Aerosol generating devices and systems

Abstract

The aerosol generating device includes a power supply (10) and an oscillator circuit (36) configured to generate a time-varying electromagnetic field for inductively heating a susceptor (20). The frequency generation circuit of the controller (12A) includes a variable frequency oscillator VFO (32) including a supply voltage terminal configured to receive a regulated supply voltage, a set terminal, and an oscillator output terminal configured to provide an output signal having a frequency determined by a resistance between the supply voltage terminal and the set terminal. The frequency generation circuit also includes a switching circuit (34) electrically connected to the power supply (10) and configured to drive the oscillator circuit (36) at an operating frequency determined by the frequency of the output signal of the VFO (32). A variable resistance component, such as a thermistor (40), is electrically connected between the supply voltage terminal and the set terminal of the VFO (32).

Description

[Technical field]

[0001] The present disclosure relates generally to an aerosol generating device, and more particularly to an aerosol generating device for generating an aerosol for inhalation by a user. Embodiments of the present disclosure also relate to an aerosol generating system including an aerosol generating device and an aerosol-generating article including a susceptor and an aerosol-generating material.

[0002] The present disclosure also generally relates to a method for controlling heating of a susceptor in an aerosol generation system.

[0003] The present disclosure is particularly applicable to portable (handheld) aerosol generating devices. Such devices heat an aerosol-generating material or substrate, such as tobacco or other suitable material, by conduction, convection and / or radiation, rather than combustion, to generate an aerosol for inhalation by a user. The present disclosure particularly relates to inductively heated aerosol generating devices. [Background technology]

[0004] In recent years, devices that heat, rather than burn, an aerosol-generating material to generate an aerosol for inhalation have become popular with consumers. Commonly available risk-reducing or risk-modifying devices are material-heated aerosol-generating devices or so-called heated non-combustion devices. This type of device generates an aerosol or vapor by heating the aerosol-generating material to a temperature typically in the range of 150°C to 300°C. Heating the aerosol-generating material to a temperature in this range, without burning the aerosol-generating material, typically generates a vapor that cools and condenses to form an aerosol for inhalation by the user of the device.

[0005] Such devices may provide heat to the aerosol-generating material using one of several different approaches. One such approach is to provide an aerosol-generating device that uses an induction heating system into which a user can removably insert an aerosol-generating article that includes the aerosol-generating material. In such devices, an induction coil is provided in the device and an inductively heatable susceptor is provided in the aerosol-generating article. When a user activates the device, electrical energy is provided to the induction coil, which in turn generates an alternating electromagnetic field. The susceptor couples with the electromagnetic field to generate heat that is transferred, for example by conduction, to the aerosol-generating material, which heats up and generates an aerosol.

[0006] Generally, it is desirable to control the heat of the aerosol-generating material to ensure that an aerosol with acceptable properties is generated for inhalation by the user throughout the period of use (also known as a vaping session). Embodiments of the present disclosure seek to provide an improved user experience in which the properties of the generated aerosol are optimized through more precise control of the heat of the aerosol-generating material by the susceptor. Summary of the Invention [Means for solving the problem]

[0007] According to a first aspect of the present disclosure, there is provided an aerosol generating device comprising: a power source, e.g., a battery or cell; an oscillator circuit configured to generate a time-varying electromagnetic field for inductively heating the susceptor; 1. A frequency generating circuit comprising: A variable frequency oscillator (VFO), a supply voltage terminal configured to receive a supply voltage; -Set terminal, an oscillator output terminal configured to provide an output signal having a frequency determined by an input signal to the set terminal; a variable frequency oscillator (VFO) including: a switching circuit electrically connected to the power supply and configured to drive the oscillator circuit at an operating frequency determined by the frequency of the output signal of the VFO; A variable resistor component electrically connected to the set terminal of the VFO; A frequency generating circuit including: An aerosol generating device is provided, comprising:

[0008] The susceptor may be an inductively heatable susceptor, which also includes an aerosol-generating material and may be part of an aerosol-generating article that is removably insertable into the device.

[0009] The oscillator circuit may include a capacitor and an induction coil arranged to generate a time-varying electromagnetic field for inductively heating the susceptor. The susceptor and oscillator circuit have a resonant frequency f that depends on the values ​​of resistance R, capacitance C, and inductance L. o For example, a parallel RLC circuit having The file is TIFF2025517275000002.tif16170.

[0010] The resistance R of the parallel RLC circuit depends on the precise positioning of the susceptor relative to the induction coil and the susceptor's resistance, which changes with temperature. This means that the resonant frequency of the parallel RLC circuit changes over the course of a vaping session as the temperature of the susceptor changes. For the most efficient heating, the oscillator circuit is preferably driven at an operating frequency that approximately matches the resonant frequency. Providing more efficient heating can lead to improved aerosol generation. The device according to the present disclosure therefore aims to adjust the operating frequency to match the changing resonant frequency of the parallel RLC circuit to provide improved heating and a better user experience. The device uses a frequency generation circuit that has a simple design, is robust, and is cost-effective to implement. This therefore allows for a more compact, efficient, and lightweight aerosol generation device.

[0011] The VFO may be, for example, an integrated circuit (IC) device.

[0012] The input signal provided to the set terminal of the VFO may be a resistance between the supply voltage terminal and the set terminal. The frequency of the output signal of the VFO may be determined by the resistance between the supply voltage terminal and the set terminal. A variable resistance component may be electrically connected between the supply voltage terminal and the set terminal of the VFO.

[0013] The VFO outputs a signal with a frequency of f osc is the resistance R between the supply voltage terminal and the set terminal, which is specified by the variable resistance component. set can be directly related to, for example, TIFF2025517275000003.tif17170, where N can be chosen to be 100, 10 or 1 depending on the frequency range required.

[0014] The switching circuit may include, for example, one or more semiconductor switches controlled to switch at an operating frequency specified by a selectable frequency of the output signal of the VFO. The switching circuit drives an oscillator circuit at the operating frequency to generate an alternating electromagnetic field at the same frequency for heating the susceptor. The switching circuit may be configured to operate at a frequency of about 80 kHz to 500 kHz, optionally about 150 kHz to 250 kHz, optionally about 200 kHz. The switching circuit may be configured to operate at a higher frequency, for example in the MHz range, depending on the type of inductively heatable susceptor used. The frequency range of the output signal of the VFO may be selected accordingly. The switching circuit may be an inverter.

[0015] The device may further include a voltage regulator, for example a low dropout regulator (LDO). The voltage regulator may include a voltage regulator output terminal electrically connected to the power supply and configured to provide a regulated supply voltage. A supply voltage terminal of the VFO may be electrically connected to the voltage regulator output terminal such that the VFO receives the regulated supply voltage. The regulated supply voltage may be provided to other components such as a digital potentiometer and a frequency divider, which will be described below. Using a regulated supply voltage may provide stable operation of the frequency generation circuit and other components.

[0016] In one embodiment, the variable resistance component may be a thermistor whose internal resistance changes with temperature. The thermistor may be placed near the susceptor and / or the aerosol-generating material in use. For example, the thermistor may be located adjacent to or within a portion of the device, such as a heating chamber or aerosol-generating space adapted to receive an aerosol-generating article including a susceptor and an aerosol-generating material. The thermistor may be attached to a surface of the heating chamber or aerosol-generating space, such as an internal sidewall or bottom wall of the heating chamber or aerosol-generating space. The thermistor may also be located within the aerosol-generating article and be in electrical contact with the VFO when the article is inserted into the device. The thermistor may be in direct contact with the susceptor or aerosol-generating material. As the temperature of the susceptor changes, the internal resistance of the thermistor located in close proximity changes accordingly. The thermistor may be selected such that its internal resistance changes appropriately as a function of temperature. In one embodiment, for example, the thermistor may have a negative temperature coefficient (NTC), such that its resistance decreases with increasing temperature and vice versa. The resistance of a thermistor can change linearly or non-linearly with temperature.

[0017] Since the frequency of the output signal of the VFO is determined by the resistance between the supply voltage terminal and the set terminal, i.e. between the terminals to which the thermistor is electrically connected, this means that any change in the internal resistance of the thermistor automatically results in a corresponding change in the frequency of the output signal of the VFO, and therefore in a corresponding change in the operating frequency at which the switching circuit drives the oscillator circuit. In particular, the thermistor can be selected and positioned relative to the susceptor such that a change in the temperature of the susceptor, which results in a change in the resonant frequency of the parallel RLC circuit, also results in a change in its internal resistance, which therefore results in a corresponding change in the operating frequency generated by the frequency generating circuit. The operating frequency can therefore be made to track changes in the resonant frequency of the parallel RLC circuit so that the device operates at optimum efficiency.

[0018] The device may further include a control unit or processor, for example a microcontroller unit or a microprocessor unit.

[0019] The variable resistance component may be a digital potentiometer having a resistance selectively changed by the control unit. The digital potentiometer may include a first potentiometer terminal electrically connected to a set terminal of the VFO, a second potentiometer terminal electrically connected to a supply voltage terminal of the VFO, and at least one data terminal configured to receive command data from the control unit to selectively change the resistance of the digital potentiometer. The control unit may be configured to change the resistance of the digital potentiometer based on the estimated or determined impedance value of the parallel RLC circuit. In particular, the device may further include a voltage sensor configured to provide a voltage measurement and a current sensor configured to provide a current measurement. The voltage and current measurements may be used to estimate or determine the impedance value. In these embodiments, the control unit may control the digital potentiometer such that the frequency of the output signal of the VFO is changed in response to changes in the resonant frequency of the oscillator circuit.

[0020] The control unit may be configured to receive the voltage and current measurements provided by the voltage and current sensor and estimate or determine an impedance value using the voltage and current measurements. The device may also include a frequency divider configured to receive the voltage and current measurements provided by the voltage and current sensor. The frequency divider may output an impedance value estimated or determined using the voltage and current measurements to the control unit. A first low pass filter may be connected between the voltage sensor and the frequency divider. A second low pass filter connected between the current sensor and the frequency divider.

[0021] An increase in the impedance value may indicate an increase in the resonant frequency of the parallel RLC circuit, and vice versa. The control unit may include a suitable control scheme for deriving command data for selectively varying the resistance of the digital potentiometer based on the change in the impedance value. In particular, if the impedance value changes, indicating a change in the resonant frequency of the parallel RLC circuit, the command data changes the resistance of the digital potentiometer accordingly. Since the frequency of the output signal of the VFO is determined by the resistance between the supply voltage terminal and the set terminal, i.e., between the terminals to which the digital potentiometer is electrically connected, this means that any change in the resistance of the digital potentiometer automatically results in a corresponding change in the frequency of the output signal of the VFO, and therefore in a corresponding change in the operating frequency at which the switching circuit drives the oscillator circuit. In particular, the control scheme of the control unit may be selected such that a change in the impedance value, indicating a change in the resonant frequency of the RLC circuit, as a result of a temperature change of the susceptor, results in a change in the selected resistance of the digital potentiometer, which, in turn, results in a corresponding change in the operating frequency generated by the frequency generating circuit. The operating frequency can therefore be made to track changes in the resonant frequency of the parallel RLC circuit so that the device operates at optimum efficiency. Such operation of the device can result in improved aerosol generation.

[0022] According to a second aspect of the present disclosure, there is provided an aerosol generating device as described herein, the aerosol generating device being configured, in use, to receive an aerosol-generating article comprising a susceptor and an aerosol-generating material.

[0023] According to a third aspect of the present disclosure, there is provided an aerosol generation system for generating an aerosol for inhalation by a user, the aerosol generation system comprising an aerosol generating device as described herein and an aerosol-generating article comprising a susceptor and an aerosol-generating material.

[0024] The aerosol generating system is adapted to heat the aerosol generating material to volatilize at least one component of the aerosol generating material without burning the aerosol generating material, thereby generating an aerosol for inhalation by a user of the aerosol generating system.

[0025] Generally speaking, a vapor is a substance that is in the gas phase below its critical temperature, meaning that it can be condensed into a liquid by increasing the pressure without decreasing the temperature, while an aerosol is fine solid particles or liquid droplets suspended in air or another gas. However, it should be noted that the terms "aerosol" and "vapor" may be used interchangeably herein, particularly with respect to the form of inhalable medium that is produced for a user to inhale.

[0026] The induction coil may comprise Litz wire or Litz cable, although it will be appreciated that other materials may be used. The induction coil may be generally helical in shape, for example extending around a space in which the aerosol-generating article is received in use.

[0027] The circular cross-section of the helical induction coil may facilitate insertion of the aerosol-generating device, e.g., the aerosol-generating article, into the space in which it is received during use, and may ensure uniform heating of the aerosol-generating material.

[0028] Inductively heatable susceptors may include, but are not limited to, one or more of aluminum, iron, nickel, stainless steel, and alloys thereof, such as nickel-chromium or nickel-copper. Application of an electromagnetic field in the vicinity of the susceptor may cause the susceptor to generate heat by causing electromagnetic-to-thermal energy conversion through eddy currents and magnetic hysteresis losses.

[0029] The induction coil may be configured, in use, to operate with a varying electromagnetic field having a magnetic flux density of about 20 mT to about 2.0 T (at the point of highest density).

[0030] The aerosol-generating material can be any type of solid or semi-solid material. Exemplary types of aerosol-generating solids include powders, granules, pellets, flakes, strands, particles, gels, strips, loose-leaf, cut filler, porous materials, foamed materials, or sheets. The aerosol-generating material can include plant-derived materials, particularly tobacco. When heated by the susceptor, the aerosol-generating material can release volatile compounds. The volatile compounds can include flavor compounds, such as nicotine or tobacco flavorings.

[0031] The foam material may include a plurality of particulates (e.g., tobacco particles) and may also include a quantity of water and / or moisture additives, such as humectants. The foam material may be porous and may allow the flow of air and / or steam through the foam material.

[0032] The aerosol-generating material may include an aerosol former. Examples of aerosol formers include polyhydric alcohols, such as glycerin or propylene glycol, and mixtures thereof. Typically, the aerosol-generating material may include an aerosol former content of about 5% to about 50% by dry weight. In some embodiments, the aerosol-generating material may include an aerosol former content of about 10% to about 20% by dry weight, and in some cases about 15% by dry weight.

[0033] The aerosol-generating article may include a breathable shell that contains the aerosol-generating material. The breathable shell may include an electrically insulating, non-magnetic breathable material. The material may be highly breathable and allow air to flow through the material that is resistant to high temperatures. Examples of suitable breathable materials include cellulose fibers, paper, cotton, and silk. The breathable material may also function as a filter. Alternatively, the aerosol-generating article may include an aerosol-generating substance wrapped in paper. Alternatively, the aerosol-generating material may be contained inside a material that is not breathable but includes suitable perforations or openings to allow air to flow through. The aerosol-generating article may be formed in a generally stick shape and may generally resemble a cigarette with a tubular region in which the aerosol-generating material is disposed in a suitable configuration. The aerosol-generating article may include a filter segment at its proximal end, the filter segment including, for example, cellulose acetate fibers. The filter segment may constitute a mouthpiece filter and may be coaxially aligned with the aerosol-generating material. Some designs may also include one or more vapor collection regions, cooling regions, and other structures. For example, the aerosol-generating article may include at least one tubular segment upstream of the filter segment, which may operate as a vapor cooling region that may advantageously allow heated vapor generated by heating the aerosol-generating material to cool and condense to form an aerosol having suitable properties for inhalation by a user, for example through the filter segment.

[0034] According to a fourth aspect of the present disclosure, there is provided a method of controlling heating of a susceptor of an aerosol generation system for generating an aerosol for inhalation by a user, the system comprising: Power supply, an oscillator circuit configured to generate a time-varying electromagnetic field for inductively heating the susceptor; a frequency generation circuit including a VFO, a switching circuit electrically connected to a power source, and a variable resistance component; A method is provided that includes controlling the VFO to provide an output signal having a frequency determined by the resistance of a variable resistance component, and driving an oscillator circuit at an operating frequency determined by the frequency of the VFO's output signal.

[0035] As explained above, the variable resistance component may be a thermistor having an internal resistance that changes with temperature or a digital potentiometer having a resistance that is selectively varied, for example, by a control unit. [Brief description of the drawings]

[0036] [Figure 1] FIG. 1 is a schematic diagram of an example of an aerosol generation system. [Diagram 2] FIG. 2 is a schematic diagram of a first example of a controller for the aerosol generation system of FIG. [Diagram 3] FIG. 2 is a schematic diagram of a second example of a controller for the aerosol generation system of FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0037] Embodiments of the present disclosure will now be described, by way of example only, and with reference to the accompanying drawings, in which:

[0038] Referring initially to Figure 1, an example of an aerosol generating system 1 is shown in a schematic diagram. The aerosol generating system 1 includes an aerosol generating device 2 and an aerosol generating article 16. The aerosol generating device 2 includes a device body 8 having a proximal end 4 and a distal end 6, which may be configured to operate at high frequencies, and which includes a power source 10 and a controller 12. The power source 10 typically includes one or more batteries, which may be inductively charged, for example. The controller 12 typically includes one or more microcontroller units (MCU) or microprocessor units (MPU).

[0039] The aerosol-generating device 2 is generally cylindrical and includes a generally cylindrical aerosol-generation space 14, for example in the form of a heating chamber or compartment, at a proximal end 4 of the aerosol-generating device 2. The cylindrical aerosol-generation space 14 is arranged to receive a correspondingly shaped, generally cylindrical aerosol-generating article 16, which contains an aerosol-generating material 18 and one or more inductively heatable susceptors 20. The aerosol-generating article 16 typically includes a non-metallic cylindrical outer shell 16a and breathable layers or membranes 16b, 16c at the proximal and distal ends to contain the aerosol-generating material 18 and allow air to flow through the aerosol-generating article 16. The aerosol-generating article 16 is a disposable article and may include, for example, tobacco as the aerosol-generating material 18.

[0040] The aerosol generation device 2 includes a helical induction coil 22 having a circular cross section and extending around a cylindrical aerosol generation space 14. The induction coil 22 may be energized by a power source 10 and a controller 12. As described in more detail below, the controller 12 includes, among other electronic components, a switching circuit (e.g., an inverter) arranged to convert direct current from the power source 10 into alternating high frequency current for the induction coil 22.

[0041] The aerosol generation device 2 includes one or more air inlets 24 in the device body 8 that allow ambient air to flow into the aerosol-generation space 14. The aerosol generation device 2 also includes a mouthpiece 26 having an air outlet 28. The mouthpiece 26 is removably attached to the device body 8 at the proximal end 4 to provide access to the aerosol-generation space 14 for purposes of inserting or removing an aerosol-generating article 16.

[0042] As will be appreciated by those skilled in the art, when the induction coil 22 is energized during use of the aerosol-generating system 1, an alternating, time-varying electromagnetic field is generated. This electromagnetic field couples with the one or more inductively heatable susceptors 20 and generates eddy currents and / or magnetic hysteresis losses in the one or more inductively heatable susceptors, heating the susceptors. This heat is then transferred from the one or more inductively heatable susceptors 20 to the aerosol-generating material 18 by, for example, conduction, radiation, and convection.

[0043] The inductively heatable susceptor 20 may be in direct or indirect contact with the aerosol-generating material 18 such that when the susceptor is inductively heated by the induction coil 22, heat is transferred from the susceptor to the aerosol-generating material to heat the aerosol-generating material, thereby generating an aerosol. The susceptor 20 may have any suitable shape and configuration, such as a planar shape, a particulate shape, or a combination thereof. Aerosolization of the aerosol-generating material 18 is facilitated by adding air from the surrounding environment through the air inlet 24. The aerosol generated by heating the aerosol-generating material 18 exits the aerosol-generation space 14 through the air outlet 28 where it may be inhaled by a user of the device 2. The flow of air through the aerosol-generation space 14, i.e., from the air inlet 24 through the aerosol-generation space and out the air outlet 28, may be assisted by a negative pressure created by the user drawing air from the air outlet side of the device 2.

[0044] The induction coil 22 forms part of an oscillator circuit that also includes a capacitor. A parallel RLC circuit includes the induction coil 22, the capacitor and the inductively heatable susceptor 20 of the aerosol-generating article 16 and has a resonant frequency that changes during operation of the aerosol-generating system 1 as a result of changes in temperature of the susceptor 20.

[0045] A first example of a controller 12A is shown in Figure 2. The controller 12A includes a low dropout (LDO) regulator 30 that is electrically connected to the power supply 10. The LDO includes an input terminal (labeled "IN") that is connected to the power supply 10, and an output terminal (labeled "OUT") that provides a regulated voltage supply. The ground terminal (labeled "GND") is electrically connected to ground.

[0046] Controller 12A includes an integrated circuit (IC) variable frequency oscillator (VFO) 32. The VFO may be implemented using, for example, an LTC® 1799 from Analog Devices, One Analog Way, Wilmington, MA 01887, United States of America. The LTC® 1799 is a precision oscillator with an oscillator frequency selected by an external resistor. VFO 32 includes a supply voltage terminal (labeled “V+”) that is electrically connected to the output terminal of VDO 30 and configured to receive a regulated supply voltage (e.g., 2.7 to 5.5 V). VFO 32 is configured to be regulated by an external resistor (R set ) for providing an output signal (e.g., a square wave signal) having a frequency specified by f osc is determined by the following formula: TIFF2025517275000004.tif14170 where N can be chosen to be 100, 10 or 1 depending on the frequency range required. In practice this can be done by electrically connecting the split terminals (not shown) of the VFO to one of the regulated supply voltage, the open circuit voltage and ground. The oscillator frequency can be in the range of 1 kHz to 33 MHz.

[0047] From the above formula, the external resistor R set If increases, the oscillator frequency f osc It can be seen that decreases and vice versa.

[0048] The VFO 32 also includes a ground terminal (labeled "GND") that is electrically connected to ground.

[0049] The switching circuit 34 is electrically connected to the power source 10 and configured to drive an oscillator circuit 36 ​​at an operating frequency specified by an oscillator frequency. The oscillator circuit 36 ​​includes a capacitor 38 and an induction coil 22. A parallel RLC circuit includes the capacitor 38, the induction coil 22, and one or more inductively heatable susceptors 20 that are part of the aerosol-generating article 16.

[0050] In the first controller 12A shown in FIG. 2, the thermistor 40 is electrically connected between the supply voltage terminal and the set terminal of the VFO 32. The internal resistance of the thermistor 40 changes with temperature and is proportional to the external resistance R set As a result, any change in the internal resistance of the thermistor 40 automatically changes the oscillator frequency f osc changes, and thus the frequency at which the oscillator circuit 36 ​​is driven by the switching circuit 34. The thermistor 40 may be located, for example, adjacent to or within the aerosol-generation space 14 shown in FIG. 1, where it undergoes temperature changes similar to those experienced by the susceptor 20 during operation of the aerosol-generation system 1, and in particular during heating of the aerosol-generating material 18. As the temperature of the susceptor changes, the internal resistance of the thermistor 40 changes accordingly. The thermistor 40 is selected such that its internal resistance decreases with increasing temperature, and vice versa. As the resonant frequency of the parallel RLC circuit increases due to an increase in temperature of the susceptor 22, the internal resistance of the thermistor 40 decreases. Thus, an external resistor R electrically connected between the supply voltage terminal and the set terminal of the VFO 32 set Also decreases the oscillator frequency f osc On the other hand, when the resonant frequency of the parallel RLC circuit decreases due to a decrease in temperature of the susceptor 22, the internal resistance of the thermistor 40 increases. set also increases, and the oscillator frequency f oscis decreased. The oscillator frequency can therefore track the resonant frequency of the parallel RLC circuit without the need for any additional sensors. The thermistor 40 can be selected so that the change in the oscillator frequency f osc as a result of changes in its internal resistance approximately matches the change in the resonant frequency of the parallel RLC circuit, i.e., the oscillator frequency and the resonant frequency remain approximately matched as the temperature of the susceptor 20 changes.

[0051] 3 illustrates an alternative controller 12B with similar components labeled with the same reference numerals. In the second controller 12B, a digital potentiometer 42 is electrically connected between the supply voltage terminal and the set terminal of the VFO 32. The digital potentiometer 42 may be implemented, for example, using an MCP483X from Microchip Technology Inc., 2355 West Chandler Blvd., Chandler, Arizona, United States of America. The MCP453X device is an I 2 4. Digital potentiometer 42 is a single channel volatile 7-bit (129 wiper steps) digital potentiometer with a C compatible interface. Digital potentiometer 42 includes a supply voltage terminal (labeled "VDD") electrically connected to the output terminal of VDO 30 and configured to receive the same regulated supply voltage as VFO 32. Digital potentiometer 42 includes a first potentiometer terminal (labeled "P0A") electrically connected to a set terminal of VFO 32 and a second potentiometer terminal (labeled "P0B") electrically connected to the supply voltage terminal of the VFO. The set terminal of VFO 32 may alternatively be electrically connected to a third potentiometer (or wiper) terminal (labeled "P0W").

[0052] Digital potentiometer 42 includes a ground terminal (labeled "VSS") that is electrically connected to ground.

[0053] Digital potentiometer 42 includes a serial data terminal (labeled "SDA") and a serial clock terminal (labeled "SCL").

[0054] MCU44 is 2 C protocol is used to provide command data to the digital potentiometer 42. The command data selectively varies the resistance of the digital potentiometer 42 and thus the R set The MCU 44 also provides clock data. The communication protocol is 2 C, other suitable serial protocols (eg, SPI or UART) or parallel protocols may be used instead.

[0055] Using an appropriate control scheme, the MCU 44 may generate command data to increase or decrease the resistance of the digital potentiometer 42. The MCU 44 selectively varies the resistance of the digital potentiometer 42 based on an estimated or determined impedance value of the parallel RLC circuit, which indicates a change in resonant frequency.

[0056] The controller 12B includes a voltage sensor 46 and a current sensor 48 that provide voltage and current measurements, respectively. The voltage measurements are provided to a first low pass filter 50 and the current measurements are provided to a second low pass filter 52. The unfiltered voltage and current measurements are provided directly to the MCU 44, where they may be used for fast protection monitoring, for example, to prevent overheating of the aerosol-generating material. The first low pass filter 50 and the second low pass filter 52 may output filtered (or averaged) voltage and current measurements, which may simplify the impedance calculation of the oscillator circuit.

[0057] The filtered voltage and current measurements are provided to a frequency divider (or multiplier / divider) 54. The frequency divider 54 includes a first input terminal (labeled "X1"), a second input terminal (labeled "X2"), a third input terminal (labeled "Z1"), a fourth input terminal (labeled "Z2"), and an output terminal (labeled "W"). The second and third input terminals are electrically connected to ground. The first input terminal is electrically connected to a second low pass filter 52 and receives the filtered current measurement from the current sensor 48. The fourth input terminal is electrically connected to a first low pass filter 50 and receives the filtered voltage measurement from the voltage sensor 46. The frequency divider 54 uses the filtered voltage and current measurements to estimate or determine an impedance value of the parallel RLC circuit. In particular, an output signal indicative of the impedance value is determined by the following equation: TIFF2025517275000005.tif15170

[0058] The frequency divider 54 may calculate the impedance value of the oscillator circuit 36 ​​instead of the MCU 44. This may result in faster calculation of the impedance value.

[0059] The output signal from the output terminal of the frequency divider 54 and the trim signal (V trim ) is provided to an operational amplifier 56. The output signal from the operational amplifier 56 is provided to the MCU 44. The output signal from the divider 54 corresponds to a background value of the calculated impedance values. By trimming the background value and amplifying the remaining impedance values, the resolution of the impedance values ​​may be improved.

[0060] An increase in the impedance value of the parallel RLC circuit typically indicates an increase in the resonant frequency, and vice versa. Using an appropriate control scheme, the MCU 44 determines whether the output signal from the operational amplifier 54 indicates that the resonant frequency of the parallel RLC circuit is increasing or decreasing. If the MCU 44 determines that the resonant frequency is increasing, it controls the digital potentiometer 42 to decrease its resistance by an appropriate amount. Thus, the external resistor R set decreases, and the oscillator frequency f osc On the other hand, if the MCU 44 determines that the resonant frequency is decreasing, it controls the digital potentiometer 42 to increase its resistance by an appropriate amount. set increases, and the oscillator frequency f osc By varying the resistance of the digital potentiometer 42, the MCU 44 can make the oscillator frequency track the resonant frequency of the parallel RLC circuit. The digital potentiometer 42 reduces the oscillator frequency f osc can be controlled so that the change in the oscillator frequency approximately matches the change in the resonant frequency of the parallel RLC circuit, ie, so that the oscillator frequency and the resonant frequency remain approximately matched as the temperature of the susceptor 20 changes.

[0061] Although exemplary embodiments have been described in the preceding paragraphs, it should be understood that various modifications may be made to those embodiments without departing from the scope of the appended claims. Thus, the breadth and scope of the claims should not be limited to the exemplary embodiments described above. For example, a series-parallel RLC circuit may be used instead of the parallel RLC circuit described above.

[0062] Any combination of the above-described features in all possible variations thereof is encompassed by the present disclosure unless otherwise indicated herein or clearly contradicted by context.

[0063] Unless the context clearly dictates otherwise, throughout this specification and the claims, the words "comprise", "comprising", and the like are to be construed in an inclusive sense, i.e., "including but not limited to," rather than in an exclusive or exhaustive sense.

Claims

1. An aerosol generating device (2), a power supply (10), an oscillation circuit (36) configured to generate a time-varying electromagnetic field for inductively heating a susceptor (20), a frequency generation circuit, a variable frequency oscillator VFO (32), - a supply voltage terminal configured to receive a supply voltage, - a set terminal, - an oscillator output terminal configured to provide an output signal having a frequency specified by an input signal to the set terminal and including the variable frequency oscillator VFO (32), a switching circuit (34) electrically connected to the power supply (10) and configured to drive the oscillation circuit (36) at an operating frequency specified by the frequency of the output signal of the VFO (32), a variable resistance component (40, 42) electrically connected to the set terminal of the VFO (32), and including the frequency generation circuit, and including the aerosol generating device (2).

2. further including a voltage regulator (30) including a voltage regulator output terminal configured to be electrically connected to the power supply (10) and provide a regulated supply voltage, wherein the supply voltage terminal of the VFO (32) is electrically connected to the voltage regulator output terminal, the aerosol generating device (2) according to claim 1.

3. The variable resistance component is a thermistor (40) having an internal resistance that changes with temperature, the aerosol generating device (2) according to claim 1.

4. further including a heating chamber or an aerosol generating space (14), wherein the thermistor (40) is attached to the surface of the heating chamber or the aerosol generating space (14), the aerosol generating device (2) according to claim 3.

5. The aerosol generating device (2) according to claim 1, further comprising a control unit (44), wherein the variable resistance component is a digital potentiometer (42) having a resistance that is selectively changed by the control unit (44).

6. The digital potentiometer (42) includes a first potentiometer terminal electrically connected to the set terminal of the VFO (32), a second potentiometer terminal electrically connected to the supply voltage terminal of the VFO (32), and a data terminal configured to receive command data from the control unit (44) to selectively change the resistance of the digital potentiometer (42). The aerosol generating device (2) according to claim 5.

7. The aerosol generating device (2) according to claim 5, wherein the control unit (44) is configured to change the resistance of the digital potentiometer based on an estimated or specified impedance value of the oscillation circuit.

8. The aerosol generating device (2) according to claim 7, further comprising a voltage sensor (46) configured to provide a voltage measurement value and a current sensor (48) configured to provide a current measurement value, wherein the voltage measurement value and the current measurement value are used to estimate or specify the impedance value of the oscillation circuit.

9. The aerosol generating device (2) according to claim 8, further comprising a divider (54) configured to receive the voltage measurement value and the current measurement value provided by the voltage sensor (46) and the current sensor (48), and output to the control unit (44) an impedance value specified using the voltage measurement value and the current measurement value.

10. The aerosol generating device (2) according to claim 9, further comprising a first low-pass filter (50) connected between the voltage sensor (46) and the divider (54).

11. The aerosol generating device (2) according to claim 9, further comprising a second low-pass filter (52) connected between the current sensor (48) and the frequency divider (54).

12. The aerosol generating device (2) according to claim 1, wherein the switching circuit (34) is an inverter.

13. An aerosol generating system (1) for generating an aerosol for inhalation by a user, comprising the aerosol generating device (2) according to any one of claims 1 to 12, and an aerosol generating article (16) comprising a susceptor (20) and an aerosol generating material (18).

14. A method for controlling heating of a susceptor (20) of an aerosol generating system (1) for generating an aerosol for inhalation by a user, the aerosol generating system (1) comprising a power supply (10), an oscillation circuit (36) configured to generate a time-varying electromagnetic field for inductively heating the susceptor (20), a VFO (32), a switching circuit (34) electrically connected to the power supply (10), and a frequency generation circuit including variable resistance components (40, 42), the method including controlling the VFO (32) to provide an output signal having a frequency specified by the resistance of the variable resistance components (40, 42), and driving the oscillation circuit (36) at an operating frequency specified by the frequency of the output signal of the VFO (32).

15. The method according to claim 14, wherein the variable resistance component is a thermistor (40) having an internal resistance that changes with temperature or a digital potentiometer (42) having a selectively variable resistance.

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