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

Abstract

A method (800) for controlling aerosol generation in an aerosol generating apparatus (200) includes performing a calibration process (820) to measure a calibration value associated with the susceptor (160). The heating arrangement (320) is configured to inductively heat the susceptor (160) based on the calibration value. The calibration process includes i) controlling power provided to the heating arrangement (320) to increase a temperature of the susceptor (160), ii) monitoring a conductance or resistance value associated with the susceptor (160), iii) interrupting the provision of power to the heating arrangement (320) when the conductance value reaches a maximum value or the resistance value reaches a minimum value, and iv) monitoring the conductance value associated with the susceptor (160) until the conductance value reaches a minimum value or the resistance value reaches a maximum value.

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 comprising 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 comprise 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 includes an inductor configured to be inductively coupled to the susceptor. The inductor generates an alternating magnetic field that causes the susceptor to heat. 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 for such an aerosol-generating device to accurately monitor and control the temperature of the susceptor to ensure optimal aerosol generation and delivery 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 one aspect of the invention, there is provided a method for controlling aerosol generation in an aerosol generating apparatus comprising a heating arrangement and a power source for providing power to the heating arrangement, the method including performing a calibration process to measure a calibration value associated with a susceptor, the heating arrangement being configured to inductively heat the susceptor based on the calibration value. The calibration process includes the steps of: i) controlling the power provided to the 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 heating arrangement when the conductance value reaches a maximum value or interrupting the provision of power to the heating arrangement when the resistance value reaches a minimum value, where the conductance value at maximum conductance or the resistance value at minimum resistance is a second calibration value associated with the susceptor; and iv) monitoring the conductance value associated with the susceptor until the conductance value reaches a minimum value or monitoring the resistance value associated with the susceptor until the resistance value reaches a maximum value, where the conductance value at minimum conductance or the resistance value at maximum resistance is a first calibration value associated with the susceptor.

[0005] The calibration process is fast and reliable without delaying aerosol production, and further improves the flexibility and cost-effectiveness of the aerosol generating device, since the aerosol generating device may be calibrated (or recalibrated) for more than one type of susceptor at any stage in the life cycle of the aerosol generating device.

[0006] The susceptor, which is preferably a susceptor, may comprise a first material having a first Curie temperature and a second material having a second Curie temperature. The second calibration temperature of the susceptor associated with the second calibration conductance value may correspond to the second Curie temperature of the second material. The first and second 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 materials are preferably two layers or strips bonded along one of their major surfaces. The susceptor may further comprise a further layer of a third 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.

[0007] The calibration process may be performed during user operation of the aerosol generating device. Performing the calibration during user operation of the aerosol generating device means that the calibration values ​​used to control the heating process are more accurate and reliable than if the calibration process is performed at the time of manufacture. This also improves flexibility and cost efficiency in that the aerosol generating device can be calibrated for more than one type of susceptor. 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 situations, calibration at the time of manufacture is not possible.

[0008] The method may further include controlling power provided to the induction heating arrangement to maintain a conductance value associated with the susceptor between a first calibrated value and a second calibrated value.

[0009] The induction heating arrangement may include a DC / AC converter and an inductor connected to the DC / AC converter. The susceptor may be arranged to be inductively coupled to the inductor. The conductance or resistance value is preferably determined based on the DC supply voltage of the power supply and the DC current drawn from the power supply. The DC current drawn from the power supply is preferably measured at the input of the DC / AC converter. Furthermore, the DC supply voltage is preferably measured at the input of the DC / AC converter. This is due to the fact that there is a monotonic relationship between the actual conductance of the susceptor (which cannot be determined if the susceptor does not form part of the aerosol-generating article) and the apparent conductance thus determined (as the susceptor may contribute a conductance to the LCR circuit (of the DC / AC converter) to which it is coupled, since a large part of the load (R) may be due to the resistance of the susceptor. The conductance is 1 / R. References to the conductance of the susceptor are therefore understood to refer to the apparent conductance when the susceptor forms part of a separate aerosol-generating article.

[0010] Controlling the power provided to the inductive heating arrangement may include controlling the power provided to the inductive heating arrangement to incrementally increase a conductance value associated with the susceptor from a first operational conductance value to a second operational conductance value, wherein a temperature of the susceptor associated with the first operational conductance value may be sufficient for the aerosol-forming substrate to form an aerosol.

[0011] The method may further include controlling the power provided to the induction heating arrangement to maintain a resistance value associated with the susceptor between a first calibration value and a second calibration value. Controlling the power provided to the induction heating arrangement may include controlling the power provided to the induction heating arrangement to stepwise decrease a resistance value associated with the susceptor from a first operating resistance value to a second operating resistance value. A temperature of the susceptor associated with the first operating resistance value may be sufficient for the aerosol-forming substrate to form an aerosol.

[0012] Performing the calibration process may further include: v) controlling power provided to the heating arrangement to increase the temperature of the susceptor when the conductance value reaches a minimum or the resistance value reaches a maximum; vi) monitoring the conductance value or resistance value associated with the susceptor; and vii) interrupting the provision of power to the heating arrangement when the conductance value reaches a second maximum or the resistance value reaches a second minimum, where the conductance value at the second maximum is a fourth calibration value associated with the susceptor, or the resistance value at the second minimum is the fourth calibration value associated with the susceptor; and iv) monitoring the conductance value associated with the susceptor until the conductance value reaches a second minimum, where the conductance value at the second minimum is a third calibration value associated with the susceptor, or monitoring the resistance value associated with the susceptor until the resistance value reaches a second maximum, where the resistance value at the second maximum is the third calibration value associated with the susceptor.

[0013] The method may further include controlling the power provided to the induction heating arrangement to maintain a conductance value associated with the susceptor between a third calibrated value and a fourth calibrated value.

[0014] By repeating the steps of the calibration process, and using the calibrated conductance values ​​obtained during the calibration process iterations, subsequent temperature regulation is significantly improved since heat has more time to disperse into the substrate.

[0015] Controlling the power provided to the induction heating arrangement may include controlling the power to the induction heating arrangement to incrementally increase a conductance value associated with the susceptor from a first operating conductance value to a second operating conductance value.

[0016] By controlling the power provided to the induction heating arrangement, a stepwise increase in temperature of the susceptor is produced that allows for the generation of an aerosol with a substantially constant delivery (nicotine, flavor, aerosol volume, etc.) for each puff throughout the user's experience, over a sustained period encompassing the entire user's experience of several puffs, e.g., 14 puffs, or a predetermined time interval, such as 6 minutes. Specifically, the stepwise increase in temperature of the susceptor prevents reduced aerosol delivery due to substrate depletion and reduced thermal diffusion over time. Additionally, the stepwise temperature increase allows for heat to diffuse into the substrate at each step.

[0017] The method may further include controlling the power provided to the induction heating arrangement to maintain a resistance value associated with the susceptor between a third calibration value and a fourth calibration value. Controlling the power provided to the induction heating arrangement may include controlling the power provided to the induction heating arrangement to stepwise decrease the resistance value associated with the susceptor from a first operating resistance value to a second operating resistance value.

[0018] The aerosol-generating device may be configured to removably receive an aerosol-generating article. The aerosol-generating article may include a susceptor and an aerosol-forming substrate. The calibration process may be performed in response to detection of the aerosol-generating article.

[0019] The calibration process may be performed in response to detecting a user input.

[0020] The calibration process may be performed in response to detecting a control signal associated with the end of a pre-heat process. The pre-heat process may have a predetermined duration.

[0021] The method may further include performing a pre-heating process that may include i) controlling power provided to the induction heating arrangement to increase a temperature of the susceptor, ii) monitoring a conductance or resistance value associated with the susceptor, and iii) interrupting the provision of power to the induction heating arrangement when the conductance value reaches a minimum or the resistance value reaches a maximum.

[0022] The pre-heating process allows heat to diffuse into the substrate before the calibration process is initiated, thereby further improving the reliability of the calibration values.

[0023] If the conductance value reaches a minimum value or the resistance value reaches a maximum value before the end of the predetermined duration of the pre-heating process, steps i) to iii) of the pre-heating process may be repeated until the end of the predetermined duration of the pre-heating process.

[0024] The predetermined duration allows heat to diffuse into the substrate in a timely manner to reach the minimum calibration 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 reliability of the calibration process.

[0025] 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, a control signal may be generated to stop operation of the aerosol generating device.

[0026] The susceptor is preferably provided 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 behave the same as a genuine aerosol-generating article. In particular, the conductance associated with the susceptor will not reach a minimum value during a predetermined duration of the pre-heating process. This therefore prevents the use of fraudulent aerosol-generating articles.

[0027] The aerosol-generating device may be configured to receive an aerosol-generating article. The aerosol-generating article may include a susceptor and an aerosol-forming substrate. The pre-heating process may be performed in response to detection of the aerosol-generating article.

[0028] The pre-heating process may be performed in response to detecting a user input.

[0029] According to another aspect of the invention, an aerosol generating device is provided. The aerosol generating device comprises a power supply for providing a DC supply voltage and a DC current, and power electronics connected to the power supply. The power electronics includes a DC / AC converter and 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 coupleable to a susceptor. The susceptor is configured to heat an aerosol-forming substrate. The power electronics further includes a controller. The controller is configured to perform a calibration process to measure a calibration value associated with the susceptor. The power electronics is configured to inductively heat the susceptor based on the calibration value. The calibration process includes the steps of: i) controlling the power provided to the inductor 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 inductor when the conductance value reaches a maximum value or interrupting the provision of power to the inductor when the resistance value reaches a minimum value, where the conductance value at the maximum conductance value or the resistance value at the minimum resistance is a second calibration value associated with the susceptor; and iv) monitoring the conductance value associated with the susceptor until the conductance value reaches a minimum value or monitoring the resistance value associated with the susceptor until the resistance value reaches a minimum value, where the conductance value at the minimum conductance or the resistance value at the maximum resistance is a first calibration value associated with the susceptor.

[0030] A second operating temperature of the susceptor associated with the second calibrated conductance value may correspond to the Curie temperature of a material of the susceptor.

[0031] The calibration process may be performed during user operation of the aerosol generating device.

[0032] The controller may be further configured to control the power provided to the inductor to maintain a conductance value associated with the susceptor between a first calibrated value and a second calibrated value.

[0033] Controlling the power provided to the inductor can include controlling the power provided to the inductor to incrementally increase a conductance value associated with the susceptor from a first operating conductance value to a second operating conductance value, wherein a temperature of the susceptor associated with the first operating conductance value can be sufficient for the aerosol-forming substrate to form an aerosol.

[0034] The controller may be further configured to control the power provided to the induction heating arrangement to maintain a resistance value associated with the susceptor between a first calibration value and a second calibration value. Controlling the power provided to the induction heating arrangement may include controlling the power provided to the induction heating arrangement to incrementally decrease a resistance value associated with the susceptor from a first operating resistance value to a second operating resistance value, where a temperature of the susceptor associated with the first operating resistance value is sufficient for the aerosol-forming substrate to form an aerosol.

[0035] Performing the calibration process may further include: v) controlling power provided to the heating arrangement to increase the temperature of the susceptor when the conductance value reaches a minimum or the resistance value reaches a maximum; vi) monitoring a conductance value or a resistance value associated with the susceptor; and vii) interrupting the provision of power to the inductor when the conductance value reaches a second maximum or the resistance value reaches a second minimum, where the conductance value at the second maximum is a fourth calibration value associated with the susceptor, or the resistance value at the second minimum is a fourth calibration value associated with the susceptor; and vi) monitoring the conductance value associated with the susceptor until the conductance value reaches a second minimum, where the conductance value at the second minimum is a third calibration value associated with the susceptor, or monitoring the resistance value associated with the susceptor until the resistance value reaches a second maximum, where the resistance value at the second maximum is a third calibration value associated with the susceptor.

[0036] The controller may further be configured to control the power provided to the inductor to maintain a conductance value associated with the susceptor between a third calibrated conductance value and a fourth calibrated conductance value.

[0037] Controlling the power provided to the inductor may include controlling the power to the inductor to incrementally increase a conductance value associated with the susceptor from a first operating conductance value to a second operating conductance value.

[0038] The controller may be further configured to control the power provided to the induction heating arrangement to maintain a resistance value associated with the susceptor between a third calibrated value and a fourth calibrated value.

[0039] Controlling the power provided to the induction heating arrangement may include controlling the power provided to the induction heating arrangement to incrementally decrease a resistance value associated with the susceptor from a first operating resistance value to a second operating resistance value. The controller may be configured to perform a calibration process in response to detecting an aerosol-generating article including a susceptor.

[0040] The controller may be configured to perform a calibration process in response to detecting a user input.

[0041] The controller may be configured to perform the calibration process in response to detecting a control signal associated with an end of a pre-heating process, the pre-heating process having a predetermined duration.

[0042] The controller may further be configured to perform a pre-heating process that may include: i) controlling power provided to the inductor to increase a temperature of the susceptor, ii) monitoring a conductance or resistance value associated with the susceptor, and iii) discontinuing the provision of power to the inductor when the conductance value reaches a minimum or the resistance value reaches a maximum.

[0043] The controller may be configured to repeat steps i) to iii) of the preheating process until the end of the predetermined duration of the preheating process if the conductance value reaches a minimum value or the resistance value reaches a maximum value before the end of the predetermined duration of the preheating process.

[0044] The controller may be configured to generate a control signal to stop operation of the aerosol generating device if the conductance value of the susceptor 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.

[0045] The controller may be configured to implement a pre-heating process in response to detecting an aerosol-generating article that includes a susceptor.

[0046] The controller may be configured to implement the pre-heating process in response to detecting a user input.

[0047] The aerosol generating device may further comprise a housing having a cavity configured to receive the aerosol-generating article. The aerosol-generating article may include an aerosol-forming substrate and a susceptor.

[0048] According to another aspect of the present invention, there is provided an aerosol generating system comprising the aerosol generating device described above and an aerosol-generating article, the aerosol-generating article including an aerosol-forming substrate and a susceptor.

[0049] 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 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 the Curie temperature of the second susceptor material.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] As used herein, "aerosol cooling element" refers to a component of an aerosol-generating article that is disposed 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. An aerosol cooling element has a large surface area but produces a low pressure drop. Filters and other mouthpieces that produce 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.

[0056] As used herein, the term "mouthpiece" refers to the portion of an aerosol-generating article, device, or system that is placed in the mouth of a user for directly inhaling the aerosol.

[0057] The term "susceptor" as used herein refers to an element that includes a material capable of converting the energy of a magnetic field into heat. When the susceptor is placed 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.

[0058] The terms "upstream" and "forward," as well as "downstream" and "rearward," as used herein when referring to an aerosol generating device, are used to describe the relative location of components of the aerosol generating device, or of parts of components, with respect 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 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 an aerosol generating device may be described as being upstream or downstream of each other based on their relative location with respect to the airflow path of the aerosol generating device.

[0059] The terms "upstream" and "forward", as well as "downstream" and "rearward" as used herein when referring to an aerosol-generating article, are used to describe the relative location of a component or a portion of a component of the aerosol-generating article with respect to the direction in which air flows through the aerosol-generating article during its use. The aerosol-generating article according to the present invention comprises a proximal end through which 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. The components or portions of components of the aerosol-generating article may be described as being upstream or downstream of each other based on their relative location between the proximal end of the aerosol-generating article and the distal end of the aerosol-generating article. The forward of a component or a portion of a component of the aerosol-generating article is the portion that is at the end closest to the upstream end of the aerosol-generating article. The rearward of a component or a portion of a component of the aerosol-generating article is the portion that is at the end closest to the downstream end of the aerosol-generating article.

[0060] As used herein, the term "inductive coupling" refers to the heating of a susceptor when penetrated by an alternating magnetic field. The heating may be caused by the generation of eddy currents in the susceptor. The heating may also be caused by magnetic hysteresis losses.

[0061] As used herein, the term "puffing" refers to the act of a user drawing an aerosol into the body through his or her mouth or nose.

[0062] 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.

[0063] Example 1: A method for controlling aerosol generation in an aerosol generating device, the aerosol generating device including a heating arrangement and a power source for providing power to the heating arrangement, the method including performing a calibration process to measure a calibration value associated with a susceptor, the heating arrangement being configured to inductively heat the susceptor based on the calibration value, the calibration process including the steps of: i) controlling power provided to the heating arrangement to increase a temperature of the susceptor; ii) monitoring a conductance or resistance value associated with the susceptor; and iii) controlling the provision of power to the heating arrangement when the conductance value reaches a maximum value. iv) interrupting the provision of power to the heating arrangement when the resistance value reaches a minimum value, the conductance value at the maximum conductance value or the resistance value at the minimum resistance being a second calibration value associated with the susceptor; and iv) monitoring the conductance value associated with the susceptor until the conductance value reaches a minimum value or monitoring the resistance value associated with the susceptor until the resistance value reaches a maximum value, the conductance value at the minimum conductance or the resistance value at the maximum resistance being a first calibration value associated with the susceptor. Example 2: A method according to example 1, wherein the susceptor includes a first material having a first Curie temperature and a second material having a second Curie temperature, the second Curie temperature being lower than the first Curie temperature, and a second calibration temperature of the susceptor associated with the second calibration conductance value corresponds to the second Curie temperature of the second material. Example 3: A method according to example 1 or 2, wherein the calibration process is performed during user operation of the aerosol generating device. Example 4: The method according to any of Examples 1-3, further comprising controlling the power provided to the induction heating arrangement to maintain a conductance value associated with the susceptor between a first calibration value and a second calibration value. Example 5: A method according to Example 4, wherein controlling the power provided to the induction heating arrangement includes controlling the power provided to the induction heating arrangement to incrementally increase a conductance value associated with the susceptor from a first operating conductance value to a second operating conductance value, wherein a temperature of the susceptor associated with the first operating conductance value is sufficient for the aerosol-forming substrate to form an aerosol. Example 6: The method according to any of Examples 1-3, further comprising controlling the power provided to the induction heating arrangement to maintain a resistance value associated with the susceptor between a first calibration value and a second calibration value. Example 7: A method according to Example 6, wherein controlling the power provided to the induction heating arrangement includes controlling the power provided to the induction heating arrangement to incrementally decrease a resistance value associated with the susceptor from a first operating resistance value to a second operating resistance value, wherein a temperature of the susceptor associated with the first operating resistance value is sufficient for the aerosol-forming substrate to form an aerosol. Example 8: performing the calibration process further comprises: v) controlling power provided to the heating arrangement to increase the temperature of the susceptor when the conductance value reaches a minimum or the resistance value reaches a maximum; vi) monitoring a conductance or resistance value associated with the susceptor; and vii) interrupting the provision of power to the heating arrangement when the conductance value reaches a second maximum or the resistance value reaches a second minimum, wherein the conductance value at the second maximum is a fourth calibration value associated with the susceptor or the second minimum. and iv) monitoring the conductance value associated with the susceptor until the conductance value reaches a second minimum, the conductance value at the second minimum being a third calibration value associated with the susceptor, or monitoring the resistance value associated with the susceptor until the resistance value reaches a second maximum, the resistance value at the second maximum being the third calibration value associated with the susceptor. Example 9: The method according to example 8, further comprising controlling the power provided to the induction heating arrangement to maintain a conductance value associated with the susceptor between a third calibration value and a fourth calibration value. Example 10: The method according to Example 9, wherein controlling the power provided to the induction heating arrangement includes controlling the power to the induction heating arrangement to incrementally increase a conductance value associated with the susceptor from a first operating conductance value to a second operating conductance value. Example 11: The method according to example 8, further comprising controlling the power provided to the induction heating arrangement to maintain a resistance value associated with the susceptor between a third calibration value and a fourth calibration value. Example 12: The method according to Example 11, wherein controlling the power provided to the induction heating arrangement includes controlling the power provided to the induction heating arrangement to incrementally decrease a resistance value associated with the susceptor from a first operating resistance value to a second operating resistance value. Example 13: A method according to any of Examples 1 to 12, wherein the aerosol generating device is configured to removably receive an aerosol generating article, the aerosol generating article including a susceptor and an aerosol-forming substrate, and the calibration process is performed in response to detection of the aerosol generating article. Example 14: The method according to any of Examples 1 to 12, wherein the calibration process is performed in response to detecting a user input. Example 15: A method according to any of Examples 1 to 12, wherein the calibration process is performed in response to detecting a control signal associated with an end of a pre-heating process, the pre-heating process having a predetermined duration. Example 16: The method according to Example 15, further comprising performing a pre-heating process comprising: i) controlling 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; and iii) 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. Example 17: The method according to Example 16, further comprising repeating steps i) to iii) of the preheating process until the end of the predetermined duration of the preheating process if the conductance value reaches a minimum value or the resistance value reaches a maximum value before the end of the predetermined duration of the preheating process. Example 18: The method according to example 15 or 16, further comprising generating a control signal to stop 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 19: A method according to any of Examples 15-18, wherein the aerosol generating device is configured to receive an aerosol-generating article, the aerosol-generating article including a susceptor and an aerosol-forming substrate, and the pre-heating process is performed in response to detection of the aerosol-generating article. Example 20: The method according to any of Examples 15-18, wherein the pre-heating process is performed in response to detecting a user input. Example 21: 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 including a 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 coupleable to a susceptor, the susceptor being configured to heat an aerosol-forming substrate, and a controller configured to perform a calibration process to measure a calibration value associated with the susceptor, the power supply electronics being configured to inductively heat the susceptor based on the calibration value, the calibration process comprising the steps of: i) controlling power provided to the inductor to increase a temperature of the susceptor; and ii) measuring a conductance associated with the susceptor. iii) interrupting the provision of power to the inductor when the conductance value reaches a maximum value or interrupting the provision of power to the inductor when the resistance value reaches a minimum value, where the conductance value at maximum conductance or the resistance value at minimum resistance is a second calibration value associated with the susceptor; and iv) monitoring the conductance value associated with the susceptor until the conductance value reaches a minimum value or monitoring the resistance value associated with the susceptor until the resistance value reaches a maximum value, where the conductance value at minimum conductance or the resistance value at maximum resistance is a first calibration conductance value associated with the susceptor. Example 22: An aerosol generating apparatus according to Example 21, wherein the second operating temperature of the susceptor associated with the second calibrated conductance value corresponds to the Curie temperature of a material of the susceptor. Example 23: An aerosol generating device according to example 21 or 22, wherein the calibration process is performed during user operation of the aerosol generating device. Example 24: An aerosol generating device according to any of Examples 21 to 23, wherein the controller is further configured to control the power provided to the inductor to maintain a conductance value associated with the susceptor between a first calibration value and a second calibration value. Example 25: An aerosol generating apparatus according to Example 24, wherein controlling the power provided to the inductor includes controlling the power provided to the inductor to incrementally increase a conductance value associated with the susceptor from a first operating conductance value to a second operating conductance value, and a temperature of the susceptor associated with the first operating conductance value is sufficient for the aerosol-forming substrate to form an aerosol. Example 26: An aerosol generating device according to any of Examples 21 to 23, wherein the controller is further configured to control the power provided to the induction heating arrangement to maintain a resistance value associated with the susceptor between a first calibration value and a second calibration value. Example 27: An aerosol generating apparatus according to Example 26, wherein controlling the power provided to the induction heating arrangement includes controlling the power provided to the induction heating arrangement to gradually decrease a resistance value associated with the susceptor from a first operating resistance value to a second operating resistance value, wherein a temperature of the susceptor associated with the first operating resistance value is sufficient for the aerosol-forming substrate to form an aerosol. Example 28: performing the calibration process further comprises: v) controlling power provided to the heating arrangement to increase the temperature of the susceptor when the conductance value reaches a minimum or the resistance value reaches a maximum; vi) monitoring a conductance value or a resistance value associated with the susceptor; and vii) interrupting the provision of power to the inductor when the conductance value reaches a second maximum or the resistance value reaches a second minimum, wherein the conductance value at the second maximum is a fourth calibration value associated with the susceptor or the resistance value at the second minimum is a fourth calibration value associated with the susceptor. 24. The aerosol generating apparatus according to any of claims 21 to 23, comprising: (i) interrupting the monitoring until the resistance value associated with the susceptor reaches a fourth calibration value associated with the susceptor; and (ii) monitoring the conductance value associated with the susceptor until the conductance value reaches a second minimum value, the conductance value at the second minimum value being a third calibration value associated with the susceptor; or (iii) monitoring the resistance value associated with the susceptor until the resistance value reaches a second maximum value, the resistance value at the second maximum value being the third calibration value associated with the susceptor. Example 29: An aerosol generating device according to Example 28, wherein the controller is further configured to control the power provided to the inductor to maintain a conductance value associated with the susceptor between a third calibration value and a fourth calibration value. Example 30: An aerosol generating device according to Example 29, wherein controlling the power provided to the inductor includes controlling the power to the inductor to incrementally increase a conductance value associated with the susceptor from a first operating conductance value to a second operating conductance value. Example 31: The aerosol generating device according to Example 28, further configured to control the power provided to the induction heating arrangement to maintain a resistance value associated with the susceptor between a third calibration value and a fourth calibration value. Example 32: An aerosol generating device according to Example 29, wherein controlling the power provided to the induction heating arrangement includes controlling the power provided to the induction heating arrangement to gradually decrease a resistance value associated with the susceptor from a first operating resistance value to a second operating resistance value. Example 33: An aerosol generating device according to any of Examples 21 to 32, wherein the controller is configured to perform a calibration process in response to detection of an aerosol-generating article including a susceptor. Example 34: An aerosol generating device according to any of Examples 21 to 32, wherein the controller is configured to perform a calibration process in response to detecting a user input. Example 35: An aerosol generating device according to any of Examples 21 to 32, wherein the controller is configured to perform a calibration process in response to detecting a control signal associated with the end of a pre-heating process, the pre-heating process having a predetermined duration. Example 36: The aerosol generating apparatus according to Example 35, wherein the controller is further configured to perform a pre-heating process, the pre-heating process including the steps of: i) controlling the power provided to the inductor to increase the temperature of the susceptor; ii) monitoring a conductance or resistance value associated with the susceptor; and iii) interrupting the provision of power to the inductor when the conductance value reaches a minimum value or the resistance value reaches a maximum value. Example 37: An aerosol generating device according to Example 36, wherein the controller is configured to repeat steps i) to iii) of the pre-heating process until the end of the predetermined duration of the pre-heating process if the conductance value reaches a minimum value or the resistance value reaches a maximum value before the end of the predetermined duration of the pre-heating process. Example 38: An aerosol generating device according to example 36 or 37, wherein the controller is configured to generate a control signal for stopping operation of the aerosol generating device if the conductance value of the susceptor 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 39: An aerosol generating apparatus according to any of Examples 35 to 38, wherein the controller is configured to perform a pre-heating process in response to detection of an aerosol-generating article including a susceptor. Example 40: An aerosol generating device according to any of Examples 35 to 39, wherein the controller is configured to perform a pre-heating process in response to detecting a user input. Example 41: An aerosol generating device according to any of Examples 21 to 40, further comprising a housing having a cavity configured to receive an aerosol-generating article, the aerosol-generating article including an aerosol-forming substrate and a susceptor. Example 42: An aerosol-generating system comprising the aerosol-generating device according to any one of claims 21 to 41 and an aerosol-generating article, the aerosol-generating article including an aerosol-forming substrate and a susceptor. Example 43: The aerosol generating system according to Example 42, wherein the susceptor comprises a first susceptor material and a second susceptor material, the first susceptor material being disposed in physical contact with the second susceptor material. Example 44: An aerosol generating system according to Example 42 or 43, 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 45: An aerosol generating system according to Example 44, wherein the second calibration temperature corresponds to the Curie temperature of a second susceptor material.

[0064] The embodiments will now be further described with reference to the figures. [Brief description of the drawings]

[0065] [Figure 1] FIG. 1 shows a schematic cross-sectional view of an aerosol-generating article. [Diagram 2] Figure 2A shows a schematic cross-sectional view of an aerosol generating device for use with the aerosol-generating article shown in Figure 1. Figure 2B shows a schematic cross-sectional view of an aerosol generating device engaged with the aerosol-generating article shown in Figure 1. [Diagram 3] FIG. 3 is a block diagram showing an induction heating device of 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 the 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

[0066] 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 these four elements is a substantially cylindrical element, each having substantially the same diameter. These four elements are arranged consecutively and surrounded by an outer wrapper 150 to form a cylindrical rod. An elongated susceptor 160 is disposed within and in contact with the aerosol-forming substrate 110. The susceptor 160 has a length approximately equal to the length of the aerosol-forming substrate 110 and is disposed along the radial central axis of the aerosol-forming substrate 110.

[0067] 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 the strip of the first susceptor material. The susceptor may be formed by cladding a strip of a second susceptor material onto a strip of a first susceptor material.

[0068] The aerosol-generating article 100 has a proximal or oral end 170 that a user inserts into their mouth during use, and a distal end 180 that is disposed at the opposite end of the aerosol-generating article 100 to the oral end 170. When assembled, the aerosol-generating article 100 preferably has a total length of about 45 mm and a diameter of about 7.2 mm.

[0069] 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 that are disposed between the oral end 170 and the distal end 180 may be described as being upstream of the oral end 170 or may be described as being downstream of the distal end 180. The aerosol-forming substrate 110 is disposed at the distal or upstream end 180 of the aerosol-generating article 100.

[0070] The support element 120 is positioned immediately downstream from and against 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.

[0071] The aerosol cooling element 130 is positioned immediately downstream from and abutting 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.

[0072] Mouthpiece 140 is positioned immediately downstream from and in abutment with aerosol cooling element 130. Mouthpiece 140 includes a conventional cellulose acetate tow filter with low filtration efficiency.

[0073] 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.

[0074] 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, for generating an aerosol. The aerosol-generating device 200 comprises a housing 210 having a cavity 220 configured to receive the aerosol-generating article 100. The aerosol-generating device 200 further comprises 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.

[0075] The induction heating device 230 is shown as a block diagram in Figure 3. The induction heating device 230 includes 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.

[0076] 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.

[0077] The DC / AC converter 340 is configured to supply a high frequency alternating current to the inductor 240. 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).

[0078] 4 shows a schematic of the electronic components of the induction heating device 230, in particular the DC / AC converter 340. The DC / AC converter 340 may include a class E power amplifier. The class E power amplifier includes a transformer switch 410 including a field effect transistor 420, for example 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 including a shunt capacitor C1 and a series connection of a capacitor C2 and an inductor L2 corresponding to the inductor 240. Furthermore, a DC power supply 310 including a choke L1 supplies a DC supply voltage V DC is shown to supply a DC current I DC is drawn from the DC power supply 310 during operation. The ohmic resistance R of the inductor L2 coil and the ohmic resistance R of the susceptor 160 load 5. An ohmic resistance R, which represents a total ohmic load 450, which is the sum of

[0079] Although DC / AC converter 340 is shown as including a class E power amplifier, it should be appreciated that DC / AC converter 340 may use any suitable circuitry 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 with four switching transistors acting in pairs.

[0080] Returning to Figure 3, the inductor 240 may receive the AC current from the DC / AC converter 340 through a matching network 350 to optimally match the load, but the matching network 350 is not required. The matching network 350 may include a small matching transformer. The matching network 350 may improve the power transfer efficiency between the DC / AC converter 340 and the inductor 240.

[0081] As shown in FIG. 2A, the inductor 240 is disposed adjacent the distal portion 225 of the cavity 220 of the aerosol generating device 200. Thus, a high frequency alternating current supplied to the inductor 240 during operation of the aerosol generating device 200 causes the inductor 240 to generate a high frequency alternating magnetic field within the distal portion 225 of the aerosol generating device 200. The alternating magnetic field preferably has a frequency of 1-30 megahertz, preferably 2-10 megahertz, for example 5-7 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 disposed adjacent the inductor 240 such that the susceptor 160 of the aerosol generating article 100 is disposed within this alternating magnetic field. When the alternating magnetic field penetrates the susceptor 160, the alternating magnetic field heats the susceptor 160. For example, eddy currents are generated within the susceptor 160, which is consequently 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.

[0082] The controller 330 may be a microcontroller, preferably a programmable microcontroller, that is programmed to regulate the supply of power from the DC power supply 310 to the induction heating arrangement 320 to control the temperature of the susceptor 160.

[0083] 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 dotted 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. As the susceptor 160 is inductively heated, the apparent resistance of the susceptor 160 increases. This increase in resistance is due to the DC current I drawn from the power supply 310, which at a constant voltage decreases as the temperature of the susceptor 160 increases. DC The high frequency alternating magnetic field provided by the inductor 240 induces eddy currents in the vicinity of the susceptor surface, an effect known as the skin effect. The resistance of the susceptor 160 depends in part on the electrical resistance of the first susceptor material and the resistance of the second susceptor material, which in turn depends in part on the depth of the skin layer in each material available for the induced eddy currents, which in turn depends on the temperature. When the second susceptor material reaches its Curie temperature, it loses its magnetism. This increases the skin layer 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, the detected DC current I DCincreases momentarily and the resistance begins to drop. This can be 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 spontaneous magnetism. This point is called the Curie temperature and can be seen as a peak (local maximum) in FIG. 6. At this point, the second susceptor material undergoes 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 inherently material specific temperature). After the Curie temperature is reached, if the inductor 240 continues to generate the alternating magnetic field (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 Joule heating within the susceptor 160 to continue, causing the resistance to increase again (which for most metallic susceptor materials can have a polynomial dependence on temperature that 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 provide power to the susceptor 160.

[0084] Thus, as can be seen from FIG. 6, the current I drawn from the susceptor 160 (and correspondingly the current I drawn from the power supply 310) DC The apparent resistance of the susceptor 160 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), since each determined value of apparent resistance represents only a single value of temperature, and there is no ambiguity in the relationship. The monotonic relationship between the temperature and apparent resistance of the susceptor 160 allows for the determination and control of the temperature of the susceptor 160, and thus the temperature of the aerosol-forming substrate 110. The apparent resistance of the susceptor 160 varies with at least the DC current I drawn from the DC power supply 310. DC This can be detected remotely by monitoring

[0085] At least the DC current I drawn from the power supply 310 DCis monitored by the controller 330. Preferably, the DC current drawn from the power supply 310, I DC and DC supply voltage V DC The controller 330 adjusts the supply of power provided to the heating arrangement 320 based on the conductance or resistance value, where the conductance is a function of the DC current I DC and DC supply voltage V DC is defined as the ratio of the DC supply voltage V DC and DC current I D The heating arrangement 320 is defined as the ratio of DC current I DC Optionally, the heating arrangement may include a current sensor (not shown) for measuring a DC supply voltage V DC The current sensor and the voltage sensor are disposed on the input side of the DC / AC converter 340. The DC current I 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.

[0086] 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.

[0087] 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 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 (peak of the current plot in FIG. 6). The first calibration temperature is equal to or greater than the temperature of the susceptor at which the skin depth of the second susceptor material begins to increase (leading to a temporary drop in resistance). Thus, the first calibration temperature is equal to or greater than the temperature at maximum penetration rate 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.

[0088] Conductance (resistance) has a polynomial dependence on temperature, and 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 ​​through 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 is given by: G Target =G Lower +(x×△G) where ΔG is the difference between the first conductance value and the second conductance value, and x is a percentage of ΔG.

[0089] The controller 330 may control the provision of power 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 may continuously generate an alternating current that heats the susceptor 160 and simultaneously generate a DC supply voltage V DC and DC current I DC may be measured every millisecond, preferably for a period of 100 milliseconds. If conductance is monitored by the controller 330, the duty cycle of the switching transistor 410 is decreased 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 decreased 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 decreased to about 9%. In other words, the switching transistor 410 may be switched into a mode in which it pulses only every 10 milliseconds for a duration of 1 millisecond. During this 1 millisecond on-state (conducting state) of the switching transistor 410, the DC supply voltage V DC and the DC current I DC The value of is measured to determine the conductance, and when the conductance decreases (or the resistance increases), indicating that the temperature of the susceptor 160 is below the target operating temperature, a pulse train is again applied to the gate of transistor 410 at the drive frequency selected for the system.

[0090] Power may be supplied by the controller 330 to the inductor 240 in the form of a series of successive pulses of current. Specifically, power may be supplied to the inductor 240 in a series of pulses, each separated by a fixed time interval. The series of successive pulses may include two or more heating pulses and one or more probe pulses between successive heating pulses. The heating pulses have an intensity for heating the susceptor 160. The probe pulses are instead separate power pulses having an intensity for obtaining feedback on the conductance or resistance value and then on the release (decrease) of 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 by the DC power supply to the inductor 240. 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 by the DC power supply to the inductor 240.

[0091] The controller 330 is programmed to perform a calibration process to obtain a calibration value where the conductance is measured at a known temperature of the susceptor 160. The known temperature of the susceptor may be a first calibration temperature that corresponds to the first calibration value, and the second calibration temperature that corresponds to the second calibration value. The calibration process is preferably performed each time a user operates the aerosol generating device 200, e.g., each time a user inserts an aerosol-generating article 100 into the aerosol generating device 200.

[0092] 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 optionally, the supply voltage V DCThe 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 and the current begins to increase. 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 a first calibration value. The controller may record the value of the conductance or resistance at a predetermined time after the minimum current is reached as the first calibration value. The conductance or resistance is proportional to the measured current I. DC and the measured voltage V DC Alternatively, the power 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.

[0093] As the controller 330 continues to control the power provided by the DC / AC converter 340 to the inductor 240, the measured current rises until a second turning point is reached, after which a maximum current is observed (corresponding to the Curie temperature of the second susceptor material), 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 provision of power to the inductor 240, resulting in a decrease in the temperature of the susceptor 160, and a corresponding decrease in conductance.

[0094] Due to the shape of the graph, this process of continuously heating the susceptor 160 to obtain the first and second calibration values ​​can be repeated at least once. After interrupting the provision of power 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 provide 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 just after the third turning point as the first calibration value, and the conductance or resistance value at the current of the fourth turning point as the second calibration value. The repetition of the measurement of the turning points corresponding to the minimum and maximum currents measured significantly improves subsequent temperature regulation during user operation 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 it may take more time for heat to dissipate into the aerosol-forming substrate 110 and the susceptor 160.

[0095] To further improve the robustness of the calibration process, the controller 310 may optionally be 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 a similar condition, the calibration may be performed before heat is diffused into the aerosol-forming substrate 110, reducing the reliability of the calibration value. If the aerosol-forming substrate 110 is wet, the susceptor 160 takes longer to reach the valley temperature (due to the moisture content of the substrate 110).

[0096] To perform the preheating process, the controller 330 is configured to continuously supply power to the inductor 240. As described above, the current starts to decrease with increasing temperature of the susceptor 160 until a minimum value is reached. At this stage, the controller 330 is configured to wait for 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 provide power until a minimum value is reached. At the minimum value, the controller controls the DC / AC converter 340 to again interrupt the supply of power to the inductor 240. The controller 330 again waits for the same predetermined period of 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 duration of the preheating process. The predetermined duration of the preheating process is preferably 11 seconds. The duration of the pre-heating process for a given combination is followed by a calibration process, preferably of 20 seconds.

[0097] If the aerosol-forming substrate 110 is dry, the first minimum of the pre-heating process may be reached within the predetermined period, and the interruption of power may be repeated until the end of the predetermined period. If the aerosol-forming substrate 110 is wet, the first minimum of the pre-heating process may be reached towards the end of the predetermined period. Thus, by carrying out the pre-heating process for a predetermined duration, it is ensured that, regardless of the physical state of the substrate 110, the substrate 110 has enough time to reach a minimum temperature and a first maximum in order to be ready to supply continuous power. This allows for calibration as early as possible, but still without the risk that the substrate 110 will not reach the valley beforehand.

[0098] Furthermore, the aerosol-generating article 100 may be configured to always reach the minimum value 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 in 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.

[0099] The pre-heating process may be performed in response to receiving a user input, for example, a user activation of the aerosol generating device 200. Additionally or alternatively, the controller 330 may be configured to detect the presence of an aerosol-generating article 100 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.

[0100] 7 is a graph of conductance versus time illustrating a heating profile of the susceptor 160. The graph shows two successive heating stages, a first heating stage 710 including a pre-heating process 710A and a calibration process 710B as described above, and a second heating stage 720 corresponding 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 will 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.

[0101] 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 or resistance values ​​associated with the susceptor, it will be appreciated that the above-described techniques may be implemented based on values ​​of current measured at the input of the DC / AC converter 340.

[0102] 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 minimum temperature at which the aerosol-forming substrate can form an aerosol in a volume and amount sufficient for a satisfactory experience when inhaled by a user. The second operating temperature of the susceptor is the maximum temperature at which it is desired 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 about 150 degrees Celsius and about 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 C. 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.

[0103] It will be appreciated that the temperature steps shown in FIG. 7 are exemplary and the second heating stage 720 comprises at least three consecutive temperature steps, preferably two to fourteen temperature steps, most preferably three to eight temperature steps. Each temperature step may have a predefined 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 and 200 seconds, more preferably between 40 and 160 seconds. The duration of each temperature step may correspond to a predefined number of user puffs. Preferably, the first temperature step corresponds to four user puffs and each subsequent temperature step corresponds to one user puff.

[0104] During the duration of each temperature step, the temperature of the susceptor 160 is maintained at the target operating temperature corresponding to the respective temperature step. Thus, during the duration of each temperature step, the controller 330 controls the provision of power to the heating arrangement 320 such that the conductance is maintained at a value corresponding to the target operating temperature of the respective temperature step mentioned above. The target conductance value for each temperature step may be stored in the memory of the controller 330.

[0105] As an example, the second heating stage 720 may include five temperature steps, the first temperature step having a duration of 160 seconds and a G Target =G Lower +(0.09×△G), the second temperature step has a duration of 40 seconds, and G Target =G Lower +(0.25×△G), the third temperature step has a duration of 40 seconds, and G Target =G Lower +(0.4×△G), the fourth temperature step has a duration of 40 seconds, and G Target =G Lower +(0.56×△G), the fifth temperature step has a duration 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.

[0106] 8 is a flow diagram of a method 800 for controlling aerosol generation in the aerosol generating device 200. As described above, the controller 330 can be programmed to implement the method 800.

[0107] 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 user activation of the aerosol generating device 200. Additionally or alternatively, detecting user operation of the aerosol generating device 200 may include detecting insertion of an aerosol-generating article 100 into the aerosol generating device 200.

[0108] In response to detecting user action at step 810, controller 330 may be configured to perform the optional pre-heating process described above. At the end of the predetermined duration of the pre-heating process, controller 330 performs the 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.

[0109] 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 cases as modified by the term "about." Also, all ranges include the maximum and minimum points disclosed, and include any intermediate ranges therein, which may or may not be specifically recited herein. Within this context, the number A may be considered to include a numerical value that is within the general standard error for the measurement of the property that the number A modifies. The number A may deviate by the percentages recited above, in some cases as used in the appended claims, provided that the amount by which A deviates does not materially affect the basic and novel property(ies) of the claimed invention. Also, all ranges include the maximum and minimum points disclosed, and include any intermediate ranges therein, which may or may not be specifically recited herein.

Claims

1. 1. A method for controlling aerosol generation in an aerosol generating device, the aerosol generating device comprising a heating arrangement and a power source for providing power to the heating arrangement, the method comprising: performing a calibration process to measure a calibration value associated with a susceptor, the heating arrangement being configured to inductively heat the susceptor based on the calibration value, the calibration process comprising: i) controlling the power provided to the 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 heating arrangement when the conductance value reaches a maximum value or interrupting the provision of power to the heating arrangement when the resistance value reaches a minimum value, the conductance value at maximum conductance or the resistance value at minimum resistance being a second calibration value associated with the susceptor; iv) monitoring the conductance value associated with the susceptor until the conductance value reaches a minimum value or monitoring the resistance value associated with the susceptor until the resistance value reaches a maximum value, wherein the conductance value at minimum conductance or the resistance value at maximum resistance is a first calibration value associated with the susceptor; A method, wherein the calibration process is performed in response to detecting a control signal associated with an end of a pre-heat process, the pre-heat process having a predetermined duration.

2. 2. The method of claim 1, wherein the susceptor comprises a first material having a first Curie temperature and a second material having a second Curie temperature, the second Curie temperature being lower than the first Curie temperature, and a second calibration temperature of the susceptor associated with the second calibration conductance value corresponds to the second Curie temperature of the second material.

3. The method of claim 1 or 2, wherein the calibration process is performed during user operation of the aerosol generating device.

4. controlling power provided to the induction heating arrangement to maintain the conductance value associated with the susceptor between the first calibration value and the second calibration value; 4. The method of claim 1, wherein controlling the power provided to the induction heating arrangement comprises controlling the power provided to the induction heating arrangement to increase the conductance value associated with the susceptor stepwise from a first operating conductance value to a second operating conductance value, wherein a temperature of the susceptor associated with the first operating conductance value is sufficient for the aerosol-forming substrate to form an aerosol.

5. controlling the power provided to the induction heating arrangement to maintain the resistance value associated with the susceptor between the first calibration value and the second calibration value; 4. The method of claim 1, wherein controlling the power provided to the induction heating arrangement comprises controlling the power provided to the induction heating arrangement to stepwise decrease the resistance value associated with the susceptor from a first operating resistance value to a second operating resistance value, wherein a temperature of the susceptor associated with the first operating resistance value is sufficient for the aerosol-forming substrate to form an aerosol.

6. 2. The method of claim 1, further comprising performing the pre-heating process, the pre-heating process comprising: 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; and iii) 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.

7. 7. The method of claim 6, further comprising repeating steps i) through iii) of the pre-heat process until the end of the predetermined duration of the pre-heat process if the conductance value reaches a minimum value or the resistance value reaches a maximum value before the end of the predetermined duration of the pre-heat process.

8. The method of any one of claims 1 to 6, further comprising generating a control signal to stop 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 the predetermined duration of the pre-heating process.

9. 9. The method of claim 1, wherein the aerosol-generating device is configured to receive the aerosol-generating article, the aerosol-generating article comprising the susceptor and the aerosol-forming substrate, and the pre-heating process is performed in response to detection of the aerosol-generating article.

10. An aerosol generating device, comprising: a power supply for providing a DC supply voltage and a DC current; a power supply electronic circuit connected to the power supply, the power supply electronic circuit comprising a 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 and a controller configured to perform a calibration process to measure a calibration value associated with a susceptor, the power electronics being configured to inductively heat the susceptor based on the calibration value, the calibration process comprising: i) controlling the power provided to the inductor to increase the temperature of the susceptor; ii) monitoring a conductance or resistance value associated with the susceptor; iii) interrupting the supply of power to the inductor when the conductance value reaches a maximum value or interrupting the supply of power to the inductor when the resistance value reaches a minimum value, the conductance value at maximum conductance or the resistance value at minimum resistance being a second calibration value associated with the susceptor; iv) monitoring the conductance value associated with the susceptor until the conductance value reaches a minimum value or monitoring the resistance value associated with the susceptor until the resistance value reaches a maximum value, wherein the conductance value at minimum conductance or the resistance value at maximum resistance is a first calibrated conductance value associated with the susceptor; An aerosol generating device, wherein the controller is configured to perform the calibration process in response to detecting a control signal associated with the end of a pre-heating process, the pre-heating process having a predetermined duration.

11. 11. The aerosol generating device of claim 10, wherein a second operating temperature of the susceptor associated with the second calibrated conductance value corresponds to a Curie temperature of a material of the susceptor.

12. 12. The aerosol generating device of claim 10 or 11, wherein the controller is further configured to control the power provided to the inductor to maintain the conductance value associated with the susceptor between the first calibration value and the second calibration value.

13. 12. The aerosol generating device of claim 10 or 11, wherein the controller is further configured to control the power provided to the induction heating arrangement to maintain the resistance value associated with the susceptor between the first calibration value and the second calibration value.

14. Performing the calibration process further comprises: v) controlling power provided to the heating arrangement to increase the temperature of the susceptor when the conductance value reaches the minimum value or the resistance value reaches the maximum value; vi) monitoring the conductance value or the resistance value associated with the susceptor; and vii) interrupting the provision of power to the inductor when the conductance value reaches a second maximum value or the resistance value reaches a second minimum value, wherein the conductance value at the second maximum value is a fourth calibration value associated with the susceptor or the resistance value at the second minimum value is a fourth calibration value associated with the susceptor.

12. The aerosol generating device of claim 10, further comprising: iv) monitoring the conductance value associated with the susceptor until the conductance value reaches a second minimum, the conductance value at the second minimum being a third calibration value associated with the susceptor; or iv) monitoring the resistance value associated with the susceptor until the resistance value reaches a second maximum, the resistance value at the second maximum being the third calibration value associated with the susceptor.

15. 15. The aerosol generating device of claim 14, wherein the controller is further configured to control the power provided to the inductor to maintain the conductance value associated with the susceptor between the third calibration value and the fourth calibration value.

16. 15. The aerosol generating device of claim 14, wherein the controller is further configured to control power provided to the induction heating arrangement to maintain a resistance value associated with the susceptor between the third calibration value and the fourth calibration value.

17. the controller is configured to perform the calibration process in response to detecting an aerosol-generating article that includes the susceptor; or An aerosol generating device according to any one of claims 10 to 16, wherein the controller is configured to perform the calibration process in response to detecting a user input.

18. 11. The aerosol generating device of claim 10, wherein the controller is further configured to perform the pre-heating process, the pre-heating process comprising: i) controlling the power provided to the inductor to increase the temperature of the susceptor; ii) monitoring a conductance or resistance value associated with the susceptor; and iii) interrupting the provision of power to the inductor when the conductance value reaches a minimum value or the resistance value reaches a maximum value.

19. the controller is configured to repeat steps i) to iii) of the pre-heating process until the end of the predetermined duration of the pre-heating process if the conductance value reaches a minimum value or the resistance value reaches a maximum value before the end of the predetermined duration of the pre-heating process; 19. The aerosol generating device of claim 18, wherein the controller is configured to generate a control signal to stop operation of the aerosol generating device if the conductance value of the susceptor does not reach a minimum value or the resistance value does not reach a maximum value during the predetermined duration of the pre-heating process.

20. An aerosol generating system comprising the aerosol generating device according to any one of claims 10 to 19 and an aerosol generating article, the aerosol generating article including the aerosol-forming substrate and the susceptor.

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