Aerosol generating device and system with induction heating device and method of operation thereof

Abstract

A method is provided for controlling aerosol generation in an aerosol-generating device (200). The device (200) comprises an inductive heating arrangement (320) and a power supply (310) for providing power to the inductive heating arrangement (320). The method includes controlling power provided to the inductive heating arrangement (320) to incrementally increase a temperature of a susceptor (160) associated with the aerosol-generating device (200) from a first operating temperature to a second operating temperature, the susceptor (160) being configured to heat the aerosol-forming substrate (110), and the power being controlled based on a measured resistance, conductance, or current associated with the susceptor.

Description

[Technical field]

[0001] The present disclosure relates to an inductive heating device for heating an aerosol-forming substrate. The present disclosure further relates to an aerosol-generating device including such an inductive heating device, and to a method for controlling aerosol generation in an aerosol-generating device. [Background technology]

[0002] The aerosol generating device may include an electrically operated heat source configured to heat the aerosol-forming substrate to generate the aerosol. The electrically operated heat source may be an induction heating device. The induction heating device typically comprises an inductor inductively coupled to the 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 aerosol-forming substrate may be controlled by controlling the temperature of the susceptor. It is therefore important that such an aerosol generating device accurately monitors and controls the temperature of the susceptor to ensure optimal generation and delivery of the aerosol to the user.

[0003] It is desirable to provide temperature monitoring and control of induction heating devices that is accurate, reliable, and inexpensive. Summary of the Invention

[0004] According to an embodiment of the invention, there is provided a method for controlling aerosol generation in an aerosol-generating device. The device may comprise an inductive heating arrangement and a power source for providing power to the inductive heating arrangement. The method may include controlling the power provided to the inductive heating arrangement to incrementally increase a temperature of a susceptor associated with the aerosol-generating device from a first operating temperature to a second operating temperature, the susceptor being configured to heat an aerosol-forming substrate.

[0005] Controlling the power provided to the induction heating arrangement to increase the temperature of the susceptor in stages allows for aerosol generation over a sustained period, including a number of puffs, such as 14 puffs, or a complete user experience over a predefined time period, such as 6 minutes, with delivery (nicotine, flavor, aerosol volume, etc.) substantially constant from puff to puff throughout the entire user experience. Specifically, the staged increase in temperature of the susceptor prevents reduced aerosol delivery due to substrate depletion near the susceptor and reduced thermal diffusion over time. Additionally, the staged increase in temperature allows for heat to diffuse into the substrate at each step.

[0006] The stepwise increase in temperature of the susceptor includes at least three successive temperature steps, each temperature step having a duration. The temperature of the susceptor may be maintained at a predetermined temperature for the duration of each temperature step. The duration may be at least 10 seconds. The duration may be between 30 seconds and 200 seconds. The duration may be between 40 seconds and 160 seconds. The first temperature step may have a longer duration than the subsequent temperature steps. The duration may be predetermined. The duration may correspond to a predetermined number of user puffs.

[0007] The stepwise increase in temperature of the susceptor may include more than two temperature steps and fewer than 14 temperature steps. The stepwise increase in temperature of the susceptor may include more than two temperature steps and fewer than eight temperature steps.

[0008] The first operating temperature may be sufficient for the aerosol-forming substrate to form an aerosol.

[0009] The method may further include determining a conductance or resistance value associated with the susceptor, and the power provided to the induction heating arrangement is controlled based on the determined conductance value or the determined resistance value.

[0010] 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.

[0011] Controlling the power provided to the induction heating arrangement may include interrupting the provision of power to the DC / AC converter when the determined conductance value exceeds a preset threshold conductance value and resuming the provision of power to the DC / AC converter when the determined conductance value falls below the preset threshold conductance value. Controlling the power provided to the induction heating arrangement may include interrupting the provision of power to the DC / AC converter when the determined resistance value falls below the preset threshold resistance value and resuming the provision of power to the DC / AC converter when the determined resistance value exceeds the preset threshold conductance value.

[0012] Power from the power source may be provided to the inductor intermittently via a DC / AC converter. Power from the power source may be provided to the inductor via the DC / AC converter as a plurality of 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.

[0013] The method may further include performing a calibration process to measure one or more calibration values ​​associated with the susceptor. Controlling the power provided to the induction heating arrangement may include controlling the power such that a temperature of the susceptor is adjusted based on the one or more calibration values.

[0014] The one or more calibration values ​​can include a first conductance value associated with a first calibrated temperature of the susceptor and a second conductance value associated with a second calibrated temperature of the susceptor. Controlling the power provided to the induction heating arrangement can include maintaining the conductance value associated with the susceptor between the first conductance value and the second conductance value.

[0015] The one or more calibration values ​​can include a first resistance value associated with a first calibration temperature of the susceptor and a second resistance value associated with a second calibration temperature of the susceptor. Controlling the power provided to the induction heating arrangement can include maintaining a resistance value associated with the susceptor between the first resistance value and the second resistance value.

[0016] 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 second calibration temperature may correspond to the second Curie temperature of the second susceptor material. 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 along one of their major surfaces. The susceptor may further include 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.

[0017] Controlling the power provided to the induction heating arrangement may include controlling the power such that the temperature of the susceptor is between a first calibration temperature and a second calibration temperature.

[0018] The first operating temperature may be greater than or equal to a first calibration temperature, and the second operating temperature may be less than or equal to a second calibration temperature.

[0019] The first calibration temperature may be between 150 degrees Celsius and 350 degrees Celsius and the second calibration temperature may be between 200 degrees Celsius and 400 degrees Celsius. The temperature difference between the first calibration temperature and the second calibration temperature may be at least 50 degrees Celsius.

[0020] The calibration process may be performed during user operation of the aerosol generating device to generate the aerosol.

[0021] The calibration values ​​used to control the heating process are therefore more accurate and reliable than if the calibration process were carried out at the time of manufacture. This is particularly important when the susceptor forms part of a separate aerosol-generating article that does not form part of the aerosol-generating device. In these circumstances, calibration at the time of manufacture is not possible.

[0022] The calibration process may be performed periodically based on one or more of a predetermined duration, a predetermined number of user puffs, a predetermined number of temperature steps, and a measured voltage of the power supply.

[0023] Conditions may change during user operation of the aerosol generating device, for example, the susceptor may move relative to the induction heating arrangement, the power source (e.g., a battery) may lose some efficiency over time, etc. Therefore, periodically performing a calibration process ensures reliability of the calibration values, thereby ensuring that optimal temperature regulation is maintained throughout use of the aerosol generating device.

[0024] Performing the calibration process may include (i) controlling power provided to the induction heating arrangement to increase the temperature of the susceptor, (ii) monitoring at least a current value of the induction heating arrangement, (iii) interrupting the provision of power to the induction heating arrangement when at least the current value reaches a maximum value, the current value at the maximum value corresponding to a second calibration temperature of the susceptor, and (iv) controlling power provided to the induction heating arrangement to increase the temperature of the susceptor when a current value associated with the susceptor reaches a minimum value, the current value at the minimum value corresponding to a first calibration temperature of the susceptor. Monitoring at least the current value of the induction heating arrangement may further include monitoring a voltage value of the induction heating arrangement.

[0025] The method may further include repeating steps (i)-(iv) when the conductance value associated with the susceptor reaches a minimum value. After repeating steps (i)-(iv), the conductance value corresponding to the current value at the maximum value may be stored as a second calibration value and the conductance value corresponding to the current value at the minimum value may be stored as the first calibration value. Alternatively, the resistance value corresponding to the current value at the maximum value may be stored as the second calibration value and the resistance value corresponding to the current value at the minimum value may be stored as the first calibration value.

[0026] Performing the calibration process may include (i) controlling the power provided to the induction heating arrangement to increase the temperature of the susceptor; (ii) monitoring a conductance or resistance value associated with the susceptor; (iii) interrupting the provision of power to the induction heating arrangement when the conductance value reaches a maximum value or the resistance value reaches a minimum value, where the maximum current value or minimum resistance value corresponds to a second calibration temperature of the susceptor; and (iv) controlling the power provided to the induction heating arrangement to increase the temperature of the susceptor when the conductance value reaches a minimum value or the resistance value reaches a maximum value, where the minimum conductance value or maximum resistance value corresponds to a first calibration temperature of the susceptor.

[0027] Steps (i)-(iv) may be repeated when the conductance value reaches a minimum or the resistance value reaches a maximum.

[0028] After repeating steps (i) to (iv), the maximum conductance value or the minimum resistance value may be stored as the second conductance value, and the minimum conductance value or the maximum resistance value may be stored as the first conductance value.

[0029] The calibration process is fast and reliable without slowing down the aerosol generation. Moreover, by repeating the steps of the calibration process, the subsequent temperature adjustment is significantly improved based on the calibration value obtained from the repeated calibration process, since it takes more time for the heat to diffuse into the substrate. Performing the calibration process based at least on the measured current value assumes that the voltage of the power supply remains constant. Therefore, monitoring the conductance or resistance value during the calibration process (and thus using both the measured current and voltage values) further improves the reliability of the calibration when the voltage of the power supply changes over a long period of time (e.g., after multiple recharges).

[0030] The method may further include performing a pre-heating process to heat the susceptor to a first calibration temperature. The pre-heating process may have a predetermined duration. The pre-heating process allows heat to diffuse into the substrate prior to initiation of the calibration process, thereby further improving the reliability of the calibration value.

[0031] Performing the pre-heating process may include controlling power provided to the induction heating arrangement to increase the temperature of the susceptor, monitoring at least a current value in the induction heating arrangement, and interrupting the provision of power to the induction heating arrangement when the current value reaches a minimum value, the current value at the minimum value corresponding to a first calibration temperature of the susceptor.

[0032] If the current value reaches a minimum value for the predetermined duration of the pre-heating process, the method may include interrupting the provision of power to the induction heating arrangement to reduce the temperature of the susceptor, and thereafter resuming the provision of power to the induction heating arrangement to increase the temperature of the susceptor to the first calibration temperature. The interrupting of the provision of power to the induction heating arrangement and resuming the provision of power to the induction heating arrangement are repeated for the predetermined duration of the pre-heating process. The method may further include ceasing operation of the aerosol generating device if the current value of the susceptor does not reach a minimum value for the predetermined duration of the pre-heating process.

[0033] Performing the pre-heating process may include controlling power provided to the induction heating arrangement to increase the temperature of the susceptor, monitoring a conductance or resistance value associated with the susceptor, and interrupting the provision of power to the induction heating arrangement when the conductance value reaches a minimum value or the resistance value reaches a maximum value, where the conductance value at the minimum value or the resistance value at the maximum value corresponds to a first calibration temperature of the susceptor.

[0034] If the conductance value reaches a minimum or the resistance value reaches a maximum during the predetermined duration of the pre-heating process, the method may further include interrupting the provision of power to the induction heating arrangement to reduce the temperature of the susceptor, and thereafter resuming the provision of power to the induction heating arrangement to increase the temperature of the susceptor to the first calibration temperature. Interrupting the provision of power to the induction heating arrangement and resuming the provision of power to the induction heating arrangement may be repeated for the predetermined duration of the pre-heating process. If the conductance value does not reach a minimum or the resistance value does not reach a maximum during the predetermined duration of the pre-heating process, the method may further include ceasing operation of the aerosol generating device.

[0035] By performing the pre-heating process step for a predetermined duration, heat can be diffused into the substrate in a timely manner to reach the minimum conductance value measured during the calibration process, regardless of the physical state of the substrate (e.g., whether the substrate is dry or wet), thereby ensuring the reliability of the calibration process.

[0036] Moreover, the susceptor is preferably included in an aerosol generating article configured to be inserted into an aerosol generating device. An aerosol generating article that is not configured for use with an aerosol generating device will not exhibit the same behavior as an approved aerosol generating article. Specifically, for an aerosol generating article that is not configured for use with an aerosol generating device, a minimum current / conductance value or a maximum resistance value is not observed for a given duration during the preheating process. This therefore prevents the use of an unapproved aerosol generating article.

[0037] The method may further comprise measuring the DC current drawn from the power supply 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 supply and from the DC current drawn from the power supply. The method may further comprise measuring the DC supply voltage of the power supply 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 if the susceptor forms part of the article) and the apparent conductance thus determined (since 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, in this text, when the inventors refer to the conductance of the susceptor, they are in fact referring to the apparent conductance when the susceptor forms part of a separate aerosol-generating article.

[0038] The first operating temperature may be between 150 degrees Celsius and 330 degrees Celsius, and the second operating temperature is between 200 degrees Celsius and 400 degrees Celsius. The temperature difference between the first operating temperature and the second operating temperature may be at least 30 degrees Celsius.

[0039] The gradual increase in the temperature of the susceptor may include a first temperature step having a temperature corresponding to the first operating temperature, where the first operating temperature is 330 degrees Celsius, a second temperature step having a temperature of 340 degrees Celsius, a third temperature step having a temperature of 345 degrees Celsius, a fourth temperature step having a temperature of 355 degrees Celsius, and a fifth temperature step having a temperature corresponding to the second operating temperature, where the second operating temperature is 380 degrees Celsius.

[0040] The susceptor and the aerosol-forming substrate may form part of an aerosol-generating article, and the aerosol-generating device may be configured to removably receive the aerosol-generating article.

[0041] According to another embodiment of the invention, there is provided an aerosol generating device comprising a power supply for providing a DC supply voltage and a DC current, and power supply electronics connected to the power supply, the power supply electronics including a DC / AC converter, an inductor connected to the DC / AC converter for generating an alternating magnetic field when energized with an alternating current from the DC / AC converter, the inductor being coupleable to a susceptor, the susceptor being configured to heat the aerosol-forming substrate, and a controller configured to control power provided to the power supply electronics to incrementally increase the temperature of the susceptor from a first operating temperature to a second operating temperature.

[0042] The stepwise increase in temperature of the susceptor includes at least three successive temperature steps, each temperature step having a duration. During the duration of each temperature step, the controller may be configured to control power provided to the power electronics to maintain the temperature of the susceptor at the predetermined temperature. The duration may be at least 10 seconds. The duration may be between 30 seconds and 200 seconds. The duration may be between 40 seconds and 160 seconds. The first temperature step may have a longer duration than the subsequent temperature steps. The duration of each temperature step may be predetermined. The duration may correspond to a predetermined number of user puffs. The stepwise increase in temperature of the susceptor may include more than two temperature steps and less than fourteen temperature steps. The stepwise increase in temperature of the susceptor may include more than two temperature steps and less than eight temperature steps. The first operating temperature may be sufficient for the aerosol-forming substrate to form an aerosol.

[0043] The controller may be configured to determine a conductance or resistance value associated with the susceptor. The controller may be configured to control power provided to the power supply electronics based on the determined conductance value or the determined resistance value.

[0044] Controlling the power provided to the power supply electronics may include interrupting the provision of power to the DC / AC converter when the determined conductance value exceeds a preset threshold conductance value, and resuming the provision of power to the DC / AC converter when the determined conductance value falls below the preset threshold conductance value.

[0045] Controlling the power provided to the induction heating arrangement may include interrupting the provision of power to the DC / AC converter when the determined resistance value falls below a preset threshold resistance value, and resuming the provision of power to the DC / AC converter when the determined resistance value exceeds a preset threshold conductance value.

[0046] The power supply electronics may be configured to intermittently provide power from a power supply to the inductor via a DC / AC converter.

[0047] The power supply electronics may be configured to provide power from a power supply, via a DC / AC converter, to the inductor as multiple pulses, each pulse separated by a time interval.

[0048] Controlling the power provided to the power electronics may include controlling a time interval between each of the multiple pulses. Controlling the power provided to the power electronics may include controlling a length of each pulse of the multiple pulses.

[0049] The controller may be further configured to perform a calibration process to measure one or more calibration values ​​associated with the susceptor.

[0050] Controlling the power provided to the power electronics can include controlling the power such that the temperature of the susceptor is adjusted based on one or more calibration values.

[0051] The one or more calibration values ​​can include a first conductance value associated with a first calibrated temperature of the susceptor and a second conductance value associated with a second calibrated temperature of the susceptor. Controlling the power provided to the power electronics can include maintaining the conductance value associated with the susceptor between the first conductance value and the second conductance value.

[0052] The one or more calibration values ​​may include a first resistance value associated with a first calibration temperature of the susceptor and a second resistance value associated with a second calibration temperature of the susceptor.

[0053] Controlling the power provided to the induction heating arrangement can include maintaining a resistance value associated with the susceptor between a first resistance value and a second resistance value.

[0054] The second calibration temperature of the susceptor may correspond to the Curie temperature of the material of the susceptor.

[0055] Controlling the power provided to the power electronics can include controlling the power such that the temperature of the susceptor is between a first calibration temperature and a second calibration temperature.

[0056] The first operating temperature may be greater than or equal to a first calibration temperature, and the second operating temperature may be less than or equal to a second calibration temperature.

[0057] The first calibration temperature may be between 150 degrees Celsius and 350 degrees Celsius, and the second calibration temperature is between 200 degrees Celsius and 400 degrees Celsius. The temperature difference between the first calibration temperature and the second calibration temperature may be at least 50 degrees Celsius.

[0058] The calibration process may be performed during user operation of the aerosol generating device to generate aerosol, or may be performed periodically based on one or more of a predetermined duration, a predetermined number of user puffs, a predetermined number of temperature steps, and a measured voltage of the power supply.

[0059] Performing the calibration process may include (i) controlling power provided to the power supply electronics to increase the temperature of the susceptor, (ii) monitoring at least a current value of the power supply electronics, (iii) interrupting the provision of power to the power supply electronics when the current value reaches a maximum value, the current value at the maximum value corresponding to a second calibration temperature of the susceptor, and (iv) controlling power provided to the power supply electronics to increase the temperature of the susceptor when the current value reaches a minimum value, the current value at the minimum value corresponding to the first calibration temperature. Monitoring at least a current value of the power supply electronics may include monitoring a voltage value of the power supply electronics.

[0060] Performing the calibration process may further include repeating steps (i)-(iv) when the current value of the power supply electronics reaches a minimum value. The controller may be further configured to store the conductance value corresponding to the current value at the maximum value as a second calibration value and the conductance value corresponding to the current value at the minimum value as the first calibration value after repeating steps i)-iv), or to store the resistance value corresponding to the current value at the maximum value as the second calibration value and the resistance value corresponding to the current value at the minimum value as the first calibration value.

[0061] Performing the calibration process may include (i) controlling the power provided to the induction heating arrangement to increase the temperature of the susceptor; (ii) monitoring a conductance or resistance value associated with the susceptor; (iii) interrupting the provision of power to the induction heating arrangement when the conductance value reaches a maximum value or the resistance value reaches a minimum value, the maximum conductance value or the minimum resistance value corresponding to a second calibration temperature of the susceptor; and (iv) controlling the power provided to the induction heating arrangement to increase the temperature of the susceptor when the conductance value reaches a minimum value or the resistance value reaches a maximum value, the minimum conductance value or the maximum resistance value corresponding to a first calibration temperature of the susceptor.

[0062] Performing the calibration process may further include repeating steps i)-iv) when the conductance value reaches a minimum or the resistance value reaches a maximum. After repeating steps (i)-(iv), the controller may be further configured to store the conductance value at the maximum as a second calibration value and store the conductance value at the minimum as a first calibration value. After repeating steps (i)-(iv), the controller may be further configured to store the resistance value at the minimum as the second calibration value and store the resistance value at the maximum as the first calibration value.

[0063] The controller may be further configured to perform a pre-heating process to heat the susceptor to a first calibration temperature. The pre-heating process may have a predetermined duration. Performing the pre-heating process may include controlling power provided to the power supply electronics to increase a temperature of the susceptor, monitoring at least a current value of the power supply electronics, and interrupting the provision of power to the power supply electronics when the current value reaches a minimum value, the current value at the minimum value corresponding to the first calibration temperature of the susceptor.

[0064] Performing the pre-heat process may further include interrupting the provision of power to the power supply electronics to reduce the temperature of the susceptor when the current value reaches a minimum value during a predetermined duration of the pre-heat process, and thereafter resuming the provision of power to the power supply electronics to increase the temperature of the susceptor to the first calibration temperature. The interrupting of the provision of power to the power supply electronics and the resuming of the provision of power to the power supply electronics may be repeated for the predetermined duration of the pre-heat process.

[0065] The controller may be further configured to generate a control signal to stop operation of the aerosol generating device if the current value of the susceptor does not reach the minimum value for a predetermined duration of the pre-heating process.

[0066] Performing the pre-heating process may include controlling power provided to the induction heating arrangement to increase the temperature of the susceptor, monitoring a conductance or resistance value associated with the susceptor, and interrupting the provision of power to the induction heating arrangement when the conductance value reaches a minimum value or the resistance value reaches a maximum value, where the current value at the minimum value or the resistance value at the maximum value corresponds to a first calibration temperature of the susceptor.

[0067] If the conductance value reaches a minimum or the resistance value reaches a maximum during the predetermined duration of the pre-heating process, the provision of power to the induction heating arrangement may be interrupted to allow the temperature of the susceptor to decrease, and thereafter the provision of power to the induction heating arrangement may be resumed to increase the temperature of the susceptor to the first calibration temperature. The interruption of the provision of power to the induction heating arrangement and the resumption of the provision of power to the induction heating arrangement may be repeated for the predetermined duration of the pre-heating process.

[0068] If the conductance value does not reach the minimum value or the resistance value does not reach the maximum value during a predetermined duration of the pre-heating process, operation of the aerosol generating device may be stopped.

[0069] The aerosol generating device may further comprise a current sensor at the input side of the DC / AC converter configured to measure a DC current drawn from the power supply. Conductance and resistance values ​​associated with the susceptor may be determined from a DC supply voltage of the power supply and from the DC current drawn from the power supply. The aerosol generating device may further comprise a voltage sensor at the input side of the DC / AC converter configured to measure a DC supply voltage of the power supply.

[0070] The first operating temperature may be between 150 degrees Celsius and 330 degrees Celsius, and the second operating temperature is between 200 degrees Celsius and 400 degrees Celsius. The temperature difference between the first operating temperature and the second operating temperature may be at least 30 degrees Celsius.

[0071] The gradual increase in the temperature of the susceptor may include a first temperature step having a temperature corresponding to the first operating temperature, where the first operating temperature is 330 degrees Celsius, a second temperature step having a temperature of 340 degrees Celsius, a third temperature step having a temperature of 345 degrees Celsius, a fourth temperature step having a temperature of 355 degrees Celsius, and a fifth temperature step having a temperature corresponding to the second operating temperature, where the second operating temperature is 380 degrees Celsius.

[0072] The power electronics may further comprise a matching network for matching the impedance of the inductor to the impedance of the susceptor.

[0073] The aerosol generating device may further comprise a housing having a cavity configured to removably receive the aerosol-generating article. The aerosol-generating article may comprise an aerosol-forming substrate and a susceptor.

[0074] According to another embodiment of the present invention there is provided an aerosol generating system comprising an aerosol generating device and an aerosol generating article as described above. The aerosol generating article may comprise an aerosol-forming substrate and a susceptor.

[0075] The susceptor may include a first susceptor material and a second susceptor material, the first susceptor material being disposed in physical contact with the second susceptor material. The first susceptor material may be one of aluminum, iron, and stainless steel, and the second susceptor material is nickel or a nickel alloy. The first susceptor material may have a first Curie temperature and the second susceptor material may have a second Curie temperature. The second Curie temperature may be lower than the first Curie temperature. The second calibration temperature may correspond to a second Curie temperature of the second susceptor material.

[0076] 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. In some examples, the aerosol-generating device may heat the aerosol-forming substrate to facilitate the release of volatile compounds from the substrate. An electrically operated aerosol-generating device may include an atomizer, such as an electric heater, for heating the aerosol-forming substrate to form an aerosol.

[0077] 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.

[0078] 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.

[0079] 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.

[0080] The aerosol-forming substrate may comprise nicotine. The aerosol-forming substrate may comprise tobacco, for example a tobacco-containing material containing volatile tobacco flavour 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 flavour 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.

[0081] As used herein, "aerosol cooling element" refers to a component of an aerosol-generating article located downstream of an aerosol-forming substrate such that, during use, an aerosol formed by volatile compounds emitted from the aerosol-forming substrate passes through and is cooled by the aerosol cooling element before being inhaled by a user. Aerosol cooling elements have a large surface area but generate a low pressure drop. Filters and other mouthpieces that generate a high pressure drop (e.g., filters formed of fiber bundles) are not considered aerosol cooling elements. Chambers and cavities within an aerosol-generating article are not considered aerosol cooling elements.

[0082] 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.

[0083] 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.

[0084] As used herein in referring to an aerosol generating device, the terms "upstream" and "forward," as well as "downstream" and "rearward," are used to describe the relative locations of components, or portions of components, of the aerosol generating device in relation to the direction in which air flows through the aerosol generating device during use. An aerosol generating device according to the invention comprises a proximal end through which aerosol exits the device during use. The proximal end of the aerosol generating device may also be referred to as the mouth end or downstream end. The mouth end is downstream of the distal end. The distal end of the aerosol-generating article may also be referred to as the upstream end. Components or portions of components of an aerosol generating device may be described as being upstream or downstream of one another based on their relative location with respect to the airflow path of the aerosol generating device.

[0085] As used herein in referring to an aerosol-generating article, the terms "upstream" and "forward", as well as "downstream" and "backward" are used to describe the relative positions of components or parts of components of the aerosol-generating article in relation to the direction in which air flows through the aerosol-generating article during use of the aerosol-generating article. The aerosol-generating article according to the present invention comprises a proximal end through which the aerosol exits the article during use. The proximal end of the aerosol-generating article may also be referred to as the mouth end or the downstream end. The mouth end is downstream of the distal end. The distal end of the aerosol-generating article may also be referred to as the upstream end. Components or parts of components of the aerosol-generating article may be described as being upstream or downstream of each other based on their relative positions between the proximal end of the aerosol-generating article and the distal end of the aerosol-generating article. The forward of a component or part of a component of the aerosol-generating article is the part that is at the end closest to the upstream end of the aerosol-generating article. The back of a component or part of a component of the aerosol-generating article is the part that is at the end closest to the downstream end of the aerosol-generating article.

[0086] 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.

[0087] 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.

[0088] 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 features of any other example, embodiment, or aspect described herein.

[0089] Example 1: A method for controlling aerosol generation in an aerosol generating device, the device comprising an induction heating arrangement and a power source for providing power to the induction heating arrangement, the method including controlling the power provided to the induction heating arrangement to gradually increase a temperature of a susceptor associated with the aerosol generating device from a first operating temperature to a second operating temperature, the susceptor being configured to heat an aerosol-forming substrate. Example 2: The method according to example 1, wherein the stepwise increase in temperature of the susceptor includes at least three successive temperature steps, each temperature step having a duration. Example 3: The method according to example 2, wherein the temperature of the susceptor is maintained at a predetermined temperature for the duration of each temperature step. Example 4: The method according to example 2 or 3, wherein the duration is at least 10 seconds. Example 5: The method according to example 2 or 3, wherein the duration is between 30 seconds and 200 seconds. Example 6: The method according to any of Examples 2 or 3, wherein the duration is between 40 seconds and 160 seconds. Example 7: The method according to any of embodiments 2-6, wherein the duration of each temperature step is predetermined. Example 8: The method according to example 2 or 3, wherein the duration corresponds to a predetermined number of user puffs. Example 9: The method according to any of examples 2-8, wherein the first temperature step has a longer duration than the subsequent temperature steps. Example 10: The method according to any of the preceding claims, wherein the stepwise increase in temperature of the susceptor includes more than two temperature steps and less than fourteen temperature steps. Example 11: The method according to any of the preceding embodiments, wherein the stepwise increase in temperature of the susceptor includes more than two temperature steps and less than eight temperature steps. Example 12: The method according to any of Examples 1-11, wherein the first operating temperature is sufficient for the aerosol-forming substrate to form an aerosol. Example 13: The method according to any of Examples 1-12, further comprising determining a conductance or resistance value associated with the susceptor, wherein the power provided to the induction heating arrangement is controlled based on the determined conductance value or the determined resistance value. Example 14: The method according to example embodiment 13, wherein the induction heating arrangement includes a DC / AC converter and an inductor connected to the DC / AC converter, and the susceptor is arranged to be inductively coupled to the inductor. Example 15: A method according to example 14, wherein controlling the power provided to the induction heating arrangement includes interrupting the provision of power to the DC / AC converter when the determined conductance value exceeds a preset threshold conductance value and resuming the provision of power to the DC / AC converter when the determined conductance value falls below the preset threshold conductance value, or controlling the power provided to the induction heating arrangement includes interrupting the provision of power to the DC / AC converter when the determined resistance value falls below the preset resistance value and resuming the provision of power to the DC / AC converter when the determined resistance value exceeds the preset threshold conductance value. Example 16: 16. The method according to example 14 or 15, wherein power from the power source is intermittently supplied to the inductor via a DC / AC converter. Example 17: The method according to any of embodiments 14-16, wherein power from a power source is provided to the inductor via a DC / AC converter as a plurality of pulses, each pulse being separated by a time interval. Example 18: 18. The method according to example 17, wherein controlling the power provided to the induction heating arrangement includes controlling a time interval between each of the plurality of pulses. Example 19: The method according to example 17, wherein controlling the power provided to the induction heating arrangement includes controlling a length of each pulse of the plurality of pulses. Example 20: The method according to any of Examples 1-19, further comprising performing a calibration process to measure one or more calibration values ​​associated with the susceptor. Example 21: 21. The method according to example 20, wherein controlling the power provided to the induction heating arrangement includes controlling the power such that the temperature of the susceptor is adjusted based on one or more calibration values. Example 22: 22. The method according to example 20 or 21, wherein the one or more calibration values ​​include a first conductance value associated with a first calibration temperature of the susceptor and a second conductance value associated with a second calibration temperature of the susceptor. Example 23: 23. The method according to example 22, wherein controlling the power provided to the induction heating arrangement includes maintaining a conductance value associated with the susceptor between a first conductance value and a second conductance value. Example 24: 22. The method according to example 20 or 21, wherein the one or more calibration values ​​include a first resistance value associated with a first calibration temperature of the susceptor and a second resistance value associated with a second calibration temperature of the susceptor. Example 25: 25. The method according to example 24, wherein controlling the power provided to the induction heating arrangement includes maintaining a resistance value associated with the susceptor between a first resistance value and a second resistance value. Example 26: The method according to any of Examples 22-25, wherein the susceptor comprises a first susceptor material having a first Curie temperature and a second susceptor material having a second Curie temperature, the second Curie temperature being lower than the first Curie temperature, and the second calibration temperature corresponds to the second Curie temperature of the second susceptor material. Example 27: The method according to any of Examples 22-26, wherein controlling the power provided to the induction heating arrangement includes controlling the power such that the temperature of the susceptor is between a first calibration temperature and a second calibration temperature. Example 28: The method according to any of examples 22-27, wherein the first operating temperature is greater than or equal to a first calibration temperature and the second operating temperature is less than or equal to a second calibration temperature. Example 29: The method according to any of examples 22-28, wherein the first calibration temperature is between 150 degrees Celsius and 350 degrees Celsius, the second calibration temperature is between 200 degrees Celsius and 400 degrees Celsius, and the temperature difference between the first calibration temperature and the second calibration temperature is at least 50 degrees Celsius. Example 30: A method according to any of Examples 20 to 29, wherein the calibration process is performed during user operation of the aerosol generating device to generate the aerosol. Example 31: A method according to any of Examples 20 to 30, wherein the calibration process is performed periodically based on one or more of a predetermined duration, a predetermined number of user puffs, a predetermined number of temperature steps, and a measured voltage of the power supply. Example 32: The method according to any of Examples 22-31, wherein performing the calibration process includes the steps of: (i) controlling the power provided to the induction heating arrangement to increase the temperature of the susceptor; (ii) monitoring at least a current value of the induction heating arrangement; (iii) interrupting the provision of power to the induction heating arrangement when the current value reaches a maximum value, the current value at the maximum value corresponding to a second calibration temperature of the susceptor; and (iv) controlling the power provided to the induction heating arrangement to increase the temperature of the susceptor when a current value associated with the susceptor reaches a minimum value, the current value at the minimum value corresponding to a first calibration temperature of the susceptor. Example 33: 33. The method according to example 32, wherein monitoring at least the current value of the induction heating arrangement further comprises monitoring a voltage value of the induction heating arrangement. Example 34: The method according to example 32 or 33, further comprising repeating steps (i)-(iv) when the current value reaches a minimum value. Example 35: The method according to Example 34, further comprising, after repeating steps i) to iv), storing the conductance value corresponding to the current value at the maximum value as a second calibration value and storing the conductance value corresponding to the current value at the minimum value as the first calibration value, or storing the resistance value corresponding to the current value at the maximum value as the second calibration value and storing the resistance value corresponding to the current value at the minimum value as the first calibration value. Example 36: The method according to any of Examples 22-29, wherein performing the calibration process includes the steps of: i) controlling the power provided to the induction heating arrangement to increase the temperature of the susceptor; ii) monitoring a conductance or resistance value associated with the susceptor; iii) interrupting the provision of power to the induction heating arrangement when the conductance value reaches a maximum value or the resistance value reaches a minimum value, where the maximum conductance value or the minimum resistance value corresponds to a second calibration temperature of the susceptor; and iv) controlling the power provided to the induction heating arrangement to increase the temperature of the susceptor when the conductance value reaches a minimum value or the resistance value reaches a maximum value, where the minimum conductance value or the maximum resistance value corresponds to a first calibration temperature of the susceptor. Example 37: 37. The method according to example 36, further comprising repeating steps i) to iv) when the conductance value reaches a minimum or the resistance value reaches a maximum. Example 38: The method according to example 37, further comprising, after repeating steps (i)-(iv), storing the maximum conductance value as a second conductance value and storing the minimum conductance value as a first calibration value, or storing the minimum resistance value as a second calibration value and storing the maximum resistance value as the first calibration value. Example 39: The method according to any of Examples 22-38, further comprising performing a pre-heating process to heat the susceptor to the first calibration temperature, the pre-heating process having a predetermined duration. Example 40: The method according to Example 39, wherein performing the preheating process includes controlling power provided to the induction heating arrangement to increase the temperature of the susceptor, monitoring at least a current value associated with the susceptor, and interrupting the provision of power to the induction heating arrangement when the current value reaches a minimum value, the current value at the minimum value corresponding to a first calibration temperature of the susceptor. Example 41: A method according to Example 40, comprising, when the current value reaches a minimum value during a predetermined duration of the preheating process, interrupting the provision of power to the induction heating arrangement to reduce the temperature of the susceptor, and then resuming the provision of power to the induction heating arrangement to increase the temperature of the susceptor to the first calibration temperature. Example 42: The method according to example 41, wherein interrupting the provision of power to the induction heating arrangement and resuming the provision of power to the induction heating arrangement is repeated for a predetermined duration of the preheating process. Example 43: The method according to example 40, further comprising: stopping operation of the aerosol generating device if the current value of the susceptor does not reach a minimum value for a predetermined duration of the preheating process. Example 44: The method according to Example 39, wherein performing the pre-heating process includes controlling power provided to the induction heating arrangement to increase the temperature of the susceptor, monitoring a conductance or resistance value associated with the susceptor, and interrupting the provision of power to the induction heating arrangement when the conductance value reaches a minimum value or the resistance value reaches a maximum value, wherein the conductance value at the minimum value or the resistance value at the maximum value corresponds to a first calibration temperature of the susceptor. Example 45: The method according to Example 44, wherein if the conductance value reaches a minimum value or the resistance value reaches a maximum value during a predetermined duration of the preheating process, the method further includes interrupting the provision of power to the induction heating arrangement to reduce the temperature of the susceptor, and then resuming the provision of power to the induction heating arrangement to raise the temperature of the susceptor to the first calibration temperature. Example 46: The method according to example 45, wherein interrupting the provision of power to the induction heating arrangement and resuming the provision of power to the induction heating arrangement is repeated for a predetermined duration of the preheating process. Example 47: 45. The method according to example 44, further comprising stopping operation of the aerosol generating device when the conductance value does not reach a minimum value or the resistance value does not reach a maximum value during a predetermined duration of the preheating process. Example 48: The method according to any of Examples 14-47, further comprising measuring a DC current drawn from the power supply at an input side of the DC / AC converter, wherein a conductance value and a resistance value associated with the susceptor are determined based on a DC supply voltage of the power supply and from the DC current drawn from the power supply. Example 49: 49. The method according to example 48, further comprising measuring a DC supply voltage of the power supply at an input side of the DC / AC converter. Example 50: The method according to any of Examples 1-49, wherein the first operating temperature is between 150 degrees Celsius and 330 degrees Celsius, the second operating temperature is between 200 degrees Celsius and 400 degrees Celsius, and the temperature difference between the first operating temperature and the second operating temperature is at least 30 degrees Celsius. Example 51: The method according to Examples 1-50, wherein the gradual increase in temperature of the susceptor includes a first temperature step having a temperature corresponding to the first operating temperature, the first operating temperature being 330 degrees Celsius, a second temperature step having a temperature of 340 degrees Celsius, a third temperature step having a temperature of 345 degrees Celsius, a fourth temperature step having a temperature of 355 degrees Celsius, and a fifth temperature step having a temperature corresponding to the second operating temperature, the second operating temperature being 380 degrees Celsius. Example 52: The method according to any of Examples 1-51, wherein the susceptor and the aerosol-forming substrate form part of an aerosol-generating article, and the aerosol-generating device is configured to removably receive the aerosol-generating article. Example 53: 1. An aerosol generating apparatus comprising: a power supply for providing a DC supply voltage and a DC current; and power supply electronics connected to the power supply, the power supply electronics including a DC / AC converter; an inductor connected to the DC / AC converter for generating an alternating magnetic field when energized by alternating current from the DC / AC converter, the inductor being coupleable to a susceptor, the susceptor being configured to heat an aerosol-forming substrate; and a controller configured to control power provided to the power supply electronics to incrementally increase the temperature of the susceptor from a first operating temperature to a second operating temperature. Example 54: 54. The aerosol generating apparatus according to embodiment 53, wherein the stepwise increase in temperature of the susceptor comprises at least three successive temperature steps, each temperature step having a duration. Example 55: An aerosol generating apparatus according to Example 54, wherein the controller is configured to control the power provided to the power electronics to maintain the temperature of the susceptor at a predetermined temperature during the duration of each temperature step. Example 56: 56. An aerosol generating device according to embodiment 54 or 55, wherein the duration is at least 10 seconds. Example 57: The aerosol generating apparatus according to Example 54 or 55, wherein the duration is 30 seconds to 200 seconds. Example 58: The aerosol generating apparatus according to Example 54 or 55, wherein the duration is 40 seconds to 160 seconds. Example 59: 56. An aerosol generating device according to embodiment 54 or 55, wherein the duration corresponds to a predetermined number of user puffs. Example 60: An aerosol generating device according to any of Examples 54 to 59, wherein the first temperature step has a longer duration than the subsequent temperature steps. Example 61: An aerosol generating apparatus according to any one of Examples 54 to 58, wherein the duration is predetermined. Example 62: An aerosol generating apparatus according to any of Examples 53 to 61, wherein the stepwise increase in temperature of the susceptor includes more than two temperature steps and less than fourteen temperature steps. Example 63: An aerosol generating apparatus according to any of Examples 53 to 61, wherein the stepwise increase in temperature of the susceptor includes more than two temperature steps and less than eight temperature steps. Example 64: The aerosol generating apparatus according to any of Examples 53 to 63, wherein the first operating temperature is sufficient for the aerosol-forming substrate to form an aerosol. Example 65: An aerosol generating device according to any of Examples 53 to 64, wherein the controller is configured to determine a conductance value or a resistance value associated with the susceptor and control the power provided to the power supply electronics based on the determined conductance value or the determined resistance value. Example 66: An aerosol generating device according to any of Examples 53 to 65, wherein controlling the power provided to the power supply electronic circuitry includes interrupting the provision of power provided to the DC / AC converter when the determined conductance value exceeds a preset threshold conductance value and resuming resistance of the power provided to the DC / AC converter when the determined conductance value falls below the preset threshold conductance value, or controlling the power provided to the power supply electronic circuitry includes interrupting the provision of power provided to the DC / AC converter when the determined resistance value falls below the preset threshold resistance value and resuming resistance of the power provided to the DC / AC converter when the determined resistance value exceeds the preset threshold conductance value. Example 67: An aerosol generating device according to any of Examples 53 to 66, wherein the power supply electronic circuit is configured to intermittently supply power from the power source to the inductor via a DC / AC converter. Example 68: An aerosol generating device according to any of Examples 53 to 67, wherein the power supply electronic circuit is configured to supply power from the power supply to the inductor via a DC / AC converter as multiple pulses, each pulse being separated by a time interval. Example 69: 69. An aerosol generating device according to Example 68, wherein controlling the power provided to the power supply electronic circuitry includes controlling the time interval between each of the multiple pulses. Example 70: 69. An aerosol generating device according to Example 68, wherein controlling the power provided to the power electronics includes controlling the length of each pulse of the plurality of pulses. Example 71: An aerosol generating device according to any of Examples 53 to 70, wherein the controller is further configured to perform a calibration process to measure one or more calibration values ​​associated with the susceptor. Example 72: 72. The aerosol generating apparatus according to embodiment 71, wherein controlling the power provided to the power electronics includes controlling the power such that the temperature of the susceptor is adjusted based on one or more calibration values. Example 73: An aerosol generating apparatus according to example 71 or 72, wherein the one or more calibration values ​​include a first conductance value associated with a first calibration temperature of the susceptor and a second conductance value associated with a second calibration temperature of the susceptor. Example 74: An aerosol generating device according to Example 71, wherein controlling the power provided to the power electronics includes maintaining a conductance value associated with the susceptor between a first conductance value and a second conductance value. Example 75: An aerosol generating device according to example 71 or 72, wherein the one or more calibration values ​​include a first resistance value associated with a first calibration temperature of the susceptor and a second resistance value associated with a second calibration temperature of the susceptor. Example 76: 76. The aerosol generating apparatus according to example 75, wherein controlling the power provided to the induction heating arrangement comprises maintaining a resistance value associated with the susceptor between a first resistance value and a second resistance value. Example 77: An aerosol generating apparatus according to any of Examples 73 to 76, wherein the second calibration temperature of the susceptor corresponds to the Curie temperature of a material of the susceptor. Example 78: An aerosol generating apparatus according to any of Examples 73 to 77, wherein controlling the power provided to the power electronics includes controlling the power so that the temperature of the susceptor is between a first calibration temperature and a second calibration temperature. Example 79: An aerosol generating device according to any of Examples 73 to 78, wherein the first operating temperature is equal to or greater than the first calibration temperature and the second operating temperature is equal to or less than the second calibration temperature. Example 80: An aerosol generating device according to any of Examples 73 to 79, wherein the first calibration temperature is between 150 degrees Celsius and 350 degrees Celsius, the second calibration temperature is between 200 degrees Celsius and 400 degrees Celsius, and the temperature difference between the first calibration temperature and the second calibration temperature is at least 50 degrees Celsius. Example 81: An aerosol generating device according to any of Examples 71 to 80, wherein the calibration process is performed during user operation of the aerosol generating device to generate the aerosol. Example 82: An aerosol generating device according to any of Examples 71 to 81, wherein the calibration process is performed periodically based on one or more of a predetermined duration, a predetermined number of user puffs, a predetermined number of temperature steps, and a measured power supply voltage. Example 83: An aerosol generating apparatus according to any of Examples 71 to 82, wherein carrying out the calibration process includes the steps of: i) controlling the power provided to the power supply electronic circuit to increase the temperature of the susceptor; ii) monitoring at least a current value of the power supply electronic circuit; iii) interrupting the provision of power to the power supply electronic circuit when at least the current value reaches a maximum value, the current value at the maximum value corresponding to a second calibration temperature; and iv) controlling the power provided to the power supply electronic circuit when the current value of the power supply electronic circuit reaches a minimum value to increase the temperature of the susceptor, the current value at the minimum value corresponding to the first calibration temperature. Example 84: 84. An aerosol generating device according to Example 83, wherein monitoring at least the current value of the power supply electronic circuit further comprises monitoring a voltage value of the power supply electronic circuit. Example 85: An aerosol generating apparatus according to embodiment 83 or 84, wherein performing the calibration process further comprises repeating steps i) to iv) when at least the current value associated with the susceptor reaches a minimum value. Example 86: An aerosol generating device according to Example 85, wherein the controller is further configured to, after repeating steps i) to iv), store a conductance value corresponding to the current value at the maximum value as a second calibration value and store a conductance value corresponding to the current value at the minimum value as a first calibration value, or store a resistance value corresponding to the current value at the maximum value as a second calibration value and store a resistance value corresponding to the current value at the minimum value as the first calibration value. Example 87: The aerosol generating apparatus according to any of Examples 71 to 82, wherein performing the calibration process includes the steps of: i) controlling the power provided to the induction heating arrangement to increase the temperature of the susceptor; ii) monitoring a conductance value or a resistance value associated with the susceptor; iii) interrupting the provision of power to the induction heating arrangement when the conductance value reaches a maximum value or the resistance value reaches a minimum value, where the maximum conductance value or the minimum resistance value corresponds to a second calibration temperature of the susceptor; and iv) controlling the power provided to the induction heating arrangement to increase the temperature of the susceptor when the conductance value reaches a minimum value or the resistance value reaches a maximum value, where the minimum conductance value or the maximum resistance value corresponds to a first calibration temperature of the susceptor. Example 88: An aerosol generating device according to Example 87, wherein performing the calibration process further comprises repeating steps i) to iv) when the conductance value reaches a minimum or the resistance value reaches a maximum. Example 89: An aerosol generating device according to Example 88, wherein the controller is further configured to store the conductance value at the maximum value or the resistance value at the minimum value as a second calibration value after repeating steps i) to iv), and to store the conductance value at the minimum value or the resistance value at the maximum value as a first calibration value. Example 90: An aerosol generating apparatus according to any of Examples 66-78, wherein the controller is further configured to perform a pre-heating process to heat the susceptor to a first calibration temperature, the pre-heating process having a predetermined duration. Example 91: An aerosol generating apparatus according to Example 90, wherein performing a preheating process includes controlling power provided to the power supply electronics to increase the temperature of the susceptor, monitoring at least a current value of the power supply electronics, and interrupting the provision of power to the power supply electronics when at least the current value reaches a minimum value, wherein the conductance value at the minimum value corresponds to a first calibration temperature of the susceptor. Example 92: An aerosol generating device according to Example 91, wherein performing the pre-heating process further comprises interrupting the provision of power to the power supply electronic circuitry to reduce the temperature of the susceptor when at least the current value reaches a minimum value during a predetermined duration of the pre-heating process, and then resuming the provision of power to the power supply electronic circuitry to increase the temperature of the susceptor to the first calibration temperature. Example 93: 93. An aerosol generating device according to claim 92, wherein interrupting the supply of power to the power supply electronic circuitry and resuming the supply of power to the power supply electronic circuitry is repeated for a predetermined duration of the pre-heating process. Example 94: An aerosol generating apparatus according to any of claims 91 to 93, wherein the controller is further configured to generate a control signal to stop operation of the aerosol generating apparatus if at least the current value of the susceptor does not reach a minimum value during a predetermined duration of the preheating process. Example 95: 91. An aerosol generating apparatus according to claim 90, wherein performing a pre-heating process comprises controlling power provided to the induction heating arrangement to increase the temperature of the susceptor, monitoring a conductance or resistance value associated with the susceptor, and interrupting the provision of power to the induction heating arrangement when the conductance value reaches a minimum value or the resistance value reaches a maximum value, wherein the current value at the minimum value or the resistance value at the maximum value corresponds to a first calibration temperature of the susceptor. Example 96: An aerosol generating apparatus according to Example 95, wherein performing the pre-heating process further comprises, if the conductance value reaches a minimum value or the resistance value reaches a maximum value during a predetermined duration of the pre-heating process, interrupting the provision of power to the induction heating arrangement to reduce the temperature of the susceptor, and then resuming the provision of power to the induction heating arrangement to raise the temperature of the susceptor to the first calibration temperature. Example 97: An aerosol generating apparatus according to Example 96, wherein interrupting the supply of power to the induction heating arrangement and resuming the supply of power to the induction heating arrangement is repeated for a predetermined duration of the pre-heating process. Example 98: An aerosol generating device according to Example 95, wherein performing the pre-heating process further comprises stopping operation of the aerosol generating device if the conductance value does not reach a minimum value or the resistance value does not reach a maximum value during a predetermined duration of the pre-heating process. Example 99: An aerosol generating apparatus according to any of Examples 65 to 98, further comprising a current sensor at the input side of the DC / AC converter configured to measure a DC current drawn from the power supply, and wherein a conductance value and a resistance value associated with the susceptor are determined from a DC supply voltage of the power supply and the DC current drawn from the power supply. Example 100: An aerosol generating device according to Example 99, further comprising a voltage sensor configured to measure the DC supply voltage of the power source at the input side of the DC / AC converter. Example 101: An aerosol generating apparatus according to any of Examples 53 to 100, wherein the first operating temperature is between 150 degrees Celsius and 330 degrees Celsius, the second operating temperature is between 200 degrees Celsius and 400 degrees Celsius, and the temperature difference between the first operating temperature and the second operating temperature is at least 30 degrees Celsius. Example 102: An aerosol generating apparatus according to any of Examples 53 to 101, wherein the gradual increase in temperature of the susceptor includes a first temperature step having a temperature corresponding to the first operating temperature, the first operating temperature being 330 degrees Celsius, a second temperature step having a temperature of 340 degrees Celsius, a third temperature step having a temperature of 345 degrees Celsius, a fourth temperature step having a temperature of 355 degrees Celsius, and a fifth temperature step having a temperature corresponding to the second operating temperature, the second operating temperature being 380 degrees Celsius. Example 103: An aerosol generating apparatus according to any of Examples 53 to 102, wherein the power electronics further comprises a matching network for matching the impedance of the inductor with the impedance of the susceptor. Example 104: An aerosol generating apparatus according to any of Examples 53 to 103, further comprising a housing having a cavity configured to removably receive an aerosol-generating article, the aerosol-generating article comprising an aerosol-generating substrate and a susceptor. Example 105: An aerosol-generating system comprising the aerosol-generating device according to any one of Examples 53 to 104 and an aerosol-generating article, the aerosol-generating article including an aerosol-generating substrate and a susceptor. Example 106: The aerosol generating system according to example 105, wherein the susceptor comprises a first susceptor material and a second susceptor material, the first susceptor material being positioned in physical contact with the second susceptor material. Example 107: The aerosol generating system according to Example 106, wherein the first susceptor material is one of aluminum, iron, and stainless steel, and the second susceptor material is nickel or a nickel alloy. Example 108: The aerosol generating system according to embodiment 106 or 107, wherein the first susceptor material has a first Curie temperature and the second susceptor material has a second Curie temperature, the second Curie temperature being lower than the first Curie temperature. Example 109: The aerosol generating system according to example 108, wherein the second calibration temperature corresponds to the Curie temperature of the second susceptor material.

[0090] The embodiments will now be further described with reference to the figures. [Brief description of the drawings]

[0091] [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 shows the temperature profile of the susceptor during operation of the aerosol generating device. [Figure 8] FIG. 8 is a flow diagram illustrating a method for controlling aerosol generation in the aerosol generating device of FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0092] FIG. 1 shows an aerosol-generating article 100. The aerosol-generating article 100 comprises four coaxially aligned elements, namely, an aerosol-forming substrate 110, a support element 120, an aerosol cooling element 130, and a mouthpiece 140. Each of the four elements is a substantially cylindrical element, each having substantially the same diameter. The four elements are arranged consecutively and surrounded by an outer wrapper 150 to form a cylindrical rod. An elongated susceptor 160 is located within and in contact with the aerosol-forming substrate 110. The susceptor 160 has a length approximately the same as the length of the aerosol-forming substrate 110 and is located along the radial central axis of the aerosol-forming substrate 110.

[0093] The susceptor 160 comprises at least two different materials. The susceptor 160 is preferably in the form of an elongated strip having a length of 12 mm and a width of 4 mm. The susceptor 160 comprises 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 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 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 160 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.

[0094] The aerosol-generating article 100 has a proximal or oral end 170 which a user inserts into the mouth during use, and a distal end 180 which is at the opposite end of the aerosol-generating article 100 to the oral end 170. The total length of the assembled aerosol-generating article 100 is preferably about 45 mm, and its diameter is about 7.2 mm.

[0095] In use, air is drawn through the aerosol-generating article 100 by a user from the distal end 180 to the oral end 170. The distal end 180 of the aerosol-generating article 100 may also be described as the upstream end of the aerosol-generating article 100, and the oral end 170 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 170 and the distal end 180 may be described as being upstream of the oral end 170, or alternatively downstream of the distal end 180. The aerosol-forming substrate 110 is located at the distal or upstream end 180 of the aerosol-generating article 100.

[0096] The support element 120 is located immediately downstream of the aerosol-forming substrate 110 and abuts the aerosol-forming substrate 110. The support element 120 may be a hollow cellulose acetate tube. The support element 120 positions the aerosol-forming substrate 110 at the distal-most end 180 of the aerosol-generating article 100. The support element 120 also acts as a spacer to space the aerosol-cooling element 130 of the aerosol-generating article 100 from the aerosol-forming substrate 110.

[0097] The aerosol cooling element 130 is located immediately downstream of and abuts the support element 120. In use, volatile material emitted from the aerosol-forming substrate 110 passes along the aerosol cooling element 130 towards the mouth end 170 of the aerosol-generating article 100. The volatile material may cool within the aerosol cooling element 130 to form an aerosol that is inhaled by the user. The aerosol cooling element 130 may include an assembly of crimped sheets of polylactic acid surrounded by a wrapper 190. The assembly of crimped sheets of polylactic acid defines a plurality of longitudinal channels extending along the length of the aerosol cooling element 130.

[0098] Mouthpiece 140 is located immediately downstream of and abuts aerosol cooling element 130. Mouthpiece 140 includes a conventional cellulose acetate tow filter with low filtration efficiency.

[0099] To assemble the aerosol-generating article 100, the four elements 110, 120, 130, and 140 described above are aligned and tightly wrapped within an outer wrapper 150, which may be a conventional cigarette paper. A susceptor 160 may be inserted into the aerosol-forming substrate 110 during the process used to form the aerosol-forming substrate 110, prior to assembling the elements to form a rod.

[0100] The aerosol-generating article 100 shown in Figure 1 is designed to engage with an aerosol-generating device, 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 160. 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 110 of the aerosol-generating article 100 is located adjacent to the inductor 240 such that the susceptor 160 of the aerosol-generating article 100 is located within this alternating magnetic field. When the alternating magnetic field penetrates the susceptor 160, the alternating magnetic field causes the susceptor 160 to heat up. For example, eddy currents are generated within the susceptor 160 which, as a result, is heated. Further heating is provided by magnetic hysteresis losses within the susceptor 160. The heated susceptor 160 heats the aerosol-forming substrate 110 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, that 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 160.

[0109] FIG. 6 shows the DC current I drawn from the power supply 310 over time as the temperature of the susceptor 160 (shown by the dashed line) increases. DC The relationship between the DC current I drawn from the power supply 310 is shown. DC is measured at the input of the DC / AC converter 340. For the purposes of this figure, the voltage V DC can be assumed to be approximately constant. When the susceptor 160 is inductively heated, the apparent resistance of the susceptor 160 increases. This increase in resistance is proportional to the DC current I drawn from the power supply 310.DC , which at constant voltage decreases as the temperature of the susceptor 160 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 160 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 160. 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 DC A temporary increase in current occurs. This is seen as a valley (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 as a hill (local maximum) in FIG. 6. 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 160 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 160 will flow against the resistance of the susceptor 160, causing continued Joule heating of the susceptor 160, 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 160.

[0110] Thus, as can be seen from FIG. 6, the apparent resistance of the susceptor 160 (and the corresponding current I drawn from the power supply 310) DC) may vary with the temperature of the susceptor 160 in a strictly monotonic relationship over a particular temperature range of the susceptor 160. The strictly monotonic relationship allows for an unambiguous determination of the temperature of the susceptor 160 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 160 and the apparent resistance allows the temperature of the susceptor 160, and therefore the temperature of the aerosol-forming substrate 110, to be determined and controlled. The apparent resistance of the susceptor 160 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 DC is monitored by the controller 330. Preferably, the DC current drawn from the power supply 310, I DC and DC supply voltage V DC 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 160 by maintaining the measured conductance value or the measured resistance value at a target value that corresponds to a target operating temperature of the susceptor 160. 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 160 and the temperature of the susceptor 160, 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 (the hill 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 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 160, 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 power supply to the heating arrangement 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 continuously generates an alternating current that heats the susceptor 160 and simultaneously generates 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 VDC 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 160 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 160. The probing pulses are separate power pulses that do not heat the susceptor 160, 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 perform a calibration process to obtain calibration values ​​where the conductance is measured at known temperatures of the susceptor 160. 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 process is performed each time the user operates the aerosol generating device 200, e.g., each time the user inserts an aerosol-generating article 100 into the aerosol generating device 200.

[0118] During the calibration process, the controller 330 controls the DC / AC converter 340 to continuously or intermittently supply power to the inductor 240 to heat the susceptor 160. The controller 330 controls the current I drawn by the power supply. DC , and possibly the supply voltage V DC The conductance or resistance associated with the susceptor 160 is monitored by measuring the current I. As described above in connection with FIG. 6, as the susceptor 160 heats up, the measured current decreases until a first turning point is reached at which the current increases. This first turning point corresponds to a local minimum conductance value (local maximum resistance value). The controller 330 may record the local minimum of conductance (or local maximum of resistance) as the 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 160 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 110 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 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 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 160 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 power supply to the inductor 240, resulting in a decrease in the temperature of the susceptor 160 and a corresponding decrease in conductance.

[0120] This process of continuously heating the susceptor 160 to obtain the first and second calibration values ​​due to the shape of the graph may be repeated at least once. After interrupting the power supply to the inductor 240, the controller 330 continues to monitor the conductance (or resistance) until a third turning point corresponding to a second minimum conductance value (second maximum resistance value) is observed. When the third turning point is detected, the controller 330 controls the DC / AC converter 340 to continuously supply power to the inductor 240 until a fourth turning point corresponding to a second maximum conductance value (second minimum resistance value) is detected. The controller 330 stores the conductance or resistance value at or shortly after the third turning point as the first calibration value and the conductance or resistance value at the fourth turning point as the second calibration value. The repetition of the measurement of the turning points corresponding to the minimum and maximum measured current significantly improves subsequent temperature regulation during user operation of the device to generate an aerosol. Preferably, the controller 330 adjusts the power based on the conductance or resistance value obtained from the second maximum and second minimum, which is more reliable since the heat requires more time to disperse within the aerosol-forming substrate 110 and the susceptor 160.

[0121] To further improve the reliability of the calibration process, the controller 310 may be optionally programmed to perform a pre-heating process prior to the calibration process. For example, if the aerosol-forming substrate 110 is particularly dry or in similar conditions, the calibration may be performed before heat spreads into the aerosol-forming substrate 110, reducing the reliability of the calibration value. If the aerosol-forming substrate 110 is wet, the susceptor 160 will take longer to reach the valley temperature (depending on the moisture content of the substrate 110).

[0122] To perform the preheating process, the controller 330 is configured to continuously supply power to the inductor 240. As described above, the current begins to decrease with increasing temperature of the susceptor 160 and reaches a minimum value. At this stage, the controller 330 is configured to wait a predetermined period of time to allow the susceptor 160 to cool before continuing the heating. Thus, the controller 330 controls the DC / AC converter 340 to interrupt the supply of power to the inductor 240. After the predetermined period of time, the controller 330 controls the DC / AC converter 340 to supply power until the minimum value is reached. At this point, the controller controls the DC / AC converter 340 to again interrupt the supply of power to the inductor 240. The controller 330 again waits the same predetermined time to allow the susceptor 160 to cool before continuing the heating. This heating and cooling of the susceptor 160 is repeated for the predetermined period of the preheating process. The predetermined duration of the preheating process is preferably 11 seconds. Following the pre-defined combined duration of the pre-heat process, the calibration process is preferably 20 seconds.

[0123] If the aerosol-forming substrate 110 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 time. If the aerosol-forming substrate 110 is wet, the first minimum of the pre-heating process is reached towards the end of the predetermined time. Thus, carrying out the pre-heating process for a predetermined duration ensures that, regardless of the physical state of the substrate 110, the substrate 110 has had enough time to reach a minimum temperature in order to be ready to continue applying power to reach the first maximum. This allows for calibration as early as possible without the risk that the substrate 110 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 110, is not suitable for use in the aerosol-generating device 200. For example, the aerosol-generating article 100 may include an aerosol-forming substrate 110 that is different from or of 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 stop operation of the aerosol-generating device 200.

[0125] The pre-heating process may be performed 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 the aerosol-generating article 100 in the aerosol generating device 200, and the pre-heating process may be performed in response to detecting the presence of the aerosol-generating article 100 in the cavity 220 of the aerosol generating device 200.

[0126] 7 is a graph of conductance versus time illustrating a heating profile of the susceptor 160. The graph shows two successive stages of heating, a first heating stage 710, which includes the pre-heating process 710A and the calibration process 710B described above, and a second heating stage 720, which corresponds to user operation of the aerosol generating device 200 to generate an aerosol. Although FIG. 7 is shown as a graph of conductance versus time, it should be understood that the controller 330 may be configured to control the heating of the susceptor during the first heating stage 710 and the second heating stage 720 based on measured resistance or current, as described above.

[0127] Furthermore, while the techniques for controlling the heating of the susceptor during the first heating stage 710 and the second heating stage 720 have been described above based on determined conductance values ​​or determined resistance values ​​associated with the susceptor, it should be understood that the above-described techniques may be implemented based on values ​​of current measured at the input of the DC / AC converter 340.

[0128] As can be seen from FIG. 7, the second heating stage 720 includes a number of conductance steps corresponding to a number of temperature steps from a first operating temperature of the susceptor 160 to a second operating temperature of the susceptor 160. The first operating temperature of the susceptor is the lowest temperature at which the aerosol-forming substrate forms an aerosol in a volume and amount sufficient for a user to have a satisfactory experience when inhaled. The second operating temperature of the susceptor is the highest temperature to which it is desirable to heat the aerosol-forming substrate in order for the user to inhale the aerosol. The first operating temperature of the susceptor 160 is equal to or greater than a first calibration temperature of the susceptor 160 at the valley of the current plot shown in FIG. 6. The first operating temperature may be between 150 degrees Celsius and 330 degrees Celsius. The second operating temperature of the susceptor is equal to or less than a second calibration temperature of the susceptor 160 at the Curie temperature of the second susceptor material. The second operating temperature may be between 200 degrees Celsius and 400 degrees Celsius. The difference between the first operating temperature and the second operating temperature is at least 50 degrees Celsius. The first operating temperature of the susceptor is the temperature at which the aerosol-forming substrate 110 forms an aerosol such that an aerosol is formed during each temperature step.

[0129] It should be understood that the number of temperature steps shown in FIG. 7 is exemplary and the second heating stage 720 includes at least three consecutive temperature steps, preferably two to fourteen temperature steps, and most preferably three to eight temperature steps. Each temperature step may have a predetermined duration. The duration of the first temperature step is preferably longer than the duration of the subsequent temperature steps. The duration of each temperature step is preferably longer than 10 seconds, preferably between 30 seconds and 200 seconds, more preferably between 40 seconds and 160 seconds. The duration of each temperature step may correspond to a predetermined number of user puffs. Preferably, the first temperature step corresponds to four user puffs and each subsequent temperature step corresponds to one user puff.

[0130] For the duration of each temperature step, the temperature of susceptor 160 is maintained at the target operating temperature corresponding to each temperature step. Thus, during the duration of each temperature step, controller 330 controls the power supply to heating arrangement 320 such that the conductance is maintained at a value corresponding to the target operating temperature of each of the above-described temperature steps. The target conductance value for each temperature step may be stored in the memory of controller 330.

[0131] As an example, the second heating stage 720 includes the following five temperature steps, a period of 160 seconds, and a first temperature step with a target conductance value of G Target =G Lower +(0.09 × ΔG), a period of 40 seconds, and a second temperature step with a target conductance value of G Target =G Lower +(0.25 × ΔG), a period of 40 seconds, and a third temperature step with a target conductance value of G Target =G Lower +(0.4 × ΔG), a period of 40 seconds, and a fourth temperature step with a target conductance value of G Target =G Lower +(0.56 × ΔG), and a fifth temperature step with a target conductance value of G for a period of 85 seconds and G Target =G Lower +(0.75 × ΔG). These temperature steps may correspond to temperatures of 330 degrees Celsius, 340 degrees Celsius, 345 degrees Celsius, 355 degrees Celsius, and 380 degrees Celsius. FIG. 8 is a flowchart of a method 800 for controlling aerosol generation in aerosol generator 200. As described above, controller 330 may be programmed to implement method 800.

[0132] The method begins at step 810, where the controller 330 detects user operation of the aerosol generating device 200 to generate aerosol. Detecting user operation of the aerosol generating device 200 may include detecting a user input, such as, for example, user activation of the aerosol generating device 200. Additionally or alternatively, detecting user operation of the aerosol generating device 200 may include detecting that an aerosol-generating article 100 is inserted into the aerosol generating device 200.

[0133] In response to detecting user action at step 810, controller 330 may be configured to perform any pre-heating process as described above. At the end of the pre-defined duration of the pre-heating process, controller 330 performs a calibration process (step 820) as described above. Alternatively, controller 330 may be configured to proceed to step 820 in response to detecting user action at step 810. After completion of the calibration process, controller 330 performs a second heating stage at step 840 in which an aerosol is generated.

[0134] 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 properties 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. 1. A method for controlling aerosol generation in an aerosol generating device, the device comprising an inductive heating arrangement and a power source for providing power to the inductive heating arrangement, the method comprising: A method comprising controlling the power provided to the induction heating arrangement to incrementally increase a temperature of a susceptor associated with the aerosol generating device from a first operating temperature to a second operating temperature, the susceptor being configured to heat an aerosol-forming substrate, the power being controlled based on a measured resistance, conductance, or current associated with the susceptor, the measured resistance, conductance, or current associated with the susceptor being determined based on a DC current drawn from the power source.

2. The method of claim 1 , wherein the stepwise increase in temperature of the susceptor includes at least three successive temperature steps, each temperature step having a duration.

3. The method of claim 2 , wherein the duration is at least 10 seconds.

4. The method of claim 2 , wherein the duration corresponds to a predetermined number of user puffs.

5. The method of any of claims 1 to 4, wherein the first operating temperature is sufficient for the aerosol-forming substrate to form an aerosol.

6. The method according to any one of claims 1 to 5, wherein the susceptor and the aerosol-forming substrate form part of an aerosol-generating article, and the aerosol-generating device is configured to removably receive the aerosol-generating article.

7. The method of any of claims 1 to 6, further comprising performing a calibration process to measure one or more calibration values ​​associated with the susceptor.

8. The method of claim 7 , wherein controlling the power provided to the induction heating arrangement comprises controlling the power such that the temperature of the susceptor is adjusted based on the one or more calibration values.

9. the one or more calibration values ​​include a first conductance value associated with a first calibrated temperature of the susceptor and a second conductance value associated with a second calibrated temperature of the susceptor; or 9. The method of claim 7 or 8, wherein the one or more calibration values ​​include a first resistance value associated with a first calibration temperature of the susceptor and a second resistance value associated with a second calibration temperature of the susceptor.

10. 10. The method of claim 9, wherein the susceptor comprises a first susceptor material having a first Curie temperature and a second susceptor material having a second Curie temperature, the second Curie temperature being lower than the first Curie temperature, and the second calibration temperature corresponds to the second Curie temperature of the second susceptor material.

11. 11. The method of claim 9 or 10, wherein controlling the power provided to the induction heating arrangement comprises controlling the power such that the temperature of the susceptor is between the first calibration temperature and the second calibration temperature.

12. The method of any of claims 7 to 11, wherein the calibration process is performed during user operation of the aerosol generating device to generate an aerosol.

13. The method according to any of claims 9 to 12, further comprising performing a pre-heating process to heat the susceptor to the first calibration temperature, the pre-heating process having a predetermined duration.

14. A power supply for providing a DC supply voltage and a DC current, and power electronics connected to the power supply, the power electronics comprising: DC / AC converter, an inductor connected to the DC / AC converter for generating an alternating magnetic field when energized by an alternating current from the DC / AC converter, the inductor being couplable to a susceptor, the susceptor being configured to heat an aerosol-forming substrate; and An aerosol generating device comprising: a controller configured to control the power provided to the power supply electronics to gradually increase the temperature of the susceptor from a first operating temperature to a second operating temperature, wherein the power is controlled based on a measured resistance, conductance, or current associated with the susceptor, and the measured resistance, conductance, or current associated with the susceptor is determined based on a DC current drawn from the power supply.

15. the stepwise increase in temperature of the susceptor includes at least three successive temperature steps, each temperature step having a duration; 15. The aerosol generating device of claim 14, wherein the controller is configured to control the power provided to the power electronics to maintain the temperature of the susceptor at a predetermined temperature during the duration of each temperature step.

16. 16. An aerosol generating device as described in claim 14 or 15, further comprising a current sensor at the input side of the DC / AC converter configured to measure the DC current drawn from the power supply, and wherein the conductance value and the resistance value associated with the susceptor are determined from the DC supply voltage of the power supply and the DC current drawn from the power supply.

17. 17. The aerosol generating device of claim 16, further comprising a voltage sensor at the input side of the DC / AC converter configured to measure the DC supply voltage of the power source.

18. 18. An aerosol generating device according to any one of claims 14 to 17, wherein the controller is further configured to perform a calibration process to measure one or more calibration values ​​associated with the susceptor.

19. the one or more calibration values ​​include a first conductance value associated with a first calibrated temperature of the susceptor and a second conductance value associated with a second calibrated temperature of the susceptor; or 20. The aerosol generating device of claim 18, wherein the one or more calibration values ​​include a first resistance value associated with a first calibration temperature of the susceptor and a second resistance value associated with the second calibration temperature of the susceptor.

20. An aerosol generating system comprising the aerosol generating device according to any one of claims 14 to 19 and an aerosol generating article, the aerosol generating article including the aerosol generating substrate and the susceptor.

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