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

Abstract

An aerosol generating apparatus method is provided for controlling aerosol generation in an aerosol generating apparatus, the apparatus comprising an inductive heating arrangement and a power source for providing power to the inductive heating arrangement. During a first user operation mode, a calibration process is performed including measuring a safety parameter associated with a susceptor inductively coupled to the inductive heating arrangement to obtain a first safety parameter value, the susceptor being configured to heat an aerosol-forming substrate, the calibration process including a heating phase from a first calibration temperature of the susceptor to a second calibration temperature, the safety parameter being a duration of the heating phase. During a second user operation mode, the power provided to the inductive heating arrangement is controlled such that the temperature of the susceptor is adjusted based at least in part on the measured safety parameter.

Description

[Technical field]

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

[0002] The aerosol generating device may comprise an electrically operated heat source configured to heat the aerosol-forming substrate to generate the aerosol. It is important for the aerosol generating device to accurately monitor and control the temperature of the electrically operated heat source to ensure optimal generation and delivery of the aerosol to the user. It is important to ensure that the electrically operated heat source does not overheat the aerosol-forming substrate, as overheating can result in the generation of undesirable compounds as well as unpleasant tastes and aromas for the user.

[0003] It is desirable to provide temperature monitoring and control of the induction heating device that provides reliable temperature regulation incorporating detection of overheating in order to efficiently implement safety mechanisms and ensure continued normal operation of the aerosol generating device. Summary of the Invention

[0004] According to an embodiment of the present invention, there is provided a method for controlling aerosol generation in an aerosol generating device. The device comprises an inductive heating arrangement and a power source for providing power to the inductive heating arrangement. The method includes performing a calibration process during a first user operation mode of the aerosol generating device to generate an aerosol, the calibration process including measuring a safety parameter associated with a susceptor inductively coupled to the inductive heating arrangement to obtain a first safety parameter value, the susceptor being configured to heat an aerosol-forming substrate, the calibration process including a heating phase from a first calibration temperature of the susceptor to a second calibration temperature, the safety parameter being a duration of the heating phase. The method further includes controlling power provided to the inductive heating arrangement such that during a second user operation mode of the aerosol generating device to generate an aerosol, the temperature of the susceptor is adjusted based at least in part on the measured safety parameter.

[0005] Measuring safety parameter values ​​during the calibration process provides a way to incorporate safety mechanisms to prevent overheating into the operation of the aerosol generating device without affecting the user experience.

[0006] The method may further include performing one or more further calibration processes. The one or more further calibration processes include re-measuring a safety parameter associated with the susceptor. Controlling the power provided to the induction heating arrangement such that the temperature of the susceptor is adjusted based at least in part on the measured safety parameter may include determining whether a value of the safety parameter re-measured during each further calibration process is greater than a threshold value, the threshold value being based at least in part on the first safety parameter value, and entering a safe operating mode of the aerosol generating device if the value of the safety parameter re-measured during each further calibration process is greater than the threshold value. The threshold value may be at least twice the first safety parameter value.

[0007] The method may further include performing one or more further calibration processes including re-measuring a safety parameter associated with the susceptor. Controlling the power provided to the induction heating arrangement such that the temperature of the susceptor is adjusted based at least in part on the measured safety parameter may further include determining whether a value of the safety parameter re-measured during each further calibration process is greater than a threshold value, the threshold value being based at least in part on a value of the safety parameter measured during a last calibration process prior to the respective calibration process, and entering a safe operating mode of the aerosol generating device if the value of the safety parameter re-measured during each further calibration process is greater than the threshold value. The threshold value may be at least twice the value of the safety parameter measured during a last calibration process prior to the respective calibration process.

[0008] Repeating the calibration process during operation of the device, including re-measuring the safety parameter, provides enhanced safety control throughout user operation of the device to generate an aerosol. In addition, comparing the re-measured safety parameter value to a threshold value (which is a multiple of the previously measured safety parameter value) provides a more accurate determination of whether overheating may occur.

[0009] One or more of the further calibration processes may be performed at predetermined time intervals, each of which may be between 20 seconds and 50 seconds.

[0010] The method may further include monitoring one of a current value associated with the susceptor, a conductance value associated with the susceptor, and a resistance value associated with the susceptor, and a further calibration process may be performed in response to detecting a change in the monitored current value, conductance value, or resistance value that is greater than a threshold change value.

[0011] Repeating the calibration process, which involves re-measuring the safety parameters when the apparent current, resistance, or conductance of the susceptor appears unstable, means that malfunctions can be detected early, thereby further enhancing the effectiveness of the safety mechanisms.

[0012] Controlling the power provided to the induction heating arrangement to regulate the temperature of the susceptor based at least in part on the measured safety parameter may include comparing a first safety parameter value to a predetermined value associated with the susceptor and entering a safe operating mode or a second user operating mode based on a result of the comparison. Entering the safe operating mode or entering a second user operating mode based on a result of the comparison may include entering the safe operating mode if the first safety parameter value is greater than the predetermined value and entering the second user operating mode if the first safety parameter value is less than the predetermined value.

[0013] This allows malfunctions leading to overheating to be detected as early as possible and ensures the accuracy of the first measured safety parameter value.

[0014] Entering the safe operating mode may include reducing power provided to the induction heating arrangement. Entering the safe operating mode may include ceasing to provide power to the induction heating arrangement. Entering the safe operating mode may include automatically turning off the aerosol generating device. Entering the safe operating mode may include generating a signal to alert a user that an error condition has occurred.

[0015] The susceptor may include a first susceptor material having a first Curie temperature and a second susceptor material having a second Curie temperature, the second Curie temperature being lower than the first Curie temperature, and the second calibration temperature corresponding to the second Curie temperature of the second susceptor material. The first susceptor material may be an iron metal and the second susceptor material may include nickel.

[0016] The method may further include maintaining a temperature of the susceptor between the first calibrated temperature and the second calibrated temperature during a second user operation mode of the aerosol generating device to generate the aerosol.

[0017] Maintaining the temperature of the susceptor between the first and second calibrated temperatures allows for more precise temperature control, thereby improving the user experience.

[0018] Performing the calibration process may further include measuring a first calibration value corresponding to the first calibration temperature and a second calibration value corresponding to the second calibration temperature, where the first calibration value and the second calibration value are current values, resistance values ​​or conductance values, and controlling the power provided to the induction heating arrangement includes adjusting a temperature of the susceptor based at least in part on the first calibration value and the second calibration value.

[0019] Controlling the power and therefore the susceptor temperature based on the first and second calibration values ​​provides an efficient method for accurate temperature control.

[0020] According to an embodiment of the present invention, there is provided an aerosol generating apparatus comprising 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 is coupleable to a susceptor, the susceptor being configured to heat an aerosol-forming substrate. The aerosol generating device further comprises a controller configured to perform a calibration process including measuring a safety parameter associated with a susceptor inductively coupled to the induction heating arrangement to obtain a first safety parameter value during a first user operation mode of the aerosol generating device for generating an aerosol, the susceptor being configured to heat the aerosol-forming substrate, the calibration process including a heating phase from a first calibration temperature of the susceptor to a second calibration temperature, the safety parameter being a duration of the heating phase, and to control power provided to the induction heating arrangement such that a temperature of the susceptor is adjusted based at least in part on the measured safety parameter during a second user operation mode of the aerosol generating device for generating an aerosol.

[0021] The controller may be further configured to perform one or more further calibration processes, the one or more further calibration processes including re-measuring a safety parameter associated with the susceptor. Controlling the power provided to the induction heating arrangement such that the temperature of the susceptor is adjusted based at least in part on the measured safety parameter includes determining whether a value of the safety parameter re-measured during each further calibration process is greater than a threshold value, the threshold value being based at least in part on the first safety parameter value, and if the value of the safety parameter re-measured during each further calibration process is greater than the threshold value, the controller is configured to enter a safe operating mode of the aerosol generating device. The threshold value may be at least twice the first safety parameter value.

[0022] The controller may be further configured to perform one or more further calibration processes, including re-measuring a safety parameter associated with the susceptor. Controlling the power provided to the induction heating arrangement such that the temperature of the susceptor is adjusted based at least in part on the measured safety parameter may include determining whether a value of the safety parameter re-measured during each further calibration process is greater than a threshold value, the threshold value being based at least in part on a value of the safety parameter measured during a last calibration process prior to the respective calibration process, and if the value of the safety parameter re-measured during each further calibration process is greater than the threshold value, the controller is configured to enter a safe operating mode of the aerosol generating device. The threshold value may be at least twice the value of the safety parameter measured during a last calibration process prior to the respective calibration process.

[0023] The controller may be configured to perform one or more further calibration processes at predetermined time intervals, each of which may be between 20 seconds and 50 seconds.

[0024] The controller may be further configured to monitor one of a current value associated with the susceptor, a conductance value associated with the susceptor, and a resistance value associated with the susceptor, and the controller is configured to perform a further calibration process in response to detecting a change in the monitored value of the monitored current value, conductance value, or resistance value that is greater than a threshold change value.

[0025] Controlling the power provided to the induction heating arrangement to adjust the temperature of the susceptor based at least in part on the measured safety parameter may include comparing the first safety parameter value to a predetermined value associated with the susceptor, and the controller is configured to enter a safe operating mode or a second user operating mode based on a result of the comparison. Entering the safe operating mode or entering the second user operating mode based on a result of the comparison may include entering the safe operating mode if the first safety parameter value is greater than the predetermined value and entering the second user operating mode if the first safety parameter value is less than the predetermined value.

[0026] Entering the safe operating mode may include reducing power provided to the induction heating arrangement. Entering the safe operating mode may include ceasing to provide power to the induction heating arrangement. Entering the safe operating mode may include automatically turning off the aerosol generating device. Entering the safe operating mode may include generating a signal to alert a user that an error condition has occurred.

[0027] The susceptor may include a first susceptor material having a first Curie temperature and a second susceptor material having a second Curie temperature, the second Curie temperature being lower than the first Curie temperature, and the second calibration temperature corresponding to the second Curie temperature of the second susceptor material.

[0028] The first susceptor material may be an iron metal and the second susceptor material may include nickel.

[0029] The controller may be further configured to maintain a temperature of the susceptor between the first calibrated temperature and the second calibrated temperature during a second user operation mode of the aerosol generating device to generate the aerosol.

[0030] Performing the calibration process may further include measuring a first calibration value corresponding to the first calibration temperature and a second calibration value corresponding to the second calibration temperature, the first calibration value and the second calibration value being values ​​of current, resistance, or conductance. Controlling the power provided to the induction heating arrangement may include adjusting a temperature of the susceptor based at least in part on the first calibration value and the second calibration value.

[0031] According to a further aspect of the present invention there is provided an aerosol generation system comprising an aerosol generating apparatus as described above and an aerosol-generating article, the aerosol-generating article including an aerosol-forming substrate and a susceptor in thermal contact with the aerosol-forming substrate.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] As used herein, "aerosol cooling element" refers to a component of an aerosol-generating article that is located downstream of an aerosol-forming substrate such that, during use, the aerosol formed by the volatile compounds emitted from the aerosol-forming substrate passes through and is cooled by the aerosol cooling element before being inhaled by the user. Aerosol cooling elements have a large surface area but generate a low pressure drop. Filters and other mouthpieces that generate a high pressure drop (e.g., filters formed of fiber bundles) are not considered aerosol cooling elements. Chambers and cavities within an aerosol-generating article are not considered aerosol cooling elements.

[0038] As used herein, the term "mouthpiece" means that portion of an aerosol-generating article, device, or system that is placed into the mouth of a user for direct inhalation of the aerosol.

[0039] As used herein, the term "susceptor" refers to an element that includes a material capable of converting the energy of a magnetic field into heat. When the susceptor is located in an alternating magnetic field, the susceptor heats up. The heating of the susceptor can be the result of at least one of hysteresis losses and eddy currents induced in the susceptor, depending on the electrical and magnetic properties of the susceptor material.

[0040] As used herein in referring to an aerosol generating device, the terms "upstream" and "forward," as well as "downstream" and "rearward," are used to describe the relative locations of components, or portions of components, of the aerosol generating device in relation to the direction in which air flows through the aerosol generating device during use. An aerosol generating device according to the invention comprises a proximal end through which aerosol exits the device during use. The proximal end of the aerosol generating device may also be referred to as the mouth end or downstream end. The mouth end is downstream of the distal end. The distal end of the aerosol-generating article may also be referred to as the upstream end. Components or portions of components of an aerosol generating device may be described as being upstream or downstream of one another based on their relative location with respect to the airflow path of the aerosol generating device.

[0041] As used herein in referring to an aerosol-generating article, the terms "upstream" and "forward," as well as "downstream" and "rearward" are used to describe the relative positions of components or parts of components of the aerosol-generating article in relation to the direction in which air flows through the aerosol-generating article during use of the aerosol-generating article. The aerosol-generating article according to the present invention comprises a proximal end through which the aerosol exits the article during use. The proximal end of the aerosol-generating article may also be referred to as the mouth end or the downstream end. The mouth end is downstream of the distal end. The distal end of the aerosol-generating article may also be referred to as the upstream end. Components or parts of components of the aerosol-generating article may be described as being upstream or downstream of each other based on their relative positions between the proximal end of the aerosol-generating article and the distal end of the aerosol-generating article. The forward of a component or part of a component of the aerosol-generating article is the part that is at the end closest to the upstream end of the aerosol-generating article. The rearward of a component or part of a component of the aerosol-generating article is the part that is at the end closest to the downstream end of the aerosol-generating article.

[0042] As used herein, the term "inductively coupled" refers to heating a susceptor when penetrated by an alternating magnetic field. The heating may be caused by the generation of eddy currents in the susceptor. The heating may also be caused by magnetic hysteresis losses.

[0043] As used herein, the term "puffing" refers to the act of a user inhaling an aerosol through the user's mouth or nose and into the user's body.

[0044] 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.

[0045] Example 1: A method for controlling aerosol generation in an aerosol generating device, the device comprising an induction heating arrangement and a power source for providing power to the induction heating arrangement, the method comprising: performing a calibration process during a first user operation mode of the aerosol generating device for generating an aerosol, the calibration process including measuring a safety parameter associated with a susceptor inductively coupled to the induction heating arrangement to obtain a first safety parameter value, the susceptor being configured to heat an aerosol-forming substrate, the calibration process including a heating phase from a first calibration temperature of the susceptor to a second calibration temperature, the safety parameter being a duration of the heating phase; and controlling power provided to the induction heating arrangement such that a temperature of the susceptor is adjusted based at least in part on the measured safety parameter during a second user operation mode of the aerosol generating device for generating an aerosol. Example 2: The method of example 1, further comprising performing one or more further calibration processes, the one or more further calibration processes comprising re-measuring a safety parameter associated with the susceptor, and controlling the power provided to the induction heating arrangement such that the temperature of the susceptor is adjusted based at least in part on the measured safety parameter; determining whether a value of the safety parameter re-measured during each further calibration process is greater than a threshold value, the threshold value being based at least in part on the first safety parameter value; and entering a safe operating mode of the aerosol generating device if the value of the safety parameter re-measured during each further calibration process is greater than the threshold value. Example 3: The method of example 2, wherein the threshold value is at least twice the first safety parameter value. Example 4: The method according to the example of Example 1, further comprising performing one or more further calibration processes including re-measuring a safety parameter associated with the susceptor, and controlling the power provided to the induction heating arrangement such that the temperature of the susceptor is adjusted based at least in part on the measured safety parameter, determining whether the value of the safety parameter re-measured during each further calibration process is greater than a threshold value, the threshold value being based at least in part on the value of the safety parameter measured during the last calibration process prior to the each calibration process, and entering a safe operating mode of the aerosol generating device if the value of the safety parameter re-measured during each further calibration process is greater than the threshold value. Example 5: The method of example 4, wherein the threshold value is at least twice the value of the safety parameter measured during the last calibration process prior to each calibration process. Example 6: The method according to one of examples 2 to 5, wherein one or more further calibration processes are performed at predetermined time intervals. Example 7: The method of example 6, wherein each of the predetermined time intervals is between 20 seconds and 50 seconds. Example 8: The method according to any one of Examples 2 to 5, further comprising monitoring one of a current value associated with the susceptor, a conductance value associated with the susceptor, and a resistance value associated with the susceptor, wherein a further calibration process is performed in response to detecting that a change in the monitored current value, conductance value, or resistance value is greater than a threshold change value. Example 9: The method according to any one of Examples 1 to 8, wherein controlling the power provided to the induction heating arrangement such that the temperature of the susceptor is adjusted based at least in part on the measured safety parameter includes comparing a first safety parameter value to a predetermined value associated with the susceptor, and entering a safe operating mode or entering a second user operation mode based on a result of the comparison. Example 10: The method of example 9, wherein entering a safe operating mode or entering a second user operating mode based on the result of the comparison includes entering the safe operating mode if the first safety parameter value is greater than a predetermined value, and entering the second user operating mode if the first safety parameter value is less than the predetermined value. Example 11: The method of any one of examples 2-10, wherein entering the safe operating mode includes reducing power provided to the induction heating arrangement. Example 12: The method of any one of examples 2-10, wherein entering the safe operating mode includes ceasing to provide power to the induction heating device. Example 13: The method of any one of examples 2 to 10, wherein entering the safe operating mode includes automatically turning off the aerosol generating device. Example 14: The method of any one of examples 2-13, wherein entering the safe operating mode includes generating a signal to alert a user that an error condition has occurred. Example 15: The method of any one of Examples 1 to 14, wherein the susceptor comprises a first susceptor material having a first Curie temperature and a second susceptor material having a second Curie temperature, the second Curie temperature being lower than the first Curie temperature, and the second calibration temperature corresponds to the second Curie temperature of the second susceptor material. Example 16: 16. The method of claim 15, wherein the first susceptor material is an iron metal and the second susceptor material comprises nickel. Example 17: The method of any one of Examples 1 to 16, further comprising maintaining a temperature of the susceptor between the first calibrated temperature and the second calibrated temperature during a second user operation mode of the aerosol generating device to generate an aerosol. Example 18: The method of any one of Examples 1 to 17, wherein performing the calibration process further includes measuring a first calibration value corresponding to the first calibration temperature and a second calibration value corresponding to the second calibration temperature, the first calibration value and the second calibration value being current values, resistance values ​​or conductance values, and controlling the power provided to the induction heating arrangement includes adjusting a temperature of the susceptor based at least in part on the first calibration value and the second calibration value. Example 19: an inductor connected to the inductive heating arrangement for generating an alternating magnetic field when energized by an alternating current from the DC / AC converter, the inductor being coupleable with a susceptor, the susceptor being configured to heat an aerosol-forming substrate; and a controller configured to perform a calibration process during a first user operation mode of the aerosol generating device for generating an aerosol, the calibration process including measuring a safety parameter associated with a susceptor inductively coupled to the induction heating arrangement to obtain a first safety parameter value, the susceptor being configured to heat the aerosol-forming substrate, the calibration process including a heating phase from a first calibration temperature of the susceptor to a second calibration temperature, the safety parameter being a duration of the heating phase, and the controller configured to control power provided to the induction heating arrangement such that a temperature of the susceptor is adjusted based at least in part on the measured safety parameter during a second user operation mode of the aerosol generating device for generating an aerosol. Example 20: An aerosol generating device as described in Example 19, wherein the controller is further configured to perform one or more further calibration processes, the one or more further calibration processes including re-measuring a safety parameter associated with the susceptor, and controlling the power provided to the induction heating arrangement such that the temperature of the susceptor is adjusted based at least in part on the measured safety parameter, and determining whether a value of the safety parameter re-measured during each further calibration process is greater than a threshold value, the threshold value being based at least in part on the first safety parameter value, and if the value of the safety parameter re-measured during each further calibration process is greater than the threshold value, the controller is configured to enter a safe operating mode of the aerosol generating device. Example 21: 21. The aerosol generating device of Example 20, wherein the threshold value is at least twice the first safety parameter value. Example 22: An aerosol generating device as described in Example 19, wherein the controller is further configured to perform one or more further calibration processes including re-measuring a safety parameter associated with the susceptor, and controlling the power provided to the induction heating arrangement such that the temperature of the susceptor is adjusted based at least in part on the measured safety parameter, includes determining whether the value of the safety parameter re-measured during each further calibration process is greater than a threshold value, the threshold value being based at least in part on the value of the safety parameter measured during the last calibration process prior to the each calibration process, and wherein if the value of the safety parameter re-measured during each further calibration process is greater than the threshold value, the controller is configured to enter a safe operating mode of the aerosol generating device. Example 23: An aerosol generating device as described in Example 22, wherein the threshold value is at least twice the value of the safety parameter measured during the last calibration process prior to each calibration process. Example 24: An aerosol generating device as described in Examples 20 to 23, wherein the controller is configured to perform one or more further calibration processes at predetermined time intervals. Example 25: 25. The aerosol generating apparatus of Example 24, wherein each of the predetermined time intervals is 20 seconds to 50 seconds. Example 26: An aerosol generating device described in one of Examples 20 to 23, wherein the controller is further configured to monitor one of a current value associated with the susceptor, a conductance value associated with the susceptor, and a resistance value associated with the susceptor, and the controller is configured to perform a further calibration process in response to detecting that a change in the monitored current value, conductance value, or resistance value is greater than a threshold change value. Example 27: An aerosol generating device as described in one of Examples 19 to 26, wherein controlling the power provided to the induction heating arrangement so that the temperature of the susceptor is adjusted based at least in part on the measured safety parameter includes comparing a first safety parameter value with a predetermined value associated with the susceptor, and the controller is configured to enter a safe operating mode or a second user operation mode based on the result of the comparison. Example 28: An aerosol generating device as described in Example 27, wherein entering a safe operating mode or entering a second user operating mode based on the result of the comparison includes entering the safe operating mode if the first safety parameter value is greater than a predetermined value, and entering the second user operating mode if the first safety parameter value is less than a predetermined value. Example 29: The aerosol generating device of any one of Examples 20 to 28, wherein entering the safe operating mode comprises reducing power provided to the induction heating arrangement. Example 30: An aerosol generating device described in one of Examples 20 to 28, wherein entering the safe operating mode includes stopping the supply of power to the induction heating device. Example 31: An aerosol generating device described in one of Examples 20 to 28, wherein entering the safe operating mode includes automatically turning off the aerosol generating device. Example 32: An aerosol generating device described in one of Examples 20 to 31, wherein entering the safe operating mode includes generating a signal to alert a user that an error condition has occurred. Example 33: An aerosol generating apparatus as described in one of Examples 19 to 32, wherein the susceptor includes a first susceptor material having a first Curie temperature and a second susceptor material having a second Curie temperature, the second Curie temperature being lower than the first Curie temperature, and the second calibration temperature corresponding to the second Curie temperature of the second susceptor material. Example 34: 34. The aerosol generating apparatus of example embodiment 33, wherein the first susceptor material is an iron metal and the second susceptor material comprises nickel. Example 35: An aerosol generating device described in one of Examples 19 to 34, wherein the controller is further configured to maintain the temperature of the susceptor between a first calibration temperature and a second calibration temperature during a second user operation mode of the aerosol generating device for generating an aerosol. Example 36: The method of any one of Examples 19 to 35, wherein performing the calibration process further includes measuring a first calibration value corresponding to a first calibration temperature and a second calibration value corresponding to a second calibration temperature, the first calibration value and the second calibration value being current values, resistance values ​​or conductance values, and controlling the power provided to the induction heating arrangement includes adjusting the temperature of the susceptor based at least in part on the first calibration value and the second calibration value. Example 37: An aerosol generating system comprising the aerosol generating device according to any one of Examples 19 to 36 and an aerosol-generating article, the aerosol-generating article including an aerosol-forming substrate and a susceptor in thermal contact with the aerosol-forming substrate.

[0046] The embodiments will now be further described with reference to the following figures: [Brief description of the drawings]

[0047] [Figure 1] FIG. 1 shows a schematic cross-sectional view of an aerosol-generating article. [Figure 2A] FIG. 2A shows a schematic cross-sectional view of an aerosol generating device for use with the aerosol-generating article shown in FIG. [Figure 2B] FIG. 2B shows a schematic cross-sectional view of an aerosol generating device that engages with the aerosol-generating article shown in FIG. [Diagram 3] FIG. 3 is a block diagram showing an induction heating device for the aerosol generating device described in relation to FIG. [Figure 4]FIG. 4 is a schematic diagram showing the electronic components of the induction heating device described in relation to FIG. [Diagram 5] FIG. 5 is a schematic diagram of an inductor of an LC load network of the induction heating device described in relation to FIG. [Figure 6] FIG. 6 is a graph of DC current versus time illustrating the remotely detectable current changes that occur as the susceptor materials undergo their respective phase transitions associated with their respective Curie points. [Figure 7] FIG. 7 shows the temperature profile of the susceptor during operation of the aerosol generating device. [Figure 8] FIG. 8 is a graph of conductance versus time illustrating the remotely detectable change in conductance that can occur if conductance monitoring is interrupted during calibration. [Figure 9] FIG. 9 is a flow diagram illustrating a method for controlling aerosol generation in the aerosol generating device of FIG.

[0048] The drawings should not be construed as limiting the application to only the illustrated and described embodiments of how they can be made and used, and in particular it should be understood that the drawings are not to scale. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0049] 1 shows a schematic side cross-sectional view of an aerosol-generating article 100. The aerosol-generating article 100 comprises a rod of aerosol-forming substrate 110 and a downstream section 115 at a location downstream of the rod of aerosol-forming substrate 110. The aerosol-generating article 100 comprises an upstream section 150 at a location upstream of the rod of aerosol-forming substrate 110. The aerosol-generating article 100 thus extends from an upstream or distal end 180 to a downstream or oral end 170. In use, air is drawn through the aerosol-generating article 100 by a user from the distal end 180 to the oral end 170.

[0050] The downstream section 115 includes a support element 120 located immediately downstream of the rod of the aerosol-forming substrate 110, the support element 120 being longitudinally aligned with the rod 110. An upstream end of the support element 120 abuts a downstream end of the rod of the aerosol-forming substrate 110. In addition, the downstream section 115 includes an aerosol cooling element 130 located immediately downstream of the support element 120, the aerosol cooling element 130 being longitudinally aligned with the rod 110 and the support element 120. An upstream end of the aerosol cooling element 130 abuts a downstream end of 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.

[0051] The support element 120 includes a first hollow tubular segment 125. The first hollow tubular segment 125 is provided in the form of a hollow cylindrical tube made of cellulose acetate. The first hollow tubular segment 125 defines an interior cavity 145 that extends entirely from an upstream end 165 of the first hollow tubular segment 125 to a downstream end 175 of the first hollow tubular segment 125.

[0052] The aerosol cooling element 130 includes a second hollow tubular segment 135. The second hollow tubular segment 135 is provided in the form of a hollow cylindrical tube made of cellulose acetate. The second hollow tubular segment 135 defines an interior cavity 155 that extends all the way from an upstream end 185 of the second hollow tubular segment 135 to a downstream end 195 of the second hollow tubular segment 135. In addition, a ventilation zone (not shown) is provided at a location along the second hollow tubular segment 135. The ventilation level of the aerosol-generating article 100 is about 25 percent.

[0053] The downstream section 115 further includes a mouthpiece 140 positioned immediately downstream of the aerosol cooling element 130. As shown in the drawing in Figure 1, the upstream end of the mouthpiece 140 abuts the downstream end 195 of the aerosol cooling element 130. The mouthpiece 140 is provided in the form of a cylindrical plug of low density cellulose acetate.

[0054] The aerosol-generating article 100 further comprises an elongated susceptor 160 within the rod of the aerosol-generating substrate 110. More specifically, the susceptor 160 is disposed substantially longitudinally within the aerosol-forming substrate 110, such as approximately parallel to the longitudinal axis of the rod 110. As shown in the drawing of Figure 1, the susceptor 160 is positioned at a radially central location within the rod and extends substantially along the longitudinal axis of the rod 110.

[0055] The susceptor 160 extends completely from the upstream end to the downstream end of the rod of the aerosol-forming substrate 110. In fact, the susceptor 160 has substantially the same length as the rod of the aerosol-forming substrate 110. The susceptor 160 is located in thermal contact with the aerosol-forming substrate 110, so that the aerosol-forming substrate 110 is heated by the susceptor 160 when the susceptor 160 is heated.

[0056] The upstream section 150 includes an upstream element 190 located immediately upstream of the rod of the aerosol-forming substrate 110, with the upstream element 190 being longitudinally aligned with the rod 110. The downstream end of the upstream element 190 abuts the upstream end of the rod of the aerosol-forming substrate. This advantageously prevents the susceptor 160 from becoming dislodged. Furthermore, this ensures that a consumer cannot accidentally come into contact with the heated susceptor 160 after use. The upstream element 190 is provided in the form of a cylindrical plug of cellulose acetate surrounded by a hard wrapper.

[0057] The susceptor 160 includes at least two different materials. The susceptor 160 includes at least two layers, namely 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 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 susceptor material may be aluminum, iron, stainless steel or other iron metal. The second susceptor material may be nickel or a nickel alloy. According to a preferred embodiment, the first susceptor material is stainless steel and the second susceptor material is a nickel alloy containing a majority of nickel.

[0058] The susceptor 160 may be formed by electroplating at least one patch of the second susceptor material onto a strip of the first susceptor material. The susceptor 160 may be formed by coating a strip of the second susceptor material onto a strip of the first susceptor material.

[0059] The aerosol-generating article 100 shown in Figure 1 is designed to engage with an aerosol-generating device, such as the aerosol-generating device 200 shown in Figure 2A, to generate an aerosol. The aerosol-generating device 200 comprises a housing 210 having a cavity 220 configured to receive the aerosol-generating article 100, and 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.

[0060] The induction heating device 230 is shown in block diagram form in Figure 3. The induction heating device 230 comprises a DC power supply 310 and a heating arrangement 320 (also referred to as power electronics). The heating arrangement 320 includes a controller 330, a DC / AC converter 340, a matching network 350, and an inductor 240.

[0061] 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.

[0062] The DC / AC converter 340 is configured to supply the inductor 240 with a high frequency alternating current. As used herein, the term "high frequency alternating current" refers to an alternating current having a frequency of about 500 kilohertz to about 30 megahertz. The high frequency alternating current may have a frequency of about 1 megahertz to about 30 megahertz (such as about 1 megahertz to about 10 megahertz, or about 5 megahertz to about 8 megahertz).

[0063] 4 shows diagrammatically the electrical components of the induction heating device 230, in particular the DC / AC converter 340. The DC / AC converter 340 preferably comprises a class E power amplifier. The class E power amplifier comprises a field effect transistor 420, a transistor switch 410, e.g. comprising a metal oxide semiconductor field effect transistor, a transistor switch supply circuit, indicated by arrow 430, for supplying a switching signal (gate-source voltage) to the field effect transistor 420, and an LC load network 440 comprising a series connection of a shunt capacitor C1 and a capacitor C2, corresponding to the inductor 240, and an inductor L2. Furthermore, a DC power supply 310 with a choke L1 is connected to the inductor 240 to supply a DC current I DC along with the DC supply voltage V DC The ohmic resistance of inductor L2, RCoil and the ohmic resistance R of the susceptor 160. Load 4. An ohmic resistance R, which represents a total ohmic load 450, is shown in more detail in FIG.

[0064] Although DC / AC converter 340 is shown as including a class E power amplifier, it should be understood that DC / AC converter 340 may use any suitable circuit for converting DC current to AC current. For example, DC / AC converter 340 may include a class D power amplifier including two transistor switches. As another example, DC / AC converter 340 may include a full-bridge power inverter having four switching transistors acting in pairs.

[0065] Returning to Figure 3, the inductor 240 may receive the AC current from the DC / AC converter 340 through a matching network 350 for optimal matching to the load, although the matching network 350 is not required. The matching network 350 may comprise a small matching transformer. The matching network 350 may improve the power transfer efficiency between the DC / AC converter 340 and the inductor 240.

[0066] As shown in FIG. 2A, the inductor 240 is located adjacent to the distal portion 225 of the cavity 220 of the aerosol generating device 200. Thus, during operation of the aerosol generating device 200, a high frequency alternating current supplied to the inductor 240 causes the inductor 240 to generate a high frequency alternating magnetic field in the distal portion 225 of the aerosol generating device 200. The alternating magnetic field has a frequency preferably between 1 and 30 megahertz, preferably between 2 and 10 megahertz, for example between 5 and 7 megahertz. As can be seen from FIG. 2B, when the aerosol-generating article 100 is inserted into the cavity 200, the aerosol-forming substrate 110 of the aerosol-generating article 100 is located adjacent to the inductor 240 such that the susceptor 160 of the aerosol-generating article 100 is located within this alternating magnetic field. When the alternating magnetic field penetrates the susceptor 160, the alternating magnetic field causes the susceptor 160 to heat up. For example, eddy currents are generated within the susceptor 160 which, as a result, is heated. Further heating is provided by magnetic hysteresis losses within the susceptor 160. The heated susceptor 160 heats the aerosol-forming substrate 110 of the aerosol-generating article 100 to a temperature sufficient to form an aerosol. The aerosol is drawn downstream through the aerosol-generating article 100 and inhaled by the user.

[0067] The controller 330 may be a microcontroller, preferably a programmable microcontroller, that is programmed to regulate the power supply from the DC power supply 310 to the induction heating arrangement 320 to control the temperature of the susceptor 160.

[0068] FIG. 6 shows the DC current I drawn from the power supply 310 over time as the temperature of the susceptor 160 (shown by the dashed line) increases. DC 6 illustrates the relationship between the DC current I and the susceptor materials. More specifically, FIG. 6 illustrates the change in remotely detectable DC current that occurs as the susceptor materials undergo their respective phase transitions associated with their respective Curie points, where the Curie temperature of the second susceptor material is lower than the Curie temperature of the first susceptor material. DCis 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.

[0069] When the susceptor 160 is inductively heated, the apparent resistance of the susceptor 160 increases. This increase in resistance is proportional to the DC current I drawn from the power supply 310. DC , which at constant voltage decreases as the temperature of the susceptor 160 increases. The high frequency alternating magnetic field provided by the inductor 240 induces eddy currents near the susceptor surface, an effect known as the skin effect. The resistance of the susceptor 160 depends partly on the electrical resistivity of the first susceptor material, partly on the resistivity of the second susceptor material, and partly on the depth of the skin layers of each material available to the induced eddy currents, which resistivity depends on temperature.

[0070] When the second susceptor material reaches its Curie temperature, it loses its magnetic properties. This increases the skin layer available for eddy currents in the second susceptor material, which reduces the apparent resistance of the susceptor 160. As a result, the detected DC current I DC increases temporarily. Then, as the skin depth of the second susceptor material begins to increase, the resistance begins to decrease. This is seen as the valley labeled A in Figure 6.

[0071] As heating continues, the current continues to increase until it reaches a maximum skin depth consistent with the point at which the second susceptor material loses its natural magnetic properties. This point corresponds to the Curie temperature (T N ) and can be seen as the hill labeled B in Figure 6. At this point the second susceptor material has undergone a phase change from a ferromagnetic or ferrimagnetic state to a paramagnetic state. The temperature of point B is known because the Curie temperature is specific to a specific material.

[0072] If the inductor 240 continues to generate an alternating magnetic field (i.e., power to the DC / AC converter 340 is not interrupted) after the Curie temperature of the second susceptor material is reached, the eddy currents generated within the susceptor 160 will flow against the resistance of the susceptor 160, causing continued Joule heating of the susceptor 160, which causes the resistance to increase again (and the current to begin to decrease again) until the temperature of the susceptor begins to approach the Curie temperature of the first susceptor material, as shown as the valley labeled C in FIG. 6. This causes more of the skin layer to be available for the eddy currents within the first susceptor material, which decreases the apparent resistance of the susceptor 160. As a result, the detected DC current I DC This point is the Curie temperature (T s ), and can be seen as the hill labeled D in Figure 6. At this point, the first susceptor material has undergone a phase change from a ferromagnetic or ferrimagnetic state to a paramagnetic state, and the susceptor 160 is at a known temperature.

[0073] Thus, when the susceptors are heated for a sufficient time, both susceptor materials undergo a reversible phase transition when heated in the (known) temperature range between their respective valleys and hills, as shown in Figure 6. However, for the purposes of heating the aerosol-generating substrate to form an aerosol, depending on the type of steel, heating through the entire temperature range up to the Curie temperature of the first susceptor material should be avoided, as the Curie temperature of stainless steel exceeds 700 degrees Celsius. Heating to these temperatures should therefore be avoided as it would initiate combustion of the aerosol-generating substrate, which would lead to the generation of smoke instead of aqueous aerosol, thereby impairing taste and producing a number of undesirable components resulting from the combustion process.

[0074] The second susceptor material is selected such that the temperature range between valley A and hill B is suitable for heating the aerosol-forming substrate 110 of the aerosol-generating article 100 to generate an aerosol. As can be seen from FIG. 6, the apparent resistance of the susceptor 160, and therefore the start and end of the phase transition of the second susceptor material, is a function of the DC current I drawn from the power supply 310. DC Alternatively, the apparent resistance of the susceptor 160, and therefore the onset and end of the phase transition of the second susceptor material, can be detected remotely by monitoring the conductance value (conductance is determined by the DC current I DC DC supply voltage V DC is defined as the ratio of the DC supply voltage V DC DC current I DC The power supply 310 can be remotely detected by monitoring at least the DC current I drawn from the power supply 310. DC is monitored by the controller 330. DC is known, but the DC current I drawn from the power supply 310 DC and DC supply voltage V DC It is preferable to monitor both the DC current I DC , the conductance value, and the resistance value may be referred to as source parameters.

[0075] As the susceptor 160 heats up, a first turning point at valley A in Figure 6 (corresponding to a local minimum in current and a local maximum in resistance) corresponds to the beginning of the phase transition. Then, as the susceptor continues to heat up, a second turning point at hill B in Figure 6 (corresponding to a local maximum in current and a local minimum in resistance) corresponds to the end of the phase transition.

[0076] Furthermore, as can be seen from FIG. 6, the apparent resistance of the susceptor 160 (and the corresponding current I drawn from the power supply 310) DC) may vary with the temperature of the susceptor 160 in a strictly monotonic relationship over a particular temperature range of the susceptor 160 (such as between a valley and a hill). The strictly monotonic relationship allows for an unambiguous determination of the temperature of the susceptor 160 from a determination of the apparent resistance (R) or apparent conductance (1 / R). This is because each determined value of the apparent resistance represents only one value of temperature, and there is no ambiguity in the relationship. The monotonic relationship between the temperature of the susceptor 160 and the apparent resistance in the temperature range in which the second susceptor material undergoes a reversible phase transition allows for the temperature of the susceptor 160, and therefore the temperature of the aerosol-forming substrate 110, to be determined and controlled.

[0077] The controller 330 regulates the supply of power provided to the heating arrangement 320 based on the power supply parameters. The heating arrangement 320 receives a DC current I DC The heating arrangement may be provided with a current sensor (not shown) for measuring a DC supply voltage V DC A voltage sensor (not shown) may optionally be included to measure the DC current I. The current sensor and the voltage sensor are located on the input side of the DC / AC converter 340. DC , and optionally a DC supply voltage V DC is provided by a feedback channel to the controller 330 and represents the AC power P AC Controlling further supply of.

[0078] The controller 330 may control the temperature of the susceptor 160 by maintaining the measured power supply parameter value at a target value that corresponds to a target operating temperature of the susceptor 160. The controller 330 may maintain the measured power supply parameter at the target value using any suitable control loop, for example, by using a proportional-integral-derivative control loop.

[0079] 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 power supply parameter measured at the input side of the DC / AC converter 340 is maintained between a first calibration value corresponding to a first calibration temperature and a second calibration value corresponding to a second calibration temperature. The second calibration temperature is the Curie temperature of the second susceptor material (hill B of the current plot in FIG. 6). The first calibration temperature is a temperature at or above the temperature of the susceptor at which the skin depth of the second susceptor material begins to increase, resulting in a temporary drop in resistance (valley A of the current plot in FIG. 6). Thus, the first calibration temperature is a temperature at or above the temperature at maximum permeability of the second susceptor material. The first calibration temperature is at least 50 degrees Celsius lower than the second calibration temperature. At least the second calibration value may be determined by calibration of the susceptor 160, as described in more detail below. The first calibration value and the second calibration value may be stored as calibration values ​​in a memory of the controller 330.

[0080] However, the power supply parameters have a polynomial dependence on temperature, which for most metallic susceptor materials can be approximated to a third polynomial dependence for this purpose, and the first and second calibration values ​​are selected such that this dependence can be approximated as linear between the first and second calibration values, since 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 power supply parameters are adjusted according to the first and second calibration values ​​via a linear equation.

[0081] For example, if the first and second calibration values ​​are conductance values, then the target conductance value corresponding to the target operating temperature may be given as: G Target =G Lower +(x×ΔG) where ΔG is the difference between the first conductance value and the second conductance value, and x is a percentage of ΔG.

[0082] 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 continuously generates an alternating current that heats the susceptor 160 and simultaneously generates a DC current I DC and optionally a DC supply voltage V DC may be measured, preferably every 1 millisecond, for 100 milliseconds.

[0083] For example, if conductance or current is monitored by the controller 330 to adjust the susceptor temperature, the duty cycle of the switching transistor 410 is reduced when the conductance or current reaches or exceeds a value corresponding to the target operating temperature for adjusting the susceptor temperature. If resistance is monitored by the controller 330 to adjust the susceptor temperature, the duty cycle of the switching transistor 410 is reduced when the resistance reaches or falls below a value corresponding to the target operating temperature. For example, the duty cycle of the switching transistor 410 may be reduced to about 10%. In other words, the switching transistor 410 may be switched into a mode that pulses only every 10 milliseconds for a duration of 1 millisecond. During this 1 millisecond on-state (conducting state) of the switching transistor 410, the DC supply voltage V DC and the DC current I DC The value of is measured to determine the conductance. If the conductance decreases (or the resistance increases), indicating that the temperature of the susceptor 160 is below the target operating temperature, then the gate of transistor 410 is again supplied with a train of pulses at the system's selected drive frequency.

[0084] Power may be supplied to the inductor 240 by the controller 330 in the form of a successive series of pulses of current. In particular, power may be supplied to the inductor 240 in a series of pulses, each separated by a time interval. The successive series of pulses may include two or more heating pulses and one or more probing pulses between the successive heating pulses. The heating pulses have an intensity such that they heat the susceptor 160. The probing pulses are separate power pulses that do not heat the susceptor 160, but rather have an intensity such that they obtain feedback on the evolution (decrease) of the power supply parameters and then the susceptor temperature. The controller 330 may control the power by controlling the duration of the time interval between successive heating pulses of power supplied to the inductor 240 by the DC power supply. Additionally or alternatively, the controller 330 may control the power by controlling the length (in other words, the duration) of each of the successive heating pulses of power supplied to the inductor 240 by the DC power supply.

[0085] The controller 330 is programmed to perform a calibration process to obtain calibration values ​​in which the power supply parameters are measured at known temperatures of the susceptor 160. The known temperatures of the susceptor may be a first calibration temperature corresponding to the first calibration value and a second calibration temperature corresponding to the second calibration value. The calibration process is performed each time a user operates the aerosol generating device 200. For example, the controller 330 may be configured to enter a calibration mode to perform the calibration process when a user turns on the aerosol generating device. The controller 330 may be programmed to enter a calibration mode each time a user inserts an aerosol-generating article 100 into the aerosol generating device 200. Thus, the calibration process is performed prior to user operation of the aerosol generating device 200 to generate an aerosol, during a first user operation mode of the aerosol generating device.

[0086] During the heating phase of 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 DC The power supply parameters are monitored by measuring the current through the first turning point (valley A) as described above in connection with FIG. 6, as the susceptor 160 heats up, the measured current decreases until a first turning point (valley A) is reached and the current begins to increase. This first turning point corresponds to a local minimum conductance or current value (local maximum resistance value). The controller 330 may record the power supply parameters at the first turning point as a first calibration value.

[0087] The conductance or resistance is determined by the measured current I DC and the measured voltage V DC Alternatively, the supply voltage V DC may be assumed to be approximately constant. The temperature of the susceptor 160 at the first calibration value is referred to as the first calibration temperature. The first calibration temperature is preferably between 150 degrees Celsius and 350 degrees Celsius. More preferably, when the aerosol-forming substrate 110 includes tobacco, the first calibration temperature is 320 degrees Celsius. The first calibration temperature is at least 50 degrees Celsius lower than the second calibration temperature.

[0088] As the controller 330 continues to control the power provided by the DC / AC converter 340 to the inductor 240, the controller 330 continues to monitor the power source parameter until a second turning point (Hill B) is reached. The second turning point corresponds to the maximum current (corresponding to the Curie temperature of the second susceptor material) before the measured current begins to decrease. This turning point corresponds to a local maximum conductance or current value (local minimum resistance value). The controller 330 records the power source parameter value at the second turning point 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. Once the maximum value is detected, the controller 330 enters the cooling phase of the calibration process and controls the DC / AC converter 340 to discontinue providing power to the inductor 240, resulting in a decrease in the temperature of the susceptor 160 and a corresponding decrease in the measured current.

[0089] This process of continuously heating the susceptor 160 to obtain a first calibration value and a second calibration value due to the shape of the graph may be repeated at least once during the calibration mode. After interrupting the provision of power to the inductor 240, the controller 330 continues to monitor the power source parameter until a third turning point is observed. The third turning point corresponds to a second minimum conductance or current value (second maximum resistance value). Once 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 of the monitored power source parameter is observed. The fourth turning point corresponds to a second maximum conductance or current value (second minimum resistance value). The controller 330 stores the power source parameter value measured at the third turning point as a first calibration value and stores the power source parameter value measured at the fourth turning point as a second calibration value. The repetition of the measurement of turning points corresponding to the minimum and maximum measured current significantly improves subsequent temperature regulation during user operation of the device to generate an aerosol. Preferably, the controller 330 adjusts the power based on the power supply parameter value obtained from the second maximum and second minimum values, which is more reliable since heat requires more time to disperse within the aerosol-forming substrate 110 and the susceptor 160.

[0090] The controller 330 is configured to detect the turning point by measuring a sequence of power supply parameter values. With reference to Figure 6, the sequence of measured power supply parameter values ​​forms a curve, with each value being greater or less than the previous value. The controller 330 is configured to measure the calibration value at the point where the curve begins to flatten. In other words, the controller 330 records the calibration value when the difference between successive power supply parameter values ​​falls below a predefined threshold.

[0091] Furthermore, during the first user operation mode, to further improve the reliability of the calibration process, the controller 310 may be optionally programmed to perform a pre-heating process prior to the calibration process. For example, if the aerosol-forming substrate 110 is particularly dry or in similar conditions, the calibration may be performed before heat spreads into the aerosol-forming substrate 110, reducing the reliability of the calibration value. If the aerosol-forming substrate 110 is wet, the susceptor 160 will take longer to reach the valley temperature (depending on the moisture content of the substrate 110).

[0092] To perform the preheating process, the controller 330 is configured to continuously supply power to the inductor 240. As described above with respect to FIG. 6, the measured current begins to decrease as the temperature of the susceptor 160 increases, until a turning point corresponding to a minimum measured current is reached. At this stage, the controller 330 is configured to wait a predetermined period of time to allow the susceptor 160 to cool before continuing heating. Accordingly, 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 turning point corresponding to a minimum measured current is again reached. At this point, the controller controls the DC / AC converter 340 to again interrupt the supply of power to the inductor 240. The controller 330 again waits the same predetermined time to allow the susceptor 160 to cool before continuing 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. Following the pre-heating process, the calibration process is preferably for a predetermined combined duration of 20 seconds.

[0093] If the aerosol-forming substrate 110 is dry, the first current minimum of the pre-heating process is reached within the predetermined period and the interruption of power is repeated until the end of the predetermined period. If the aerosol-forming substrate 110 is wet, the first current minimum of the pre-heating process is reached towards the end of the predetermined period. Thus, carrying out the pre-heating process for a predetermined duration ensures that, regardless of the physical state of the substrate 110, the substrate 110 has enough time to reach a minimum operating temperature in order to be ready to continue to apply power to reach the first maximum. This allows for calibration as early as possible without the risk that the substrate 110 has not reached the valley beforehand.

[0094] Furthermore, the aerosol-generating article 100 may be configured such that the current minimum is always reached within a predetermined duration of the pre-heating process. If the current minimum 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 with 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 with the aerosol-generating device 200. As another example, the aerosol-generating article 100 may not be configured for use with the heating arrangement 320, for example, if the aerosol-generating article 100 and the aerosol-generating device 200 are manufactured by different manufacturers. Thus, the controller 330 may be configured to generate a control signal to stop operation of the aerosol-generating device 200.

[0095] As mentioned above, as a first step in the calibration process, the pre-heating process may be performed in response to receiving a user input, for example, 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.

[0096] During normal operation when the aerosol generating device 200 is generating an aerosol, the controller 330 will operate in the second user operation mode to heat the aerosol-forming substrate 110 to generate an aerosol. From the second user operation mode, the controller 330 may be programmed to enter a recalibration mode to perform at least a portion of the calibration process at a predetermined interval. The predetermined interval may be a predetermined time interval or a predetermined number of puffs. Additionally or alternatively, the controller 330 may be programmed to enter the recalibration mode to repeat at least a portion of the calibration process in response to detecting that a power supply parameter has become unstable.

[0097] Performing at least a portion of the calibration process may include re-measuring both of the calibration values ​​at both turning points (shown as hill B and valley A in FIG. 6). To perform further calibration processes in the recalibration mode, the controller 330 may adjust the power supply and, optionally, the power supply voltage V DC The current drawn by I DC The power supply parameters associated with the susceptor 160 are monitored by measuring the measured current I as the susceptor 160 heats up during further iterations of the calibration process because the minimum operating temperature of the aerosol generating device is higher than the first calibration temperature. DC reaches a tipping point and the current I DC begins to decrease. This turning point corresponds to the end of the reversible phase transition of the susceptor 160, observed as a local maximum conductance or current value (local minimum resistance value). The controller 330 records the power supply parameter value at the turning point as the re-measured second calibration value.

[0098] Once the turning point is reached, the controller 330 controls the DC / AC converter 340 to decrease the power provided to the inductor 240 until another turning point is observed, which corresponds to the end of the reversible phase transition of the susceptor, observed as a local minimum conductance or current value (local maximum resistance value). The controller 330 records the power supply parameter value at the other turning point as the re-measured first calibration value.

[0099] FIG. 7 is a graph of conductance versus time illustrating a heating profile of the susceptor 160. The graph illustrates two successive user modes: a first user operation mode 710, which is entered when a user turns on the aerosol generating device 200, and a second user operation mode 720, which corresponds to a user operation of the aerosol generating device 200 to generate an aerosol. As described above, in the first user operation mode 710, the controller 330 may operate in a calibration mode 710B to perform a calibration process. Optionally, in the first user operation mode 710, the controller 330 may operate in a pre-heat mode 710A to perform a pre-heat process. It should be understood that FIG. 7 is not drawn to scale. In particular, the first user operation mode 710 has a shorter duration than the second user operation mode 720. For example, the first user operation mode 710 may have a duration of 5 to 30 seconds, preferably 10 to 20 seconds. The second user operation mode 720 may have a duration of between 140 and 340 seconds.

[0100] 7 is illustrated as a graph of conductance versus time, it should be understood that the controller 330 may be configured to control the heating of the susceptor 160 during the first user operation mode 710 and the second user operation mode 720 based on a measured resistance or current, as described above. Indeed, while the techniques for controlling the heating of the susceptor during the first user operation mode 710 and the second user operation mode 720 have been described above based on a determined conductance value or a determined resistance value associated with the susceptor, it should be understood that the techniques described above may be implemented based on a value of a current measured at the input of the DC / AC converter 340.

[0101] As can be seen from FIG. 7, during the second user operation mode 720, heating the aerosol-forming substrate 110 to generate an aerosol includes a plurality of conductance steps corresponding to a plurality 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 temperature at which the aerosol-forming substrate 110 forms an aerosol such that aerosol is formed during each temperature step. The first operating temperature of the susceptor is preferably the lowest temperature at which the aerosol-forming substrate forms aerosol in a volume and amount sufficient for a user to obtain a satisfactory experience when inhaled. The second operating temperature of the susceptor is the highest temperature to which it is desired to heat the aerosol-forming substrate in order for the user to inhale the aerosol.

[0102] The first operating temperature of the susceptor 160 is equal to or greater than the first calibrated temperature of the susceptor 160 corresponding to the first calibrated value (valley A of the current plot shown in FIG. 6). The first operating temperature may be between 150 degrees Celsius and 330 degrees Celsius. The second operating temperature of the susceptor 160 is equal to or less than the second calibrated temperature of the susceptor 160 corresponding to the second calibrated value at the Curie temperature of the second susceptor material (hill B of the current plot in FIG. 6). The second operating temperature may be between 200 degrees Celsius and 400 degrees Celsius. The difference between the first operating temperature and the second operating temperature is at least 50 degrees Celsius. It should be understood that the number of temperature steps shown in FIG. 7 is exemplary and the second heating stage 720 includes at least three consecutive temperature steps, preferably two to fourteen temperature steps, and most preferably three to eight temperature steps. Each temperature step may have a predetermined duration. The duration of the first temperature step is preferably longer than the duration of the subsequent temperature steps. The duration of each temperature step is preferably greater 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 predetermined number of user puffs. Preferably, the first temperature step corresponds to four user puffs and each subsequent temperature step corresponds to one user puff.

[0103] For 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 measured power supply parameter is maintained at a target value corresponding to the target operating temperature of the respective temperature step, the target value being determined with reference to the first and second calibration values ​​as described above.

[0104] As an example, the second heating stage 720 has five temperature steps, a duration of 160 seconds, and a G Target =G Lower A first temperature step 720a with a target conductance value of +(0.09×ΔG), duration of 40 seconds and G Target =G LowerA second temperature step 720b with a target conductance value of +(0.25×ΔG), duration of 40 seconds and G Target =G Lower A third temperature step 720c with a target conductance value of +(0.4×ΔG), duration of 40 seconds and G Target =G Lower A fourth temperature step 720d having a target conductance value of +(0.56×ΔG) and a duration of 85 seconds and G Target =G Lower A fifth temperature step 720e may be included having a target conductance value of +(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.

[0105] Thus, control of the operating temperature of the susceptor 160 to generate the aerosol depends on the first calibration value (corresponding to the first calibration temperature) and the second calibration value (corresponding to the second calibration temperature) measured during the calibration process. In particular, referring back to FIG. 6, control of the operating temperature of the susceptor 160 depends on detection of Hill B, which corresponds to the Curie temperature of the second susceptor material. As described above, the heating phase of the calibration process ends when the controller 330 discontinues providing power to the inductor to reduce the temperature of the susceptor 160. This is triggered by detection of the second turning point (Hill B) in FIG. 6.

[0106] However, if for some reason hill B is not detected, controller 330 does not disable the heating pulse and continues to heat susceptor 160 above the Curie temperature of the second susceptor material, which would result in overheating of the aerosol-forming substrate. If heating continues, valley C will be detected by controller 330. Once valley C is detected, further heating of susceptor 160 is triggered until hill D, which corresponds to the Curie temperature of the first susceptor material, is detected. The temperature of susceptor 160 is then adjusted based on the temperatures corresponding to valley C and hill D. This temperature range is significantly higher than the temperature range between hill B and valley A associated with the second susceptor material.

[0107] 8, which shows a hypothetical scenario in which the controller 330 does not detect hill B during the calibration process due to an event (indicated by three dots) that results in the controller 330 not detecting valley A and hill B associated with the second susceptor material. Such an event could be, for example, a change in the apparent susceptor impedance response detected by the controller as a result of the aerosol-generating article 110 (and thus the susceptor 160) being moved from its correct position during use.

[0108] To prevent such overheating scenarios from occurring, the controller 330 is configured to measure additional parameters (referred to herein as safety parameters) during the calibration process in addition to the first and second calibration values.

[0109] As can be seen from both FIG. 6 and FIG. 8, due to the properties of the first susceptor material and the second susceptor material, the investigation focused on the time it takes to reach hill B from valley A (Δt N ) from valley C to hill D (Δt S ) is always shorter than

[0110] Thus, the controller 330 is configured to measure the duration between the detection of the first turning point at valley A and the detection of the second turning point at hill B during the calibration process. If the duration is longer than a threshold, the controller 330 is configured to enter a safe operating mode to prevent overheating. The threshold is based on a characteristic of the second susceptor material and is measured during the calibration mode during the first heating stage. Additionally or alternatively, the threshold is a predetermined value stored by the controller 330.

[0111] During the calibration mode 710B, a timer associated with the controller 330 is triggered when a first turning point is detected. The timer measures the time until a second turning point is detected. The duration measured by the timer is Δt NThe first value of the safety parameter is stored by the controller 330 as a first value of the safety parameter corresponding to the first value of the safety parameter. The controller 330 then determines and stores a first threshold value for the duration of the subsequent calibration process based on the first value of the safety parameter. The threshold value is defined as follows:

[0112] Threshold = Δt N +Tolerance.

[0113] The purpose of the tolerance is to prevent false overheat detections, which may occur if the threshold is set to a safe parameter value. At the same time, the tolerance is selected based on the characteristics of the first susceptor material, i.e., the threshold is large enough to avoid false overheat detections, but within a typical time interval Δt S This is illustrated in Figure 8. The tolerance is chosen to be at least 0.5 × Δt N , preferably Δt N In other words, the threshold value may be a value of Δt N It can be a multiple of .

[0114] During the second user operation mode 720, when the controller 330 repeats the calibration process, in addition to re-measuring the first and second calibration values, the safety parameter is re-measured by the controller 330. The re-measured value of the safety parameter is compared to the stored first threshold value. If the duration corresponding to the safety parameter value measured during the re-calibration is greater than the threshold value, the controller is configured to enter a safe operating mode of the aerosol generating device. In the safe operating mode, the controller 330 is configured to prevent further heating of the susceptor, for example, by ceasing to provide power to the inductor or immediately switching off the aerosol generating device 200. In the safe operating mode, the controller 330 may be configured to generate a warning or alert to the user to indicate that the safe operating mode has been entered.

[0115] To re-measure the safety parameter value, the controller 330 is configured to measure the time since detection of the first turning point of the calibration process. Comparing the re-measured safety parameter value to a threshold value may include comparing the time elapsed since detection of the first turning point to the threshold value. The controller 330 may then enter the safe operating mode as soon as the time elapsed since detection of the first turning point reaches the threshold value.

[0116] If the controller 330 performs a first time calibration process during the second heating stage 720, the threshold value may be based on the first safety parameter value measured during the calibration mode 710B. During subsequent further calibration processes during the second heating stage 720, each re-measured safety parameter value may be compared to the first safety parameter value measured during the calibration mode.

[0117] Since the temperature of the aerosol-forming substrate 110 surrounding the susceptor 160 increases over time and the temperature of the tipping points (hills and valleys) is fixed, the time required to increase the temperature from the first tipping point to the second tipping point decreases over time, so that the safety parameter value re-measured during each subsequent calibration process during the second heating stage will be of shorter duration than the previously re-measured safety calibration value. Thus, each re-measured safety parameter value may be compared to the most recently measured safety parameter value. For example, the safety parameter value measured during the second calibration process performed in the second heating stage 720 may be compared to the safety parameter value measured during the first calibration process performed in the second heating stage.

[0118] It can be assumed that the measurement of the safety parameter during the calibration process performed during calibration mode 710B is performed properly and the first value of the safety parameter is correctly measured because the aerosol-generating article 100 is at a lower temperature at the start of the calibration mode and the aerosol-forming substrate 110 is not depleted.

[0119] However, during use, a user may inadvertently move the position of the aerosol-generating article 110. Therefore, to further enhance safety, a predetermined threshold value may be stored by the controller 330, and the controller 330 is configured to compare the first measured value of the safety parameter with the predetermined threshold value. Comparing the re-measured safety parameter value with the predetermined threshold value may include comparing the time elapsed since detection of the first turning point with the predetermined threshold value. The controller 330 may then enter the safe operating mode as soon as the time elapsed since detection of the first turning point reaches the predetermined threshold value.

[0120] The predetermined threshold may be determined during manufacture of the aerosol-generating article or based on known properties of the susceptor material. The controller 330 may be configured to enter the second heating mode 720 when the first safety parameter value is less than the predetermined threshold and to enter the safe operating mode when the first safety parameter value is greater than the predetermined threshold.

[0121] 9 is a flow diagram of a method 900 for controlling aerosol generation in the aerosol generating device 200. The controller 330 may be programmed to implement the method 900, as described above.

[0122] The method begins at step 910, where the controller 330 detects user operation of the aerosol generating device 200 to generate aerosol. Detecting user operation of the aerosol generating device 200 may include detecting a user input, such as, for example, user activation of the aerosol generating device 200. Additionally or alternatively, detecting user operation of the aerosol generating device 200 may include detecting that an aerosol-generating article 100 is inserted into the aerosol generating device 200.

[0123] In response to detecting user operation at step 910, the controller 330 enters a first user operation mode. During the first user operation mode, the controller 330 may be configured to perform the optional pre-heating process described above at step 920. At the end of a predetermined duration of the pre-heating process, the controller 330 is configured to perform the calibration process (step 930) described above. Alternatively, during the first user operation mode, the controller 330 may be configured to proceed to step 930 without performing the pre-heating process. After successful completion of the calibration process, the controller 330 enters a second user operation mode and an aerosol is generated for inhalation by the user at step 940.

[0124] For the purposes of this specification and the appended claims, unless otherwise indicated, all numbers expressing amounts, quantities, percentages, and the like should be understood in all instances to be modified by the term "about." Also, all ranges include the maximum and minimum points disclosed, and include any intermediate ranges therein, which may or may not be specifically recited herein. Within this context, the number A may be considered to include a numerical value that is within the general standard error for the measurement of the property that the number A modifies. The number A may deviate by the percentages recited above, in some cases as used in the appended claims, provided that the amount by which A deviates does not materially affect the basic and novel properties of the claimed invention. Also, all ranges include the maximum and minimum points disclosed, and include any intermediate ranges therein, which may or may not be specifically recited herein.

Claims

1. 1. A method for controlling aerosol generation in an aerosol generating device, the device comprising an induction heating arrangement and a power supply for providing power to the induction heating arrangement, the method comprising: performing a calibration process during a first user operation mode of the aerosol-generating device for generating an aerosol, the calibration process including measuring a safety parameter associated with a susceptor inductively coupled to an induction heating arrangement to obtain a first safety parameter value, the susceptor being configured to heat an aerosol-forming substrate, the calibration process including a heating step of the susceptor from a first calibration temperature to a second calibration temperature, the safety parameter being a duration of the heating step; and controlling power provided to the induction heating arrangement such that during a second user operation mode of the aerosol generating device to generate an aerosol, the temperature of the susceptor is adjusted based at least in part on the measured safety parameter.

2. performing one or more additional calibration processes, the one or more additional calibration processes including re-measuring the safety parameters associated with the susceptor; controlling power provided to the induction heating arrangement such that the temperature of the susceptor is regulated based at least in part on the measured safety parameter; determining whether the value of the safety parameter re-measured during each further calibration process is greater than a threshold value, the threshold value being based at least in part on the first safety parameter value; and entering a safe operating mode of the aerosol generating device if the value of the safety parameter re-measured during each further calibration process is greater than the threshold value.

3. The method of claim 2 , wherein the threshold value is at least twice the first safety parameter value.

4. performing one or more additional calibration processes, including re-measuring the safety parameters associated with the susceptor; controlling power provided to the induction heating arrangement such that the temperature of the susceptor is regulated based at least in part on the measured safety parameter; determining whether a value of the safety parameter re-measured during each further calibration process is greater than a threshold value, the threshold value being based at least in part on the value of the safety parameter measured during a last calibration process prior to the respective calibration process; and entering a safe operating mode of the aerosol generating device if the value of the safety parameter re-measured during each further calibration process is greater than the threshold value.

5. The method of claim 4 , wherein the threshold value is at least twice the value of the safety parameter measured during the last calibration process prior to the respective calibration process.

6. controlling power provided to the induction heating arrangement such that the temperature of the susceptor is regulated based at least in part on the measured safety parameter; comparing the first safety parameter value to a predetermined value associated with the susceptor; and entering the safe operating mode or the second user operating mode based on the result of the comparison.

7. entering the safe operating mode or the second user operation mode based on the result of the comparison; entering the safe operating mode if the first safety parameter value is greater than the predetermined value; and entering the second user operation mode if the first safety parameter value is less than the predetermined value.

8. 6. The method of claim 1, further comprising maintaining the temperature of the susceptor between the first calibrated temperature and the second calibrated temperature during the second user operation mode of the aerosol generating device to generate an aerosol.

9. 6. The method of claim 1, wherein performing the calibration process further comprises measuring a first calibration value corresponding to the first calibration temperature and a second calibration value corresponding to the second calibration temperature, the first calibration value and the second calibration value being current values, resistance values, or conductance values, and controlling power provided to the induction heating arrangement comprises adjusting the temperature of the susceptor based at least in part on the first calibration value and the second calibration value.

10. An aerosol generating device, comprising: a power supply for providing a DC supply voltage and a DC current; a power supply electronic device connected to the power supply, DC / AC converters, power supply electronics comprising: an inductor connected to the DC / AC converter to generate an alternating magnetic field when energized by alternating current from the DC / AC converter, the inductor being couplable to a susceptor, the susceptor configured to heat an aerosol-forming substrate; a controller, performing a calibration process during a first user operation mode of the aerosol-generating device for generating an aerosol, the calibration process including measuring a safety parameter associated with a susceptor inductively coupled to the induction heating arrangement to obtain a first safety parameter value, the susceptor being configured to heat an aerosol-forming substrate, the calibration process including a heating step of the susceptor from a first calibration temperature to a second calibration temperature, the safety parameter being a duration of the heating step; and a controller configured to control power provided to the induction heating arrangement so that the temperature of the susceptor is adjusted based at least in part on the measured safety parameter during a second user operation mode of the aerosol generating device for generating an aerosol.

11. the controller is further configured to perform one or more further calibration processes, the one or more further calibration processes including re-measuring the safety parameter associated with the susceptor; controlling power provided to the induction heating arrangement such that the temperature of the susceptor is regulated based at least in part on the measured safety parameter; determining whether a value of the safety parameter re-measured during each further calibration process is greater than a threshold value, the threshold value being based at least in part on the first safety parameter value; 11. The aerosol generating device of claim 10, wherein the controller is configured to enter a safe operating mode of the aerosol generating device if the value of the safety parameter re-measured during each further calibration process is greater than the threshold value.

12. the controller is further configured to perform one or more additional calibration processes, including re-measuring the safety parameters associated with the susceptor; controlling power provided to the induction heating arrangement such that the temperature of the susceptor is regulated based at least in part on the measured safety parameter; determining whether the value of the safety parameter re-measured during each further calibration process is greater than a threshold value, the threshold value being based at least in part on the value of the safety parameter measured during a last calibration process prior to the respective calibration process; 12. The aerosol generating device of claim 11, wherein the controller is configured to enter a safe operating mode of the aerosol generating device if the value of the safety parameter re-measured during each further calibration process is greater than the threshold value.

13. An aerosol generating device according to any one of claims 10 to 12, wherein entering the safe operating mode comprises turning off the aerosol generating device.

14. 13. The aerosol generating device of claim 10, wherein the susceptor comprises a first susceptor material having a first Curie temperature and a second susceptor material having a second Curie temperature, the second Curie temperature being lower than the first Curie temperature, and the second calibration temperature corresponds to the second Curie temperature of the second susceptor material.

15. 1. An aerosol generating system comprising: The aerosol generating device according to any one of claims 10 to 12, an aerosol-generating article comprising the aerosol-forming substrate and the susceptor in thermal contact with the aerosol-forming substrate.

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