured to undergo a reversible phase transition when heated, e.g., when heated or cooled through a particular or predetermined temperature range. The controller is preferably configured to identify upper and lower boundaries of the phase transition and upper and lower boundary values ​​of an electrical control parameter associated with the upper and lower boundaries of the phase transition, e.g., during operation in a calibration mode. As a result of the calibration, a target value of the electrical control parameter may be determined to be a value between the upper and lower boundary values ​​of the electrical control parameter.

[0009] During operation according to the calibration mode, the controller may be configured to perform the steps of heating the susceptor through a predetermined temperature range, allowing the susceptor to cool through a predetermined temperature range, monitoring the electrical control parameter, identifying upper and lower boundary values ​​of the electrical control parameter associated with upper and lower boundaries of the phase transition, and determining a target value for the electrical control parameter.

[0010] During operation according to the calibration mode, the controller may be configured to perform the steps of heating the susceptor, monitoring an electrical control parameter while heating the susceptor, identifying upper and lower boundary values ​​of the electrical control parameter associated with upper and lower boundaries of a phase transition, allowing the susceptor to cool through a predetermined temperature range, monitoring the electrical control parameter while allowing the susceptor to cool, and determining a target value for the electrical control parameter.

[0011] The step of heating the susceptor may involve supplying power to the induction heating arrangement. The power supplied to heat the susceptor during the calibration mode may be supplied at a duty cycle of greater than 80%, such as greater than 90%, for example 100%.

[0012] Allowing the susceptor to cool may involve supplying power to the induction heating arrangement with a reduced duty cycle and monitoring an electrical control parameter. By supplying some power during cooling, the controller can monitor the value of the electrical control parameter and thereby monitor the temperature of the susceptor as it cools. Allowing the susceptor to cool may involve supplying power to the induction heating arrangement as pulses of energy, e.g., pulses of current, e.g., pulses of energy having a duty cycle of less than 10%, e.g., less than 2% or less than 1%, and monitoring the value of the electrical control parameter during each of the pulses.

[0013] The susceptor is preferably located and / or positionable within the alternating electromagnetic field generated by the inductor. The susceptor may be configured to undergo a reversible phase transition when heated through a predetermined temperature range, with a phase transition start point and a phase transition end point being identifiable by a change in the value of the electrical control parameter as the susceptor is heated through the predetermined temperature range, e.g., as the susceptor is heated according to a calibration protocol during a calibration mode. A target value of the electrical control parameter is preferably determined to be between the values ​​of the electrical control parameter at the phase transition start point and the phase transition end point.

[0014] Advantageously, the inductive heating arrangement may exhibit a reversal in apparent resistance while undergoing a phase transition, for example, the inductive heating arrangement may exhibit a reversal in apparent conductance while undergoing a phase transition.

[0015] The system may be configured such that the apparent resistance of the induction heating system increases before the start of the phase transition, decreases as the phase transition heats through, and increases as the phase transition heats beyond the end of the phase transition. Apparent conductance is the reciprocal of apparent resistance. Thus, the apparent conductance of the induction heating system may decrease before the start of the phase transition, increase as the phase transition heats through, and decrease as the phase transition heats beyond the end of the phase transition.

[0016] The electrical control parameter is preferably indicative of the temperature of the susceptor and / or is indicative of a material property of the susceptor that varies as a function of temperature and / or the electrical control parameter is a parameter that varies as a function of the temperature of the susceptor. The electrical control parameter may be a parameter selected from the list consisting of the electrical resistance of the susceptor, the apparent electrical resistance of the induction heating arrangement, the electrical conductance of the susceptor, the apparent electrical conductance of the induction heating arrangement, the current supplied to the induction heating arrangement, and the power supplied to the induction heating arrangement.

[0017] The controller may be configured to monitor at least one power parameter representative of power supplied to the induction heating arrangement during operation. The at least one power parameter may be used as an electrical control parameter or the at least one power parameter may be used to derive an electrical control parameter. The at least one power parameter may be or may include a current supplied to the induction heating arrangement during operation. The at least one power parameter may be or may include a voltage across the induction heating arrangement during operation.

[0018] As an example, the apparent conductance of an induction heating arrangement may be calculated by the formula σ=I / V, where σ is the apparent conductivity of the induction heating arrangement, I is the current delivered to the induction heating arrangement, and V is the voltage across the induction heating arrangement. Thus, if power is delivered at a constant voltage, the apparent conductance may be determined in real time by monitoring the current and applying the formula. Both the current and voltage may be monitored, and both of these monitored parameters may be used to calculate the apparent conductance. The apparent resistance is the inverse of the apparent conductance and may be calculated using the formula ρ=V / I, where ρ is the apparent resistance.

[0019] In some embodiments, the aerosol-generating system comprises an aerosol-generating article and an aerosol generating device configured to receive the aerosol-generating article. The aerosol-generating article includes an aerosol-forming substrate, and the susceptor is preferably disposed in thermal communication with the aerosol-forming substrate. The aerosol-generating article may be a disposable article, for example an article similar to a conventional cigarette.

[0020] The aerosol generating device may comprise an inductor, a controller, and a power supply for providing power to the controller. The aerosol generating device may further comprise a DC / AC converter for converting direct current provided by the power supply into alternating current for powering the inductor.

[0021] The aerosol generating device is preferably configured to inductively heat an aerosol-forming substrate so as to generate an inhalable aerosol during a session of use.

[0022] The aerosol generating device may be configured to detect when an aerosol-generating article is received within the aerosol generating device. For example, the device may be configured to detect an electrical signal associated with a susceptor of the article disposed within an inductor of the device. As a further example, the device may be configured with a sensor, such as an optical sensor, that detects the presence of the aerosol-generating article when properly positioned within the device. The aerosol generating device may be further configured to determine whether the aerosol-generating article received within the aerosol generating device is an article configured for use with the aerosol generating device, and preferably, operation of the aerosol generating device to heat the aerosol-generating article is prevented if the detected article is not configured for use with the aerosol generating device. For example, the article may be configured to provide a specific electrical response when a susceptor or electromagnetic indicator of the article interacts with an alternating electric field generated by the inductor. Alternatively, the article may include a determinable marking or code for determining whether the article is configured for use with the device.

[0023] The phase transition of the susceptor may be a magnetic or crystalline phase transition. The phase transition is preferably a phase transition that occurs at a known temperature when the susceptor is heated by supplying power to the induction heating arrangement. Such a phase transition may be detectable by monitoring an electrical parameter of the apparatus during operation, for example during a calibration mode, and may provide an indication of a relationship between the value of the monitored electrical parameter or parameters and the actual temperature of the susceptor. This relationship may vary slightly from article to article and may also vary depending on whether the article is correctly inserted into the apparatus. Typically, the phase transition may be a ferromagnetic / paramagnetic phase transition, or a ferrimagnetic / paramagnetic phase transition, or an antiferromagnetic / paramagnetic phase transition.

[0024] The susceptor should have the ability to heat the aerosol-forming substrate quickly and efficiently. It is preferable that the susceptor be able to heat the substrate to the temperature required to generate the aerosol without wasting energy in heating the susceptor itself. It is also desirable that the susceptor be able to cool quickly when the power is reduced or turned off. Thus, the dimensions and materials of the susceptor can be selected to configure the susceptor to efficiently heat the article.

[0025] The susceptor may include a first material that does not undergo a reversible phase transition when heated through a predetermined heating cycle or a predetermined temperature range, and a second material that undergoes a reversible phase transition when heated through a predetermined heating cycle or a predetermined temperature range.

[0026] The operating temperature range, or operating temperature range, is preferably selected to optimize the generation of aerosol from the aerosol-forming substrate. The operating temperature range may be set by a target operating temperature, and the system may be configured to maintain the temperature of the susceptor as close as possible to the target operating temperature. The operating temperature range may be between 100°C and 500°C, for example between 200°C and 400°C. A preferred operating temperature range may be between 300°C and 400°C, for example between 350°C and 390°C. The operating heating mode may have a target operating temperature of between 300°C and 400°C, for example between 350°C and 390°C, for example about 350°C, or 360°C, or 370°C, or 380°C.

[0027] In embodiments where the susceptor exhibits a reversible phase transition when heated through a predetermined temperature range, the phase transition may be a magnetic phase transition or a crystalline phase transition. For example, the phase transition may be a ferromagnetic / paramagnetic phase transition, or a ferrimagnetic / paramagnetic phase transition, or an antiferromagnetic / paramagnetic phase transition. For example, the susceptor, or a portion of the susceptor, may be a material that undergoes a Curie transition within a predetermined temperature range.

[0028] The susceptor may be configured to optimize heating efficiency while still undergoing a reversible phase transition within a predetermined temperature range. Thus, the susceptor may include a first material that does not undergo a reversible phase transition during the predetermined temperature range and a second material that does undergo a reversible phase transition during the predetermined temperature range. The first material may comprise more than 50% of the volume of the susceptor, preferably more than 60% of the volume, or more than 70% of the volume, or more than 80% of the volume, or more than 90% of the volume, or more than 95% of the volume. The first material may be an iron-based alloy, such as stainless steel. The second material may be nickel or a nickel-based alloy. The second material may be present as a patch of material disposed on the first material. The second material may be encapsulated by the first material. The second material may be laminated on or encapsulate the first material.

[0029] Advantageously, the target value of the electrical control parameter may be determined to correspond to a susceptor temperature equal to or less than a Curie temperature of a material within the susceptor. The susceptor may include a first susceptor material having a first Curie temperature and a second susceptor material having a second Curie temperature. The second Curie temperature may be lower than the first Curie temperature. The target value of the electrical control parameter may correspond to a susceptor temperature equal to or less than the second Curie temperature.

[0030] The first and second susceptor materials are preferably two separate materials bonded together and thus in intimate physical contact with each other, thereby ensuring that both materials have the same temperature due to thermal conduction. The two susceptor materials are preferably two layers or strips bonded together, preferably along one of their major surfaces. The susceptor may further comprise a further third layer of susceptor material. The third layer of susceptor material is preferably made of the first susceptor material. The thickness of the third layer of susceptor material is preferably less than the thickness of the layer of the second susceptor material.

[0031] The target value of the electrical control parameter may correspond to a susceptor temperature that is within a temperature range in which the conductance of the susceptor increases monotonically with increasing temperature. At the lower end of this temperature range, the material within the susceptor may begin to change phase from a ferromagnetic or ferrimagnetic state to a paramagnetic state. At the upper end of this temperature range, the material may complete the phase change from a ferromagnetic or ferrimagnetic state to a paramagnetic state.

[0032] The susceptor may be formed as a single component, for example as an elongated pin, blade, wire, or strip, or as a sheet or mesh. The susceptor may be an elongated susceptor having a length dimension greater than its width or thickness dimension. The susceptor may have a rectangular or circular transverse cross-section. The susceptor may be in the form of a strip of material or a strip of foil.

[0033] The susceptor may have a length of 8 mm to 100 mm, for example, 10 mm to 30 mm, for example, 12 mm to 20 mm. The susceptor may have a width of 2 mm to 6 mm, for example, 3 mm to 5 mm, for example, 3.5 mm to 4.5 mm. The susceptor may have a thickness of 0.01 mm to 2 mm, for example, 0.05 mm to 1.5 mm, for example, 0.1 mm to 1 mm.

[0034] The susceptor may be formed from a plurality of individual components, for example, from a plurality of elongated pins, blades, wires, or strips, from a plurality of sheets or meshes, or from a plurality of particles, for example, the susceptor may be formed from a plurality of particles disposed in thermal contact with or within the aerosol-forming substrate.

[0035] The power source may be a DC power source, for example a battery located within the aerosol generating device, which further includes a DC to AC converter, for example a DC to AC inverter, for supplying AC power to the inductor.

[0036] The inductor may include an inductor coil. The inductor coil may be a helical coil or a flat planar coil, particularly a pancake coil or a curved planar coil. The inductor may be used to generate a varying magnetic field. The varying magnetic field may be a high frequency varying magnetic field. The varying magnetic field may be in the range of 500 kHz (kilohertz) to 30 MHz (megahertz), particularly 5 MHz to 15 MHz, preferably 5 MHz to 10 MHz. The varying magnetic field is used to inductively heat the susceptor due to at least one of eddy currents or hysteresis losses, depending on the electrical and magnetic properties of the susceptor material.

[0037] The induction heating arrangement may include a DC / AC converter and an inductor connected to the DC / AC converter. The susceptor may be inductively coupled to the inductor. Power from a power source may be provided to the inductor via the DC / AC converter as a plurality of current pulses, each pulse separated by a time interval. Controlling the power provided to the induction heating arrangement may include controlling a time interval between each of the plurality of pulses. Controlling the power provided to the induction heating arrangement may include controlling a length of each pulse of the plurality of pulses.

[0038] The system may be configured to measure the DC current drawn from the power source at the input side of the DC / AC converter. A conductance or resistance value associated with the susceptor may be determined based on the DC supply voltage of the power source and from the DC current drawn from the power source. The system may further be configured to measure the DC supply voltage of the power source at the input side of the DC / AC converter. This is due to the fact that there is a monotonic relationship between the real conductance of the susceptor (which cannot be determined when the susceptor forms part of the article) and the apparent conductance thus determined (because the susceptor contributes the conductance of the LCR circuit (of the DC / AC converter) to which it is coupled, and therefore most of the load (R) is due to the resistance of the susceptor). The conductance is 1 / R. Thus, when referring to the conductance of a susceptor in this text, reference is made to the apparent conductance when the susceptor forms part of a separate aerosol-generating article.

[0039] The aerosol generating device preferably comprises an inductor, a controller, and a power supply for providing power to the controller. The aerosol generating device may further comprise a DC / AC converter for converting a direct current provided by the power supply to an alternating current for powering the inductor. The current provided to the DC / AC converter may be monitored and may form or be used to derive an electrical control parameter. The aerosol generating device may be configured to inductively heat an aerosol-forming substrate to generate an inhalable aerosol during a session of use.

[0040] In some examples, the apparent resistance of the induction heating arrangement exhibits a positive relationship with temperatures just below the lower boundary of the phase transition and just above the upper boundary of the phase transition, and a negative relationship with temperatures between the upper and lower boundaries of the phase transition.

[0041] In some embodiments, the apparent conductance of the induction heating arrangement exhibits a negative relationship with temperatures just below the lower boundary of the phase transition and just above the upper boundary of the phase transition, and a positive relationship with temperatures between the upper and lower boundaries of the phase transition.

[0042] The operating temperature during the heating mode is preferably between the upper and lower boundaries of the phase transition, i.e., the start and end of the phase transition.

[0043] The heating mode is preferably configured to maintain the temperature of the susceptor according to a predetermined temperature profile. Power may be supplied to the inductor during the heating mode as power pulses, e.g. current pulses, and the temperature of the susceptor is controlled by varying the duty cycle of the inductor. The controller may be configured to control the temperature of the susceptor during the heating mode with reference to a target value of the apparent resistance of the induction heating arrangement, the target value of the apparent resistance being determined during the calibration mode or the recalibration mode. The controller may be configured to control the temperature of the susceptor during the heating mode with reference to a target value of the apparent conductance of the induction heating arrangement, the target value of the apparent conductance being determined during the calibration mode or the recalibration mode.

[0044] The electrical control parameter may be monitored during the heating mode to verify that the value of the electrical control parameter is between upper and lower boundary values ​​of the electrical control parameter associated with the upper and lower boundaries of the phase transition, and if this cannot be verified, the device may be configured to operate according to a safety mode.

[0045] The response of the electrical control parameters to the power supplied to the induction heating arrangement, for example a power pulse supplied to the induction heating arrangement, may be monitored during the heating mode to verify that the susceptor is within an operating temperature range, and if this cannot be verified the apparatus may be configured to operate according to a safety mode.

[0046] Operation in accordance with the safety mode may involve a reduction in the power supplied to the induction heating arrangement, e.g., a reduction in the duty cycle supplied to the inductor for a period sufficient to allow the susceptor to cool, e.g., to a temperature below the lower boundary of the phase transition.

[0047] The aerosol generating device may include one or more sensors to provide feedback about operating conditions, for example, the aerosol generating device may include a puff sensor to determine a user puff, for example an airflow sensor, or a temperature sensor such as a thermistor mounted in the airflow path of the aerosol generating device.

[0048] The heating mode may include two or more control protocols. For example, the heating mode may be configured to operate according to either a non-puff heating regime or a puff heating regime. The controller may be configured to operate according to the puff heating regime when it is detected that the user is puffing during the heating mode, and to operate according to the non-puff heating regime when it is not detected that the user is puffing during the heating mode.

[0049] The controller may be configured to apply limits to the power supplied to the induction heating arrangement during a puff heating regime, for example, by limiting the duty cycle to 50% of the maximum duty cycle, or 60% of the maximum duty cycle, or 70% of the maximum duty cycle, or 80% of the maximum duty cycle. This may prevent inadvertent overheating during a user puff, where the increased power requirements to maintain the temperature of the susceptor at the operating temperature increases the risk that the actual temperature of the susceptor will exceed the operating temperature.

[0050] The system may be configured to terminate the calibration or recalibration mode if the user is determined to take a puff while operating under the calibration or recalibration mode. The controller may prevent or delay initiation of the recalibration mode if the user is determined to be taking a puff.

[0051] The aerosol generating system may include a temperature sensor located outside the airflow path, such as a thermocouple or thermistor mounted on the PCB of the aerosol generating device or a thermocouple or thermistor mounted within the substrate receiving cavity of the aerosol generating device, to monitor temperature, e.g., the temperature of the aerosol generating device.

[0052] The device may be configured to operate according to a safety mode if the temperature of a portion of the device is determined to be outside a predetermined range, or to terminate operation if the temperature of a portion of the device is determined to be outside a predetermined range.

[0053] The controller may be configured to interrupt the heating mode and perform a recalibration according to a recalibration mode, and preferably resume the heating mode if the recalibration is successfully performed. The recalibration mode may be performed periodically based on one or more of the following requirements: a predetermined duration, a predetermined number of user puffs, a predetermined number of temperature steps, and a measured voltage of the power supply.

[0054] The one or more predetermined criteria for the safety mode, e.g., safety criteria or safety triggers, are preferably criteria related to an operational event or a monitored operational parameter, and the controller is preferably configured to implement the safety mode in response to the one or more predetermined criteria being satisfied.

[0055] For example, at least one of the one or more predetermined criteria may be that the temperature of an electronic component of the aerosol generating system exceeds a predetermined temperature, e.g., the temperature of a PCB of the aerosol generating system exceeds a predetermined temperature, e.g., greater than 50° C., 60° C., or 70° C., or 80° C., or 100° C. Preferably, the temperature of the electronic component is monitored by a temperature sensor mounted on or near the electronic component.

[0056] For example, at least one of the one or more predetermined criteria may be that the temperature of a substrate-receiving cavity or chamber of the aerosol-generating system exceeds a predetermined temperature. For example, the temperature of a heated chamber of the aerosol-generating device exceeds a predetermined temperature, e.g., greater than 400° C., or 410° C., or 450° C., or 480° C. Preferably, the temperature of the cavity or chamber is monitored by a temperature sensor mounted within the substrate-receiving cavity or chamber.

[0057] For example, at least one of the one or more predetermined criteria may be that the temperature of the susceptor exceeds a maximum operating temperature, e.g., greater than 400° C., or 410° C., or 450° C., or 480° C. This may be determined by monitoring electrical control parameters. For example, at least one of the one or more predetermined criteria may be that the temperature of the susceptor exceeds a Curie temperature of a material component of the susceptor.

[0058] For example, at least one of the one or more predetermined criteria may be that the response of the electrical control parameters to the power supplied to the induction heating arrangement during the heating mode does not satisfy a predetermined condition, e.g., the apparent conductance of the induction heating arrangement does not increase in response to the power supplied during the heating mode.

[0059] For example, at least one of the one or more predetermined criteria may be that the voltage of the power supply drops below a predetermined level.

[0060] The temperature of the susceptor is preferably reduced during operation or initially reduced according to a safety mode.

[0061] The safety mode may include one or more of the steps of reducing the power supplied to the induction heating arrangement, terminating the power supplied to the induction heating arrangement, initiating another one of a number of operating modes, such as a calibration mode or a recalibration mode, and terminating the user session.

[0062] Operating in accordance with a safety mode preferably includes adjusting the power provided to the induction heating arrangement, for example adjusting the power provided to the induction heating arrangement in response to one or more overheating or cooling events.

[0063] In one embodiment, the aerosol-generating system may comprise an aerosol-generating device and an aerosol-generating article. The aerosol-generating device may comprise a power supply, a DC / AC converter, an inductor coil, and a controller. The aerosol-generating article may comprise an aerosol-forming substrate and a susceptor element, the susceptor element being configured, in use, to be inductively coupled to the inductor coil and to heat the aerosol-forming substrate. The controller may be configured to: operating in a calibration mode to calculate a range of conductance or resistance values ​​associated with the susceptor element that correspond to a desired temperature range for the susceptor element based on measurements of changes in conductance or resistance associated with the susceptor element with increasing power provided to the induction heating arrangement; providing power to the induction heating arrangement to operate in a heating mode to maintain a conductance or resistance associated with the susceptor element at a target value within a range of conductance or resistance values; operating in a recalibration mode to periodically or intermittently recalculate a range of conductance or resistance corresponding to a desired temperature range of the susceptor element based on measurements of changes in conductance or resistance with increasing power provided to the induction heating arrangement; It may be configured to operate in a safety mode to adjust the power provided to the induction heating arrangement in response to one or more overheating or cooling events.

[0064] In a preferred embodiment, the controller is programmed with instructions to implement any of a number of operational modes. The controller may include a memory containing executable instructions to implement any of a number of operational modes.

[0065] According to an embodiment of the invention, an aerosol generating device may be provided, the aerosol generating device configured for use in the aerosol generating system described herein.

[0066] According to an embodiment of the invention, an aerosol-generating article may be provided, the aerosol-generating article configured for use in the aerosol generation system described herein.

[0067] According to one embodiment of the present invention, a method for controlling an inductively heated aerosol generating system including an inductive heating arrangement having an inductor and a susceptor comprises the steps of: operating the system in a calibration mode to determine target values ​​for electrical control parameters; operating the system in a heating mode by providing power to the induction heating arrangement to maintain the susceptor at an operating temperature with reference to a target value of the electrical control parameter; periodically or intermittently operating the system in a recalibration mode to re-determine the target values ​​of the electrical control parameters; and adjusting the power provided to the induction heating arrangement in response to one or more predetermined safety criteria being met.

[0068] At least a portion of the susceptor is preferably configured to undergo a reversible phase transition, and the calibration mode includes determining upper and lower boundaries of the phase transition by heating the susceptor through a predetermined temperature range, for example, by heating the susceptor until detecting an upper boundary of the phase transition. The method may include identifying upper and lower boundary values ​​for an electrical control parameter associated with the upper and lower boundaries of the phase transition.

[0069] The method may be a method of controlling an aerosol generating system as described herein.

[0070] The term "aerosol-generating device" as used herein refers to a device that interacts with an aerosol-forming substrate to generate an aerosol. The aerosol-generating device may interact with one or both of an aerosol-generating article that includes an aerosol-forming substrate and a cartridge that includes an aerosol-forming substrate.

[0071] The term "aerosol-generating system" as used herein refers to the combination of an aerosol-generating device with an aerosol-forming substrate. When the aerosol-forming substrate forms part of an aerosol-generating article, the aerosol-generating system refers to the combination of an aerosol-generating device with an aerosol-generating article. In an aerosol-generating system, the aerosol-forming substrate and the aerosol-generating device work together to generate an aerosol.

[0072] The term "aerosol-forming substrate" as used herein refers to a substrate capable of releasing a volatile compound capable of forming an aerosol. The volatile compound may be released by heating or burning the aerosol-forming substrate. As an alternative to heating or burning, in some cases the volatile compound may be released by a chemical reaction or by mechanical stimulation such as ultrasound. The aerosol-forming substrate may be solid or may include both solid and liquid components. The aerosol-forming substrate may be part of an aerosol-generating article.

[0073] The term "aerosol-generating article" as used herein refers to an article that includes an aerosol-forming substrate capable of emitting a volatile compound capable of forming an aerosol. The aerosol-generating article may be disposable. An aerosol-generating article that includes an aerosol-forming substrate that includes tobacco may be referred to herein as a tobacco stick.

[0074] The aerosol-forming substrate may comprise nicotine. The aerosol-forming substrate may comprise tobacco, for example a tobacco-containing material containing volatile tobacco flavor compounds that are released from the aerosol-forming substrate upon heating. In a preferred embodiment, the aerosol-forming substrate may comprise homogenized tobacco material, for example cast leaf tobacco. The aerosol-forming substrate may comprise both solid and liquid components. The aerosol-forming substrate may comprise a tobacco-containing material containing volatile tobacco flavor compounds that are released from the substrate upon heating. The aerosol-forming substrate may comprise a non-tobacco material. The aerosol-forming substrate may further comprise an aerosol former. Examples of suitable aerosol formers are glycerin and propylene glycol.

[0075] As used herein, the term "mouthpiece" means that portion of an aerosol-generating article, device, or system that is placed into the mouth of a user for direct inhalation of the aerosol.

[0076] As used herein, the term "susceptor" refers to an element that includes a material capable of converting the energy of a magnetic field into heat. When the susceptor is located in an alternating magnetic field, the susceptor heats up. The heating of the susceptor can be the result of at least one of hysteresis losses and eddy currents induced in the susceptor, depending on the electrical and magnetic properties of the susceptor material.

[0077] As used herein, the term "inductively coupled" refers to heating a susceptor when penetrated by an alternating magnetic field. The heating may be caused by the generation of eddy currents in the susceptor. The heating may also be caused by magnetic hysteresis losses.

[0078] As used herein, the term "duty cycle" of a current pulse means the ratio of the pulse duration, or pulse width, to the total period over which the current pulse is delivered.

[0079] As used herein, the term "puffing" refers to the act of a user inhaling an aerosol through the user's mouth or nose and into the user's body. The present invention is defined in the claims. However, below 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 of the features of other examples, embodiments, or aspects described herein.

[0080] Example 1 1. An inductively heated aerosol generating system, comprising: an induction heating arrangement having an inductor and a susceptor; a power supply for supplying power to the induction heating arrangement; a controller configured to control power provided from the power source to the induction heating arrangement and to monitor electrical control parameters; The controller is configured to operate the aerosol generation system in a plurality of operating modes, the plurality of operating modes comprising at least: a calibration mode for determining target values ​​for electrical control parameters; a heating mode in which power is supplied to an inductor to maintain the susceptor at an operating temperature, the operating temperature being maintained by controlling the power supplied to the inductor with reference to a target value of an electrical control parameter; a recalibration mode for periodically or intermittently re-determining the target values ​​of the electrical control parameters; and and a safety mode for adjusting power provided to the induction heating arrangement in response to one or more predetermined criteria being met. Example 2 The aerosol generating system according to Example 1, wherein the plurality of operating modes further includes a pre-heating mode for increasing the temperature of the susceptor to a predetermined temperature before operating in a different operating mode, such as a calibration mode or a heating mode. Example 3 An aerosol generation system according to any of the preceding embodiments, wherein at least a portion of the susceptor is configured to undergo a reversible phase transition when heated or cooled through a predetermined temperature range. Example 3a. An aerosol generating system according to Example 3, wherein the controller is configured to identify upper and lower boundary values ​​of an electrical control parameter associated with the upper and lower boundaries of the phase transition. Example 3b. An aerosol generating system according to Example 3a, wherein the target value of the electrical control parameter is set to a value between an upper boundary value and a lower boundary value. Example 4 An aerosol generation system according to Example 3, 3a or 3b, wherein during the calibration mode, the controller is configured to perform the steps of heating the susceptor through a predetermined temperature range, allowing the susceptor to cool through a predetermined temperature range, monitoring the electronic control parameter, identifying upper and lower boundary values ​​of the electronic control parameter associated with upper and lower boundaries of the phase transition, and determining a target value for the electronic control parameter. Example 5 An aerosol generating system according to any of Examples 3-4, wherein during the calibration mode, the controller is configured to perform the steps of heating the susceptor, monitoring the electrical control parameter while heating the susceptor, identifying upper and lower boundary values ​​of the electrical control parameter associated with upper and lower boundaries of the phase transition, allowing the susceptor to cool through a predetermined temperature range, monitoring the electrical control parameter while allowing the susceptor to cool, and determining a target value for the electrical control parameter. Example 6 An aerosol generation system according to any of the previous embodiments, wherein the step of heating the susceptor involves supplying power to an inductive heating arrangement. Example 7 An aerosol generation system according to any of Examples 4 to 6, wherein the power supplied to heat the susceptor during the calibration mode is supplied at a duty cycle of more than 80%, such as more than 90%, such as 100%. Example 8 An aerosol generation system according to any of Examples 4-7, wherein the step of allowing the susceptor to cool involves powering the induction heating arrangement at a reduced duty cycle and monitoring electrical control parameters. Example 9 An aerosol generating system according to any of Examples 4 to 8, wherein the step of allowing the susceptor to cool involves supplying power to the induction heating arrangement as pulses of energy, e.g. pulses of current, e.g. pulses of energy having a duty cycle of less than 10%, e.g. less than 2% or less than 1%, and monitoring the value of the electrical control parameter during each of the pulses. Example 10 An aerosol generation system according to any of the preceding embodiments, wherein the susceptor is located and / or positionable within an alternating electromagnetic field generated by the inductor. Example 11 An aerosol generation system according to any of the preceding embodiments, wherein the susceptor is configured to undergo a reversible phase transition when heated through a predetermined temperature range, and wherein a phase transition start point and a phase transition end point are identifiable by a change in the value of an electrical control parameter as the susceptor is heated through the predetermined temperature range, e.g., when the susceptor is heated according to a calibration protocol during a calibration mode. Example 12 An aerosol generating system according to Example 11, wherein the target value of the electrical control parameter is determined to be between the values ​​of the electrical control parameter at the phase transition start point and the phase transition end point. Example 13 An aerosol generating system according to any of Examples 3-12, wherein the induction heating arrangement exhibits a reversal of apparent resistance while undergoing a phase transition. Example 14 An aerosol generating system according to any of Examples 3-13, wherein the induction heating arrangement exhibits a reversal of apparent conductance while undergoing a phase transition. Example 15 An aerosol generating system according to any of Examples 3-14, wherein the apparent resistance of the induction heating system increases before the onset of the phase transition, decreases upon heating through the phase transition, and increases upon heating beyond the end of the phase transition. Example 16 An aerosol generating system according to any of Examples 3-15, wherein the apparent conductance of the inductively heated system decreases before the onset of the phase transition, increases upon heating through the phase transition, and decreases upon heating beyond the end of the phase transition. Example 17 An aerosol generation system according to any of the preceding embodiments, wherein the electrical control parameter is indicative of the temperature of the susceptor and / or indicative of a material property of the susceptor that varies as a function of temperature, and / or the electrical control parameter is a parameter that varies as a function of the temperature of the susceptor. Example 18 An aerosol generation system according to any of the preceding embodiments, wherein the electrical control parameter is a parameter selected from the list consisting of the electrical resistance of the susceptor, the apparent electrical resistance of the induction heating arrangement, the electrical conductance of the susceptor, the apparent electrical conductance of the induction heating arrangement, the current supplied to the induction heating arrangement, and the power supplied to the induction heating arrangement. Example 19 An aerosol generation system according to any of the preceding embodiments, wherein the controller is configured to monitor at least one power parameter indicative of power supplied to the induction heating arrangement during operation. Example 20 An aerosol generating system according to Example 19, wherein at least one power parameter is used as an electrical control parameter or at least one power parameter is used to derive an electrical control parameter. Example 21 An aerosol generation system according to embodiment 19 or 20, wherein at least one power parameter is or includes a current supplied to the induction heating arrangement during operation. Example 22 An aerosol generation system according to any of Examples 19-21, wherein at least one power parameter is or includes a voltage across the inductive heating arrangement during operation. Example 23 An aerosol generating system according to any of the previous embodiments, wherein the system comprises an aerosol generating article and an aerosol generating device configured to receive the aerosol generating article. Example 24 24. An aerosol-generating system according to Example 23, wherein the aerosol-generating article comprises an aerosol-forming substrate, and the susceptor is disposed in thermal communication with the aerosol-forming substrate. Example 25 25. An aerosol generating system according to embodiment 23 or 24, wherein the aerosol generating article is a disposable article. Example 26 An aerosol generation system according to any of Examples 23 to 25, wherein the aerosol generation device comprises an inductor, a controller, and a power supply for providing power to the controller. Example 27 An aerosol generation system according to Example 26, wherein the aerosol generation device further comprises a DC / AC converter that converts the direct current provided by the power supply into alternating current for powering the inductor. Example 28 An aerosol generation system according to any of the previous embodiments, comprising an aerosol generation device configured to inductively heat an aerosol-forming substrate to generate an inhalable aerosol during a session of use. Example 29 An aerosol generating system according to any of Examples 23-28, wherein the aerosol generating device is further configured to detect when an aerosol-generating article is received within the aerosol generating device. Example 30 An aerosol generating system according to Example 29, wherein the aerosol generating device is further configured to determine whether an aerosol generating article received within the aerosol generating device is an article configured for use with the aerosol generating device, and preferably, operation of the aerosol generating device to heat the aerosol generating article is prevented if a detected article is not configured for use with the aerosol generating device. Example 31 An aerosol generating system according to any one of Examples 3 to 30, wherein the phase transition is a magnetic phase transition or a crystalline phase transition. Example 32 32. The aerosol generating system according to Example 31, wherein the phase transition is a ferromagnetic / paramagnetic phase transition, or a ferrimagnetic / paramagnetic phase transition, or an antiferromagnetic / paramagnetic phase transition. Example 33 An aerosol generating system according to any of the preceding embodiments, wherein the susceptor comprises a first material that does not undergo a reversible phase transition when heated through a predetermined temperature range, and a second material that does not undergo a reversible phase transition when heated through a predetermined temperature range, preferably the predetermined temperature range being between 100°C and 500°C, for example between 200°C and 400°C. Example 34 An aerosol generating system according to Example 33, wherein the first material comprises more than 50% by volume of the susceptor, preferably more than 60% by volume, or more than 70% by volume, or more than 80% by volume, or more than 90% by volume, or more than 95% by volume. Example 35 The aerosol generating system according to example 33 or 34, wherein the first material is an iron-based alloy, such as stainless steel. Example 36 The aerosol generating system according to any of Examples 33-35, wherein the second material is nickel or a nickel-based alloy. Example 37 An aerosol generation system according to any of the preceding embodiments, wherein the susceptor is formed as a single component, for example as an elongated pin, blade, wire or strip, or as a sheet or mesh. Example 38 An aerosol generation system according to any of the preceding embodiments, wherein the susceptor is an elongated susceptor having a length dimension greater than its width or thickness dimension. Example 39 An aerosol generation system according to any of the preceding embodiments, wherein the susceptor has a rectangular cross-section or a circular cross-section. Example 40 The aerosol generation system according to any of the preceding embodiments, wherein the susceptor has a length of from 8 mm to 100 mm, such as from 10 mm to 30 mm, such as from 12 mm to 20 mm. Example 41 The aerosol generation system according to any of the preceding embodiments, wherein the susceptor has a width of from 2mm to 6mm, such as from 3mm to 5mm, such as from 3.5mm to 4.5mm. Example 42 The aerosol generation system according to any of the preceding embodiments, wherein the susceptor has a thickness of 0.1 mm to 2 mm, such as 0.2 mm to 1.5 mm, such as 0.4 mm to 1 mm. Example 43 The aerosol generating system according to any of the preceding examples, wherein the susceptor is formed from a plurality of individual components, e.g., from a plurality of elongated pins, blades, wires, or strips, from a plurality of sheets or meshes, or from a plurality of particles, e.g., the susceptor may be formed from a plurality of particles disposed in thermal contact with or within the aerosol-forming substrate. Example 44 An aerosol generation system according to any of the preceding embodiments, wherein the power source may be a DC power source, e.g., a battery located within the aerosol generation device, and the aerosol generation device further comprises a DC to AC converter, e.g., a DC to AC inverter, for supplying AC power to the inductor. Example 45 An aerosol generating system according to any of Examples 3 to 44, wherein the apparent resistance of the induction heating arrangement exhibits a positive relationship with the temperature just below the lower boundary of the phase transition and just above the upper boundary of the phase transition, and a negative relationship with the temperature between the upper and lower boundaries of the phase transition. Example 46 An aerosol generating system according to any of Examples 3 to 44, wherein the apparent conductance of the induction heating arrangement exhibits a negative relationship with the temperature just below the lower boundary of the phase transition and just above the upper boundary of the phase transition, and a positive relationship with the temperature between the upper and lower boundaries of the phase transition. Example 47 An aerosol generating system according to any of Examples 3 to 46, wherein the operating temperature during the heating mode is a temperature between the upper and lower boundaries of the phase transition, i.e., the start of the phase transition and the end of the phase transition. Example 48 An aerosol generation system according to any of the preceding embodiments, wherein the heating mode is configured to maintain a temperature of the susceptor according to a predetermined temperature profile. Example 49 An aerosol generation system according to any of the preceding embodiments, wherein the power supplied to the inductor during the heating mode is supplied as power pulses, e.g. pulses of current, and the temperature of the susceptor is controlled by varying the duty cycle of the inductor. Example 50 An aerosol generating system according to Example 49, wherein the controller is configured to control the temperature of the susceptor during the heating mode by reference to a target value of the apparent resistance of the induction heating arrangement, and the target value of the apparent resistance is determined during the calibration mode or recalibration mode. Example 51 An aerosol generating system according to Example 49, wherein the controller is configured to control the temperature of the susceptor during the heating mode by referring to a target value of the apparent conductance of the induction heating arrangement, and the target value of the apparent conductance is determined during the calibration mode or recalibration mode. Example 52 An aerosol generating system according to any of Examples 3 to 51, wherein an electrical control parameter is monitored during heating mode to verify that the value of the electrical control parameter is between upper and lower boundary values ​​of the electrical control parameter associated with the upper and lower boundaries of the phase transition, and if this cannot be verified, the device enters a safety mode. Example 53 An aerosol generating system according to any of Examples 3 to 52, wherein the response of the electrical control parameters to the power supplied to the induction heating arrangement, e.g., a power pulse supplied to the induction heating arrangement, is monitored during the heating mode to verify that the susceptor is within the operating temperature range, and if this cannot be verified, the apparatus enters a safety mode. Example 54 An aerosol generation system according to any of the preceding embodiments, wherein the safety mode involves a reduction in the power supplied to the induction heating arrangement, e.g., a reduction in the duty cycle supplied to the inductor, for a period sufficient to allow the susceptor to cool, e.g., to a temperature below the lower boundary of the phase transition. Example 55 An aerosol generation system according to any of the preceding embodiments, wherein the aerosol generating device comprises a puff sensor for determining a user puff, e.g. an airflow sensor or a temperature sensor such as a thermistor mounted in the airflow path of the aerosol generating device. Example 56 An aerosol generation system according to Example 55, wherein the heating mode includes a non-puff heating regime and a puff heating regime, and the controller is configured to operate according to the puff heating regime when it is detected that the user is puffing during the heating mode, and to operate according to the non-puff heating regime when it is not detected that the user is puffing during the heating mode. Example 57 An aerosol generating device according to Example 56, wherein the controller applies a limit to the power supplied to the induction heating arrangement during the smoke suction heating regime, for example by limiting the duty cycle to 50% of the maximum duty cycle, or 60% of the maximum duty cycle, or 70% of the maximum duty cycle, or 80% of the maximum duty cycle. Example 58 An aerosol generating device according to any of Examples 55 to 57, wherein the calibration mode or recalibration mode is terminated if it is determined that the user takes a puff while operating in the calibration mode or recalibration mode. Example 59 An aerosol generating device according to any of Examples 55 to 58, wherein the controller prevents or delays initiation of the recalibration mode if it is determined that the user is taking a puff. Example 60 The aerosol generation system according to any of the preceding embodiments may include a temperature sensor located outside the airflow path, such as a thermocouple or thermistor mounted on a PCB of the aerosol generation device, or a thermocouple or thermistor mounted within a substrate receiving cavity of the aerosol generation device, to monitor temperature, e.g., the temperature of the aerosol generation device. Example 61 An aerosol generating system according to Example 60, wherein the device is configured to operate according to a safety mode if the temperature of a portion of the device is determined to be outside a predetermined range, or to terminate operation if the temperature of a portion of the device is determined to be outside a predetermined range. Example 62 An aerosol generation system according to any of the preceding embodiments, wherein the controller is configured to interrupt the heating mode and perform a recalibration according to the recalibration mode, and preferably, if the recalibration is successfully performed, the heating mode is resumed. Example 63 An aerosol generation system according to any of the preceding embodiments, wherein the recalibration mode is performed periodically based on one or more criteria of a predetermined duration, a predetermined number of user puffs, a predetermined number of temperature steps, and a measured power supply voltage. Example 64 An aerosol generation system according to any of the preceding embodiments, wherein one or more predetermined criteria for the safety mode, e.g., safety criteria or safety triggers, are criteria set in relation to an operational event or a monitored operational parameter, and the controller is configured to implement the safety mode in response to the one or more predetermined criteria being satisfied. Example 65 An aerosol generating system according to Example 64, wherein at least one of the one or more predetermined criteria is that the temperature of an electronic component of the aerosol generating system exceeds a predetermined temperature, for example, that the temperature of a PCB of the aerosol generating system exceeds a predetermined temperature, for example, greater than 50°C, or 60°C, or 70°C, or 80°C, or 100°C, and preferably the temperature of the electronic component is monitored by a temperature sensor mounted on or near the electronic component. Example 66 An aerosol generating system according to Example 64 or 65, wherein at least one of the one or more predetermined criteria is that the temperature of the substrate receiving cavity or chamber of the aerosol generating system exceeds a predetermined temperature, e.g., the temperature of the heated chamber of the aerosol generating device exceeds a predetermined temperature, e.g., greater than 400°C, or 410°C, or 450°C, or 480°C, and preferably the temperature of the substrate receiving cavity or chamber is monitored by a temperature sensor mounted on or near the substrate receiving cavity or chamber. Example 67 An aerosol generating system according to any of Examples 64 to 66, wherein at least one of the one or more predetermined criteria is that the temperature of the susceptor exceeds a maximum operating temperature, for example, greater than 400°C, or 410°C, or 450°C, or 480°C. Example 68 An aerosol generating system according to any of Examples 64 to 67, wherein at least one of the one or more predetermined criteria is that the temperature of the susceptor exceeds the Curie temperature of a material component of the susceptor. Example 69 An aerosol generating system according to any of Examples 64 to 68, wherein at least one of the one or more predetermined criteria is that the response of the electrical control parameters to the power supplied to the induction heating arrangement during the heating mode does not satisfy a predetermined condition, e.g., the apparent conductance of the induction heating arrangement does not increase in response to the power supplied during the heating mode. Example 70 An aerosol generation system according to any of Examples 64 to 69, wherein at least one of the one or more predetermined criteria is that the voltage of the power supply drops below a predetermined level. Example 71 An aerosol generating system according to any of Examples 64-70, wherein the temperature of the susceptor is reduced during the safety mode. Example 72 An aerosol generating system according to any of Examples 64 to 71, wherein the safety mode may include one or more of the following steps: reducing the power supplied to the induction heating arrangement, terminating the power supplied to the induction heating arrangement, initiating another one of a plurality of operating modes, such as a calibration mode or a recalibration mode, and terminating the user session. Example 73 An aerosol generation system according to any of the preceding embodiments, wherein operating in a safety mode includes adjusting the power provided to the induction heating arrangement, for example adjusting the power provided to the induction heating arrangement in response to one or more overheating or cooling events. Example 74 an aerosol generating device for receiving the aerosol generating article to generate an aerosol; The aerosol generating device is an inductor coupleable to a power source; A controller, The aerosol-generating article is an aerosol-forming substrate; a susceptor in thermal communication with the aerosol-forming substrate, at least a portion of the susceptor configured to undergo a reversible phase transition when heated or cooled through a predetermined temperature range; The aerosol generating device is (a) operating in a calibration mode in which power is supplied to an inductor to generate an alternating magnetic field for heating a susceptor through a predetermined temperature range, and an electrical control parameter is monitored to identify a start and end of a phase transition, the start of the phase transition being a transition start point and the end of the phase transition being a transition end point; (b) operating in a heating mode in which power is supplied to the inductor to maintain the susceptor within an operating temperature range for generating an aerosol from the aerosol-forming substrate, the operating temperature range being maintained by controlling the power supplied to the inductor with reference to at least one of a transition start point and a loading end point determined during the calibration mode and / or with reference to a target value of an electrical control parameter determined during the calibration mode; (c) operating a recalibration mode at predetermined intervals during the duration of the heating mode to update the transition start and end point values ​​used and / or to update the target values ​​of the electrical control parameters; (d) operating in a safety mode if one or more predetermined criteria for initiating the safety mode are met. Example 75 The method includes the steps of: The aerosol generating device includes a power supply, a DC / AC converter, an inductor coil, and a controller; an aerosol-generating article comprising an aerosol-forming substrate and a susceptor element, the susceptor element being configured, in use, to be inductively coupled to an inductor coil and to heat the aerosol-forming substrate; The controller operating in a calibration mode to calculate a range of conductance or resistance values ​​associated with the susceptor element that correspond to a desired temperature range for the susceptor element based on measurements of changes in conductance or resistance associated with the susceptor element with increasing power provided to the induction heating arrangement; providing power to the induction heating arrangement to operate in a heating mode to maintain a conductance or resistance associated with the susceptor element at a target value within a range of conductance or resistance values; operating in a recalibration mode to periodically or intermittently recalculate a range of conductance or resistance corresponding to a desired temperature range of the susceptor element based on measurements of changes in conductance or resistance with increasing power provided to the induction heating arrangement; An aerosol generation system according to any of the preceding embodiments, configured to operate in a safety mode and adjust the power provided to the induction heating arrangement in response to one or more overheating or cooling events. Example 76 An aerosol generation system according to any of the preceding embodiments, wherein the controller is programmed with instructions to implement any of a plurality of operating modes, e.g., the controller includes a memory including executable instructions to implement any one of the plurality of operating modes. Example 77 13. An aerosol generating device configured for use in an aerosol generating system as defined in any of the preceding embodiments. Example 78 An aerosol-generating article configured for use in an aerosol-generating system as defined in any one of Examples 1 to 76. Example 79 1. A method for controlling an inductively heated aerosol generating system comprising an inductive heating arrangement having an inductor and a susceptor, the method comprising: operating the system in a calibration mode to determine target values ​​for electrical control parameters; operating the system in a heating mode by providing power to the induction heating arrangement to maintain the susceptor at an operating temperature with reference to a target value of the electrical control parameter; periodically or intermittently operating the system in a recalibration mode to re-determine the target values ​​of the electrical control parameters; and adjusting the power provided to the induction heating arrangement in response to one or more predetermined safety criteria being met. Example 80 A method according to example 79, wherein at least a portion of the susceptor is configured to undergo a reversible phase transition, and the calibration mode includes a step of determining upper and lower boundaries of the phase transition by heating the susceptor through a predetermined temperature range, for example, by heating the susceptor until an upper boundary of the phase transition is detected. Example 81 The method according to example 80, comprising identifying upper and lower boundary values ​​of an electrical control parameter associated with the upper and lower boundaries of the phase transition. Example 82 A method for controlling an inductively heated aerosol generating system according to any one of Examples 79 to 81, the system comprising an aerosol generating article and an aerosol generating device for receiving the aerosol generating article to generate an aerosol; The aerosol generating device is an inductor coupleable to a power source; A controller, The aerosol-generating article is an aerosol-forming substrate; a susceptor in thermal communication with the aerosol-forming substrate, the susceptor being configured such that at least a portion of the susceptor undergoes a reversible phase transition when heated or cooled through a predetermined temperature range; The method is (a) operating the apparatus in a calibration mode in which power is provided to an inductor to generate an alternating magnetic field for heating the susceptor through a predetermined temperature range and monitoring power supply parameters to identify the start and end of a phase transition of the susceptor, the start of the phase transition being a transition initiation point and the end of the phase transition being a transition endpoint; (b) after completion of the configuration mode, operating in a heating mode in which power is supplied to the inductor to maintain the susceptor within an operating temperature range to generate an aerosol from the aerosol-forming substrate, wherein a predetermined thermal profile is maintained by controlling the power supplied to the inductor with reference to at least one of a transition start point and an end point, or a target derived from at least one of a transition start point and an end point determined during the calibration mode; (c) switching to a recalibration mode at predetermined intervals during the progress of the heating mode to update the transition start and end point values ​​used during the continuation of the heating mode; (d) detecting one or more signals related to a predetermined safety criterion; (e) initiating a safety mode in which power provided to the induction heating arrangement is adjusted in response to the detected signal. Example 83 The method according to any of Examples 79-82, further comprising the step of detecting that the aerosol-generating article has been received within the aerosol generating device. Example 84 The method according to any of Examples 79 to 83, further comprising a step of determining whether an aerosol-generating article received within the aerosol generating device is an article configured for use with the aerosol generating device, and preferably a step of preventing operation of the aerosol generating device to heat the aerosol-generating article if the detected article is not an article configured for use with the aerosol generating device. Example 85 The method according to any of Examples 79-84, wherein the heating mode involves maintaining the temperature of the susceptor within the operating temperature range according to a predetermined temperature profile. Example 86 1. A method of controlling an aerosol generation system, the system comprising an inductive heating arrangement including a susceptor element and an inductor coil, and a power source for providing power to the inductive heating arrangement as current pulses, the method comprising: calculating a range of conductance or resistance values ​​associated with the susceptor element that corresponds to a desired temperature range of the susceptor based on measurements of changes in conductance or resistance associated with the susceptor element with increasing power provided to the induction heating arrangement; providing power to the induction heating arrangement to maintain a conductance or resistance associated with the susceptor element at a target value within a range of conductance or resistance values; periodically or intermittently recalculating a range of conductance or resistance corresponding to a desired temperature range of the susceptor element based on measurements of changes in conductance or resistance with increasing power provided to the induction heating arrangement; and adjusting power provided to the induction heating arrangement in response to one or more heating or cooling events. Example 87 The method according to example 86, wherein the step of calculating a range of conductance or resistance values ​​associated with the susceptor element corresponding to a desired temperature range of the susceptor element includes detecting a range of conductance values ​​in which the conductance increases as the temperature of the susceptor increases. Example 88 The method according to example 86 or 87, wherein the step of calculating a range of conductance or resistance values ​​associated with the susceptor element corresponding to a desired temperature range of the susceptor element includes operating in a first calibration mode in which maximum power is provided to the induction heating arrangement until a maximum conductance value is reached. Example 89 The method according to any of Examples 86-88, wherein the step of calculating a range of conductance or resistance values ​​associated with the susceptor element corresponding to a desired temperature range for the susceptor element includes operating in a second calibration mode in which power is provided to the induction heating arrangement at a low duty cycle until a maximum conductance value is reached. Example 90 The method according to any of Examples 86-89, wherein providing power to the induction heating arrangement to maintain a conductance or resistance associated with the susceptor element at a target value includes operating in a heating mode in which a duty cycle of current pulses provided to the induction heating arrangement is adjusted to adjust the conductance or resistance toward the target conductance or resistance. Example 91 The method according to any of Examples 86-90, wherein adjusting the power provided to the induction heating arrangement in response to one or more overheating or cooling events includes detecting a cooling event that may cool the susceptor element, determining a maximum duty cycle limit of the current pulse during the cooling event, and increasing the duty cycle of the current pulse to a duty cycle that is less than or equal to the maximum duty cycle limit to compensate for the cooling event. Example 92 The method according to any of Examples 86-91, wherein adjusting the power provided to the induction heating arrangement in response to one or more overheating or cooling events includes detecting an overheating event and reducing the duty cycle of the current pulse in response to the detected overheating event. Example 93 The method according to any of Examples 86-92, wherein the aerosol generating system comprises an aerosol generating device and an aerosol generating article, the power supply and inductor coil being part of the aerosol generating device, and the susceptor element being part of the aerosol generating article. Example 94 The method according to example 92 or 93, wherein the overheating event is overheating of the apparatus or overheating of the susceptor. Example 95 The method according to any of Examples 86-94, wherein the power supply includes a DC / AC converter and the conductance or resistance value associated with the susceptor is determined from a DC supply voltage of the power supply and from a DC current drawn from the power supply. Example 96 A method of controlling an aerosol-generating system as defined in any of Examples 79-95 using an aerosol-generating system as defined in any of Examples 1-76. [Brief description of the drawings]

[0081] The embodiments will now be further described with reference to the following figures:

[0082] [Figure 1] FIG. 1 shows a schematic cross-sectional view of an aerosol-generating article. [Figure 2A]FIG. 2A shows a schematic cross-sectional view of an aerosol generating device for use with the aerosol-generating article shown in FIG. [Figure 2B] FIG. 2B shows a schematic cross-sectional view of an aerosol generating device that engages with the aerosol-generating article shown in FIG. [Diagram 3] FIG. 3 is a block diagram showing an induction heating device for the aerosol generating device described in relation to FIG. [Figure 4] FIG. 4 is a schematic diagram showing the electronic components of the induction heating device described in relation to FIG. [Diagram 5] FIG. 5 is a schematic diagram of an inductor of an LC load network of the induction heating device described in relation to FIG. [Figure 6] FIG. 6 is a graph of DC current versus time illustrating the remotely detectable change in electrical current that occurs as the susceptor material undergoes a phase transition associated with its Curie point. [Figure 7] FIG. 7 is a graph of apparent conductance versus time showing the change in remotely detectable current that occurs as the susceptor material undergoes a phase transition associated with its Curie point. [Figure 8] FIG. 8 is a graph showing the shift in the apparent conductance curve as the susceptor moves in position relative to the conductor. [Figure 9] FIG. 9 illustrates the effect that a shift in the apparent conductance curve can have on the temperature control of a system. [Figure 10] FIG. 10 is a schematic diagram showing the control of an aerosol generation system in multiple operational modes. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0083] Figure 1 shows an aerosol-generating article 100 for use in an aerosol-generating system. The aerosol-generating article 100 shown in Figure 1 comprises a rod of aerosol-generating substrate 12 and a downstream section 14 located downstream of the rod of aerosol-generating substrate 12. The aerosol-generating article 100 further comprises an upstream section 16 located upstream of the rod of aerosol-generating substrate 12. The aerosol-generating article 100 thus extends from an upstream or distal end 18 to a downstream or oral end 20.

[0084] The downstream section 14 comprises a support element 22 located immediately downstream of the rod 12 of the aerosol-generating substrate, the support element 22 being in longitudinal alignment with the rod 12. In the embodiment of Figure 1, the upstream end of the support element 22 abuts the downstream end of the rod 12 of the aerosol-generating substrate. In addition, the downstream section 14 comprises an aerosol cooling element 24 located immediately downstream of the support element 22, the aerosol cooling element 24 being in longitudinal alignment with the rod 12 and the support element 22. In the embodiment of Figure 1, the upstream end of the aerosol cooling element 24 abuts the downstream end of the support element 22.

[0085] The support element 22 and the aerosol cooling element 24 together define an intermediate hollow section 50 of the aerosol-generating article 100. Taken as a whole, the intermediate hollow section 50 does not contribute substantially to the overall RTD of the aerosol-generating article.

[0086] The support element 22 comprises a first hollow tubular segment 26. The first hollow tubular segment 26 is provided in the form of a hollow cylindrical tube made of cellulose acetate. The first hollow tubular segment 26 defines an interior cavity 28 that extends entirely from an upstream end 30 of the first hollow tubular segment to a downstream end 32 of the first hollow tubular segment 26. The interior cavity 28 is substantially empty, thereby permitting substantially unrestricted air flow therealong.

[0087] The first hollow tubular segment 26 has a length of about 8 millimeters, an outer diameter of about 7.25 millimeters, and an inner diameter (DFTS ), the peripheral wall thickness of the first hollow tubular segment 26 is therefore approximately 2.67 millimeters.

[0088] The aerosol cooling element 24 includes a second hollow tubular segment 34. The second hollow tubular segment 34 is provided in the form of a hollow cylindrical tube made of cellulose acetate. The second hollow tubular segment 34 defines an interior cavity 36 that extends from an upstream end 38 of the second hollow tubular segment all the way to a downstream end 40 of the second hollow tubular segment 34. The interior cavity 36 is substantially empty, thereby permitting substantially unrestricted airflow therealong.

[0089] The second hollow tubular segment 34 has a length of about 8 millimeters, an outer diameter of about 7.25 millimeters, and an inner diameter (D STS ) The peripheral wall thickness of the second hollow tubular segment 34 is therefore approximately 2 millimeters.

[0090] The aerosol-generating article 100 includes a ventilation zone 60 provided at a location along the second hollow tubular segment 34. More specifically, the ventilation zone is provided approximately 2 millimeters from the upstream end of the second hollow tubular segment 34. The ventilation level of the aerosol-generating article 100 is approximately 25 percent.

[0091] 1, the downstream section 14 further comprises a mouthpiece element 42 located downstream of the intermediate hollow section 50. More specifically, the mouthpiece element 42 is positioned immediately downstream of the aerosol cooling element 24. As shown in the drawing of FIG.

[0092] Mouthpiece element 42 is provided in the form of a cylindrical plug of low density cellulose acetate. Mouthpiece element 42 has a length of about 12 millimeters and an outside diameter of about 7.25 millimeters.

[0093] The rod 12 comprises an aerosol-generating substrate of one of the types described above. The rod 12 of aerosol-generating substrate has an outer diameter of about 7.25 millimeters, and a length of about 12 millimeters.

[0094] The aerosol-generating article 100 further comprises an elongated susceptor element 44 within the rod 12 of the aerosol-generating substrate. More specifically, the susceptor element 44 is disposed substantially longitudinally within the aerosol-generating substrate such that the susceptor element 44 is generally parallel to the longitudinal direction of the rod 12. As shown in the drawing of Figure 1, the susceptor element 44 is positioned at a radially central location within the rod and effectively extends along the longitudinal axis of the rod 12.

[0095] The susceptor element 44 extends completely from the upstream end to the downstream end of the rod 12. In practice, the susceptor element 44 has substantially the same length as the rod 12 of the aerosol-generating substrate.

[0096] In the embodiment of Fig. 1, the susceptor element 44 is provided in the form of a strip, having a length of about 12 millimeters, a thickness of about 60 micrometers, and a width of about 4 millimeters. The upstream section 16 comprises an upstream element 46 located immediately upstream of the rod 12 of the aerosol-generating substrate, the upstream element 46 being longitudinally aligned with the rod 12. In the embodiment of Fig. 1, the downstream end of the upstream element 46 abuts the upstream end of the rod 12 of the aerosol-generating substrate. This advantageously prevents the susceptor element 44 from becoming dislodged. Furthermore, this ensures that a consumer cannot accidentally come into contact with the heated susceptor element 44 after use.

[0097] The upstream element 46 is provided in the form of a cylindrical plug of cellulose acetate surrounded by a rigid wrapper. The upstream element 46 has a length of approximately 5 millimeters.

[0098] The susceptor 44 includes at least two different materials. The susceptor 44 includes at least two layers, a first layer of a first susceptor material disposed in physical contact with a second layer of a second susceptor material. The first susceptor material and the second susceptor material may each be a material that undergoes a Curie transition and therefore each may have a Curie temperature. In this case, the Curie temperature of the second susceptor material is lower than the Curie temperature of the first susceptor material. The first material may not undergo a Curie transition and may not have a Curie temperature. The first susceptor material may be aluminum, iron or stainless steel. The second susceptor material may be nickel or a nickel alloy. The susceptor 44 may be formed by electroplating at least one patch of the second susceptor material onto a strip of the first susceptor material. The susceptor may be formed by coating a strip of the second susceptor material onto a strip of the first susceptor material.

[0099] In use, air is drawn through the aerosol-generating article 100 by a user from the distal end 18 to the oral end 20. The distal end 18 of the aerosol-generating article 100 may also be described as the upstream end of the aerosol-generating article 100, and the oral end 20 of the aerosol-generating article 100 may also be described as the downstream end of the aerosol-generating article 100. Elements of the aerosol-generating article 100 located between the oral end 20 and the distal end 18 may be described as being upstream of the oral end 20, or alternatively downstream of the distal end 18. The aerosol-forming substrate 12 is located at the distal or upstream end 18 of the aerosol-generating article 100.

[0100] The aerosol-generating article 100 shown in Figure 1 is designed to engage with an aerosol-generating device of an aerosol generation system, such as the aerosol-generating device 200 shown in Figure 2A, to generate an aerosol. The aerosol-generating device 200 includes a housing 210 having a cavity 220 configured to receive the aerosol-generating article 100. The aerosol-generating device 200 further includes an induction heating device 230 configured to heat the aerosol-generating article 100 to generate an aerosol. Figure 2B shows the aerosol-generating device 200 when the aerosol-generating article 100 is inserted into the cavity 220.

[0101] The induction heating device 230 is shown as a block diagram in Figure 3. The induction heating device 230 comprises a DC power supply 310 and a heating arrangement 320 (also referred to as power electronics). The heating arrangement includes a controller 330, a DC / AC converter 340, a matching network 350, and an inductor 240.

[0102] The DC power supply 310 is configured to provide DC power to the heating arrangement 320. Specifically, the DC power supply 310 provides a DC supply voltage (V DC ) and DC current (I DC ) to the DC / AC converter 340. The power source 310 is preferably a battery, such as a lithium ion battery. Alternatively, the power source 310 may be another form of charge storage device, such as a capacitor. The power source 310 may require recharging. For example, the power source 310 may have a capacity sufficient to allow continuous generation of aerosol for approximately six minutes, or a multiple of six minutes. In another example, the power source 310 may have a capacity sufficient to allow a predetermined number of puffs, or discontinuous activation of the heating arrangement.

[0103] The DC / AC converter 340 is configured to supply the inductor 240 with a high frequency alternating current. As used herein, the term "high frequency alternating current" refers to an alternating current having a frequency of about 500 kilohertz to about 30 megahertz. The high frequency alternating current may have a frequency of about 1 megahertz to about 30 megahertz (such as about 1 megahertz to about 10 megahertz, or about 5 megahertz to about 8 megahertz).

[0104] 4 shows diagrammatically the electrical components of the induction heating device 230, in particular the DC / AC converter 340. The DC / AC converter 340 preferably comprises a class E power amplifier. The class E power amplifier comprises a field effect transistor 420, a transistor switch 410, e.g. comprising a metal oxide semiconductor field effect transistor, a transistor switch supply circuit, indicated by arrow 430, for supplying a switching signal (gate-source voltage) to the field effect transistor 420, and an LC load network 440 comprising a series connection of a shunt capacitor C1 and a capacitor C2, corresponding to the inductor 240, and an inductor L2. Furthermore, a DC power supply 310 with a choke L1 is connected to the inductor 240 to supply a DC current I DC along with the DC supply voltage V DC The ohmic resistance of inductor L2, R Coil and the ohmic resistance R of the susceptor 44. load 4. An ohmic resistance R, which represents a total ohmic load 450, is shown in more detail in FIG.

[0105] Although DC / AC converter 340 is shown as including a class E power amplifier, it should be understood that DC / AC converter 340 may use any suitable circuit for converting DC current to AC current. For example, DC / AC converter 340 may include a class D power amplifier including two transistor switches. As another example, DC / AC converter 340 may include a full-bridge power inverter having four switching transistors acting in pairs.

[0106] Returning to Figure 3, the inductor 240 may receive the AC current from the DC / AC converter 340 through a matching network 350 for optimal matching to the load, although the matching network 350 is not required. The matching network 350 may comprise a small matching transformer. The matching network 350 may improve the efficiency of the power transfer between the DC / AC converter 340 and the inductor 240.

[0107] As shown in FIG. 2A, the inductor 240 is located adjacent to the distal portion 225 of the cavity 220 of the aerosol generating device 200. Thus, during operation of the aerosol generating device 200, a high frequency alternating current supplied to the inductor 240 causes the inductor 240 to generate a high frequency alternating magnetic field in the distal portion 225 of the aerosol generating device 200. The alternating magnetic field has a frequency preferably between 1 and 30 megahertz, preferably between 2 and 10 megahertz, for example between 5 and 7 megahertz. As can be seen from FIG. 2B, when the aerosol generating article 100 is inserted into the cavity 200, the aerosol-forming substrate 12 of the aerosol generating article 100 is located adjacent to the inductor 240 such that the susceptor 44 of the aerosol generating article 100 is located within this alternating magnetic field. When the alternating magnetic field penetrates the susceptor 44, the alternating magnetic field causes the susceptor 44 to heat up. For example, eddy currents are generated within the susceptor 44 which, as a result, is heated. Further heating is provided by magnetic hysteresis losses within the susceptor 44. The heated susceptor 44 heats the aerosol-forming substrate 12 of the aerosol-generating article 100 to a temperature sufficient to form an aerosol. The aerosol is drawn downstream through the aerosol-generating article 100 and inhaled by the user.

[0108] The controller 330 may be a microcontroller, preferably a programmable microcontroller. The controller 330 is programmed to regulate the power supply from the DC power supply 310 to the induction heating arrangement 320 to control the temperature of the susceptor 44. The controller is programmed to regulate the power supply to control the aerosol generation system according to a number of different operating modes. The controller may receive inputs from a smoke puff sensor 360 and from one or more temperature sensors, as described.

[0109] FIG. 6 illustrates the DC current I drawn from the power supply 310 over time as the temperature of the susceptor 44 increases (the temperature is indicated by dashed line 620). DC The relationship between the DC current is shown by line 600. The DC current I drawn from the power supply 310 DC is measured at the input of the DC / AC converter 340. For the purposes of this figure, the voltage V DC may be assumed to be approximately constant. The inductor and susceptor form part of the induction heating arrangement. As the susceptor 44 is inductively heated, the apparent resistance of the induction heating arrangement and the susceptor itself increases, and since conductance is the reciprocal of resistance, the apparent conductance of the induction heating arrangement decreases. The increase in resistance reduces the DC current I drawn from the power supply 310. DC , which at constant voltage decreases as the temperature of the susceptor 44 increases. The high frequency alternating magnetic field provided by the inductor 240 induces eddy currents near the susceptor surface, an effect known as the skin effect. The resistance of the susceptor 44 depends partly on the electrical resistivity of the first susceptor material, partly on the resistivity of the second susceptor material, and partly on the depth of the skin layer of each material available for the induced eddy currents, the resistivity being temperature dependent. As the second susceptor material reaches its Curie temperature, it loses its magnetism. This causes more skin layer to be available for eddy currents in the second susceptor material, which decreases the apparent resistance of the susceptor 44. As a result, as the skin depth of the second susceptor material begins to increase and its resistance begins to drop, the detected DC current I DCA temporary increase in current occurs. This is seen as a valley 602 (local minimum) in FIG. 6. The current continues to increase until it reaches a maximum skin depth which coincides with the point at which the second susceptor material loses its natural magnetic properties. This point is called the Curie temperature and is seen in FIG. 6 as a hill 601 (local maximum). At this point, the second susceptor material has undergone a phase change from a ferromagnetic or ferrimagnetic state to a paramagnetic state. At this point, the susceptor 44 is at a known temperature (the Curie temperature, which is an intrinsic material specific temperature). If the inductor 240 continues to generate an alternating magnetic field after the Curie temperature is reached (i.e., power to the DC / AC converter 340 is not interrupted), the eddy currents generated within the susceptor 44 will flow against the resistance of the susceptor 44, causing continued Joule heating of the susceptor 44, which causes the resistance to increase again (resistance has a polynomial dependence on temperature, and for most metallic susceptor materials can be approximated for our purposes to a third order polynomial dependence), and the current will begin to decrease again as long as the inductor 240 continues to supply power to the susceptor 44.

[0110] Thus, as can be seen from FIG. 6, the apparent resistance of the susceptor 44 (and the corresponding current I drawn from the power supply 310) DC ) may vary with the temperature of the susceptor 44 in a strictly monotonic relationship over a particular temperature range of the susceptor 44. The strictly monotonic relationship allows for an unambiguous determination of the temperature of the susceptor 44 from a determination of the apparent resistance or apparent conductance (1 / R). This is because each determined value of apparent resistance represents only one value of temperature, and there is no ambiguity in the relationship. The monotonic relationship between the temperature of the susceptor 44 and the apparent resistance allows the temperature of the susceptor 44, and therefore the temperature of the aerosol-forming substrate 12, to be determined and controlled. The apparent resistance of the susceptor 44 is determined by at least the DC current I drawn from the DC power supply 310. DC This can be detected remotely by monitoring

[0111] At least the DC current I drawn from the power supply 310 DCis monitored by the controller 330. Preferably, the DC current drawn from the power supply 310, I DC and DC supply voltage V DC Both the conductance and resistance are monitored. The controller 330 adjusts the supply of power provided to the heating arrangement 320 based on the conductance or resistance value. The conductance is proportional to the DC current I DC DC supply voltage V DC is defined as the ratio of the DC supply voltage V DC DC current I DC The heating arrangement 320 is defined as a ratio of the DC current I DC The heating arrangement may be provided with a current sensor (not shown) for measuring a DC supply voltage V DC A voltage sensor (not shown) may optionally be included to measure the DC current I. The current sensor and the voltage sensor are located on the input side of the DC / AC converter 340. DC , and optionally a DC supply voltage V DC is provided by a feedback channel to the controller 330 and represents the AC power P AC Controlling further supply of.

[0112] The controller 330 may control the temperature of the susceptor 44 by maintaining an electrical control parameter, which may be a measured apparent conductance value or a measured apparent resistance value, at a target value corresponding to a target operating temperature of the susceptor 44. The controller 330 may maintain the measured conductance value or the measured resistance value at the target value using any suitable control loop, for example, by using a proportional-integral-derivative control loop.

[0113] To take advantage of the strictly monotonic relationship between the apparent resistance (or apparent conductance) of the susceptor 44 and the temperature of the susceptor 44, during user operation to generate an aerosol, a conductance value or resistance value associated with the susceptor and measured at the input side of the DC / AC converter 340 is maintained between a first calibration value corresponding to a first calibration temperature and a second calibration value corresponding to a second calibration temperature. The second calibration temperature is the Curie temperature of the second susceptor material (hill 601 of the current plot in FIG. 6). The first calibration temperature is a temperature at or above the temperature of the susceptor at which the skin depth of the second susceptor material begins to increase (resulting in a temporary drop in resistance). Thus, the first calibration temperature is a temperature at or above the temperature at maximum permeability of the second susceptor material. The first calibration temperature is preferably at least 50 degrees Celsius lower than the second calibration temperature. At least the second calibration value may be determined by calibration of the susceptor 44, as described in more detail below. The first calibration value and the second calibration value may be stored as calibration values ​​in a memory of the controller 330.

[0114] Since the conductance (resistance) has a polynomial dependence on temperature, the conductance (resistance) behaves nonlinearly as a function of temperature. However, the first and second calibration values ​​are selected such that this dependence can be approximated as linear between the first and second calibration values, because the difference between the first and second calibration values ​​is small, and such that the first and second calibration values ​​are in the upper part of the operating temperature range. Thus, to adjust the temperature to the target operating temperature, the conductance is adjusted according to the first and second calibration values ​​via a linear equation. For example, if the first and second calibration values ​​are conductance values, the target conductance value corresponding to the target operating temperature can be given as follows: G Target =G Lower +(x×ΔG) where ΔG is the difference between the first conductance value and the second conductance value, and x is the ratio of ΔG.

[0115] The controller 330 may control the provision of power to the heating device 320 by adjusting the duty cycle of the switching transistor 410 of the DC / AC converter 340. For example, during heating, the DC / AC converter 340 may continuously generate an alternating current that heats the susceptor 44 and simultaneously generate a DC supply voltage V DC and DC current I DC may be measured, preferably every 1 millisecond, for 100 milliseconds. If conductance is monitored by the controller 330, the duty cycle of the switching transistor 410 is reduced when the conductance reaches or exceeds a value corresponding to the target operating temperature. If resistance is monitored by the controller 330, the duty cycle of the switching transistor 410 is reduced when the resistance reaches or falls below a value corresponding to the target operating temperature. For example, the duty cycle of the switching transistor 410 may be reduced to about 9%. In other words, the switching transistor 410 may be switched into a mode that pulses only every 10 milliseconds for a duration of 1 millisecond. During this 1 millisecond on-state (conducting state) of the switching transistor 410, the DC supply voltage V DC and the DC current I DC The value of is measured to determine the conductance. If the conductance decreases (or the resistance increases), indicating that the temperature of the susceptor 44 is below the target operating temperature, then the gate of transistor 410 is again supplied with a train of pulses at the system's selected drive frequency.

[0116] Power may be supplied to the inductor 240 by the controller 330 in the form of a successive series of pulses of current. In particular, power may be supplied to the inductor 240 in a series of pulses, each separated by a time interval. The successive series of pulses may include two or more heating pulses and one or more probing pulses between the successive heating pulses. The heating pulses have an intensity such that they heat the susceptor 44. The probing pulses are separate power pulses that do not heat the susceptor 44 but rather have an intensity such that they obtain feedback on the evolution (decrease) of the conductance or resistance value and then the susceptor temperature. The controller 330 may control the power by controlling the duration of the time interval between successive heating pulses of power supplied to the inductor 240 by the DC power supply. Additionally or alternatively, the controller 330 may control the power by controlling the length (in other words, the duration) of each of the successive heating pulses of power supplied to the inductor 240 by the DC power supply.

[0117] The controller 330 is programmed to operate in a calibration mode to perform a calibration process to obtain calibration values ​​where the conductance is measured at known temperatures of the susceptor 44. The known temperatures of the susceptor may be a first calibration temperature corresponding to the first calibration value and a second calibration temperature corresponding to the second calibration value. Preferably, the calibration mode is operated every time the user operates the aerosol generating device 200, e.g., every time the user inserts an aerosol-generating article 100 into the aerosol generating device 200.

[0118] During the calibration mode, the controller 330 controls the DC / AC converter 340 to continuously or intermittently supply power to the inductor 240 to heat the susceptor 44. The controller 330 controls the current I drawn by the power supply. DC , and optionally a supply voltage V DCThe conductance or resistance associated with the induction heating arrangement or susceptor 44 is monitored by measuring the current I. As described above in connection with FIG. 6, as the susceptor 44 heats up, the measured current decreases until a first turning point 602 is reached and the current increases. This first turning point or valley 602 corresponds to a local minimum conductance value (local maximum resistance value). The controller 330 may record the local minimum in conductance (or local maximum in resistance) as a first calibration value. The controller may record the value of the conductance or resistance at a predetermined time after the minimum current is reached as the first calibration value. The conductance or resistance is proportional to the measured current I. DC and the measured voltage V DC Alternatively, the supply voltage V DC may be assumed to be approximately constant. The temperature of the susceptor 44 at the first calibration value is referred to as the first calibration temperature. The first calibration temperature is preferably between 150 degrees Celsius and 350 degrees Celsius. More preferably, when the aerosol-forming substrate 12 includes tobacco, the first calibration temperature is 320 degrees Celsius. The first calibration temperature is at least 50 degrees Celsius lower than the second calibration temperature.

[0119] As the controller 330 continues to control the power provided by the DC / AC converter 340 to the inductor 240, the measured current increases until a second turning point 601 is reached and a maximum current (corresponding to the Curie temperature of the second susceptor material) is observed before the measured current begins to decrease. This turning point or hill 601 corresponds to a local maximum conductance value (local minimum resistance value). The controller 330 records the local maximum of conductance (or local minimum of resistance) as a second calibration value. The temperature of the susceptor 44 at the second calibration value is referred to as the second calibration temperature. Preferably, the second calibration temperature is between 200 degrees Celsius and 400 degrees Celsius. When the maximum value is detected, the controller 330 controls the DC / AC converter 340 to interrupt the provision of power to the inductor 240, which results in the susceptor cooling.

[0120] This calibration process of successively heating the susceptor 44 to obtain first and second calibration values ​​may be repeated at least once to improve the reliability of the calibration.

[0121] To further improve the reliability of the calibration process, the controller 310 may optionally be programmed to operate in a pre-heat mode to perform a pre-heat process before operating in the calibration mode. For example, if the aerosol-forming substrate 12 is particularly dry or in similar conditions, the calibration may be performed before heat spreads into the aerosol-forming substrate 12, reducing the reliability of the calibration value. If the aerosol-forming substrate 12 is wet, the susceptor 44 will take longer to reach the valley temperature (due to the moisture content of the substrate 12).

[0122] During operation according to the preheat mode, the controller 330 is configured to continuously supply power to the inductor 240. As described above, the current begins to decrease as the temperature of the susceptor 44 increases until a minimum value is reached. At this stage, the controller 330 is configured to wait a predetermined period of time to allow the susceptor 44 to cool before continuing heating. Accordingly, the controller 330 controls the DC / AC converter 340 to discontinue providing power to the inductor 240. After the predetermined period of time, the controller 330 controls the DC / AC converter 340 to supply power until a minimum value is reached. At this point, the controller controls the DC / AC converter 340 to again discontinue providing power to the inductor 240. The controller 330 again waits the same predetermined period of time to allow the susceptor 44 to cool before continuing heating. This heating and cooling of the susceptor 44 is repeated for the predetermined duration of the preheat process. The predetermined duration of the preheat process is preferably 11 seconds. Following the pre-heating process, the calibration process is preferably for a predetermined combined duration of 20 seconds.

[0123] If the aerosol-forming substrate 12 is dry, the first minimum of the pre-heating process is reached within the predetermined time and the interruption of power is repeated until the end of the predetermined period. If the aerosol-forming substrate 12 is wet, the first minimum of the pre-heating process is reached towards the end of the predetermined period. Thus, carrying out the pre-heating process for a predetermined duration ensures that, regardless of the physical state of the substrate 12, the substrate 12 has enough time to reach a minimum temperature in order to be ready to continue applying power to reach the first maximum. This allows the calibration mode to be operated as early as possible without risking that the substrate 12 has not reached the valley beforehand.

[0124] Furthermore, the aerosol-generating article 100 may be configured such that the minimum value is always reached within a predetermined duration of the pre-heating process. If the minimum value is not reached within a predetermined duration of the pre-heating process, this may indicate that the aerosol-generating article 100, including the aerosol-forming substrate 12, is not suitable for use in the aerosol-generating device 200. For example, the aerosol-generating article 100 may include an aerosol-forming substrate 12 of a different or lower quality than the aerosol-forming substrate 100 intended for use in the aerosol-generating device 200. As another example, the aerosol-generating article 100 may not be configured for use with the heating arrangement 320, for example, if the aerosol-generating article 100 and the aerosol-generating device 200 are manufactured by different manufacturers. Thus, the controller 330 may be configured to generate a control signal to enter a safety mode or to stop operation of the aerosol-generating device 200.

[0125] The pre-heat mode may be implemented in response to receiving a user input, such as, for example, a user activation of the aerosol generating device 200. Additionally or alternatively, the controller 330 may be configured to detect the presence of an aerosol-generating article 100 within the aerosol generating device 200, and the pre-heat process may be implemented in response to detecting the presence of the aerosol-generating article 100 within the cavity 220 of the aerosol generating device 200.

[0126] After performing the preheat and calibration modes, the controller 330 switches control to a heating mode in which the controller controls the DC / AC converter 340 to maintain the conductance or resistance associated with the susceptor 44 at a target value. This may be referred to as a heating process or an operational heating mode. The target value may change over time, either continuously or in steps, but always remains between a maximum and minimum value determined during the calibration process.

[0127] The heating mode may be interrupted and a recalibration mode may be operated such that a recalibration process may be performed at set time intervals during the heating mode, to verify or re-establish maximum and minimum values ​​that may drift over the life of the device.

[0128] To maintain the conductance or resistance associated with the susceptor 44 at a target value during the heating mode, the controller 330 varies the duty cycle of the DC / AC converter 340. If the susceptor is cooled by increased airflow past the susceptor, such as during a user puff on the system, the conductance associated with the susceptor decreases. The controller 330 then increases the duty cycle of the current pulse to increase the power provided to the inductor, thereby moving the conductance of the susceptor back toward the target value.

[0129] To prevent overheating of the device, the heating mode is configured to operate in a different regime when it is determined that the user is puffing. Thus, the heating mode includes the described no puff regime and a puff regime that is implemented when a user puff is detected. Experiments show that during a susceptor cooling event, such as a user puff, the S-shaped curve shown in FIG. 6 undergoes compression, resulting in a local minimum 602 of DC current (or conductance) having a higher value and a local maximum 601 of DC current at the Curie temperature being reduced.

[0130] This flattening of the curve shown in Figure 6 means that the normal control process may lead to overheating. For example, if a cooling event such as a user puff occurs when the target conductance is close to the local maximum conductance established during the calibration process, the target conductance may not actually be achievable. In that situation, there is a risk that the controller will continue to increase the duty cycle of the current pulse to the point where the susceptor is overheated, i.e. heated to a temperature at which undesirable aerosols are provided.

[0131] To reduce the possibility of overheating the susceptor when a user puffs during heating mode operation, the controller operates in a puff regime, which may be referred to as a puff mode or a puff heating mode. Thus, the controller is configured to introduce a duty cycle limit when a cooling event, such as a user puff, is detected during heating mode. For example, during steady state before a user puff, a duty cycle of 30% may be required to maintain a target conductance. Once the susceptor cools down, the controller may need to increase the duty cycle to 50% to maintain the target conductance. However, the controller may introduce a duty cycle limit of less than 50% to prevent overheating. This means that while the susceptor may not reach the target temperature during a puff, it is more important to prevent overheating than to prevent marginal heat deficit.

[0132] To prevent overheating of the apparatus or susceptor during operation, one or more safety modes or processes may be implemented.

[0133] One safety process, illustrated generally with respect to Figures 7, 8, and 9, involves monitoring the response of electrical control parameters to current pulses supplied to the induction heating arrangement, i.e., the response of apparent conductance to the supplied current, to check that a predetermined condition is met. The predetermined condition is that the conductance value increases for the duration of each pulse during the heating mode of operation. If this condition is not met, the controller implements a safety mode, which may be referred to as a recovery mode, in which the susceptor is cooled and a recalibration is performed to determine an updated target value for conductance.

[0134] FIG. 7 illustrates the response of the calculated apparent conductance of an induction heating arrangement to continuous power supply, such as in the calibration mode described above. It is noted that the calibration mode is unlikely to result in heating of the susceptor substantially beyond the maximum value indicated by reference numeral 704, as this may result in overheating of the susceptor. In FIG. 7, for illustrative purposes, line 705 continues beyond the maximum value 704. The article and apparatus are as described above. Supplying current to the inductor increases the temperature of the susceptor. As the temperature of the susceptor increases, its conductance initially decreases at 701. The susceptor includes a portion of a material (such as a nickel alloy) that undergoes a phase transition, in particular a Curie transition from a ferromagnetic phase to a paramagnetic phase, at a particular temperature (e.g., within a temperature range of about 300-400° C.). As described above, the onset of this transition is detectable by a local minimum in conductance 702. As the temperature of the susceptor increases with continued current application, the phase transition progresses at 703 and the conductance continues to increase. At the Curie temperature of the transitioning susceptor material, the phase transition is complete, detectable by a local maximum in conductance 704. The conductance vs. temperature relationship returns to its original state, with conductance decreasing with increasing temperature at 705.

[0135] By operating the calibration mode, the value of the apparent conductance can be matched to the temperature of any particular induction heating arrangement (i.e., formed by a particular inductor / susceptor combination). Since the Curie temperature is therefore known, this temperature can be determined to be equal to the value of the apparent conductance at the local maximum 704. The temperature of the susceptor can then be controlled with reference to an apparent conductance target value 750 set between the local minimum 702 and the local maximum 704 of the calibrated conductance time curve.

[0136] Note that the target value of the apparent conductance is set between a minimum value 702 and a maximum value 701. In this region, the apparent conductance increases with increasing temperature. On either side of the phase transition, i.e., before the minimum value 702 or after the maximum value 704, the apparent conductance decreases with temperature. Also, the target value of the apparent conductance 750 is equal to the target operating temperature while the susceptor is going through its phase transition (i.e., between the minimum value 702 and the maximum value 704), and the s-shape of the curve means that the same values ​​of apparent resistance occur at lower and higher temperatures.

[0137] During the heating mode for generating an aerosol, current is supplied to the induction heating arrangement as current pulses, and these pulses are controlled with reference to the target value of the apparent conductance as described above. To check that the temperature of the susceptor is properly controlled, the response of the apparent conductance to the current pulses is determined. If the susceptor is maintained at the correct temperature, the apparent conductance increases in response to the current pulses. This ensures that the temperature of the susceptor is between maximum and minimum values ​​determined by calibration, and that the desired operating temperature is achieved by controlling with reference to the target value of the apparent conductance. If the apparent conductance does not meet this predetermined criterion of increasing in response to a current pulse, a fault is assumed and the controller implements a recovery mode in which the susceptor is cooled and the calibration mode is implemented.

[0138] The curves shown in Figure 7 are examples of apparent conductance responses to a calibration mode. Such a mode may be performed when an article is inserted into the device prior to generating an aerosol. Several scenarios may occur that may invalidate the calibration and result in the susceptor temperature being improperly maintained.

[0139] For example, an article may be improperly inserted into the apparatus when the calibration is performed. Despite this, the apparatus will normally adjust the temperature to the conductance target value 750 as determined by the calibration. However, during use, the article may be pushed further into the apparatus, thereby moving the susceptor relative to the inductor. This causes the S-curve to shift down from its initial calibrated value 700 to a new position 800, as shown in FIG.

[0140] The problem is that the conductance target 750 will be located above the maximum 804 of the new s-curve 800. As a result, the device will try to control the current supply with reference to the calibrated target 750, but due to the repositioning of the s-curve, the new maximum 804 is the maximum conductance value that can be reached, and this target cannot be reached. The device will continue to heat in order to meet the calibrated conductance target 750, but will eventually reach the new maximum 804. After reaching the new maximum 804, the device will continue to heat until it actually passes the maximum 804. After the maximum 804, the response of the conductance to temperature is inverted, which means that the power pulse trigger will cause the apparent conductance to decrease.

[0141] The effect can be seen in FIG. 9. After an initial calibration, a target conductance 750 is set between the maximum 704 and minimum 702 of the calibration curve. Initially, during the heating mode, current pulses are supplied to the induction heating arrangement and are controlled with reference to the target conductance value 750. Such controlled pulses are seen in the group of pulses 900 of FIG. 9. It can be seen that the slope of these pulses is positive as the conductance increases over the duration of each pulse. As mentioned above, the s-curve is displaced after the article moves in the device. As a result, the first current pulse 905 after this anomalous movement records a low apparent conductance. The conductance increases with subsequent pulses as the controller attempts to increase the conductance to the target level 750. However, the new maximum 804 is lower than the target value 750, which means that the current pulses are not controlled. As the temperature of the susceptor increases, the apparent conductance response to the power supplied changes and the conductance begins to decrease with each pulse 910. Without a safety mechanism, the temperature may continue to increase as the conductance decreases. However, if the first pulse is detected (e.g., pulse 910) that does not show an increase in conductance over its duration, the controller initiates a safety or recovery mode.

[0142] As mentioned above, the system's controller receives various inputs and signals and controls the supply of power to the induction heating arrangement according to a number of operating modes, which is shown diagrammatically in Figure 10 for the aerosol generation system described above.

[0143] As shown in FIG. 10, the controller 1000 is configured to receive input signals from a user interface 1001, a voltage sensor 1010 for determining the voltage across the input side of the DC / AC converter of the induction heating arrangement, a current sensor 1020 for determining the DC current supplied to the induction heating arrangement, a puff sensor 1030 for detecting a user puff, and a PCB temperature sensor 1040 for determining the temperature of the control electronics of the aerosol generating device.

[0144] The controller processes various input signals and determines which of a plurality of operational modes 1050 to apply. The controller then controls the supply of power from a power supply 1060 to an induction heating arrangement 1070 to control the temperature of the susceptor according to one of the plurality of operational modes 1050.

[0145] In certain embodiments, the operating modes are preheat mode 1051 , calibration mode 1052 , heating mode: non-puff regime 1053 , heating mode: puff regime 1054 , recalibration mode 1055 , and safety or recovery mode 1056 .

[0146] As an example of operation, the controller 1000 may receive a signal from the user interface 1001 that a user has begun a use session to consume an aerosol-generating article. The controller sends a signal to operate in pre-heat mode 1051. Signals from the voltage sensor 1010 and the current sensor 1020 are received by the controller 1000 and a value for the apparent conductance of the induction heating arrangement 1070 is calculated. The value of the apparent conductance is monitored.

[0147] When preheat mode 1051 is finished, for example after a predetermined period of time, the controller sends a signal to operate in calibration mode 1052. The calibration mode proceeds, for example, as described above, and a target value for apparent conductance is determined.

[0148] Once the calibration mode 1052 is completed, for example once the target value of apparent conductance has been determined, the controller sends a signal to operate in the heating mode: non-puffing regime 1053. This heating mode is applied when the user is not puffing on the device. The temperature of the susceptor is maintained at the operating temperature by supplying current pulses to the induction heating arrangement and controlling the power supplied with reference to the target value of conductance.

[0149] If during the heating mode: non-puff regime 1053 a signal is received from the puff sensor 1030 indicating that the user is puffing, the controller signals to switch the mode of operation to the heating mode: non-puff regime 1054. This mode is similar to the heating mode: non-puff regime, but there is a limit to the duty cycle of the power supplied to the induction heating arrangement to prevent overheating. When the controller determines that the user is no longer puffing, a signal is issued to return to the heating mode: non-puff regime 1053.

[0150] At regular time intervals, or after a predetermined number of puffs have been recorded, the controller signals to operate in recalibration mode 1055. The recalibration mode verifies or re-determines the target value of conductance. If the recalibration mode is completed successfully, the controller signals to return to the heating mode: no puff regime. If the recalibration mode is not completed successfully, there may be a fault and the controller signals to operate according to a safety mode.

[0151] If the controller receives a signal indicating the user is taking a puff, switching to the recalibration mode is delayed until the user has finished puffing. If the controller receives a signal indicating the user is taking a puff while operating under the recalibration mode, the recalibration mode is terminated and the operating mode is switched to the heating mode: puff regime.

[0152] During use of the aerosol generation system, a number of abnormal or fault conditions may occur. For example, the monitored conductance value may indicate that the susceptor has overheated. In such a case, the controller issues a signal to enter a safety mode 1056. In the safety mode, the power supplied to the induction heating arrangement is reduced or terminated for a period of time to allow the susceptor to cool. The safety mode may include a recalibration or reset before continued operation in one of the other operating modes. If the abnormal or fault cannot be corrected by the recovery process operating during the recovery mode, operation is terminated.

[0153] A further example of a fault condition may be a determination that the conductance is not increasing in response to a current pulse provided during the heating mode, which may indicate that the susceptor is too hot or cold, causing the controller to send a signal to operate according to a safe mode.

[0154] A further example of a fault condition may be that the temperature of the PCB is determined to be greater than a predetermined maximum temperature, which may indicate that the susceptor is overheating and the device is overheating, causing the controller to send a signal to operate according to a safe mode.

[0155] A further example of a fault condition may be that the voltage of the power source is determined to have decreased below a minimum operating voltage. This may indicate that the power source has insufficient remaining charge to complete a usage session, and the controller sends a signal to operate according to a safe mode. In this case, it may be unlikely that operation can be resumed without recharging the power source.

[0156] For the purposes of this specification and the appended claims, unless otherwise indicated, all numbers expressing amounts, quantities, percentages, and the like should be understood in all instances to be modified 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 recited herein. Within this context, the number A may be considered to include a numerical value that is within the general standard error for the measurement of the property that the number A modifies. The number A may deviate by the percentages recited above, in some cases as used in the appended claims, provided that the amount by which A deviates does not materially affect the basic and novel property(ies) 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 recited herein.

Claims

1. An induction heating arrangement having an inductor and a susceptor, A power supply for supplying power to the induction heating arrangement, A controller configured to control the power supplied from the power supply to the induction heating arrangement and monitor electrical control parameters, comprising: The controller is configured to operate the aerosol generation system in a plurality of operating modes, The plurality of operating modes includes at least a calibration mode for determining the relationship between the electrical control parameters and the temperature of the susceptor and determining a target value of the electrical control parameters, A heating mode in which power is supplied to the inductor to maintain the susceptor at an operating temperature, the operating temperature being maintained by controlling the power supplied to the inductor with reference to the target value of the electrical control parameters, A re-calibration mode for verifying or correcting the relationship between the electrical control parameters and the temperature of the susceptor and re-determining the target value of the electrical control parameters periodically or intermittently, the re-calibration mode being performed periodically based on one or more of a predetermined duration, a predetermined number of user puffs, a predetermined number of temperature steps, and the measured voltage of the power supply, and A safety mode for adjusting the power provided to the induction heating arrangement in response to one or more predetermined criteria being met. An induction heating aerosol generation system.

2. The aerosol generation system according to claim 1, wherein the electrical control parameter is a parameter selected from the list consisting of the electrical resistance of the susceptor, the apparent electrical resistance of the induction heating arrangement, the electrical conductance of the susceptor, the apparent electrical conductance of the induction heating arrangement, the current supplied to the induction heating arrangement, and the power supplied to the induction heating arrangement.

3. The aerosol generation system according to any one of claims 1 or 2, wherein the heating mode is configured to maintain the temperature of the susceptor according to a predetermined temperature profile.

4. During the heating mode, the power supplied to the inductor is supplied as power pulses, for example, current pulses, and the temperature of the susceptor is controlled by changing the load cycle of the inductor. Preferably, the controller is configured to control the temperature of the susceptor during the heating mode with reference to a target value of the apparent conductance of the induction heating arrangement, and the target value of the apparent conductance is determined during the calibration mode or the recalibration mode. The aerosol generation system according to any one of claims 1 or 2.

5. The safety mode involves a reduction in the power supplied to the induction heating arrangement, for example, a reduction in the load cycle supplied to the inductor for a period sufficient to cool the susceptor. The aerosol generation system according to any one of claims 1 or 2.

6. The system comprises a smoking sensor for determining user smoking. For example, the smoking sensor can be an airflow sensor or a temperature sensor such as a thermistor mounted in the airflow path of the aerosol generating device. The aerosol generation system according to any one of claims 1 or 2.

7. The heating mode includes a non-smoking heating regime and a smoking heating regime, and the controller operates according to the smoking heating regime when it is detected that the user is smoking during the heating mode, and operates according to the non-smoking heating regime when it is not detected that the user is smoking during the heating mode. The aerosol generation system according to any one of claims 1 or 2.

8. The controller prevents or delays the switching from the operation according to the heating mode to the operation according to the recalibration mode when it is determined that the user is smoking. The aerosol generation system according to any one of claims 1 or 2.

9. To monitor the temperature, for example, the temperature of the aerosol generating device, a temperature sensor located outside the air flow path is provided, such as a thermocouple or thermistor mounted on the PCB of the aerosol generating device, or a thermocouple or thermistor mounted in the substrate receiving cavity of the aerosol generating device. Preferably, the device switches to the safety mode when it is determined that the temperature of a part of the device is outside a predetermined range, or the operation ends when it is determined that the temperature of a part of the device is outside a predetermined range. The aerosol generating system according to any one of claims 1 or 2.

10. The one or more predetermined criteria of the safety mode, such as safety criteria or safety triggers, are operating events, criteria related to monitored operating parameters, or differential values of monitored parameters. The controller is configured to perform the safety mode in response to the one or more predetermined criteria being met. The aerosol generating system according to any one of claims 1 or 2.

11. At least one of the one or more predetermined criteria is selected from the list of criteria consisting of the temperature of the electronic components of the aerosol generating system exceeding a predetermined temperature, the temperature of the substrate receiving cavity or chamber of the aerosol generating system exceeding a predetermined temperature, the temperature of the susceptor exceeding the maximum operating temperature, the temperature of the susceptor exceeding the Curie temperature of the material components of the susceptor, the response of the electrical control parameters to the power supplied to the induction heating arrangement during the heating mode not meeting a predetermined condition, and the voltage of the power supply dropping below a predetermined level. The aerosol generating system according to claim 10.

12. The safety mode may include one or more of the steps of reducing the power supplied to the induction heating arrangement, terminating the power supplied to the induction heating arrangement, starting another one of the plurality of operating modes, such as a calibration mode or a recalibration mode, and terminating the operation of the system. The aerosol generating system according to any one of claims 1 or 2.

13. Operating in the safety mode includes adjusting the power provided to the induction heating arrangement, e.g., adjusting the power provided to the induction heating arrangement in response to one or more overheating or cooling events, for the aerosol generation system according to any one of claims 1 or 2.

14. At least a portion of the susceptor is configured to undergo a reversible phase transition when heated or cooled through a predetermined temperature range, preferably, the controller is configured to identify upper and lower boundary values of the electrical control parameters associated with upper and lower boundaries of the phase transition, preferably, the target value of the electrical control parameter is set to a value between the upper boundary value and the lower boundary value, for the aerosol generation system according to any one of claims 1 or 2.

15. The aerosol generation system according to any one of claims 1 or 2, wherein the recalibration mode is configured to operate without interrupting the heating mode more than necessary.

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