`
`(12) UK Patent Application .. GB 2399 225 ..A
`
`
`
`(43) Date of A Publication 08.09.2004
`
`(21) Application No:
`
`(22) Date of Filing:
`
`Date Lodged:
`
`(30) Priority Data:
`(31) 0210886
`(31) 0213024
`(31) 0225006
`(31) 0228425
`
`0409705.1
`
`13.05.2003
`
`30.04.2004
`
`(33) GB
`
`(32) 13.05.2002
`(32) 07.06.2002
`(32) 28.10.2002
`(32) 06.12.2002
`
`(62) Divided from Application No
`0310956.8 under Section 15(4) of the Patents Act 1977
`
`(71) Applicant(s):
`Splashpower Limited
`(Incorporated in the United Kingdom)
`St John’s Innovation Centre,
`Cowley Road, CAMBRIDGE, CB4 OWS,
`United Kingdom
`
`(61)
`
`INT CL’:
`HO1F 38/14 // HO2J 7/02 , HO4B 5/00
`
`(52) UK CL(Edition W ):
`H1T T1C T1F 112 T6 T7A11 T7A13 T7A2A T7A2B T7A5
`TICIA T7C5
`
`US 6100663 A
`
`(56) DocumentsCited:
`SE 008704910 A
`US 3673334 A
`
`(58) Field of Search:
`UK CL [Edition W ) H1T
`INT CL’ HO1F, H02J, H04B
`Other:
`
`(continued on next page)
`
`
`(54) Abstract Title: Inductive power transfer system having a horizontal magneticfield
`
`(57) Aprimary unit for use in a powertransfer system has a powertransfer surface shaped and arranged such
`that a secondary device 820, separable from the primary unit, can be placed in a working disposition on or
`in proximity to a power transfer area of the surface to receive powerfrom the primary unit without
`requiring direct electrical conductive contacts between the primary unit and the secondary device. The
`primary unit comprises a field generating unit having a plurality of substantially coplanar conductive
`elements 711 arranged at or beneath the power transfer surface in a generating area. The elements
`extend generally in parallel with one another across the generating area, and generate an
`electromagnetic field 1 distributed across the power transfer area. The respective instantaneous currents
`which flow simultaneously through all the conductive elements in the generating area have the same
`general direction.
`
`
`
`Figure 4d
`
`Original Printed on Recycled Paper
`
`VSc66E2AD
`
`1
`
`Exhibit 2001
`Momentum Dynamicsv. Witricity
`IPR2021-01116
`
`1
`
`Exhibit 2001
`Momentum Dynamics v. Witricity
`IPR2021-01116
`
`

`

`GB 2399225 A continuation
`
`(72)
`
`(74)
`
`Inventor(s):
`Lily Ka-lai Cheng
`James Westwood Hay
`Pilgrim Giles William Beart
`
`Agent and/or Address for Service:
`Haseltine Lake & Co
`Imperial House, 15-19 Kingsway,
`LONDON, WC2B 6UD,United Kingdom
`
`2
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`

`

`2399225
`
`INDUCTIVE POWER TRANSFER SYSTEM HAVING HORIZONTAL
`
`
`FIELD
`
`This invention relates to a new apparatus and method for transferring power in a
`
`contact-less fashion.
`
`Manyof today’s portable devices incorporate “secondary” powercells which can be
`recharged, saving the user the cost and inconvenience of regularly having to purchase
`new cells. Example devices include cellular telephones, laptop computers, the Paim
`500 series of Personal Digital Assistants, electric shavers and electric toothbrushes.
`In some ofthese devices, the cells are recharged via inductive coupling rather than
`direct electrical connection. Examples include the Braun Oral B Plak Control power
`toothbrush,
`the Panasonic Digital Cordless Phone Solution KX-PHI5AL and the
`Panasonic multi-head men’s shavers ES70/40series.
`
`Each ofthese devices typically has an adaptor or charger which takes power from
`mainselectricity, a car cigarette lighter or other sources of power and converts it into
`a form suitable for charging the secondary cells. There are a number of problems
`associated with conventional means of powering or charging these devices:
`
`20
`
`25
`
`30
`
`e Both the characteristics of the cells within each device and the means of
`connecting to them vary considerably from manufacturer to manufacturer,
`and from device to device. Therefore users who own several such devices
`must also own several different adaptors.
`If users are going away ontravel,
`they will have to bring their collection of chargers if they expect to use their
`devices during this time.
`
`e These adaptors and chargers often require uscrs to plug a small connector into
`the device or to place the device with accurate alignmentinto a stand causing
`inconvenience. If users fail to plug or place their device into a charger and it
`runs out of power, the device becomes useless and important data stored
`locally in the device might even belost.
`
`27
`
`27
`
`

`

`©
`
`In addition, most adaptors and chargers have to be plugged into mains sockets
`and hence if several are used together, they take up space in plug strips and
`
`create a messy and confusing tangle of wires.
`
`e Besides the above problems with conventional methods of recharging
`devices, there are also practical problems associated with devices having an
`open electrical contact.
`For example, devices cannot be used in wet
`environments dueto the possibility of corroding or shorting out the contacts
`and also they cannot be used in flammable gascous environments due to the
`possibility of creating electrical sparks.
`
`Chargers which use inductive charging remove the need to have open electrical
`contacts hence allowing the adaptor and device to be sealed and used in wet
`environments (for example the electric toothbrush as mentioned above is designed to
`be used in a bathroom). Howeversuch chargersstill suffer from all other problems
`as described above. For example, the devicesstill need to be placed accurately into a
`charger such that the device and the chargerare in a predefined relative position (See
`Figures 1a and 1b). The adaptorsare still only designed specifically for a certain
`make and model of device andarestill only capable of charging one device ata time.
`Asaresult, users still need to possess and managea collection ofdifferent adaptors.
`
`Universal chargers (such as the Maha MH-C777 Plus Universal charger) also exist
`such that battery packs of different shapes and characteristics can be removed from
`the device and charged using a single device. Whilst these universal chargers
`eliminate the need for having different chargers for different devices, they create
`even more inconveniencefor the userin the sense that the battery packs first need to
`be removed, then the charger needs to be adjusted and the battery pack needs to be
`accurately positionedin or relative to the charger.
`In addition, time must be spent to
`determine the correct pair ofbattery pack metal contacts which the charger must use.
`
`It is known from US 3,938,018 “Induction charging system” to provide a means for
`non-contact battery charging whereby an inductive coil on the primary side aligns
`
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`

`

`with a horizontal inductive coil on a secondary device whenthe device is placed into
`a cavity on the primary side. The cavity ensures the relatively precise alignment
`which is necessary with this design to ensure that good coupling is achieved between
`
`the primary and secondary coils.
`
`It is also known from US 5,959,433 “Universal Inductive Battery Charger System”
`to provide a non-contact battery charging system. The battery charger described
`includes a single charging coil which creates magnetic flux lines which will induce
`an electrical current in a battery pack which may belong to cellular phones or laptop
`
`10
`
`computers.
`
`It is also known from US 4,873,677 “Charging Apparatus for an Electronic Device”
`to provide an apparatus for charging an electronic device which includes a pair of
`coils. This pair of coils is designed to operate in anti-phase such that magnetic flux
`lines are coupled from one coil to the other. An electronic device such as a watch
`can be placed onthese two coils to receive power.
`
`It is also known from US 5,952,814 “Induction charging apparatus and an electronic
`device” to provide an induction charger for charging a rechargeable battery. The
`shapeof the external casing of the electronic device matches the internal shape ofthe
`chargerthus allowing for accurate alignmentof the primary and secondary coils.
`
`[t is also known from US 6,208,115 “Battery substitute pack” to provide a substitute
`battery pack which maybeinductively recharged.
`
`It is known from WO 00/61400 “Device for Inductively Transmitting Electrical
`Power” to provide a meansoftransferring powerinductively to conveyors.
`
`15
`
`20
`
`25
`
`It is known from WO 95/11545 “Inductive power pick-up coils” to provide a system
`for inductive powering ofelectric vehicles from a series ofin-road flat primaries.
`
`30
`
`29
`
`29
`
`

`

`To overcome the limitations of inductive power transfer systems which require that
`secondary devices be axially aligned with the primary unit, one might propose that
`an obvioussolution is to use a simple inductive powertransfer system whereby the
`primary unit is capable of emitting an electromagnetic field over a large area (See
`Figure 2a). Users can simply place one or more devices to be recharged within range
`of the primary unit, with no requirementto place them accurately. For example this
`primary unit may consist of a coil encircling a large area. When a current flows
`through the coil, an electromagnetic field extending overa large area is created and
`devices can be placed anywhere within this area. Although theoretically feasible,
`this method suffers
`from a number of drawbacks.
`Firstly,
`the intensity of
`electromagnetic emissions is governed by regulatory limits. This means that this
`method can only support powertransferat a limited rate.
`In addition, there are many
`objects that can be affected by the presence of an intense magnetic field. For
`example, data stored on credit cards maybe destroyed andobjects made of metal will
`have induced therein eddy currents generating undesired heating effects. In addition,
`if a secondary device comprising a conventional coil (see Figure 2a) is placed against
`a metallic plate such as a copperplanein a printed circuit board or metallic can of a
`cell, coupling is likely to be significantly reduced.
`
`Toavoid the generation oflarge magnetic fields, one might suggest using an array of
`coils (See Figure 3) whereby only the coils needed are activated. This method is
`described in a paper published in the Journal of the Magnetics Society of Japan titled
`“Coil Shape in a Desk-type Contactless Power Station System” (29" Nov 2001).
`In
`an embodiment of the multiple-coil concept, a sensing mechanism senses the relative
`location of the secondary device relative to the primary unit. A control system then
`activates the appropriate coils to deliver power to the secondary device in a localised
`fashion. Although this method provides a solution to the problemspreviously listed,
`it does so in a complicated and costly way. The degree to which the primary field
`can be localised is limited by the number ofcoils and hence the numberofdriving
`circuits used (i.e. the “resolution” ofthe primary unit). The cost associated with a
`multiple-coil system would severely limit
`the commercial applications of this
`concept. Non-uniform field distribution is also a drawback. Whenall the coils are
`
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`

`activated in the primary unit, they sum to an equivalentofa large coil, the magnetic
`field distribution of which is seen to exhibit a minimum at the centre of the coil.
`
`- Another scheme is outlined in US 5,519,262 “Near Field Power Coupling System”,
`whereby a primary unit has a number of narrow inductive coils (or alternatively
`capacitive plates) arranged from one end to the other of a flat plate, creating a
`number of vertical fields which are driven in a phase-shifted manner so that a
`sinusoidal wave ofactivity moves across the plate. A receiving device has two
`vertical field pickups arranged so that regardless of its position on the plate it can
`always collect power from at
`least one pickup. While this scheme also offers
`freedom of movementofthe device, it has the disadvantages of needing a complex
`secondary device, having a fixed resolution, and having poor coupling because the
`return flux path is throughair.
`
`Noneofthe prior art solutions can satisfactorily address all of the problems that have
`been described.
`It would be convenient to have a solution which is capable of
`transferring power to portable devices with all of the following features and is cost
`
`effective to implement:
`
`20
`
`25
`
`30
`
`a single primary unit which can supply power to different
`e Universality:
`secondary devices with different power requirements thereby eliminating the
`need for a collection of different adaptors and chargers;
`e Convenience:
`a single primary unit which allows secondary devices to be
`placed anywhere within an active vicinity thereby eliminating the need for
`plugging-in or placing secondary devices accurately relative to an adaptor or
`
`charger;
`e Multiple-load: a single primary unit that can supply power to a number of
`secondary different devices with different power requirements at the same
`
`time;
`e Flexibility for use in different environments: a single primary unit that can
`supply power to secondary devices such that no direct electrical contact is
`
`31
`
`31
`
`

`

`required thereby allowing for secondary devices and the primary unit itself to
`be used in wet, gaseous, clean and other atypical environments;
`© Low electromagnetic emissions:
`a primary unit that can deliver power in a
`manner that will minimize the intensity and size of the magnetic field
`
`generated.
`
`It is further to be appreciated that portable appliances are proliferating and theyall
`need batteries to power them. Primary cells, or batteries of them, must be disposed of
`once used, which is expensive and environmentally unfriendly. Secondary cells or
`batteries can be recharged and used again andagain.
`
`10
`
`Many portable devices have receptacles for cells of an industry-standard size and
`voltage, such as AA, AAA, C, D and PP3. This leaves the user free to choose
`whether to use primary or secondary cells, and of various types. Once depleted,
`secondary cells must typically be removed from the device and placed into a separate
`recharging unit. Alternatively, some portable devices do have recharging circuitry
`built-in, allowing cells to be recharged in-situ once the deviceis plugged-in to an
`
`external source of power.
`
`It is inconvenient for the user to have to either remove cells from the device for
`recharging,or to have to plug the device into an external power source for recharging
`in-situ. It would be far preferable to be able to recharge the cells without doing
`
`either, by some non-contact means.
`
`Some portable devices are capable of receiving power coupled inductively from a
`recharger, for example the Braun Oral B Plak Control toothbrush. Such portable
`devices typically have a custom, dedicated power-receiving module built-in to the
`device, which then interfaces with an internal standard cell or battery (which may or
`
`maynot be removable).
`
`However it would be convenient if the user could transform any portable device
`which accepts industry-standard cell sizes into an inductively-rechargeable device,
`
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`

`

`simply by fitting inductively-rechargeable cells or batteries, which could then be
`rechargedin-situ by placing the device onto an inductive recharger.
`
`Examplesofprior art include US 6,208,115, which discloses a substitute battery pack
`which maybe inductively recharged.
`
`According to a first aspect of the present invention, there is provided a system for
`transferring power without requiring direct electrical conductive contacts, the system
`
`comprising:
`
`a primary unit including a substantially laminar charging surface and at least
`1)
`one means for generating an electromagnetic field, the means being distributed in
`two dimensions across a predetermined areain or parallel to the charging surface so
`as to define at least one charging area of the charging surface that is substantially
`coextensive with the predetermined area, the charging area having a width and a
`length on the charging surface, wherein the meansis configured such that, when a
`predetermined current
`is supplied thereto and the primary unit
`is effectively in
`electromagnetic isolation, an electromagnetic field generated by the means has
`electromagnetic field lines that, when averaged over any quarter length part of the
`charging area measuredparallel to a direction ofthe field lines, subtend an angle of
`45° or less to the charging surface in proximity thereto and are distributed in two
`dimensions thereover, and wherein the means has a height measured substantially
`perpendicular to the charging area thatis less than either of the width or the length of
`the charging area; and
`
`il)
`
`at least one secondary device includingat least one electrical conductor;
`
`wherein, when the at least one secondary device is placed on or in proximity to a
`charging area of the primary unit, the electromagnetic field lines couple with the at
`least one conductorofthe at least one secondary device and induce a current to flow
`
`therein.
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`
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`
`

`

`According to a second aspect of the present invention, there is provided a primary
`unit for transferring power without requiring direct electrical conductive contacts, the
`primary unit including a substantially laminar charging surface and at
`least one
`means for generating an electromagnetic field, the means being distributed in two
`dimensions across a predeterminedarea in or parallel to the charging surface so as to
`define at
`least one charging area of the charging surface that
`is substantially
`coextensive with the predetermined area, the charging area having a width and a
`length on the charging surface, wherein the means is configured such that, when a
`predetermined current is supplied thereto and the primary unit
`is effectively in
`electromagnetic isolation, an electromagnetic field generated by the means has
`electromagnetic field lines that, when averaged over any quarter length part of the
`charging area measuredparallel to a direction of the field lines, subtend an angle of
`45° or less to the charging surface in proximity thereto and are distributed in two
`dimensions thereover, and wherein the means has a height measured substantially
`perpendicular to the charging areathatis less than either of the width or the length of
`the charging area.
`
`According to a third aspect of the present invention, there is provided a method of
`transferring power in a non-conductive manner from a primary unit to a secondary
`device, the primary unit including a substantially laminar charging surface and at
`least one meansfor generating an electromagnetic field, the means being distributed
`in two dimensions across a predetermined area in or parallel to the charging surface
`so as to define at least one charging area of the charging surface that is substantially
`coextensive with the predetermined area, the charging area having a width and a
`length on the charging surface, the means having a height measured substantially
`perpendicularto the charging areathatis less than either of the width or the length of
`the charging area, and the secondary device having at least one electrical conductor;
`wherein:
`
`an electromagnetic field, generated by the means when energised with a
`i)
`predetermined current and measured when the primary unit
`is effectively in
`electromagnetic isolation, has electromagnetic field lines that, when averaged over
`
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`34
`
`34
`
`

`

`any quarter length part of the charging area measuredparallel to a direction of the
`field lines, subtend an angle of 45° or less to the charging surface in proximity
`thereto and are distributed in two dimensions over the at least one charging area
`
`- when averaged thereover; and
`
`the electromagnetic field links with the conductor of the secondary device
`ii)
`whenthis is placed on or in proximity to the charging area.
`
`10
`
`According to a fourth aspect of the present invention, there is provided a secondary
`device for use with the system, unit or method ofthe first, second or third aspects,
`the secondary device including at
`least one electrical conductor and having a
`substantially laminar form factor.
`
`In the context of the present application, the word “laminar” detines a geometry in
`the form ofa thin sheet or lamina. The thin sheet or lamina may be substantially flat,
`
`or may be curved.
`
`The primary unit may include an integral power supply for the at least one means for
`generating an electromagnetic field, or may be provided with connectors or the like
`enabling the at least one meansto be connected to an external power supply.
`
`20
`
`In some embodiments, the means for generating the electromagnetic field have a
`height that is no more than half the width or half the length of the charging area; in
`some embodiments, the height may be no more than 1/5 of the width or 1/5 of the
`
`25
`
`length of the charging area.
`
`The at least one electrical conductor in the secondary device may be wound about a
`core that serves to concentrate flux therein.
`In particular, the core (where provided)
`may offer a path of least resistance to flux lines of the electromagnetic field
`generated by the primary unit. The core may be amorphous magnetically permeable
`material.
`In some embodiments, there is no need for an amorphouscore.
`
`30
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`35
`
`

`

`Where an amorphouscoreis provided,it is preferred that the amorphous magnetic
`material is a non-annealed or substantially as-cast state. The material maybe at least
`70% non-annealed, or preferably at
`least 90% non-annealed. This is because
`annealing tends
`to make
`amorphous magnetic materials brittle, which is
`disadvantageous when contained in a device, such as a mobile phone, which may be
`subjected to rough treatment,
`for example by being accidentally dropped.
`In a
`particularly preferred embodiment, the amorphous magnetic material is provided in
`the form ofa flexible ribbon, which may comprise one or morelayers of one or more
`of the same ordifferent amorphous magnetic materials. Suitable materials include
`alloys which may contain iron, boron and silicon or other suitable materials. The
`alloy is melted and then cooled so rapidly (“quenched”) that there is no time forit to
`crystallise as it solidifies, thus leaving the alloy in a glass-like amorphousstate.
`Suitable materials include Metglas® 2714A and like materials.
`Permalloy or
`mumetal orthe like may also be used.
`
`The core in the secondary device, where provided, is preferably a high magnetic
`permeability core. The relative permeability of this core is preferably at least 100,
`even more preferably at
`least 500, and most preferably at
`least 1000, with
`magnitudesofat least 10,000 or 100,000 being particularly advantageous.
`
`The at least one means for generating an electromagnetic field may be a coil, for
`example in the form of a length of wire or a printed strip, or may be in the form ofa
`conductive plate of appropriate configuration, or may comprise any appropriate
`arrangement of conductors.
`A preferred material
`is copper, although other
`conductive materials, generally metals, may be used as appropriate.
`It is to be
`understood that the term “coil” is here intended to encompass any appropriate
`electrical conductor forming an electrical circuit through which current may flow and
`thus generate an electromagnetic field.
`In particular, the “coil” need not be wound
`about a core or formerorthe like, but may be a simple or complex loop or equivalent
`structure.
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`Preferably, the charging area of the primary unitis large enough to accommodatethe
`conductor and/or core of the secondary device in a plurality of orientations thereof.
`In a particularly preferred embodiment,
`the charging area is large enough to
`accommodate the conductor and/or core of the secondary device in any orientation
`thereof.
`In this way, power transfer from the primary unit to the secondary device
`may be achieved without having to align the conductor and/or core of the secondary
`device in any particular direction when placing the secondary device on the charging
`surface of the primary unit.
`
`The substantially laminar charging surface of the primary unit may be substantially
`planar, or may be curved or otherwise configured to fit into a predetermined space,
`such as a glove compartment of a car dashboard or the like.
`It
`is particularly
`preferred that the means for generating an electromagnetic field does not project or
`protrude above or beyond the charging surface.
`
`A kcy feature of the means for generating an electromagnetic field in the primary
`unit is that electromagnetic field lines generated by the means, measured when the
`primary unit is effectively in magnetic isolation (i.e. when no secondary device is
`present on or in proximity to the charging surface), are distributed in two dimensions
`overthe at least one charging area and subtend an angle of 45° orless to the charging
`area in proximity thereto (for example, less than the height or width of the charging
`area) and over any quarter length part of the charging area measured in a direction
`generally parallelto that of the field lines. The measurementofthefield lines in this
`connection is to be understood as a measurementofthe field lines when averaged
`over the quarter length of the charging area, rather than an instantaneous point
`measurement.
`In some embodiments,the field lines subtend an angle of 30° or less,
`and in some embodiments are substantially parallel to at least a central part of the
`charging area in question. This is in stark contrast to prior art systems, where the
`ficld lines tend to be substantially perpendicular to a surface of a primary unit. By
`generating electromagnetic fields that are more or less parallel to or at least have a
`significant resolved componentparallel to the charging area, it is possible to control
`the field so as to cause angular variations thereof, in or parallel to the plane of the
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`charging area, that help to avoid any stationary nulls in the electromagnetic field that
`would otherwise reduce charging efficiency in particular orientations of the
`secondary device on the charging surface. The direction of the field lines may be
`rotated through a complete or partial circle, in one or both directions. Alternatively,
`the direction may be caused to “wobble”or fluctuate, or may be switched between
`two or more directions.
`In more complex configurations, the direction of the field
`lines may vary as a Lissajouspattern orthe like.
`
`In some embodiments, the field lines may be substantially parallel to each other over
`any given charging area, or at least have resolved components in or parallel to the
`plane of the charging area that are substantially parallel to each other at any given
`moment in time.
`
`It is to be appreciated that one means for generating an electromagnetic field may
`serve to provide a field for more than one charging area; also that more than one
`means may serveto provide a field for just one charging area.
`In other words, there
`need not be a one-to-one correspondence of means for generating electromagnetic
`
`fields and charging areas.
`
`The secondary device may adopt a substantially flat form factor with a core thickness
`of 2mm orless. Using a material such as one or more amorphous metal sheets, it is
`possible to have core thickness down to 1mm or less for applications where size and
`weight is important. See Figure 7a.
`
`In a preferred embodiment, the primary unit may include a pair of conductors having
`adjacent coplanar windings which have mutually substantially parallel linear sections
`arranged so as to produce a substantially uniform electromagnetic field extending
`generally parallel to or subtending an angle of 45° or less to the plane of the
`windings but substantially at right angles to the parallel sections.
`
`The windings in this embodiment may be formed in a generally spiral shape,
`comprisinga series ofturns having substantially parallel straight sections.
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`Advantageously, the primary unit may include first and second pairs of conductors
`which are superimposed in substantially parallel planes with the substantially parallel
`linear sections of the first pair arranged generally at right angles to the substantially
`parallel linear sections of the second pair, and further comprising a driving circuit
`which is arranged to drive them in such a way as to generate a resultant field which
`rotates in a plane substantially parallel to the planes of the windings.
`
`According to a fifth aspect of the present invention, there is provided a system for
`transferring power in a contact-less manner consisting of:
`e
`a primary unit consisting of at least one electrical coil whereby each coil
`features at
`least one active area whereby two or more conductors are
`substantially distributed over this area in such a fashion that it is possible for
`a secondary device to be placed in proximity to a part of this active area
`where the net
`instantaneous current
`flow in a particular direction is
`
`substantially non-zero;
`eat least one secondary device consisting of conductors wound around a high
`permeability core in such a fashion that it is possible for it to be placed in
`proximity to an area of the surface of the primary unit where the net
`instantaneous current flow is substantially non-zero,
`wherebythe at least one secondary deviceis capable of receiving power by means of
`electromagnetic induction when the central axis of the winding is in proximity to the
`active area of the primary unit, is substantially not perpendicular to the plane of the
`active area of primary unit and is substantially not parallel to the conductors in the
`active area ofat least one ofthe coils of the primary unit.
`
`Where the secondary device comprises an inductively rechargeable battery or cell,
`the battery or cell may have a primary axis and be capable of being recharged by an
`alternating field flowing in the primary axis of the battery or cell, the battery or cell
`consisting of:
`e
`an enclosure and external electrical connections similar in dimensions to
`industry-standard batteries or cells
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`®
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`e
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`*
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`e
`
`an energy-storage means
`
`an optional flux-concentrating means
`
`a power-receiving means
`
`ameansof converting the received power to a form suitable for delivery to
`outside the cell through the externalelectrical connections, or to recharge the
`
`energy storage means, or both.
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`The proposed invention is a significant departure from the design of conventional
`inductive power transfer systems. The difference between conventional systems and
`the proposed system is best illustrated by looking at their respective magnetic flux
`line patterns. (See Figure 2a and 4)
`
`In a conventional system (See Figure 2a), there is
`¢ Conventional System:
`typically a planar primary coil which generates a magnetic field with flux
`lines coming out of the plane in a perpendicular fashion. The secondary
`device has typically a round or square coil that encircles someor all of these
`
`flux lines.
`
`e
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`the magnetic field travels
`In the proposed system,
`Proposed system:
`substantially horizontally across the surface of the plane (see Figure 4)
`instead of directly out of the plane as illustrated in Figure 2a. The secondary
`device hence may have an elongated winding wound around a magnetic core.
`See Figure 7a and 7b. When the secondary device is placed on the primary
`unit, the flux lines would beattracted to travel through the magnetic core of
`the secondary device because it is the lowest reluctance path. This causes the
`secondary device and the primary unit to be coupled effectively.
`The
`secondary core and winding maybe substantially flatten