Aerosol generating device and system

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] This disclosure relates, in general, to aerosol generating devices, and more particularly to aerosol generating devices for generating aerosols for inhalation by a user. Embodiments of this disclosure also relate to aerosol generating systems, which include an aerosol generating device and an aerosol generating article comprising a susceptor and an aerosol generating material.

[0002] This disclosure also relates, in general terms, to a method for controlling the heating of a susceptor in an aerosol generating system.

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

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

[0005] Such a device may supply heat to an aerosol-generating material using one of several different methods. One such method is to provide an aerosol-generating device using an induction heating system, into which an aerosol-generating article containing an aerosol-generating material can be detachably inserted by the user. In such a device, an induction coil is provided in the device, and an induction-heatable susceptor is provided in the aerosol-generating article. When the user operates the device, electrical energy is supplied to the induction coil, which in turn generates an alternating current electromagnetic field. The susceptor couples with this electromagnetic field to generate heat, which is transferred to the aerosol-generating material, for example, by conduction, and when the aerosol-generating material is heated, an aerosol is generated.

[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 usage period (also known as a vaping session). Embodiments of this disclosure aim to provide an improved user experience in which the properties of the generated aerosol are optimized by more precise control of the heat of the aerosol generating material by the susceptor. [Overview of the project] [Means for solving the problem]

[0007] According to a first aspect of this disclosure, an aerosol generating device, A power source, such as a battery or cell, An oscillator circuit configured to generate a time-varying electromagnetic field for inductive heating of a susceptor, A frequency generating circuit, A variable frequency oscillator (VFO), - A supply voltage terminal configured to receive a supply voltage, -Set terminals, - An oscillator output terminal configured to provide an output signal having a frequency determined by the input signal to the set terminal. A variable frequency oscillator (VFO) including, A switching circuit that is electrically connected to a power supply and configured to drive an oscillator circuit at an operating frequency determined by the frequency of the VFO output signal, A variable resistor component electrically connected to the VFO's set terminal, A frequency generation circuit including, An aerosol generating device including is provided.

[0008] The susceptor is an inductively heated susceptor, and may also include an aerosol-generating material, and may be part of an aerosol-generating article that is removablely 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 inductive heating of 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 A parallel RLC circuit having can be defined, for example, The filename is TIFF0007860261000001.tif16170.

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

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

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

[0013] VFO controls the frequency of the output signal f osc This is the resistance R between the supply voltage terminal and the set terminal, which is identified by the variable resistor component. set It can be directly associated with, for example, The filename is TIFF0007860261000002.tif17170, where N can be selected to be 100, 10, or 1, depending on the required frequency range.

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

[0015] The device may further include a voltage regulator, such as a low dropout regulator (LDO). The voltage regulator may include a voltage regulator output terminal that is electrically connected to a power supply and configured to provide a regulated supply voltage. The 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 supplied to other components such as a digital potentiometer and a frequency divider described below. Using the 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 during use. For example, the thermistor may be disposed adjacent to or within a part of the device, such as a heating chamber or an aerosol generating space, adapted to receive an aerosol generating article including the susceptor and the aerosol generating material. The thermistor may be attached to the surface of the heating chamber or the aerosol generating space, such as the inner sidewall or the bottom wall of the heating chamber or the aerosol generating space. The thermistor may also be disposed within the aerosol generating article and may 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 the aerosol generating material. When the temperature of the susceptor changes, the internal resistance of the thermistor located nearby 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 as the temperature rises and vice versa. The resistance of the thermistor may change linearly or non-linearly with temperature.

[0017] 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., the terminals between which the thermistor is electrically connected. Thus, 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 as a result, automatically results in a corresponding change in the operating frequency at which the switching circuit drives the oscillation circuit. In particular, the thermistor can be selected and arranged with respect to the susceptor such that a change in the temperature of the susceptor that results in a change in the resonant frequency of the parallel RLC circuit also results in a change in its internal resistance, which thus results in a corresponding change in the operating frequency generated by the frequency generation circuit. The operating frequency can thus be made to track the change in the resonant frequency of the parallel RLC circuit so that the device operates at optimal efficiency.

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

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

[0020] The control unit may be configured to receive voltage and current measurements provided by voltage and current sensors and to estimate or determine impedance values ​​using these measurements. The device may also include a frequency divider configured to receive voltage and current measurements provided by voltage and current sensors. The frequency divider may output impedance values ​​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 may be connected between the current sensor and the frequency divider.

[0021] An increase in impedance value may indicate an increase in the resonant frequency of a parallel RLC circuit, and vice versa. The control unit may include a suitable control scheme for deriving command data to selectively change the resistance of a digital potentiometer based on the change in impedance value. In particular, if the impedance value changes and indicates a change in the resonant frequency of a parallel RLC circuit, the command data will change the resistance of the digital potentiometer accordingly. Since the frequency of the VFO output signal 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 will automatically result in a corresponding change in the frequency of the VFO output signal, and consequently, 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 impedance value indicating a change in the resonant frequency of the RLC circuit as a result of a temperature change in the susceptor leads to a selected change in the resistance of the digital potentiometer, which in turn leads to a corresponding change in the operating frequency generated by the frequency generating circuit. The operating frequency can therefore be adjusted to track changes in the resonant frequency of the parallel RLC circuit so that the device operates at optimal efficiency. Such operation of the device can result in improved aerosol generation.

[0022] A second aspect of this disclosure provides an aerosol generating device, as described herein, which is configured to receive an aerosol generating article, including a susceptor and aerosol generating material, when in use.

[0023] A third aspect of the present disclosure provides an aerosol generating system for generating an aerosol for inhalation by a user, the 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 without burning it, thereby volatilizing at least one component of the aerosol generating material, and thereby generating an aerosol for inhalation by the user of the aerosol generating system.

[0025] Generally speaking, vapor is a substance that is in the gaseous phase at temperatures below its critical temperature, meaning that vapor can be condensed into a liquid by increasing the pressure without decreasing the temperature, while aerosol is fine solid particles or droplets suspended in the 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 media generated for the user to inhale.

[0026] The induction coil may include Litz wire or Litz cable. However, it will be understood that other materials may be used. The induction coil may have a substantially helical shape and may extend, for example, around the space in which the aerosol-generating article is received during use.

[0027] The circular cross-section of the helical induction coil facilitates the insertion of an aerosol generating article into a space that receives the aerosol generating device, such as an aerosol generating article, during use, and ensures uniform heating of the aerosol generating material.

[0028] Inductively heated susceptors may include, but are not limited to, one or more of the following materials: aluminum, iron, nickel, stainless steel, and their alloys, such as nickel-chromium or nickel-copper. When an electromagnetic field is applied near the susceptor, the susceptor may generate heat due to the conversion of electromagnetic energy into heat through eddy currents and magnetic hysteresis losses.

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

[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 leaves, cut fillers, porous materials, foamed materials, or sheets. The aerosol-generating material may include plant-derived materials, particularly tobacco. When heated by a susceptor, the aerosol-generating material may release volatile compounds. These volatile compounds may include nicotine or flavoring compounds such as tobacco flavorings.

[0031] The foaming material may contain multiple fine particles (e.g., tobacco particles) and may also contain a certain amount of water and / or moisture additives such as humectants. The foaming material may be porous and may allow air and / or vapor to flow through it.

[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 contain an aerosol-forming agent content of about 5% to about 50% by dry weight. In some embodiments, the aerosol generating material may contain an aerosol-forming agent content of about 10% to about 20%, and possibly about 15%, by dry weight.

[0033] An aerosol generating article may include a breathable shell containing an aerosol generating material. The breathable shell may include an electrically insulating, non-magnetic breathable material. This material may have high breathability and resistance to high temperatures, allowing air to flow through it. 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 has appropriate perforations or openings to allow air to flow. The aerosol generating article may be formed in a substantially stick shape and may generally resemble a cigarette having a tubular region in which the aerosol generating material is arranged in a suitable form. The aerosol generating article may include a filter segment at its proximal end, the filter segment may include, for example, cellulose acetate fibers. The filter segment may constitute a mouthpiece filter and may be aligned coaxially with the aerosol generating material. Some designs may also include one or more vapor collection regions, cooling regions, and other structures. For example, an aerosol-generating article may include at least one tubular segment upstream of the filter segment. The tubular segment may act as a vapor cooling region. The vapor cooling region 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 the user, for example, through the filter segment.

[0034] A fourth aspect of this disclosure relates to a method for controlling the heating of a susceptor of an aerosol generating system for generating an aerosol for user inhalation, wherein the system is Power supply and An oscillator circuit configured to generate a time-varying electromagnetic field for inductive heating of a susceptor, The frequency generation circuit includes a VFO, a switching circuit electrically connected to a power supply, and a variable resistor component. The method provided includes controlling a VFO to provide an output signal having a frequency determined by the resistance of a variable resistor component, and driving an oscillator circuit at an operating frequency determined by the frequency of the VFO's output signal.

[0035] As described above, the variable resistor component may be a thermistor having an internal resistance that changes with temperature, or a digital potentiometer having a resistance that is selectively changed by, for example, a control unit. [Brief explanation of the drawing]

[0036] [Figure 1] This is a schematic diagram of an example of an aerosol generation system. [Figure 2] Figure 1 is a schematic diagram of a first example of a controller for an aerosol generation system. [Figure 3] Figure 1 is a schematic diagram of a second example of the controller for the aerosol generation system. [Modes for carrying out the invention]

[0037] Herein, embodiments of the present disclosure will be described, merely as examples and with reference to the attached drawings.

[0038] Referring first 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 which has a proximal end 4 and a distal end 6 and may be configured to operate at a high frequency, and includes a power supply 10 and a controller 12. The power supply 10 typically includes one or more batteries, which may be inductively charged, for example. The controller 12 typically includes one or more microcontroller units (MCUs) or microprocessor units (MPUs).

[0039] The aerosol generating device 2 is substantially cylindrical and includes a substantially cylindrical aerosol generating space 14 at its proximal end 4, for example, in the form of a heating chamber or compartment. The cylindrical aerosol generating space 14 is arranged to receive a substantially cylindrical aerosol generating article 16 of a corresponding shape, which contains an aerosol generating material 18 and one or more induction-heatable susceptors 20. The aerosol generating article 16 typically includes a non-metallic cylindrical outer shell 16a and permeable 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 generating device 2 includes a spiral induction coil 22 having a circular cross-section and extending around a cylindrical aerosol generating space 14. The induction coil 22 can be energized by a power supply 10 and a controller 12. As will be described in more detail below, the controller 12 includes, among other electronic components, a switching circuit (e.g., an inverter) arranged to convert a DC current from the power supply 10 into an AC high-frequency current for the induction coil 22.

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

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

[0043] The induction-heatable susceptor 20 may come into direct or indirect contact with the aerosol-generating material 18 so that when the susceptor is induction-heated by the induction coil 22, heat is transferred from the susceptor to the aerosol-generating material, heating the aerosol-generating material and thereby generating an aerosol. The susceptor 20 may have any suitable shape and configuration, e.g., planar shape, particle shape, or a combination thereof. Aerosolization of the aerosol-generating material 18 is facilitated by adding air from the ambient environment through the air inlet 24. The aerosol generated by heating the aerosol-generating material 18 exits the aerosol-generating space 14 through the air outlet 28, where it can be inhaled by the user of device 2. The airflow through the aerosol-generating space 14, i.e., the airflow from the air inlet 24 through the aerosol-generating space to the air outlet 28, may be assisted by the negative pressure generated when the user inhales air from the air outlet side of device 2.

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

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

[0046] The controller 12A includes an integrated circuit (IC) variable frequency oscillator (VFO) 32. The VFO may be implemented using, for example, the LTC® 1799 from Analog Devices, One Analog Way, Wilmington, MA01887, United States of America. The LTC® 1799 is a precision oscillator having an oscillator frequency selected by an external resistor. The VFO 32 includes a supply voltage terminal (labeled "V+") electrically connected to the output terminal of the VFO 30 and configured to receive a regulated supply voltage (e.g., 2.7 to 5.5V). The VFO 32 includes an external resistor (R) between the supply voltage terminal and the set terminal. set It includes a set terminal (labeled "SET") and an oscillator output terminal (labeled "OUT") for supplying an output signal (e.g., a square wave signal) having a frequency specified by ). In particular, the oscillator frequency f osc It is determined by the following formula: TIFF0007860261000003.tif14170 Here, N may be selected to be 100, 10, or 1, depending on the required frequency range. In practice, this can be done by electrically connecting the split terminal of the VFO (not shown) to one of the regulated supply voltage, open-circuit voltage, and ground. The oscillator frequency may be in the range of 1 kHz to 33 MHz.

[0047] From the above equation, the external resistor R set If it increases, the oscillator frequency f osc It can be seen that the decrease is also true, and vice versa.

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

[0049] The switching circuit 34 is electrically connected to the power supply 10 and is configured to drive the oscillation circuit 36 at an operating frequency specified by the oscillator frequency. The oscillation circuit 36 includes a capacitor 38 and an inductor coil 22. The parallel RLC circuit includes the capacitor 38, the inductor 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 determines the external resistance R set . As a result, when the internal resistance of the thermistor 40 changes, the oscillator frequency f osc automatically changes, and thus the frequency at which the oscillation circuit 36 is driven by the switching circuit 34 changes. The thermistor 40 can be disposed, for example, adjacent to or within the aerosol generating space 14 shown in FIG. 1, where it undergoes temperature changes similar to those received by the susceptor 20 during operation of the aerosol generating system 1, particularly during heating of the aerosol generating material 18. When 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 in response to an increase in temperature and vice versa. When the resonant frequency of the parallel RLC circuit increases due to an increase in the temperature of the susceptor 22, the internal resistance of the thermistor 40 decreases. Accordingly, the external resistance R set electrically connected between the supply voltage terminal and the set terminal of the VFO 32 also decreases, and the oscillator frequency f osc increases. On the other hand, when the resonant frequency of the parallel RLC circuit decreases due to a decrease in the temperature of the susceptor 22, the internal resistance of the thermistor 40 increases. Accordingly, the external resistance R set electrically connected between the supply voltage terminal and the set terminal of the VFO 32 also increases, and the oscillator frequency f oscThe oscillator frequency decreases. 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 such that the change in oscillator frequency fosc as a result of the change in its internal resistance approximately matches the change in the resonant frequency of the parallel RLC circuit, that is, the oscillator frequency and the resonant frequency remain approximately the same even if the temperature of the susceptor 20 changes.

[0051] Figure 3 shows an alternative controller 12B with similar components bearing the same reference numerals. In the second controller 12B, the 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 using, for example, the MCP483X from Microchip Technology Inc., 2355 West Chandler Blvd., Chandler, Arizona, United States of America. The MCP483X device is I 2 This is a single-channel volatile 7-bit (129 wiper steps) digital potentiometer with a C-compatible interface. The 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. The digital potentiometer 42 includes a first potentiometer terminal (labeled "P0A") electrically connected to the 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] The digital potentiometer 42 includes a grounding terminal (labeled "VSS") which is electrically connected to ground.

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

[0054] MCU44 is I 2 Command data is provided to the digital potentiometer 42 using the C protocol. The command data selectively changes the resistance of the digital potentiometer 42, and therefore the R applied to the VFO 32. set The value of is selectively changed. The MCU44 also provides clock data. The communication protocol is I 2 It is not limited to C; other suitable serial protocols (e.g., SPI or UART) or parallel protocols may be used instead.

[0055] The MCU44 can generate command data to increase or decrease the resistance of the digital potentiometer 42 using an appropriate control scheme. The MCU44 selectively changes the resistance of the digital potentiometer 42 based on the estimated or identified impedance value of the parallel RLC circuit, which indicates a change in the 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 can be used for high-speed protection monitoring, for example, to prevent overheating of aerosol-generating materials. The first low-pass filter 50 and the second low-pass filter 52 can output filtered (or averaged) voltage and current measurements, thereby simplifying the impedance calculation of the oscillator circuit.

[0057] The filtered voltage and current measurements are provided to a frequency divider (or frequency 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 filtered current measurements from the current sensor 48. The fourth input terminal is electrically connected to a first low-pass filter 50 and receives filtered voltage measurements from the voltage sensor 46. The frequency divider 54 uses the filtered voltage and current measurements to estimate or determine the impedance value of the parallel RLC circuit. In particular, the output signal indicating the impedance value is determined by the following formula: TIFF0007860261000004.tif15170

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

[0059] Output signal and trim signal (V) from the output terminal of frequency divider 54 trim The signal is supplied to the operational amplifier 56. The output signal from the operational amplifier 56 is supplied to the MCU 44. The output signal from the frequency divider 54 corresponds to the background value of the calculated impedance value. The resolution of the impedance value can be improved by trimming the background value and amplifying the remaining impedance value.

[0060] An increase in the impedance value of a parallel RLC circuit usually indicates an increase in the resonant frequency, and vice versa. The MCU44 uses an appropriate control scheme to determine whether the output signal from the operational amplifier 54 indicates an increase or decrease in the resonant frequency of the parallel RLC circuit. If the MCU44 determines that the resonant frequency is increasing, it controls the digital potentiometer 42 to decrease its resistance by the appropriate amount. Thus, the external resistor R set The oscillator frequency f decreases. osc The external resistance R increases. On the other hand, if the MCU44 determines that the resonant frequency is decreasing, it controls the digital potentiometer 42 to increase its resistance by an appropriate amount. Therefore, the external resistance R set As the oscillator frequency f increases, osc The frequency decreases. By changing the resistance of the digital potentiometer 42, the MCU 44 can make the oscillator frequency follow the resonant frequency of the parallel RLC circuit. The digital potentiometer 42 reduces the oscillator frequency f as a result of the change in its resistance. osc The change in the oscillator frequency can be controlled to approximately coincide with the change in the resonant frequency of the parallel RLC circuit, that is, the oscillator frequency and the resonant frequency can remain approximately the same even if the temperature of the susceptor 20 changes.

[0061] While exemplary embodiments have been described in the preceding paragraphs, it should be understood that various modifications to these embodiments can be made without departing from the scope of the attached claims. Therefore, 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] Unless otherwise stated herein or unless clearly inconsistent with the context, any combination of any possible variations thereof of the features described above is encompassed by this disclosure.

[0063] Unless the context clearly indicates otherwise, throughout this specification and the claims, words such as “includes,” “contains,” and “includes” should be interpreted in an inclusive sense, i.e., “includes, but not limited,” rather than in an exclusive or exhaustive sense.

Claims

1. Aerosol generating device (2), Power supply (10), An oscillator circuit (36) configured to generate a time-varying electromagnetic field for inductively heating the susceptor (20), A frequency generating circuit, A variable frequency oscillator VFO (32), - A supply voltage terminal configured to receive the supply voltage, - Set terminals, - An oscillator output terminal configured to provide an output signal having a frequency determined by the input signal to the set terminal. A variable frequency oscillator VFO (32) including, A switching circuit (34) is 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 resistor component (40, 42) is electrically connected to the set terminal of the VFO (32), A frequency generation circuit including, an aerosol generating device (2) including the above.

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

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

4. The aerosol generating device (2) according to claim 3, further comprising a heating chamber or aerosol generating space (14), wherein the thermistor (40) is mounted on the surface of the heating chamber or aerosol generating space (14).

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

6. The aerosol generating device (2) according to claim 5, wherein 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) in order to selectively change the resistance of the digital potentiometer (42).

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 identified 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 and a current sensor (48) configured to provide a current measurement, wherein the voltage measurement and the current measurement are used to estimate or determine the impedance value of the oscillation circuit.

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

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 frequency 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 an aerosol generating device (2) according to any one of claims 1 to 12, and an aerosol generating article (16) including a susceptor (20) and an aerosol generating material (18).

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

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

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