AEROSOL-GENERATING SYSTEM WITH RESONANT CIRCUIT FOR CARTRIDGE RECOGNITION

Abstract

An aerosol-generating system is provided, including: a cartridge including an aerosol-forming substrate; a resonant circuit, the cartridge including at least part of the resonant circuit, the circuit being configured to resonate at a predetermined resonant frequency associated with an identity of the cartridge; and an aerosol-generating device including: a housing to removably receive the cartridge, a power source to supply power to the cartridge, and control circuitry including a controller configured to determine a resonant frequency of the resonant circuit when the cartridge is received by the device, and identify the cartridge based on the determined frequency, the cartridge having a connection end to connect the cartridge to the device and including electrical contacts to electrically connect the cartridge to the device, and the device having a connection end to connect the device to the cartridge and including electrical contacts configured to electrically connect the device to the cartridge.

Claims

1.-17. (canceled)

18. An aerosol-generating system, comprising: a cartridge including an aerosol-forming substrate; a resonant circuit, wherein the cartridge comprises at least a portion of the resonant circuit, wherein the resonant circuit is configured to resonate at a predetermined resonant frequency, and wherein the predetermined resonant frequency is associated with an identity of the cartridge; and an aerosol-generating device including: a housing configured to removably receive the cartridge, a power source configured to supply power to the cartridge, and control circuitry comprising a controller configured to: determine a resonant frequency of the resonant circuit when the cartridge is received by the aerosol-generating device, and identify the cartridge based on the determined resonant frequency, wherein the cartridge has a connection end configured to connect the cartridge to the aerosol-generating device, the connection end of the cartridge comprising electrical contacts configured to electrically connect the cartridge to the aerosol-generating device, and wherein the aerosol-generating device has a connection end configured to connect the aerosol-generating device to the cartridge, the connection end of the aerosol-generating device comprising electrical contacts configured to electrically connect the aerosol-generating device to the cartridge.

19. The aerosol-generating system according to claim 18, wherein the cartridge further includes an electric heater configured to heat the aerosol-forming substrate, and wherein the resonant circuit comprises the electric heater.

20. The aerosol-generating system according to claim 18, wherein the resonant circuit comprises a capacitor and an inductor.

21. The aerosol-generating system according to claim 20, wherein the cartridge comprises the inductor.

22. The aerosol-generating system according to claim 18, wherein the resonant circuit comprises a capacitor and an inductor, wherein the cartridge further includes an electric heater configured to heat the aerosol-forming substrate, wherein the resonant circuit comprises the electric heater, and wherein the electric heater comprises a coil and forms the inductor of the resonant circuit.

23. The aerosol-generating system according to claim 21, wherein the capacitor of the resonant circuit is connected in parallel with the inductor.

24. The aerosol-generating system according to claim 20, wherein the cartridge comprises the capacitor.

25. The aerosol-generating system according to claim 18, wherein the cartridge comprises the resonant circuit.

26. The aerosol-generating system according to claim 20, wherein the aerosol-generating device comprises the capacitor.

27. The aerosol-generating system according to claim 18, wherein the resonant circuit comprises a capacitor, and the predetermined resonant frequency of the resonant circuit is dependent on a capacitance of the capacitor and a parasitic inductance of the resonant circuit.

28. The aerosol-generating system according to claim 18, wherein the control circuitry is further configured to form an oscillator with the resonant circuit, the oscillator being configured to generate an oscillating signal with a frequency at the predetermined resonant frequency of the resonant circuit.

29. The aerosol-generating system according to claim 28, wherein the control circuitry is further configured to measure the frequency of the oscillating signal from the oscillator.

30. A cartridge for an aerosol-generating system, the cartridge comprising: an aerosol-forming substrate; an electric heater; a connection end configured to connect the cartridge to an aerosol-generating device, the connection end of the cartridge comprising electrical contacts configured to electrically connect the cartridge to the aerosol-generating device; and a resonant circuit, wherein the resonant circuit is configured to resonate at a predetermined resonant frequency, and wherein the predetermined resonant frequency is associated with an identity of the cartridge.

31. The cartridge according to claim 30, wherein the resonant circuit comprises a capacitor and an inductor.

32. The cartridge according to claim 31, wherein the electric heater comprises a coil and forms the inductor of the resonant circuit.

33. An aerosol-generating device for a cartridge including a resonant circuit, the aerosol-generating device including: a housing configured to removably receive the cartridge; a power source configured to supply power to the cartridge; a connection end configured to connect the aerosol-generating device to a cartridge, the connection end of the aerosol-generating device comprising electrical contacts configured to electrically connect the aerosol-generating device to the cartridge; and control circuitry comprising a controller configured to: determine a resonant frequency of the resonant circuit when the cartridge is received by the aerosol-generating device, and identify the cartridge based on the determined resonant frequency.

34. The aerosol-generating device according to claim 33, wherein the control circuitry is further configured to form an oscillator with the resonant circuit of the cartridge, the oscillator being configured to generate an oscillating signal with a frequency at the predetermined resonant frequency of the resonant circuit.

Description

[0173] Examples will now be further described with reference to the figures in which:

[0174] FIG. 1 shows a schematic illustration of an aerosol-generating system including an aerosol-generating device and a cartridge removably received by the aerosol-generating device in accordance with an example of the present disclosure;

[0175] FIG. 2 shows a block diagram of the main electrical components of the aerosol-generating system of FIG. 1;

[0176] FIG. 3 shows a schematic circuit diagram of the electrical circuit of the aerosol-generating system of FIG. 1;

[0177] FIG. 4 shows a schematic circuit diagram of an alternative example of an electrical circuit suitable for the aerosol-generating system of FIG. 1;

[0178] FIG. 5 shows a schematic illustration of an aerosol-generating system including an aerosol-generating device and a cartridge removably received by the aerosol-generating device in accordance with another example of the present disclosure;

[0179] FIG. 6 shows a block diagram of the main electrical components of the aerosol-generating system of FIG. 5; and

[0180] FIG. 7 shows a schematic circuit diagram of the electrical circuit of the aerosol-generating system of FIG. 1.

[0181] FIG. 1 shows a schematic illustration of an example of an aerosol-generating system in accordance with the present invention. The aerosol-generating system comprises two main components, a cartridge 100 and a main body part 200. A connection end 115 of the cartridge 100 is removably connected to a corresponding connection end 205 of the main body part 200. The main body part 200 contains a battery 210, which in this example is a rechargeable lithium ion battery, and control circuitry 220. The aerosol-generating system is portable and has a size comparable to a conventional cigar or cigarette. A mouthpiece is arranged at the end of the cartridge 100 opposite the connection end 115.

[0182] The cartridge 100 comprises a housing 105 containing a heater assembly 120 and a liquid storage compartment having a first portion 130 and a second portion 135. A liquid aerosol-forming substrate is held in the liquid storage compartment. Although not illustrated in FIG. 1, the first portion 130 of the liquid storage compartment is connected to the second portion 135 of the liquid storage compartment so that liquid in the first portion 130 can pass to the second portion 135. The heater assembly 120 receives liquid from the second portion 135 of the liquid storage compartment. In this embodiment, the heater assembly 120 comprises a fluid permeable heating element.

[0183] An air flow passage 140, 145 extends through the cartridge 100 from an air inlet 150 formed in a side of the housing 105 past the heater assembly 120 and from the heater assembly 120 to a mouthpiece opening 110 formed in the housing 105 at an end of the cartridge 100 opposite to the connection end 115.

[0184] The components of the cartridge 100 are arranged so that the first portion 130 of the liquid storage compartment is between the heater assembly 120 and the mouthpiece opening 110, and the second portion 135 of the liquid storage compartment is positioned on an opposite side of the heater assembly 100 to the mouthpiece opening 110. In other words, the heater assembly 120 lies between the two portions 130, 135 of the liquid storage compartment and receives liquid from the second portion 135. The first portion 130 of liquid storage compartment is closer to the mouthpiece opening 110 than the second portion 135 of the liquid storage compartment. The air flow passage 140, 145 extends past the heater assembly 110 and between the first 130 and second 135 portion of the liquid storage compartment.

[0185] The main body part 200 comprises a housing 202 containing the battery 210 and control circuitry 220.

[0186] The system is configured so that a user can puff or draw on the mouthpiece opening 110 of the cartridge to draw aerosol into their mouth. In operation, when a user puffs on the mouthpiece opening 110, air is drawn through the airflow passage 140, 145 from the air inlet 150, past the heater assembly 120, to the mouthpiece opening 110. The control circuitry 220 controls the supply of electrical power from the battery 210 to the cartridge 100 when the system is activated. This in turn controls the amount and properties of the vapour produced by the heater assembly 120. The control circuitry 220 may include an airflow sensor (not shown) and the control circuitry 220 may supply electrical power to the heater assembly 120 when user puffs on the cartridge 100 are detected by the airflow sensor. This type of control arrangement is well established in aerosol-generating systems such as inhalers and e-cigarettes. So when a user puffs on the mouthpiece opening 110 of the cartridge 100, the heater assembly 120 is activated and generates a vapour that is entrained in the air flow passing through the air flow passage 140. The vapour cools within the airflow in passage 145 to form an aerosol, which is then drawn into the user's mouth through the mouthpiece opening 110.

[0187] In operation, the mouthpiece opening 110 is typically the highest point of the system. The construction of the cartridge 100, and in particular the arrangement of the heater assembly 120 between first and second portions 130, 135 of the liquid storage compartment, is advantageous because it exploits gravity to ensure that the liquid substrate is delivered to the heater assembly 120 even as the liquid storage compartment is becoming empty, but prevents an oversupply of liquid to the heater assembly 120 which might lead to leakage of liquid into the air flow passage 140.

[0188] FIG. 2 shows a block diagram illustrating the main electric and electronic components of the aerosol-generating system of FIG. 1, comprising the cartridge 100 and the aerosol-generating device 200. The cartridge 100 comprises the electric heater 120 connected in parallel with a resonant circuit 155 (not shown in FIG. 1). The resonant circuit 155 is configured to resonate at a predetermined resonant frequency, which is associated with an identity of the cartridge 100. By determining the resonant frequency of the resonant circuit 155, the aerosol-generating device 200 is able to identify the cartridge 100, and the aerosol-forming substrate contained in the cartridge 100, and control the supply of power to the electric heater 120 to generate the appropriate temperature to generate the optimal aerosol from the aerosol-forming substrate.

[0189] The resonant circuit 155 comprises an inductor L1 and a capacitor C1 connected in series. The resonant circuit 155 is connected in parallel across the electric heater 120.

[0190] With this arrangement of the resonant circuit 155 and the electric heater 120, only two electrical connections are required between the cartridge 100 to the aerosol-generating device 200. The two electrical connections can be used to supply power to the heater 120 for heating the aerosol-forming substrate, and to provide an input signal to the resonant circuit 155, and to receive an output signal from the resonant circuit 155 for determining the resonant frequency of the resonant circuit 155, and determining the identity of the cartridge 100. Accordingly, the cartridge 100 comprises a single pair of electrical contacts 160, for electrical connection with the aerosol-generating device 200.

[0191] The aerosol-generating device 200 comprises the battery 210, which acts as a power source, and the control circuitry 220, which controls the supply of power from the battery 210 to the cartridge 100. The aerosol-generating device 200 further comprises a single pair of electrical contacts 260, complementary to the pair of electrical contacts 160 of the cartridge 100, for electrical connection of the aerosol-generating device 200 with the cartridge 100.

[0192] The control circuitry 220 comprises a microcontroller (MCU) 230. The microcontroller 230 is configured to control the supply of electrical power to the electric heater 120, which is shown in FIG. 2 by a DC voltage source V1 and a switch S1, which may be a transistor or other suitable electronic switch. The microcontroller 230 modulates the DC voltage source V1 through pulse width modulation (PWM) to provide power to the electric heater 120 in a series of pulses. The power to the electric heater 120 is controlled by controlling the duty cycle of the series of pulses, which controls the temperature of the electric heater 120. No passive components which can generate heat, such as resistors or inductors, are connected in series between the DC voltage source V1 and the electric heater 120. This helps to reduce energy losses during heating of the electric heater 120.

[0193] The control circuitry 220 also comprises identification circuitry 240, which is connected to the resonant circuit 155. The microcontroller 230 is also configured to control the supply of electrical power to the resonant circuit 155, via the identification circuitry 240. The configuration of the microcontroller 230 for controlling the supply of electrical power to the resonant circuit 155 via the identification circuitry 240 is shown in FIG. 2 by a DC voltage source V2 and a switch S2, which may be a transistor or other suitable electronic switch. The microcontroller 230 is further configured to receive an output signal from the identification circuitry 240, and determine the resonant frequency of the resonant circuit 155 from the output signal of the identification circuitry 240, as described in more detail below in relation to FIG. 3.

[0194] Although two separate voltage sources V1 and V2 are shown separate from the microcontroller 230 in FIG. 2, it will be appreciated that in practice both of these voltage sources are provided by the microcontroller 230. It will also be appreciated in some embodiments the aerosol-generating device may actually comprise two separate power sources, such as two separate batteries, which may separately form the voltage sources V1 and V2.

[0195] FIG. 3 shows a schematic circuit diagram of the electrical circuit of the aerosol-generating system of FIGS. 1 and 2.

[0196] The cartridge 100 comprises the electric heater 120 and the resonant circuit 155 connected in parallel. The electric heater 120 is a resistive heater, and as such, is indicated in FIG. 3 as RH. The resonant circuit 155 comprises the capacitor C1 and the inductor L1 connected in series.

[0197] In this embodiment, the resistive heater RH is taken to have no inductance, and as such, is not shown forming part of the resonant circuit 155. However, it will be appreciated that in other embodiments the resistive heater RH may have an inductance and may form part of the resonant circuit 155.

[0198] The cartridge 100 comprises a pair of electrical contacts 160, which electrically connect the cartridge 100 to the aerosol-generating device 200 when the cartridge 100 is received by the aerosol-generating device 200, via a complementary pair of electrical contacts 260 on the aerosol-generating device 200.

[0199] The aerosol-generating device 200 comprises control circuitry 220, including the microcontroller 230 and the identification circuitry 240. The battery 210 of the aerosol-generating device 200 is not shown in FIG. 3, but the first DC voltage source V1, switch S1, the second DC voltage source V2, and the switch S2 illustrated above in FIG. 2 are shown.

[0200] As shown in FIG. 3, the first voltage source V1 is directly connected to the electric heater RH. It will be appreciated that in other embodiments the voltage source V2 may be indirectly connected to the electric heater RH, such as via a resistor. The microcontroller 230 and first voltage source V1 are configured to provide pulses of power to the electric heater RH for heating the aerosol-forming substrate in the cartridge 100. The duty cycle of the pulses of power from the first voltage source V1 is controlled by the microcontroller 230 via pulse width modulation (PWM) to control the temperature of the electric heater RH. The capacitor C1 of the resonant circuit, which is connected in parallel with the electric heater RH, prevents DC current from being drawn through the inductor L1, and hence minimises current losses through the inductor L1 when the pulses of power are supplied from the first voltage source V1 to the electric heater RH for heating the aerosol-forming substrate.

[0201] Also as shown in FIG. 3, the second voltage source V2 is directly connected to the identification circuitry 240. The identification circuitry 240 is connected to the resonant circuit 155 in the cartridge 100 via the same rail that connects the first voltage source V1 to the heater RH. An output of the identification circuitry 240 is connected to the microcontroller 230.

[0202] In this embodiment, the identification circuit 240 is configured as an oscillator, which outputs a square wave signal having a frequency equal to the predetermined resonant frequency of the resonant circuit 155.

[0203] The identification circuit 240 comprises a voltage comparator U5. In this embodiment the comparator U5 is an LM311 from Texas Instruments Incorporated, however, it will be appreciated that other comparators may be used.

[0204] The second voltage source V2 is connected to the positive supply terminal (pin 8) of the voltage comparator U5. The second voltage source V2 is also connected to the non-inverting input (pin 2) of the voltage comparator U5, via a voltage divider comprising equal 100 kiloohm resistors R3 and R4. A feedback loop from the output (pin 7) of the voltage comparator U5 to the non-inverting input (pin 2) of the voltage comparator U5 is provided, via a 10 kiloohm resistor R2. A 1 kiloohm resistor R1 is also provided between the second voltage source V2, the output (pin 7) of the voltage comparator U5, and the resistor R2, in order to provide a voltage drop between the second voltage supply V2 and the output of the voltage comparator U5. A 22 nanofarad capacitor C5, is connected to the inverting input (pin 3) of the voltage comparator U5, and is also connected to the output (pin 7) of the comparator U5 via a resistor R5 of 100 kiloohms. The non-inverting input (pin 2) of the voltage comparator U5 is also connected to the cartridge 100 via a 100 nanofarad capacitor C2, arranged in parallel with a 10 microfarad electrolytic capacitor C4. The capacitors C2 and C4 are decoupling capacitors that permit AC oscillations to pass between the resonant circuit 155 and the identification circuit 240, while preventing DC signals from passing between the resonant circuit 155 and the identification circuit 240. The capacitor C2 is provided to permit the passage of high frequencies, and the electrolytic capacitor C4 is provided to permit the passage of low frequencies.

[0205] When the switch S2 is closed, and the second voltage source V2 is connected to the identification circuit, the voltage at the non-inverting input of the voltage comparator U5 is about half V2 (which is about 1.5 Volts if we use an example where V2 is about 3 Volts), due to the voltage divider formed by the equal resistors R3 and R4. This input results in an output from the voltage comparator U5 of about V2 (about 3 Volts). The output of the voltage comparator U5 charges the capacitor C5 through resistor R5, until the voltage at the inverting input of the voltage comparator U5 is also about half V2 (about 1.5 Volts). As the inverting input of the voltage comparator U5 reaches about half V2 (about 1.5 Volts), which is the same voltage as the non-inverting input, the output of the voltage comparator U5 switches to a low level, inducing a transient voltage into the identification circuit. This transient voltage is fed to the resonant circuit 155 in the cartridge 100 via the resistor R2 and the capacitors C2 and C4, and maintain the resonant circuit 155 to resonate at the predetermined resonant frequency of the resonant circuit 155. The resonating resonant circuit 155 affects the voltage at the non-inverting input of the voltage comparator U5, which causes a square wave to be generated at the output of the voltage comparator U5 with a frequency at the predetermined resonant frequency of the resonant circuit 155. The square wave output from the voltage comparator U5 is fed back to the resonant circuit 155 through resistor R2 and capacitor C2, which sustains the resonant oscillation of the resonant circuit. The square wave output from the voltage comparator U5 is also fed back to the capacitor C5 through the resistor R5, which in turn induces an AC signal at the inverting input of the voltage comparator U5. The phase difference between the output from the voltage comparator U5 and the AC signal at the inverting input of the voltage comparator U5 causes the output of the voltage comparator U5 to be a square wave signal.

[0206] The square wave output from the voltage comparator U5 is supplied to the microcontroller 230, which is configured to determine the frequency of the square wave output.

[0207] In this example, the microcontroller 230 is configured to determine the resonant frequency of the resonant circuit 155 by determining the frequency of the square wave output of the identification circuit 240 by counting the number of oscillations or pulses in a predetermined time period of around 100 milliseconds. It will be appreciated that other predetermined time periods may be used, such as between about 10 milliseconds and about 200 milliseconds. It will also be appreciated that in other embodiments the microcontroller 230 may be configured to determine the resonant frequency of the resonant circuit 155 by determining the frequency of the square wave output by measuring the duration of one or more oscillations or pulses.

[0208] In this example, the microcontroller 230 is configured to disconnect the first voltage source V1 from the electric heater RH, via the switch S1, before the second voltage source V2 is connected to the identification circuit 240, via the switch S2. Advantageously, this reduces interference from the first voltage source V1 in the square wave output of the identification circuitry 240.

[0209] In this example, the microcontroller 230 comprises a memory (not shown) storing a look-up table comprising a plurality of reference resonant frequency values, with each reference resonant frequency value being associated with a particular cartridge identity, and power value. Each associated cartridge identity relates to the particular aerosol-forming substrate contained in the cartridge. Each associated power value corresponds to the power required to be supplied to the electric heater to generate the optimal aerosol from the particular aerosol-forming substrate contained in the cartridge.

[0210] The microcontroller 230 is configured to determine the identity of the cartridge 100 based on the determined resonant frequency by comparing the determined resonant frequency to the plurality of reference resonant frequency values stored in the look-up table.

[0211] When the determined resonant frequency matches one of the stored reference resonant frequency values, the microcontroller 230 is configured to determine the identity of the cartridge 100 to be the cartridge identity associated with the matched reference resonant frequency value in the look-up table. The microcontroller 230 is further configured to control the first voltage source V1 to supply power to the electric heater RH in the cartridge 100 in accordance with the power value associated with cartridge identity in the look-up table.

[0212] When the determined resonant frequency does not match any of the stored reference resonant frequency values in the look-up table, the microcontroller 230 is configured to determine that the cartridge is an unauthorised cartridge. When the microcontroller 230 determines that a cartridge is unauthorised, the microcontroller 230 is configured to prevent power from being supplied from the first voltage source V1 to the electric heater RH to heat the aerosol-forming substrate in the cartridge.

[0213] FIG. 4 shows a schematic circuit diagram of an alternative example of an electrical circuit suitable for the aerosol-generating system of FIG. 1. The example circuit of FIG. 4 is substantially the same as the example circuit of FIG. 3, and as such, equivalent features have been given equivalent reference numerals.

[0214] The only difference between the example circuit of FIG. 3 and the example circuit of FIG. 4 is that the resonant circuit 155 of the example circuit of FIG. 4 does not comprise the inductor L1 of the example circuit of FIG. 3. The example circuit of FIG. 4 uses the parasitic inductance Lp of the resonant circuit 155, which is primarily comprised of the parasitic inductance of the capacitor C1, instead of the inductor L1 of the example circuit of FIG. 3. In this embodiment, the heater RH is considered to have no inductance. However, it will be appreciated that in most embodiments, the heater RH will have an appreciable inductance, and will contribute to the parasitic inductance Lp of the resonant circuit 155. In some embodiments, the parasitic inductance of the heater RH is significantly higher than the parasitic inductance of the other components in the resonant circuits, and in these embodiments the resonant frequency of the resonant circuit is primarily determined by the capacitance of the capacitor C1 and the inductance of the heater RH.

[0215] The parasitic inductance Lp of the resonant circuit 155 is typically significantly lower than the inductance of a “real” inductor, such as the inductor L1 of the example circuit of FIG. 3. Accordingly, the resonant frequency of the resonant circuit 155 of the example circuit of FIG. 4 is typically significantly higher than the resonant frequency of a resonant circuit including a “real” inductor, such as the example circuit of FIG. 3.

[0216] Advantageously, using the parasitic inductance of the resonant circuit without providing a “real” inductor may reduce the complexity of the resonant circuit, and reduce the cost of the components of the cartridge.

[0217] FIG. 5 shows a schematic illustration of another example of an aerosol-generating system in accordance with the present invention. The aerosol-generating system of FIGS. 5, 6 and 7 is substantially similar to the aerosol-generating system of FIG. 1, and as such, equivalent features have been given equivalent reference numerals.

[0218] The aerosol-generating system comprises two main components, a cartridge 100 and a main body part 200. A connection end 115 of the cartridge 100 is removably connected to a corresponding connection end 205 of the main body part 200. The main body part comprises a battery 210, which in this example is a rechargeable lithium ion battery, and control circuitry 220. The aerosol-generating system is portable and has a size comparable to a conventional cigar or cigarette. A mouthpiece is arranged at the end of the cartridge 100 opposite the connection end 115.

[0219] The cartridge 100 comprises a housing 105 containing a heater assembly 120 and a liquid storage compartment 130. A liquid aerosol-forming substrate is held in the liquid storage compartment.

[0220] In this embodiment, the heater assembly 120 comprises a heating element in the form of heating coil. The heater assembly 120 receives liquid from the liquid storage compartment 130 via a capillary wick 122. One end of the capillary wick 122 is positioned in the liquid storage compartment 130 and the other end of the capillary wick 122 is positioned outside of the liquid storage compartment 130 and is surrounded by the heating coil 120.

[0221] An air flow passage 140, 145 extends through the cartridge 100 from an air inlet 150 formed in a side of the housing 105 past the heater assembly 120 and from the heater assembly 120 to a mouthpiece opening 110 formed in the housing 105 at an end of the cartridge 100 opposite to the connection end 115.

[0222] The main body part 200 comprises a housing 202 containing the battery 210 and control circuitry 220.

[0223] The system is configured so that a user can puff or draw on the mouthpiece opening 110 of the cartridge to draw aerosol into their mouth. In operation, when a user puffs on the mouthpiece opening 110, air is drawn through the airflow passage 140, 145 from the air inlet 150, past the heater assembly 120, to the mouthpiece opening 110. The control circuitry 220 controls the supply of electrical power from the battery 210 to the cartridge 100 when the system is activated. This in turn controls the amount and properties of the vapour produced by the heater assembly 120. The control circuitry 220 may include an airflow sensor (not shown) and the control circuitry 220 may supply electrical power to the heater assembly 120 when user puffs on the cartridge 100 are detected by the airflow sensor. This type of control arrangement is well established in aerosol-generating systems such as inhalers and e-cigarettes. So when a user puffs on the mouthpiece opening 110 of the cartridge 100, the heater assembly 120 is activated and generates a vapour that is entrained in the air flow passing through the air flow passage 140. The vapour cools within the airflow in passage 145 to form an aerosol, which is then drawn into the user's mouth through the mouthpiece opening 110.

[0224] FIG. 6 shows a block diagram illustrating the main electric and electronic components of the aerosol-generating system of FIG. 5, comprising the cartridge 100 and the aerosol-generating device 200.

[0225] The cartridge 100 comprises the electric heater 120, in the form of a heater coil. Due to the geometry of the heater coil 120, the heater coil 120 forms an inductor, and as such, the heater coil 120 is also referred to in FIGS. 6 and 7 as LH.

[0226] The aerosol-generating device 200 comprises a capacitor C1. When the cartridge 100 is received by the aerosol-generating device 200, the heater coil LH and the capacitor C1 are connected in parallel, and form a resonant circuit 155 (not shown in FIG. 5). The resonant circuit 155 is configured to resonate at a predetermined resonant frequency, which is associated with an identity of the cartridge 100. By determining the resonant frequency of the resonant circuit 155, the aerosol-generating device 200 is able to identify the cartridge 100, and the aerosol-forming substrate contained in the cartridge 100, and control the supply of power to the electric heater 120 to generate the appropriate temperature to generate the optimal aerosol from the aerosol-forming substrate.

[0227] The resonant frequency of the resonant circuit 155 is associated with the identity of the cartridge through the inductance of the heater coil LH. The inductance of the heater coil LH may be varied between cartridges containing different aerosol-forming substrates, such that the resonant frequency of the resonant circuit 155 for each cartridge is associated with the liquid aerosol-forming substrate in the cartridge. Advantageously, dividing components of the resonant circuit between the aerosol-generating device and the cartridge may reduce the number of components in the cartridge, lowering the complexity and cost of the cartridge.

[0228] With this arrangement of the heater coil LH and the capacitor C1, only two electrical connections are required between the cartridge 100 and the aerosol-generating device 200. The two electrical connections can be used to supply power to the heater coil LH for heating the aerosol-forming substrate, and to provide an input signal to the resonant circuit 155, and to receive an output signal from the resonant circuit 155 for determining the resonant frequency of the resonant circuit 155, and determining the identity of the cartridge 100. Accordingly, the cartridge 100 comprises a single pair of electrical contacts 160, for electrical connection with the aerosol-generating device 200.

[0229] The aerosol-generating device 200 comprises the battery 210, which acts as a power source, and the control circuitry 220, which controls the supply of power from the battery 210 to the cartridge 100. The aerosol-generating device 200 further comprises a single pair of electrical contacts 260, complementary to the pair of electrical contacts 160 of the cartridge 100, for electrical connection of the aerosol-generating device 200 with the cartridge 100.

[0230] The control circuitry 220 comprises a microcontroller (MCU) 230. The microcontroller 230 is configured to control the supply of electrical power to the heater coil LH, which is shown in FIG. 6 by a DC voltage source V1 and a switch S1, which may be a transistor or other suitable electronic switch. The microcontroller 230 modulates the DC voltage source V1 through pulse width modulation (PWM) to provide power to the heater coil in a series of pulses. The power to the heater coil LH is controlled by controlling the duty cycle of the series of pulses, which controls the temperature of the heater coil LH. No passive components which can generate heat, such as resistors or inductors, are connected in series between the DC voltage source V1 and the heater coil LH. This helps to reduce energy losses during heating of the heater coil LH.

[0231] The control circuitry 220 also comprises identification circuitry 240, which is connected to the resonant circuit 155. The microcontroller 230 is also configured to control the supply of electrical power to the resonant circuit 155, via the identification circuitry 240. The configuration of the microcontroller 230 for controlling the supply of electrical power to the resonant circuit 155 via the identification circuitry 240 is shown in FIG. 6 by a DC voltage source V2 and a switch S2, which may be a transistor or other suitable electronic switch. The microcontroller 230 is further configured to receive an output signal from the identification circuitry 240, and determine the resonant frequency of the resonant circuit 155 from the output signal of the identification circuitry 240, as described above in relation to FIGS. 3 and 4.

[0232] Although two separate voltage sources V1 and V2 are shown separate from the microcontroller 230 in FIG. 6, it will be appreciated that in practice both of these voltage sources are provided by the microcontroller 230. It will also be appreciated in some embodiments the aerosol-generating device may actually comprise two separate power sources, such as two separate batteries, which may separately form the voltage sources V1 and V2.

[0233] FIG. 7 shows a schematic circuit diagram of an example of an electrical circuit suitable for the aerosol-generating system of FIG. 5. The example circuit of FIG. 7 is substantially the same as the example circuit of FIG. 3, and as such, equivalent features have been given equivalent reference numerals.

[0234] The first difference between the example circuit of FIG. 3 and the example circuit of FIG. 7 is that the resonant circuit 155 of the example circuit of FIG. 7 comprises a heater coil LH, which also forms the inductor of the resonant circuit 155. Accordingly, the resonant circuit 155 of the example circuit of FIG. 7 does not comprise the separate heater 120 and inductor L1 of the example circuit of FIG. 3.

[0235] The second difference between the example circuit of FIG. 3 and the example circuit of FIG. 7 is that the cartridge 100 does not comprise the entire resonant circuit 155. The cartridge 100 of the example circuit of FIG. 7 does not comprise the capacitor C1 of the resonant circuit 155. In the example circuit of FIG. 7, the aerosol-generating device comprises the capacitor C1 of the resonant circuit 155.

[0236] Advantageously, using the parasitic inductance of the resonant circuit without providing a “real” inductor may reduce the complexity of the resonant circuit, and reduce the cost of the components of the cartridge.

[0237] Advantageously, dividing components of the resonant circuit between the aerosol-generating device and the cartridge may reduce the number of components in the cartridge, lowering the complexity and cost of the cartridge.

[0238] For the purpose of the present description and of the appended claims, except where otherwise indicated, all numbers expressing amounts, quantities, percentages, and so forth, are to be understood as being modified in all instances by the term “about”. Also, all ranges include the maximum and minimum points disclosed and include any intermediate ranges therein, which may or may not be specifically enumerated herein. In this context, therefore, a number A is understood as A±{5%} of A. Within this context, a number A may be considered to include numerical values that are within general standard error for the measurement of the property that the number A modifies. The number A, in some instances as used in the appended claims, may deviate by the percentages enumerated above provided that the amount by which A deviates does not materially affect the basic and novel characteristic(s) of the claimed invention. Also, all ranges include the maximum and minimum points disclosed and include any intermediate ranges therein, which may or may not be specifically enumerated herein.