Patent Publication Number: US-2022225680-A1

Title: Apparatus for an aerosol generating device

Description:
PRIORITY CLAIM 
     The present application is a National Phase entry of PCT Application No. PCT/GB2020/051542, filed Jun. 25, 2020, which claims priority from Great Britain Application No. 1909385.5, filed Jun. 28, 2019, each of which is hereby fully incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present specification relates to an apparatus for an aerosol generating device. 
     BACKGROUND 
     Smoking articles, such as cigarettes, cigars and the like burn tobacco during use to create tobacco smoke. Attempts have been made to provide alternatives to these articles by creating products that release compounds without combusting. For example, tobacco heating devices heat an aerosol generating substrate such as tobacco to form an aerosol by heating, but not burning, the substrate. 
     SUMMARY 
     In a first aspect, this specification describes an apparatus for an aerosol generating device comprising: a resonant circuit (such as an LC resonant circuit) comprising one or more inductive elements (e.g. one or more inductive coils) for inductively heating a susceptor arrangement to heat an aerosol generating material to thereby generate an aerosol, wherein the inductive elements are mounted on a first external surface of a substrate; a switching arrangement (such as a bridge circuit) for enabling an alternating current to be generated from a voltage supply (e.g. a DC voltage supply) and flow through one or more of said inductive elements to cause inductive heating of the susceptor arrangement, wherein the switching arrangement comprises a plurality of transistors mounted to a second external surface of the substrate; and a heat sink, wherein the inductive elements of the resonant circuit and the transistors of the switching arrangement are thermally connected to the heat sink. 
     The transistors of the switching arrangement may be implemented using one or more flat no-lead packages (such as dual-flat no-lead packages, quad flat no-lead packages or similar technologies). 
     The heat sink may be formed, at least in part, on the first external surface of the substrate. Alternatively, or in addition, the heat sink is formed, at least in part, on the second external surface of the substrate. 
     The heat sink may be a copper heat reservoir. 
     The heat sink may be a ground plane. 
     The substrate may be a printed circuit board, such as a multi-layered printed circuit board. The heat sink may, for example, be formed, at least in part, on an internal layer of the multi-layer printed circuit board. 
     The first external surface of the substrate may be a top layer of a multi-layer printed circuit board and the second external surface of the substrate may be a bottom layer of the multi-layer printed circuit board. 
     The resonant circuit may further comprise a capacitor. 
     The switching arrangement may be configured to provide an impulse generation circuit for applying an impulse to the resonant circuit, wherein the applied impulse induces an impulse response. 
     In a second aspect, this specification describes a non-combustible aerosol generating device comprising an apparatus as described above with reference to the first aspect. The said apparatus may comprise a tobacco heating system. The aerosol generating device may be configured to receive a removable article comprising an aerosol generating material. The aerosol generating material may, for example, comprise an aerosol generating substrate and an aerosol forming material. The removable article may include the said susceptor arrangement. 
     In a third aspect, this specification describes a kit of parts comprising an article for use in a non-combustible aerosol generating system, wherein the non-combustible aerosol generating system comprises an apparatus including any of the features of the first aspect described above or an aerosol generating device including any of the features of the second aspect described above. The article may, for example, be a removable article comprising an aerosol generating material. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Example embodiments will now be described, by way of example only, with reference to the following schematic drawings, in which: 
         FIG. 1  is a block diagram of a system in accordance with an example embodiment; 
         FIG. 2  shows a non-combustible aerosol provision device in accordance with an example embodiment; 
         FIG. 3  is a view of a non-combustible aerosol provision device in accordance with an example embodiment; 
         FIG. 4  is a view of an article for use with a non-combustible aerosol provision device in accordance with an example embodiment; 
         FIG. 5  is a block diagram of a circuit in accordance with an example embodiment; 
         FIGS. 6 to 15  are block diagrams of systems in accordance with example embodiments; 
         FIG. 16  is a flow chart showing an algorithm in accordance with an example embodiment; 
         FIGS. 17 and 18  are plots demonstrating example uses of example embodiments; 
         FIG. 19  is a flow chart showing an algorithm in accordance with an example embodiment; 
         FIG. 20  is a block diagram of a circuit switching arrangement in accordance with an example embodiment; 
         FIG. 21  is a block diagram of a circuit switching arrangement in accordance with an example embodiment; and 
         FIGS. 22 and 23  are flow charts showing algorithms in accordance with example embodiments. 
     
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS 
     As used herein, the term “delivery system” is intended to encompass systems that deliver a substance to a user, and includes: 
     combustible aerosol provision systems, such as cigarettes, cigarillos, cigars, and tobacco for pipes or for roll-your-own or for make-your-own cigarettes (whether based on tobacco, tobacco derivatives, expanded tobacco, reconstituted tobacco, tobacco substitutes or other smokable material); 
     non-combustible aerosol provision systems that release compounds from an aerosolizable material without combusting the aerosolizable material, such as electronic cigarettes, tobacco heating products, and hybrid systems to generate aerosol using a combination of aerosolizable materials; 
     articles comprising aerosolizable material and configured to be used in one of these non-combustible aerosol provision systems; and 
     aerosol-free delivery systems, such as lozenges, gums, patches, articles comprising inhalable powders, and smokeless tobacco products such as snus and snuff, which deliver a material to a user without forming an aerosol, wherein the material may or may not comprise nicotine. 
     According to the present disclosure, a “combustible” aerosol provision system is one where a constituent aerosolizable material of the aerosol provision system (or component thereof) is combusted or burned in order to facilitate delivery to a user. 
     According to the present disclosure, a “non-combustible” aerosol provision system is one where a constituent aerosolizable material of the aerosol provision system (or component thereof) is not combusted or burned in order to facilitate delivery to a user. 
     In embodiments described herein, the delivery system is a non-combustible aerosol provision system, such as a powered non-combustible aerosol provision system. 
     In one embodiment, the non-combustible aerosol provision system is an electronic cigarette, also known as a vaping device or electronic nicotine delivery system (END), although it is noted that the presence of nicotine in the aerosolizable material is not a requirement. 
     In one embodiment, the non-combustible aerosol provision system is a tobacco heating system, also known as a heat-not-burn system. 
     In one embodiment, the non-combustible aerosol provision system is a hybrid system to generate aerosol using a combination of aerosolizable materials, one or a plurality of which may be heated. Each of the aerosolizable materials may be, for example, in the form of a solid, liquid or gel and may or may not contain nicotine. In one embodiment, the hybrid system comprises a liquid or gel aerosolizable material and a solid aerosolizable material. The solid aerosolizable material may comprise, for example, tobacco or a non-tobacco product. 
     Typically, the non-combustible aerosol provision system may comprise a non-combustible aerosol provision device and an article for use with the non-combustible aerosol provision system. However, it is envisaged that articles which themselves comprise a means for powering an aerosol generating component may themselves form the non-combustible aerosol provision system. 
     In one embodiment, the non-combustible aerosol provision device may comprise a power source and a controller. The power source may be an electric power source or an exothermic power source. In one embodiment, the exothermic power source comprises a carbon substrate which may be energized so as to distribute power in the form of heat to an aerosolizable material or heat transfer material in proximity to the exothermic power source. In one embodiment, the power source, such as an exothermic power source, is provided in the article so as to form the non-combustible aerosol provision. 
     In one embodiment, the article for use with the non-combustible aerosol provision device may comprise an aerosolizable material, an aerosol generating component, an aerosol generating area, a mouthpiece, and/or an area for receiving aerosolizable material. 
     In one embodiment, the aerosol generating component is a heater capable of interacting with the aerosolizable material so as to release one or more volatiles from the aerosolizable material to form an aerosol. In one embodiment, the aerosol generating component is capable of generating an aerosol from the aerosolizable material without heating. For example, the aerosol generating component may be capable of generating an aerosol from the aerosolizable material without applying heat thereto, for example via one or more of vibrational, mechanical, pressurization or electrostatic means. 
     In one embodiment, the aerosolizable material may comprise an active material, an aerosol forming material and optionally one or more functional materials. The active material may comprise nicotine (optionally contained in tobacco or a tobacco derivative) or one or more other non-olfactory physiologically active materials. A non-olfactory physiologically active material is a material which is included in the aerosolizable material in order to achieve a physiological response other than olfactory perception. 
     The aerosol forming material may comprise one or more of glycerine, glycerol, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, 1,3-butylene glycol, erythritol, meso-Erythritol, ethyl vanillate, ethyl laurate, a diethyl suberate, triethyl citrate, triacetin, a diacetin mixture, benzyl benzoate, benzyl phenyl acetate, tributyrin, lauryl acetate, lauric acid, myristic acid, and propylene carbonate. 
     The one or more functional materials may comprise one or more of flavors, carriers, pH regulators, stabilizers, and/or antioxidants. 
     In one embodiment, the article for use with the non-combustible aerosol provision device may comprise aerosolizable material or an area for receiving aerosolizable material. In one embodiment, the article for use with the non-combustible aerosol provision device may comprise a mouthpiece. The area for receiving aerosolizable material may be a storage area for storing aerosolizable material. For example, the storage area may be a reservoir. In one embodiment, the area for receiving aerosolizable material may be separate from, or combined with, an aerosol generating area. 
     Aerosolizable material, which also may be referred to herein as aerosol generating material, is material that is capable of generating aerosol, for example when heated, irradiated or energized in any other way. Aerosolizable material may, for example, be in the form of a solid, liquid or gel which may or may not contain nicotine and/or flavorants. In some embodiments, the aerosolizable material may comprise an “amorphous solid”, which may alternatively be referred to as a “monolithic solid” (i.e. non-fibrous). In some embodiments, the amorphous solid may be a dried gel. The amorphous solid is a solid material that may retain some fluid, such as liquid, within it. 
     The aerosolizable material may be present on a substrate. The substrate may, for example, be or comprise paper, card, paperboard, cardboard, reconstituted aerosolizable material, a plastics material, a ceramic material, a composite material, glass, a metal, or a metal alloy. 
       FIG. 1  is a block diagram of a system, indicated generally by the reference numeral  10 , in accordance with an example embodiment. System  10  comprises a power source in the form of a direct current (DC) voltage supply  11 , a switching arrangement  13 , a resonant circuit  14 , a susceptor arrangement  16 , and a control circuit  18 . The switching arrangement  13  and the resonant circuit  14  may be coupled together in an inductive heating arrangement  12 . 
     The resonant circuit  14  may comprise a capacitor and one or more inductive elements for inductively heating the susceptor arrangement  16  to heat an aerosol generating material. Heating the aerosol generating material may thereby generate an aerosol. 
     The switching arrangement  13  may enable an alternating current to be generated from the DC voltage supply  11 . The alternating current may flow through the one or more inductive elements and may cause the heating of the susceptor arrangement. The switching arrangement may comprise a plurality of transistors. Example DC-AC converters include H-bridge or inverter circuits, examples of which are discussed below. It should be noted that the provision of a DC voltage supply  11  from which a pseudo AC signal is generated is not an essential feature; for example, a controllable AC supply or an AC-AC converter may be provided. Thus, an AC input could be provided (such as from a mains supply or an inverter). 
     Example arrangements of the switching arrangement  13  and the resonant circuit  14  are discussed in greater detail in  FIGS. 5 to 14 . 
       FIGS. 2 and 3  show a non-combustible aerosol provision device, indicated generally by the reference numeral  20 , in accordance with an example embodiment.  FIG. 2  is a perspective view of an aerosol provision device  20 A with an outer cover. The aerosol provision device  20 A may comprise a replaceable article  21  that may be inserted in the aerosol provision device  20 A to enable heating of a susceptor comprised within the article  21  (or provided elsewhere). The aerosol provision device  20 A may further comprise an activation switch  22  that may be used for switching on or switching off the aerosol provision device  20 A. Further elements of the aerosol provision device  20  are illustrated in  FIG. 3 . 
       FIG. 3  depicts an aerosol provision device  20 B with the outer cover removed. The aerosol generating device  20 B comprises the article  21 , the activation switch  22 , a plurality of inductive elements  23   a ,  23   b , and  23   c , and one or more air tube extenders  24  and  25 . The one or more air tube extenders  24  and  25  may be optional. 
     The plurality of inductive elements  23   a ,  23   b , and  23   c  may each form part of a resonant circuit, such as the resonant circuit  14 . The inductive element  23   a  may comprise a helical inductor coil. In one example, the helical inductor coil is made from Litz wire/cable which is wound in a helical fashion to provide the helical inductor coil. Many alternative inductor formations are possible, such as inductors formed within a printed circuit board. The inductive elements  23   b  and  23   c  may be similar to the inductive element  23   a . The use of three inductive elements  23   a ,  23   b  and  23   c  is not essential to all example embodiments. Thus, the aerosol generating device  20  may comprise one or more inductive elements. 
     A susceptor may be provided as part of the article  21 . In an example embodiment, when the article  21  is inserted in aerosol generating device, the aerosol generating device  20  may be turned on due to the insertion of the article  21 . This may be due to detecting the presence of the article  21  in the aerosol generating device using an appropriate sensor (e.g., a light sensor) or, in cases where the susceptor forms a part of the article  21 , by detecting the presence of the susceptor using the resonant circuit  14 , for example. When the aerosol generating device  20  is turned on, the inductive elements  23  may cause the article  21  to be inductively heated through the susceptor. In an alternative embodiment, the susceptor may be provided as part of the aerosol generating device  20  (e.g. as part of a holder for receiving the article  21 ). 
       FIG. 4  is a view of an article, indicated generally by the reference numeral  30 , for use with a non-combustible aerosol provision device in accordance with an example embodiment. The article  30  is an example of the replaceable article  21  described above with reference to  FIGS. 2 and 3 . 
     The article  30  comprises a mouthpiece  31 , and a cylindrical rod of aerosol generating material  33 , in the present case tobacco material, connected to the mouthpiece  31 . The aerosol generating material  33  provides an aerosol when heated, for instance within a non-combustible aerosol generating device, such as the aerosol generating device  20 , as described herein. The aerosol generating material  33  is wrapped in a wrapper  32 . The wrapper  32  can, for instance, be a paper or paper-backed foil wrapper. The wrapper  32  may be substantially impermeable to air. 
     In one embodiment, the wrapper  32  comprises aluminum foil. Aluminum foil has been found to be particularly effective at enhancing the formation of aerosol within the aerosol generating material  33 . In one example, the aluminum foil has a metal layer having a thickness of about 6 μm. The aluminum foil may have a paper backing. However, in alternative arrangements, the aluminum foil can have other thicknesses, for instance between 4 μm and 16 μm in thickness. The aluminum foil also need not have a paper backing, but could have a backing formed from other materials, for instance to help provide an appropriate tensile strength to the foil, or it could have no backing material. Metallic layers or foils other than aluminum can also be used. Moreover, it is not essential that such metallic layers are provided as part of the article  30 ; for example, such a metallic layer could be provided as part of the apparatus  20 . 
     The aerosol generating material  33 , also referred to herein as an aerosol generating substrate  33 , comprises at least one aerosol forming material. In the present example, the aerosol forming material is glycerol. In alternative examples, the aerosol forming material can be another material as described herein or a combination thereof. The aerosol forming material has been found to improve the sensory performance of the article, by helping to transfer compounds such as flavor compounds from the aerosol generating material to the consumer. 
     As shown in  FIG. 4 , the mouthpiece  31  of the article  30  comprises an upstream end  31   a  adjacent to an aerosol generating substrate  33  and a downstream end  31   b  distal from the aerosol generating substrate  33 . The aerosol generating substrate may comprise tobacco, although alternatives are possible. 
     The mouthpiece  31 , in the present example, includes a body of material  36  upstream of a hollow tubular element  34 , in this example adjacent to and in an abutting relationship with the hollow tubular element  34 . The body of material  36  and hollow tubular element  34  each define a substantially cylindrical overall outer shape and share a common longitudinal axis. The body of material  36  is wrapped in a first plug wrap  37 . The first plug wrap  37  may have a basis weight of less than 50 gsm, such as between about 20 gsm and 40 gsm. 
     In the present example the hollow tubular element  34  is a first hollow tubular element  34  and the mouthpiece includes a second hollow tubular element  38 , also referred to as a cooling element, upstream of the first hollow tubular element  34 . In the present example, the second hollow tubular element  38  is upstream of, adjacent to and in an abutting relationship with the body of material  36 . The body of material  36  and second hollow tubular element  38  each define a substantially cylindrical overall outer shape and share a common longitudinal axis. The second hollow tubular element  38  is formed from a plurality of layers of paper which are parallel wound, with butted seams, to form the tubular element  38 . In the present example, first and second paper layers are provided in a two-ply tube, although in other examples 3, 4 or more paper layers can be used forming 3, 4 or more ply tubes. Other constructions can be used, such as spirally wound layers of paper, cardboard tubes, tubes formed using a papier-mâché type process, molded or extruded plastic tubes or similar. The second hollow tubular element  38  can also be formed using a stiff plug wrap and/or tipping paper as the second plug wrap  39  and/or tipping paper  35  described herein, meaning that a separate tubular element is not required. 
     The second hollow tubular element  38  is located around and defines an air gap within the mouthpiece  31  which acts as a cooling segment. The air gap provides a chamber through which heated volatilized components generated by the aerosol generating material  33  may flow. The second hollow tubular element  38  is hollow to provide a chamber for aerosol accumulation yet rigid enough to withstand axial compressive forces and bending moments that might arise during manufacture and whilst the article  21  is in use. The second hollow tubular element  38  provides a physical displacement between the aerosol generating material  33  and the body of material  36 . The physical displacement provided by the second hollow tubular element  38  will provide a thermal gradient across the length of the second hollow tubular element  38 . 
     Of course, the article  30  is provided by way of example only. The skilled person will be aware of many alternative arrangements of such an article that could be used in the systems described herein. 
       FIG. 5  is a block diagram of a circuit, indicated generally by the reference numeral  40 , in accordance with an example embodiment. The circuit  40  comprises a positive terminal  47  and a negative (ground) terminal  48  (that are an example implementation of the DC voltage supply  11  of the system  10  described above). The circuit  40  comprises a switching arrangement  44  (implementing the switching arrangement  13  described above), where the switching arrangement  44  comprises a bridge circuit (e.g. an H-bridge circuit, such as an FET H-bridge circuit). The switching arrangement  44  comprises a first circuit branch  44   a  and a second circuit branch  44   b , where the first circuit branch  44   a  and the second circuit branch  44   b  may be coupled by a resonant circuit  49  (implementing the resonant circuit  14  described above). The first circuit branch  44   a  comprises switches  45   a  and  45   b , and the second circuit branch  44   b  comprises switches  45   c  and  45   d . The switches  45   a ,  45   b ,  45   c , and  45   d  may be transistors, such as field-effect transistors (FETs), and may receive inputs from a controller, such as the control circuit  18  of the system  10 . The resonant circuit  49  comprises a capacitor  46  and an inductive element  43  such that the resonant circuit  49  may be an LC resonant circuit. The circuit  40  further shows a susceptor equivalent circuit  42  (thereby implementing the susceptor arrangement  16 ). The susceptor equivalent circuit  42  comprises a resistance and an inductive element that indicate the electrical effect of an example susceptor arrangement  16 . When a susceptor is present, the susceptor arrangement  42  and the inductive element  43  may act as a transformer  41 . Transformer  41  may produce a varying magnetic field such that the susceptor is heated when the circuit  40  receives power. During a heating operation, in which the susceptor arrangement  16  is heated by the inductive arrangement, the switching arrangement  44  is driven (e.g., by control circuit  18 ) such that each of the first and second branches are coupled in turn such that an alternating current is passed through the resonant circuit  14 . The resonant circuit  14  will have a resonant frequency, which is based in part on the susceptor arrangement  16 , and the control circuit  18  may be configured to control the switching arrangement  44  to switch at the resonance frequency or a frequency close to the resonant frequency. Driving the switching circuit at or close to resonance helps improve efficiency and reduces the energy being lost to the switching elements (which causes unnecessary heating of the switching elements). In an example in which the article  21  comprising an aluminum foil is to be heated, the switching arrangement  44  may be driven at a frequency of around 2.5 MHz. However, in other implementations, the frequency may, for example, be anywhere between 500 kHz to 4 MHz. 
     A susceptor is a material that is heatable by penetration with a varying magnetic field, such as an alternating magnetic field. The heating material may be an electrically-conductive material, so that penetration thereof with a varying magnetic field causes induction heating of the heating material. The heating material may be magnetic material, so that penetration thereof with a varying magnetic field causes magnetic hysteresis heating of the heating material. The heating material may be both electrically-conductive and magnetic, so that the heating material is heatable by both heating mechanisms. 
     Induction heating is a process in which an electrically-conductive object is heated by penetrating the object with a varying magnetic field. The process is described by Faraday&#39;s law of induction and Ohm&#39;s law. An induction heater may comprise an electromagnet and a device for passing a varying electrical current, such as an alternating current, through the electromagnet. When the electromagnet and the object to be heated are suitably relatively positioned so that the resultant varying magnetic field produced by the electromagnet penetrates the object, one or more eddy currents are generated inside the object. The object has a resistance to the flow of electrical currents. Therefore, when such eddy currents are generated in the object, their flow against the electrical resistance of the object causes the object to be heated. This process is called Joule, ohmic, or resistive heating. An object that is capable of being inductively heated is known as a susceptor. 
     In one embodiment, the susceptor is in the form of a closed circuit. It has been found in some embodiments that, when the susceptor is in the form of a closed circuit, magnetic coupling between the susceptor and the electromagnet in use is enhanced, which results in greater or improved Joule heating. 
     Magnetic hysteresis heating is a process in which an object made of a magnetic material is heated by penetrating the object with a varying magnetic field. A magnetic material can be considered to comprise many atomic-scale magnets, or magnetic dipoles. When a magnetic field penetrates such material, the magnetic dipoles align with the magnetic field. Therefore, when a varying magnetic field, such as an alternating magnetic field, for example as produced by an electromagnet, penetrates the magnetic material, the orientation of the magnetic dipoles changes with the varying applied magnetic field. Such magnetic dipole reorientation causes heat to be generated in the magnetic material. 
     When an object is both electrically-conductive and magnetic, penetrating the object with a varying magnetic field can cause both Joule heating and magnetic hysteresis heating in the object. Moreover, the use of magnetic material can strengthen the magnetic field, which can intensify the Joule heating. 
     In each of the above processes, as heat is generated inside the object itself, rather than by an external heat source by heat conduction, a rapid temperature rise in the object and more uniform heat distribution can be achieved, particularly through selection of suitable object material and geometry, and suitable varying magnetic field magnitude and orientation relative to the object. Moreover, as induction heating and magnetic hysteresis heating do not require a physical connection to be provided between the source of the varying magnetic field and the object, design freedom and control over the heating profile may be greater, and cost may be lower. 
       FIG. 6  is a block diagram of a system, indicated generally by the reference numeral  50 , in accordance with an example embodiment. System  50  comprises a resonant circuit  51  (similar to the resonant circuit  14 ), a switching arrangement  52  (similar to the switching arrangement  13 ), and a substrate  53 . As discussed above with respect to  FIG. 5 , the resonant circuit  51  may comprise one or more inductive elements and the switching arrangement  52  may comprise a plurality of transistors. The one or more inductive elements may be mounted on a first external surface  54  of the substrate  53 . The plurality of transistors may be mounted on a second external surface  55  of the substrate  53 . The substrate  53  may be a printed circuit board (PCB). The resonant circuit  51  may include a capacitor although, as noted below, the capacitor may be provided elsewhere in the system  50 . 
     The resonant circuit  51  and the switching arrangement  52  may generate heat that may cause the overall temperature of the system  50  to rise. It may be beneficial to mount the resonant circuit  51  (or at least one or more inductive elements thereof) on the first surface  54 , and the switching arrangement  52  on the second surface  55 , so that the resonant circuit  51  and the switching arrangement  52  may, at least partially, be thermally isolated from each other by the substrate  53 . 
       FIG. 7  is a block diagram of a system, indicated generally by the reference numeral  60 A, in accordance with an example embodiment. System  60 A (showing a cross-section) comprises the substrate  53 , one or more inductive elements of the resonant circuit  51  mounted on the first external surface  54  of the substrate  53 , the plurality of transistors of the switching arrangement  52  mounted on the second external surface  55  of the substrate  53 , and a heat sink  61 . The one or more inductive elements of the resonant circuit  51  are thermally connected to the heat sink  61  via connections  62 , and the plurality of transistors of the switching arrangement  52  are thermally connected to the heat sink  61  via connections  63 . 
     In an example embodiment, the switching arrangement  52  may be implemented using one or more integrated circuits. The integrated circuits may be provided within a protective material (such as plastic) which provides some protection against damage due to handling or the like to the integrated circuits. Such arrangements are typically known as packages (or sometimes electrical packages). While packages offer protection to the integrated circuitry embedded within (or covered by) the protective material, heat dissipation can be negatively impacted. The plurality of transistors of the switching arrangement  52  may be implemented using one or more flat no-lead packages. The flat no-lead packages may be dual-flat no-leads (DFN) packages, quad-flat no-leads (QFN) packages or similar packages. 
     Use of DFN or QFN packages may enable improved heat dissipation from the switching arrangement  52  to the substrate  53  on which substrate  53  the DFN/QFN packages may be mounted. DFN and QFN packages typically include an exposed thermal pad (that is, an element, such as a metallic element, which has at least one exposed surface that is not covered by the protective material), which can improve heat dissipation. The improved heat dissipation may enable the switching arrangement  52  to be run at loads generating greater heat than would be achievable using other forms of integrated circuits that do not use DFN or QFN packages. 
     The heat sink  61  may provide increased heat dissipation, and thereby may allow maintaining the temperature of the printed circuit board below a threshold temperature. The heat sink  61  may be formed on the first external surface  54  of the substrate  53 . The heat sink  61  (and other heat sinks described herein) may, for example, be in the form of a copper mass (e.g. a copper plane) to absorb, spread and dissipate heat. The skilled person will be aware of alternative arrangements. 
     The heat sink  61  may be arranged such that the resonant circuit  51  may only be thermally connected to the heat sink  61  via connections  62 . As such, the remaining surface of the heat sink  61  may be isolated from the surface of the resonant circuit  51  with a fluid, such as air, or any other cooling medium. 
     In implementations where the switching arrangement  52  is implemented using one or more flat no-lead packages, the connections  63  may run from the thermal pad to the heat sink  61 . The connections  63  may pass through the substrate  63 , for example, in the form of vias. 
       FIG. 8  is a top-view, indicated generally by the reference numeral  60 B, of the system  60 A, in accordance with an example embodiment. As illustrated in the top view  60 B, the heat sink  61  and the resonant circuit  51  (or at least the inductive element(s) thereof) may be isolated by a gap  64  or other electrically insulating material, for example to prevent short-circuits. 
       FIG. 9  is a block diagram of a system, indicated generally by the reference numeral  70 , in accordance with an example embodiment. System  70  comprises the substrate  53 , one or more inductive elements of the resonant circuit  51  mounted on the first external surface  54  of the substrate  53 , the plurality of transistors of the switching arrangement  52  mounted on the second external surface  55  of the substrate  53 , and a heat sink  71 . The one or more inductive elements of the resonant circuit  51  are thermally connected to the heat sink  71  via connections  72 , and the plurality of transistors of the switching arrangement  52  are thermally connected to the heat sink  71  via connections  73 . The heat sink  71  may be formed on the second external surface  55  of the substrate  53 . 
     The heat sink  71  may be arranged such that the switching arrangement  52  may only be thermally connected to the heat sink  71  via connections  73 . As such, the remaining surface of the heat sink  71  may be isolated from the surface of the switching arrangement  52  with a fluid, such as air, or any other cooling medium. 
     In implementations where the switching arrangement  52  is implemented using one or more flat no-lead packages, the thermal pad may be directly connected to the heat sink  71 . The thermal pad is electrically isolated from the integrated circuit. 
       FIG. 10  is a bottom view, indicated generally by the reference numeral  70 B, of the system  70 A, in accordance with an example embodiment. As illustrated in the bottom view  70 B, the heat sink  71  and the switching arrangement  52  may be isolated by a gap  74  or other electrically insulating material, for example to prevent short-circuits. 
     In an example embodiment, the heat sinks  61  and/or  71  may be a copper heat reservoir. Alternatively, the heat sinks  61  and/or  71  may be an aluminum heat reservoir. In an example embodiment, the heat sinks  61  and/or  71  may be a ground plane. 
     A heat sink, such as heat sinks  61  and  71 , transfers thermal energy from a higher temperature device to a lower temperature fluid medium. The fluid medium is frequently air, but can also be water, refrigerants or oil. If the fluid medium is water, the heat sink is frequently called a cold plate. The heat sink may be a heat reservoir that can absorb an arbitrary amount of heat without significantly changing temperature. 
       FIG. 11  is a block diagram of a system, indicated generally by the reference numeral  80 , in accordance with an example embodiment. System  80  comprises the resonant circuit  51 , the switching arrangement  52 , and a substrate  81 . The substrate  81  may be a printed circuit board. The printed circuit board may be a multi-layered printed circuit board comprising a plurality of layers  82 . 
       FIG. 12  is a block diagram of a system, indicated generally by the reference numeral  90 , in accordance with an example embodiment. System  90  comprises the resonant circuit  51 , the switching arrangement  52 , a substrate  92 , and a heat sink  91 . The substrate  92  may be a multi-layered printed circuit board. The heat sink  91  may be formed, at least in part, on an internal layer of the substrate  92 , which substrate  92  is a multi-layered printed circuit board. The resonant circuit  51  may be thermally connected to the heat sink  91  via connections  93 , and the switching arrangement  52  may be thermally connected to the heat sink  91  via the connections  94 . 
       FIG. 13  is a block diagram of a system, indicated generally by the reference numeral  100 , in accordance with an example embodiment. System  100  comprises the resonant circuit  51 , the switching arrangement  52 , a substrate  101 , and a plurality of layers  102 ,  103 , and  104 . The layers include a layer  103  formed on a first external surface of the substrate  101 , a layer  102  formed on an internal layer of the substrate  101 , and a layer  104  formed on a second external surface of the substrate  101 . One of more of said layers  102  to  104  could be used as a heat sink. Moreover, one or more of said layers could be used for some other purpose (e.g. routing of electrical signals). 
     By way of example, the resonant circuit  51  may be thermally and or electrically connected to one or more of the layers  102  to  104  (for example via connections  109 ,  105  and  108  respectively). Similarly, the switching arrangement  52  may be thermally or electrically connected to one or more of the layers  102  to  104  (for example via connections  110 ,  107  and  106  respectively). 
     In some of the example arrangements described above, a resonant circuit has been provided on a first external surface of a substrate (e.g. a printed circuited board) and a switching arrangement on a second external surface of the substrate, with the resonant circuit including one or more inductive elements and at least one capacitor. This is not essential to all embodiments. For example,  FIG. 14  is a block diagram of a system, indicated generally by the reference numeral  110 , comprising one or more inductive elements  111 , a switching arrangement  112  and at least one capacitive element  113 . The inductive element(s) and the capacitive element(s) form one or more resonant circuits. The one or more inductive elements are mounted on a first external surface  115  of a substrate  114 . The switching arrangement (e.g. a plurality of transistors, as discussed above) is mounted on a second external surface  116  of the substrate  114 . In the example system  110 , the capacitor(s) are also mounted on the second external surface  116  of the substrate. 
       FIG. 15  is a block diagram of a system, indicated generally by the reference numeral  200 , in accordance with an example embodiment. The system  200  comprises the resonant circuit  14  and the susceptor  16  of the system  10  described above. The system  200  further comprises an impulse generation circuit  202  and an impulse response processor  204 . The impulse generation circuit  202  and the impulse response processor  204  may be implemented as part of the control circuit  18  of the system  10 . 
     The impulse generation circuit  202  may be implemented using a first switching arrangement (such as an H-bridge circuit) to generate the impulse by switching between positive and negative voltage sources. For example, the switching arrangement  44  described above with reference to  FIG. 5  may be used. As described further below, the impulse generation circuit  202  may generate an impulse by changing the switching states of the FETs of the switching arrangement  44  from a condition where the switches  45   b  and  45   d  are both on (such that the switching arrangement is grounded) and the switches  45   a  and  45   b  are off, to a state where the switch states of one of the first and second circuit branches  44   a  and  44   b  are reversed. The impulse generation circuit  202  may alternatively be provided using a pulse width modulation (PWM) circuit. Other impulse generation arrangements are also possible. 
     The impulse response processor  204  may determine one or more performance metrics (or characteristics) of the resonant circuit  14  and the susceptor  16  based on the impulse response. Such performance metrics include properties of an article (such as the removable article  21 ), presence or absence of such an article, type of article, temperature of operation etc. 
       FIG. 16  is a flow chart showing an algorithm, indicated generally by the reference numeral  210 , in accordance with an example embodiment. The algorithm  210  shows an example use of the system  200 . 
     The algorithm  210  starts at operation  212  where an impulse (generated by the impulse generation circuit  202 ) is applied to the resonant circuit  14 .  FIG. 17  is a plot, indicated generally by the reference numeral  220 , showing an example impulse that might be applied in the operation  212 . 
     The impulse may be applied to the resonant circuit  14 . Alternatively, in systems having multiple inductive elements (such as non-combustible aerosol arrangement  20  described above with reference to  FIGS. 2 and 3 ), the impulse generation circuit  202  may select one of a plurality of resonant circuits, each resonant circuit comprising an inductive element for inductively heating a susceptor and a capacitor, wherein the applied impulse induces an impulse response between the capacitor and the inductive element of the selected resonant circuit. 
     At operation  214 , an output is generated (by the impulse response processor  204 ) based on an impulse response that is generated in response to the impulse applied in operation  212 .  FIG. 18  is a plot, indicated generally by the reference numeral  225 , showing an example impulse response that might be received at the impulse response processor  204  is response to the impulse  220 . As shown in  FIG. 18 , the impulse response may take the form of a ringing resonance. The impulse response is a result of charge bouncing between the inductor(s) and capacitor of the resonant circuit  14 . In one arrangement, no heating of the susceptor is caused as a result. That is, the temperature of the susceptor remains substantially constant (e.g., within ±1° C. or ±0.1° C. of the temperature prior to applying the impulse). 
     At least some of the properties of the impulse response (such as frequency and/or decay rate of the impulse response) provide information regarding the system to which the impulse is applied. Thus, the system  200  can be used to determine one or more properties of the system to which the impulse is applied. For example one or more performance properties, such as fault conditions, properties of an inserted article  21 , presence or absence of such an article, whether the article  21  is genuine, temperature of operation etc., can be determined based on output signal derived from an impulse response. The system  200  may use the determined one or more properties of the system to perform further actions (or prevent further actions if so desired) using the system  10 , for example, to perform heating of the susceptor arrangement  16 . For instance, based on the determined temperature of operation, the system  200  can choose what level of power is to be supplied to the induction arrangement to cause further heating of the susceptor arrangement, or whether power should be supplied at all. For some performance properties, such as fault conditions or determining whether the article  21  is genuine, a measured property of the system (as measured using the impulse response) can be compared to an expected value or range of values for the property, and actions taken by the system  200  are performed on the basis of the comparison. 
       FIG. 19  is a flow chart showing an algorithm, indicated generally by the reference numeral  230 , in accordance with an example embodiment. At operation  232  of the algorithm  230 , an impulse is applied to the resonant circuit  14  by the impulse generation circuit  202 . Thus, the operation  232  is the same as the operation  212  described above. 
     At operation  234  of the algorithm  230 , a period of an impulse response induced in response to the applied impulse is determined by the impulse response processor  204 . Finally, at operation  236 , an output is generated (based on the determined period of the impulse response). 
       FIG. 20  is a block diagram of a circuit switching arrangement, indicated generally by the reference numeral  380 , in accordance with an example embodiment. The switching arrangement  380  shows switch positions of the circuit  40  in a first state, indicated generally by the reference numeral  382 , and a second state, indicated generally by the reference numeral  383 . 
     In the first state  382 , the switches  45   a  and  45   c  of the circuit  40  are off (i.e. open) and the switches  45   b  and  45   d  are on (i.e. closed). In the second state  383 , the switches  45   a  and  45   d  are on (i.e. closed) and the switches  45   b  and  45   c  are off. Thus, in the first state  382 , both sides of the resonant circuit  49  are connected to ground. In the second state  383 , a voltage pulse (i.e. an impulse) is applied to the resonant circuit. 
       FIG. 21  is a block diagram of a circuit switching arrangement, indicated generally by the reference numeral  390 , in accordance with an example embodiment. The switching arrangement  390  shows switch positions of the circuit  40  in a first state, indicated generally by the reference numeral  392 , and a second state, indicated generally by the reference numeral  393 . 
     In the first state  392 , the switch  45   b  is on (i.e. closed) and the switches  45   a ,  45   c  and  45   d  are off (i.e. open). Thus, one side of the resonant circuit  49  is grounded. In the second state  393 , a voltage pulse (i.e. an impulse) is applied to the resonant circuit. 
     In the second state  382  of the switching arrangement  380 , a current is able to flow through the first switch  45   a , the resonant circuit  49  and the switch  45   d . This current flow may lead to heat generation and discharging of a power supply (such as a battery). In the second state  393  of the switching arrangement  390 , a current will not flow through the switch  45   d . Accordingly, heat generation and power supply discharge may be reduced. Moreover, noise generation may be reduced on the generation of each impulse. 
       FIG. 22  is a flow chart, indicated generally by the reference numeral  400 , showing an algorithm in accordance with an example embodiment. The algorithm  400  shows an example use of the systems described herein. 
     The algorithm  400  starts with a measurement operation  401 . The measurement operation  401  may, for example, include a temperature measurement. Next, at operation  402 , a heating operation is carried out. The implementation of the heating operation  402  may be dependent on the output of the measurement operation  401 . Once the heating operation  402  is complete, the algorithm  400  returns to operation  401 , where the measurement operation is repeated. 
     The operation  401  may be implemented by the system  200  in which an impulse is applied by the impulse generation circuit  202  and a measurement (e.g. a temperature measurement) determined based on the output of the impulse response processor  204 . As discussed above, a temperature measurement may be based, for example, on a decay rate, an impulse response time, an impulse response period etc. 
     The operation  402  may be implemented by controlling the inductive heating arrangement  12  in order to heat the susceptor  16  of the system  10 . The inductive heating arrangement  12  may be driven at or close to the resonant frequency of the resonant circuit, in order to cause an efficient heating process. The resonant frequency may be determined based on the output of the operation  401 . 
     In one implementation of the algorithm  400 , the measurement operation is conducted for a first period of time, the heating operation  402  is conducted for a second period of time and the process is then repeated. For example, the first period of time may be 10 ms and the second period of time may be 250 ms, although other time periods are possible. In other words, the measurement operation may be performed between successive heating operations. It should also be noted that the heating operation  402  being conducted for the second period of time does not necessarily imply that power is supplied to the induction coil for the whole duration of the second period of time. For example, power may only be supplied for a fraction of the second period of time. 
     In an alternative embodiment, the algorithm  400  may be implemented with the heating operation  402  having a duration dependent on a required level of heating (with the heating duration being increased if more heating is required and reduced if less heating is required). In such an algorithm, the measurement operation  401  may simply be carried out when heating is not being conducted, such that the heating operation  402  need not be interrupted in order to conduct the measurement operation  401 . This interleaved heating arrangement may be referred to as a pulse-width-modulation approach to heating control. By way of example, a pulse-width modulation scheme may be provided at a frequency of the order of 100 Hz, where each period is divided into a heating portion (of variable length) and a measurement portion. 
       FIG. 23  is a flow chart, indicated generally by the reference numeral  410 , showing an algorithm in accordance with an example embodiment. The algorithm  410  may be implemented using the system  200  described above. 
     The algorithm  410  starts at operation  411 , where an impulse is applied to the resonant circuit  14  by the switching circuit  13  (e.g. the circuit  40 ). At operation  413 , an impulse response (e.g. detected using the impulse response processor  204 ) is used to determine whether an article (such as the article  21 ) is present in the system to be heated. As discussed above, the presence of the article  21  affects the impulse response in a manner that can be detected. 
     If an article is detected at operation  413 , the algorithm  410  moves to operation  415 ; otherwise, the algorithm terminates at operation  419 . 
     At operation  415 , measurement and heating operations are implemented. By way of example, the operation  415  may be implemented using the algorithm  400  described above. Of course, alternative measurement and heating arrangements could be provided. 
     Once a number of heating measurement and heating cycles have been conducted, the algorithm  400  moves to operation  417 , where it is determined whether heating should be stopped (e.g. if a heating period has expired, or in response to a user input). If so, the algorithm terminates at operation  419 ; otherwise the algorithm  400  returns to operation  411 . 
     It should be appreciated that the above techniques for determining one or more properties of the inductive arrangement or susceptor arrangement can be applied to individual inductive elements. For systems that comprise multiple inductive elements, such as the system  20 , which comprises three inductive elements  23   a ,  23   b , and  23   c , the system may be configured such that the one or more parameters, such as the temperature, can be determined for each of the inductive elements using the above described techniques. In some implementations, it may be beneficial for the system to operate using separate measurements for each of the inductive elements. In other implementations, it may be beneficial for the system to operate using only a single measurement for the plurality of inductive elements (e.g., in the case of determining whether the article  21  is present or not). In such situations, the system may be configured to determine an average measurement corresponding to the measurements obtained from each inductive element. In other instances, only one of the plurality of inductive elements may be used to determine the one or more properties. 
     The various embodiments described herein are presented only to assist in understanding and teaching the claimed features. These embodiments are provided as a representative sample of embodiments only, and are not exhaustive and/or exclusive. It is to be understood that advantages, embodiments, examples, functions, features, structures, and/or other aspects described herein are not to be considered limitations on the scope of the invention as defined by the claims or limitations on equivalents to the claims, and that other embodiments may be utilized and modifications may be made without departing from the scope of the claimed invention. Various embodiments of the invention may suitably comprise, consist of, or consist essentially of, appropriate combinations of the disclosed elements, components, features, parts, steps, means, etc, other than those specifically described herein. In addition, this disclosure may include other inventions not presently claimed, but which may be claimed in future.