Aerosol-generating device and system

Abstract

An aerosol-generating device comprises a power source (10) and an oscillating circuit (36) configured to generate a time-varying electromagnetic field for inductively heating a susceptor (20). A frequency generation circuit of a controller (12A) includes a variable frequency oscillator VFO (32) including a supply voltage terminal configured to receive a regulated supply voltage, a setting terminal, and an oscillator output terminal configured to provide an output signal, the output signal has a frequency determined by a resistance between the supply voltage terminal and the set terminal. The frequency generating circuit further comprises a switching circuit (34) electrically connected to the power supply (10) and configured to drive the oscillating 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 a power supply voltage terminal and a setting terminal of the VFO (32).

Description

Technical Field

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

[0003] The present disclosure is particularly applicable to portable (handheld) aerosol generating devices. Such devices heat, rather than burn, an aerosol generating material or substrate (e.g., tobacco or other suitable material) by conduction, convection and / or radiation to generate an aerosol for inhalation by a user. The present disclosure is particularly related to induction heated aerosol generating devices. Background Art

[0004] In recent years, devices that generate an aerosol for inhalation by heating rather than burning an aerosol-generating material have become increasingly popular with consumers. A commonly used risk reduction or risk modification device is a heated material aerosol-generating device or a so-called heat-not-burn device. This type of device generates an aerosol or vapour by heating an aerosol-generating material to a temperature typically in the range of 150°C to 300°C. Heating the aerosol-generating material to a temperature within this range without burning or combusting the aerosol-generating material generates a vapour which typically cools and condenses to form an aerosol for inhalation by a user of the device.

[0005] Such a device may use one of a number of different methods to provide heat to the aerosol generating material. One method is to provide an aerosol generating device that uses an induction heating system into which an aerosol generating article including an aerosol generating material can be removably inserted by a user. In such a device, an induction coil is provided for the device, and an inductively heatable susceptor is provided for the aerosol generating article. When the 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 and generates heat, which is transferred to the aerosol generating material, for example by conduction, and an aerosol is generated when the aerosol generating material is heated.

[0006] It is generally desirable to control the heating 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 smoking 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 heating of the aerosol-generating material by a receptor. Summary of the invention

[0007] According to a first aspect of the present disclosure, there is provided an aerosol generating device, the aerosol generating device comprising:

[0008] A power source, such as a battery or battery cells;

[0009] an oscillating circuit configured to generate a time-varying electromagnetic field for inductively heating the susceptor; and

[0010] A frequency generating circuit, the frequency generating circuit comprising:

[0011] A variable frequency oscillator (VFO), the variable frequency oscillator comprising:

[0012] - a supply voltage terminal configured to receive a supply voltage;

[0013] - Setting terminals; and

[0014] - an oscillator output terminal configured to provide an output signal having a frequency determined by an input signal entering the set terminal;

[0015] a switching circuit electrically connected to a power source and configured to drive the oscillation circuit at an operating frequency determined by a frequency of an output signal of the VFO; and

[0016] A variable resistance component is electrically connected to a setting terminal of the VFO.

[0017] The susceptor is an inductively heatable susceptor and may be a part of an aerosol-generating article which also includes the aerosol-generating material and is removably insertable into the device.

[0018] The oscillating 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 the oscillating circuit may define a parallel RLC circuit with a resonant frequency f o Depends on the values ​​of resistance R, capacitance C, and inductance L, for example, where:

[0019]

[0020] The resistance R of the parallel RLC circuit depends on the precise positioning of the receptor relative to the induction coil and the resistance of the receptor that varies with temperature. This means that the resonant frequency of the parallel RLC circuit will change as the temperature of the receptor changes during the inhalation process. For the most efficient heating, the oscillation circuit is preferably driven at an operating frequency that substantially matches the resonant frequency. Providing more efficient heating can improve aerosol generation. Therefore, the device according to the present disclosure is intended to adjust the operating frequency to match the change in the resonant frequency of the parallel RLC circuit, thereby providing improved heating and a better user experience. The device uses a frequency generating circuit that is simple in design, rugged and cost-effective to implement. This in turn allows the aerosol generating device to be more compact, efficient and lightweight.

[0021] The VFO may be, for example, an integrated circuit (IC) device.

[0022] The input signal provided to the setting terminal of the VFO may be a resistance between the power supply voltage terminal and the setting terminal. The frequency of the output signal of the VFO may be determined by the resistance between the power supply voltage terminal and the setting terminal. The variable resistance component may be electrically connected between the power supply voltage terminal and the setting terminal of the VFO.

[0023] VFO can directly output the frequency f ose The resistance R between the power supply voltage terminal and the setting terminal is determined by the variable resistance component set associated, for example, where:

[0024]

[0025] And wherein, N can be selected as 100, 10 or 1 according to the required frequency range.

[0026] The switching circuit may include, for example, one or more semiconductor switches that are controlled to switch at an operating frequency determined by a selectable frequency of the VFO output signal. The switching circuit drives the oscillating circuit at the operating frequency to generate an alternating electromagnetic field of the same frequency for heating the susceptor. The switching circuit may be configured to operate at a frequency between about 80kHz and 500kHz, possibly between about 150kHz and 250kHz, and possibly about 200kHz. Depending on the type of inductively heatable susceptor used, the switching circuit may be configured to operate at a higher frequency, such as a frequency in the MHz range. The frequency range of the output signal of the VFO may be selected accordingly. The switching circuit may be an inverter.

[0027] The device may further include a regulator (e.g., a low dropout regulator (LDO)). The regulator may be electrically connected to a power supply and include a regulator output terminal configured to provide a regulated supply voltage. The supply voltage terminal of the VFO may be electrically connected to the regulator output terminal so 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 voltage divider described below. Using the regulated supply voltage may provide stable operation of the frequency generation circuit and other components.

[0028] In one embodiment, the variable resistance component can be a thermistor whose internal resistance varies with temperature. When in use, the thermistor can be placed near the susceptor and / or the aerosol generating material. For example, the thermistor can be arranged adjacent to or inside a part of the device (such as a heating chamber or an aerosol generating space), which is suitable for receiving an aerosol generating article including a susceptor and an aerosol generating material. For example, the thermistor can be installed on the surface of the heating chamber or the aerosol generating space, such as the inner side wall or bottom wall of the heating chamber or the aerosol generating space. The thermistor can also be arranged in the aerosol generating article and electrically contact the VFO when the article is inserted into the device. The thermistor can directly contact the susceptor or the aerosol generating material. When the temperature of the susceptor changes, the internal resistance of the thermistor located nearby will change accordingly. The thermistor is selected so that its internal resistance changes appropriately according to the temperature. In one embodiment, for example, the thermistor can have a negative temperature coefficient (NTC), and its resistance decreases as the temperature increases, and vice versa. The resistance of a thermistor can vary linearly or nonlinearly with temperature.

[0029] Because 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 terminal to which the thermistor is electrically connected), this means that any change in the internal resistance of the thermistor will automatically cause a corresponding change in the frequency of the output signal of the VFO, and in turn cause a corresponding change in the operating frequency of the oscillating circuit driven by the switching circuit. In particular, the thermistor can be selected and placed relative to the susceptor so that changes in the temperature of the susceptor (which will cause changes in the resonant frequency of the parallel RLC circuit) also cause changes in the internal resistance of the thermistor, which in turn causes corresponding changes in the operating frequency generated by the frequency generating circuit. Thus, the operating frequency can be made to track changes in the resonant frequency of the parallel RLC circuit, so that the device operates at optimal efficiency.

[0030] The apparatus may further comprise a control unit or processor (eg a microcontroller unit or a microprocessor unit).

[0031] The variable resistance component may be a digital potentiometer having a resistance that is selectively changed by a control unit. The digital potentiometer may include: a first potentiometer terminal electrically connected to a setting terminal of the VFO; a second potentiometer terminal electrically connected to a power supply voltage terminal of the VFO; and at least one data terminal configured to receive command data from a control unit for selectively changing the resistance of the digital potentiometer. The control unit may be configured to change the resistance of the digital potentiometer based on an estimated or determined impedance value of a parallel RLC circuit. In particular, the device may further include a voltage sensor configured to provide a voltage measurement result and a current sensor configured to provide a current measurement result. The voltage measurement result and the current measurement result may be used to estimate or determine the impedance value. In these embodiments, the control unit may control the digital potentiometer so that the frequency of the output signal of the VFO changes in response to a change in the resonant frequency of the oscillation circuit.

[0032] The control unit may be configured to receive voltage measurements and current measurements provided by the voltage and current sensors, and use the voltage measurements and current measurements to estimate or determine the impedance value. The device may also include a voltage divider configured to receive voltage measurements and current measurements provided by the voltage and current sensors. The voltage divider may output the impedance value estimated or determined using the voltage measurements and current measurements to the control unit. A first low-pass filter may be connected between the voltage sensor and the voltage divider. A second low-pass filter is connected between the current sensor and the voltage divider.

[0033] 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 an appropriate control scheme that derives command data based on the change in the impedance value for selectively changing the resistance of the digital potentiometer. In particular, if the impedance value changes, indicating a change in the resonant frequency of the parallel RLC circuit, the command data will change the resistance of the digital potentiometer accordingly. Because 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 terminal to which the digital potentiometer is electrically connected), this means that any change in the resistance of the digital potentiometer will automatically cause a corresponding change in the frequency of the VFO output signal, and in turn cause a corresponding change in the operating frequency of the switching circuit driving the oscillating circuit. In particular, the control scheme of the control unit may be selected so that a change in the impedance value that changes due to a change in the temperature of the receptor and indicates a change in the resonant frequency of the RLC circuit causes a change in the selected resistance of the digital potentiometer, which in turn causes a corresponding change in the operating frequency generated by the frequency generating circuit. Therefore, the operating frequency can be made to track the change in the resonant frequency of the parallel RLC circuit, so that the device operates at optimal efficiency. Such operation of the device makes it possible to improve aerosol generation.

[0034] According to a second aspect of the present disclosure, there is provided an aerosol-generating device as described herein, configured, in use, to receive an aerosol-generating article comprising a susceptor and an aerosol-generating material.

[0035] According to a third aspect of the present disclosure, there is provided 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.

[0036] The aerosol generating system is adapted to heat the aerosol generating material, without burning the aerosol generating material, to volatilize at least one component in the aerosol generating material and thereby generate an aerosol for inhalation by a user of the aerosol generating system.

[0037] Generally speaking, a vapor is a substance that is in the gaseous phase at a temperature below its critical temperature, which means that the vapor can be condensed into a liquid by increasing its pressure without lowering the temperature, while an aerosol is a suspension of fine solid particles or liquid droplets in the air or another gas. However, it should be noted that the terms 'aerosol' and 'vapor' are used interchangeably in this specification, particularly with respect to the form of the inhalable medium produced for inhalation by the user.

[0038] The induction coil may comprise Litz wire or Litz cable. However, it will be appreciated that other materials may be used. The induction coil may be substantially helical in shape and may, for example, extend around a space that receives the aerosol-generating article in use.

[0039] The circular cross-section of the spiral induction coil may facilitate insertion of the aerosol-generating article into an aerosol-generating device, for example into a space that receives the aerosol-generating article in use, and may ensure uniform heating of the aerosol-generating material.

[0040] The inductively heatable susceptor may include, but is not limited to, one or more of aluminum, iron, nickel, stainless steel, and alloys thereof (e.g., nickel-chromium or nickel-copper alloys). By applying an electromagnetic field in the vicinity thereof, the susceptor may generate heat due to eddy currents and hysteresis losses, thereby causing conversion of electromagnetic energy into thermal energy.

[0041] The induction coil may be arranged to operate, in use, with a fluctuating electromagnetic field having a magnetic flux density of between about 20 mT and about 2.0 T at a point of highest concentration.

[0042] Aerosol generating material can be any type of solid or semi-solid material. Exemplary types of aerosol generating solids include powders, microparticles, pellets, fragments, strands, granules, gels, strips, loose leaves, shredded fillers, porous materials, foam materials or sheets. Aerosol generating materials can include plant-derived materials, and can particularly include tobacco. When heated by a receptor, aerosol generating materials can release volatile compounds. These volatile compounds can include nicotine or flavor compounds such as tobacco flavors.

[0043] The foam material may include a plurality of fine particles (eg, tobacco particles), and may also include a volume of water and / or a moisture additive (eg, a humectant). The foam material may be porous, and may allow air and / or vapor to flow through the foam material.

[0044] The aerosol generating material may include an aerosol former. Examples of aerosol formers include polyols and mixtures thereof, such as glycerol or propylene glycol. Typically, the aerosol generating material may include an aerosol former content of between about 5% and about 50% on a dry weight basis. In some embodiments, the aerosol generating material may include an aerosol former content of between about 10% and about 20% on a dry weight basis, and may be about 15% on a dry weight basis.

[0045] The aerosol generating article may include a permeable shell containing an aerosol generating material. The permeable shell may include an electrically insulating and non-magnetic permeable material. The material may have high permeability to allow air to flow through a material having high temperature resistance. Examples of suitable permeable materials include cellulose fibers, paper, cotton, and silk. The permeable material may also be used as a filter. Alternatively, the aerosol generating article may include an aerosol generating substance wrapped in paper. Alternatively, an aerosol generating material may be included inside the material, which is airtight but includes appropriate perforations or openings to allow air to flow. The aerosol generating material may be substantially formed into a rod shape and may be broadly similar to a cigarette having a tubular region with an aerosol generating material arranged in a suitable manner. The aerosol generating article may include a filter segment at the proximal end of the aerosol generating article, for example, the filter segment includes cellulose acetate fibers. The filter segment may constitute a mouthpiece filter and may be coaxially aligned with the aerosol generating material. In some designs, one or more vapor collection areas, cooling areas, and other structures may also be included. For example, the 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 the 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 (e.g., through the filter segment).

[0046] According to a fourth aspect of the present disclosure, there is provided a method for controlling heating of a susceptor of an aerosol generating system for generating an aerosol for inhalation by a user, the system comprising:

[0047] power supply;

[0048] an oscillating circuit configured to generate a time-varying electromagnetic field for inductively heating the susceptor; and

[0049] a frequency generating circuit including a VFO, a switching circuit electrically connected to a power source, and a variable resistance component;

[0050] The method includes controlling a VFO to provide an output signal having a frequency determined by a resistance of a variable resistance component, and driving an oscillation circuit at an operating frequency determined by the frequency of the output signal of the VFO.

[0051] As described above, the variable resistance component may be a thermistor having an internal resistance that varies with temperature or a digital potentiometer having a resistance that is selectively varied by, for example, a control unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 is a diagrammatic view of an example of an aerosol generating system;

[0053] Figure 2 yes Figure 1 a schematic diagram of a first example of a controller for an aerosol generating system; and

[0054] Figure 3 yes Figure 1 Schematic diagram of a second example of a controller of an aerosol generating system. DETAILED DESCRIPTION

[0055] Embodiments of the present disclosure will now be described, by way of example only, and with reference to the accompanying drawings.

[0056] First reference Figure 1 , diagrammatically shows an example of an aerosol generating system 1. The aerosol generating system 1 comprises an aerosol generating device 2 and an aerosol generating article 16. The aerosol generating device 2 has a proximal end 4 and a distal end 6, and comprises a device body 8, the device body comprising a power source 10 and a controller 12, which can be configured to operate at high frequencies. The power source 10 typically comprises one or more batteries capable of inductive recharging, for example. The controller 12 typically comprises one or more microcontroller units (MCU) or microprocessor units (MPU).

[0057] The aerosol generating device 2 is generally cylindrical and comprises a generally cylindrical aerosol generating space 14 (e.g. in the form of a heating chamber or compartment) at the proximal end 4 of the aerosol generating device 2. The cylindrical aerosol generating 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 comprises a cylindrical non-metallic housing 16a and an air permeable layer or membrane 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, which can, for example, contain tobacco as the aerosol generating material 18.

[0058] 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 described in more detail below, the controller 12 includes, among other electronic components, a switching circuit (e.g., an inverter) that is arranged to convert a direct current from the power supply 10 into an alternating high-frequency current for the induction coil 22.

[0059] The aerosol generating device 2 comprises 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 comprises a mouthpiece 26 having an air outlet 28. The mouthpiece 26 is removably mounted at the proximal end 4 of the device body 8 to allow access to the aerosol generating space 14 for inserting or removing the aerosol generating article 16.

[0060] It will be appreciated by those skilled in the art that when the induction coil 22 is energized during use of the aerosol generating system 1, an alternating and time-varying electromagnetic field is generated. The electromagnetic field couples with one or more inductively heatable susceptors 20 and generates eddy currents and / or hysteresis losses in the one or more inductively heatable susceptors, causing these susceptors to heat up. 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.

[0061] The inductively heatable susceptor 20 can be in direct or indirect contact with the aerosol generating material 18, so 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 and thereby generate an aerosol. The susceptor 20 can have any suitable shape and configuration (e.g., a planar shape, a particle shape, or a combination thereof). Adding air from the surrounding environment through the air inlet 24 facilitates the aerosolization of the aerosol generating material 18. The aerosol generated by heating the aerosol generating material 18 leaves the aerosol generating space 14 through the air outlet 28, and the user of the device 2 can inhale the aerosol at the air outlet. The negative pressure generated by the user sucking air from the air outlet side of the device 2 can help air flow through the aerosol generating space 14 (i.e., flow from the air inlet 24 through the aerosol generating space and flow out from the air outlet 28).

[0062] The induction coil 22 forms part of an oscillating circuit. The oscillating circuit also includes a capacitor. The 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 due to changes in the temperature of the susceptor 20.

[0063] Figure 2 A first example of a controller 12A is shown in FIG. 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 power supply. A ground terminal (labeled “GND”) is electrically connected to ground.

[0064] The controller 12A includes an integrated circuit (IC) variable frequency oscillator (VFO) 32. The VFO may be a 32-bit analog oscillator such as the Analog Devices 32. 1799, and is located at One Analog Way, Wilmington, MA 01887, USA. 1799 is a precision oscillator whose oscillator frequency is selected by an external resistor. VFO 32 includes a power supply voltage terminal (labeled as "V+"), which is electrically connected to the output terminal of VDO 30 and is configured to receive a regulated power supply voltage (e.g., 2.7V to 5.5V). VFO 32 also includes a setting terminal (labeled as "SET") and an oscillator output terminal (labeled as "OUT") for providing an output signal (e.g., a square wave signal), the frequency of which is determined by an external resistor (R) between the power supply voltage terminal and the setting terminal. set ) is determined. In particular, the oscillator frequency fosc It is determined by:

[0065]

[0066] Wherein, N can be selected to be 100, 10 or 1, depending on the required frequency range. In practice, this can be accomplished by electrically connecting the voltage divider terminal (not shown) of the VFO to one of a regulated power supply voltage, an open circuit voltage, and ground. The oscillator frequency can be in the range of 1 kHz to 33 MHz.

[0067] It can be concluded from the above equation that if the external resistance R set Increase, oscillator frequency f osc will decrease and vice versa.

[0068] VFO 32 also includes a ground terminal (labeled “GND”) that is electrically connected to ground.

[0069] The switching circuit 34 is electrically connected to the power source 10 and is configured to drive the oscillating circuit 36 ​​at an operating frequency determined by the oscillator frequency. The oscillating circuit 36 ​​includes a capacitor 38 and an induction coil 22. The parallel RLC circuit includes the capacitor 38, the induction coil 22, and one or more inductively heatable susceptors 20, which are part of the aerosol generating article 16.

[0070] exist Figure 2 In the first controller 12A shown, the thermistor 40 is electrically connected between the power supply voltage terminal and the setting terminal of the VFO 32. The internal resistance of the thermistor 40 varies with temperature and determines the external resistance R set Therefore, any change in the internal resistance of thermistor 40 will automatically cause the oscillator frequency f osc The change of the temperature of the oscillating circuit 36 ​​driven by the switching circuit 34 causes the change of the frequency. For example, the thermistor 40 can be arranged with Figure 1 The aerosol generating space 14 is shown adjacent to or within it, where the thermistor will experience similar temperature changes as the susceptor 20 during operation of the aerosol generating system 1, in particular during heating of the aerosol generating material 18. As the temperature of the susceptor changes, the internal resistance of the thermistor 40 will change accordingly. The thermistor 40 is selected so that its internal resistance decreases in response to an increase in temperature, and vice versa. If 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 will decrease. The external resistance R between the supply voltage terminal and the set terminal electrically connected to the VFO 32 is set will also decrease, and the oscillator frequency f oscOn the other hand, if the resonant frequency of the parallel RLC circuit decreases due to the decrease in the temperature of the susceptor 22, the internal resistance of the thermistor 40 will increase. The external resistance R between the power supply voltage terminal and the setting terminal electrically connected to the VFO 32 set will also increase, and the oscillator frequency f osc will decrease. Therefore, the oscillator frequency can track the resonant frequency of the parallel RLC circuit without any additional sensor. The thermistor 40 can be selected so that the oscillator frequency f caused by the change in its internal resistance osc The change in is substantially matched to the change in the resonant frequency of the parallel RLC circuit, ie, so that even when the temperature of the susceptor 20 changes, the oscillator frequency and the resonant frequency remain substantially matched.

[0071] Figure 3 An alternative controller 12B is shown, wherein like components have like 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 using, for example, an MCP483X from Microchip Technology Inc., 2355 West Chandler Blvd., Chandler, Arizona, USA. The MCP483X device is a single channel, volatile, 7-bit (129 sliding steps) digital potentiometer having an I 2 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 also 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 VFO. The set terminal of VFO 32 may alternatively be electrically connected to a third potentiometer (or wiper) terminal (labeled “P0W”).

[0072] The digital potentiometer 42 includes a ground terminal (labeled “VSS”) that is electrically connected to ground.

[0073] The digital potentiometer 42 includes a serial data terminal (labeled “SDA”) and a serial clock terminal (labeled “SCL”).

[0074] MCU 44 uses I 2 The C protocol provides command data to the digital potentiometer 42. The command data selectively changes the resistance of the digital potentiometer 42 and, therefore, changes the R applied to the VFO 32. setThe MCU 44 also provides clock data. The communication protocol is not limited to I 2 C and other suitable serial protocols (eg, SPI or UART) or parallel protocols may also be used.

[0075] The MCU 44 may use an appropriate control scheme to generate command data for increasing or decreasing the resistance of the digital potentiometer 42. The MCU 44 selectively changes the resistance of the digital potentiometer 42 based on an estimated or determined impedance value of the parallel RLC circuit, which is indicative of a change in the resonant frequency.

[0076] The controller 12B includes a voltage sensor 46 and a current sensor 48, which provide voltage and current measurements, respectively. The voltage measurement is provided to a first low-pass filter 50 and the current measurement is 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 example, for high-speed protection monitoring to prevent overheating of the aerosol generating material. The first low-pass filter 50 and the second low-pass filter 52 can output filtered (or averaged) voltage and current measurements, which can simplify the impedance calculation of the oscillating circuit.

[0077] The filtered voltage measurement and current measurement are provided to a voltage divider (or multiplier / divider) 54. The voltage 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 input terminal and the third input terminal are electrically connected to ground. The first input terminal is electrically connected to the second low-pass filter 52 and receives the filtered current measurement from the current sensor 48. The fourth input terminal is electrically connected to the first low-pass filter 50 and receives the filtered voltage measurement from the voltage sensor 46. The voltage divider 54 uses the filtered voltage and current measurements to estimate or determine the impedance value of the parallel RLC circuit. More specifically, the output signal indicating the impedance value is determined by:

[0078]

[0079] The voltage divider 54 can calculate the impedance value of the oscillation circuit 36 ​​instead of the MCU 44. This makes it possible to calculate the impedance value more quickly.

[0080] The output signal from the output terminal of the voltage divider 54 and the trimming signal (V trim) is provided to the operational amplifier 56. The output signal from the operational amplifier 56 is provided to the MCU 44. The output signal from the voltage divider 54 corresponds to the background value of the calculated impedance value. By fine-tuning the background value and amplifying the remaining impedance value, the resolution of the impedance value can be improved.

[0081] An increase in the impedance value of the parallel RLC circuit generally indicates an increase in the resonant frequency, and vice versa. The MCU 44 uses an appropriate control scheme to determine 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, the MCU will control the digital potentiometer 42 to reduce its resistance by an appropriate amount. The external resistance R set will therefore decrease and the oscillator frequency f ose On the other hand, if the MCU 44 determines that the resonant frequency is decreasing, the MCU will control the digital potentiometer 42 to increase its resistance by an appropriate amount. set will therefore increase and the oscillator frequency f osc By changing 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 can be controlled so that the oscillator frequency f caused by the change in its resistance osc The change in is substantially matched to the change in the resonant frequency of the parallel RLC circuit, ie, so that even when the temperature of the susceptor 20 changes, the oscillator frequency and the resonant frequency remain substantially matched.

[0082] Although exemplary embodiments have been described in the preceding paragraphs, it should be understood that various modifications may be made to these embodiments without departing from the scope of the appended 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.

[0083] Unless otherwise indicated herein or clearly contradicted by context, this disclosure encompasses any combination of the above-described features in all possible variations thereof.

[0084] Unless the context clearly requires otherwise, throughout the specification and claims, the words "comprise," "comprising," and the like are to be interpreted in an inclusive rather than an exclusive or exhaustive sense; that is, in the sense of "including but not limited to."

Claims

1. An aerosol generating device (2), comprising: Power supply (10); an oscillating circuit (36) configured to generate a time-varying electromagnetic field for inductively heating the susceptor (20); as well as A frequency generating circuit, the frequency generating circuit comprising: A variable frequency oscillator VFO (32), the variable frequency oscillator comprising: - a supply voltage terminal configured to receive a supply voltage; - Setting terminals; and - an oscillator output terminal configured to provide an output signal having a frequency determined by an input signal entering the set terminal; a switching circuit (34) electrically connected to the power supply (10) and configured to drive the oscillation circuit (36) at an operating frequency determined by the frequency of the output signal of the VFO (32); and A variable resistance component (40; 42) is electrically connected to a setting terminal of the VFO (32).

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

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

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

5. An aerosol generating device (2) according to claim 1 or claim 2, further comprising a control unit (44), and wherein: The variable resistance component is a digital potentiometer (42) having a resistance 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 a setting terminal of the VFO (32); a second potentiometer terminal electrically connected to a power supply voltage terminal of the VFO (32); and a data terminal configured to receive command data from the control unit (44) for selectively changing the resistance of the digital potentiometer (42).

7. An aerosol generating device (2) according to claim 5 or claim 6, wherein: The control unit (44) is configured to change the resistance of the digital potentiometer based on the estimated or determined impedance value of the oscillating circuit.

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

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

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

11. An aerosol generating device (2) according to claim 9 or claim 10, further comprising a second low pass filter (52) connected between the current sensor (48) and the voltage divider (54).

12. An aerosol-generating device (2) according to any preceding claim, wherein: The switching circuit (34) is an inverter.

13. An aerosol generating system (1) for generating an aerosol for inhalation by a user, the system (1) comprising an aerosol generating device (2) according to any preceding claim and an aerosol generating article (16), the aerosol generating article comprising a receptor (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, the system (1) comprising: Power supply (10); an oscillating circuit (36) configured to generate a time-varying electromagnetic field for inductively heating the susceptor (20); as well as A frequency generating circuit, the frequency generating circuit comprising a VFO (32), a switch circuit (34) electrically connected to the power supply (10), and a variable resistance component (40; 42); The method includes controlling the VFO (32) to provide an output signal having a frequency determined by the resistance of the variable resistance component (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 resistance component is a thermistor (40) having an internal resistance that varies with temperature or a digital potentiometer (42) having a resistance that selectively varies.

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