RU2800769C2 - Appliance for an aerosol generation apparatus - Google Patents

Abstract

FIELD: electrical engineering.

SUBSTANCE: invention relates to an aerosol generation apparatus, in particular, to an apparatus containing a temperature detector for determining the temperature of a current-collecting apparatus. Appliance for an aerosol generation apparatus comprises a resonant LC circuit containing an inductive element for induction heating of a current-collecting structure for heating the aerosol generating material so as to obtain an aerosol. The appliance comprises a switching apparatus for receiving a changing current from a DC voltage source and for the flow thereof through the inductive element, to cause the induction heating of the current-collecting structure. The appliance also comprises a temperature detector configured to determine the temperature of the current-collecting structure during use, based on the working frequency of the resonant LC circuit.

EFFECT: temperature of a current collector inductively heated using the inductive element of an LC resonant contour is determined by measuring the working frequency of the circuit.

31 cl, 5 dwg

Description

The technical field to which the invention belongs

The present invention relates to an instrument for an aerosol generating apparatus, in particular to an instrument comprising a temperature detector for determining the temperature of a current-collecting structure.

State of the art

Smoking articles such as cigarettes, cigars, etc. during their use, tobacco is burned to produce tobacco smoke. Attempts have been made to provide alternatives to these products by creating products that release compounds without burning. Examples of such products are so-called "non-burning" products or tobacco heating devices or products which release compounds when the material is heated but not burned. The substance may be, for example, tobacco or other non-tobacco products, which may or may not contain nicotine.

The essence of the invention

According to a first aspect of the present invention, there is provided an apparatus for an aerosol generating apparatus, the apparatus comprising: an LC resonant circuit comprising an inductive element for inductively heating a current-collecting structure to heat an aerosol generating material to thereby produce an aerosol; a switching device for receiving a varying current from a constant voltage source and flowing it through the inductive element to cause inductive heating of the current-collecting structure; and a temperature detector for determining, in use, the temperature of the current-collecting structure based on the frequency at which the LC circuit operates.

The temperature detector may be designed to, in addition to the frequency at which the resonant LC circuit operates, when used, determine the temperature of the current collector structure based on direct current from a direct current source.

The temperature detector may be designed to, in addition to the frequency at which the resonant LC circuit operates and the direct current from the direct current source in use, determine the temperature of the current-collecting structure based on the direct current voltage from the direct voltage source.

The LC circuit may be a parallel LC circuit containing a capacitive element in parallel with an inductive element.

The temperature detector can determine the effective group resistance of the inductive element and the current collector structure based on the frequency at which the resonant LC circuit operates, DC from a DC source, and DC voltage from a DC voltage source, and determines the temperature of the current collector structure based on the obtained effective group resistance. .

The temperature determiner may determine the temperature of the susceptor structure based on the calibration values of the effective group resistance of the inductive element and the susceptor structure and the temperature of the susceptor structure.

The calibration may be based on a polynomial equation, preferably a third order polynomial equation.

The temperature determiner can determine the effective group resistance r using the following formula:

where V _s is the DC voltage, I _s is the DC current, C is the capacitance of the resonant LC circuit, and f ₀ is the frequency at which the resonant LC circuit operates.

The frequency at which the resonant LC circuit operates may be the resonant frequency of the resonant LC circuit.

The switching device may be configured to switch between the first state and the second state, and the frequency at which the LC circuit operates may be determined based on determining the frequency at which the switching device switches between the first state and the second state.

The switching device may comprise one or more transistors, and the frequency at which the LC circuit operates can be determined by measuring the period with which one of the transistors switches between an on state and an off state.

The instrument may include a frequency-to-voltage converter configured to output a voltage value indicative of the frequency at which the LC circuit is operating.

DC voltage and DC current may be estimated values.

The values obtained for DC voltage and/or DC current may be the values measured by the instrument.

The calibration of the values between the effective group resistance and the temperature of the current collector structure may be one of a plurality of calibrations between the effective group resistance and the temperature of the current collector structure, and the temperature detector may be configured to select one of the plurality of calibrations for use in determining the temperature of the current collector from the effective group resistance values. .

The instrument may include a temperature sensor configured to detect a temperature associated with the current-collecting structure prior to being heated by the inductive element, and the temperature detector may use the temperature sensed by the temperature sensor to select a calibration.

The temperature measured by the temperature sensor may represent the ambient temperature for the aerosol generating device.

The aerosol receiving device may include a chamber for inserting a current-collecting structure, for example, a chamber for inserting a consumable containing a current-collecting structure, and the temperature measured by the temperature sensor may be the temperature of the chamber.

The temperature determiner may be configured to determine the effective group resistance value corresponding to the temperature detected by the temperature sensor and select a calibration from the plurality of calibrations based on a comparison between the temperature determined by the temperature sensor and the temperature specified by each calibration from the plurality of calibrations using the effective value. group resistance corresponding to the temperature determined by the temperature sensor.

Each calibration can be a calibration curve, or a polynomial equation, or a set of calibration values in a lookup table.

The temperature detector may be configured to perform a calibration selection each time the aerosol generating device is turned on or each time the aerosol generating device enters an aerosol generating mode.

The switching device may be configured to switch between the first state and the second state in response to voltage fluctuations in the resonant circuit operating at the resonant frequency of the resonant circuit, and thereby can maintain a varying current at the resonant frequency of the resonant circuit.

The switching device may comprise a first transistor and a second transistor, and if the switching device is in the first state, then the first transistor is off and the second transistor is on, and if the switching device is in the second state, then the first transistor is on and the second is off.

The first transistor and the second transistor may include a first terminal for turning the transistor on and off, a second terminal and a third terminal, and wherein the switching device is configured such that the first transistor switches from an on state to an off state if the voltage at the second terminal of the second transistor is less than or equal to threshold switching voltage of the first transistor.

The first transistor and the second transistor may comprise a first terminal for turning this transistor on and off, a second terminal and a third terminal, wherein the switching device is configured such that the second transistor switches from on to off if the voltage at the second terminal of the first transistor is less than or equal to the threshold switching voltage of the second transistor.

The resonant circuit may also include a first diode and a second diode, and the first terminal of the first transistor may be connected to the second terminal of the second transistor through the first diode, and the first terminal of the second transistor may be connected to the second terminal of the first transistor through the second diode, thereby the first terminal of the first transistor is low when the second transistor is on, and the first terminal of the second transistor is low when the first transistor is on.

The switching device may be configured such that the first transistor switches on from off if the voltage at the second terminal of the second transistor is less than or equal to the switching threshold voltage of the first transistor plus the bias voltage of the first diode.

The switching device may be configured such that the second transistor switches on from off if the voltage at the second terminal of the first transistor is less than or equal to the switching threshold voltage of the second transistor plus the bias voltage of the second diode.

The first terminal of the constant voltage source may be connected to the first and second points in the resonant circuit, with the first point and the second point electrically located on each side of the inductive element.

The device may include at least one choke located between the DC voltage source and the inductive element.

According to a second aspect of the invention, an aerosol generating device is provided, comprising an apparatus according to the first aspect.

Brief description of the drawings

In FIG. 1 schematically shows an aerosol generating device according to an example.

In FIG. 2 schematically shows a resonant circuit according to the example.

In FIG. 3 shows plots of voltage, current, effective group resistance, and temperature of a current-collecting structure versus time in accordance with an example.

In FIG. 4 shows a plot of the temperature of the current-collecting structure as a function of the parameter r according to the example.

In FIG. 5 is a schematic representation of a plurality of plots of current-collecting structure temperature versus parameter r according to an example.

Detailed description of the invention

Induction heating is the process of heating an electrically conductive object (or current collector) using electromagnetic induction. An induction heater may include an inductive element, such as an induction coil, and a device for passing a varying electrical current, such as an alternating electrical current, through the inductive element. The changing electric current in an inductive element creates a changing magnetic field. An alternating magnetic field penetrates through a pantograph appropriately positioned relative to the inductive element, creating eddy currents inside the pantograph. The current collector has an electrical resistance to eddy currents, and therefore the flow of eddy currents against this resistance causes heating of the current collector due to Joule heating. In cases where the current collector contains a ferromagnetic material such as iron, nickel or cobalt, heat can also be generated by magnetic hysteresis losses in the current collector, i.e. the changing orientation of the magnetic dipoles in the magnetic material as a result of their alignment with the changing magnetic field.

With induction heating, compared to, for example, heating by heat transfer, heat is generated inside the current collector, which ensures rapid heating. In addition, there is no need for any physical contact between the induction heater and the current collector, allowing greater freedom in design and application.

The induction heater may comprise an LC circuit having an inductance L provided by an inductive element such as an electromagnet, which may be configured to inductively heat a current collector, and a capacitance C provided by a capacitor. In some cases, the circuit can be represented as an RLC circuit containing the resistance R provided by the resistor. In some cases, the resistance is provided by the ohmic resistance of the parts of the circuit connecting the inductive element and the capacitor, and therefore the circuit need not include a resistor as such. Such a circuit can be called, for example, an LC circuit. In such circuits, electrical resonance can be observed, which occurs at a certain resonant frequency, when the imaginary parts of the impedances or the admittance of the circuit elements cancel each other out.

One example of a circuit exhibiting electrical resonance is an LC circuit containing an inductive element, a capacitor, and optionally a resistor. One example of an LC circuit is a series circuit in which an inductive element and a capacitor are connected in series. Another example of an LC circuit is a parallel LC circuit in which an inductive element and a capacitor are connected in parallel. Resonance occurs in an LC circuit because the collapsing magnetic field of an inductive element generates an electric current in its windings, which charges the capacitor, while the discharging capacitor provides an electric current, which creates a magnetic field in the inductive element. The present disclosure focuses on parallel LC circuits. When a parallel LC circuit is driven at the resonant frequency, the dynamic impedance of the circuit is maximum (since the reactance of the inductive element is equal to that of the capacitor) and the current in the circuit is minimum. However, for a parallel LC circuit, an inductive element and a capacitor connected in parallel act as a current multiplier (effectively multiplying the current in the loop and hence the current through the inductive element). Thus, driving the RLC or LC circuit to or close to the resonant frequency can provide efficient and/or efficient induction heating by providing the largest amount of magnetic field penetrating the current collector.

A transistor is a semiconductor device for switching electronic signals. A transistor usually contains at least three leads for connection to an electronic circuit. In some prior art examples, alternating current can be applied to a circuit using a transistor by applying a control signal that causes the transistor to switch at a predetermined frequency, such as the resonant frequency of the circuit.

A field effect transistor (FET) is a transistor where the effect of an applied electric field can be used to change the effective conductance of the transistor. The FET may include a package B, a source terminal S, a drain terminal D, and a gate terminal G. The FET contains an active channel containing a semiconductor through which charge carriers, electrons or holes, can flow between the source S and the drain D. The conductance of the channel, i.e. the conductance between the drain D and the source S, is a function of the potential difference between the gate terminals G and the source S, for example, generated by the potential applied to the terminal G of the gate. In enrichment mode FETs, the FET may be turned off (i.e. substantially prevent current from flowing through it) when there is essentially zero voltage between the gate G and source S, and may be turned on (i.e. essentially allow current to flow through it) when there is a substantially non-zero voltage between the gate G and the source S.

An n-channel FET (or n-type FET) (n-FET) is a FET whose channel consists of an n-type semiconductor in which electrons are majority carriers and holes are minority carriers. For example, n-type semiconductors may contain an intrinsic semiconductor (such as, for example, silicon) doped with donor impurities (such as, for example, phosphorus). In n-channel FETs, the drain terminal D is at a higher potential than the source terminal S (ie, there is a positive drain-to-source voltage, or in other words, a negative source-to-drain voltage). In order to turn on the n-channel FET (ie, allow current to flow through it), a switching potential is applied to the gate terminal G which is higher than the potential at the source terminal S.

A p-channel FET (or p-type FET) (p-FET) is a FET whose channel consists of a p-type semiconductor in which holes are majority carriers and electrons are minority carriers. For example, p-type semiconductors may contain an intrinsic semiconductor (such as, for example, silicon) doped with acceptor impurities (such as, for example, boron). In p-channel FETs, the source terminal S is at a higher potential than the drain terminal D (ie, there is a negative drain-to-source voltage, or in other words, a positive source-to-drain voltage). To turn on the p-channel FET (i.e., allow current to flow through it), a switching potential is applied to the gate terminal G, which is lower than the potential at the source terminal S (and which may be, for example, higher than the potential at the drain terminal D ).

A metal-oxide-semiconductor field-effect transistor (MOSFET) is a field-effect transistor whose gate terminal G is electrically isolated from the semiconductor channel by an insulating layer. In some examples, the gate terminal G may be metallic and the insulating layer may be an oxide (such as, for example, silicon dioxide), hence the name "metal-oxide-semiconductor". However, in other examples, the gate may be made from materials other than metal, such as polysilicon, and/or the insulating layer may be made from materials other than oxide, such as other dielectric materials. Such devices are, however, commonly referred to as metal-oxide-semiconductor field-effect transistors (MOSFETs), and it is to be understood that the term field-effect transistors or MOSFETs as used herein should be interpreted to include such devices.

The MOSFET may be an n-channel MOSFET (or n-type transistor), where the semiconductor is n-type. An n-channel MOSFET (n-MOSFET, n-type MOSFET) can work in the same way as described above for an n-channel FET. As another example, the MOSFET may be a p-channel MOSFET (or p-type transistor), where the semiconductor is p-type. A p-channel MOSFET (p-MOSFET, p-type MOSFET) can work in the same way as described above for a p-channel FET. An n-type MOSFET typically has a lower source-to-drain resistance than a p-type MOSFET. Therefore, in the on state (i.e. when current flows through it), n-type MOSFETs generate less heat compared to p-type MOSFETs, and therefore can consume less power in operation than MOSFETs p-type. In addition, n-type MOSFETs generally have a shorter switching time (i.e., the characteristic response time from a change in the switching potential applied to the gate G terminal to switching the current flow through the MOSFET) compared to p-type MOSFETs. -type. This can improve the switching speed and improve the switching control.

In FIG. 1 schematically shows an aerosol generating device 100 according to an example. The aerosol generating device 100 includes a DC power supply 104, in this example a battery 104, a circuit 150 including an inductive element 158, a current collector structure 110, and an aerosol generating material 116.

In the example shown in FIG. 1, the current-collecting structure 110 is located within the consumable 120 along with the aerosol generating material 116. DC power source 104 is electrically coupled to circuit 150 and configured to supply DC electrical power to circuit 150. Device 100 also includes control circuit 106, in this example circuit 150 is connected to battery 104 via control circuit 106.

The control circuit 106 may include means for turning the device 100 on and off, for example, in response to user input. The control circuit 106 may, for example, include a puff detector (not shown) known per se and/or may receive user input via at least one button or touch control (not shown). The control circuit 106 may include means for controlling the temperature of the components of the device 100 or the components of the consumable 120 inserted into the device. In addition to inductive element 158, circuit 150 includes other components, which are described below.

The inductive element 158 may be, for example, a coil, which may be, for example, flat. The inductive element 158 may be made of copper (which has a relatively low resistivity), for example. Circuit 150 is configured to convert the DC input from DC source 104 to varying, for example, AC current through inductive element 158. Circuit 150 is configured to pass AC current through inductive element 158.

Current collector structure 110 is located relative to inductive element 158 for inductively transferring energy from inductive element 158 to current collector structure 110. Current collector structure 110 may be made of any suitable material that can be heated inductively, such as metal or a metal alloy, such as steel. . In some implementations, current-collecting structure 110 may comprise or be made entirely of a ferromagnetic material, which may contain one or a combination of metals such as iron, nickel, and cobalt. In some implementations, the current-collecting structure 110 may consist of, or be made entirely of, a non-ferromagnetic material, such as aluminum. The inductive element 158, through which an alternating current is passed, causes the current-collecting structure 110 to be heated by Joule heating and/or by magnetic hysteresis heating, as described above. The current-collecting structure 110 is configured to heat the aerosol generating material 116, for example, by conduction, convection and/or radiation heating, to generate an aerosol in use. In some examples, current-collecting structure 110 and aerosol generating material 116 form a single unit that can be inserted and/or removed from aerosol generating device 100 and can be disposable. In some examples, the inductive element 158 may be removed from the device 100, for example, for replacement. The aerosol generating device 100 may be portable. The aerosol generating device 100 may be configured to heat the aerosol generating material 116 to create an aerosol for inhalation by the user.

Note that in this context, the expression "aerosol generating material" refers to substances that emit volatile components when heated, usually in the form of vapor or aerosol. The "aerosol generating material" may be a non-tobacco material or a tobacco-containing material. For example, the aerosol generating material may be or contain tobacco. The aerosol generating material, for example, may include one or more of the following: tobacco itself, tobacco derivatives, exploded tobacco, reconstituted tobacco, tobacco extract, homogenized tobacco, or tobacco substitutes. The aerosol generating material may be in the form of ground tobacco, cut tobacco leaves, extruded tobacco, reconstituted tobacco, reconstituted aerosol material, liquid, gel, gel sheet, powder or agglomerates, and the like. The aerosol generating material may also include other non-tobacco products, which may or may not contain nicotine, depending on the product. The aerosol generating material may contain one or more humectants such as glycerin or propylene glycol.

Returning to FIG. 1, the aerosol generating device 100 includes an outer housing 112 housing a DC source 104, a control circuit 106, and a circuit 150 containing an inductive element 158. example is also inserted into the housing 112 to prepare the device 100 for use. The outer housing 112 includes a mouthpiece 114 to allow aerosol generated during use to exit the device 100.

In use, the user may activate, for example, with a button (not shown) or a puff detector (not shown), the circuit 106 to cause a varying, for example, alternating current to pass through the inductive element 108, thereby inductively heating the current collector structure 110 , which in turn heats the aerosol generating material 116 and causes the aerosol generating material 116 to generate aerosol. The resulting aerosol enters the air drawn into the device 100 through an air inlet (not shown) and is thereby carried to the mouthpiece 104 where the aerosol exits the device 100 for inhalation by the user.

The circuit 150 including the inductive element 158 and the current collector structure 110 and/or the device 100 as a whole can be adapted to heat the aerosol generating material 116 to a certain temperature range to vaporize at least one component of the aerosol generating material 116 without burning. aerosol generating material. For example, the temperature range may be 50°C to 350°C, such as 50°C to 300°C, 100°C to 300°C, 150°C to 300°C, 100°C to 200 °C, 200°C to 300°C, or 150°C to 250°C. In some examples, the temperature range is from about 170°C to 250°C. In some examples, the temperature range may differ from this range, and the upper limit of the temperature range may be greater than 300°C.

It should be understood that there may be a difference between the temperature of the current collector structure 110 and the temperature of the aerosol generating material 116, for example, during heating of the current collector structure 110, for example, when the heating rate is high. Thus, it should be understood that, in some instances, the temperature to which current-collecting structure 110 is heated may be, for example, higher than the temperature to which aerosol generating material 116 is desired to be heated.

Let us now turn to FIG. 2, which shows an example of a circuit 150, which is a resonant circuit, for inductively heating the current-collecting structure 110. The resonant circuit 150 includes an inductive element 158 and a capacitor 156 connected in parallel.

The resonant circuit 150 includes a switching device M1, M2, which in this example includes a first transistor M1 and a second transistor M2. The first transistor M1 and the second transistor M2 comprise a first terminal G, a second terminal D and a third terminal S. The second terminals D of the first transistor M1 and the second transistor M2 are connected to one side of the parallel connected inductive element 158 and the capacitor 156, as will be explained in more detail below. . The third terminals S of the first transistor M1 and the second transistor M2 are connected to ground 151. In the example shown in FIG. 2, the first transistor M1 and the second transistor M2 are MOSFETs, and the first G terminals are gate terminals, the second D terminals are drain terminals, and the third S terminals are source terminals.

It should be understood that alternative types of transistors may be used in place of the MOSFETs described above in alternative examples.

The resonant circuit 150 has an inductance L and a capacitance C. The inductance L of the resonant circuit 150 is provided by the inductive element 158, and can also be affected by the inductance of the current collector structure 110, which is configured to be inductively heated by the inductive element 158. The inductive heating of the current collector structure 110 is carried out by an alternating magnetic field generated by the inductive element 158, which, as described above, causes Joule heating and/or magnetic hysteresis losses in the current collector structure 110. The inductance L of the resonant circuit 150 may be associated with the magnetic permeability of the current collector structure 110. The changing magnetic field generated by the inductive element 158 is created by a changing, for example, alternating current flowing through the inductive element 158.

The inductive element 158, for example, may be in the form of a coiled conductive element. For example, inductive element 158 may be a copper coil. The inductive element 158 may comprise, for example, a stranded wire, such as a high frequency winding wire, such as a wire containing several individually insulated wires twisted together. The resistance of the stranded wire to alternating current depends on the frequency, and the stranded wire can be designed in such a way that the power consumption of the inductive element decreases at the driving frequency. As another example, the inductive element 158 may be, for example, a helical track on a printed circuit board. The use of a helical track on a PCB can be beneficial as it gives a rigid and self-supporting track with a cross section that eliminates any requirement for stranded wire (which can be expensive) that can be mass-produced with high reproducibility at low cost. Although one inductive element 158 is shown, it is understood that there may be more than one inductive element 158 for inductively heating one or more current collector structures 110.

The capacitance C of the resonant circuit 150 is provided with a capacitor 156. The capacitor 156 may be, for example, a class 1 ceramic capacitor, such as a COG type capacitor. The total capacitance C may also include the parasitic capacitance of the resonant circuit 150; however, it is negligible compared to the capacitance provided by capacitor 156.

The resistance of resonant circuit 150 is not shown in FIG. 2, but it should be understood that the resistance of the circuit may be provided by the resistance of the trace or wire connecting the components of the resonant circuit 150, the resistance of the inductive element 158, and/or the resistance to the current flowing through the resonant circuit 150 provided by the current-sinking structure 110 for transferring power using inductive element 158. In some examples, one or more special resistors (not shown) may be included in resonant circuit 150.

The resonant circuit 150 is supplied with a DC voltage V1 provided by a DC source 104 (see FIG. 1), such as a battery. The positive terminal of the DC voltage source V1 is connected to the resonant circuit 150 at the first point 159 and at the second point 160. The negative terminal (not shown) of the DC voltage source V1 is connected to ground 151 and therefore, in this example, to the source terminals S of both MOSFETs M1 and M2. In examples, the DC supply voltage V1 may be supplied to the resonant circuit directly from the battery or through an intermediate element.

Therefore, resonant circuit 150 can be viewed as an electrical bridge with inductor 158 and capacitor 156 connected in parallel between the two arms of the bridge. The resonant circuit 150 operates to create a switching effect, described below, whereby a varying, for example, alternating current flows through the inductive element 158, thus creating an alternating magnetic field and heating the current-collecting structure 110.

The first point 159 is connected to the first node A, located on the first side of the parallel combination of inductive element 158 and capacitor 156. The second point 160 is connected to the second node B, located on the second side of the parallel combination of inductive element 158 and capacitor 156. The first inductor 161 is connected in series between the first point 159 and the first node A, and the second choke 162 is connected in series between the second point 160 and the second node B. The first and second chokes 161 and 162 serve to filter AC frequencies, not passing them into the circuit from the first point 159 and the second point 160 respectively, but allowing direct current to flow into and through the inductive element 158. Chokes 161 and 162 allow the voltage at nodes A and B to oscillate with little or no visible effects at the first point 159 or the second point 160.

In this particular example, the first MOSFET M1 and the second MOSFET M2 are n-channel MOSFETs operating in enrichment mode. The drain terminal of the first MOSFET M1 is connected to the first node A via a wire or the like, while the drain terminal of the second MOSFET M2 is connected to the second node B via a wire or the like. The source terminal of each MOSFET M1, M2 is connected to ground 151.

The resonant circuit 150 contains a second voltage source V2, a gate voltage source (or sometimes referred to here as a control voltage), with its positive terminal connected to a third point 165, which is used to energize the G gate terminals of the first and second MOSFETs M1 and M2. The control voltage V2 applied to the third point 165 in this example is independent of the voltage V1 applied to the first and second points 159, 160, which allows the voltage V1 to be changed without affecting the control voltage V2. The first terminating resistor 163 is connected between the third point 165 and the gate terminal G of the first MOSFET M1. A second terminating resistor 164 is connected between the third point 165 and the gate terminal G of the second MOSFET M2.

In other examples, a different type of transistor may be used, such as a different type of FET. It should be understood that the switching effect described below can equally be achieved with another type of transistor that is capable of switching from an on state to an off state. The values and polarities of the supply voltages V1 and V2 can be chosen depending on the properties of the used transistor and other components in the circuit. For example, supply voltages can be selected depending on whether an n-channel transistor or a p-channel is used, or depending on the configuration in which the transistor is connected, or on the potential difference applied to the transistor's terminals, which causes the transistor is either on or off.

The resonant circuit 150 also includes a first diode d1 and a second diode d2, which in this example are Schottky diodes, but in other examples any other suitable type of diode may be used. The gate terminal G of the first MOSFET M1 is connected to the drain terminal D of the second MOSFET M2 via the first diode d1, with the conducting direction of the first diode d1 directed towards the drain D of the second MOSFET M2.

The gate terminal G of the second MOSFET M2 is connected to the drain terminal D of the first MOSFET M1 via a second diode d2, with the conductive direction of the second diode d2 directed towards the drain D of the first MOSFET M1. The first and second Schottky diodes d1 and d2 can have a diode threshold voltage of about 0.3V. In other examples, silicon diodes having a diode threshold voltage of about 0.7V can be used. In the examples, the type of diode used is chosen in conjunction with the gate threshold voltage, to ensure the required switching of MOSFETs M1 and M2. It should be understood that the diode type and gate supply voltage V2 can also be selected in conjunction with the values of the terminating resistors 163 and 164 as well as other components of the resonant circuit 150.

The resonant circuit 150 maintains current through the inductive element 158, which is an alternating current due to the switching of the first and second MOSFETs M1 and M2. Since, in this example, the MOSFETs M1 and M2 are enrichment mode MOSFETs, if the voltage applied to the gate terminal G of one of the MOSFETs is such that the gate-to-source voltage is higher than a predetermined threshold for this MOSFET, the MOSFET turns on. Current can then flow from the drain terminal D to the source terminal S which is connected to ground 151. The series resistance of the MOSFET in this on state is negligible for circuit operation, and the drain terminal D can be considered to be at ground potential when the MOSFET is the transistor is on. The gate-source threshold for the MOSFET may be any suitable value for the resonant circuit 150, and it will be understood that the voltage V2 and the resistance of resistors 164 and 163 are chosen depending on the gate-source threshold voltage of the MOSFETs M1 and M2 essentially so that V2 is greater than the gate threshold voltage(s).

A switching procedure of the resonant circuit 150 will now be described which causes the current flowing through the inductive element 158 to change from a state where the voltage at the first node A is high and the voltage at the second node B is low.

If the voltage at node A is high, then the voltage at the drain pin D of the first MOSFET M1 is also high, because in this example the drain pin of M1 is connected directly to node A via a conductor. At the same time, if the voltage at node B is kept low, then the voltage at the source terminal D of the second MOSFET M2 is correspondingly low (in this example, the source terminal of transistor M2 is directly connected to node B via a conductor).

Accordingly, at this time, the drain voltage value of the transistor M1 is high and greater than the gate voltage of the transistor M2. Therefore, the second diode d2 is reverse biased at this time. The gate voltage of the transistor M2 at this time is greater than the voltage at the source terminal of the transistor M2, and the voltage V2 is such that the gate-source voltage of the transistor M2 is greater than the turn-on threshold for the MOSFET M2. So M2 is on at this time.

At the same time, the drain voltage of the transistor M2 is low and the first diode d1 is forward-biased due to the application of the gate voltage V2 to the gate terminal of the transistor M1. Thus, the gate terminal of the transistor M1 is connected through the forward biased first diode d1 to the low voltage drain terminal of the second MOSFET M2, and therefore the gate voltage of the transistor M1 is also low. In other words, since transistor M2 is on, it acts as a ground clamp, which causes the first diode d1 to be forward biased and the gate voltage of transistor M1 to be low. Thus, the gate-source voltage of the transistor M1 is below the turn-on threshold, and the first MOSFET M1 is turned off.

In general, at this point, the circuit 150 is in the first state, in which:

voltage at node A is high; voltage at node B is low; the first diode d1 is forward biased;

the second MOSFET M2 is on;

the second diode d2 is reverse biased; And

the first MOSFET M1 is turned off.

From now on, when the second MOSFET M2 is in the on state and the first MOSFET M1 is in the off state, the current from the source V1 passes through the first choke 161 and through the inductive element 158. Due to the presence of the inductive choke 161, the voltage in node A is free to oscillate. Because inductor 158 is in parallel with capacitor 156, the observed voltage at node A follows a half-sine voltage profile. The frequency of the observed voltage at node A is equal to the resonant frequency f ₀ of circuit 150.

The voltage at node A decreases sinusoidally over time from a maximum value to 0 as a result of the weakening of the energy at node A. The voltage at node B is kept low (because the MOSFET M2 is on) and the inductive element L is charged from the DC source V1. MOSFET M2 turns off at the point in time when the voltage at node A is equal to or lower than the gate threshold voltage of M2 plus the forward bias voltage of diode d2. When the voltage at node A finally reaches zero, the MOSFET M2 will be completely turned off.

At the same time, or shortly thereafter, the voltage at node B goes high. This is due to resonant power transfer between inductive element 158 and capacitor 156. When the voltage at node B becomes high due to this resonant power transfer, the situation described above with respect to nodes A and B and MOSFETs M1 and M2, changes to the opposite. That is, when the voltage across A decreases to zero, the drain voltage of transistor M1 decreases. The drain voltage of transistor M1 is reduced to the point where the second diode d2 is no longer reverse biased and becomes forward biased. Similarly, the voltage at node B rises to its maximum and the first diode d1 switches from forward bias to reverse bias. When this happens, the gate voltage of the transistor M1 is no longer related to the drain voltage of the transistor M2, and therefore the gate voltage of the transistor M1 becomes high when the gate voltage V2 is applied. Therefore, the first MOSFET M1 turns on because its gate-source voltage now exceeds the turn-on threshold. Since the gate terminal of transistor M2 is now connected via the forward biased second diode d2 to the low voltage drain terminal of transistor M1, the gate voltage of transistor M2 is low. Therefore, the transistor M2 turns off.

In general, at this point circuit 150 is in a second state in which:

voltage at node A is low; voltage at node B is high; the first diode d1 is reverse biased; the second MOSFET M2 is off;

the second diode d2 is forward biased; And

the first MOSFET M1 is turned on.

At this point, the current flows through the inductive member 158 from the supply voltage V1 through the second inductor 162. Thus, the direction of the current is reversed due to the switching operation of the resonant circuit 150. The resonant circuit 150 will continue to switch between the above-described first state, in which the first the MOSFET M1 is turned off and the second MOSFET M2 is turned on, and the above-described second state in which the first MOSFET M1 is turned on and the second MOSFET M2 is turned off.

In steady state operation, energy is transferred between the electrostatic region (ie, capacitor 156) and the magnetic region (ie, inductive element 158), and vice versa.

The net switching effect occurs in response to voltage fluctuations in resonant circuit 150 where energy is transferred between the electrostatic region (i.e., capacitor 156) and the magnetic region (i.e., inductive element 158), thus creating a time-varying current in the parallel LC. circuit that changes at the resonant frequency of resonant circuit 150. This is advantageous for power transfer between inductive element 158 and current-collecting structure 110 because circuit 150 operates at an optimum level of efficiency and therefore provides more efficient heating of aerosol generating material 116 compared to with a circuit operating without resonance. The switching arrangement described is advantageous in that it allows circuit 150 to operate at resonant frequency under varying load conditions. This means that if the properties of the circuit 150 change (for example, if the current collector 110 is present or not, or if the temperature of the current collector changes, or even if the current collector 110 is physically moved), the dynamic nature of the circuit 150 continuously adapts its resonant point for optimal power transfer, which means that circuit 150 is always running in resonance. Moreover, circuit 150 is configured such that no external controller or the like is required to supply control voltage signals to the gates of the MOSFETs for switching.

In the examples described above with reference to FIG. 2, the gate terminals G are supplied with a gate voltage by a second power supply that is different from the source voltage V1. However, in some examples, the gate terminals may be supplied with the same voltage as the source voltage V1. In such examples, the first point 159, the second point 160 and the third point 165 in circuit 150 may, for example, be connected to the same power rail. In such examples, it should be understood that the properties of the circuit components must be chosen so that the described switching can take place. For example, the gate supply voltage and diode threshold voltages should be chosen such that circuit oscillations trigger the MOSFETs to switch at the appropriate level. Providing separate voltage values for the gate supply voltage V2 and the source voltage V1 allows the source voltage V1 to vary independently of the gate supply voltage V2 without affecting the operation of the circuit switching mechanism.

The resonant frequency f ₀ of circuit 150 may be in the megahertz range, for example, in the range from 0.5 MHz to 4 MHz, for example, in the range from 2 MHz to 3 MHz. It should be understood that the resonant frequency f ₀ of the resonant circuit 150 depends on the inductance L and capacitance C of the circuit 150 as discussed above, which in turn depends on the inductive element 158, the capacitor 156 as well as the current collector structure 110. As such, the resonant frequency f ₀ of circuit 150 may vary from implementation to implementation. For example, the frequency may be in the range of 0.1 MHz to 4 MHz, or in the range of 0.5 MHz to 2 MHz, or in the range of 0.3 MHz to 1.2 MHz. In other examples, the resonant frequency may be in a range other than that described above. Typically, the resonant frequency will depend on the characteristics of the circuit, such as the electrical and/or physical properties of the components used, including the current-collecting structure 110.

It is also understood that the properties of resonant circuit 150 may be selected based on other factors for a given current collector structure 110. susceptor structure 110, within which the current density falls by a factor of 1/e, which is at least a function of frequency) based on the material properties of the susceptor structure 110. The skin depth differs for different materials of the susceptor structures 110 and decreases with increasing drive frequency. On the other hand, for example, in order to reduce the proportion of power supplied to resonant circuit 150 and/or drive element 102 that is lost as heat within the electronic components, a circuit that operates at relatively lower frequencies may be preferred. Since the driving frequency is equal to the resonant frequency in this example, the questions regarding the driving frequency are considered here in relation to obtaining an appropriate resonant frequency, for example, by developing a current-collecting structure 110 and/or using a capacitor 156 with a certain capacitance and an inductive element 158 with a certain inductance. Therefore, in some instances, a compromise between these factors may be selected as appropriate and/or desirable.

Resonance circuit 150 in FIG. 2 has a resonant frequency f ₀ at which the current I is minimized and the dynamic impedance is maximized. The resonant circuit 150 operates at this resonant frequency, and therefore the oscillating magnetic field generated by the inductive element 158 is maximum, and the inductive heating of the current-collecting structure 110 by the inductive element 158 is maximum.

In some examples, the induction heating of the current collector structure 110 by the resonant circuit 150 can be controlled by controlling the supply voltage supplied to the resonant circuit 150, which in turn can control the current flowing in the resonant circuit 150 and therefore can control the energy transmitted to the current collector. structure 110 via resonant circuit 150, and hence the degree to which current-collecting structure 110 is heated. duty cycle of the PWM voltage signal pulse) applied to the inductive element 158 depending on whether the current-collecting structure 110 needs to be heated to a greater or lesser extent.

As mentioned above, the inductance L of the resonant circuit 150 is provided by an inductive element 158 for inductively heating the current-collecting structure 110. At least a portion of the inductance L of the resonant circuit 150 is associated with the magnetic permeability of the current-collecting structure 110. Therefore, the inductance L and hence the resonant frequency f _{The 0} of resonant circuit 150 may depend on the particular current collector(s) used and its position relative to inductive element(s) 158, which may change from time to time. In addition, the magnetic permeability of the current collector structure 110 may change as the temperature of the current collector 110 changes.

In the examples described herein, the current collector structure 110 is contained in a consumable and therefore is replaceable. For example, the current-collecting structure 110 may be disposable and, for example, may be integrated into the material 116 that generates the aerosol it is intended to heat. The resonant circuit 150 allows the circuit to operate at a resonant frequency, automatically taking into account differences in the design and/or type of material of the various current collector structures 110 and/or differences in the placement of the current collector structures 110 relative to the inductive element 158 when the current collector structure 110 is replaced. the ability to operate in resonance independently of the particular inductor 158 or any component of the resonant circuit 150 used. This is particularly useful in order to account for changes in manufacturing, both in relation to the current-collecting design 110 and in relation to other components of the circuit 150. For example, the resonant circuit 150 allows the circuit to continue to operate at resonant frequency regardless of the use of different inductive elements 158 with different inductance values and/or differences in the placement of the inductive element 158 relative to the current-collecting structure 110. The circuit 150 can also operate at resonance even if components are replaced during the life of the device. .

Now, the operation of the aerosol generating device 100 including the resonant circuit 150 will be described according to an example. Before turning on the device 100, the device 100 may be in the off state, that is, no current flows in the resonant circuit 150. The device 150 is switched to the on state, for example, the user turns on the device 100. After the device 100 is turned on, the resonant circuit 150 begins to draw current from the voltage source 104, while the current passing through the inductive element 158 changes with the resonant frequency f ₀ . The device 100 may remain on until the controller 106 receives a new input, such as until the user stops pressing a button (not shown), or until the puff detector (not shown) is activated, or until the maximum time has elapsed. heating. The resonant circuit 150, operating at the resonant frequency f ₀ , causes an alternating current I to flow in the resonant circuit 150 and the inductive element 158 and hence inductively heat the current collector structure 110 for a given voltage. As the current-collecting structure 110 is heated inductively, its temperature (and hence the temperature of the aerosol generating material 116) increases. In this example, current-collecting structure 110 (and aerosol generating material 116) is heated so that it reaches a constant temperature T _MAX . The temperature T _MAX may be a temperature that is substantially equal to the temperature at which the aerosol generating material 116 generates a significant amount of aerosol. The temperature T _MAX may be, for example, from about 200 to about 300°C (although, of course, this may be a different temperature depending on the material 116, the current-collecting structure 110, the layout of the entire device 100, and/or other requirements and/or conditions) . Thus, the device 100 is in a "heating" state or mode in which the aerosol-generating material 116 reaches a temperature at which aerosol is mainly formed or a significant amount of aerosol is formed. It should be understood that in most if not all cases, as the temperature of the current collector structure 110 changes, so does the resonant frequency f ₀ of the resonant circuit 150. This is because the magnetic permeability of the current collector structure 110 is a function of temperature, and as described above, the magnetic permeability of the current-collecting structure 110 affects the coupling between the inductive element 158 and the current-collecting structure 110 and hence the resonant frequency f ₀ of the resonant circuit 150.

The present disclosure mainly describes the configuration of a parallel LC circuit. As mentioned above, for a parallel LC circuit at resonance, the impedance is maximum and the current is minimum. Note that the minimum current usually refers to the current seen outside of the parallel LC circuit, for example, to the left of choke 161 or to the right of choke 162. Conversely, in a series LC circuit, the current is at its maximum and, generally speaking, a resistor must be inserted to limit the current to a safe value that could otherwise damage some electrical components in the circuit. This usually reduces the efficiency of the circuit, as energy is lost through the resistor. A parallel circuit operating at resonance does not require such restrictions.

In some examples, current-collecting structure 110 comprises or consists of aluminum. Aluminum is an example of a non-ferrous metal and therefore has a relative magnetic permeability close to unity. This means that aluminum usually has a low degree of magnetization in response to an applied magnetic field. Therefore, it has generally been considered difficult to effect inductive heating of aluminium, especially at low voltages such as those used in aerosol delivery systems. It has also generally been found that operating the circuit at the resonant frequency is preferable as it provides optimum coupling between the inductive element 158 and the current collector structure 110. element 158 and thus a noticeable reduction in heating efficiency (in some cases to the extent that heating is no longer observed). As mentioned above, as the temperature of the current collector structure 110 changes, the resonant frequency f ₀ of the circuit 150 also changes. the advantage that the circuit always operates at the resonant frequency (regardless of any external control mechanism). This means that maximum inductive coupling and therefore maximum heating efficiency is achieved all the time, allowing the aluminum to be heated efficiently. It has been found that a consumable including an aluminum current collector can be heated efficiently if the consumable includes an aluminum wrapper that forms a closed electrical circuit and/or has a thickness of less than 50 microns.

In instances where current-collecting structure 110 forms part of a consumable, the consumable may be of the form described in PCT/EP2016/070178, which is incorporated herein by reference in its entirety.

The device 100 is equipped with a temperature detector for detecting the temperature of the current-collecting structure 110 in use. As shown in FIG. 1, the temperature detector may be a control circuit 106, such as a processor, that controls the overall operation of the device 100. The temperature detector 106 determines the temperature of the current-collecting structure 110 based on the frequency at which the resonant circuit 150 operates, the DC current from the DC voltage source V1, and the DC voltage V1 of the constant voltage source.

Without being limited by theory, the following description explains the derivation of relationships between the electrical and physical properties of the resonant circuit 150 that allow the temperature of the current-collecting structure 110 to be determined in the examples described herein.

When used, the impedance at resonance of the parallel combination of inductive element 158 and capacitor 156 is the dynamic impedance R _dyn .

As explained above, the operation of the switching device M1 and M2 causes the direct current drawn from the direct voltage source V1 to be converted into an alternating current that flows through the inductive element 158 and the capacitor 156. An induced current also occurs on the inductive element 158 and the capacitor 156. AC voltage.

As a result of the oscillatory nature of the resonant circuit 150, the impedance of the oscillatory circuit is R _dyn for a given source voltage V _s (voltage source V1). Current I _s will be drawn in response to R _dyn . Therefore, the load impedance R _{dyn of} the resonant circuit 150 can be equated to the impedance of the effective voltage and current drawn. This makes it possible to determine the load impedance by determining, for example, the measured values of DC voltage V _s and DC current I _s in accordance with equation (1) below.

(1)

At the resonant frequency f _0, the dynamic impedance R _dyn is

(2)

where the parameter r can be considered to represent the effective group resistance of the inductive element 158 and the effect of the current-collecting structure 110 (if any), and, as described above, L is the inductance of the inductive element 158, and C is the capacitance of the capacitor 156. The parameter r is described here as effective group resistance. As will be clear from the description below, the parameter r is measured in units of resistance (Ω), but in certain circumstances it may not be considered as representing the physical/actual resistance of the circuit 150.

As described above, the inductance of the inductive element 158 here takes into account the interaction of the inductive element 158 with the current collector structure 110. Thus, the inductance L depends on the properties of the current collector structure 110 and the position of the current collector structure 110 relative to the inductive element 158. The inductance L of the inductive element 158 and, therefore, the resonant circuit 150 depends, among other factors, on the magnetic permeability μ of current-collecting structure 110. Permeability μ is a measure of a material's ability to support the formation of a magnetic field within itself, and it expresses the degree of magnetization the material receives in response to an applied magnetic field. The magnetic permeability μ of the material constituting the current-collecting structure 110 may change with temperature.

From equations (1) and (2) one can obtain the following equation (3)

(3)

The relation of resonant frequency f ₀ to inductance L and capacitance C can be modeled in at least two ways given by equations (4a and 4b) below.

(4a)

(4b)

Equation (4a) represents the resonant frequency modeled using a parallel LC circuit containing an inductive element L and a capacitor C, while equation (4b) represents the resonant frequency modeled using a parallel LC circuit with an additional resistor r connected in series with the inductive element L. For equation (4b), it should be understood that as r goes to zero, equation (4b) goes to equation (4a).

In what follows, we assume that r is small and therefore we can use equation (4a). As will be described below, this approximation works well because it combines changes in circuit 150 (eg, inductance and temperature) in terms of the L representation. From equations (3) and (4a), the following expression can be obtained

(5)

It should be understood that equation (5) gives an expression for the parameter r in terms of measurable or known quantities. Here it should be understood that the parameter r is affected by the inductive coupling in the resonant circuit 150. In the loaded state, that is, in the presence of a current-collecting structure, we cannot consider the value of the parameter r small. In this case, the parameter r may no longer be an accurate representation of the group resistances, but instead is a parameter that is affected by the effective inductive coupling in the circuit 150. The parameter r is referred to as a dynamic parameter that depends on the properties of the current collector structure 110 as well as on the temperature T of the current collector. designs.

The value of the DC source V _s is known (e.g. the battery voltage) or can be measured with a voltmeter, and the value of the DC current I _s drawn from the DC voltage V1 can be measured by any suitable means, for example using a voltmeter suitably set for measurement of source voltage V _s .

To be able to obtain the parameter r, the frequency f ₀ can be measured and/or determined.

In one example, the frequency f ₀ can be measured using the converter 210 frequency to voltage (F/V). The F/V converter 210 may, for example, be connected to the gate terminal of the first MOSFET M1 or the second MOSFET M2. In examples where other types of transistors are used in the switching mechanism of the circuit, the F/V converter 210 may be connected to a gate terminal or other terminal that outputs a periodic voltage signal at a frequency equal to the switching frequency of one of the transistors. Therefore, the F/V converter 210 may receive a signal from the gate terminal of one of the MOSFETs M1, M2 representing the resonant frequency f ₀ of the resonant circuit 150. The signal received by the F/V converter 210 may be an approximately square wave with a period representing the resonant frequency of the resonant circuit 210. The F/V converter 210 can then use this period to represent the resonant frequency f ₀ as the output voltage.

Accordingly, since C is known from the capacitance value of capacitor 156, and V _s , I _s and f ₀ can be measured, for example, as described above, the parameter r can be determined from these measured and known values.

The parameter r of the inductive element 158 varies with temperature and further with the inductance L. This means that the parameter r has a first value when the resonant circuit 150 is in an "unloaded" state, i.e. when the inductive element 158 is not inductively coupled to the current collector structure 110, and the value of r changes when the circuit enters the "loaded" state, that is, when the inductive element 158 and the current collector structure 110 are inductively coupled to each other.

When using the method described in this document to determine the temperature of the current-collecting structure 110 consider whether the circuit is in the "loaded" state or in the "unloaded" state. For example, the value of parameter r of inductive element 158 in a particular configuration may be known and compared with a measured value to determine whether the circuit is in a "loaded" or "unloaded" state. In the examples, whether the circuit is in a loaded or unloaded state can be determined by control circuit 106 detecting the insertion of the current collector structure 110, for example, detecting the insertion of a consumable containing the current collector structure 110 into the device 100. The insertion of the current collector structure 110 may be detected by any suitable means such as, for example, an optical sensor or a capacitive sensor. In other examples, the unloaded value of the parameter r may be known and stored in the control circuit 106 . In some examples, current-collecting structure 119 may include a portion of device 100 such that resonant circuit 150 can be considered to be in a permanently loaded state.

Once it is determined or can be assumed that the resonant circuit 150 is in a loaded state, with the susceptor structure 110 inductively coupled to the inductive element 158, it can be assumed that a change in the parameter r indicates a change in the temperature of the susceptor structure 110. For example, a change in r can be considered as evidence of heating of the current-collecting structure 110 by the inductive element 158.

The device 100 (or the actual resonant circuit 150) can be calibrated so that the temperature detector 106 can determine the temperature of the current-collecting structure 110 based on the measurement of the parameter r.

Calibration can be performed on the resonant circuit 150 itself (or on an identical test circuit used for calibration purposes) by measuring the temperature T of the susceptor structure 110 with a suitable temperature sensor such as a thermocouple at several given values of r and plotting r from T.

In FIG. 3 shows an example of the measured values of V _s , I _s , r and T plotted on the y-axis as a function of the time t of operation of the resonant circuit 150 plotted on the x-axis. It can be seen that at a substantially constant source voltage V _s of about 4 V, within about 30 seconds, the constant current I _s increases from about 2.5 A to about 3 A, and the parameter r increases from about 1.7-1, 8 ohm to about 2.5 ohm. At the same time, the temperature T rises from about 20-25°C to about 250-260°C.

In FIG. 4 shows a calibration plot based on the r and T values shown in FIG. 3 and described above. In FIG. 4, the temperature T of the current collector structure 110 is shown on the y-axis, the parameter r is shown on the x-axis. In the example in FIG. 4, a function was selected for the plot of T versus r, which in this example is a polynomial function of the third order. The function is fitted to values of r that correspond to a change in temperature T. As noted above, the value of the parameter r can also change between an unloaded state (when there is no current collector structure 110) and a loaded state (when there is a current collector structure 110), although this is not shown in FIG. . 4. Thus, the range of r chosen to be plotted for such a calibration can be chosen to exclude any changes in r due to changes in the circuit, eg changes between "loaded" and "unloaded" states. In other examples, other functions may be fitted to the graph, or an array of r and T values may be stored, for example, as a lookup table. Although, as noted above, in the loaded state we cannot assume that the value of r is small, it was found that the approximation of equation 4a still allows you to accurately track the temperature T. Without wishing to be limited by theory, it is believed that changes in various electrical and magnetic circuit parameters are "taken into account" in the E value of Equation 4a.

In use, the temperature detector 106 takes the values of DC voltage V _s , DC current I _s and frequency f ₀ and determines the value of the parameter r in accordance with Equation 5 above. temperature calculation using a function such as that shown in FIG. 4, or by searching the table of values for parameter r and temperature T obtained by calibration, as explained above.

In some instances, this may allow the control circuit 106 to take action based on a determined temperature of the pantograph 110. For example, the supply voltage may be turned off or reduced (either by lowering the supplied voltage or by reducing the average voltage supplied in the duty cycle if a wide-width circuit is used). -pulse modulation) if the obtained temperature T of the pantograph is higher than a predetermined value.

In some examples, the method for determining the temperature T from the parameter r may comprise assuming a relationship between T and r, determining the change in r, and determining the change in temperature T from the change in r.

In FIG. 4 shows a single calibration curve that characterizes a particular current-collecting structure 110 geometry, material type, and/or position relative to the inductive element 158. a calibration curve may be sufficient to account for manufacturing tolerances, for example. In other words, the temperature measurement error (at a certain value of r) can be allowed to allow for various manufacturing tolerances of the single current collector structure 110. Therefore, the control circuit 106 is configured to perform the operations of determining the value of r, then determining the temperature value T (for example, using polynomial curve or lookup table as shown above).

In other examples, particularly those where the current collector has a different shape and/or material, different calibration curves (eg, different third order polynomials) may be required for these different current collector structures 110. FIG. 5 shows a basic representation of a set of three calibration curves, each with a corresponding polynomial function fitted to it (not shown). As in FIG. 4, the temperature T of current-collecting structure 110 is shown on the y-axis, and the effective group resistance r is shown on the x-axis. By way of example and illustration only, curve A may represent a stainless steel pantograph, curve B may represent an iron pantograph, and curve C may represent an aluminum pantograph.

In aerosol generation devices 100 into which various current collector structures 110 may be inserted and heated, the control circuit 106 may also be configured to determine which of the calibration curves (e.g., selected from curves A, B, or C in FIG. 5) is correct curve to use for the inserted current collector structure 110. In one example, the aerosol generating device 100 may be equipped with a temperature sensor (not shown) that is configured to measure the temperature associated with the device 100. In one implementation, the temperature sensor may be configured to detect ambient temperature around the device 100 (i.e. ambient temperature). This temperature may be indicative of the temperature of the current collector 110 just prior to insertion into the device 110, assuming that the current collector has not been heated by any means other than the environment immediately prior to insertion. In other examples, the temperature sensor may be configured to measure the temperature of the chamber for inserting the consumable 120.

As generally shown in FIG. 5, the value of r can be determined (r _det ) based on Equation (5). The value of r _det is measured either immediately after the current-collecting structure 110 is placed in the device 100 (if the inductive element 158 is currently active), or immediately after the activation of the inductive element 158 (i.e., immediately after the circuit 150 begins to flow ). That is, r _det is preferably determined in the absence of any additional heating caused by power transfer from inductive element 158. As seen in FIG. 5, for a given value of r _det, there are several possible temperature values (T1, T2 and T3), each corresponding to a point on one of the calibration curves. To determine which of the calibration curves is the most appropriate to use for the current collector structure 110 that has been inserted into the device 100, the control circuit 106 is configured to first determine the value of r (as described above). The control circuit 106 is configured to receive/receive a temperature measurement (or an indication and a temperature measurement) from a temperature sensor and compare the temperature measurement with temperature values corresponding to a certain value of r for each of the calibration curves (or a subset thereof). By way of example and with reference to FIG. 5, if the temperature sensor measures a temperature t equal to T1, then the control circuit compares the measured temperature T with three temperature values T1, T2, T3 corresponding to a certain value r for each calibration curve A, B, C. Depending on the result of the comparison, the control circuit sets a calibration curve having a temperature value closest to the measured/obtained temperature value as a calibration curve for this current collector structure 110. In the above example, calibration curve A is set by the control circuit 106 as a calibration curve for the inserted current collector 110. Thereafter, each once the control circuit 106 determines the value of r, the temperature of the current-collecting structure 110 is calculated based on the selected calibration curve (curve A). Although it has been described above that a calibration curve is selected/specified, it should be understood that this may mean that a polynomial equation representing the curve is selected, or a plurality of calibration values corresponding to the curve may be selected, for example, in a look-up table.

In this regard, the comparison step described above may be performed in accordance with any suitable comparison algorithm. For example, suppose the measured temperature is between T1 and T2. The control circuit 106 may select either Curve A or Curve B depending on the algorithm used. The algorithm may choose the curve having the smallest difference (that is, the one for which the T2-t or T1-t difference is the smallest). Other algorithms may be implemented, such as selecting the largest value (in this case T2). The principles of the present invention are not limited to the particular algorithm used.

In addition, the control circuit 106 may be configured to repeat the process of determining the calibration curve under certain conditions. For example, the control circuit 106 may be configured to repeat the process of identifying the corresponding curve at the appropriate time (eg, when the inductive element 158 is first energized) each time the device is turned on. In this regard, the device 100 may have several modes of operation, such as an initial turn-on state where battery power is applied to the control circuit 106 (but not to the resonant circuit 150). Transition to this state can occur, for example, when a user presses a button on the surface of the device 100. The device 100 can also have an aerosol generation mode in which energy is also applied to the resonant circuit 150. It can be activated either by a button or by a puff sensor ( as described above). Therefore, the control circuit 106 can be configured to repeat the selection process of the appropriate calibration curve when the aerosol generation mode is selected for the first time. Alternatively, the control circuit 106 may be configured to determine when the current-collecting structure is removed from (or inserted into) device 100 and to repeat the calibration curve determination process at the next appropriate opportunity.

While it has been described above that the control circuit uses Equations 4a and 5, it should be understood that other equations having the same or similar effect may be used in accordance with the principles of the present invention. In one example, R _dyn may be calculated from the AC current and voltage values in circuit 150. For example, the voltage at node A may be measured and found to be different from V _s - we call this voltage V _ac . The voltage V _ac can be measured by almost any suitable method, but it is an AC voltage in a parallel LC circuit. Using this, one can determine the alternating current, I _ac , by equating the power of alternating and direct current. That is, V _ac I _ac =V _s I _s . The parameters V _s and I _s may be replaced by their AC equivalents in equation 5 or any other suitable equation for the parameter r. It should be understood that in this case, another set of calibration curves can be implemented.

While the above description describes the operation of the temperature measurement concept in the context of circuit 150 that is configured to self-excite at resonant frequency, the above concepts also apply to an induction heating circuit that is not configured to operate at resonant frequency. For example, the above-described pantograph temperature detection method may be performed with an induction heating circuit that operates at a predetermined frequency, which may not be the resonant frequency of the circuit. In one such example, an induction heating circuit may be driven via a bridge control circuit containing a switching mechanism such as a plurality of MOSFETs. The bridge control circuit may be controlled by a microcontroller or the like to use a DC voltage to supply an alternating current to the inductive element at a switching frequency of the bridge control circuit set by the microcontroller. In such an example, it is assumed that the above relationships set forth in equations (1)-(5) hold and provide a valid, eg, usable estimate of the current collector temperature T for frequencies in the frequency range including the resonant frequency. In an example, the method described above can be used to obtain a calibration between the parameter r and temperature T at the resonant frequency, and then the same calibration is used to relate r and T if the circuit is not in resonance. However, it should be understood that the derivation of equation 5 assumes that the circuit 150 operates at the resonant frequency f ₀ . Therefore, it is likely that the error associated with a certain temperature will increase as the difference between the resonant frequency f ₀ and the predetermined operating frequency increases. In other words, the temperature measurement can be determined with greater accuracy when the circuit is operated at or near the resonant frequency. For example, the above method of correlating and determining r and T can be used for frequencies in the range f ₀ -Δf to f ₀ +Δf, where Δf, for example, can be determined experimentally by directly measuring the temperature T of the pantograph and checking the above relationships. For example, larger values of Δf may provide less accuracy in determining the current collector temperature T, but may still be applicable.

In some examples, the method may include assigning constant values of V _s and I _s and assuming that these values do not change when the parameter r is calculated. Then it may not be necessary to measure the voltage V _s and current I _s to estimate the temperature of the current collector. For example, voltage and current may be known approximately from the properties of the power supply and the circuit, and may be assumed to be constant over the entire range of temperatures used. In such examples, the temperature T can be estimated by measuring only the frequency at which the circuit is operating and using assumed or previously measured voltage and current values. Thus, the invention can provide a method for determining the temperature of a pantograph by measuring the frequency of the circuit. In some implementations, the invention may provide a method for determining the temperature of a current collector by measuring the frequency of the circuit only.

The above examples are to be understood as illustrative examples of the invention. It should be understood that any feature described in relation to any example may be used alone or in combination with other features described, and may also be used in combination with one or more features of any other example, or any combination of any other examples. In addition, equivalents and modifications not described above may also be used without departing from the scope of the invention as defined in the appended claims.

Claims (36)

1. A device for determining the temperature of a pantograph for an aerosol generation device, containing: an LC resonant circuit comprising an inductive element for inductively heating the current-collecting structure for heating the aerosol-generating material, to thereby produce an aerosol; a switching device for receiving a varying current from a constant voltage source and flowing it through the inductive element to cause inductive heating of the current-collecting structure; And a temperature detector configured, in use, to determine the temperature of the current-collecting structure based on the frequency at which the LC circuit operates. 2. The instrument of claim 1, wherein the temperature detector is configured, in use, to determine the temperature of the current-collecting structure based on direct current from a direct current source in addition to the frequency at which the resonant LC circuit operates. 3. The instrument of claim 2, wherein the temperature detector is configured, in use, to determine the temperature of the current-collecting structure based on the DC voltage from the DC voltage source in addition to the specified frequency at which the resonant LC circuit operates and the DC current from DC source when using. 4. The device according to any one of paragraphs. 1-3, in which the LC circuit is a parallel LC circuit containing a capacitive element in parallel with an inductive element. 5. The device according to claim 3 or 4, in which the temperature detector is configured to determine the effective group resistance of the inductive element and the current-collecting structure based on the frequency at which the resonant LC circuit operates, direct current from a direct current source and constant voltage from a direct current source voltage and with the ability to determine the temperature of the current-collecting structure based on the obtained effective group resistance. 6. The instrument of claim 5, wherein the temperature detector is configured to determine the temperature of the susceptor structure based on the calibration values of the effective group resistance of the inductive element and the susceptor structure and the indicated temperature of the susceptor structure. 7. An instrument according to claim 6 wherein the calibration is based on a polynomial equation, preferably a third order polynomial equation. 8. The device according to any one of paragraphs. 5-7, in which the temperature detector is configured to determine the effective group resistance r using the formula: , where V _s is the DC voltage, I _s is the DC current, C is the capacitance of the resonant LC circuit, and f ₀ is the frequency at which the resonant LC circuit operates. 9. An apparatus according to any one of the preceding claims, wherein the frequency at which the resonant LC circuit operates is the resonant frequency of the resonant LC circuit. 10. The device according to any of the preceding claims, wherein the switching device is configured to switch between the first state and the second state, and the frequency at which the LC circuit operates is determined based on the determination of the frequency at which the switching device switches between the first state and the second state. state. 11. The device of claim 10, wherein the switching device comprises one or more transistors, and the frequency at which the LC circuit operates is determined by measuring the period with which one of the transistors switches between an on state and an off state. 12. An instrument according to any one of the preceding claims, also comprising a frequency-to-voltage converter configured to output a voltage value indicative of the frequency at which the LC circuit is operating. 13. Apparatus according to any one of the preceding claims, wherein the DC voltage and/or DC current are calculated values. 14. An instrument according to any one of the preceding claims, wherein the values obtained for DC voltage and/or DC current are values measured using said instrument. 15. The device according to any one of paragraphs. 6-14, wherein the calibration of the values between the effective group resistance and the temperature of the current collector is one of a plurality of calibrations between the effective group resistance and the temperature of the current collector, and the temperature detector is configured to select one of the plurality of calibrations for use in determining the temperature of the current collector based on values of effective group resistance. 16. The instrument of claim 15, further comprising a temperature sensor configured to measure the temperature associated with the current-collecting structure prior to being heated by the inductive element, wherein the temperature detector is configured to use the temperature obtained by the temperature sensor to select a calibration. 17. The apparatus of claim 16, wherein the temperature sensed by the temperature sensor is the ambient temperature for the aerosol generating device. 18. The apparatus of claim 16, wherein the aerosol receiving device comprises a chamber for receiving the current-collecting structure, such as a chamber for receiving a consumable containing the current-collecting structure, and the temperature measured by the temperature sensor is the temperature of the chamber. 19. The device according to any one of paragraphs. 16-18, in which the temperature determiner is configured to determine the value of the effective group resistance corresponding to the temperature measured by the temperature sensor, and select a calibration from a plurality of calibrations based on a comparison between the temperature measured by the temperature sensor and the temperature given by each calibration from the specified set of calibrations , using the effective group resistance value corresponding to the temperature measured by the temperature sensor. 20. The device according to any one of paragraphs. 15-19, in which each calibration is a calibration curve, or a polynomial equation, or a set of calibration values in a look-up table. 21. The device according to any one of paragraphs. 15-20, wherein the temperature detector is configured to perform a calibration selection each time the aerosol generating device is turned on or each time the aerosol generating device enters an aerosol generating mode. 22. The apparatus of claim 10, wherein the switching device is configured to switch between the first state and the second state in response to voltage fluctuations in the resonant circuit operating at the resonant frequency of the resonant circuit, thereby maintaining a varying current at the resonant frequency of the resonant circuit. 23. The device according to claim 22, in which the switching device comprises a first transistor and a second transistor, and if the switching device is in the first state, then the first transistor is off and the second transistor is on, and if the switching device is in the second state, then the first transistor on and the second transistor is off. 24. The device according to claim 23, in which the first transistor and the second transistor contain a first terminal for turning this transistor on and off, a second terminal and a third terminal, and the switching device is configured so that the first transistor switches from an on state to an off state if the voltage on the second output of the second transistor is less than or equal to the threshold switching voltage of the first transistor. 25. The device according to claim 23 or 24, in which the first transistor and the second transistor contain a first terminal for turning this transistor on and off, a second terminal and a third terminal, and the switching device is configured so that the second transistor switches from an on state to an off state if the voltage at the second output of the first transistor is less than or equal to the threshold switching voltage of the second transistor. 26. The device according to any one of paragraphs. 23-25, wherein the resonant circuit also comprises a first diode and a second diode, wherein the first terminal of the first transistor is connected to the second terminal of the second transistor through the first diode, and the first terminal of the second transistor is connected to the second terminal of the first transistor through the second diode, thereby the first the terminal of the first transistor is at low voltage when the second transistor is on, and the first terminal of the second transistor is at low voltage when the first transistor is on. 27. The device of claim 26, wherein the switching device is configured such that the first transistor switches from an on state to an off state if the voltage at the second terminal of the second transistor is less than or equal to the switching threshold voltage of the first transistor plus the bias voltage of the first diode. 28. The device of claim 26 or 27, wherein the switching device is configured such that the second transistor switches from an on state to an off state if the voltage at the second terminal of the first transistor is less than or equal to the switching threshold voltage of the second transistor plus the bias voltage of the second diode. 29. Apparatus according to any one of the preceding claims, wherein the first terminal of the constant voltage source is connected to first and second points in the resonant circuit, the first point and second point being electrically located respectively on one side and the other of the inductive element. 30. The device according to any one of the previous claims, containing at least one choke located between the DC voltage source and the inductive element. 31. An aerosol generating device, comprising a device for determining the temperature of a pantograph according to any one of the preceding paragraphs.