Frequency determination of dielectric heater of aerosol-forming article and device

Abstract

A portable and hand-held aerosol-forming device for forming aerosol for human inhalation from an aerosol-forming article by dielectric heating, comprising: a dielectric heating arrangement including an oscillation circuit, the arrangement generating of an alternating electric field for performing the dielectric heating, a heating chamber or receiving space configured to removably receive the aerosol-forming article, a sensing device arranged outside of the generated alternating electric field, wherein the sensing device is configured to detect a parameter indicative of a frequency of the alternating electric field.

Description

[0001] FREQUENCY DETERMINATION OF DIELECTRIC HEATER OF AEROSOL-FORMING ARTICLE AND DEVICE

[0002] The present disclosure relates to an aerosol-forming device for forming aerosol from an aerosol-forming article by dielectric heating, an aerosol-forming system, particularly comprising the aerosol-forming device and the aerosol-forming article, and a method of monitoring dielectric heating of an aerosol-forming article in an aerosol-forming device.

[0003] Aerosol-forming or aerosol-generating devices are typically designed as handheld devices that can be used by a user for consuming or experiencing, for instance in one or more usage sessions, aerosol generated from an aerosol-forming substrate or an aerosol-forming article, for example by heating. The aerosol-forming devices the present disclosure pertains to are mainly directed to the field of tobacco and tobacco-substitute products, as well as e-vapor devices, for example heated tobacco products (HTP), heat-not-burn devices, electronic cigarettes, e-vapor devices, and / or vaporisers. The aerosol-forming devices of the present disclosure may also pertain to other types of inhalers, dispensers, or atomizers, for example inhalers, dispensers, or atomizers for medical applications.

[0004] Typical aerosol-forming systems can be designed as one-part systems or devices including an aerosol-forming device that can be operated by a user to generate aerosol. Alternatively, aerosol-forming systems can be designed as two-part systems or devices comprising an aerosolforming device and a companion device for storing and / or charging the aerosol-forming device. In either design or configuration, the aerosol-forming system or device can be used by a user for consuming or inhaling, for instance in one or more usage sessions, aerosol generated based on heating an aerosol-forming article or substrate couplable to the aerosol-forming system. In the context of the present disclosure, an aerosol-forming device can refer to both a one-part device and a two-part device, unless explicitly specified otherwise.

[0005] The aerosol-forming article, also referred to as aerosol-generating article or a pod, can comprise an aerosol-generating or aerosol-forming substrate, for example a liquid aerosolforming substrate, such as a tobacco or nicotine-containing substrate. The aerosol-forming article may be configured in shape and size to be inserted at least partially into the aerosol-forming device or system. In conventional systems or devices, the aerosol-forming article is usually formed as a pod, cartridge or stick that can be at least partly inserted into a cavity, receptacle or heating chamber of the aerosol-forming device for aerosol consumption.

[0006] Exemplary aerosol-forming substrates can comprise liquid and / or solid substrate material, such as tobacco material or tobacco cast leaves (TCL) material. The substrate material can, for example, be assembled, often with other elements or components, to form a substantially stickshaped or pod-shaped aerosol-forming article. Such a stick or aerosol-forming article can be configured in shape and size to be inserted at least partially into the aerosol-forming device. Theaerosol-forming device may comprise a heating element or heater device for heating the aerosolforming article and / or the aerosol-forming substrate. The heating element or heater device may be part of the aerosol-forming article and / or the aerosol-forming device. Alternatively or additionally, aerosol-forming substrates can comprise one or more liquids and / or solids, which can, for example, be supplied to the aerosol-forming device in the form of a cartridge or container. Corresponding exemplary aerosol-forming articles can, for example, comprise a cartridge containing or fillable with the liquid and / or solid substrate, which can be vaporized during aerosol consumption by the user based on heating the substrate and / or liquid. Usually, such cartridge or container can be coupled to, attached to or at least partially inserted into the aerosol-forming device. Alternatively, the cartridge may be fixedly mounted to the aerosol-forming device and refilled by inserting liquid and / or solid into the cartridge. The aerosol generated from the aerosolforming substrate or article may comprise or include one or more of nicotine, aroma, sugar, moisturising agent, botanicals, preservative, flavouring, for example cocoa, liquorice, menthol and lactic acid or other additives. The aerosol generated from the aerosol-forming substrate or article may additionally or alternatively comprise one or more pharmaceutical agents or drugs and may include one or more adjuvants.

[0007] For generating the aerosol during use or consumption, heat can be supplied by a heating element, heater device or heat source to heat at least a portion or part of the aerosol-forming substrate. The heating element, heater device or heat source can be arranged in the handheld device or a handheld part of the aerosol-forming device. Alternatively or additionally, at least a part of or the entire heating element or heater device or heat source can be fixedly associated with or arranged within an aerosol-forming article, for instance in the form of a stick or cartridge, which can be attached to and / or powered by the handheld device or handheld part of the aerosolforming device.

[0008] Recently, dielectric or microwave heating arrangements have been proposed for dielectrically heating and vaporizing ingredients of the aerosol-forming substrate, taking advantage of the relative permittivity of the aerosol-forming substrate, by using electric energy from or stored in an energy storage or battery of the aerosol-forming device.

[0009] As used herein, a battery of the aerosol-forming device can generally refer to an energy storage of the aerosol-forming device configured to store electrical energy. Accordingly, the term energy storage can include one or more batteries, one or more capacitors, one or more accumulators or other types of energy storage. Also, any reference to a battery herein can include a plurality of batteries.

[0010] Typically, aerosol-forming devices comprise an energy storage, for example a battery, providing the electrical energy needed to operate the aerosol-forming device and especially for heating the aerosol-forming substrate and / or article, for example to generate aerosol in one ormore usage sessions using one or more aerosol-forming articles. The battery may, for example, be a lithium-ion battery.

[0011] As used herein, a usage session may refer to a period of time, during which a user may use the device to generate, consume, experience or inhale aerosol using the aerosol-forming device. Therein, a usage session may be finite. In other words, a usage session may have a start, an end and a duration. The duration of the usage session as measured by time may be influenced by use during the usage session. The duration of the usage session may have a maximum duration determined by a maximum time from the start of the usage session. The duration of the usage session may be less than the maximum time if one or more monitored parameters reaches a predetermined threshold before the maximum time from the start of the usage session. By way of example, the one or more monitored parameters may comprise one or more of: i) a cumulative puff count of a series of puffs drawn by a user since the start of the usage session, and ii) a cumulative volume of aerosol evolved from the aerosol-forming substrate since the start of the usage session.

[0012] In aerosol-forming devices, it is desirable to be able to control how much heating power is applied to the aerosol-forming article for controlled vaporization and aerosolization of the substrate, to follow a predefined temperature profile, and to avoid overheating or underheating for efficient and controlled vapor and aerosol formation. On the one side, wasting power is to be avoided to increase battery lifetime as well as user experience and to reduce charging cycles. On the other side, different aerosol-forming articles may need different heating powers, for example because they contain aerosol-forming substrates of different compositions. Therefore, to provide high-quality aerosol, different heating profiles may be needed. For meaningfully controlling the heating power that is delivered to an aerosol-forming article or substrate by a dielectric heating arrangement, it may be preferred that the frequency of the radio frequency (RF) electric field is known. This may be particularly the case for freely oscillating circuits that provide for the RF oscillation, for example voltage, to the load capacitor. The frequency may change as a function of changes to the capacitance value of the load capacitor in the LC feedback loop, for example caused by temperature changes, substrate depletion level, proper insertion of the aerosol-forming article, contamination, or other factors. The same may be applicable if a resonant cavity or transmission line type dielectric heating arrangement are used, where the alternating electric field is caused by an oscillator that is connected to an amplifier, and coupled into the at least one resonant cavity and / or transmission line via a coupler. An electric field probe may be used that measures the frequency of the alternating electric field caused by the load capacitor, the resonant cavity, and / or transmission line. However, the use of an electric field probe which directly measures the frequency of the alternating electric field itself can add some additional costs and complexity to the aerosol-forming device. In addition, the electric field probe can be obstructingor otherwise require space in the heating chamber or heating zone (e.g. the space between the electrodes of the load capacitor), and could obstruct the heating chamber. In addition, the electric field probe can be subjected to strong temperature variations and particle deposits from the generated vapor and aerosol, that could render the probe inoperable. Similarly, in the e-vapor space and for liquid aerosol forming substrates and cartridges, the provision of an electric field probe at the cartridge receiving space could have the same disadvantages as described above, and the provision of an electric field probe inside the cartridge itself could be too costly and require complex electric interconnection with the holder for reading the measured values.

[0013] It may therefore be desirable to provide for an improved aerosol-forming device and / or system using dielectric heating, in which the frequency of the alternating electric field used for dielectric heating is determined with improved efficiency, for example without obstructing space in the heating chamber.

[0014] These advantages may be achieved by the features described herein.

[0015] According to an aspect of the present invention, there is provided a portable and hand-held aerosol-forming device for forming aerosol for human inhalation from an aerosol-forming article by dielectric heating, comprising: a dielectric heating arrangement including an oscillation circuit configured to oscillate freely, the arrangement generating of an alternating electric field for performing the dielectric heating, a heating chamber or receiving space configured to removably receive the aerosol-forming article, and a sensing device arranged outside of the generated alternating electric field, wherein the sensing device is configured to detect a parameter indicative of a frequency of the alternating electric field.

[0016] In the context of the present disclosure, the aerosol-forming device and / or the aerosolforming system may be a portable device and / or system. It may be battery powered. Particularly, the aerosol-forming device and / or the aerosol-forming system may be pocket-size, hand-held, suitable for one-hand use and / or may weigh less than 300 g, preferably less than 200 g. It may be shaped and / or sized to fit snugly into a user’s hand. It may be carried in jacket and / or trouser pockets. Particularly, the aerosol-forming device and / or the aerosol-forming system may be configured to provide aerosol for human inhalation and / or human consumption, particularly inhalation and / or consumption through the mouth.

[0017] In principle, aspects of the present disclosure pertain to all possible types and implementations of dielectric heating. Special use cases, using different types of dielectric heating, may pose different requirements and / or difficulties, which is why preferred implementations are also exemplarily discussed herein. However, in their most general form, the aspects of the present disclosure apply to all types of portable and hand-held aerosol-forming devices for forming aerosol for human inhalation using any kind of dielectric heating. The present disclosure is not limited in this aspect.In one example, the heating chamber or receiving space may be arranged to be subjected to the alternating electric field caused by at least two electrodes and the oscillation circuit. For instance, the oscillation circuit may be configured to provide an oscillating current and / or voltage to at least two electrical contacts couplable or coupled to at least two electrodes of a load capacitor so that an alternating electric field between the at least two electrodes may be established for performing dielectric heating, wherein the sensing device may be arranged outside of the load capacitor, i.e. outside of the volume between the electrodes. Additionally or alternatively, the dielectric heating arrangement may comprise a resonant cavity and / or a transmission line and may be configured to provide an alternating electric field for performing the dielectric heating in the resonant cavity and / or the transmission line, wherein the sensing device may be arranged outside of the resonant cavity and / or the transmission line.

[0018] That the at least two electrical contacts may be couplable or coupled to at least two electrodes of a load capacitor may mean that the electrodes constituting the load capacitor may be removably or fixedly connected to the oscillation circuit. For example, in a possible embodiment, an aerosol-forming article (e.g. a liquid cartridge or heat-not-burn stick) for use with the aerosol-forming device may comprise the electrodes constituting the load capacitor. Therefore, when the aerosol-forming article is inserted into the aerosol-forming device, the electrical contacts may be used to electrically connect the electrodes arranged in the aerosolforming article with the rest of the oscillation circuit arranged in the aerosol-forming device to electrically close the resonant feedback loop. There may be even more components arranged on the side of the aerosol-forming article. For example, also a part of the feedback loop, for example comprising at least one or two inductors, may be arranged on or in the aerosol-forming article. In this case, also these components may be electrically connected to the rest of the oscillation circuit arranged in the aerosol-forming device when the aerosol-forming article is inserted into the aerosol-forming device. To achieve this connection, the electrical contacts may be used. For the dielectric heating, it may be provided that the polarization of the electrodes is changed in radio frequency. The at least two electrical contacts may be free of pads or other shapes which might add a parasitic capacitance into the feedback loop of the oscillation circuit. Keeping the circuit, particularly the radio frequency feedback loop oscillation circuit free from such a parasitic capacitance increases its energy efficiency and avoids alterations of the oscillation frequency.

[0019] In another possible embodiment, the oscillation circuit, for example comprising a feedback loop, which in turn may comprise one or more inductors, as well as the electrodes constituting the load capacitor, may all be arranged in or on the aerosol-forming device. When the aerosol-forming article containing the aerosol-forming substrate, for example a liquid aerosol-forming substrate, is inserted into the aerosol-forming device, at least part of the aerosol-forming article is inserted between the electrodes constituting the load capacitor, i.e. into the heating chamber. The aerosol-forming substrate contained in the aerosol-forming article may therefore be dielectrically heated in the load capacitor.

[0020] That the sensing device is arranged outside of the generated alternating electric field may mean that the sensing device is arranged outside of a volume of space in which the electric field is strong enough to perform heating or meaningful heating. In other words, the sensing device may be arranged outside and / or distanced from a volume of space in which the aerosol-forming substrate contained in the aerosol-forming article is heated to form vapor and / or aerosol. The heating chamber may be formed or established between the at least two electrodes forming or constituting the load capacitor. Therefore, the heating chamber may be defined by the volume of space arranged between the at least two electrodes or inside the resonant cavity. Particularly, the dielectric heating chamber may be defined as the volume between the at least two electrodes in which an alternating electrical field of sufficient strength for pre-heating and / or heating and / or vaporization of the aerosol-forming substrate is achieved. The sensing device may be arranged and / or positioned outside the heating chamber or receiving space. That the sensing device is arranged outside of the load capacitor or receiving space, more importantly outside the alternating electric field that is generated by the load capacitor, may mean that the sensing device may be arranged and / or positioned outside the heating chamber, for example the heating chamber of a HnB aerosol-forming substrate or receiving space for a cartridge. No part of the sensing device may therefore be arranged and / or positioned between the at least two electrodes and / or in the heating chamber or receiving space. In other words, the heating chamber and / or the volume of space between the at least two electrodes may be free of the sensing device, particularly any part of the sensing device. Outside of the heating chamber or the cartridge receiving space, the electric field strength of the load capacitor may diminish very quickly with increasing distance from the heating chamber, in particular due to the required electromagnetic shielding. The sensing device may therefore be arranged and / or positioned outside an area and / or space where the alternating electric field can be measured, i.e. be measured directly. By positioning the sensing device outside of the heating chamber or away from the receiving space, the full volume of the heating chamber is available for the aerosol-forming article, which improves energy efficiency of heating.

[0021] As mentioned, the sensing device is configured to detect a parameter indicative of the frequency of the alternating electric field, i.e. how often the direction of the electric field changes per unit of time, for example per second. Additionally, the sensing device may be arranged at a position where the electric field is too weak to be measured directly, or at a position that is not reached by the electric field due to shielding. The parameter indicative of the frequency of the alternating electric field may therefore not be the direction of the electric field and / or the strength of the electric field itself. In other words, the sensing device may not directly measure the electric field, not the field strength and not the direction. The sensing device may be or may comprise anyother type of sensor allowing determination of the frequency of the alternating electric field from some other parameter. For example, the sensing device may be configured to detect a parameter indirectly indicative of the frequency of the alternating electric field, particularly wherein the sensing device does not directly measure or detect changes to the alternating electric field. Using such an indirect detection of the frequency of the alternating electric field may allow more freedom in positioning the sensing device, as the sensing device does not have to be put into an area and / or space where the strength of the electric field is high enough to be reliably directly measured, i.e. into the heating chamber.

[0022] The aerosol-forming device may further comprise control circuitry including at least one controller and / or processor, wherein the control circuitry is configured to determine the frequency of the alternating electric field. The control circuitry may be connected to the sensing device and may receive the detected values of the parameter indicative of the frequency of the alternating electric field from the sensing device. The control circuitry may be configured to determine the frequency of the alternating electric field from the parameter detected by the sensing device, for example from the detected values of the parameter detected by the sensing device.

[0023] The aerosol-forming device may comprise an oscillator circuit electrically connectable or electrically connected to the at least two electrical contacts, i.e. connection terminals, to provide the alternating electrical field in the dielectric heating chamber, for example an electric field alternating directions with a radio frequency. In other words, the oscillator circuit may be configured to establish or drive the dielectric heating between the electrodes. The oscillation circuit may be a self-oscillating resonator circuit or a self-exciting resonator circuit or a self-sustaining resonator circuit having a resonant feedback loop, the resonant feedback loop including the load capacitor and at least one inductor. This may mean that the resonator circuit is not driven, particularly not externally driven. In the present disclosure, this may also be referred to as the oscillation circuit or resonator circuit being configured to oscillate freely, as no driving frequency is imposed on the circuit. The feedback loop may be used to provide the oscillating current and / or voltage which in turn provides the alternating electrical field in the heating chamber. The feedback loop may include at least one inductor, such as a coil, a choke, or a reactor. The frequency of the alternating field provided by such an oscillation circuit may be automatically provided by the self-oscillation or self-excitation or self-sustaining operation in the feedback loop. The frequency may, for example, depend on parameters of the circuit, for example the inductance of inductors included in the circuit as well as the capacitance, both of the circuit itself as well as the load capacitor. The capacitance of the load capacitor, in turn, may depend on the temperature of the load capacitor as well as on the nature and / or the temperature of the material between the electrodes constituting the load capacitor, i.e. of the material in the heating chamber. As these factors influence the frequency at which the self-oscillating resonator circuit oscillates, thefrequency may be used to infer information about the influencing factors. For example, for many materials, the capacitance of the load capacitor may increase with rising temperatures. However, there are also materials for which the capacitance of the load capacitor may decrease with rising temperatures. As the materials used are known, the proper relationship may be used for determination. The temperature of the load capacitor may be regarded as the same temperature as the aerosol-forming article in the heating chamber, as the load capacitor may be in close contact with the aerosol-forming article in the heating chamber, for example such that the load capacitor is heated up by the aerosol-forming article by heat conduction. Therefore, determining the temperature of the load capacitor, for example from the detected parameter and / or the frequency of the electric field, may at the same time determine the temperature of the aerosolforming article in the heating chamber.

[0024] Therefore, for example, from the frequency of the alternating electric field, the control circuitry may determine other useful information and / or parameters pertaining to the status of the aerosol-forming article in the heating chamber. Of course, as the frequency may be determined from the parameter measured by the sensing device, this information may also be determined directly from the parameter itself. For instance, the control circuitry may be configured to determine a temperature of the aerosol-forming article in the load capacitor and / or a grade of depletion of the aerosol-forming article from the detected parameter and / or the frequency of the alternating electric field. For example, when the aerosol-forming article is depleted, no more or only very limited quantities of liquid aerosol-forming substrate may be available in the heating chamber, which may result in a change of the capacitance of the load capacitor, which in turn may change the frequency of the oscillation. In general, the frequency of the oscillation circuit may increase with a decrease of aerosol-forming substrate in the load capacitor. Therefore, the frequency of the oscillation circuit may increase with an increasing grade of depletion of the aerosol-forming article. This may be due to the fact that the aerosol-forming substrate, for example a liquid substrate, may have a higher relative permittivity than the carrier material of the aerosol-forming article used to transport the liquid into and / or through the heating chamber. Therefore, the fraction of the volume of the heating chamber filled with aerosol-forming substrate may decrease, decreasing the capacitance of the load capacitor and increasing the frequency of the alternating electric field.

[0025] As used herein, the term “relative permittivity” may also be referred to as the real part of the complex, frequency-dependent relative permittivity, measured at a temperature of 20 degrees Celsius, in an alternating electric field at a very low frequency (VLF) of 1 Kilohertz or less, as defined in the international standard I EC 62631-2-1:2018. It will be appreciated that the frequency value of 1 Kilohertz is included here solely as a general reference and other definitions may use different frequencies.For example, a wicking element or liquid transfer element comprising a porous material or a material comprising capillaries may be used fortransporting the liquid aerosol-forming substrate into and / or through the heating chamber by capillary action. The material used for the wicking element may, for example, be a ceramic material having a lower relative permittivity than the liquid aerosol-forming substrate. Therefore, when the depletion level of the aerosol-forming article increases, the relative permittivity of the material inside the heating chamber decreases, which in turn leads to a decrease of the capacitance of the load capacitor, influencing the frequency of the oscillation, i.e. leading to an increase of the frequency. A variation of the frequency upon consumption from full substrate to a maximum depletion level may be in between 3% to 25%, for example between 5% to 20% or between 7% to 15%. The relationship between the oscillation frequency of the oscillation circuit and the temperature of the aerosol-forming article in the heating chamber and / or the depletion level of the aerosol-forming article may be experimentally predetermined. For example, the relationship may be recorded in a look-up table and / or reference charts and / or a mathematical function. These may be stored in a data storage or memory of the aerosol-forming device for use as explained herein.

[0026] The information gathered about the status of the aerosol-forming article, for example its temperature in the heating chamber and / or grade of depletion, may then be used to control and / or adjust control of the aerosol-forming device. For example, the control circuitry may be configured to control a power supplied to the oscillation circuit dependent on the detected parameter and / or the frequency of the alternating electric field. Of course, this may also be done indirectly, for example by the control circuitry being configured to control a power supplied to the oscillation circuit dependent on the determined temperature of the aerosol-forming article in the heating chamber and / or the grade of depletion of the aerosol-forming article. As an example, the control circuitry may adjust the power supplied to the oscillation circuit so that the temperature of the aerosol-forming article in the heating chamber follows or corresponds to a heating profile, for example a heating profile specifically optimized for the type of aerosol-forming article used in the aerosol-forming device in that particular usage session. In this way, for example, the control circuitry may reduce the power supplied to the oscillation circuit when the temperature of the aerosol-forming article in the heating chamber lies above a target temperature of the heating profile and / or the control circuitry may increase the power supplied to the oscillation circuit when the temperature of the aerosol-forming article in the heating chamber lies below a target temperature of the heating profile and / or the control circuitry may keep the power supplied to the oscillation circuit constant when the temperature of the aerosol-forming article in the heating chamber matches a target temperature of the heating profile. As another example, the control circuitry may adjust the power supplied to the oscillation circuit so that overheating of an almost depleted or depleted aerosol-forming article or the substrate in the aerosol-forming article may beavoided. For example, the control circuitry may reduce, for example gradually reduce, the power supplied to the oscillation circuit with an increasing depletion of the aerosol-forming article. The control circuitry may be configured to stop power supply to the oscillation circuit when the depletion of the aerosol-forming article reaches a predetermined threshold. The predetermined threshold may be chosen so that the depletion grade of the aerosol-forming article counts as fully depleted. For example, the depletion threshold may be more than 90% depletion, for example more than 95% depletion, of the aerosol-forming article. When the predetermined threshold is reached, the control circuit may be configured to notify the user of the aerosol-forming device, for example by displaying or otherwise outputting a notification. The control circuit may also be configured to notify the user of the grade of the depletion of the aerosol-forming article, even before the predetermined threshold is reached.

[0027] As mentioned, the oscillation circuit may be configured to provide an oscillating current and / or voltage in the range of radio frequency. More particularly, the oscillation circuit may be configured to provide an oscillating current and / or voltage of at least 100 MHz, for example at least 200 MHz or at least 300 MHz, but below 1.5 Ghz, for example below 1.2 GHz. For example, the oscillation circuit may be configured to provide an oscillating current and / or voltage of from 100 MHz to 800 MHz. An alternating electric field with these frequencies may be efficiently provided by the oscillation circuits as used in the present invention, which will be described in more detail below. For resonant cavity and / or transmission line type dielectric heating arrangements, oscillation frequencies may be higher, e.g. in a range between 1GHz to 24Ghz, more preferably between 1GHz and 5GHz, even more preferably about 2.45GHz.

[0028] In an aerosol-forming device, the aerosol-forming article may need to be heated to high temperatures, for example between 180 °C to 400 °C, in very short times, for example during the puff of the user. To provide for sufficient heating power the voltage across the at least two electrodes of the load capacitor may need to be sufficiently high. For example, the oscillation circuit may be configured to provide an oscillating AC voltage across the at least two electrodes of the load capacitor having a peak value of at least 50 V, for example at least 75 V or at least 100 V or at least 125 V or at least 150 V or at least 175 V or at least 200 V. The respective voltages may be achieved by boosting, multiplying and / or amplifying the nominal voltage of the power supply or energy storage of the aerosol-forming device, for example the battery.

[0029] As mentioned, the increased efficiency of the invention may at least partly rely on the fact that the sensing device may not directly measure the direction and / or strength of the electric field in the load capacitor. Therefore, the sensing device may be arranged and / or positioned remote from the load capacitor and may therefore not obstruct the interior space or volume of the heating chamber. The sensing device may be configured to detect the action and / or electrical parameters and / or working frequency of components of the oscillation circuit other than the load capacitor. Ina possible embodiment, the oscillation circuit may include at least one inductor, for example at least one inductor coil, wherein the sensing device is configured to detect the frequency of a magnetic field of the at least one inductor. As the inductor, along with the load capacitor, may drive and / or establish the oscillation of the oscillation circuit, the frequency of the magnetic field of the at least one inductor may equal the frequency of the alternating electric field in the load capacitor. Therefore, by measuring the frequency of the magnetic field of the at least one inductor, the frequency of the alternating electric field in the load capacitor may be determined.

[0030] To achieve this, the sensing device may include a measurement coil. The measurement coil may be configured to measure the magnetic field of the at least one inductor of the oscillation circuit. The at least one inductor of the oscillation circuit may comprise at least one or exactly one turn or coil winding. The measurement coil may include at least one or exactly one turn or coil winding. The measurement coil may be at least partly arranged inside the inductor coil, where the magnetic field of the inductor coil is strongest. Changes in the magnetic field of the inductor coil may therefore induce a voltage and / or current in the measurement coil, which may be detected as the signal of the measurement coil and therefore as the signal of the sensing device. This voltage and / or current at the measurement coil may, for example, be measured between the two terminals of the measurement coil.

[0031] For the changes of the direction of the magnetic field of the at least one inductor to have the most effect on the measurement coil and therefore to be reliably detected, it may be provided that the measurement coil is arranged and / or positioned in the center of the inductor coil. For example, the measurement coil may be arranged such that a measurement coil axis of the measurement coil coincides with a coil axis of the inductor coil. The measurement coil and the inductor coil may therefore be coaxially arranged. The coil windings of the measurement coil and the inductor coil may at least partly overlap in the radial direction of the measurement coil axis and / or the coil axis of the inductor coil. In this case, the signals detectable at the measurement coil and representative of the changes of the magnetic field in the inductor coil may be the greatest. However, small deviations may be possible without influencing the measurement too much. For example, the measurement coil may be arranged such that a measurement coil axis of the measurement coil and a coil axis of the inductor coil are arranged at an angle of up to 30° or up to 20° or up to 15° or up to 10° or upto 5°. In these ranges, the measurement of the magnetic field and / or the changes to the magnetic field of the inductor coil may still be reliable. Simultaneously, the measurement coil may be more freely placed and / or positioned in the aerosol-generating device, both in terms of saving space and in terms of tolerances.

[0032] In another possible embodiment of the sensing device, the sensing device may be configured to measure a voltage and / or a current in the feedback loop of the oscillation circuit. The voltage and / or the current in the feedback loop may switch directions in the same frequencyas the alternating electric field of the load capacitor. Therefore, by measuring the frequency of the changes, for example directional changes, of the voltage and / or the current in the feedback loop of the oscillation circuit, the frequency of the alternating electric field in the load capacitor may be determined. In an example embodiment, the oscillation circuit may include at least one transistor, wherein the sensing device may be connected to a gate of the transistor and may be configured to detect a voltage applied at the gate. The voltage at the gate of the transistor may change with the same frequency as the alternating electric field. Therefore, measuring the voltage of the gate of the transistor also constitutes the determination of the frequency of the alternating electric field.

[0033] As mentioned, the frequency of the alternating electric field may be measured by measuring voltages over different parts of the oscillation circuit. The sensing device may therefore comprise a voltage sensor configured to measure and / or determine a voltage and / or a change of a voltage at a sensor input. To make sure that the voltages to be measured fit or match the input voltages of the voltage sensor, the sensing device may include a voltage divider configured to reduce the input voltage of the sensing device, for example for adjusting the voltage to be measured to the input voltage of the voltage sensor. In an exemplary embodiment, the voltage divider may comprise two resistors connected in series, wherein the voltage sensor and / or the sensing device may detect and / or measure the voltage between the two resistors.

[0034] For reliable detection, the input signal into the sensing device also needs to be in a frequency range suitable for the sensing device. As the frequencies of the alternating electric field as used herein may be high, the frequencies may need to be reduced for detection by the sensing device. The sensing device may therefore include a prescaler or frequency divider, wherein the prescaler or frequency divider may be configured to divide the frequency of an input signal of the sensing device by a factor, for example a factor of between 10 and 250 or of between 20 and 150. In an alternative embodiment, the sensing device may include a phase locked loop, PLL, wherein the PLL is configured to reduce the frequency of an input signal of the sensing device by a factor, for example a factor of between 10 and 250 or of between 20 and 150. In this way, the comparatively high frequencies of the alternating electric field may be reliably measured by the sensing device.

[0035] To further improve the accuracy of the measurement, signal noise may be reduced and / or the signal to noise ratio may be increased. For example, the sensing device may include a band pass filter, for example a capacitor or capacitor-based band pass filter, wherein the band pass filter is configured to filter an input signal of the sensing device. The band pass filter may be configured to filter out and / or attenuate frequencies outside of the frequency range expected from the oscillation circuit. For example, frequencies that are higher or lower than the expected frequency range of the oscillation circuit may be filtered out and / or attenuated.According to another aspect of the present invention, there is provided an aerosol-forming system, including an aerosol-forming device according to the present disclosure, and further including an aerosol-forming article, for example wherein the aerosol-forming device is configured to generate or form aerosol from the aerosol-forming article by dielectric heating. All of the features, effects and advantages of the aerosol-forming device according to the present disclosure are also applicable to the aerosol-forming system and vice versa.

[0036] According to another aspect of the present invention, there is provided a method of monitoring dielectric heating of an aerosol-forming article in a portable and hand-held aerosolforming device for forming aerosol for human inhalation, for example an aerosol-forming device according to the present disclosure, or in an aerosol-forming system, for example an aerosolforming system according to the present disclosure, including: generating of an alternating electric field for performing dielectric heating; and detecting a parameter indicative of a frequency of the alternating electric field by a sensing device arranged outside of the generated alternating electric field. All of the features, effects and advantages of the aerosol-forming device and / or the aerosolforming system according to the present disclosure are also applicable to the method and vice versa.

[0037] According to another aspect of the present invention, there is provided a method of monitoring dielectric heating of an aerosol-forming article in an aerosol-forming device, for example an aerosol-forming device according to the present disclosure, or in an aerosol-forming system, for example an aerosol-forming system according to the present disclosure, including: providing an oscillating current and / or voltage to at least two electrical contacts couplable or coupled to at least two electrodes of a load capacitor so that an alternating electric field across the at least two electrodes is established for performing dielectric heating; and detecting a parameter indicative of a frequency of the alternating electric field by a sensing device arranged outside of the load capacitor. All of the features, effects and advantages of the aerosol-forming device and / or the aerosol-forming system and / or the previously mentioned method according to the present disclosure are also applicable to this method and vice versa.

[0038] The invention is defined in the claims. However, below there is provided a non-exhaustive list of non-limiting examples. Any one or more of the features of these examples may be combined with any one or more features of another example, embodiment, or aspect described herein.

[0039] Example 1. A portable and hand-held aerosol-forming device for forming aerosol for human inhalation from an aerosol-forming article by dielectric heating, comprising:

[0040] a dielectric heating arrangement including an oscillation circuit, for example wherein the oscillation circuit is configured to oscillate freely, the arrangement generating of an alternating electric field for performing the dielectric heating,a heating chamber or receiving space configured to removably receive the aerosol-forming article, and

[0041] a sensing device arranged outside of the generated alternating electric field, wherein the sensing device is configured to detect a parameter indicative of a frequency of the alternating electric field.

[0042] Example 2. The aerosol-forming device according to Example 1, comprising wherein the oscillation circuit is configured to provide an oscillating current and / or voltage to at least two electrical contacts couplable or coupled to at least two electrodes of a load capacitor so that an alternating electric field between the at least two electrodes is established for performing dielectric heating,

[0043] wherein the sensing device is arranged outside of the load capacitor.

[0044] Example 3. The aerosol-forming device according to any one of the previous Examples,

[0045] wherein the dielectric heating arrangement comprises a resonant cavity and / or a transmission line and is configured to provide an alternating electric field for performing the dielectric heating in the resonant cavity and / or the transmission line,

[0046] wherein the sensing device is arranged outside of the resonant cavity and / or the transmission line.

[0047] Example 4. The aerosol-forming device according to any one of the previous Examples,

[0048] wherein the sensing device is arranged and / or positioned outside the heating chamber or receiving space.

[0049] Example 5. The aerosol-forming device according to any one of the previous Examples,

[0050] wherein the sensing device is configured to detect a parameter indirectly indicative of the frequency of the alternating electric field, particularly wherein the sensing device does not directly measure or detect changes to the alternating electric field.

[0051] Example 6. The aerosol-forming device according to any one of the previous Examples,

[0052] wherein the oscillation circuit is a self-oscillating resonator circuit having a resonant feedback loop, the resonant feedback loop including the load capacitor and at least one inductor.

[0053] Example 7. The aerosol-forming device according to any one of the previous Examples,

[0054] further including control circuitry including at least one controller and / or processor, wherein the control circuitry is configured to determine the frequency of the alternating electric field.

[0055] Example 8. The aerosol-forming device according to the previous Example,wherein the control circuitry is configured to determine a temperature of the aerosol-forming article in the load capacitor and / or a grade of depletion of the aerosol-forming article from the detected parameter and / or the frequency of the alternating electric field.

[0056] Example 9. The aerosol-forming device according to any one of Examples 7-8, wherein the control circuitry is configured to control a power supplied to the oscillation circuit dependent on the detected parameter and / or the frequency of the alternating electric field.

[0057] Example 10. The aerosol-forming device according to any one of the previous Examples,

[0058] wherein the oscillation circuit is configured to provide an oscillating current and / or voltage of at least 100 MHz, for example at least 200 MHz or at least 300 MHz, but below 1.5 Ghz, for example below 1.2 GHz.

[0059] Example 11. The aerosol-forming device according to any one of the previous Examples,

[0060] wherein the oscillation circuit is configured to provide an oscillating AC voltage across the at least two electrodes of the load capacitor having a peak value of at least 50 V, for example at least 75 V or at least 100 V or at least 125 V or at least 150 V or at least 175 V or at least 200 V.

[0061] Example 12. The aerosol-forming device according to any one of the previous Examples,

[0062] wherein the oscillation circuit includes at least one inductor, for example at least one inductor coil, wherein the sensing device is configured to detect the frequency of a magnetic field of the at least one inductor.

[0063] Example 13. The aerosol-forming device according to the previous Example, wherein the sensing device includes a measurement coil, wherein the measurement coil includes at least one turn, and wherein the measurement coil is at least partly arranged inside the inductor coil.

[0064] Example 14. The aerosol-forming device according to the previous Example, wherein the measurement coil is arranged such that a measurement coil axis of the measurement coil coincides with a coil axis of the inductor coil or

[0065] wherein the measurement coil is arranged such that a measurement coil axis of the measurement coil and a coil axis of the inductor coil are arranged at an angle of up to 30° or up to 20° or up to 15° or up to 10° or up to 5°.

[0066] Example 15. The aerosol-forming device according to any one of the previous Examples,

[0067] wherein the oscillation circuit includes at least one transistor, wherein the sensing device is connected to a gate of the transistor and is configured to detect a voltage applied at the gate.

[0068] Example 16. The aerosol-forming device according to the previous Example,wherein the sensing device includes a voltage divider configured to reduce the input voltage of the sensing device.

[0069] Example 17. The aerosol-forming device according to any one of the previous Examples,

[0070] wherein the sensing device includes a prescaler or frequency divider, wherein the prescaler or frequency divider is configured to divide the frequency of an input signal of the sensing device by a factor, for example a factor of between 10 and 250 or of between 20 and 150.

[0071] Example 18. The aerosol-forming device according to any one of the previous Examples,

[0072] wherein the sensing device includes a phase locked loop, PLL, wherein the PLL is configured to reduce the frequency of an input signal of the sensing device by a factor, for example a factor of between 10 and 250 or of between 20 and 150.

[0073] Example 19. The aerosol-forming device according to any one of the previous Examples,

[0074] wherein the sensing device includes a band pass filter, for example a capacitor or capacitorbased band pass filter, wherein the band pass filter is configured to filter an input signal of the sensing device.

[0075] Example 20. An aerosol-forming system including an aerosol-forming device according to any one of the previous Examples, and

[0076] further including an aerosol-forming article, for example wherein the aerosol-forming device is configured to generate or form aerosol from the aerosol-forming article by dielectric heating.

[0077] Example 21. A method of monitoring dielectric heating of an aerosol-forming article in a portable and hand-held aerosol-forming device for forming aerosol for human inhalation, for example an aerosol-forming device according to any one of the previous Examples 1-19, or in an aerosol-forming system, for example an aerosol-forming system according to the previous Example, including:

[0078] generating of an alternating electric field for performing dielectric heating; and detecting a parameter indicative of a frequency of the alternating electric field by a sensing device arranged outside of the generated alternating electric field.

[0079] Examples will now be further described with reference to the figures in which:

[0080] Figure 1 shows an aerosol-forming system;

[0081] Figure 2 shows a schematic illustration of an oscillation circuit for use in an aerosolgenerating system;

[0082] Figure 3a shows a schematic illustration of an oscillation circuit;

[0083] Figure 3b shows a schematic illustration of another oscillation circuit;

[0084] Figure 4 shows an oscillation circuit diagram;Figure 5 shows an isometric illustration of an inductor pair sharing a mutual inductive coupling for use in the oscillation circuit;

[0085] Figure 6 shows an a possible implementation of a sensing device comprising a measurement coil;

[0086] Figure 7 shows the positioning of the measurement coil inside an inductor coil of the oscillation circuit;

[0087] Figure 8 shows another possible implementation of a sensing device comprising a voltage sensor;

[0088] Figure 9 shows a circuit diagram for a possible implementation of a sensing device; and Figure 10 shows a flowchart of the method.

[0089] The figures are schematic only and not to scale.

[0090] Figure 1 shows an aerosol-forming or aerosol-generating system 1 for forming or generating aerosol, for example for consumption or inhalation by a user in one or more usage sessions. The system 1 may comprise at least one of an aerosol-forming device 2 for generating aerosol and a companion device 3 for at least partially receiving the aerosol-forming device 2. The companion device 3 may be a charging device for charging the aerosol-forming device 2 and / or an energy storage 15 or battery thereof.

[0091] The aerosol-forming device 2 may comprise an insertion opening for at least partially inserting an aerosol-forming article 18, such as a tobacco stick or an e-vapor cartridge or pod. The aerosol-forming article 18 may comprise an aerosol-forming substrate, such as a tobacco containing substrate, for example a liquid, for example a liquid that can be aerosolized for inhalation. The aerosol-forming article 18 may at least partly protrude from the aerosol-forming device 2 when it is inserted into the aerosol-forming device, for example into a receptacle chamber 21 of the aerosol-forming device 2. For example, the aerosol-forming article 18 may comprise a mouthpiece 4, through which a user may inhale aerosol provided by the aerosol-forming device 2 for consumption during a usage session and / or an inhalation or puff. The mouthpiece 4 may be a part of the aerosol-forming article 18 protruding from the aerosol-forming device 2. Another part of the aerosol-forming article 18 may be arranged inside the aerosol-forming device 2, particularly inside the receptacle chamber 21 , and is therefore not visible in Figure 1. Therefore, the aerosolforming article 18 may be removably couplable to the aerosol-forming device 2. Alternatively, the aerosol-forming article 18 may be a fixedly coupled component of the aerosol-forming device 2, and may for example comprise a refillable reservoir for liquid aerosol-forming substrate.

[0092] The aerosol-forming device 2 may further include processing circuitry or control circuitry with at least one controller 5 and one or more processors 6. For generating the aerosol during use or consumption of the aerosol-forming article 18, the aerosol-forming device 2 may comprise at least one heating element 7 or heater device for applying heat to at least a portion of theaerosol-forming article. For example, the heating element 7 may be or may comprise a dielectric heating arrangement. Instead of the heating element?, an ultrasonic device (not shown) may also be used to generate aerosol from the aerosol-forming article. The processing circuitry and / or the controller 5 and / or the processor 6 may be configured to control actuation, activation and / or deactivation of at least one heating element 7 or ultrasonic device. Particularly, the heating element 7 may comprise an oscillation circuit or at least parts of an oscillation circuit used for dielectric heating, for example in conjunction with electrodes forming a load capacitor. The heating element 7 may not itself be heated, but be used to heat parts of the aerosol-forming article 18, which may in turn lead to heating of the load capacitor through heat conduction from the aerosolforming article 18. The load capacitor, i.e. the electrodes, may be arranged in and / or part of the aerosol-forming article 18 or the aerosol-forming device 2. The aerosol-forming device 2 may comprise electrical contacts 160, 165, which may be used to connect any part, if any, of the oscillation circuit arranged in the aerosol-forming article 18 with the part of the oscillation circuit arranged in the aerosol-forming device 2.

[0093] The aerosol-forming device 2 may comprise a sensing device 19 configured to detect a parameter indicative of a frequency of the alternating electric field. The sensing device 19 may therefore indirectly be used to detect the frequency of the alternating electric field of the oscillation circuit, as will be described in more detail below.

[0094] For powering the at least one heating element 7 or dielectric heating arrangement with electrical power, the aerosol-forming device 2 may further comprise the at least one energy storage 15, for example in the form of a battery, for storing electrical energy or power. In Figure 1, both the aerosol-forming device 2 and the companion device 3 each comprise an energy storage 15 and the energy storage 15 is electrically coupled to the respective device 2, 3. In particular, energy storage 15 may be removably couplable to the aerosol-forming device 2 and / or the companion device 3. In other words, energy storage 15 may be a replaceable energy storage or battery. The connection between the energy storage 15 and the devices 2, 3 may be configured so that the devices 2, 3 may be run by electrical energy provided by the energy storage 15. Additionally, the connection between the energy storage 15 and the aerosol-forming device 2 and / or the companion device 3 may be configured so that data may be transmitted between the processing circuitries of the aerosol-forming device 2 and / or the companion device 3 and the energy storage 15.

[0095] The aerosol-forming device 2 may further comprise at least one electrical connector 12 for coupling to a corresponding at least one electrical connector 13 of the companion device 3 and / or an electrical connector of an external power supply (not shown), e.g., a USB charger. For example, when the aerosol-forming device 2 is at least partially inserted into the opening 14 of the companion device 3, the one or more electrical connectors 12 of the aerosol-forming device2 may be coupled with the one or more electrical connectors 13 of the companion device 3 to charge the at least one energy storage 15 of the aerosol-forming device 2.

[0096] The aerosol-forming device 2 may further comprise a communications arrangement 9 or communication circuitry 9 with one or more communications interfaces 10 for communicatively coupling the aerosol-forming device 2 with the companion device 3 or other devices, for example, via an Internet connection, a wireless LAN connection, a WiFi connection, a Bluetooth connection, a mobile phone network, a mobile data connection for example but not limited to a 3G / 4G / 5G connection, an edge connection, an LTE connection, a BUS connection, a wireless connection, a wired connection, an optical data connection such as but not limited to IrDa, a radio connection, a near field connection, and / or an loT connection.

[0097] The aerosol-forming device 2 may further comprise a data storage 11 or memory for storing information, program code or data. Data storage 11 may also store collected values of sensors and / or one or more mathematical functions or formulas, software and computer instructions that can be executed by the processing circuitry, particularly controller 5 and / or processor 6. One or more sensors 16 may be arranged on, at or in the aerosol-forming device 2 or the companion device 3 to collect data. One or more of the sensors 16 may for example be temperature sensors, strain sensors, accelerometers or any other suitable sensors.

[0098] The aerosol-forming device 2 may further comprise user interface components, for example comprising an input element or input device 8, for example in the form of a pushbutton or a capacitive button. The input device 8 may be used as a power button to activate or deactivate the heating element 7 or ultrasonic device for aerosol generation thereby to activate or deactivate the aerosol-forming device 2. Upon activation of the aerosol-forming device 2, the heating element 7 may be activated and heat may be applied to at least a part of the aerosol-forming article 18, such that aerosol can be generated for consumption or inhalation by the user, for example in a usage session. The aerosol-forming device 2 and / or the companion device 3 may each comprise one or more output elements, such as a display device 17 and / or one or more LEDs, for outputting a signal and / or displaying information to a user, for example a user interface such as a GUI, or haptic and acoustic data output devices. The display device 17 may be, for example, a touchscreen and may therefore be configured as both an output and an input element.

[0099] Figure 2 is a schematic illustration of an exemplary oscillation circuit 250 that can be used as or for the dielectric heating arrangement 7 for aerosol-forming system 1 or aerosol-forming device 2. Oscillation circuit 250 may comprise a switching unit 260 interconnected with a resonator feedback loop 270 to provide for a self-oscillating signal to the switching unit 260. The switching unit 260 may comprise a single transistor, such as a bipolar junction transistor (BJT) or a field effect transistor (FET). The oscillation circuit described herein is exemplary only, and other types of oscillation circuits can be used, for example other types of resonant oscillator circuitswhere the load capacitor for causing the dielectric heating is part of the resonant feedback loop, or signal oscillators that are connected to an amplifier and an impedance matching circuit to apply an RF voltage to the electrodes for causing the alternating electric field for dielectric heating. The given embodiments of the oscillation circuits 250 and 355 (Figure 4) are therefore merely exemplary and not intended to limit the invention.

[0100] The oscillation circuit 250 may further comprise a choke 280 that acts on an input to the feedback loop 270 to provide for a stimulation signal, for example a stimulation voltage. The oscillation circuit may also comprise a biasing unit 290 acting on the feedback loop 270 for providing a variable or controllable biasing signal, for example a biasing voltage for setting the operating conditions. In the variant shown, the feedback signal can be described as a voltage. The output voltage UOUT of the switching unit 260 may be coupled to the feedback loop 270 providing a feedback switching signal in the form of a voltage U|Nto the switching unit 260. The configuration of the feedback loop 270 may be such that the output signal, e.g. the voltage UOUT of the switching unit 260, can undergo a phase change and arrives inverted at the input U|Nof the switching unit 260 for resonant oscillation. In other configurations, a current could be used as the feedback signal with a switching unit 260 comprising a BJT.

[0101] The feedback loop 270 may be configured to be self-oscillating and may oscillate at or close to a given resonance frequency determined by the values of the passive components of the feedback loop 270. Feedback loop 270 may be configured to provide a 180° phase shift from the output UOUT to input UIN of switching unit 260 for oscillation, and, in addition, a transistor T (Figure 4) may be configured for inverting operation.

[0102] As shown in Figures 3a and 3b, feedback loop 270 may include a resonant circuit 272 comprising a load capacitor CLproviding for a first 90 degrees phase shift or quarter wave shift to the feedback signal. The heating zone according to the present disclosure may be arranged or may be provided inside the load capacitor CL. Feedback loop 270 may further include a capacitive element 274 providing for a second 90 degrees phase shift or quarter wave shift to the feedback signal, such that the feedback signal reaching the input of the switching unit 260 may be inverted and phase-shifted by 180 degrees. Switching unit 260 may itself be configured for inverted switching operation to provide a 180 degree phase shift between the input U|Nand the output UOUT of the switching unit 260.

[0103] Resonant circuit 272 may comprise first and second electrodes 130, 135 (which may both be referred to as electrodes 26), together forming a load capacitor CL(see Figure 4). When an aerosol-forming substrate, in the present case the liquid aerosol-forming substrate 20 that is brought into the heating zone by a liquid transfer element, is situated between the first and second electrodes 130, 135, it may form part of the load capacitor CL. In this non-limiting example of the oscillator, the load capacitor CLmay be formed in the feedback loop 270, and not at a separateoutput or part of a separate circuitry that is connected to the switching unit 260. This may enable a high-frequency oscillating voltage to be created across the electrodes 130, 135 of load capacitor CL, which is needed for sufficient and efficient dielectric heating of the aerosol-forming substrate 20, without having an additional output or circuit to the already resonating feedback loop 270. This may avoid unnecessary losses and circuit complexity. The resonant circuit 272 may comprise a series resonator circuit or a parallel resonator circuit.

[0104] Figure 4 illustrates an oscillation circuit 355 according to a non-limiting, exemplary embodiment of the present disclosure. Oscillation circuit 355 may comprise a switching unit 260 in the form of a transistor T having an intrinsic capacitance Ci. Moreover, transistor T may be configured for inverting operation, for example as an inverting common source FET, MOSFET, more specifically a LDMOS, or a common emitter BJT. The source terminal of transistor T may be coupled to a DC power supply via a choke 280. Between the gate and source terminals of transistor T a feedback loop 270 may extend. The feedback loop 270 may comprise a resonant circuit 272 including a load capacitor CLhaving a first and second electrode 130, 135 separated by an aerosol-forming substrate 20 supplied from the aerosol-forming article 18. In the variant shown, the resonant circuit 272 may also be connected to ground via a delay line DL and a capacitor C2connected in series to the delay line DL. The circuit 355 may further comprise a biasing unit 290 coupled to the gate terminal of the transistor T via the delay line DL. As shown in Figure 4, the biasing unit 290 may be electrically connected between the delay line DL and the capacitor C2, so that the biasing unit 290 may be somewhat isolated from the high oscillation frequency of the feedback loop 270.

[0105] The delay line DL may be a time delay element, for example an element that has inductive behavior, for slowing down the arriving voltage wave from the feedback loop 270 during a period of the oscillation. This may allow to tune the resonant circuit 272 to a desired switching and oscillation frequency, to move the oscillation frequency away from the natural resonant frequency given by the resonant circuit 272. This may ensure that oscillation circuit 355 remains in a predefined frequency operating range to provide for the requisite inverted or 90° phase shifted feedback and also to make sure that the feedback loop has a low impedance to provide for a high gain.

[0106] The oscillation circuit 355 is shown with electrical contacts 160, 165 that may be arranged on each side of the load capacitor CL. The first and second electrodes 130, 135 are part of the removable aerosol-forming article 18 and are therefore removable from the rest of the oscillation circuit 355. Electrical contacts 160, 165 provide a removable electrical connection between the first and second electrode 130, 135 and the feedback loop 270. As exemplarily shown in the Figure, electrical contacts 160, 165 may be arranged at different positions in the oscillator circuit 355, resulting in different components being arranged on the aerosol-forming article 18 side orthe aerosol-forming device 2 side. For example, electrical contacts 160, 165 may be arranged between the load capacitor CL, i.e. the electrodes 26, 130, 135, and the inductors LT and L2. In this case, only the electrodes 26, 130, 135 may be arranged on and removable with the aerosolforming article 18. As another example, the electrical contacts 160, 165 may be arranged between the inductors and L2and the load capacitor CL, i.e. the electrodes 26, 130, 135, on the one hand, and the rest of the oscillation circuit 355 on the other. In this case, the electrodes 26, 130, 135 and the inductors LT and L2may be arranged on and removable with the aerosol-forming article 18. In embodiments where the load capacitor CLis fixed within the feedback loop 270, e.g. a non-removable cartridge as the aerosol-forming article 18, for example, electrical contacts 160, 165 provide electrical connections from the first and second electrodes to the next components in the feedback loop 270, e.g. inductors LT and L2or other components. Although two inductors LT and L2are shown, the oscillation circuit 355 may also only comprise one single inductor.

[0107] With respect to the power supply voltage, a DC power supply voltage may be provided, that is preferably in a range that is suitable for battery operation with one or more standard battery cells. Preferably, the DC power supply voltage is below 14V. For example, it is possible to operate the oscillation circuit 355 on a single battery cell, for example an 18650 battery cell (Li-Ion), or a similar battery cell, that provides for 3.2V to 3.9V. However, more preferably, a voltage of one battery cell of an exemplary 3.5V to 7V for power supply can be boosted, for example by a DC-DC converter (e.g. a boost circuit), or a voltage doubler. Alternatively or in addition, two or more battery cells can be used in series, or other configurations or arrangements that allow to increase a voltage from one or more battery cell can be used. It is also possible to have a controllable output voltage (e.g. DC-DC converter, voltage regulator), to control the temperature of heating by a change to the DC supply voltage, or to boost the voltage (for example to 10-12V) for maximum power at the preheating stage, to speed up the preheating stage with the goal to reach the aerosolization temperature quickly. Control of the DC supply voltage is one way that makes it possible to rapidly change heating power despite the oscillation circuit 355 freely oscillating.

[0108] A capacitor C-, may be arranged in parallel to the transistor T and therefore in parallel with the intrinsic capacitor of the transistor T (e.g. a field effect transistor). This may facilitate a less voltage-dependent oscillation and frequency, stabilize the oscillation, and also improve the overall dielectric heating efficiency. Capacitance of capacitor C-j may be chosen to be larger than the maximal intrinsic capacitor Ci of transistor T at the operating conditions, so that the variation of the intrinsic transistor based on frequency, temperature, etc. has much less or negligible influence on the feedback loop 270. For example, in a non-limiting embodiment, the value may be in a range between 2pF to 100pF, more preferably in a range between 5pF and 50pF.

[0109] Capacitive element 274 may comprise a capacitor C2arranged at the output or end of the resonant circuit 272. In one embodiment, capacitive element 274 may comprise more than onecapacitor. As described above, capacitive element 274 may have the function of providing a 90° phase shift to the feedback voltage of feedback loop 270 with minimized losses or other undesired effects, and it therefore needs to have a high-quality factor or Q factor, preferably above 1000 at 100MHz. The capacitance value for capacitor C2of the capacitive element 274 may be relatively high as compared to capacitor

[0110]

[0111] for example in a range between 500pF to 100nF, more preferably between 1 nF and 50nF, which may lead to a low impedance of capacitive element 274. In one embodiment, the capacitive element 274 may be implemented as an RC network to provide for the 90° phase shift, for example using two single-resistor-capacitor networks, having two capacitors in the feedback loop, each capacitor connected to ground via a resistor.

[0112] Resonant circuit 272, together with capacitive element 274, may provide for a 180° phase shift and a voltage gain from the output UOUT to the input U|N, and transistor T (for example a FET) may be configured for inverting operation, thereby also providing for another 180° phase shift. This may result in a resonant or close-to resonant oscillation and an amplified voltage across the electrodes 130 and 135 of the load capacitor CL, as compared to the DC supply voltage. When operating close to resonance, the resonant circuit 272 circuit may behave inductively, having a high Q factor. Furthermore, the feedback loop 270 may be impedance-matched with the transistor T, to provide for a high gain, leading to an increased voltage across the load capacitor CL.

[0113] The combination of capacitor Ci , the feedback loop with resonant circuit 272 and capacitive element 274 may also be described as a bandpass filter or Pi or TT network that generates a 180° phase shift. In the illustrated embodiment, the resonant circuit 272 of the feedback loop 270 may not be connected to ground, but may be suspended with ends at each capacitor C-, and C2, thereby not having a direct ground connection at either end of resonant circuit 272, reducing stray elements and ground influences for more predictable operation.

[0114] At the operating frequency, the resonant circuit 272 including load capacitor CLmay act as an inductive load providing a first 90° phase shift, also referred to as a quarter-wave phase shift, and capacitive element 274, which may exemplarily include a high quality factor capacitor C2 connected to ground, may provide for the second 90° phase shift or quarter-wave phase shift.

[0115] In some embodiments, oscillation circuit 355 may be based on other resonant feedback loop oscillation circuit configurations, for example, but not limited to, the use of a Colpitts or Hartley type oscillator, using an inverting transistor T.

[0116] Figure 5 is an isometric illustration of a split coil resonator having a mutual inductive coupling for use in the oscillation circuit according to embodiments of the present disclosure. In the example of Figure 5, the two inductors LT and L2, may each be formed as a single winding, e.g. a single loop coil. Other winding numbers and / or winding shapes are also possible while providing substantially the same functionality. In some examples, it is possible to use a smaller diameter of inductor coils L2, but have several loops or turns. For example the number of turns in eachinductor coil U, L2may be no more than five. The winding central axis of each coil may substantially coincide with each other, and the plane formed by each single-winding inductor may be parallel to the other, and may also be in close proximity. This may establish a mutual inductance between inductors LT and L2without a magnetic core Mc. If necessary, the mutual inductance may be further increased by adding a magnetic core Mcthat may traverse or may at least partially traverse each winding of LT and L2to reach a desired inductance level. In this respect, a distance between the two planes in which the windings are arranged may be increased, to minimize the capacitive effect between them. In an example, the windings of inductors LT and L2may be wound in the same direction around the coinciding winding central axis, or in case a core Mcis present, around the core Mcor the central axis. This way, the magnetic flux caused by both coils LT and L2may be enhanced, rather than cancelled out. In other words, the two inductors LT and L2may appear as a continuously wound coil around a magnetic core Mc, or around the winding central axis in case no core is used, with two winding regions forming two inductor coils LT, L2. Figure 5 shows an exemplary embodiment of the resonant circuit as a complete parallel resonant circuit, PRC, by virtue of the second branch being created by the mutual inductance between inductors and L2. It is also possible that the mutual inductance between and L2may be created by simple proximity of the two inductor coils

[0117]

[0118] and L2, without the use of a magnetic core Mc, or by inter-winding the coils of inductors U and L2. Figure 5 illustrates an electrode arrangement comprising a pair of electrode plates aligned in parallel, however other electrode arrangements are also possible.

[0119] Figure 6 illustrates how the electrodes 130, 135 may protrude into the receptacle chamber 21 of the aerosol-forming device 2. The receptacle chamber 21 may be configured to receive the aerosol-forming article 18, wherein the electrodes 130, 135 may be arranged to receive at least part of the aerosol-forming article 18 between them to form the heating chamber 20 as explained herein. As also shown in Figure 6, the electrodes 130, 135 may be connected to an oscillation circuit 250, 355 as explained above. Although the inductors

[0120]

[0121] L2may be part of oscillation circuit 250, 355, they are shown separately for clarity. Oscillation circuit 250, 355 may be connected to a DC / DC converter 29, which may be configured as a boost converter, for supplying electrical power to the oscillation circuit 250, 355, for example as controlled by controller 5.

[0122] Figure 6 also shows a particular arrangement of an exemplary embodiment of the sensing device 19. In the example shown in Figure 6, the sensing device 19 may comprise a measurement coil 22 which may comprise one or more turns or coil windings and which may be wound around the magnetic core Mcof inductors L2. In this way, a change of the magnetic field of the magnetic core Mcmay induce a voltage and / or current in the measurement coil 22 of the same frequency. This frequency therefore may be the same as the frequency of the alternating electric field, and the magnetic field of the inductors L2and / or of the magnetic core Mcmay be usedas the parameter indicative of the frequency of the alternating electric field according to the present disclosure. As the frequency of the magnetic field of the inductors

[0123]

[0124] L2and / or of the magnetic core Mcmay be comparatively high, the measurement coil 22 may be connected to a prescaler 23 or a phase locked loop 24, which may be configured to reduce the measured frequency by a predetermined factor so that the divided frequency may be reliably measured. The result of the measurement, i.e. the frequency of the alternating electrical field, may be provided to the controller 5 for use in further controlling the aerosol-forming device 2 as explained herein. Alternatively, the prescaled signal from the measurement coil 22 may be sent to the controller 5 and the controller 5 may be used to actually count or measure the frequency, for example using an analog to digital (AD) converter, which may be available in most types of controllers or can be provided as an external AD converter. A separate, dedicated voltage sensor may also be used (not shown).

[0125] In this and other variants, two inductors

[0126]

[0127] L2are shown as an exemplary embodiment , but it is also possible that there is only one coil L for the LC feedback loop resonant circuit 272 of the oscillator 355, and the same principles of measuring the magnetic field caused by a single inductor applies.

[0128] Figure 7 shows an alternative arrangement of the sensing device 19 comprising the measurement coil 22. Particularly, in this embodiment, the inductors U, L2may be free of a magnetic core Mc. The measurement coil 22 may again include one or more turns or coil windings and may be at least partly inserted into at least one or both of the inductors U, L2. The one or both inductors L-i , L2and the measurement coil 22 may be aligned with each other, for example such that the measurement coil axis 25 coincides with the coil axis 26 of the inductors

[0129]

[0130] L2. In other words, the measurement coil 22 and the one or both inductors L-i, L2may be coaxially arranged. In this way, the current and / or voltage induced in the measurement coil 22 by the changing magnetic field of the inductors L-i, L2has the largest possible magnitude and may therefore be reliably measured and / or detected. However, as explained before, slight deviations may also be acceptable. Again, the measurement coil 22 may be connected to a prescaler 23 or a phase locked loop 24 and ultimately may be connected to the controller 5 to deliver the results of the measurement to the controller 5. As before, also the controller 5 may itself be used for counting and / or measuring the frequency of the signal delivered from the measurement coil 22.

[0131] Another possible implementation of the sensing device 19 is shown in Figure 8. The sensing device 19 may directly tap or measure a voltage from the oscillation circuit 250, 355, for example from the feedback loop 270. This can be done by tapping the voltage right at the gate of the transistor T. In general, any suitable oscillation circuit 250, 355 may be used and its frequency measured in this way, for example via the amplifier of a quartz crystal oscillation circuit. The sensing device 19 may comprise a filter 27, which may, for example comprise a capacitor, forexample a small capacitor, acting as a low pass filter. Again, the sensing device 19 may also comprise a prescaler 23 or a phase locked loop 24 before the signal and / or the measurement result is transmitted to the controller 5 for determination and / or control of the aerosol-forming device 2. In this case, for example, the alternating voltage from the oscillation circuit 250, 355, for example from the feedback loop 270, may be used as the parameter indicative of the frequency of the alternating electric field according to the present disclosure. In other variants, it is possible that a voltage of an RF amplifier may be used as the parameter indicative of the frequency of the alternating electric field, for example the amplifier of an RF signal from an oscillator.

[0132] An implementation of the sensing device 19 directly determining the voltage from the oscillation circuit 250, 355 is shown in more detail in Figure 9. In this specific and non-limiting embodiment, the oscillation circuit 355 as shown in Figure 4 is used. However, other implementations of the oscillation circuit may also be used. The sensing device 19 may be connected to the gate of the transistor T of the oscillation circuit 355 and may be configured to measure the voltage, particularly the frequency of the alternating voltage, at the gate of the transistor T. The sensing device 19 may comprise a voltage divider 30, for example comprising two resistors 28 connected in series. The voltage divider 30 may be configured to scale down the voltage of the oscillation circuit 355 to voltage values which may be input into a voltage sensor and / or the controller 5 for measurement and / or determination. The scaled-down voltage may be tapped between the resistors 28 and may be filtered by filter 27 as described before. As also described before, a prescaler 23 or a phase locked loop 24 may be used to divide the frequency of the voltage inversions so as to provide a reliably measurable signal. The signal may then be measured and / or determined by a dedicated voltage sensor and / or by the controller 5. In this way, the frequency of the voltage inversions in the oscillating circuit 355 may be determined as the parameter indicative of the frequency of the alternating electrical field according to the present disclosure. As also shown in Figure 9, controller 5 may use the acquired information to control the power supply to the oscillation circuit 355, for example by controlling the DC / DC converter 29, which may be configured to provide electrical power from the energy storage 15 to the oscillation circuit 355.

[0133] Figure 10 shows a flowchart of the method 40 of monitoring dielectric heating of an aerosolforming article 18 in a portable and hand-held aerosol-forming device 2 and / or in a portable and hand-held aerosol-forming system 1 for forming aerosol for human inhalation. Method 40 may begin in step 41 with generating an alternating electric field for performing dielectric heating, for example by providing an oscillating current and / or voltage to at least two electrical contacts 160, 165 couplable or coupled to at least two electrodes 130, 135 of a load capacitor CL. This may lead to establishing an alternating electric field across the at least two electrodes 130, 135 for performing dielectric heating. The frequency of the oscillation may be influenced by severalfactors, for example by the temperature of the aerosol-forming article 18 and the substrate contained therein in the alternating electric field, by the grade of depletion of the aerosol-forming article 18, or whether the aerosol-forming article 18 has been properly or fully inserted or not. Therefore, the frequency of the alternating electric field is determined to infer these factors and their respective values. To this end, method 40 may comprise step 42 of detecting a parameter indicative of the frequency of the alternating electric field. Specifically, step 42 may be performed by or by using a sensing device 19 arranged outside of the load capacitor CL, i.e. outside of the alternating electric field and / or the heating chamber 20. As the sensing device 19 may be positioned and / or arranged such that the alternating electrical field strength is too low to be measured where the sensing device 19 is located, an indirect measurement of the frequency of the alternating electric field may be implemented. For example, the frequency of the alternating electric field may be determined by measuring the frequency of the magnetic field of an inductor LT, L2in the oscillation circuit 250, 355. As another example, the frequency of the alternating electric field may be determined by measuring the frequency of an alternating voltage in the oscillation circuit 250, 355, for example at the gate of a transistor T in the oscillation circuit 250, 355. From these parameters and / or from the frequency of the alternating electric field, the temperature of the aerosol-forming article 18 in the heating chamber 20 and / or the grade of depletion of the aerosol-forming article 18 may be determined. In turn, these values may then be used for controlling the aerosol-forming device 2, for example for controlling the amount of power supplied to the oscillation circuit 250, 355.

[0134] In summary, the present disclosure provides for improved monitoring and control of an aerosol-forming device 2 using dielectric heating. By implementing a frequency measurement of the alternating electric field which does not measure the field itself, a compact, efficient and energy saving aerosol-forming device 2 may be provided.

[0135] For the purpose of the present description and of the appended claims, except where otherwise indicated, all numbers expressing amounts, quantities, percentages, and so forth, are to be understood as being modified in all instances by the term "about". Also, all ranges include the maximum and minimum points disclosed and include any intermediate ranges therein, which may or may not be specifically enumerated herein. In this context, therefore, a number A is understood as A ±10 % of A. Within this context, a number A may be considered to include numerical values that are within general standard error for the measurement of the property that the number A modifies. The number A, in some instances as used in the appended claims, may deviate by the percentages enumerated above provided that the amount by which A deviates does not materially affect the basic and novel characteristic(s) of the claimed invention. Also, all ranges include the maximum and minimum points disclosed and include any intermediate ranges therein, which may or may not be specifically enumerated herein.

Claims

28 / 32CLAIMS1. A portable and hand-held aerosol-forming device for forming aerosol for human inhalation from an aerosol-forming article by dielectric heating, comprising:a dielectric heating arrangement including an oscillation circuit configured to oscillate freely, the arrangement generating of an alternating electric field for performing the dielectric heating,a heating chamber or receiving space configured to removably receive the aerosolforming article, anda sensing device arranged outside of the generated alternating electric field, wherein the sensing device is configured to detect a parameter indicative of a frequency of the alternating electric field.

2. The aerosol-forming device according to claim 1 , comprisingwherein the oscillation circuit is configured to provide an oscillating current and / or voltage to at least two electrical contacts couplable or coupled to at least two electrodes of a load capacitor so that an alternating electric field between the at least two electrodes is established for performing dielectric heating,wherein the sensing device is arranged outside of the load capacitor.

3. The aerosol-forming device according to any one of the previous claims,wherein the dielectric heating arrangement comprises a resonant cavity and / or a transmission line and is configured to provide an alternating electric field for performing the dielectric heating in the resonant cavity and / or the transmission line,wherein the sensing device is arranged outside of the resonant cavity and / or the transmission line.

4. The aerosol-forming device according to any one of the previous claims,wherein the sensing device is arranged and / or positioned outside the heating chamber or receiving space.

5. The aerosol-forming device according to any one of the previous claims,wherein the sensing device is configured to detect a parameter indirectly indicative of the frequency of the alternating electric field, particularly wherein the sensing device does not directly measure or detect changes to the alternating electric field.

6. The aerosol-forming device according to any one of the previous claims, wherein the oscillation circuit is a self-oscillating resonator circuit having a resonant feedback loop, the resonant feedback loop including the load capacitor and at least one inductor.

7. The aerosol-forming device according to any one of the previous claims,further including control circuitry including at least one controller and / or processor, wherein the control circuitry is configured to determine the frequency of the alternating electric field,for example wherein the control circuitry is configured to determine a temperature of the aerosol-forming article in the load capacitor and / or a grade of depletion of the aerosol-forming article from the detected parameter and / or the frequency of the alternating electric field, and / or for example wherein the control circuitry is configured to control a power supplied to the oscillation circuit dependent on the detected parameter and / or the frequency of the alternating electric field.

8. The aerosol-forming device according to any one of the previous claims,wherein the oscillation circuit is configured to provide an oscillating current and / or voltage of at least 100 MHz, for example at least 200 MHz or at least 300 MHz, but below 1.5 Ghz, for example below 1.2 GHz, and / orwherein the oscillation circuit is configured to provide an oscillating AC voltage across the at least two electrodes of the load capacitor having a peak value of at least 50 V, for example at least 75 V or at least 100 V or at least 125 V or at least 150 V or at least 175 V or at least 200 V.

9. The aerosol-forming device according to any one of the previous claims,wherein the oscillation circuit includes at least one inductor, for example at least one inductor coil, wherein the sensing device is configured to detect the frequency of a magnetic field of the at least one inductor,for example wherein the sensing device includes a measurement coil, wherein the measurement coil includes at least one turn, and wherein the measurement coil is at least partly arranged inside the inductor coil.

10. The aerosol-forming device according to the previous claim,wherein the measurement coil is arranged such that a measurement coil axis of the measurement coil coincides with a coil axis of the inductor coil orwherein the measurement coil is arranged such that a measurement coil axis of the measurement coil and a coil axis of the inductor coil are arranged at an angle of up to 30° or up to 20° or up to 15° or up to 10° or up to 5°.

11. The aerosol-forming device according to any one of the previous claims,wherein the oscillation circuit includes at least one transistor, wherein the sensing device is connected to a gate of the transistor and is configured to detect a voltage applied at the gate, for example wherein the sensing device includes a voltage divider configured to reduce the input voltage of the sensing device.

12. The aerosol-forming device according to any one of the previous claims,wherein the sensing device includes a prescaler or frequency divider, wherein the prescaler or frequency divider is configured to divide the frequency of an input signal of the sensing device by a factor, for example a factor of between 10 and 250 or of between 20 and 150, and / orwherein the sensing device includes a phase locked loop, PLL, wherein the PLL is configured to reduce the frequency of an input signal of the sensing device by a factor, for example a factor of between 10 and 250 or of between 20 and 150.

13. The aerosol-forming device according to any one of the previous claims,wherein the sensing device includes a band pass filter, for example a capacitor or capacitor-based band pass filter, wherein the band pass filter is configured to filter an input signal of the sensing device.

14. An aerosol-forming system including an aerosol-forming device according to any one of the previous claims, andfurther including an aerosol-forming article, for example wherein the aerosol-forming device is configured to generate or form aerosol from the aerosol-forming article by dielectric heating.

15. A method of monitoring dielectric heating of an aerosol-forming article in a portable and hand-held aerosol-forming device for forming aerosol for human inhalation, for example an aerosol-forming device according to any one of the previous claims 1-19, or in an aerosol-forming system, for example an aerosol-forming system according to the previous claim, including:generating an alternating electric field for performing dielectric heating; anddetecting a parameter indicative of a frequency of the alternating electric field by a sensing device arranged outside of the generated alternating electric field.

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