Patent Publication Number: US-2018034327-A1

Title: Wireless power transfer adaptor

Description:
FIELD OF THE INVENTION 
     The present invention is in the field of wireless or inductive power transfer. More particularly, but not exclusively, the present invention is directed to systems and methods for inductive power transfer for consumer electronic devices. 
     BACKGROUND OF THE INVENTION 
     IPT technology is an area of increasing development and IPT systems are now utilised in a range of applications and with various configurations. One such application is the use of IPT systems in so called ‘charging mats’ or pads. Such charging mats will normally provide a planar charging surface onto which portable electronic devices (such as smartphones) may be placed to be charged or powered wirelessly. 
     Typically, the charging mat will include a transmitter having one or more power transmission coils arranged parallel to the planar charging surface of the charging mat. The transmitter drives the transmitting coils so that the transmitting coils generate a time-varying magnetic field in the immediate vicinity of the planar surface. When portable electronic devices are placed on or near the near the planar surface, the time-varying magnetic field will induce an alternating current in the receiving coil of a suitable receiver associated with the device (for example a receiver incorporated into the device itself). The received power may then be used to charge a battery, or power the device or some other load. 
     A problem associated with charging mat design is ensuring that the inductive power transfer is adequately efficient for different orientations of receiving coils. That is, for planar or flat devices, such as smartphones, the receiving coil associated with the device will typically be placed in a parallel plane to the transmitting coil(s) by being placed on the interface surface of the charging mat such that coupling is maximised and therefore power transfer is reasonably efficient. However, for non-planar or arbitrarily shaped devices, such as wearable devices, the receiving coil(s) associated with the device may be placed at a arbitrary angle or orientation relative to the transmitting coil(s) of the charging mat because the device itself may not sit flat on the interface surface of the charging mat. This situation may also occur for planar devices if a user wishes to orient the device for ease of use during charging/powering, e.g., the user props the device at an angle to the interface surface so that a screen of the device can be interacted with. Thus, without requiring device designers to provide ‘flat’ exterior surfaces for the coupling with the receiving coils or forcing users to not deviate from a co-planar orientation of their device, the efficiency of wireless power transfer may be significantly deteriorated, thereby limiting the applicable uses of charging mats. 
     Another problem associated with charging mat design is enabling multiple devices to be charged simultaneously in an efficient and cost effective manner. Some conventional designs use a single large transmitting coil corresponding to the entire surface of the charging mat. In this instance, one or more devices may be placed anywhere on the surface of the charging mat. This allows more freedom in terms of where a user may place a device on the charging mat. However, the magnetic field produced by a large transmitting coil may not be uniform, with ‘weak spots’ towards the centre of the charging mat, and the problems with arbitrary receiving coil orientation are not ameliorated. Further, since the entire surface is being ‘powered’ it is possible that any portions of the surface not covered by a device being charged may be a safety hazard. 
     Another conventional approach for multi-device charging is to have an array of transmitting coils. In order to provide efficient and safe power transfer, the charging mat detects the position of the devices using a suitable detection mechanism and activates the most proximate transmitting coil or coils. Though this allows more freedom in terms of where a user may place a device, like the single coil design, the boundary between adjacent transmitting coils can result in weak spots due to the cancelling effects of adjacent coils whereby receivers do not receiver sufficient power, and the problems with arbitrary receiving coil orientation are not ameliorated. 
     The invention provides an inductive power transfer system and methods that achieve reliable and efficient wireless power transfer for arbitrarily placed and orientated device powering or at least provides the public with a useful choice. 
     SUMMARY OF THE INVENTION 
     According to one exemplary embodiment there is provided a wireless power transfer system comprising:
         a wireless power transfer transmitter having at least one power transmitting coil aligned in a first plane;   a wireless power transfer receiver having at least one power receiving coil aligned in a second plane, the first and second planes being non-parallel to one another; and   a wireless power transfer adaptor for adapting the power transferred in the first plane to power transferred in the second plane.       

     It is acknowledged that the terms “comprise”, “comprises” and “comprising” may, under varying jurisdictions, be attributed with either an exclusive or an inclusive meaning. For the purpose of this specification, and unless otherwise noted, these terms are intended to have an inclusive meaning, i.e., they will be taken to mean an inclusion of the listed components which the use directly references, and possibly also of other non-specified components or elements. 
     Reference to any prior art in this specification does not constitute an admission that such prior art forms part of the common general knowledge. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings which are incorporated in and constitute part of the specification, illustrate embodiments of the invention and, together with the general description of the invention given above, and the detailed description of embodiments given below, serve to explain the principles of the invention. 
         FIG. 1  is a block diagram of a wireless power transfer system; 
         FIG. 2  illustrates an example application of the wireless power transfer system with a power transfer adaptor; 
         FIG. 3  illustrates another example application of the wireless power transfer system with example configurations of the power transfer adaptor; 
         FIGS. 4A and 4B  are isolated views of one example configuration of the power transfer adaptor; 
         FIG. 5  is a block diagram of a wireless power transfer system having the wireless power transfer adaptor; 
         FIG. 6  is a conceptual view of the internal components of the wireless power transfer adaptor; 
         FIG. 7  is an isolated view of another example configuration of the power transfer adaptor; 
         FIGS. 8A-8C  are isolated views of another example configuration of the power transfer adaptor; 
         FIGS. 9A and 9B  are conceptual views of example configurations of internal components of the wireless power transfer adaptor; 
         FIGS. 10A-10G  are a number of exemplary body geometries for a wireless power transfer adapter; 
         FIG. 11  illustrates an example application of a wireless power transfer system according to a further example configuration; 
         FIG. 12  is an isolated view of the further example configuration of the power transfer adaptor; 
         FIG. 13  is also an isolated view of the further example configuration of the power transfer adaptor; 
         FIG. 14  is conceptual view of the internal components of a further example configuration of the power transfer adaptor; 
         FIG. 15  is a side view of the wireless power transfer system according to a further example configuration; 
         FIG. 16  is conceptual view of the internal components of a yet further example configuration of the power transfer adaptor; 
         FIG. 17  illustrates an example application of the wireless power transfer system according to a yet further example configuration; 
         FIG. 18  illustrates another example application of the wireless power transfer system according to a yet further example configuration; 
         FIG. 19  illustrates a further example application of the wireless power transfer system according to a yet further example configuration; and 
         FIG. 20  illustrates a yet further example application of the wireless power transfer system according to a yet further example configuration. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION 
     An inductive power transfer (IPT) system  1  is shown generally in  FIG. 1 . The IPT system includes an inductive power transmitter  2  and an inductive power receiver  3 . The inductive power transmitter  2  is connected to an appropriate power supply  4  (such as mains power or a battery). The inductive power transmitter  2  in the form of a charging mat as described in the background may include transmitter circuitry having one or more of a converter  5 , e.g., an AC-DC converter (depending on the type of power supply used) and an inverter  6 , e.g., connected to the converter  5  (if present). The inverter  6  supplies a transmitting coil or coils  7  with an AC signal so that the transmitting coil or coils  7  generate an alternating magnetic field. In some configurations, the transmitting coil or coils  7  may be separate from the inverter  6 . The transmitting coil or coils  7  may be connected to capacitors (not shown) either in parallel or series to create a resonant circuit. 
     A controller  8  is provided to control operation of the inductive power transmitter  2  and may be directly or indirectly connected to several or all parts of the transmitter  2 . The controller  8  receives inputs from the various operational components of the inductive power transmitter  2  and produces outputs that control that operation. The controller  8  may be implemented as a single unit or separate units, configured to control various aspects of the inductive power transmitter  2  depending on its capabilities, including for example: power flow, tuning, selectively energising transmitting coil or coils  7 , inductive power receiver detection and/or communications. Whilst the transmitter is depicted as a charging mat or device, other configurations are possible in the scope of the present invention, such as a transmitter integrated into the surfaces of non-device objects, such as bench tops or desk tops of furniture, and the interiors of motor vehicles. 
     The inductive power receiver  3  includes a power pick-up stage  9  connected to power conditioning circuitry  10  that in turn supplies power to a load  11 . The load may be an electrically operational part of an electronic device or machine, or may be one or more power storage elements. The power pick-up stage  9  includes an inductive power receiving coil or coils. When the coil(s) of the inductive power transmitter  2  and the inductive power receiver  3  are suitably coupled, the alternating magnetic field generated by the transmitting coil or coils  7  induces an alternating current in the receiving coil or coils. The receiving coil or coils may be connected to capacitors and additional inductors (not shown) either in parallel, series or some other combination, such as inductor-capacitor-inductor, to create a resonant circuit. In some inductive power receivers, the receiver may include a controller  12  which may control tuning of the receiving coil or coils, operation of the power conditioning circuitry  10 , characteristics of the load  11  and/or communications. 
     The term “coil” may include an electrically conductive structure where an electrical current generates a magnetic field. For example inductive “coils” may be electrically conductive wire in three dimensional shapes or two dimensional planar shapes, electrically conductive material fabricated using printed circuit board (PCB) techniques into three dimensional shapes over plural PCB ‘layers’, and other coil-like shapes. Other configurations may be used depending on the application. The use of the term “coil”, in either singular or plural, is not meant to be restrictive in this sense. 
     Current induced in the power pick-up stage  9  by transmitting coil or coils  7  will typically be high frequency AC at the frequency of operation of the transmitting coil or coils  7 , which may be for example, 20 kHz, up to hundreds of megahertz or higher. The power conditioning circuitry  10  is configured to convert the induced current into a form that is appropriate for powering or charging the load  11 , and may perform for example power rectification, power regulation, or a combination of both. 
       FIGS. 2 and 3  illustrate depictions of example applications of an IPT system according to the present invention. In these applications the power transmitter  2  is provided as a charging pad or mat  200  having one or more transmitting coils  7  arranged in a plane parallel to an interface surface  202  of the mat  200  onto which one or more power receiver devices  3  can be placed. In the example of  FIG. 2 , two receiver devices  3  are to be powered/charged by the transmitter mat  200 , where one device is consumer electronic device  204 , depicted as a smartphone, which has circuitry of the power receiver  3  integrated therewith or connected in some other way, e.g., via an “after-market” cover or device. The receiving coil(s)  9  of the device  204  are generally positioned so that they are in a parallel plane with the transmitting coil(s) in the orientation depicted in  FIG. 2 . The other receiver device is an arbitrary consumer electronic device  206 , depicted as a wearable device or smartwatch, which has circuitry of the power receiver  3  integrated therewith such that the receiving coil(s)  9  of the device  206  are generally positioned so that they may not be in a parallel plane with the transmitting coil(s) if placed directly on the interface surface  202 . 
     In order to ensure maximum power transfer efficiency to the arbitrary receiver device  206  the present invention further provides a power transfer adaptor  208  which functions to reorient the power transferring field of the power transmitter for full receipt by the receiver circuitry of the device  206 . In  FIG. 2 , the power transfer adaptor  208  is depicted as a ‘stand’ for the wearable device  206 .  FIG. 3  depicts multiple examples of possible configurations of the stand  208  holding or supporting the wearable device  206 , which are discussed in more detail later. The actual configuration, e.g., the exterior shape, dimensions and aspect of the adaptor unit  208  is not limited to this however, and depends on the type of receiver device to which power transfer is to be adapted. Some further examples of these applications are discussed in more detail later. 
       FIGS. 4A and 4B  illustrate one of the example adaptor units  208  supporting the wearable device  206  and in isolation. As can be seen the general curved shape of the unit  208  is configured so that a strap  210  of the wearable device  206  is received over a neck portion  212  of the unit  208  so as to be supported against a body portion  214 . The interior of the adaptor unit  208  houses wireless power transfer transceiver electronics for receiving power transferred from the transmitter  2  and transferring that received power to the receiver  3 . 
     Example transceiver electronics  500  of the adaptor unit  208  are depicted in block diagram form in  FIG. 5  relative the block diagram forms of the transmitter  2  and receiver  3  depicted for the IPT system  1  in  FIG. 1 . The adaptor electronics  500  includes a power pick-up stage  502  and a power transmitting stage  504  connected to one another via a connection stage  506 . The power pick-up stage  502  includes one or more inductive power receiving coils. When the coil(s) of the inductive power transmitter  2  and receiving coil(s) the adaptor unit  208  are suitably coupled, the alternating magnetic field generated by the transmitting coil(s)  7  induces an alternating current in the receiving coil(s) of the adaptor unit  208 . The receiving coil(s) may be connected to capacitors and additional inductors (not shown) either in parallel, series or some other combination, such as inductor-capacitor-inductor, to create a resonant circuit. The connection stage  506  may include power conditioning and/or control circuitry for conditioning the power received from the power transmitter and/or controlling tuning of the receiving coil(s), operation of the power conditioning circuitry and/or communications. 
     The power received by the power pick-up stage  502  is transferred to the power transmitting stage  504  via the connection stage  506 . This power is supplied to one or more transmitting coils of the power transmitting stage  504 , and as the power received by the power pick-up stage  502  represents an AC signal, this AC signal is conveyed to the transmitting coil(s) thereby generating an alternating magnetic field so that when the coil(s) of the inductive power receiver  3  and the transmitting coil(s) of the adaptor unit  208  are suitably coupled, the alternating magnetic field generated by the transmitting coil(s) induces an alternating current in the receiving coil(s) of the receiver  3 . The transmitting coil(s) may be connected to capacitors and additional inductors (not shown) either in parallel, series or some other combination, such as inductor-capacitor-inductor, to create a resonant circuit. The connection stage  506  may include power conditioning and/or control circuitry for conditioning the power conveyed to transmitting coil(s) of the adaptor unit and/or controlling tuning of the transmitting coil(s), operation of the power conditioning circuitry and/or communications. 
     In the simplest form, the connection stage  506  is merely a conductive path between the receiving coil(s) and transmitting coil(s), so that minimal power is lost. This is depicted in conceptual form in  FIG. 6 . In  FIG. 6 , the exterior body of the adaptor unit  208  is shown in transparent form to reveal the transceiver electronics  500  within the unit  208 . The power pick-up stage  502  is depicted as a single receiver coil  600  and the power transmitting stage  504  is depicted as a single transmitter coil  602 . The coils are connected to one another via a single conductive wire  604  of the connection stage  506 . As can be seen the transmitting coil  602  is orientated at a non-co-planar angle to the receiving coil  600 . In the example of  FIG. 6  the transmitting coil  602  is substantially orthogonal to the receiving coil  600 . In this way, when the adaptor unit  208  is placed on the interface surface of the transmitter  2 , the receiving coil  600  located at a base portion  216  of the unit  208  will be in a parallel plane with one or more transmitting coils  7  of the transmitter  2  thereby allowing maximum coupling (i.e., because there is maximum interaction with the magnetic field of the transmitting coils  7  of the transmitter  2  by the receiving coil  600  such that maximum magnetic flux is induced). On the other hand, when the wearable device  206  is placed on the adaptor unit  208  in a manner like that depicted in  FIG. 4A , for example, the transmitting coil  602  located in the neck portion  212  of the unit  208  will be in a parallel plane with receiving coil(s)  9  of the receiver  3  thereby allowing maximum coupling (i.e., because there is maximum interaction with the magnetic field of the transmitting coils  602  by the receiving coil(s)  9  such that maximum magnetic flux is induced). 
     The adaptor receiving and transmitting coils depicted in conceptual form herein, are generally comprised of a spirally wound coil of conductive material on a supporting plate of magnetically permeable material, such as a ferrite. However, as described earlier other ‘coil’ configurations are possible. The magnetically permeable material enhances the coupling of the adaptor coils to the external coils of the transmitter and receiver devices. The magnetically permeable material is further positioned within the adaptor unit so that the adaptor receiving and transmitting coils are suitably decoupled from one another, thereby ensuring no interference between the coils. The adaptor coils may be similarly shielded from other electronics within the adaptor unit and or the external environment. 
     In the example depicted in  FIG. 6 , where a single planar transmitting coil  602  is provided in the adaptor unit  208 , it is necessary for the wearable device  206  to be positioned so that its receiving coil(s) is properly aligned with the transmitting coil of the adaptor unit to allow maximum power transfer. This could be done by provided suitable marking on the adaptor unit to designate the location of the coil. Alternatively, the neck portion  212  can be configured to allow inherent alignment. This is depicted in  FIG. 7 , where a ‘flat’ facet  700  is provided on the neck portion  212  onto which a ‘flat’ surface of the wearable device aligned with the receiving coil thereof nests, as illustrated in  FIG. 3 . 
       FIGS. 8A to 8C  illustrate another example configuration of the adaptor  208  for providing ease for a user in correctly positioning the wearable device  206 . In this example configuration, as illustrated in  FIG. 8B , the flat facet  700  is provided at an angle to the base  216  of the unit  208  and the body portion  214  has a seat portion  218  configured to receive an watch segment of the smartwatch  206  depicted which has a receiving coil therein. This arrangement ensures that a user positions the smartwatch for maximum power transfer efficiency. Due to the non-orthogonal orientation of the facet or adaptor interface surface  700 , the adaptor transmitting coil  602  is similarly arranged to be non-orthogonally aligned, but angled, to the base  216  (and the adaptor receiving coil  600 ), so that the adaptor transmitting coil is in a parallel plane to the adaptor interface surface, as illustrated in  FIG. 8C . With this angled configuration of the adaptor unit which provides an angled relative orientation of the charging mat and the receiving coils of the receiver device, not only wearable devices can be supported in this relationship, but other devices as well, such as smartphones, such that interaction with the receiver device by users during powering/charging via the adaptor can be easily enabled. 
     Further ease for a user however can be provided by configuring the transceiver electronics of the adaptor unit  208  so that multiple power transmission planes are provided. To this end,  FIGS. 9A and 9B  depict example configurations of the adaptor electronics  500  having multiple transmitting coils  602 . In  FIG. 9A , two transmitting coils  602  are arranged orthogonal to one another such that two magnetic fields (or actually four magnetic fields) are induced  90  radian degrees out of phase with one another, such that the magnetic fields due not interfere with one other through cross-coupling of the coils. In  FIG. 9B , three transmitting coils are arranged about the neck portion  212  such that three magnetic fields are induced, with cross-coupling avoided by arranging ferrite material behind each coils with respect to the interior of the neck portion. These arrangements provide a power transfer field having a larger range than the single planar coil example thereby be providing substantially free placement of the receiver device. 
     In the multiple transmitting coil embodiments of the adaptor unit, the plural transmitting coils may be simultaneously operated through constant connection to the adaptor receiving coil(s) via the connection stage, or operation may be selective. Selective operation may be provided by suitable switching control in the electronics of the connection stage  506  so that only selected adaptor transmitting coils are connected to the adaptor receiving coil at any time. This selection could be controlled using a suitable controller, such as a digital controller in the form of a programmable integrated circuit, e.g., a microcontroller, or as an analog controller in the form of discrete circuit components. 
     Selection of the adaptor transmitting coil or coils required to transfer power to a proximate receiver device could be governed by suitable detection of the proximity of the receiver device. This can be achieved, for example, using suitable sensors or detection techniques within the adaptor electronics. As one example, the Applicant has found that receiver devices which generally include ferrite in conjunction with the receiving coils provide reflected impedance characteristics which are different to objects having metal only, e.g., little or no magnetically permeable material. This situation can therefore be used to detect the presence of a receiver object, and power transfer can be established based on this or on further detection techniques, such as analogue or digital communications with applicably capable receiver devices. Indeed, depending of the type of charging mat that the adaptor unit is placed upon, the presence of the adaptor unit itself can be ascertained by the power transmitter using a similar technique, since the adaptor unit has ferrite associated with the base coil  600 . Further, in IPT systems in which communications between transmitter and receiver devices is implemented using the IPT field itself, e.g., through amplitude, frequency and/or phase modulation of the IPT field, such communication can be carried out through the transceiver network of the adaptor unit. Further, the transceiver electronics of the adaptor itself can be provided with suitable modulation/demodulation circuitry to allow independent communications with the transmitter and receiver devices, thus allowing establishment of ‘power contracts’ between the adaptor and power transmitter and/or between the adaptor and the power receiver. 
       FIGS. 10 a  to 10 g    show a number of exemplary body geometries for a wireless power transfer system utilising flat surfaces having coils adjacent a plurality or each flat surface. Possible geometries include a triangular based pyramid ( FIG. 10 a   ), a frusto triangular based pyramid ( FIG. 10 b   ), a cube ( FIG. 10 c   ), a triangular prism ( FIG. 10 d   ), a square based pyramid ( FIG. 10 e   ), a frusto square based pyramid ( FIG. 10 f   ) or articulated planar sections ( FIG. 10 g   ). Flat surfaces have the advantage that they closely conform to planar interface surfaces of devices to be charged as well as the charging pad. This also allows wireless power transfer systems to be stacked for geometries such as a cube. 
     In some embodiments one or more coil may be dedicated receive coils and one or more coils may be dedicated transmit coils. In a preferred embodiment each flat face may have an associated coil proximate the face that may be dynamically configured to be a receive or a transmit coil based on monitoring of the coils by a wireless power transfer adaptor of the wireless power transfer system. The wireless power transfer adaptor may monitor the coils and upon detecting a coil receiving power may configure that coil to be a power receiving coil. The wireless power transfer adaptor may then monitor the other coils to determine if there is a device proximate one of the other coils demanding power and configure that coil as a power transmitting coil. The transmitter coil configuration may also be performed based on communication between the wireless power transfer adaptor and a device to be charged. 
     Referring to  FIGS. 11 to 14  a wireless power transfer system  700  having a frustopyrimidal body is shown. In this case the base  705  has a dedicated receiver coil  710  located adjacent base  705  and four transmit coils  706  to  709  located adjacent flat side faces  711  to  714 . The flat base may be positioned adjacent the surface of charging pad  701  for good coupling. 
     As shown in  FIG. 12  a device such as a tablet  702  may be positioned in an inclined manner against wireless power transfer system  700  so that it is well oriented for a user to use the device during charging as well as to position a transmitter coil of the wireless power transfer system  700  optimally with respect to the flat face of tablet  702 . 
     As shown in  FIG. 13  a watch  703  may be simply placed on wireless power transfer system  700  and the flat back of the watch will automatically position itself against a flat face of wireless power transfer system  700  to provide good coupling between the transmit coil of wireless power transfer system  700  and the receive coil of watch  703 . The tapering shape also ensures that a watch will be easily placed and retained in the correct position on wireless power transfer system  700 . 
       FIG. 15  shows a modified version in which wireless power transfer system  700  includes feet  715  to retain the bottom edge of tablet  702 . 
       FIGS. 16 to 19  show an embodiment in which the wireless power transfer system  800  is in the form of a cube. As shown in  FIG. 15  an inner cube  801  has coils  802  to  804  mounted to each face (as well as three more coils on the faces not visible). A wireless power transfer adaptor is located within inner cube  801  and is electrically connected to all coils. In this embodiment the coils are configurable to be transmit or receive coils as will be explained. The outer casing is formed by two halves  805  and  806  that join to encase the other components. 
     As shown in  FIG. 17  a wireless power transfer system in the form of a cube  800  may be placed on a charging pad  807 . The wireless power transfer adaptor within the cube detects power being received by the coil proximate the surface of the charging pad and configures it as a receiver coil. Watch  808  is then placed about the cube and the wireless power transfer adaptor detects that one of the other coils is proximate a device demanding power an configures that coil as a transmit coil. Alternatively the transmit coil could be configured as a result of communication—for example communication via the coil proximate the watch. 
     As shown in  FIGS. 18 and 19  a tablet  809  may also be placed against the cube  800  to charge in a similar way. Coupling may be less optimal than for the embodiment of  FIGS. 11 to 14  as the tablet is more inclined but the arrangement has advantages in terms of modularity as will be described below. 
       FIG. 20  illustrates how multiple cubes  900  may be employed as a modular repeater. In this case a first cube  917  is stacked upon a second cube  916  upon a charging pad  901 . In this case wireless power transfer adaptor  919  configures coil  918  as the receive coil and coil  920  as the transmit coil and wireless power transfer adaptor  922  configures coil  921  as a receive coil and coil  923  as a transmit coil. This forms a two stage repeater from charging pad  901  to tablet  902 . This may desirable depending upon the size of the device and position of the power receiving coil of the device to be charged. It will be appreciated that the cubes may be mechanically or magnetically locked together and/or provided with non-slide surfaces so as to provide a suitable support for a device. 
     In the afore-described example configurations of the wireless power transfer adaptor, the ‘body’ of the adaptor unit is rigid or static, meaning that the possible relative orientations of the interface surface of the transmitter and the receiver device are set. However, in a further example configuration of the adaptor unit, the body may be at least partly formed of a mouldable and conformable material. In this way, the adaptor body can be moulded and remoulded depending on application where the adaptor electronics within is flexible through, for example, a flexible connection stage  506 . The mouldable material may be any suitable material that can be moulded to retain the moulded shape thereby providing structure for the desired form for the adaptor unit without interfering with operation of the encased electronics or with the inductive magnetic fields used by the system. Such material may be, for example, gel, polymer, clay or bendable plastic. The adaptor electronics may be embedded within the mouldable material, for example, by pouring or shaping the material about the electronics, or by having the material press- or snap-fitted about the internal components, which are held in place by the mouldable material itself or by adhesive or the like. 
     Whilst the present invention has been illustrated by the description of the embodiments thereof, and while the embodiments have been described in detail, it is not the intention to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details, representative apparatus and method, and illustrative examples shown and described. Accordingly, departures may be made from such details without departure from the spirit or scope of the general inventive concept.