A control circuit for an aerosol generating device, a printed circuit board assembly, and an aerosol generating system

Abstract

A control circuit for an aerosol generating device is described. The control circuit includes an energy storage device terminal (B+) and a heater terminal (H+; H-). First and second semiconductor switches (Q1, Q2) are electrically connected in series between the energy storage device terminal (B+) and the heater terminal (H+) or between the heater terminal (H-) and ground. A microcontroller unit (20) of the control circuit has a first control terminal (22) and a second control terminal (24). The first control terminal (22) of the microcontroller unit (20) is electrically connected to a control terminal of the first semiconductor switch (Q1) by a first switch circuit (26). The second control terminal (24) of the microcontroller unit (20) is electrically connected to a control terminal of the second semiconductor switch (Q2) by a second switch circuit (28).

Description

[0001] A CONTROL CIRCUIT FOR AN AEROSOL GENERATING DEVICE, A PRINTED CIRCUIT BOARD ASSEMBLY, AND AN AEROSOL GENERATING SYSTEM

[0002] Technical Field

[0003] The present disclosure relates generally to a control circuit for an aerosol generating device, and in particular a device that is adapted to heat aerosol generating material to generate an aerosol for inhalation by a user. The aerosol generating device may comprise an energy storage device and a heater for heating the aerosol generating material. Alternatively, the heater may be part of a separate aerosol generating article where the aerosol generating device is adapted to receive the aerosol generating article in use. The aerosol generating material may also be part of the aerosol generating article.

[0004] The control circuit may be used to control the supply of power from the energy storage device to the heater. Consequently, the heating of the aerosol generating material may be controlled.

[0005] The present disclosure also relates generally to a printed circuit board assembly, and in particular a printed circuit board assembly that has a printed circuit board and electronic components that are mounted to the circuit board. The electronic components may implement the control circuit.

[0006] The present disclosure also relates generally to an aerosol generating system. The aerosol generating system may include an aerosol generating device that includes the control circuit, and optionally an aerosol generating article. The present disclosure is particularly applicable to a portable (hand-held) aerosol generating device.

[0007] Technical Background

[0008] Devices which heat, rather than burn, an aerosol generating material to produce an aerosol for inhalation have become popular with consumers in recent years. A commonly available reduced-risk or modified-risk device is the heated material aerosol generating device, or so-called heat-not-bum device. Devices of this type generate an aerosol or vapour by heating an aerosol generating material to a temperature typically in the range 150°C to 300°C. This temperature range is quite low compared to an ordinary cigarette. Heating the aerosol generating material to a temperature within this range, without burning or combusting the aerosol generating material, generates a vapour which typically cools and condenses to form an aerosol for inhalation by a user of the device.

[0009] The aerosol generating material may be a solid or liquid. For example, the aerosol generating article may include a solid or semi-solid substrate of plant derived material, such as tobacco, or it may include a wick and a heater to produce vapour from aerosol generating liquid stored in a capsule or tank. When a user operates the aerosol generating device, liquid that has soaked into the wick is heated by the heater, producing a vapour which cools and condenses to form an aerosol which may then be inhaled. An aerosol generating article (sometimes called a pod or cartridge) may be received in the aerosol generating device and may include a liquid store, a liquid transfer element (e.g., a wick) and a heater. Electrical contacts may provide an electrical connection between the heater and an energy storage device of the aerosol generating device. The energy storage device may be a rechargeable battery that may be charged from an external power source by a charging assembly of the aerosol generating device.

[0010] The supply of power from the energy storage device to the heater may be controlled by a control circuit. The control circuit will typically include only one semiconductor switch (e.g., a single metal-oxide-semi conductor field-effect transistor (MOSFET)) electrically connected between the energy storage device and the heater. Power is supplied to the heater when the semiconductor switch is switched on (i.e., in an on- state). The semiconductor switch may be switched on and off by a microcontroller unit (MCU) of the control circuit so as to control or regulate the supply of power to the heater. There is a need for an improved control circuit that avoids unexpected conditions if there is a critical fault with the semiconductor switch, for example a short-circuit fault. Summary of the Disclosure

[0011] According to a first aspect of the present disclosure, there is provided a control circuit for an aerosol generating device, the control circuit comprising: an energy storage device terminal electrically connectable to an energy storage device (e.g., to a rechargeable battery such as a lithium-ion secondary battery of the aerosol generating device); a heater terminal electrically connectable to a heater (e.g., to a heater of the aerosol generating device or a separate aerosol generating article that is received in the device in use); first and second semiconductor switches electrically connected in series between the energy storage device terminal and the heater terminal or between the heater terminal and ground (e.g., a ground plane of a printed circuit board assembly); and a microcontroller unit (MCU) having a first control terminal and a second control terminal; wherein the first control terminal of the MCU is electrically connected to a control terminal of the first semiconductor switch by a first switch circuit and the second control terminal of the MCU is electrically connected to a control terminal of the second semiconductor switch by a second switch circuit.

[0012] The first and second semiconductor switches may be P-channel MOSFETs, for example. The first and second semiconductor switches may be N-channel MOSFETs, for example. P-channel MOSFETs may be preferred if the first and second semiconductor switches are electrically connected between the energy storage device terminal and the heater terminal. N-channel MOSFETs may be preferred if the first and second semiconductor switches are electrically connected between the heater terminal (e.g., a negative heater terminal) and ground. Compared with bipolar transistors, MOSFETs typically have lower energy losses and faster switching. In addition, if the same MOSFET is used as both the first and second semiconductor switches, the procurement of electronic components for the control circuit is simplified. Assembly costs may be minimised and the continuity of assembly and production may be improved.

[0013] Electrically connecting the control terminals of the first and second semiconductor switches to different control terminals of the MCU improves safety. If there is a fault with the first control terminal of the MCU and / or with the first semiconductor switch itself, for example, it might be expected that the second control terminal of the MCU will continue to operate correctly so that at least the second semiconductor switch may still be controlled by the MCU, or vice versa. In particular, it allows at least one of the first and second semiconductor switches to be switched off by the MCU (i.e., switched to an off-state) to electrically isolate the heater terminal from the energy storage device terminal if necessary. The control circuit is particularly robust in a situation where one of the first and second semiconductor switches suffers from a short-circuit condition.

[0014] The MCU may be adapted to output a first control signal from the first control terminal for controlling the switching of the first semiconductor switch. The first semiconductor switch may be in the on-state if the first control signal has a low voltage level and may be in the off-state if the first control signal has a high voltage level. The MCU may also be adapted to output a second control signal from the second control terminal for controlling the switching of the second semiconductor switch. The second semiconductor switch may be in the on-state if the second control signal has a high voltage level and may be in the off-state if the second control signal has a low voltage level. Such an arrangement may be beneficial because if there is a fault with the MCU, it is most likely that the first and second control terminals will be at the same voltage level - i.e., the first and second control signals will both have a high voltage level or will both have a low voltage level. This means that at least one of the first and second semiconductor switches will be an off-state and the heater terminal will be electrically isolated from the energy storage device terminal.

[0015] The first switch circuit may comprise a first switch resistor. If the first semiconductor switch is a P-channel MOSFET, its gate terminal (control terminal) may be electrically connected to the first control terminal of the MCU by the first switch resistor. The first semiconductor switch will be in the on-state if the first control signal that is applied to its gate terminal has a low voltage level and it will be in the off-state if the first control signal has a high voltage level. If the first semiconductor switch is a N-channel MOSFET, its gate terminal (control terminal) may be electrically connected to the first control terminal of the MCU by the first switch resistor. The first semiconductor switch will be in the on-state if the first control signal that is applied to its gate terminal has a high voltage level and it will be in the off-state if the first control signal has a low voltage level.

[0016] The second switch circuit may comprise a third semiconductor switch. The third semiconductor switch may be electrically connected between the control terminal of the second semiconductor switch and ground. A control terminal of the third semiconductor switch may be electrically connected to the second control terminal of the MCU.

[0017] The third semiconductor switch may be a N-channel MOSFET or NPN bipolar transistor, for example. If the third semiconductor switch is an N-channel MOSFET, its gate terminal (control terminal) may be electrically connected to the second control terminal of the MCU, for example. The third semiconductor switch will be in the on- state if the second control signal that is applied to its gate terminal has a high voltage level and it will be in the off-state if the second control signal has a low voltage level. The third semiconductor switch may be a P-channel MOSFET or PNP bipolar transistor, for example. If the third semiconductor switch is a P-channel MOSFET, its gate terminal (control terminal) may be electrically connected to the second control terminal of the MCU, for example. The third semiconductor switch will be in the on- state if the second control signal that is applied to its gate terminal has a low voltage level and it will be in the off-state if the second control signal has a high voltage level. The MCU may therefore switch the third semiconductor switch on and off (i.e., between on- and off-states) by switching the second control signal between high and low voltage levels. If the second semiconductor switch is a P-channel MOSFET and the third semiconductor switch is an N-channel MOSFET, for example, the drain terminal of the third semiconductor switch may be electrically connected to the gate terminal (control terminal) of the second semiconductor switch, the source terminal of the third semiconductor switch may be electrically connected to ground, and the gate terminal of the third semiconductor switch may be electrically connected to the second control terminal of the MCU. If the second semiconductor switch is a P-channel MOSFET and the third semiconductor switch is an NPN bipolar transistor, for example, the collector terminal of the third semiconductor switch may be electrically connected to the gate terminal (control terminal) of the second semiconductor switch, the emitter terminal of the third semiconductor switch may be electrically connected to ground, and the base terminal of the third semiconductor switch may be electrically connected to the second control terminal of the MCU.

[0018] The source terminal of the second semiconductor switch may also be electrically connected to the gate terminal of the second semiconductor switch, preferably by means of a capacitor.

[0019] If the third semiconductor switch is an N-channel MOSFET, for example, it will be in the on-state if the second control signal that is applied to its gate terminal has a high voltage level and it will be in the off-state if the second control signal has a low voltage level. If the third semiconductor switch is an NPN bipolar transistor, for example, it will be in the on-state if the second control signal that is applied to its base terminal has a high voltage level and it will be in the off-state if the second control signal has a low voltage level. When the third semiconductor switch is in the on-state, the gate terminal of the second semiconductor switch is electrically connected to ground - i.e., it receives a low level signal at its gate terminal and the second semiconductor switch is also in the on-state if it is a P-channel MOSFET, for example. When the third semiconductor switch is in the off-state, the gate terminal of the second semiconductor switch is electrically isolated from ground and is electrically connected to its source terminal by the capacitor. The second semiconductor switch therefore receives a high level signal at its gate terminal and the second semiconductor switch is in the off-state if it is a P-channel MOSFET, for example. The MCU may therefore switch the second semiconductor switch on and off (i.e., between on- and off-states) by switching the second control signal that is applied to the control terminal of the third semiconductor switch between high and low voltage levels.

[0020] It will therefore be understood that for such an arrangement, the first semiconductor switch will be in the on-state when the MCU outputs a low level signal from the first control terminal of the MCU (i.e., when the first control signal has a low voltage level) and will be in the off-state when the MCU outputs a high level signal from the first control terminal of the MCU (i.e., when the first control signal has a high voltage level). However, the second semiconductor switch will be in the off-state when the MCU outputs a low level signal from the second control terminal of the MCU (i.e., when the second control signal has a low voltage level) and in the on-state when the MCU outputs a high level signal from the second control terminal of the MCU (i.e., when the second control signal has a high voltage level). This is because when the second control signal has a high voltage level, the third semiconductor switch is also in the on-state and the gate terminal of the second semiconductor switch is electrically connected to ground through the third semiconductor switch. If there is a fault with the MCU which causes a low level signal to be output on both the first and second control terminals, it means that the first semiconductor switch will be in the on-state and the second semiconductor switch will be in the off-state. On the other hand, if the fault with the MCU causes a high level signal to be output on both the first and second control terminals, it means that the first semiconductor switch will be in the off-state and the second semiconductor switch will be in the on-state. In either case, the heater terminal will be electrically isolated from the energy storage device terminal. This may be contrasted with a known control circuit that has a single semiconductor switch electrically connected between the energy storage device terminal and the heater terminal, and where there is a risk that the semiconductor switch remains in the on-state if there is a fault with the MCU.

[0021] The second switch circuit may comprise a filter capacitor and a filter resistor. The second switch circuit may comprise a second switch resistor. The second switch resistor and the filter capacitor may be electrically connected in series between the control terminal of the third semiconductor switch and the second control terminal of the MCU. The filter resistor may be electrically connected to a junction between the filter capacitor and the control terminal of the third semiconductor switch. The filter resistor may also be electrically connected to ground. The filter capacitor and the filter resistor may form a high-pass filter to cut off low frequency noise which may cause unexpected switching of the third semiconductor switch. Alternatively, or additionally, other types of filter circuit (e.g., low-pass or band-pass filters) may be employed in the second switch circuit.

[0022] The first semiconductor switch may be electrically connected between the second semiconductor switch and the heater terminal. The second semiconductor switch may be electrically connected to the energy storage device terminal. If the first and second semiconductor switches are P-channel MOSFETs, for example, the drain terminal of the first semiconductor switch may be electrically connected to the heater terminal, e.g., to a positive heater terminal, the source terminal of the first semiconductor switch may be electrically connected to the drain terminal of the second semiconductor switch, and the source terminal of the second semiconductor switch may be electrically connected to the energy storage device terminal, e.g., a positive energy storage device terminal. If the first and second semiconductor switches are electrically connected in this order, and if they are both P-channel MOSFETs where the source terminal of the second semiconductor switch is also electrically connected to its gate terminal - see the more detailed explanation above - it will be understood that switching the first semiconductor switch on and off will not affect the switching of the second semiconductor switch. Regardless of whether the MCU outputs a high or low level signal from the first control terminal to switch the first semiconductor switch on and off, the second semiconductor switch may be maintained in the on-state (i.e., it may stay switched on) by outputting a high level signal from the second control terminal. However, if the first and second semiconductor switches are electrically connected in the reverse order with the same switch circuits, so that the source terminal of the first semiconductor switch is electrically connected to the energy storage device terminal, the source terminal of the second semiconductor switch is electrically connected to the drain terminal of the first semiconductor switch and to the gate terminal of the second semiconductor switch, and the drain terminal of the second semiconductor switch is electrically connected to the heater terminal, it will be understood that switching the first semiconductor switch on and off may also cause the second semiconductor switch to be switched on and off. This is because the on-state and the off-state of the first semiconductor switch will directly affect the electrical potential of the source and gate terminals of the second semiconductor switch. This may result in increased switching losses and lower energy efficiency. The overall switching operation may also become unstable.

[0023] The MCU may be adapted to switch on the second semiconductor switch and subsequently switch on the first semiconductor switch to allow power to be supplied from the energy storage device terminal to the heater terminal. It will be understood that if the second semiconductor switch is electrically connected to the energy storage device terminal, when it is in the off-state it will already be receiving a stable voltage (e.g., at its source and gate terminals if it is a P-channel MOSFET) and may be reliably switched to the on-state by the MCU. Once the second semiconductor switch has been switched on, the first semiconductor switch will also be electrically connected to the energy storage device terminal through the second semiconductor switch. It will therefore receive a stable voltage (e.g., at its source and gate terminals if it is a P-channel MOSFET) and may be reliably switched from the off-state to the on-state by the MCU. Compared with simultaneously switching both of the first and second semiconductor switches to the on-state, such delayed or sequential switching of the first and second semiconductor switches may be effective against inrush currents, for example. The MCU may be adapted to switch off the first semiconductor switch to stop power from being supplied from the energy storage device terminal to the heater terminal, and subsequently switch off the second semiconductor switch. Because the first and second switch circuits connected to the control terminals of the first and second semiconductor switches are different, the second semiconductor switch may switch off slightly later than the first semiconductor switch even if the MCU controls the signals from the first and second control terminals to switch between high and low voltage levels at the same time. For example, the first control signal may be switched from a low voltage level to a high voltage level to switch off the first semiconductor switch at the same time as the second control signal is switched from a high voltage level to a low voltage level to switch off the third semiconductor switch, which in turn switches off the second semiconductor switch. In other words, to switch off the second semiconductor switch, it is necessary to switch off the third semiconductor switch first. The third semiconductor switch will have an associated turn-off duration - i.e., the time taken for it to transition from the on-state to the off-state. This means that there is typically a delay in switching the second semiconductor switch from the on-state to the off-state. The second semiconductor switch may therefore be switched off slightly later than the first semiconductor switch even if the MCU switches the voltage levels of the first and second control signals at the same time. Such a delay may be beneficial because it prevents simultaneous switching of the first and second semiconductor switches. Such simultaneous switching may result in unexpected behaviour due to switching noise.

[0024] The first and second semiconductor switches may be switched on when it is necessary to supply power from the energy storage device to the heater to start to heat the aerosol generating material - e.g., at the start of a pre-heating phase. The first and second semiconductor switches may be switched off at the end of a heating phase during which the aerosol generating material is heated to generate an aerosol for inhalation by a user of the aerosol generating device (e.g., at the end of a vaping session).

[0025] During the heating phase, the MCU may be adapted to maintain the second semiconductor switch in the on-state and repeatedly switch the first semiconductor switch on and off (i.e., switch it between on- and off-states) to regulate power supplied from the energy storage device terminal to the heater terminal. This in turn will regulate the heating of aerosol generating material by the heater. Heating may be increased by supplying more power to the heater and vice versa. The second semiconductor switch may be maintained in the on-state by maintaining the third semiconductor switch in the on-state, for example. The first switch circuit connected to the control terminal of the first semiconductor switch may be simpler than the second switch circuit connected to the control terminal of the second semiconductor switch. For example, the second switch circuit for the second semiconductor switch may include the third semiconductor switch, the filter capacitor etc. The first semiconductor switch may therefore be more suitable for rapid switching operation using pulse width modulation or pulse frequency modulation, for example. In one arrangement, the first semiconductor switch may be switched on and off simply by controlling the voltage level of the first control signal that is output from the first control terminal of the MCU, whereas for the second semiconductor switch this may additionally involve switching the third semiconductor switch. The first semiconductor switch and first switch circuit may have a faster switching speed, lower switching noise, and lower energy losses than the second semiconductor switch and second switch circuit.

[0026] A printed circuit board assembly (PCBA) may be used to implement the control circuit described above. The PCBA may comprise a printed circuit board and electronic components, e.g., the semiconductor switches, MCU, capacitors, resistors etc. mentioned above, that are mounted to the printed circuit board.

[0027] The printed circuit board may be a double-sided circuit board - i.e., with electrically conductive paths on a top and bottom surface. The first and second semiconductor switches may be mounted to a first surface of a printed circuit board. If the control circuit comprises a third semiconductor switch, it may also be mounted on the first surface of the printed circuit board. This provides a convenient and simplified implementation of the PCBA. It may also reduce switching noise and / or energy losses. The MCU may be mounted to a second, opposite, surface of the printed circuit board. The MCU is therefore protected from switching noise coming from the semiconductor switches of the control circuit.

[0028] A solder point for the heater terminal may be provided on the second surface of the printed circuit board - i.e., the surface on which the MCU is mounted. A solder point for the energy storage device terminal may also be provided on the second surface of the printed circuit board. This provides a convenient and simplified implementation of the PCBA.

[0029] The PCBA may be located in a body or housing of an aerosol generating device.

[0030] According to a second aspect of the present disclosure, there is provided an aerosol generating system comprising: the control circuit or the PCBA described above; an energy storage device electrically connected to the energy storage device terminal; and a heater electrically connected to the heater terminal.

[0031] The energy storage device terminal may be a positive energy storage device terminal that may be electrically connected to a positive terminal of the energy storage device. The control circuit may further comprise a negative energy storage device terminal that may be electrically connected to a negative terminal of the energy storage device. The negative energy storage device terminal may be electrically connected to ground. Solder points for the positive and negative energy storage device terminals may be provided on the same surface of the printed circuit board to provide a convenient and simplified implementation of the PCBA.

[0032] The heater terminal may be a positive heater terminal that may be electrically connected to a positive terminal of the heater. The control circuit may further comprise a negative heater terminal that may be electrically connected to a negative terminal of the heater. The negative heater terminal may be electrically connected to ground. Solder points for the positive and negative heater terminals may be provided on the same surface of the printed circuit board to provide a convenient and simplified implementation of the PCBA.

[0033] The aerosol generating system may comprise an aerosol generating device and an aerosol generating article. The control circuit and the energy storage device may be part of the aerosol generating device. The aerosol generating article may be received in a body or housing of the aerosol generating device, for example. The aerosol generating article may be removably received in the body or housing. The aerosol generating article may be of any suitable type and may include an aerosol generator adapted to heat aerosol generating material to generate an aerosol for inhalation by a user. The aerosol generator may include the heater. Operation of the heater may be controlled by the control circuit. The heater may alternatively be part of the aerosol generating device.

[0034] The aerosol generator may be adapted to heat aerosol generating material. The aerosol generating material may be a liquid which may be stored in the aerosol generating article. The liquid aerosol generating material may soak into a wick (e.g., a cotton wick) and is then heated by the heater to produce a vapour that cools and condenses to form an aerosol that may then be inhaled. The wick may be omitted in some cases and the liquid aerosol generating material may be directly stored in a cavity of the aerosol generating article. The aerosol generating article may be formed as an integrated component (or “pod”) that includes a liquid store, a liquid transfer element or wick, and a heater. One or more electrical contacts may also be provided to establish an electrical connection between the heater and the energy storage device.

[0035] The aerosol generating material may comprise any type of solid or semi-solid material. Example types of aerosol generating solids include powder, granules, pellets, shreds, strands, particles, gel, strips, loose leaves, cut filler, porous material, foam material or sheets. The aerosol generating material may comprise plant derived material and in particular, may comprise tobacco. It may advantageously comprise reconstituted tobacco, for example including tobacco and any one or more of cellulose fibres, tobacco stalk fibres and inorganic fillers. The solid or semi-solid aerosol generating material may be heated by a heater that is provided as part of the aerosol generating article or the aerosol generating device - e.g., arranged adjacent to a heating space or chamber of the aerosol generating device that is adapted to receive the aerosol generating article in use. The aerosol generating material may comprise an aerosol-former. Examples of aerosol-formers include polyhydric alcohols and mixtures thereof such as glycerine or propylene glycol. Typically, the aerosol generating material may comprise an aerosolformer content of between approximately 5% and approximately 50% on a dry weight basis. In some embodiments, the aerosol generating material may comprise an aerosol -form er content of between approximately 10% and approximately 22% on a dry weight basis, and possibly approximately 15% on a dry weight basis.

[0036] The aerosol generating device may be adapted to heat the aerosol generating material or substrate, without burning the aerosol generating material, to volatise at least one component of the aerosol generating material and thereby generate a heated vapour which cools and condenses to form an aerosol for inhalation by a user of the aerosol generating device. The volatile compounds released from the aerosol generating material may include nicotine or flavour compounds such as tobacco flavouring.

[0037] In general terms, a vapour is a substance in the gas phase at a temperature lower than its critical temperature, which means that the vapour may be condensed to a liquid by increasing its pressure without reducing the temperature, whereas an aerosol is a suspension of fine solid particles or liquid droplets, in air or another gas. It should, however, be noted that the terms ‘aerosol’ and ‘vapour’ may be used interchangeably in this specification, particularly with regard to the form of the inhalable medium that is generated for inhalation by a user.

[0038] When the aerosol generating material is depleted, the aerosol generating article may be removed from the aerosol generating device and a new article may be inserted.

[0039] The aerosol generating article may include a mouthpiece through which the generated aerosol may be inhaled.

[0040] Brief Description of the Drawings

[0041] Figure 1 is a diagrammatic view of an aerosol generating system with an aerosol generating device and an aerosol generating article; Figure 2 is a circuit diagram showing the control circuit of the aerosol generating device; and

[0042] Figures 3A and 3B are diagrammatic views of top and bottom surfaces of a printed circuit board assembly implementing the control circuit of Figure 2.

[0043] Detailed Description of Embodiments

[0044] Embodiments of the present disclosure will now be described by way of example only and with reference to the accompanying drawings.

[0045] Referring initially to Figure 1 there is shown diagrammatically an example of an aerosol generating system 1. The aerosol generating system 1 comprises an aerosol generating device 2 and an aerosol generating article 4 for use with the aerosol generating device 2. The aerosol generating device 2 comprises a body or housing 6 and is sized to be comfortably held by a user unaided, in a single hand.

[0046] A power output control circuit is implemented by a printed circuit board assembly (PCBA) 8. The PCBA 8 comprises electronic components that are mounted on a printed circuit board 30 (Figure 3). The PCBA 8 is electrically connected to an energy storage device (e.g., a rechargeable battery 10) of the aerosol generating device 2.

[0047] The aerosol generating article 4 includes an aerosol generator 12 adapted to heat aerosol generating material (not shown) to generate an aerosol for inhalation by a user. The aerosol generator 12 includes a heater 14 that is electrically controlled by the control circuit. One or more electrical contacts (not shown) are provided on the body or housing 6 and the aerosol generating article 4 to provide an electrical connection when the aerosol generating article 4 is received in an opening 16 in the upper end of the body or housing 6. The heater 14 is used to heat aerosol generating material (not shown) to generate an aerosol that may be inhaled by a user through a mouthpiece 18 of the aerosol generating article 4.

[0048] Referring to Figure 2, the control circuit includes a microcontroller unit (MCU) 20.

[0049] The MCU 20 includes: a first input / output terminal 22, and a second input / output terminal 24.

[0050] The MCU 20 will receive operating power from a power supply terminal (not shown) that is electrically connected to the battery 10.

[0051] The control circuit includes a first semiconductor switch QI and a second semiconductor switch Q2. The first and second semiconductor switches QI and Q2 are P-channel MOSFETs.

[0052] A drain terminal of the first semiconductor switch QI is electrically connected to a positive heater terminal H+. A negative heater terminal H- is electrically connected to ground (e.g., the ground plane of the PCBA 8). The heater 14 is electrically connected to the positive and negative heater terminals H+ and H-. The heater 14 may be of any suitable type, e.g., a resistive heater, an induction heater, or a combination thereof. The heater 14 will operate as a heating element by consuming power from the battery 10.

[0053] A diode DI is electrically connected to the positive and negative heater terminals H+ and H- in parallel with the heater 14 as shown in Figure 2. The diode DI may protect the heater 14 from an over voltage.

[0054] A source terminal of the first semiconductor switch QI is electrically connected to a drain terminal of the second semiconductor switch Q2. A gate terminal of the first semiconductor switch QI is electrically connected to the first control terminal 22 of the MCU 20 by a first switch circuit 26 that includes a first switch resistor Rl. The gate terminal of the first semiconductor switch QI is also electrically connected to the source terminal of the first semiconductor switch QI by means of a resistor R4. The resistor R4 may electrically isolate the source and gate terminals of the first semiconductor switch QI if a stable voltage is applied to its gate terminal. The resistor R4 may also prevent an indefinite state of the gate terminal of the first semiconductor switch QI if a stable is not applied to the gate terminal by the MCU 20.

[0055] A source terminal of the second semiconductor switch Q2 is electrically connected to a positive battery terminal B+. A positive terminal of the battery 10 is electrically connected to the positive battery terminal B+. A negative terminal of the battery 10 is electrically connected to a negative battery terminal B- that is electrically connected to ground.

[0056] A gate terminal of the second semiconductor switch Q2 is electrically connected to the second control terminal 24 of the MCU 20 by a second switch circuit 28. The second switch circuit 28 includes a third semiconductor switch Q3, a filter capacitor Cl, a filter resistor R2, and a second switch resistor R3. The third semiconductor switch Q3 is a N-channel MOSFET, but it may also be a NPN bipolar transistor, for example. The source terminal of the third semiconductor switch Q3 is electrically connected to ground. The drain terminal of the third semiconductor switch Q3 is electrically connected to the gate terminal of the second semiconductor switch Q2. The filter capacitor Cl and the second switch resistor R3 are electrically connected in series between the gate terminal of the third semiconductor switch Q3 and the second control terminal 24 of the MCU. The filter resistor R2 is electrically connected between ground and the junction of the filter capacitor Cl and the gate terminal of the third semiconductor switch Q3.

[0057] The source terminal of the second semiconductor switch Q2 is electrically connected to the gate terminal of the second semiconductor switch Q2 by a capacitor C2 and a resistor R5. The capacitor C2 and the resistor R5 are electrically connected in parallel. The resistor R5 may isolate the source and gate terminals of the second semiconductor switch Q2 if a stable voltage is applied to its gate terminal and may also prevent an indefinite state of the gate terminal of the second semiconductor switch Q2 if a stable is not applied to the gate terminal. When power is not being supplied to the heater 14 (e.g., before the start of a pre-heating phase), the MCU 20 outputs a high level signal from the first control terminal 22 to the gate terminal of the first semiconductor switch QI so that it is switched off (i.e., in the off-state). The MCU 20 outputs a low level signal from the second control terminal 24 to the gate terminal of the third semiconductor switch Q3 so that it is switched off (i.e., in the off-state). As such, the second semiconductor switch Q2 is also switched off (i.e., in the off-state). Alternatively, an electrical potential of the first control terminal 22 may be indefinite.

[0058] When power is to be supplied from the battery 10 to the heater 14, i.e., from the positive battery terminal B+ to the positive heater terminal H+, the MCU 20 outputs a high level signal from the second control terminal 24 to the gate terminal of the third semiconductor switch Q3 so that it is switched on (i.e., switched to the on-state). The gate terminal of the second semiconductor switch Q2 is electrically connected to ground through the third semiconductor switch Q3 and is also switched on (i.e., switched to the on-state). A stable voltage is then supplied to the source terminal of the first semiconductor switch QI through the second semiconductor switch Q2. This stable voltage allows the first semiconductor switch QI to be reliably switched on. After the second semiconductor switch Q2 has been switched on, the MCU 20 outputs a low level signal from the first control terminal 22 to the gate terminal of the first semiconductor switch QI so that it is switched on (i.e., switched to the on-state). The positive battery terminal B+ is now electrically connected to the positive heater terminal H+ through the first and second semiconductor switches QI and Q2.

[0059] The second semiconductor switch Q2 may be maintained in the on-state and the MCU 20 may repeatedly switch the first semiconductor switch QI on and off (i.e., between the on- and off-states) to regulate the power supplied from the battery 10 to the heater 14. This may be used to regulate or control the heating of the aerosol generating material (not shown), e.g., during a heating phase of the aerosol generating system 1. To maintain the second semiconductor switch Q2 in the on-state, the MCU 20 will continue to output a high level signal from the second control terminal 24 to the gate terminal of the third semiconductor switch Q3. The first semiconductor switch QI is repeatedly switched on and off (i.e., between the on- and off-states) by repeatedly switching the voltage level of the first control signal between high and low voltage levels. The switching between the high and low voltage levels may be controlled using pulse width modulation or pulse frequency modulation, for example.

[0060] When power no longer needs to be supplied from the battery 10 to the heater 14, i.e., from the positive battery terminal B+ to the positive heater terminal H+, the MCU 20 outputs a high level signal from the first control terminal 22 to the gate terminal of the first semiconductor switch QI so that it is switched off (i.e., switched to the off-state). The positive heater terminal H+ is now electrically isolated from the positive battery terminal B+ by the first semiconductor switch QI. A stable voltage is still supplied to the source terminal of the second semiconductor switch Q2 and this allows the second semiconductor switch Q2 to be reliably switched off. To do this, the MCU 20 outputs a low level signal from the second control terminal 24 to the gate terminal of the third semiconductor switch Q3 so that it is switched off (i.e., switched to the off-state). The gate terminal of the second semiconductor switch Q2 is no longer electrically connected to ground through the third semiconductor switch Q3 and is also switched off (i.e., to the off-state). In practice, switching delays because of the differences in the first and second switch circuits 26, 28 means that the MCU 20 may start to output the high level signal from the first control terminal 22 and the low level signal from the second control terminal 24 at the same time. Such a delay may be beneficial because it prevents simultaneous switching of the first and second semiconductor switches QI and Q2. Such simultaneous switching may result in unexpected behaviour due to switching noise. The capacitor C2 may also contribute to the switching delay because some time is needed to discharge the electrical charge that is stored in the capacitor C2.

[0061] In the control circuit described above, the first and second semiconductors switches QI and Q2 are electrically connected in series between the positive battery terminal B+ and the positive heater terminal H+. In other words, a positive control mechanism is employed. A fourth semiconductor switch (not shown) may additionally be provided between the negative heater terminal H- and ground. Adding a fourth semiconductor switch between the negative heater terminal H- and ground may provide a further improvement in the safety of the aerosol generating device 2. The fourth semiconductor switch may be switched on any off by the MCU 20.

[0062] In an alternative control circuit, the first and second semiconductor switches QI and Q2 may be electrically connected in series between the negative heater terminal H- and ground. In other words, a negative control mechanism may be employed. In this alternative control circuit, both the first and second semiconductor switches QI and Q2 may be N-channel MOSFETs. The third semiconductor switch Q3 may be a P- channel MOSFET. The switching control will be as described above, but it will be understood that the voltage levels of the first and second control signals will be inverted, for example.

[0063] Figures 3 A and 3B show top and bottom surfaces of the printed circuit board 30 of the PCBA 8 that implements the control circuit. The MCU 20 is mounted to the top surface 30a of the printed circuit board 30. The first, second, and third semiconductor switches QI, Q2 and Q3 are mounted on the bottom surface 30b of the printed circuit board 30. The MCU 20 is therefore protected from switching noise coming from the first, second, and third semiconductor switches QI, Q2 and Q3.

[0064] The heater 14 is electrically connected to the positive and negative heater terminals H+ and H- by a pair of wires. Solder points for electrically connecting the wires to the positive and negative heater terminals H+ and H- are provided on the top surface 30a of the printed circuit board 30. In particular, each wire may extend through the body of the printed circuit board 30 from the bottom surface 30b to the top surface 30a where it is soldered to a respective solder point. Similarly, the battery 10 is electrically connected to the positive and negative battery terminals B+ and B- by a pair of wires. Solder points for electrically connecting the wires to the positive and negative battery terminals B+ and B- are provided on the top surface 30a of the printed circuit board 30. In particular, each wire may extend through the body of the printed circuit board 30 from the bottom surface 30b to the top surface 30a where it is soldered to a respective solder point. This provides a convenient and simplified implementation of the PCBA 8. Although exemplary embodiments have been described in the preceding paragraphs, it should be understood that various modifications may be made to those embodiments without departing from the scope of the appended claims. Thus, the breadth and scope of the claims should not be limited to the above-described exemplary embodiments.

[0065] Any combination of the above-described features in all possible variations thereof is encompassed by the present disclosure unless otherwise indicated herein or otherwise clearly contradicted by context.

[0066] Unless the context clearly requires otherwise, throughout the description and the claims, the words “comprise”, “comprising”, and the like, are to be construed in an inclusive as opposed to an exclusive or exhaustive sense; that is to say, in the sense of “including, but not limited to” .

Claims

Claims1. A control circuit for an aerosol generating device (2), the control circuit comprising: an energy storage device terminal (B+) electrically connectable to an energy storage device (10); a heater terminal (H+; H-) electrically connectable to a heater (14); first and second semiconductor switches (QI, Q2) electrically connected in series between the energy storage device terminal (B+) and the heater terminal (H+) or between the heater terminal (H-) and ground; and a microcontroller unit (20) having a first control terminal (22) and a second control terminal (24); wherein the first control terminal (22) of the microcontroller unit (20) is electrically connected to a control terminal of the first semiconductor switch (QI) by a first switch circuit (26) and the second control terminal (24) of the microcontroller unit (20) is electrically connected to a control terminal of the second semiconductor switch (Q2) by a second switch circuit (28).

2. A control circuit according to claim 1, wherein the first and second semiconductor switches (QI, Q2) are P-channel MOSFETs.

3. A control circuit according to claim 1 or claim 2, wherein the microcontroller unit (20) is adapted to output a first control signal from the first control terminal (22) for controlling the switching of the first semiconductor switch (QI) so that the first semiconductor switch (QI) is in the on-state if the first control signal has a low level and is in the off-state if the first control signal has a high voltage level, and wherein the microcontroller unit (20) is adapted to output a second control signal from the second control terminal (24) for controlling the switching of the second semiconductor switch (Q2) so that the second semiconductor switch (Q2) is in the on- state if the second control signal has a high voltage level and is in the off-state if the second control signal has a low voltage level.

4. A control circuit according to any preceding claim, wherein the second switch circuit (28) comprises a third semiconductor switch (Q3) electrically connected between the control terminal of the second semiconductor switch (Q2) and ground, and wherein a control terminal of the third semiconductor switch (Q3) is electrically connected to the second control terminal (24) of the microcontroller unit (20).

5. A control circuit according to claim 4, wherein the third semiconductor switch (Q3) is an N-channel MOSFET or an NPN bipolar transistor.

6. A control circuit according to claim 4 or claim 5, wherein the second semiconductor switch (Q2) is a P-channel MOSFET, and further comprising a capacitor (C2) electrically connected between the source and gate terminals of the second semiconductor switch (Q2).

7. A control circuit according to any of claims 4 to 6, wherein the control terminal of the third semiconductor switch (Q3) is electrically connected to the second control terminal of the microcontroller unit (20) by a filter capacitor (Cl).

8. A control circuit according to claim 7, further comprising a filter resistor (R2) electrically connected to the junction between the filter capacitor (Cl) and the control terminal of the third semiconductor switch (Q3).

9. A control circuit according to any of claims 4 to 8, wherein the first semiconductor switch (QI) is electrically connected between the second semiconductor switch (Q2) and the heater terminal (H+).

10. A control circuit according to claim 9, wherein the microcontroller unit (20) is adapted to switch on the second semiconductor switch (Q2) and subsequently switch on the first semiconductor switch (QI) to allow power to be supplied from the energy storage device terminal (B+) to the heater terminal (H+).

11. A control circuit according to claim 9 or claim 10, wherein the microcontroller unit (20) is adapted to maintain the second semiconductor switch (Q2) in the on-state and repeatedly switch the first semiconductor switch (QI) on and off to regulate power supplied from the energy storage device terminal (B+) to the heater terminal (H+).

12. A control circuit according to any of claims 9 to 11, wherein the microcontroller unit (20) is adapted to switch off the first semiconductor switch (QI) to stop power from being supplied from the energy storage device terminal (B+) to the heater terminal (H+), and subsequently switch off the second semiconductor switch (Q2).

13. A printed circuit board assembly (8) implementing the control circuit according to any preceding claim, wherein the first and second semiconductor switches (QI, Q2) are mounted to a first surface of a printed circuit board and the microcontroller unit (20) is mounted to a second, opposite, surface of the printed circuit board.

14. An aerosol generating system (1) comprising: the control circuit according to any of claims 1 to 12 or the printed circuit board assembly (8) according to claim 13; an energy storage device (10) electrically connected to the energy storage device terminal (B+); and a heater (14) electrically connected to the heater terminal (H+; H-).

15. An aerosol generating system (1) according to claim 14, comprising an aerosol generating article (4) and an aerosol generating device (2) adapted to receive the aerosol generating article (4) in use, wherein the aerosol generating device (2) comprises the control circuit or printed circuit board assembly (8), and the energy storage device (10), and wherein the aerosol generating article (4) comprises the heater (14).

Images