An electrically heated aerosol-generating system

0001The present invention relates to a method of controlling an electrically heated aerosol-generating system, a method of controlling an electrically heated aerosol-generating device, and the associated electrically heated aerosol-generating system and device.

0002An example of such an electrical system having a portable device and a primary charging device is an electrically operated smoking disclosed in <patcit id="pcit0001" dnum="WO2013102612A2"><text>WO 2013/102612 A2</text></patcit>. Electrically operated smoking systems significantly reduce sidestream smoke, as compared to lit-end smoking devices, while permitting a consumer to selectively activate the smoking system during the smoking experience. Electrically operated smoking systems typically include an aerosol-generating device having a housing for receiving an aerosol-generating article or a smoking article, heating elements to generate an aerosol, a power source and the necessary electronic circuitry. The circuitry may be, for example, circuitry for controlling the heating and charging of the aerosol-generating device. Having a portable device and primary charging device provides the advantage of a small aerosol-generating device being the portable device that is easy to hold and use, but also the ability to quickly and conveniently recharge the aerosol generating device for repeated use.

0003Despite such known systems, there still remains the need to enable improve the speed and efficiency of the power supply charging process. That is, the charging of the charging device power supply and the charging of the aerosol-generating device power supply.

0004The present invention is defined by the appended claims.

0005According to an embodiment of the present invention, there is provided a method of controlling an electrically heated aerosol-generating system. The electrically heated aerosol-generating system comprises a charging device comprising a rechargeable power supply, and an electrically heated aerosol-generating device configured to receive an aerosol-generating substrate comprising a rechargeable power supply, and at least one electrical heating element. The method comprises: monitoring the ambient temperature adjacent the charging device; determining a charging current, for charging the rechargeable power supply of the charging device, in dependence on the ambient temperature adjacent the charging device; and charging the rechargeable power supply of the charging device at the determined charging current. Such that when the ambient temperature adjacent the charging device is within a first pre-determined temperature range, the charging current is less than about 0.1 C; when the ambient temperature adjacent the charging device is within a second pre-determined temperature range, the charging current is greater than about 0.1 C; and, when the ambient temperature adjacent the charging device is above a pre-determined temperature, preventing charging of the rechargeable power of the charging device.

0006Providing such a charging method enables the rechargeable power supply of the charging device to be recharged at a substantially optimum rate while reducing the risk of damaging the rechargeable power supply due to supplying a charging current that is too large for the current status of the power supply.

0007As used herein, the term "C" refers to a charging current, where 1 C equates to 1 A for a 1000 mAh rechargeable power supply. That is to say, the charging current at which the capacity of the rechargeable power supply is supplied in one hour.

0008In one embodiment, the first temperature range is between about 0 degrees C and about 10 degrees C, and the second temperature range is between about 10 degrees C and about 45 degrees C.

0009In a preferred embodiment, when the ambient temperature adjacent the charging device is within the second pre-determined temperature range, the charging current is about 0.2 C.

0010The rechargeable power supply of the charging device may be configured to allow fast charging of the power supply. In this embodiment, when the ambient temperature adjacent the charging device is within the second pre-determined temperature range, the fast charging current is about 1 C. The method may comprise receiving an input from the user requesting that the charging device power supply is fast charged. In addition, or alternatively, the method may comprise determining the type of input power supply providing the power to recharge the charging device power supply, and determining the charging current accordingly. For example, if the input power supply cannot provide sufficient power to fast charge the rechargeable power supply, a charging current of 0.2 C is selected.

0011Given the above, it will be appreciated that the first and second temperature ranges, and the associated charging currents, may be altered by one of ordinary skill in the art in dependence on the type of power supply used.

0012The method may further comprise, when the rechargeable power supply of the charging device is being charged, indicating to a user which charging current is being provided to the power supply. The step of indicating which charging current is being provided preferably utilises at least one of: a visual indicator, such as a light, or series of lights; a sound, or series of sounds; and a tactile indicator. The tactile indicator may be a vibration or series of vibrations. The visual indicator may be a digital display. The digital display may provide an estimate of the time required to fully charge the charging device rechargeable power supply.

0013The method preferably further comprises the steps of: determining a discharging current for the rechargeable power supply of the charging device, for charging the rechargeable power supply of the electrically heated aerosol-generating device; and charging the rechargeable power supply of the electrically heated aerosol-generating device at the determined discharge current. Such that when the ambient temperature adjacent the charging device is within a third pre-determined temperature range, the discharging current is between about 0.1 C and about 0.3 C; when the ambient temperature adjacent the charging device is within a fourth pre-determined temperature range, the discharging current is between about 0.8 C and about 1.2 C; and when the ambient temperature adjacent the charging device is above a pre-determined temperature, preventing discharging of the rechargeable power of the charging device.

0014Providing such a charging method enables the rechargeable power supply of the electrically heated aerosol-generating device to be recharged at a substantially optimum rate while reducing the risk of damaging the rechargeable power supply of the charging device due to providing a charging current that is too large for the current status of the power supply. As will be appreciated, the discharging current of the charging device power supply is substantially equivalent to the charging current of the electrically heated aerosol-generating device power supply.

0015In one embodiment, the third temperature range is between about -10 degrees C and about 0 degrees C, and the fourth temperature range is between about 0 degrees C and about 45 degrees C.

0016In a preferred embodiment, when the ambient temperature adjacent the charging device is within a third pre-determined temperature range, the discharging current is about 0.2 C, and when the ambient temperature adjacent the charging device is within a fourth pre-determined temperature range, the discharging current is about 1 C.

0017The method may further comprise, when the rechargeable power supply of the charging device is being discharged, indicating to a user which discharging current is being provided to the power supply of the electrically heated aerosol-generating device. The step of indicating which discharging current is being provided preferably utilises at least one of: a visual indicator, such as a light, or series of lights; a sound, or series of sounds; and a tactile indicator. The tactile indicator may be a vibration or series of vibrations. The visual indicator may be an electronic display. The electronic display may provide an estimate of the time required to fully charge the electrically heated aerosol-generating device rechargeable power supply.

0018The method preferably further comprises monitoring the ambient temperature adjacent the electrically heated aerosol-generating device, and providing a charging current to the rechargeable power supply of the electrically heated aerosol-generating device for recharging the power supply, in dependence on the ambient temperature adjacent the device. Such that when the ambient temperature adjacent the electrically heated aerosol-generating device is within a pre-determined temperature range, providing a charging current of about 10 C to the power supply; and when the ambient temperature adjacent the electrically heated aerosol-generating device is without the pre-determined temperature range, preventing a charging current from being supplied to the power supply.

0019In a preferred embodiment, the charging current of about 10 C is provided to the power supply when the pre-determined temperature range is about 0 degrees C to about 35 degrees C.

0020In one embodiment, the step of monitoring the ambient temperature is preferably performed with a frequency of about once per minute to about 5 time per minute. Preferably, the ambient temperature is monitored once per minute. In this embodiment, the step of determining a charging current is performed in dependence on an average of the monitored ambient temperature, preferably a weighted average. The average may be calculated using two, three, four or more measurements. Where used, the weighting applied to each successive measurement may decrease in an arithmetical progression, or in a geometric progression.

0021In a preferred embodiment, a weighted average is used, where the weighted average is calculated using the present measured ambient temperature and the previous weighted average. The present measurement is given a weight of between about 10% and about 50%, and the previous weighted average is given a weight of between about 90% and about 50% accordingly. The weightings applied are preferably chosen in dependence on the overall heat transfer coefficient of the rechargeable power supply and surrounding air, such that the weighting produces an approximation to the heating rate or cooling rate of the rechargeable power supply. The initial weighted average is set to the first measurement of ambient temperature.

0022In one example, the present measurement is given a weight of about 20%, and the previous weighted average is given a weight of about 80%. Advantageously, such weightings approximate the relatively slow heating rate or cooling rate of the rechargeable power supplies of the systems described herein.

0023In one embodiment, the operational temperature range is between about 10 degrees C and about 70 degrees C, more preferably between about 12 degrees C and about 65 degrees C. When the temperature is below the lower end of the operational temperature range the resistance of the heating element is low as compared to the resistance of the heating element when the temperature is within the operational range. Thus, in accordance with Ohm's law, the current drain is higher and, without increasing the size and capacity, the power supply of the electrically heated aerosol-generating device cannot provide the required current.

0024Again, the step of monitoring the ambient temperature adjacent the aerosol-generating device is preferably performed with a frequency of about once per minute to about 5 time per minute. Preferably, a similar weighted average process is used as described above. The present measurement is given a weight of between about 10% and about 50%, and the previous weighted average is given a weight of between about 90% and about 50% accordingly. The weightings applied are preferably chosen in dependence on the overall heat transfer coefficient of the rechargeable power supply and surrounding air, such that the weighting produces an approximation to the heating rate or cooling rate of the rechargeable power supply. Again, the initial weighted average is set to the first measurement of ambient temperature.

0025In one example, the present measurement is given a weight of about 30%, and the previous weighted average is given a weight of about 70%. Advantageously, these weightings model the heating and cooling rate of the aerosol-generating device more effectively than the above described 20%/80% model used for the charging device weighted average because the thermal mass of the aerosol-generating device is less than the thermal mass of the charging device. Therefore, the aerosol-generating device heats or cools more quickly than the charging device.

0026According to a further embodiment of the present invention, there is provided an electrically heated aerosol-generating system. The system comprises: an electrically heated aerosol-generating device configured to receive an aerosol-generating substrate. The device comprises: a heating element; a rechargeable power supply for powering the heating element. The system further comprises a charging device configured to receive the electrically heated aerosol-generating device. The charging device comprises: a cavity for receiving the electrically heated aerosol-generating device; a rechargeable power supply for charging the rechargeable power supply of the electrically heated aerosol-generating device; a temperature sensor for sensing the ambient temperature adjacent the charging device; and a controller for controlling the supply of power to the charging device power supply from an external power source to recharge the power supply, in dependence on the ambient temperature adjacent the charging device. Such that: when the ambient temperature adjacent the charging device is within a first pre-determined range, the controller is configured to provide a charging current of less than about 0.1 C; when the ambient temperature adjacent the charging device is within a second pre-determined range, the controller is configured to provide a charging current of greater than about 0.1 C; and when the ambient temperature adjacent the charging device is above a predetermined temperature, preventing charging of the rechargeable power of the charging device.

0027Providing such a system enables the rechargeable power supply of the charging device to be recharged at a substantially optimum rate while reducing the risk of damaging the rechargeable power supply due to supplying a charging current that is too large for the current status of the power supply.

0028In one embodiment, the first temperature range is between about 0 degrees C and about 10 degrees C, and the second temperature range is between about 10 degrees C and about 45 degrees C.

0029In a preferred embodiment, when the ambient temperature adjacent the charging device is within the second pre-determined temperature range, the charging current is about 0.2 C.

0030The rechargeable power supply of the charging device may be configured to allow fast charging of the power supply. In this embodiment, when the ambient temperature adjacent the charging device is within the second pre-determined temperature range, the fast charging current is about 1 C. The controller may be configured to receive an input from the user requesting that the charging device power supply is fast charged. In addition, or alternatively, the controller may be configured to determine the type of input power supply providing the power to recharge the charging device power supply, and determine the charging current accordingly. For example, if the input power supply cannot provide sufficient power to fast charge the rechargeable power supply, a charging current of 0.2 C is selected.

0031Preferably, the charging device comprises means for receiving external electrical power to recharge the rechargeable power supply.

0032The charging device may further comprise an indicator for indicating to a user which charging current is being provided to the power supply, when the rechargeable power supply of the charging device is being charged. The indicator preferably comprises at least one of: a visual indicator, such as a light, or series of lights; a sound, or series of sounds; and a tactile indicator. The tactile indicator may be a vibration, or series of vibrations. The visual indicator may be a digital display. The digital display may provide an estimate of the time required to fully charge the charging device rechargeable power supply.

0033Preferably, the charging device controller is further configured to control the supply of power from the charging device power supply to the electrically heated aerosol-generating device power supply to recharge the power supply. Such that: when the ambient temperature adjacent the charging device is within a third pre-determined temperature range, the controller is configured to provide a discharging current between about 0.1 C and about 0.3 C to the power supply of the electrically heated aerosol-generating device; when the ambient temperature adjacent the charging device is within a fourth predetermined temperature range, the controller is configured to provide a discharging current between about 0.8 C and about 1.2 C to the power supply of the electrically heated aerosol-generating device; and when the ambient temperature adjacent the charging device is above a predetermined temperature, the controller is configured to prevent discharging of the rechargeable power of the charging device.

0034Providing such a controller enables the rechargeable power supply of the electrically heated aerosol-generating device to be recharged at a substantially optimum rate while reducing the risk of damaging the rechargeable power supply of the charging device due to providing a charging current that is too large for the current status of the power supply. Aswill be appreciated, the discharging current of the charging device power supply is substantially equivalent to the charging current of the electrically heated aerosol-generating device power supply.

0035In one embodiment, the third temperature range is between about -10 degrees C and about 0 degrees C, and the fourth temperature range is between about 0 degrees C and about 45 degrees C.

0036In a preferred embodiment, when the ambient temperature adjacent the charging device is within a third pre-determined temperature range, the discharging current is about 0.2 C, and when the ambient temperature adjacent the charging device is within a fourth pre-determined temperature range, the discharging current is about 1 C.

0037Preferably, the charging device power supply is a lithium-ion battery. More preferably, the charging device power supply is a lithium cobalt oxide battery.

0038Preferably, the electrically heated aerosol-generating device power supply is also a lithium-ion battery. More preferably, the electrically heated aerosol-generating device power supply is a lithium iron phosphate battery.

0039The charging device may further comprise an indicator for indicating toa user which discharging current is being provided to the power supply of the electrically heated aerosol-generating device when the rechargeable power supply of the charging device is being discharged. The indicator preferably comprises at least one of: a visual indicator, such as a light, or series of lights; a sound, or series of sounds; and a tactile indicator. The tactile indicator may be a vibration or series of vibrations. The visual indicator may be an electronic display. The electronic display may provide an estimate of the time required to fully charge the electrically heated aerosol-generating device rechargeable power supply.

0040The charging device may include a display, or further display, (for example a digital display) indicating information to the user. For example, the display may indicate smoking article consumption, energy usage or other information. The display may further indicate when the electrically heated aerosol-generating device power supply has sufficient charge to be used to consume a smoking article.

0041Preferably, the charging device further comprises a housing, and a lid attached to the housing. The lid is configured to close over the open end of the cavity, such that the electrically heated aerosol-generating device is not accessible when the lid is in the closed position. The charging device may further comprise means for preventing the supply of power to the electrically heated aerosol-generating device when the lid is open.

0042The lid is preferably a hinge lid. Preferably, the hinge extends across the top of the housing from the front wall to the back wall. The hinge may comprise a spring configured to retain the lid in the first position. The hinge may also comprise a damper configured to damp the motion of the lid when the lid is moved from the second position to the first position. Alternatively, the hinge may comprise a spring configured to retain the lid in the second position. In this alternative, the lid is preferably provided with means for retaining the lid in the first position, the retaining means being configured to provide sufficient force to overcome the force applied to the lid by the spring.

0043The retaining means may comprise at least one magnet and at least one corresponding ferrous element. The at least one magnet being provided in the housing of the primary device, and the ferrous element being provided in the lid. Alternatively, the retaining means may be a latch type arrangement.

0044The hinge lid may form the entire top of the housing. In this alternative, the hinge may be internal to the lid, and be adjacent a side wall of the housing.

0045The housing of the charging device preferably comprises a front wall, a back wall, a bottom wall, a top wall, a first side wall and a second side wall.

0046The terms "front", "back", "upper, "lower", "side", "top", "bottom", "left", "right" and other terms used to describe relative positions of the components of the charging device and electrically heated aerosol-generating device refer to the charging device in an upright position with the opening of the cavity configured to receive the electrically heated aerosol-generating device at the top end.

0047The term "longitudinal" refers to a direction from bottom to top or vice versa. The term "transverse" refers to a direction perpendicular to the longitudinal direction.

0048The charging device may be a substantially rectangular parallelepiped comprising two wider walls spaced apart by two narrower side walls and top and bottom walls. The electrically heated aerosol-generating device is preferably elongate.

0049The temperature sensor is preferably provided in contact with a wall of the charging device housing to enable an improved correlation between the measured temperature and the ambient temperature. The temperature sensor may be a thermocouple or a thermistor.

0050The electrically heated aerosol-generating device of the system preferably further comprises a temperature sensor for sensing the ambient temperature adjacent the device. The charging device controller is preferably further configured to control the supply of power from the charging device power supply to the electrically heated aerosol-generating device power supply to recharge the power supply in dependence on the ambient temperature adjacent the electrically heated aerosol-generating device. Such that: when the ambient temperature adjacent the electrically heated aerosol-generating device is within a pre-determined temperature range, the controller is configured to provide a charging current of about 10 C to the power supply; and when the ambient temperature adjacent the electrically heated aerosol-generating device is without the pre-determined temperature range, the controller is configured to prevent a charging current from being supplied to the power supply.

0051In a preferred embodiment, the charging current of about 10 C is provided to the power supply when the pre-determined temperature range is about 0 degrees C to about 35 degrees C.

0052The temperature sensor of the electrically heated aerosol-generating device is preferably provided in contact with a wall of a housing of the device to enable an improved correlation between the measured temperature and the ambient temperature. The temperature sensor may be a thermocouple or a thermistor. Alternatively, the heating element may be used as a thermistor to measure the temperature.

0053The device may further comprise an indicator for indicating to a user when the ambient temperature adjacent the device is without the pre-determined temperature range.

0054Preferably, the aerosol-generating device is designed to receive an aerosol-generating substrate in the form of an aerosol-generating article, and be held by a user during a smoking experience. The aerosol-generating device power supply is preferably adapted to heat up the aerosol-forming substrate to operating temperature before aerosol generating begins. The power supply in the aerosol-generating device is also adapted to maintain the temperature of the aerosol-forming substrate during the aerosol generation.

0055The aerosol-generating device is preferably of a similar size to or slightly larger than a lit-end cigarette. Thus, the device can be held between the user's fingers in a similar way to a lit-end cigarette.

0056The aerosol-generating substrate is preferably in the form of an aerosol-generating article, or a smoking article.

0057As used herein, the term 'aerosol-forming substrate' relates to a substrate capable of releasing volatile compounds that can form an aerosol. Such volatile compounds are released by heating the aerosol-forming substrate. An aerosol-forming substrate may be solid or liquid or comprise both solid and liquid components. An aerosol-forming substrate may be adsorbed, coated, impregnated or otherwise loaded onto a carrier or support. An aerosol-forming substrate may conveniently be part of an aerosol-generating article or smoking article.

0058An aerosol-forming substrate may comprise nicotine. An aerosol-forming substrate may comprise tobacco, for example may comprise a tobacco-containing material containing volatile tobacco flavour compounds, which are released from the aerosol-forming substrate upon heating. In preferred embodiments an aerosol-forming substrate may comprise homogenised tobacco material, for example cast leaf tobacco. An aerosol-forming substrate may comprise at least one aerosol-former, such as propylene glycol or glycerine.

0059As used herein, the terms 'aerosol-generating article' and 'smoking article' referto an article comprising an aerosol-forming substrate that is capable of releasing volatile compounds that can form an aerosol. For example, an aerosol-generating article may be a smoking article that generates an aerosol that is directly inhalable into a user's lungs through the user's mouth. An aerosol-generating article may be disposable. The term 'aerosol-generating article' is generally used hereafter.

0060The aerosol formed by heating the aerosol-forming substrate may contain fewer known harmful constituents than would be produced by combustion or pyrolytic degradation of the aerosol-forming substrate. An aerosol-generating article may be, or may comprise, a tobacco stick.

0061The aerosol-forming substrate preferably comprises a tobacco-containing material containing volatile tobacco flavour compounds which are released from the substrate upon heating. Alternatively, the aerosol-forming substrate may comprise a non-tobacco material. Preferably, the aerosol-forming substrate further comprises an aerosol former. Examples of suitable aerosol formers are glycerine and propylene glycol.

0062The aerosol-forming substrate may be a solid substrate. The solid substrate may comprise, for example, one or more of: powder, granules, pellets, shreds, spaghettis, strips or sheets containing one or more of: herb leaf, tobacco leaf, fragments of tobacco ribs, reconstituted tobacco, homogenised tobacco, extruded tobacco and expanded tobacco. Optionally, the solid substrate may contain additional tobacco or non-tobacco volatile flavour compounds, to be released upon heating of the substrate. Optionally, the solid substrate may be provided on or embedded in a thermally stable carrier. The carrier may take the form of powder, granules, pellets, shreds, spaghettis, strips or sheets. Alternatively, the carrier may be a tubular carrier having a thin layer of the solid substrate deposited on its inner surface, or on its outer surface, or on both its inner and outer surfaces. Such a tubular carrier may be formed of, for example, a paper, or paper like material, a non-woven carbon fibre mat, a low mass open mesh metallic screen, or a perforated metallic foil or any other thermally stable polymer matrix. The solid substrate may be deposited on the surface of the carrier in the form of, for example, a sheet, foam, gel or slurry. The solid substrate may be deposited on the entire surface of the carrier, or alternatively, may be deposited in a pattern in order to provide a non-uniform flavour delivery during use. Alternatively, the carrier may be a non-woven fabric orfibre bundle into which tobacco components have been incorporated. The non-woven fabric or fibre bundle may comprise, for example, carbon fibres, natural cellulose fibres, or cellulose derivative fibres.

0063The aerosol-forming substrate may be a liquid substrate and the smoking article may comprise means for retaining the liquid substrate. The aerosol-forming substrate may alternatively be any other sort of substrate, for example, a gas substrate, or any combination of the various types of substrate.

0064Any feature in one aspect or embodiment of the invention may be applied to other aspects or embodiments of the invention, in any appropriate combination. In particular, method aspects or embodiments may be applied to apparatus aspects or embodiments, and vice versa. More specifically, the controllers described herein in relation to the charging device and the electrically heated aerosol-generating device may be configured to carry out any method aspects or embodiments in relation to the control of the power supplies. Furthermore, any, some and/or all features in one aspect or embodiment can be applied to any, some and/or all features in any other aspect or embodiment, in any appropriate combination.

0065It should also be appreciated that particular combinations of the various features described and defined in any aspects or embodiments of the invention can be implemented and/or supplied and/or used independently.

0066The invention will be further described, by way of example only, with reference to the accompanying drawings in which: <ul id="ul0001" list-style="none" compact="compact"><li><figref idref="f0001">Figures 1</figref> show schematic diagrams of a charging unit and electrically heated aerosol-generating device according to the invention;</li><li><figref idref="f0002">Figure 2</figref> show a system of the present invention having a charging unit and an electrically heated aerosol-generating device;</li><li><figref idref="f0003">Figure 3</figref> shows a flow diagram of the control steps for charging the charging unit;</li><li><figref idref="f0004">Figure 4</figref> shows a flow diagram of the control steps for discharging the charging unit;</li><li><figref idref="f0005">Figure 5</figref> shows a flow diagram of the control steps for charging the electrically heated aerosol-generating device; and</li><li><figref idref="f0006">Figure 6</figref> shows a flow diagram of the control steps for discharging the electrically heated aerosol-generating device.</li></ul>

0067<figref idref="f0001">Figure 1(a)</figref> shows a charging device 100. The charging device 100 in this example is for an electrically heated smoking system. <figref idref="f0001">Figure 1(b)</figref> shows an electrically heated aerosol-generating device 102. The electrically heated aerosol-generating device 102 is adapted to receive a smoking article 104 comprising an aerosol-forming substrate. The charging device 100 comprises a rechargeable battery 106, control electronics 108, and electrical contacts 110 configured to provide electrical power to the aerosol-generating device, from the battery 106, when the aerosol-generating device is in connection with the electrical contacts 110. The charging device further comprises a temperature sensor 111. The rechargeable battery 108 is a lithium cobalt oxide battery.

0068The charging device is configured to charge the aerosol-generating device utilising the battery 106, in dependence on the measured temperature. The electrical contacts 110 are provided adjacent the bottom of a cavity 112. The cavity is configured to receive the aerosol-generating device 102. A lid 114 is provided that is configured to secure the aerosol-generating device 102 within the cavity 112 of the charging device 100. The components of the charging device 100 are housed within the housing 116. The lid 114 is coupled to the housing 116 by hinge 118.

0069In addition, the charging device 100 is provided with a series of three indicators 120, 122 and 124. The indicator 120 is provided to indicate the level of charge remaining in the charging device battery 106. The indicator 120 may indicate the percentage of the charge remaining in the charging device battery. For example, 100% would indicate that the battery 106 is fully charged, and 50% would indicate that the battery 106 is half charged. Alternatively the indicator 120 may simply indicated when the charging device battery requires recharging.

0070The second indicator 122 is provided to indicate that the aerosol-generating device 102 is fully charged, and ready to be used to generate an aerosol. The indicator 122 only indicates this state of readiness once the aerosol-generating device is capable of providing sufficient power to provide the user with a complete smoking experience; for example, sufficient power to aerosolise the entire aerosol forming substrate 104, or sufficient power to generate a predetermined number of puffs.

0071The third indicator 124 is provided to indicate the charging regime being used to recharge the battery 106 from the external power supply (not shown). The various charging regimes are described in detail below.

0072The aerosol-generating device 102 comprises a rechargeable battery 126, control electronics 128 and electrical contacts 130. As described above, the rechargeable battery 126 of the aerosol-generating device 102 is configured to receive a supply of power from the charging device battery 106 when the electrical contacts 130 are in contact with the electrical contacts 110 of the charging device 100. The aerosol-generating device further comprises a temperature sensor 131 for measuring the ambient temperature adjacent the device. The rechargeable battery 126 is a lithium iron phosphate battery.

0073The aerosol-generating device 102 further comprises a cavity 132 configured to receive the aerosol-generating article 104. A heater 134, in the form of, for example, a blade heater, is provided at the bottom of the cavity 132. In use, the user activates the aerosol-generating device 102, and power is provided from the battery 126 via the control electronics 128 to the heater 134. The heater is heated to a standard operational temperature that is sufficient to generate an aerosol from the aerosol-forming substrate of the aerosol-generating article 104. The components of the aerosol-generating device 102 are housed within the housing 136.

0074<figref idref="f0002">Figure 2</figref> shows the aerosol-generating device 102 housed within the cavity of the charging device 100. The lid 114 is shown in a closed position. In this closed position the lid is configured to act on the aerosol-generating device 102 such that a good electrical connection is made between the charging device and the aerosol-generating device. As can be seen, the electrical contacts 130 of the aerosol-generating device are engaged with the electrical contacts 110 of the charging device.

0075The control electronics 108 of the charging device are configured both to control the charging of the charging device battery 106 by the external power supply, and to control the charging of the aerosol-generating device battery 126, in dependence on the ambient temperature. The control methods utilised by the control electronics 108 are described with reference to <figref idref="f0003">Figures 3</figref> and <figref idref="f0004">4</figref> respectively.

0076In use, when the user connects the charging device to an external power supply, the control electronics 108 determine the appropriate charging current using the following method shown in <figref idref="f0003">Figure 3</figref>.

0077The ambient temperature adjacent the charging device is measured using temperature sensor 111, and a weighted average of the ambient temperature is calculated. The current temperature measurement is given a weighting of 20%, and the previous weighted average is given a weighting of 80%. Where the temperature measurement is the first temperature measurement, the weighted average is set to the current temperature.

0078The control electronics 108 then determine whether the weighted average temperature is within a first range of temperatures. In one specific example, the first range of temperatures is 0 degrees C to 10 degrees C. If the weighted average temperature is within the range, the control electronics provides a charging current to the battery 106 of less than 0.1 C.

0079If the weighted average temperature is not within the range, the control electronics determines whether the weighted average temperature is within a second range of temperatures. In one specific example, the second range of temperatures is 10 degrees C to 45 degrees C. If the weighted average temperature is not within the second range of temperatures the battery 106 is without the operational temperature range and no charging is initiated to protect the battery from damage. The indicator 124 indicates this to the user.

0080If the weighted average temperature is within the second temperature range, the control electronics 108 determines whether fast charging is required, if so, a charging current of approximately 1 C is provided, if not a charging current of approximately 0.2 C is provided.

0081At each stage a charging current is determined, after a period of 1 minute the process is repeated.

0082In use, when the user inserts the aerosol-generating device into the charging device and activates charging of the aerosol-generating device, the control electronics 108 determine the appropriate charging current using the following method shown in <figref idref="f0004">Figure 4</figref>.

0083Again, the ambient temperature adjacent the charging device is measured using temperature sensor 111, and a weighted average of the ambient temperature is calculated. The current temperature measurement is given a weighting of 20%, and the previous weighted average is given a weighting of 80%. Where the temperature measurement is the first temperature measurement, the weighted average is set to the current temperature.

0084The control electronics 108 then determine whether the weighted average temperature is within a third range of temperatures. In one specific example, the third range of temperatures is -10 degrees C to 0 degrees C. If the weighted average temperature is within the range, the control electronics provides a charging current to the battery 126 of approximately 0.2 C.

0085If the weighted average temperature is not within the range, the control electronics determines whether the weighted average temperature is within a fourth range of temperatures. In one specific example, the second range of temperatures is 0 degrees C to 45 degrees C. If the weighted average temperature is not within the fourth range of temperatures the battery 126 is without the operational temperature range and no charging is initiated to protect the battery from damage. The indicator 124 indicates this to the user.

0086If the weighted average temperature is within the fourth temperature range, the control electronics 108 provides a charging current of approximately 1 C to the battery 126.

0087At each stage a charging current is determined, after a period of 1 minute the process is repeated.

0088Furthermore, the aerosol-generating device control electronics 128 are configured both to control the charging of the device battery 126, and to control the use of the device in dependence on the ambient temperature. The control methods utilised by the control electronics 128 are described with reference to <figref idref="f0005">Figures 5</figref> and <figref idref="f0006">6</figref>.

0089When the user initiates the charging of the aerosol-generating device, the control electronics 128 of the aerosol-generating device are configured to carry out the method shown in <figref idref="f0005">Figure 5</figref> to determine whether the battery 126 may be charged.

0090The ambient temperature adjacent the device 102 is measured using temperature sensor 131, and a weighted average of the ambient temperature is calculated. The current temperature measurement is given a weighting of between 10-50%, and the previous weighted average is given a weighting of 90-50%. Where the temperature measurement is the first temperature measurement, the weighted average is set to the current temperature.

0091The control electronics 128 then determine whether the weighted average temperature is within a range of operational temperatures. In one specific example, the operational range of temperatures is 0 degrees C to 35 degrees C. If the weighted average temperature is within the range, the control electronics enables a charging current of approximately 10 C to be provided to the battery 126. However, the charging device temperature may change this charging rate in accordance with the control method described above.

0092If the weighted average temperature is not within the range, the control electronics prevents the battery 126 from being charged to reduce the risk of damaging the battery.

0093At each stage a charging current is determined, after a period of 1 minute the process is repeated.

0094Finally, when the user initiates the aerosol-generating device to generate an aerosol, the method of <figref idref="f0006">Figure 6</figref> is carried out by the controller 128.

0095Again, the ambient temperature adjacent the device 102 is measured using temperature sensor 131, and a weighted average of the ambient temperature is calculated. The current temperature measurement is given a weighting of 10-50%, and the previous weighted average is given a weighting of 90-50%. Where the temperature measurement is the first temperature measurement, the weighted average is set to the current temperature.

0096The control electronics 128 then determine whether the weighted average temperature is within a range of operational temperatures. In one specific example, the operational range of temperatures is 12 degrees C to 65 degrees C. If the weighted average temperature is within the range, the control electronics enables power to be supplied to the heating element 134.

0097If the weighted average temperature is not within the operational range of temperatures the control electronics 128 prevents power being supplied to the heating element 134.

0098After a period of 1 minute the process is repeated.

0099When the temperature is below the lower end of the operational temperature range, the resistance of the heating element will be too low for the battery 126 to supply sufficient current. The heating element in one specific example has a resistance of approximately 0.7 Ohm at 0 degrees C, and approximately 2 Ohm at 300 degrees C (the temperature at which the heating element is held to generate an aerosol). The nominal voltage of the battery is 3.3 V at 0 degrees C, and during operation the nominal voltage of the battery at 300 degrees C is 3.0 V. Therefore, at 0 degrees C, the current drain will be 3.3 / 0.7 = 4.7 A, but at 300 degrees C, the current drain will be 3.0 / 2 = 1.5.

0100When the temperature is above the higher end of the operational temperature range, the use of the aerosol-generating device may increase the temperature of the control electronics to above its upper design temperature of 80 degrees C, which could result in unreliable performance.

0101Briefly, when the control electronics 128 provide power to the heating element 134, the heating element 134 heats to approximately 300 degree C. The heating element 134 is in contact with the aerosol-generating substrate of the aerosol-generating article 104. This causes the aerosol-generating substrate to generate an aerosol which can be inhaled by the user when they draw on the aerosol-generating article 104.

0102The invention has been exemplified above by reference to the accompanying figures. However, it will be appreciated that the control methods described herein may be applicable to other types of portable device.