[Technical Field]

The present invention generally relates to the field of inhalation devices . In particular, the present invention is directed to a control unit for an inhalation device with at least one liquid j et device for producing drops of a liquid on demand, an inhalation device comprising such a control unit , and a method performed by such a control unit .

[ Background ]

Inhalation devices , also referred to as aerosol generation devices , such as e-cigarettes , vaping devices and aerosol inhalers , are known .

Such inhalation devices are hand-held devices and conventionally include an atomizer , a power supply, and a liquid-filled capsule , or similar means disposed therein in order to generate an aerosol ( that is , a vapour ) to be inhaled by a user . By way of example , conventional inhalation devices generally change the phase of a fluid before inhalation with, for example , a wick and a coil so as to significantly raise the vapour temperature above human body temperature or deliver drops at room temperature by, for example , employing an ultrasonic mesh .

The generated aerosol may contain, for example , a form of nicotine such that user of the inhalation device may, for example , simulate smoking tobacco by inhaling the generated aerosol .

Inhalation devices generally have to be of a relatively small size and relatively low weight in order to be handheld and easily portable . Normally, this requirement results in limited power supply as the battery ( or any other suitable power supply means ) must be relatively small and light .

As such, the present inventors have recognised a general need to improve inhalation devices , e . g . in terms of efficiency, size and/or weight .

[Summary of the Invention]

The present invention is intended to address one or more of the above technical problems . One or more of these problems may be remedied by the subj ect-matter of the independent claims . Further preferred embodiments are defined in the dependent claims .

In particular, in view of the limitations discussed above , the present inventors have devised, in accordance with a first aspect herein, a control unit for an inhalation device with at least one liquid j et device for producing drops of a liquid on demand . The control unit is configured to control supply of voltage to a heating element of the liquid j et device based on a pulse train . The pulses of the pulse train have a pulse width and a given voltage . The pulse width is less than or equal to 1 . 5ps .

The present inventors have further devised, in accordance with a second aspect herein, an inhalation device comprising at least one liquid j et device for producing drops of a liquid on demand, a power supply unit configured to supply voltage to the liquid j et device at a given voltage , and a control unit according to the first aspect herein . The liquid j et device comprises a fluid chamber, at least one ej ection nozzle , a supply channel and a heating element configured to heat the liquid in order to cause ej ection through the at least one ej ection nozzle .

The present inventors have further devised, in accordance with a third aspect herein, a method performed by a control unit for an inhalation device with at least one liquid j et device for producing drops of a liquid on demand . The method comprises controlling supply of voltage to a heating element of the liquid j et device based on a pulse train . The pulses of the pulse train have a pulse width and a given voltage . The pulse width is less than or equal to 1 . 5ps .

The present inventors have further devised, in accordance with a fourth aspect herein, a computer program comprising instructions which, when executed by a control unit of an inhalation device with at least one liquid j et device for producing drops of a liquid on demand, cause the control unit to perform a method according to the third aspect herein .

[Brief Description of the Drawings ]

Embodiments of the invention will now be explained in detail , by way of non-limiting example only, with reference to the accompanying figures , described below . Like reference numerals appearing in different ones of the figures can denote identical or functionally similar elements , unless indicated otherwise .

Figure 1 is a schematic illustration of an inhalation device in accordance with an embodiment of the present invention .

Figure 2A is a schematic view of a first liquid j et device as employed in an inhalation device in accordance with an embodiment of the present invention .

Figure 2B is a schematic view of a second liquid j et device as employed in an inhalation device in accordance with an embodiment of the present invention .

Figures 3A and 3B are schematic illustrations of exemplary layouts of ej ection noz zles associated with a heating element in a liquid j et device . Figure 4 is a flow diagram illustrating a process performed by the control unit of Figure 1 in accordance with an embodiment of the present invention .

Figure 5 shows a graph of an exemplary pulse train .

Figure 6 shows a graph of proportional Turn-On Energy versus pulse width .

Figure 7 shows a graph of corresponding Turn-On Voltage versus pulse width .

[Detailed Description]

Example embodiments of the present invention will now be described in detail with reference to the accompanying drawings .

Where technical features in the drawings , detailed description or any claim are followed by reference signs , the reference signs have been included for the sole purpose of increasing the intelligibility of the drawings , detailed description, and claims . Accordingly, neither the reference signs nor their absence have any limiting effect on the scope of any claim elements .

The present inventors have recognised that inhalation device may use drop-on demand technology similar to inkj et printers in order to generate an aerosol by providing at least one liquid j et device in an inhalation device . Such liquid j et devices , which may also be referred to as thermal inkj et microfluidic devices , allow liquid drops to be produced on demand so as to form an aerosol .

Firing a liquid j et device ( i . e . producing a drop of liquid by the inkj et device ) typically takes a specific amount of energy . This amount of energy may be referred to as the Turn-On Energy (TOE ) , which is defined as the amount of energy needed to initiate drop ej ection . It is known that when firing a liquid j et device with a single heater and a single noz zle the efficiency of the liquid et device ( electricity in vs . mechanical momentum/energy out ) decreases as the drop size decreases . This may result in a presumed decrease in efficiency of a liquid j et device when drop size decreases , particularly to the size required for aerosol generation .

Inhalation devices generally have to be of a relatively small size and relatively low weight in order to be handheld and easily portable . Normally, this requirement results in limited power supply as the battery ( or any other suitable power supply means ) must be relatively small and light .

The present inventors have recognised that such a limited power supply may be incompatible with the above-identified decrease in efficiency of a liquid j et device as the drop size decreases . As such, the present inventors have recognised a need to improve efficiency of use of liquid j et devices , so as to allow the use of liquid j et devices in an inhalation device without exceeding any power supply limitations of the inhalation device .

In view of the limitations discussed above , there is described, in accordance with a first aspect herein, a control unit for an inhalation device with at least one liquid j et device for producing drops of a liquid on demand . The control unit is configured to control supply of voltage to a heating element of the liquid j et device based on a pulse train . The pulses of the pulse train have a pulse width and a given voltage . The pulse width is less than or equal to 1 . 5ps .

In accordance with a second aspect herein, there is described an inhalation device comprising at least one liquid j et device for producing drops of a liquid on demand, a power supply unit configured to supply voltage to the liquid j et device at a given voltage , and a control unit according to the first aspect herein . The liquid j et device comprises a fluid chamber, at least one ej ection nozzle , a supply channel and a heating element configured to heat the liquid in order to cause ej ection through the at least one ej ection noz zle .

In accordance with a third aspect herein, there is described a method performed by a control unit for an inhalation device with at least one liquid j et device for producing drops of a liquid on demand . The method comprises controlling supply of voltage to a heating element of the liquid j et device based on a pulse train . The pulses of the pulse train have a pulse width and a given voltage . The pulse width is less than or equal to 1 . 5ps .

In accordance with a fourth aspect herein, there is described a computer program comprising instructions which, when executed by a control unit of an inhalation device with at least one liquid j et device for producing drops of a liquid on demand, cause the control unit to perform a method according to the third aspect herein .

According to the first to fourth aspect , supply of voltage to a heating element of the liquid j et device based on a pulse train, the pulses of the pulse train having a pulse width and a given voltage . By way of more particular example , to generate sufficient drops to create an aerosol , the control unit creates the pulse train at a desired frequency, which repeatedly energizes the one or more heating element , causing fluid drops to be ej ected .

The present inventors have recognised that the TOE required by the liquid j et device to produce a drop on demand may decrease as the pulse width of the pulses of the pulse train decreases . In particular , conventional liquid j et devices typically use a pulse width of 1 . 8ps to 2 . 5ps to create a drop . The present inventors have recognised that , by reducing the pulse width relative to such conventional devices , the TOE required by the liquid j et device to produce a drop on demand may be reduced . Therefore, according to each of first to fourth aspects herein, the pulse width of the pulses of the pulse train is less than or equal to 1.5ps .

This reduces the energy used by the liquid jet device to produce drops, in accordance with the reduced TOE. In particular, the energy consumed by the liquid jet device to produce a drop on demand is proportional to the square of the voltage applied to the heating element of the liquid jet device multiplied by the time (i.e. V ² t) . As such, reducing the pulse width (i.e. time t) reduces the energy consumed by the liquid jet device.

Accordingly, by controlling supply of voltage to a heating element of the liquid jet device based on a pulse train with pulses having a pulse width of less than 1.5 ps, the overall amount of energy consumed by the liquid jet device during production of an aerosol may be reduced. In this way, the efficiency of the use of a liquid jet device in an inhalation device may be improved.

This may in turn allow the use of liquid jet devices in an inhalation device without exceeding any limitations of the power supply of the inhalation device or enable for a decrease in the size of the battery (or other power supply means) of the inhalation device.

Figure 1 is a schematic illustration of an inhalation device 100 in accordance with an embodiment of the present invention. The inhalation device 100 comprises a liquid jet device 210 for producing drops of a liquid on demand. The liquid jet device 210 comprises a fluid chamber, at least one ejection nozzle, a supply channel and a heating element configured to heat the liquid in order to cause ejection through the at least one ejection nozzle.

Details of the elements of the liquid jet device 210 are shown and described below in relation to Figures 2A, 2B, 3A and 3B. The term fluid chamber is meant to cover jet technologies generally, including at least piezo jet and thermal jet devices, wherein in the latter case the fluid chamber is then usually referred to as a firing chamber.

The inhalation device 100 further comprises a control unit 110 in accordance with an embodiment herein. Operation of the control unit 110 will be described in more detail below in relation to Figure 4.

More generally, the control unit 110 may, as in the present example embodiment, be configured to control operation of the inhalation device 100. By way of example, in example embodiments such as the present example embodiment in which the inhalation device 100 comprises a power supply unit 120, the control section 110 may control charging of a power supply unit. Additionally or alternatively, the control section 11 may optionally control supply of power to, and receive and process signals from any sensors or I/O units (e.g. optional button 130) included in the inhalation device 100 and control operation of the inhalation device 100 based on the received signals.

The control unit 110 may comprise one or more processing units or modules (e.g. a central processing unit (CPU) such as a microprocessor, or a suitably programmed field programmable gate array (FPGA) or application-specific integrated circuit (ASIC) ) . Additionally or alternatively, the control unit 110 may be provided with any memory sections (not shown) necessary to perform its function of controlling operation of the inhalation device 100. Such memory sections may be provided as part of (comprised in) the control unit 110 (e.g. integrally formed or provided on the same chip) or provided separately, but electrically connected to the control unit 110. By way of example, the memory sections may comprise both volatile and non-volatile memory resources, including, for example, a working memory (e.g. a random access memory) . In addition, the memory sections may include an instruction store (e.g. a ROM in the form of an electrically- erasable programmable read-only memory (EEPROM) or flash memory) storing a computer program comprising the computer-readable instructions which, when executed by the control unit 110, cause the control unit 110 to perform various functions described herein .

The computer program comprising the computer-readable instructions which, when executed by the control unit 110, cause the control unit 110 to perform various functions described herein may, for example, be a software or a firmware program.

The inhalation device 100 may, as in the present example embodiment, further comprise a power supply unit 120. The power supply unit 120 may, as in the present example embodiment, be a rechargeable power supply. The power supply unit 120 may, as in the present example embodiment, be a lithium ion battery. Alternatively, the power supply unit 120 may be, for example, a chargeable secondary battery or an electric double layer capacitor (EDLC) or any other suitable power supply means known in the art.

Additionally or alternatively, the inhalation device 100 may, as in the present example embodiment, comprise a reservoir 220 for storing an amount of said liquid to be vaporized. By way of nonlimiting example, the liquid may contain nicotine and/or flavours (e.g. mint, menthol, herbs, and/or fruit flavours) . Optionally, the liquid stored in the reservoir 220 may include additional substances, such as glycerin, propylene glycol and/or water, to aid formation of an aerosol.

By way of example, the reservoir 220 and/or the liquid stored therein may be replaceable. By way of example, at least the reservoir 220 of the inhalation device 100 may be provided in the form of a replaceable cartridge. Preferably, the inhalation device may further comprise a reservoir heating element ( not shown ) arranged to heat the liquid in said reservoir 220 and/or in a flow path between said reservoir 220 and liquid j et device 210 to a predetermined liquid reservoir temperature . This may allow the liquid to be provided to the liquid j et device 210 from the reservoir 220 at an optimal temperature for producing drops by the liquid j et device 210 .

Additionally or alternatively, the inhalation device 100 may, as the present example embodiment , comprise an air conduit 230 and a mixing chamber ( not shown ) in which air from said air conduit 230 is mixed with the liquid drops generated by the liquid j et device 210 . The air conduit 230 further comprises at least one air inlet orifice 240 at some suitable site of said inhalation device 100 .

Additionally or alternatively, the inhalation device 100 may, as in the present example embodiment , comprise a mouthpiece opening 310 through which a user may inhale the inhalation vapour . The mouthpiece 300 may be integral with the housing of the inhalation device 100 , it may be replaceable , or may form part of a capsule or cartridge . The latter may comprise further elements , such as the mixing chamber, the liquid j et device 210 or the reservoir 220 so as to provide a replaceability of further elements for achieving convenience , flexibility, reliability and/or safety .

Figure 2A is a schematic view of a first liquid j et device 210 as employed in an inhalation device in accordance with an embodiment of the present invention .

The liquid j et device 210 comprises a fluid chamber 211 , at least one ej ection nozzle 214 , a supply channel 213 and a heating element 212 configured to heat the liquid 216 in order to cause ej ection through the at least one ej ection nozzle 214 .

The heating element 212 may, as in the present example embodiment , be arranged in the vicinity of the fluid chamber 211 . In such embodiments, the control unit 110 may control the heating element 212 to heat up a portion of the liquid 216 to vaporized and form a gas bubble 217. The resulting expansion leads to the ejection of an amount of the liquid 216 in the form of a drop or droplet 215 through the ejection nozzle 214. By way of example, the drop 215 may then form a vapour or aerosol in the mixing chamber.

By way of example, the fluid chamber 211 may, as in the present example embodiment, be in liquid communication with the reservoir 220 for providing liquid 216 to the fluid chamber 211 so as to be vaporized or atomized.

The heating element 212 may, for example, be a resistive heating element. By way of more specific example, the heating element 212 may be a resistor embedded in the substrate.

The liquid jet device 210 may, as in the present example embodiment, be formed as a micro-electromechanical system, MEMS, in a substrate of any suitable material, for example silicon. In such example embodiments, the fluid chamber 211, the ejection nozzle 214, and the supply channel 213 may be formed on the substrate. In addition, in a case where the heating element 212 comprises a resistor, the resistor may be deposited on a substrate of the MEMs. Such a MEMs liquid jet device may, by way of nonlimiting example, be mounted on a printed circuit board.

In the liquid jet device 210 showing in Figure 2A, the liquid jet device 210 comprises a single ejection nozzle 214 in association with the heating element 212. Alternatively, the liquid jet device may comprise two or more ejection nozzles in association with the heating element 212. That is, the liquid jet device 210 may have a 'shower head' type design in which there are multiple ejection nozzles per heating element and at least some of the plurality of ejection nozzles associated with the heating element are provided at the edge of the fluid chamber. By way of example, Figure 2B shows a schematic view of a second liquid jet device 210 as employed in an inhalation device in accordance with an embodiment of the present invention. In the liquid jet device 210 shown in Figure 2B, the heating element 212 is associated with three ejection nozzles 214-1 to 214-3.

As such, the control unit 110 may control the heating element 212 to heat up a portion of the liquid 216 to vaporized and form a gas bubble 217. The resulting expansion leads to the ejection of an amount of the liquid 216 in the form of respective drops (or droplets) 215-1 to 215-3 through each of the ejection nozzle 214-1 to 214-3. By way of example, the drops 215-1 to 215-3 may then form a vapour or aerosol in the mixing chamber.

By way of further alternative, the heating element 212 of the liquid jet device 210 may be associated with any suitable number of ejection nozzles in any suitable layout. By way of non-limiting example, Figures 3A and 3B are schematic illustrations of alternative exemplary layouts of ejection nozzles 214-1 to 214-9 associated with the heating element 212 in the liquid jet device 210.

As shown in Figure 3A, the ejection nozzles 214-1 to 214-9 may be arranged at the edge of the fluid chamber only. Alternatively, as shown in Figure 3B, the ejection nozzles 214-1 to 214-9 may be arranged at the edge and the centre of the fluid chamber.

The use of liquid jet devices having such 'shower head' type designs may, in combination with the control device of the present invention, allow for further improvement in the efficiency of the use of a liquid jet device in an inhalation device, particularly where smaller drops suitable for generation of an aerosol are to be produced. In particular, such 'shower head' type designs allow for multiple drops to be produced with each energy pulse (i.e. pulse of the pulse train) , thereby further improving efficiency. In particular, when compared to a single nozzle per resistor, the shower head type design improves both the mechanical and electrical efficiencies of the drop generation.

More specifically, conventional liquid jet devices typically use a pulse width of 1.8ps to 2.5ps to produce a drop. In conventional devices having a single ejection nozzle per heater, a controlled drop is produced through a square wave pulse. As a true square wave is never generated, utilizing such 'long' pulse widths (e.g. a 2. Ops pulse) allows the taper of the pulse wave to be insignificant to the overall energy, creating more consistency.

However, when a 'shower head' type design having multiple ejection nozzles per heater is provided in a liquid jet device, the system dynamics can change. As such, by controlling supply of voltage to a heating element of the liquid jet device based on a pulse train with pulses having a pulse width of less than 1.5 ps, the resultant energy needed for TOE is reduced while also maintaining the consistency achieved with conventional liquid jet device through use of a 'shower head' type design.

Optionally, the given voltage of the pulses of the pulse train may be increased relative to conventional liquid jet devices to compensate for the reduced pulse width. In this case, the resultant energy needed for TOE is still reduced, while further ensuring consistency of drop production.

In Figures 2A and 2B, the liquid jet device 210 comprises a single heating element 212. Alternatively, the liquid jet device 210 may comprise multiple heating elements 212, each heating element 212 being associated with a respective one or more ejection nozzles 214. In example embodiments in which the liquid jet device 210 comprises multiple heating elements 212, the control unit 110 may be configured to control the supply of power to each of the heating elements 212 based on the pulse train. As discussed in detail above, the present inventors have recognised a need to improve efficiency of use of liquid jet devices, so as to allow the use of liquid jet devices in an inhalation device without exceeding any power supply limitations of the inhalation device. This objective may be achieved by the control unit 110 configured to perform a process as described in relation to Figure 4.

Figure 4 is a flow diagram illustrating a process performed by the control unit 110 of Figure 1 in accordance with an embodiment of the present invention.

In process step S41 of Figure 4, control unit 110 controls supply of voltage to a heating element 212 of the liquid jet device 210 based on a pulse train. The pulses of the pulse train have a pulse width and a given voltage. The pulse width is less than or equal to 1.5ps

That is, the control unit 110 may control supply of power (e.g. from the power supply unit 120 or a connected external power supply) to the heating element 212 such that the heating element 212 receives voltage in the form of a pulsed waveform. The control unit 110 may control the width of the pulses of the pulse train (i.e. the length of time the waveform is ON or positive) so as to control the length of time for which voltage is continuously supplied to the heating element .

Thus, the control unit 110 may reduce the amount of time for which current is continuously supplied to the heating element during a pulse of a given pulse width such that the pulse width is less than or equal to 1.5ps. The energy consumed by the liquid jet device 210 to produce a drop on demand is proportional to the square of the voltage applied to the heating element 212 of the liquid jet device 210 multiplied by the time (i.e. V ² t) . As such, reducing the pulse width (i.e. time t) relative to conventional liquid jet devices, which typically use a pulse width of 1.8ps to 2 . 5ps , allows the energy consumed by the liquid j et device to be reduced .

Additionally or alternatively, the control unit 110 may control the voltage of the pulses of the pulse train so as to control the amount of voltage that is continuous ly supplied to the heating element during a pulse of a given pulse width .

By way of example , the given voltage may be appropriately selected based on the required Turn-On Energy (TOE ) , which is defined as the amount of energy needed to initiate drop ej ection . The TOE for a liquid j et device may be determined experimentally, for example , by sweeping through a series of voltages with a given pulse width to visually detect when a drop is first ej ected . Alternatively, in order to prevent overheating a system when no drops are ej ected, the TOE for a liquid j et device may be determined experimentally by starting at a high voltage and decreasing voltage until no drop is ej ected . By way of further alternative , the TOE may be determined experimentally by sweeping through a series of pulse widths with the voltage being held constant , starting with a long pulse width and gradually reducing the pulse width, to visually detect when a drop is first ej ected . The voltage and pulse width at which a drop ej ect is first detected may then be used to derive the TOE and/or the given voltage .

By way of example , the given voltage of the pulses of the pulse train may, as in the present example embodiment , correspond to a peak voltage of the pulse train excluding any overshoot . That is , the given voltage may be a high level/ON voltage of the ideal pulse train ( i . e . the target high level voltage ) , which is the steady state peak value of the pulses supplied to the at least one ink j et device .

Such a peak voltage may exclude any overshoot in that a positive overshoot may briefly result in a voltage exceeding the target high level voltage of the pulse. Such overshoot voltages are not considered to be the peak voltage.

By way of more specific example, Figure 5 shows a graph of an exemplary pulse train. Voltage V is shown on the ordinate (y-axis) and time t is plotted on the abscissa (x-axis) .

In the example of Figure 5, the pulse train 501 is a square wave alternating between a fixed maximum value 503 (e.g. 12V) and a fixed minimum value 504 (e.g. 0V) . However, the voltage supplied to the at least one ink jet device in the form of pulse train 501 does not correspond exactly to ideal square wave 502 due to the inherent limitations of electronic components. Instead, the pulse train 501 may have non-zero rise and fall times and may oscillate about the fixed maximum value 503 and the fixed minimum value 504. In this case, the fixed maximum value 504 is taken to be the peak voltage (i.e. 12V in this example) , even though higher voltage values may be present due to overshoot. As such, in the example of Figure 5, the given voltage of the pulse train 501 is the fixed maximum value 503.

As such, the control unit 110 may control the amount of voltage and the resulting current applied to the heating element 212 of the liquid jet device 210.

For example, the control unit 110 may, as in the present example embodiment, control the supply of voltage to the heating element 212 of the liquid jet device 210 such that a ratio of the given voltage in volts to the pulse width in ps is greater than or equal to 8.

By controlling the supply of voltage such that this relationship between the pulse width and the given voltage is maintained, it can be ensured that the given voltage of the pulses of the pulse train may be appropriately increased relative to conventional liquid jet devices to compensate for the reduced pulse width. As such, it is possible to ensure that a sufficient TOE is achieved to effectively produce drops while also reducing the overall resultant energy needed for TOE , thereby ensuring consistency of drop production .

By way of preferable example , the control unit 110 may, as in the present example embodiment , control the supply of voltage to the heating element 212 of the liquid j et device 210 such that the pulse width is less than or equal to 1 . 2ps and/or the given voltage is greater than or equal to 12V .

By way of more preferable example , the control unit 110 may, as in the present example embodiment , control the supply of voltage to the heating element 212 of the liquid j et device 210 such that the pulse width is less than or equal to 0 . 8ps and/or the given voltage of greater than or equal to 14V .

The heating element 212 may, as in the present example embodiment , be configured to heat up a portion of the liquid 216 to vaporized and form a gas bubble 217 so as to ej ect an amount of the liquid 216 in the form of one or more drops ( dependent on the number of ej ection nozzles ) in response to the voltage supplied thereto with each pulse of the pulse train .

Additionally, the control unit 110 may, as in the present example embodiment , control other aspects of the pulse train such as the frequency, shape , and/or duty cycle of the pulse train . By way of example , the pulse train may be in the form of a square wave , a rectangular wave , a sawtooth wave , a triangular wave , or any other suitable wave form .

The interrelation between pulse width, given voltage , and TOE is illustrated in Figures 6 and 7 . Figure 6 shows a graph of proportional TOE versus pulse width and Figure 7 shows a graph of corresponding Turn-On Voltage versus pulse width for a liquid j et device having a shower head type design . As shown in Figure 6, the energy consumed by the liquid jet device 210 to produce a drop on demand is proportional to the square of the voltage applied to the heating element 212 of the liquid jet device 210 multiplied by the time (i.e. V2t) . As shown in Figure 7, reducing the pulse width (i.e. time t) may result in a higher required Turn-On Voltage but, consequently, a lower current and, thus, less energy used, as indicated by arrow 600 in Figure 6.

Accordingly, by controlling supply of voltage to a heating element of the liquid jet device based on a pulse train with pulses having a pulse width of less than 1.5 ps, the overall amount of energy consumed by the liquid jet device 210 during production of an aerosol may be reduced. In this way, the efficiency of the use of a liquid jet device 210 in an inhalation device 100 may be improved .

In particular, energy inefficiency in liquid jet devices produces excess heat, which may be transferred to silicon or other substrates forming the liquid jet devices. In order to compensate for the excess heat generated by less efficient parts, conventional liquid jet devices and associated control units relied on thermal throttling (that is, decreasing speed in order to decrease heat) or increasing a silicon area to dissipate the heat .

By controlling supply of voltage to the liquid jet device 210 in accordance with the process of Figure 4, the efficiency of the use of a liquid jet device 210 in an inhalation device 100 may be improved. This may result in less excess heat being generating, thereby reducing the need to rely on thermal throttling and/or increasing silicon area.

Furthermore, in example embodiments such as the present example embodiment, in which the power supply unit 120 is rechargeable, improving efficiency may result in the power supply unit 120 lasting longer for every charge cycle , thereby increasing life of the inhalation device 100 or allowing for a decrease in size of the power supply unit 120 .

The control unit 110 may be configured to initiate controlling supply of voltage to the heating element of the liquid j et device based on the pulse train by any suitable means . By way of example , the control unit 110 may be caused to initiate controlling by any action or input of a user of the inhalation device 100 that causes the inhalation device to generate an aerosol . For example , the control unit 110 initiate controlling in response to detecting that the user has provided input to an I /O device of the inhalation device 100 ( e . g . optional button 130 shown in Figure 1 ) , in a response to a detection of the user inhaling through the mouthpiece opening 310 by suitable sens ing means , etc .

Additionally or alternatively, the inhalation device 100 may be configured to generate aerosol only for a predetermined length of time following an action or input of a user of the inhalation device 100 to cause the inhalation device to generate an aerosol . This may help to ensure safe and reliable operation of the inhalation device 100 . For example , the inhalation device 100 may be configured so as to allow aerosol to be continuously generated for up to a maximum time limit only, e . g . Is , 3s , or 5s .

In such cases , the control unit 110 may be further configured to control to stop supply of voltage from the power supply unit 120 to the liquid j et device 210 , e . g . until a next action or input of a user of the inhalation device 100 to cause the inhalation device to generate an aerosol is received .

Although detailed embodiments have been described, they only serve to provide a better understanding of the invention defined by the independent claims , and are not to be seen as limiting .