HK1143463B - Improvements relating to contact-less power transfer - Google Patents

Abstract

There is disclosed a system and method for transferring power without requiring direct electrical conductive contacts. There is provided a primary unit having a power supply and a substantially laminar charging surface having at least one conductor that generates an electromagnetic field when a current flows therethrough and having an charging area defined within a perimeter of the surface, the at least one conductor being arranged such that electromagnetic field lines generated by the at least one conductor are substantially parallel to the plane of the surface or at least subtend an angle of 45 or less to the surface within the charging area; and at least one secondary device including at least one conductor that may be wound about a core. Because the electromagnetic field is spread over the charging area and is generally parallel or near-parallel thereto, coupling with flat secondary devices such as mobile telephones and the like is significantly improved in various orientations thereof.

Description

Contactless power transmission device and method

The application is a divisional application, and the original application is the application number 03810505.5, the application date is 2003-5-13, and the name of the invention is 'contactless electric energy transmission device and method'.

This application claims priority to british patent application nos. 0210886.8, 0213024.3, 0225006.6 and 0228425.5 filed on days 5 and 13 in 2002, 6 and 7 in 2002, 10 and 28 in 2002 and 12 and 6 in 2002, respectively, and to us patent application No. 10/326,571 filed on day 20 in 2002. All of these prior patent applications are incorporated herein by reference in their entirety.

Field of operation

The invention relates to a novel device and a method for the contactless transmission of electrical energy.

Background

Many portable devices today incorporate a "secondary" battery that can be recharged, saving the user the cost and inconvenience of having to purchase a new battery on a regular basis. Examples of such portable devices include cellular telephones, laptop computers, personal digital assistants of the palm 500 series, electric shavers, and electric toothbrushes. In some such devices, the battery is recharged through inductive coupling rather than a direct electrical connection. Examples include the plane Control electric toothbrush by Braun Oral B, the digital cordless telephone solution KX-PH15AL by Panasonic, and the multiple-head male razor ES70/40 series by Panasonic.

Each such device typically has an adapter or charger that takes power from a power supply, an automobile cigarette lighter, or other power source and converts it to a form suitable for charging the battery. The conventional methods employed to provide power or charge for these devices have a number of problems:

the characteristics of the battery within each device and the method of connection to the battery vary considerably from manufacturer to manufacturer and device to device. A user who owns several such devices must also own several different adapters. If a user were to go on a trip and wish to use their device during that time, they would have to carry all of their chargers.

These adapters and chargers often require the user to plug a small connector into the device or to accurately calibrate the device into the housing, which is inconvenient. If a user fails to plug or place their device into the charger and the device has run out of power, the device will become useless and important data stored locally in the device may even be lost.

In addition, most adapters and chargers have to be plugged into a power outlet, so if several adapters and chargers are used together, they will take up space in the strip of sockets and cause the wires to become tangled and tangled.

In addition to the above problems with conventional methods of recharging devices, there are many practical problems with devices having open electrical contacts. For example, the device cannot be used in a humid environment, due to the possibility of corroding or short-circuiting the contacts, and in a combustible gas environment, due to the possibility of generating electric sparks.

Chargers using inductive charging do not need to have open electrical contacts, thus allowing the adapter and device to be sealed and used in wet environments (e.g., the above-mentioned power toothbrushes are designed for use in bathrooms). However, such chargers still face all other problems described above. For example, the device still needs to be accurately placed in the charger so that the device and the charger are in a predetermined relative position (see fig. 1a and 1 b). The adapter is still only designed to be dedicated to a certain configuration and type of device and is still only able to charge one device at a time. As a result, the user still needs to own and manage multiple different adapters.

There are also universal chargers (e.g., Maha MH-C777+ universal charger) so that battery packs of different shapes and characteristics can be removed from the device and charged using the same device. While these universal chargers eliminate the necessity of having different chargers for different devices, they create even greater inconvenience to the user because the battery pack needs to be removed first, then the charger needs to be adjusted, and the battery pack needs to be placed accurately into or against the charger. In addition, it must take time to determine the correct pair of battery pack metal contacts that the charger must use.

It is known from US 3,938,018 "inductive charging system" to provide a contactless battery charging apparatus by means of which the Induction coil on the primary side can be aligned with the horizontal Induction coil on the secondary side device when the device is placed in a recess on the primary side. This recess ensures the relatively precise alignment necessary for the design, and thus ensures good coupling between the primary and secondary coils.

It is also known from US 5,959,433 "universal inductive Battery Charger System", which provides a contactless Battery charging System. The described battery charger comprises a single charging coil that generates magnetic field lines that will induce a current in a battery pack that may belong to a cell phone or laptop computer.

It is also known from US 4,873,677 "Charging Apparatus for Electronic devices" to provide an Apparatus for Charging an Electronic Device, the Apparatus comprising a pair of coils. The pair of coils are designed for anti-phase operation such that the magnetic flux lines are coupled from one coil to the other. An electronic device such as a watch may be placed over the two coils to receive power.

It is also known from US 5,952,814 "inductive charging device and electronic equipment" (which provides an inductive charger for charging a rechargeable battery). The housing shape of the electronic device matches the internal shape of the charger, thereby allowing precise alignment of the primary and secondary coils.

It is also known from US 6,208,115 "alternative Battery pack" to provide an alternative Battery pack that can be inductively charged.

It is known from WO 00/61400 "Device for inductive transfer of Electrical energy" (which provides a method of inductively transferring Electrical energy to a transfer Device).

It is known from WO 95/11545 "Inductive power pick-up coils" to provide a system for inductively providing electrical power to an electric vehicle from a series of built-in flat primary coils.

In order to overcome the limitations of inductive power transfer systems that require axial alignment of the secondary device with the primary device, one may propose an obvious solution, namely to use a simple inductive power transfer system by means of which the primary device is able to emit an electromagnetic field over a large area (see fig. 2 a). The user may simply place one or more devices to be charged within range of the primary unit without requiring their precise placement. For example, the primary means may comprise a coil surrounding a larger area. When a current flows through the coil, an electromagnetic field is generated that extends over a large area, and the device can be placed anywhere within that area. Although this method is theoretically possible, it has many drawbacks. First, the intensity of the electromagnetic emission is controlled by the tuning range. This means that the method only supports rate-limited power transfer. In addition, many objects may be affected by the presence of strong magnetic fields. For example, data stored on a credit card may be corrupted and eddy currents will be induced inside the object made of metal, thereby producing an undesirable heating effect. In addition, if a secondary device comprising a conventional coil (see fig. 2a) is placed opposite a metal housing, such as a copper plate in a printed circuit board or a battery, the coupling may be significantly reduced.

In order to avoid the generation of large magnetic fields, it may be advisable to use a coil array, by means of which only the required coils are activated (see fig. 3). The method is described in a paper entitled "Coil Shape in Desk-top contact Power station StationalSyetem" published in Japan magnetic society journal, 11/29 2001. In one embodiment of the multi-coil principle, the sensing mechanism detects the relative position of the secondary device with respect to the primary device. The control system then activates the corresponding coil to deliver power to the secondary device in a localized manner. While this approach provides a solution to the problems listed previously, it is both complex and expensive to implement. The extent to which the primary field can be localized is limited by the number of coils and hence the number of drive circuits used (i.e. the "resolution" of the primary). The cost of a multi-coil system would greatly limit the commercial application of this principle. Non-uniform field distribution is also a drawback. When all the coils in the primary are activated, they together are equivalent to one large coil, whose magnetic field distribution is shown to be minimal in the center of the coil.

Another solution is outlined in US 5,519,262 "Near Field power coupling System", where the primary has a large number of narrow inductive coils (or optionally capacitive plates) arranged from one end of a flat plate to the other, generating a large number of vertical fields driven in a phase-shifted manner, such that a moving sine wave moves over the plate. The receiving device is arranged with two vertical field receiving means so that it always collects power from at least one receiving means, no matter where the receiving device is located on the board. Although this solution also provides freedom of movement for the device, it has some disadvantages in that it requires a complex secondary arrangement, has a fixed breakdown and is poorly coupled because the return flux path is through air.

None of the prior art solutions satisfactorily solves all the problems described. It would be desirable if a solution could be obtained that could transfer power to a portable device with all of the following features, and that could be implemented at a cost effective rate:

versatility: a single primary device that can provide power to different secondary devices having different power requirements, thereby eliminating the need for multiple different adapters and chargers;

convenience: a single primary device that allows the secondary device to be placed anywhere within effective proximity, thereby eliminating the need to insert or precisely place the secondary device relative to an adapter or charger;

multiple loads: a single primary device that can simultaneously provide power to a plurality of different secondary devices having different power requirements.

Flexibility for different environments: a single primary device that can provide power to the secondary device without requiring direct electrical contact, allowing the secondary device and the primary device themselves to be used in wet, gas-containing, clean, and other unusual environments;

low electromagnetic emission: a single primary unit that can deliver electrical energy in a manner that minimizes the strength and magnitude of the generated magnetic field.

It will also be appreciated that portable devices are being produced in large numbers, all of which require batteries to provide them with electrical power. The galvanic cells or their batteries must be disposed of after use, which is both expensive and environmentally polluting. And the storage battery or the storage battery pack can be charged and reused.

Many portable devices have a container filled with batteries such as AA, AAA, C, D and PP3 of industry standard size and voltage. This allows the user to freely choose whether to use primary or secondary batteries and different types of batteries. Once used up, the batteries must typically be removed from the apparatus and placed in a separate charging device. Alternatively, some portable devices have built-in charging circuitry that allows the battery to be charged in situ when the device is plugged into an external power source.

It is inconvenient for the user to have to remove the battery from the device for charging or plug the device into an external power source for charging in situ. It is desirable to be able to charge the battery in some non-contact manner without having to perform any of the operations described above.

Some portable devices are capable of receiving power from a charger in an inductively coupled manner, such as the Plak Control toothbrush by Braun Oral B. Such portable devices typically have a custom, dedicated power receiving module built into the device which is then connected to an internal standard battery or battery pack (which may or may not be removable).

However, it would be convenient if a user could convert any portable device that accepts industry standard battery sizes into an inductively charged device simply by installing an inductively charged battery or battery pack that can be charged by placing the device on an inductive charger.

Examples of prior art also include US 6,208,115 which discloses an alternative battery pack which can be inductively charged.

Disclosure of Invention

According to a first aspect of the present invention there is provided a system for transferring electrical energy without requiring direct conductive contact, the system comprising:

i) a primary unit comprising a substantially laminar charging surface and at least one means for generating an electromagnetic field, the means being distributed in two dimensions over a predetermined area within or parallel to the charging surface to define at least one charging area of the charging surface substantially coextensive with the predetermined area, the charging area having a width and a length over the charging surface, wherein the unit is configured in such a way that: when a predetermined current is delivered into the device and the primary device is effectively electromagnetically isolated, the electromagnetic field generated by the device has electromagnetic field lines that make an angle of 45 ° or less near the charging surface and are distributed in two dimensions over the charging surface when averaged over any quarter length portion of the charging area measured in a direction parallel to the electromagnetic field lines; and wherein the height of the device, measured substantially perpendicular to the charging area, is less than the width or length of the charging area; and

ii) at least one secondary device comprising at least one electrical conductor; wherein when the at least one primary device is placed on or proximate to a charging area of the primary apparatus, the electromagnetic field lines couple with the at least one conductor of the at least one secondary apparatus and induce a current to flow therein.

According to a second aspect of the present invention there is provided a primary unit for transferring electrical energy without requiring direct conductive contact, the primary unit comprising a charging surface which is substantially laminar and at least one means for generating an electromagnetic field, the means being distributed in two dimensions over a predetermined area within or parallel to the charging surface to define at least one charging area of the charging surface which is substantially coextensive with the predetermined area, the charging area having a width and a length over the charging surface, wherein the unit is configured in such a way that: when a predetermined current is delivered into the device and the primary device is effectively electromagnetically isolated, the electromagnetic field generated by the device has electromagnetic field lines that make an angle of 45 ° or less near the charging surface and are distributed in two dimensions over the charging surface when averaged over any quarter length portion of the charging area measured parallel to one direction of the field lines; and wherein the height of the device, measured substantially perpendicular to the charging area, is less than the width or length of the charging area.

According to a third aspect of the present invention there is provided a method of transferring electrical energy in a non-conductive manner from a primary device to a secondary device, the primary device comprising a substantially laminar charging surface and at least one means for generating an electromagnetic field, the means being distributed in two dimensions over a predetermined area within or parallel to the charging surface to define at least one charging area of the charging surface substantially coextensive with the predetermined area, the charging area having a width and a length over the charging surface, the height of the device measured substantially perpendicular to the charging area being less than the width or length of the charging area, and the secondary device having at least one electrical conductor; wherein:

i) when the electromagnetic field generated by passing a predetermined current through the device and measured when the primary device is effectively electromagnetically isolated has electromagnetic field lines that, when averaged over any quarter length portion of the charging area measured parallel to one direction of the field lines, are at an angle of 45 ° or less to the charging surface proximate thereto and are distributed in two dimensions over at least one charging area when averaged over the charging area; and

ii) an electromagnetic field is coupled to the secondary device when the conductor is placed on or near the charging area.

According to a fourth aspect of the present invention there is provided a secondary device for use with the system, device or method of the first, second or third aspects. The secondary device includes at least one electrical conductor and has a substantially laminar form factor.

In the context of the present application, the word "lamellar" defines the geometry of a sheet or lamella shape. The sheet or lamina may be substantially flat or may be curved.

The primary device may comprise a power supply for the at least one means for generating an electromagnetic field or may be provided with a connector or similar means enabling the at least one means to be connected to an external power supply.

In some embodiments, the height of the means for generating an electromagnetic field is no more than (only) half the width or half the length of the charging area; in some embodiments, the height may be only 1/5 the width or 1/5 the length of the charging region.

At least one electrical conductor in the secondary device may be wound around a magnetic core for collecting the incoming magnetic field lines. In particular, the core, if provided, may provide a path of least resistance to the field lines of the electromagnetic field generated by the primary unit. The core may be an amorphous magnetically conductive material. In some embodiments, an amorphous magnetic core need not be used.

If an amorphous core is provided, the amorphous magnetic material is preferably in an unannealed or substantially cast state. The material may be at least 70% unannealed, or preferably at least 90% unannealed. This is because annealing tends to make the amorphous magnetic material susceptible to fracture, which is disadvantageous for inclusion in devices such as mobile phones, which may be subjected to severe impact due to accidental dropping, for example. In a particularly preferred embodiment, the amorphous magnetic material is in the form of a flexible tape, which may comprise one or more layers of one or more of the same or different amorphous magnetic materials. Suitable materials include alloys that may include iron, boron, and silicon or other suitable materials. The alloy is melted and then rapidly cooled ("quenched") to solidify before crystallization occurs, leaving the alloy in a glassy, amorphous state. Suitable materials include2714A, and the like. Permalloy, or the like may also be used.

The magnetic core in the secondary device is preferably a high permeability magnetic core, if provided. The relative permeability of such a core is preferably 100, more preferably at least 500, most preferably at least 1000, and is particularly advantageous in the order of at least 10,000 or 100,000.

The at least one means for generating an electromagnetic field may be in the form of a coil, for example a wire or printed strip having a length, or may be in the form of a conductive plate having a suitable configuration, or the means may also comprise any suitable arrangement of wires. The preferred material is copper, although other conductive materials, typically metals, may be suitably used. It should be understood that the term "coil" is intended herein to include any suitable electrically conductive wire that forms an electrical circuit through which an electrical current may flow to generate an electromagnetic field. In particular, the "coil" need not be wound around a core or former or the like, but may be a simple or complex loop or equivalent structure.

Preferably, the charging area of the primary device is large enough to accommodate the wires and/or magnetic core of the secondary device in multiple orientations. In a particularly preferred embodiment, the charging area is large enough to accommodate the wires and/or the core of the secondary device in any orientation. In this manner, transfer of electrical energy from the primary device to the secondary device can be accomplished without having to align the wires and/or magnetic cores of the secondary device in any particular direction when the secondary device is placed on the charging surface of the primary device.

The substantially laminar charging surface of the primary unit may be substantially flat or may be curved or designed to fit into a predetermined space, such as a glove compartment of a motor vehicle. It is particularly preferred that the means for generating an electromagnetic field does not project or protrude from the charging surface beyond the charging surface.

An important feature of the means for generating an electromagnetic field within the primary means is that the electromagnetic field lines generated by the means and measured when the primary means is in effective magnetic isolation (i.e. when no secondary means is present on or near the charging surface) are distributed in two dimensions over at least one charging area, are at an angle of 45 ° or less to the charging area close thereto (e.g. less than the height or width of the charging area), and are averaged over any quarter length portion of the charging area measured generally parallel to the direction of the field lines. A measurement of a field line in such a relationship should be understood as a measurement of the field line when averaged over a quarter length of the charging area, rather than a measurement of the instantaneous point. In some embodiments, the field lines are at an angle of 30 ° or less. In some embodiments, the field lines are substantially parallel to at least a central portion of the designated charging area. This is in stark contrast to prior art systems. In prior art systems, the field lines tend to be substantially perpendicular to one surface of the primary. By generating an electromagnetic field that is more or less parallel to the charging area or has at least one significant resolved component parallel to the charging area, it is possible to control the field to produce an angular variation in the plane of the charging area or in a plane parallel thereto that helps to avoid any static null in the electromagnetic field that would otherwise reduce the charging efficiency for a particular orientation of the secondary device on the charging surface. The direction of the field lines can be rotated in one or both directions by a full circle or half circle. Alternatively, the magnetic field direction may "dither" or fluctuate, or may switch between one or more directions. In more complex structures, the direction of the field lines may vary in Lissajous figures or the like.

In some embodiments, the field lines may be substantially parallel to each other over any particular charging region, or at least have a resolved component in the charging region or in a plane parallel to the charging region, which are substantially parallel to each other at any particular time.

It should be understood that one means for generating an electromagnetic field may be used to provide an electromagnetic field for more than one charging area; it should also be appreciated that more than one device may be used to provide an electromagnetic field with only one charging area. In other words, the means for generating an electromagnetic field and the charging area do not have to correspond one-to-one.

The secondary device may take a substantially flat form factor with a core thickness of 2mm or less. Using a material such as one or more amorphous metal plates, it is possible to reduce the core thickness to 1mm or less for applications where size and weight are important. See fig. 7 a.

In a preferred embodiment, the primary means may comprise a pair of conductors having adjacent co-planar windings, the conductors having linear portions arranged substantially parallel to each other to generate a substantially uniform electromagnetic field which extends generally parallel to the plane of the windings, or at an angle of 45 ° or less to the plane of the windings, but substantially at right angles to the parallel portions.

The winding in this embodiment may be configured in a generally spiral shape comprising a series of turns having substantially parallel straight portions.

Advantageously, the primary device may comprise first and second pairs of wires, the pairs of wires lying in substantially parallel planes and the substantially parallel linear portions of the first pair of wires being arranged generally at right angles to the substantially parallel linear portions of the second pair of wires; the primary unit further comprises a drive circuit arranged to drive the two pairs of conductors in such a way as to generate a resultant field that rotates in a plane substantially parallel to the plane of the windings.

According to a fifth aspect of the present invention, there is provided a system for transferring electrical energy in a contactless manner, the system comprising:

a primary device consisting of at least one electric coil, wherein each coil is characterized by at least one active area (active area) in which two or more wires are substantially distributed in such a way as to make it possible to place the secondary device close to a portion of this active area, in which the net instantaneous current flowing in a particular direction is substantially non-zero;

at least one secondary device comprising a wire wound around a high permeability core in such a way as to make possible the placement of the secondary device in a region close to the surface of the primary device, in which region the net instantaneous current is substantially non-zero;

thereby, the at least one secondary device is capable of receiving electrical energy by electromagnetic induction when a central axis of the winding is proximate to an active area of the primary device, a plane substantially non-perpendicular to the active area of the primary device, and a wire within the active area of the at least one coil of the primary device.

Where the secondary device comprises an inductively rechargeable battery or cell, the battery or cell may have a major axis and can be charged by an alternating field flowing along the major axis of the battery or cell, the battery or cell comprising:

housings and external electrical connection means of similar size to the battery or cell of the industrial standard

Energy storage device

Optional magnetic line gathering device

Electric energy receiving device

Means for converting the electrical energy received into a form suitable for transmission outside the battery, or means for charging the energy storage device, or both, by means of an external electrical connection.

The proposed invention is significantly different from the design of conventional inductive power transfer systems. The differences between the conventional system and the proposed system can best be clarified by referring to their respective magnetic force line profiles. (see FIGS. 2a and 4)

The conventional system: in conventional systems (see fig. 2a), there is usually a planar primary coil which generates a magnetic field whose lines emerge in a perpendicular manner from the plane of the coil. The secondary device typically has a circular or square coil that surrounds some or all of these flux lines.

The proposed system: in the proposed system, the magnetic field proceeds substantially horizontally along the surface of the coil plane (see fig. 4), rather than directly out of the coil plane as shown in fig. 2 a. Thus, the secondary device may have an elongated winding wound around the magnetic core. See fig. 7a and 7 b. When the secondary device is placed on the primary device, the magnetic field lines will be attracted to travel through the magnetic core of the secondary device because it is the path of least magnetic reluctance. This allows the secondary device and the primary device to be effectively coupled. The core and the winding of the secondary device may be substantially flattened to form a very thin component.

In describing the present invention, specific terminology will be resorted to for the sake of clarity. However, it is not intended that the invention be limited to the specific terms so selected and it is to be understood that each specific term includes all technical equivalents which operate in a similar manner to accomplish a similar purpose.

It should be understood that the term "charging region" as used in this patent application may refer to a region of at least one device (e.g., one or more wires in the form of a coil) for generating a field, or a region formed by the union of primary wires, within which a secondary device may effectively couple magnetic field lines. Some embodiments regarding the charging area are shown in fig. 6 a-6 l and 9c as component 740. One characteristic of the "charging area" is that the conductors are distributed over the active area of the primary unit, so constructed that at least one device for generating a field can be driven to obtain instantaneous net magnetic field lines flowing in one direction. The primary unit may have more than one charging area. When the flux lines cannot be effectively coupled by the secondary device in any rotation at the boundary (such as those shown in fig. 7a), one charging region is different from the other.

It should be understood that the term "coil" as used in this patent refers to all wire configurations that feature a charging region as described above. This includes wire windings or printed traces or planes as shown in figure 8 e. The wires may be made of copper, gold, an alloy or any other suitable material.

The present application mentions the rotation of the secondary device in several places. It should be clarified here that if the secondary device is rotated, the mentioned axis of rotation is perpendicular to the plane of the charging area.

This fundamental change in design overcomes at least one of the deficiencies of conventional systems. The benefits of the proposed invention include:

no precise alignment is required: the secondary device may be placed anywhere on the charging area of the primary device;

uniform coupling: in the proposed invention, the coupling between the primary and secondary devices is more uniform over the charging area than conventional primary and secondary coils. In a conventional large coil system (see fig. 2a), the field strength is minimized in the center of the coil in the coil plane (see fig. 2 b). This means that the minimum field strength must be above a certain threshold value if sufficient power can be effectively transferred at the central location. The maximum field strength will be much higher than the required threshold value which may lead to undesired results.

Versatility: a plurality of different secondary devices, even those with different power requirements, may be placed in a charging area on the charging surface of the primary device to receive power simultaneously.

The coupling coefficient increases: the optional high permeability magnetic material in the secondary device greatly increases the induced magnetic flux by providing a path of low reluctance. This can greatly increase the electrical energy transfer.

Ideal form factor for the secondary device: the geometry of the present system allows the use of thin-sheet magnetic materials (e.g., amorphous metal strips). This means that the secondary device can have a laminar form factor making it suitable for mounting at the rear of mobile phones and other electronic equipment. If a magnetic material is used in the center of the conventional coil, it is possible to increase the volume of the secondary device.

Minimal field leakage: when one or more secondary devices are present in the charging region of the primary device, it is possible to use magnetic material in such a way that more than half of the magnetic circuit is of low reluctance material (see fig. 4 d). This means that for a particular magnetomotive force (mmf) more magnetic flux lines will flow in. This will increase the power transferred to the secondary device, since the induced voltage is proportional to the rate of change of the coupled magnetic flux. The fewer and shorter the air gap in the magnetic circuit, the fewer the edges of the field, the closer the magnetic field lines are to the surface of the primary, so leakage is also minimal.

Cost-effective: unlike the multi-coil design, the solution of the present invention requires a simpler control system and fewer components.

Free pivoting of the secondary: if the secondary device is laminar or alternatively even cylindrical (see fig. 10), it can be constructed such that it maintains good coupling with the flux lines, regardless of whether it rotates about the longest axis or not. This may be particularly advantageous if the secondary device is a battery cell mounted in another apparatus, as the pivoting of the secondary device may be difficult to control.

The magnetic core in the secondary device may be arranged to be located in the vicinity of other parallel metal planes in or near the apparatus, for example in the vicinity of a copper printed circuit board or an aluminium cover. In this case, the performance of embodiments of the present invention is much better than that of conventional coils wound around a core, because the field lines passing through a conventional device coil will suffer from repulsion of the magnetic lines if the conventional device coil is placed facing a metal plane (because the magnetic lines must propagate perpendicular to the plane of the coil). Since in embodiments of the invention the magnetic field lines propagate along the plane of the core and hence also along the metal plane, the performance is improved. An additional benefit is that the magnetic core within the secondary device of embodiments of the present invention may act as a shield between the electromagnetic field generated by the primary device and the electromagnetic field generated by any component on the other side of the magnetic core (e.g., the circuitry and battery cells).

Since the magnetic permeability of the core of the secondary device of an embodiment of the invention is higher than that of air, it serves to concentrate the magnetic field lines, which captures more magnetic field lines that would otherwise flow through an equivalent air cross section. The size of the core "form factor" (equivalent field line capture range) is determined to be a first order approximation by the longest planar dimension of the core. Therefore, if the planar dimensions of the magnetic core of the secondary device of an embodiment of the present invention have a large non-square aspect ratio, such as a rectangle with an aspect ratio of 4: 1, rather than a square with an aspect ratio of 1: 1, it will capture proportionally more of any magnetic field lines propagating in a direction parallel to the longest planar dimension. Therefore, if the magnetic core is used for a device having a limited aspect ratio (for example, a long and thin device such as a headphone or a pen), the performance thereof will be greatly improved as compared with that of a conventional coil of the same area.

The primary unit is generally composed of the following components. (see FIG. 5)

Power supply: the power supply converts the supply voltage to a lower voltage direct current. This is usually a conventional transformer or switched mode power supply;

the control device: the control means functions to maintain the circuit resonant if the inductance of the means for generating the field varies with the presence of the secondary means. To enable this function, the control means may be coupled to sensing means for feeding back the current state of the circuit. It may also be coupled to a bank of capacitors that may be switched in or out as desired. If the means for generating the field requires more than one drive circuit, the control means may also adjust parameters such as phase differences or the number of on/off times of different drive circuits to achieve the desired result. It is also possible to design the Q (quality factor) of the system to function within a certain inductance range, thereby eliminating the need for the above control system;

a driving circuit: the drive circuit is controlled by the control means and drives a varying current through the means or a component of the means for generating a field. Depending on the number of individual components in the device, there may be more than one drive circuit;

means for generating an electromagnetic field: the device generates an electromagnetic field of a predetermined shape and intensity using a current supplied from a driving circuit. The particular structure of the device defines the shape and strength of the field generated. The device may comprise a magnetic material acting as a flux guide and also one or more separate drive components (windings), together forming a charging region. Many embodiment designs are possible, an example of which is shown in FIG. 6.

The sensing means: the sensing device retrieves and sends the relevant data to the control device for analysis.

The secondary device is generally composed of the following components, as shown in fig. 5.

Magnetic means: the magnetic device converts the energy stored in the magnetic field generated by the primary device back into electrical energy. This is usually achieved by means of windings wound around a high permeability core. The maximum dimension of the core is generally coincident with the central axis of the winding.

A conversion device: the conversion means converts the fluctuating current received from the magnetic means into a form useful to the device to which it is coupled. For example, the conversion means may convert the ripple current into unregulated direct current by means of a full wave bridge rectifier and a filter capacitor. In other cases, the switching circuit may be coupled to a heating element or a battery charger. There is also typically a capacitor connected in parallel or series with the magnetic device to form a resonant circuit operating at the operating frequency of the primary device.

In typical operation, one or more secondary devices are placed over a charging surface of a primary device. The magnetic field lines flow through the at least one conductor and/or the magnetic core of the secondary device present and induce an electric current. Depending on the configuration of the means for generating the field in the primary arrangement, the rotational positioning of the secondary arrangement may influence the amount of magnetic field lines coupled.

Primary device

The primary unit may exist in many different forms, for example:

flat platforms or pads that can be placed on tables and other smooth surfaces;

built into furniture such as desks, tables, counters, chairs, bookshelves, etc., so that the primary device is not visible;

a portion of a container, such as a drawer, a box, a cabinet on the dashboard of a car, and a container for a power tool;

flat platforms or pads that can be glued to a wall and used upright.

The primary unit may be powered from different power sources, for example:

AC mains outlet

Vehicle igniter socket

Batteries

Fuel cell

Solar panels

Manpower (human power)

The primary device may be small enough that only one secondary device is housed on the charging surface within a single charging area, or may be large enough to house multiple secondary devices simultaneously, often housed in different charging areas.

The means for generating the field in the primary unit may be driven at the mains frequency (50Hz or 60Hz) or some higher frequency.

The sensing means of the primary device may detect the presence of the secondary device, the number of secondary devices present, or even the presence of other magnetic materials that are not part of the secondary device. This sensed information may be used to control the current delivered to the field generating means of the primary unit.

The primary device and/or the secondary device may be substantially waterproof or explosion proof.

The primary device and/or the secondary device may be sealed according to a standard such as IP 66.

The primary device may include a visual indicator (e.g., without limitation, a light emitting device such as a light emitting diode, an electro-phosphorescent display, a light emitting polymer, or a light reflecting device such as a liquid crystal display or MIT electronic paper) to indicate the current state of the primary device, the presence of a secondary device, or the number of secondary devices present, or any combination thereof.

Device for generating an electromagnetic field

The field generating means mentioned in the present application comprise all configurations of wires, wherein:

the wires are distributed substantially in a plane and;

there is a planar substantial area (substitional area) where there is a non-zero net instantaneous current. Given the correct orientation, the secondary device will efficiently couple and receive power over these areas. (see FIG. 6)

The wire is capable of generating an electromagnetic field in which the field lines make an angle of 45 ° or less with a substantial area of the plane, or are substantially parallel with a substantial area of the plane.

Fig. 6 shows some possible configurations of such a primary wire. Although most structures are actually coil windings, it should be appreciated that wire planes that are not normally considered coils can achieve the same effect (see fig. 6 e). These figures are some typical examples, but are not exhaustive. These wires or coils can be used in combination so that the secondary device can be effectively coupled in all turns at the same time over the charging area of the primary device.

Magnetic material

It is possible to use magnetic materials in the primary device to enhance performance.

The magnetic material may be placed under one or more charging areas or the entire charging surface so that there is also a low reluctance path under the conductor for the magnetic field lines to complete its path. In theory, the magnetic circuit is similar to an electrical circuit. Voltage is similar to magnetomotive force (mmf), resistance is similar to reluctance, and current is similar to magnetic force lines (flux). From this it can be seen that for a given mmf, the flux flow will increase if the reluctance of the path decreases. By arranging the magnetic material below the charging area, the reluctance of the magnetic circuit is essentially reduced. This effectively increases the magnetic flux coupled by the secondary device and ultimately the electrical energy transferred. Fig. 4d shows the magnetic material plates placed under the charging area and the resulting magnetic circuit.

Magnetic material can also be placed above the charging surface and/or charging area, and below the secondary device, to act as a flux guide. The flux guide performs two functions: first, the reluctance of the entire magnetic circuit is further reduced to allow more magnetic flux to flow. Secondly, it provides a path of low reluctance along the upper surface of the charging region, so that the magnetic field lines will flow through the flux guides rather than through the air. This therefore has the effect of controlling the field near the charging surface of the primary unit, rather than containing it in air. The magnetic material for the flux guide may be strategically or intentionally chosen to provide the magnetic core of the secondary device (if provided) with different magnetic properties. For example, a material with a lower magnetic permeability and a higher saturation magnetic property may be selected. High saturation magnetization means that the material can carry more magnetic flux, and lower permeability means that a large number of magnetic lines of force will be selected to pass through the secondary device rather than being magnetically conductive when the secondary device is nearby. (see FIG. 8)

In some primary arrangement field generating device configurations, there may be conductors that do not form part of the charging area, such as the component labeled 745 in fig. 6a and 6 b. In this case, it may be desirable to shield the wires from the effects of the magnetic material.

Some examples of materials that may be used include, but are not limited to: amorphous metals (metallic glass alloys such as MetGlas^TM) Electric wire made of magnetic materialMesh, steel, ferrite core, permalloy, and permalloy.

Secondary device

The secondary device may have different shapes and forms. Generally, for better magnetic flux coupling, the central axis of the wire (e.g., coil winding) should not be substantially perpendicular to the charging area.

The primary device may have the shape of a flat winding (see fig. 7 a). The inner magnetic core may be formed from a sheet of magnetic material such as an amorphous metal. This geometry enables the secondary device to fit into the back of electronic equipment such as mobile phones, personal digital assistants and laptop computers without adding bulk to the equipment.

The secondary device may have the shape of an oblong cylinder. Around the long cylindrical magnetic core, wires may be wound (see fig. 7 b).

The secondary device may be an object surrounded by magnetic material. One example is a standard size (AA, AAA, C, D) or other size/shape (e.g., specific/customized for a particular application) rechargeable battery cell having, for example, magnetic material wrapped around a cylinder and windings wrapped around the cylinder.

The secondary device may be a combination of two or more of the above. The above embodiments may even be combined with conventional coils.

The following non-exhaustive list illustrates some examples of objects that may be coupled to a secondary device to receive electrical energy. May not be limited to the following:

a mobile communication device, such as a radio, mobile phone or intercom;

a portable computing device, such as a personal digital assistant or a palmtop or laptop computer;

portable entertainment devices, such as music players, gamepads or toys;

personal hygiene tools, such as toothbrushes, shavers, hair curlers;

portable imaging devices, such as video camcorders or cameras;

containers for holding items that may need to be heated, such as coffee cups, plates, rice cookers, nail polish, and cosmetic cases;

consumer devices such as flashlights, clocks and fans;

electric tools, such as drills and screwdrivers for both ac and dc;

wireless peripherals such as wireless computer mouse, keyboard and headphones;

timing devices, such as clocks, watches, stopwatches, and alarm clocks;

a battery pack for inserting any of the above devices;

standard size battery cells.

In the case of non-intelligent secondary devices such as battery cells, some sophisticated charge control means may also be required to meter the inductive power supplied to the cells, and to handle situations where multiple cells in the device have different states of charge. Moreover, being able to display a "charged" condition becomes particularly important for the primary unit, as the battery or batteries may not be readily visible when located within other electronic devices.

Figure 10 shows one possible system comprising an inductively rechargeable battery or cell and a primary unit. In addition to optionally placing the battery 920 in the (X, Y) plane and optionally rotating about the rZ axis relative to the primary unit 910, the battery pack can be rotated about its rA axis to continue receiving power.

When a user inserts a battery into a portable device, it is not easy to ensure that it has any particular pivoting. Thus, embodiments of the present invention are highly advantageous because they can ensure that the battery can receive power while rotating about rA in any orientation.

The battery pack or cells may include magnetic flux gathering devices arranged in a variety of ways:

1. as shown in fig. 11a, the battery 930 may be encased within a cylindrical magnetic flux concentration device 931, which is wound with a wire coil 932 around it.

a. The cylindrical device may be long or short relative to the length of the battery.

2. As shown in fig. 11b, the battery 930 may have a magnetic line concentrating device 931 portion on the surface thereof, and a wire coil 932 wound around the magnetic line concentrating device portion.

a. The portion may conform to the surface of the battery or be embedded in the battery.

b. The area of the portion may be large or small with respect to the periphery of the battery, and the portion may be long or short with respect to the length of the battery.

3. As shown in fig. 11c, the interior of the battery 930 may contain a portion of a magnetic line focusing device 931, around which a wire coil 932 is wound.

a. The portion may be substantially flat, cylindrical, rod-like, or any other shape.

b. The width of the portion may be large or small relative to the diameter of the cell.

c. The length of this portion may be large or small relative to the length of the battery.

In either of these cases, the flux-gathering device may be a functional part of the cell housing (e.g., the outer zinc electrode) or the cell itself (e.g., the inner electrode).

Problems related to the charging of storage batteries (e.g., AA rechargeable batteries within a device) include:

the termination voltage may be higher than normal.

The series of batteries may exhibit anomalies, particularly in the case where some of the batteries are charged and others are not.

Have to provide enough power to operate the device and charge the battery.

The battery may be destroyed if rapid charging is not properly implemented.

Thus, it is advantageous to provide some sophisticated charge control means to determine the induced power supplied to the device and the battery. Moreover, being able to display the "charged" status is particularly important for the primary unit, as the battery or batteries may not be readily visible when located within the electronic device.

The battery or battery pack implemented in this manner can be charged by placing the device on the primary unit when mounted in another device, or by placing the battery or battery pack directly on the primary unit when the battery or battery pack is mounted outside the device.

A plurality of battery packs implemented in this manner may be arranged in a battery pack as in a typical device (e.g., end-to-end or side-by-side) so that a single battery pack can replace a set of cells.

Alternatively, the secondary device may be constituted by a flat "adaptor" mounted on the battery pack within the appliance, the flat "adaptor" having thin poles acting downwardly between the battery poles and the appliance contacts.

Rotating electromagnetic field

In coils such as those in fig. 6, 9a and 9b, the secondary devices are typically only effectively coupled when the windings are placed substantially parallel to the direction of the net current in the primary conductor as shown by arrow 1. In some applications, a primary device may be required that will effectively transfer electrical energy to a secondary device regardless of how the secondary device rotates, provided that:

the central axis of the secondary wire is not perpendicular to the plane, and;

the secondary device is in close proximity to the primary device.

To make this possible it is possible to have two coils, for example one on top of the other, or one woven into the other, or woven together with the other, the second coil being able to generate a net current in a direction substantially perpendicular to the first coil at any point within the active area of the primary device. The two coils may be alternately driven so that each is activated for a period of time. Another possibility is to drive the two coils one quarter cycle apart, thereby creating a rotating magnetic dipole in the plane. This is shown in fig. 9. This is also possible for other combinations of coil structures.

Resonant circuit

The use of parallel or series resonant circuits to drive the coils is well known in the art. For example, in a series resonant circuit, the impedances of the coil and capacitor are equal and opposite at resonance, so the total impedance of the circuit is minimal and the current flowing through the primary coil is maximal. The secondary device is also typically tuned to the operating frequency to maximize the induced voltage or current.

In some systems, such as power toothbrushes, there is typically a circuit that is detuned (tuned) when the secondary device is not present and tuned when the secondary device is in place. The presence of magnetic material in the secondary device changes the self-inductance of the primary device and causes the circuit to resonate. In other systems like passive radio tags, the secondary device has no magnetic material and therefore does not affect the resonant frequency of the system. These tags are typically small and remote to the primary device so that the inductance of the primary device does not change significantly, even in the presence of magnetic material.

In the proposed system, this is not the case:

high permeability magnetic material may be present in the secondary device and used in close proximity to the primary device;

one or more secondary devices may be in close proximity to the primary device at the same time.

This has the effect of significantly changing the inductance of the primary device and varying the levels according to the number of secondary devices present on the mat. When the inductance of the primary is changed, the capacitance required by the circuit to resonate at a particular frequency changes. There are three ways to keep the circuit in resonance:

dynamically varying the operating frequency by means of a control system;

dynamically varying the capacitance by means of a control system so that resonance occurs at a predetermined frequency;

by means of a low Q system, the system remains resonant in the inductive range.

A problem with varying the operating frequency is that the secondary device is typically configured to resonate at a predetermined frequency. If the operating frequency changes, the secondary device will be detuned. To overcome this problem, the capacitance can be changed without changing the operating frequency. The secondary device may be designed such that each additional device placed close to the primary device will change the inductance to a quantum level, while an appropriate capacitor is switched in to resonate the circuit at a predetermined frequency. Due to this change of the resonance frequency, the number of devices on the charging surface can be detected and the primary unit can also sense when something is close to or far from the charging surface. If a magnetically permeable object is placed near the charging surface in addition to a secondary slave device, it is unlikely that the system will change to the predetermined quantum level. In this case, the system can automatically detune and reduce the current flowing into the coil.

Drawings

For a better understanding of the present invention, and to show how it may be carried into effect, reference will now be made, by way of example only, to the accompanying drawings in which:

FIG. 1 illustrates the magnetic design of a typical prior art contactless power transfer system that requires precise alignment of the primary and secondary devices;

FIG. 2a shows the magnetic design of another typical prior art contactless power transfer system, which includes one large coil in the primary;

FIG. 2b shows a non-uniform field distribution inside a large coil at 5mm from the coil plane, with a minimum amount in the center;

FIG. 3 shows a multi-coil system in which each coil is driven independently to produce a localized field;

fig. 4a shows an embodiment of the proposed system, which shows a substantial difference from the prior art, in which no secondary device is included;

fig. 4b shows an embodiment of the proposed system with two secondary devices;

fig. 4c shows a cross section of the active area of the primary unit, and the equipotential lines of the magnetic flux density generated by the wire;

fig. 4d shows the magnetic circuit of this particular embodiment of the proposed invention;

FIG. 5 shows a schematic diagram of an embodiment of a primary device and a secondary device;

fig. 6a to 6l show the design of some alternative embodiments of the field generating means or parts of the field generating means of the primary apparatus;

figures 7a and 7b show some possible designs of the magnetic means of the secondary device;

FIG. 8 illustrates the effect of the flux guide (the thickness of the flux guide is exaggerated for clarity);

FIG. 8a shows that without flux-guiding, the field tends to spread into the air directly above the active area;

FIG. 8b shows the direction of current flow in the wire in this particular embodiment;

fig. 8c shows that when the magnetic material is placed on top of the charging area, the flux guide contains magnetic field lines inside it;

FIG. 8d shows the secondary device on top of the primary device;

fig. 8e shows a cross section of a primary unit without any secondary unit;

figure 8f shows a cross-section of a primary device with a secondary device on top and shows the effect of using a magnetic core with a secondary device having a higher magnetic permeability than the magnetic permeability;

FIG. 9a shows a specific coil arrangement with net instantaneous current indicated by the direction of the arrows;

FIG. 9b shows a similar coil arrangement to FIG. 9a except that it is rotated 90 degrees;

fig. 9c shows the charging area of the primary device when the coil of fig. 9a is placed on top of fig. 9 b. If the coil in FIG. 9a is driven a quarter cycle away from the coil in FIG. 9b, this figure shows the effect of the rotating magnetic dipole;

FIG. 10 shows the case where the secondary device has a degree of rotation about an axis;

FIG. 11 shows a different arrangement of a secondary device with a degree of rotation about an axis;

fig. 12a and 12b show a further embodiment of a coil arrangement of the type shown in fig. 9a and 9 b; and

fig. 13 shows a simple embodiment of the electronics of the drive device.

Detailed Description

Referring first to fig. 1, two examples of prior art contactless power transfer systems are shown, both of which require precise alignment of the primary and secondary devices. This embodiment is typically used for a charger for an electric toothbrush or a mobile phone.

Fig. 1a shows a primary magnetic device 100 and a secondary magnetic device 200. On the primary magnetic means side, a coil 110 is wound on a core 120 such as ferrite. Likewise, the secondary side is constituted by a coil 210 wound around another magnetic core 220. In operation, an alternating current flows into the primary coil 110 and generates magnetic flux (flux) 1. When the secondary magnetic means 200 is positioned such that it is axially aligned with the primary magnetic means 100, the magnetic field lines 1 will couple from the primary magnetic means into the secondary magnetic means, inducing a voltage on the secondary coil 210.

Fig. 1b shows a split transformer. The primary magnetic device 300 is composed of a U-shaped magnetic core 320 wound with a coil 310. When an alternating current flows into the primary coil 310, a varying magnetic field line 1 is generated. The secondary magnetic means 400 is constituted by a second U-shaped magnetic core 420 wound with another coil 410. When the secondary magnetic means 400 is placed on the primary magnetic means 300 with the arms of the two U-shaped cores in line, the magnetic field lines will couple efficiently into the secondary U-shaped core 420 and induce a voltage on the secondary winding 410.

Fig. 2a is another embodiment of a prior art induction system that is typically used to power radio frequency passive tags. The primary device is typically formed by a coil 510 covering a large area. When a plurality of secondary devices 520 are within the area surrounded by the primary coil 510, an induced voltage will be generated in these devices. The system does not require precise alignment of the secondary coil 520 with the primary coil 510. Fig. 2b shows a graph of the magnitude of the magnetic flux intensity over the area surrounded by the primary coil 510 at 5mm above the plane of the primary coil. It shows a non-uniform field with a minimum 530 in the center of the primary coil 510.

Fig. 3 is another embodiment of a prior art induction system in which a multi-coil array is used. The primary magnetic means 600 is constituted by a coil array comprising coils 611, 612 and 613. Secondary magnetic device 700 may be comprised of coil 710. When the secondary magnetic device 700 is in proximity to some of the coils of the primary magnetic device 600, coils 611 and 612 are activated, while others, such as 613, are inactive. The activated coils 611 and 612 generate magnetic field lines, part of which will couple into the secondary magnetic means 700.

Fig. 4 shows an embodiment of the proposed invention. Fig. 4a shows a primary coil 710 wound or printed in such a way that there is a net instantaneous current in the active area 740. For example, if a direct current flows through the primary coil 710, the wires within the active area 740 will all have current flowing in the same direction. The current flowing through the primary coil 710 generates magnetic field lines 1. A layer of magnetic material 730 is present under the charging region to provide a return path for the magnetic field lines. Fig. 4b shows the same primary magnetic arrangement as shown in fig. 4a with two secondary arrangements 800. When the secondary device 800 is placed over the charging area 740 of the primary magnetic device in the correct orientation, magnetic flux 1 will flow through the magnetic core of the secondary device 800, not through air. Thus, the magnetic field lines 1 flowing through the secondary magnetic core will induce a current in the secondary coil.

Fig. 4c shows some equipotential lines of the magnetic flux density of the magnetic field generated by the conducting wires 711 within the charging area 740 of the primary magnetic means. A layer of magnetic material 730 is present under the conductive lines to provide a low reluctance return path for the magnetic field lines.

Fig. 4d shows a cross section of the charging area 740 of the primary magnetic means. One possible path of the magnetic circuit is shown. The magnetic material 730 provides a low reluctance path for the circuit and the core 820 of the secondary magnetic device 800 also provides a low reluctance path. This greatly reduces the distance the flux lines must travel through the air, thus minimizing leakage.

Fig. 5 shows a schematic view of an embodiment of the overall system of the proposed invention. In this embodiment, the primary unit is comprised of a power source 760, a control unit 770, a sensing unit 780 and an electromagnetic unit 700. The power supply 760 converts the supply voltage (or other power source) into direct current at a voltage suitable for the system. The control unit 770 controls the driving unit 790 that drives the magnetic device 700. In this embodiment the magnetic means are constituted by two separate drive components, a coil 1 and a coil 2. The coil 1 and the coil 2 are arranged such that the conductors in the charging region of the coil 1 are perpendicular to the conductors in the charging region of the coil 2. When the primary unit is activated, the control unit causes a phase shift of 90 degrees between the alternating currents flowing through coils 1 and 2. This creates a rotating magnetic dipole on the surface of the primary magnetic device 700, enabling the secondary device to receive power regardless of the direction of rotation (see fig. 9). In a standby mode, where no secondary device is present, the primary device is detuned and the current flowing into the magnetic device 700 is minimized. When the secondary device is placed on top of the charging area of the primary device, the inductance of the primary magnetic device 700 changes. This causes the primary circuit to resonate and the current becomes maximum. When there are two secondary devices on the primary device, the inductance is changed to another level and the primary circuit is detuned again. At this point, the control 770 uses feedback from the sensing device 780 to switch another capacitor into the circuit so that the circuit is tuned again and the current becomes maximum. In this embodiment, the secondary unit has a standard size, and up to six standard sizes of equipment may receive power from the primary unit simultaneously. Due to the standard size of the secondary device, the change in inductance due to changes in the adjacent secondary device is quantified to a number of predetermined levels, such that only up to six capacitances are required to maintain resonant operation of the system.

Fig. 6a to 6l show various exemplary embodiments of a coil component of a primary magnet arrangement. These embodiments may be implemented as coil components of the primary magnetic means only, in which case the rotation of the secondary means is critical for the transfer of electrical energy. These embodiments may also be implemented in combination, without excluding embodiments not shown here. For example, the two coils shown in FIG. 6a may be placed at 90 degrees to each other to form a single magnetic device. In fig. 6 a-6 e, charging area 740 is comprised of a series of wires with net current flow generally in the same direction. In some configurations, such as fig. 6c, there is no substantial coupling and therefore no electrical energy transfer when the secondary device is placed directly in the center of the coil. In fig. 6d, there is also no substantial coupling when the secondary device is located in the gap between the two charging regions 740. Fig. 6f shows a special coil structure of the primary unit adapted to generate electromagnetic field lines substantially parallel to the surface of the primary unit in the charging area 740. Two primary windings 710 on either side of a charging region 740 are formed around opposite arms of a generally rectangular flux guide 750 of magnetic material, the primary windings 710 generating opposing electromagnetic fields. The flux guide 750 contains the electromagnetic field and creates a magnetic dipole in the charging region 740 in the direction of the arrow shown in the figure. When the secondary device is placed in the charging region 740 in a predetermined orientation, a path of low reluctance is created and magnetic flux flows through the secondary device, thereby creating efficient coupling and transfer of electrical energy. It should be appreciated that the flux guide 750 need not be continuous, but may in fact be formed as two opposing unconnected horseshoe members.

Fig. 6g shows another possible coil structure of the primary device, which is adapted to generate electromagnetic field lines substantially parallel to a charging surface of the primary device within a charging area 740. Primary winding 710 is wound on a core 750, which may be ferrite or some other suitable material. Charging area 740 includes a series of wires having a net current flow generally in the same direction. The coil structure of fig. 6g can actually support or define a charging area 740 both above and below that shown in the drawing, and depending on the design of the primary device, one or both of the charging areas can be used for the secondary device.

Fig. 6h shows a variation of the structure of fig. 6 g. Unlike primary windings 710 being evenly spaced as in fig. 6g, windings 710 are not evenly spaced. The intervals and variations shown in this figure may be selected or designed to improve the performance balance or field strength level balance across the charging region 740.

Fig. 6i shows an embodiment in which the two primary windings 710 shown in fig. 6g are in a mutually orthogonal configuration such that the direction of the field lines can be dynamically switched or rotated to other orientations about the plane of the charging surface.

Fig. 6j and 6k show an additional dual coil structure of the primary unit, which is not a simple geometry with substantially parallel wires.

In fig. 6j, line 710 represents one of a set of current carrying wires placed in the plane of the charging surface 600. The main conductor 710 is of an arbitrary shape, and does not have to be a regular pattern, and in fact, the conductor 710 may have a straight portion and a curved portion, and may cross itself. One or more of the auxiliary conductors 719 are arranged beside the main conductor 710 and generally parallel thereto (at any particular local point), only two of the auxiliary conductors 719 being shown here for clarity. The current in the auxiliary conductor 719 has the same direction as the current in the main conductor 710. The auxiliary conductors 719 may be connected in series or in parallel to form a single coil arrangement.

In fig. 6k, a set of current carrying wires 720 (only two of which are shown here for clarity) is arranged in the plane of the charging surface 600. The main conductors 710 are arranged as in fig. 6j, each conductor 720 being arranged so as to be locally orthogonal to the main conductors 710. The wires 720 may be connected in series or in parallel to form a single coil arrangement. If a first sinusoidal current is delivered into wire 710 and a second sinusoidal current, 90 degrees phase shifted with respect to the first current, is delivered into coil 720, then by varying the relative proportions and signs of the two currents, it will be seen that the direction of the electromagnetic field vector generated at most points on charging region 740 will be rotated 360 degrees.

Fig. 6l shows another alternative arrangement in which the core 750 is in the shape of a disc with a through hole in the centre. A first set of current carrying wires 710 are arranged in a spiral shape on the surface of the disc. The second set of wires 720 is wound radially around the periphery and through the center of the disk in the form of a coil. These wires may be driven in such a way, for example, with orthogonal sinusoidal currents, that the secondary device will not detect zero voltage when placed at any point of the charging area 740 and rotated about an axis perpendicular to the charging area.

Fig. 7a and 7b are embodiments of the proposed secondary device. Winding 810 is wound on core 820. The two secondary devices may be combined into a single secondary device, for example at right angles, so that the secondary device can be effectively coupled with the primary device in all rotations. These secondary devices may also be combined with standard coils, such as coil 520 shown in fig. 2a, to eliminate dead zones.

Fig. 8 shows the effect of the flux guide 750 on top of the charging area. The thickness of the material is exaggerated for clarity, but in practice it is in the order of millimeters. The flux guide 750 will minimize leakage and contain the magnetic field lines by reducing the amount of magnetic field lines coupled to the secondary device. In fig. 8a, the primary magnetic arrangement is shown without flux-guide 750. The field will be dispersed into the air directly above the charging area. As shown in fig. 8b to 8f, the leakage is minimized because the flux lines are contained within the plane of the material due to the flux guide 750. In fig. 8e, the magnetic flux lines remain within the magnetic conductor 750 when there is no secondary device 800 on top. In fig. 8f, when there is a secondary device 800 with a core of a material with a higher magnetic permeability, part of the magnetic flux will flow through the secondary device. The permeability of flux guide 750 may be selected to be higher than typical metals such as steel. When other material, such as steel, is placed on top, it is not part of the secondary device and most of the magnetic field lines will remain within the flux guide 750, rather than passing through the object. The flux guide 750 may not be a continuous layer of magnetic material, but may have a small air gap between them to encourage more flux to flow into the secondary device 800 (if the secondary device 800 is present).

Fig. 9 shows an embodiment of a primary device using more than one coil. Fig. 9a shows a coil 710 and a charging area 740 with current flowing in a direction parallel to arrow 2. Fig. 9b shows a similar coil arranged at 90 degrees to the coil in fig. 9 a. When the two coils are placed on top of each other such that the charging area 740 overlaps, the charging area will be as shown in fig. 9 c. Such an embodiment would allow the secondary device to rotate arbitrarily and couple efficiently on top of the primary device.

Fig. 10 shows an embodiment in which the secondary device has a degree of rotation about an axis, wherein the secondary device is a battery cell or has battery cells embedded therein. In this embodiment, the secondary device may be configured so that it couples with the main magnet flux during any axial rotation (rA) relative to the primary device (910), and with the same degrees of freedom described above (i.e. translation in the (X, Y) plane and arbitrary rotation about (rZ) perpendicular to the primary device plane).

Fig. 11a shows an arrangement in which a rechargeable battery cell 930 is wrapped by an optional cylindrical flux concentrating device 931, the latter being wound with copper wire 932. The cylindrical device may be long or short relative to the length of the battery.

Fig. 11b shows another arrangement in which the magnetic field line concentration device 931 covers only a portion of the battery 930 and is wound with copper wire 932 (but not the battery). The device and copper wire may conform to the surface of the battery. Their area may be large or small relative to the perimeter of the cell and their length may be long or short relative to the length of the cell.

Fig. 11c shows another arrangement in which a magnetic flux concentrating device 931 is embedded within a battery 930 and wound with copper wire 932. The device may be substantially flat, cylindrical, rod-like, or any other shape, with a width that may be greater or lesser relative to the diameter of the cell and a length that may be greater or lesser relative to the length of the cell.

In any of the cases shown in fig. 10 and 11, these flux-gathering devices may also be a functional part of the battery enclosure (e.g., the outer zinc electrode), or of the battery itself (e.g., the inner electrode).

In either case shown in fig. 10 and 11, the electrical energy may be stored in a smaller standard battery (e.g., AAA size) mounted in a larger standard battery housing (e.g., AA).

Fig. 12 shows an embodiment of a primary unit similar to that shown in fig. 9. Fig. 12a shows a coil generating a field horizontal to the page. Fig. 12b shows another coil generating a field perpendicular to the page, the two coils being arranged in a substantially coplanar manner, possibly one on top of the other, or even being wound around each other in some way. The wires associated with each coil are shown at 940 and the charging area is represented by arrows 941.

Fig. 13 shows a simple embodiment of the drive means (790 of fig. 5). In this embodiment there is no control means. The PIC processor 960 produces two 23.8kHz square waves 90 degrees in phase. These square waves are amplified by a block 961 and driven into two coil blocks 962, which are identical to the magnetic device shown in fig. 12a and 12 b. Although the drive means is used to provide a square wave, the high resonance "Q" of the magnetic means converts the square wave into a sinusoidal waveform.

The preferred features of the invention are applicable to all aspects of the invention and may be used in any possible combination.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the claims of the present invention.

Claims (66)

1. A primary unit having a power transfer region in or on which a secondary device separate from the primary unit can be placed into a fixed operating configuration to receive power from the primary unit without requiring direct electrically conductive contact between the primary unit and the secondary device, the primary unit comprising:

a first field generating device and a second field generating device, each arranged substantially parallel to the power transfer region, and each configured such that: each device, if driven individually, produces an electromagnetic field having field lines extending generally in a predetermined direction through at least a portion of the electrical energy transmission region, and having significant resolved components parallel to the electrical energy transmission region, the predetermined direction of the first field generating device being different from the predetermined direction of the second field generating device; and

drive means for providing an electrical drive signal to said first and second field generating means such that said first and second field generating means cooperatively generate field lines in or on at least a portion of said electrical energy transmission region, said field lines changing direction over time when resolved onto said electrical energy transmission region.

2. A primary unit as claimed in claim 1, wherein the drive means is for providing an electrical drive signal to the first and second field generating means to cause the field lines to switch in two or more different predetermined directions over time.

3. A primary unit as claimed in claim 1, wherein the drive means is arranged to provide an electrical drive signal to the first and second field generating means to cause the field line directions to rotate through an angle over time.

4. A primary unit as claimed in claim 1, wherein the drive means is arranged to provide an electrical drive signal to the first and second field generating means to cause the field line directions to rotate one full circle over time.

5. The primary unit of any preceding claim, wherein:

the first field generating device comprises at least one first conductive element;

the second field generating means comprises at least one second conductor;

the first conductive member extends substantially perpendicular to the second conductive member.

6. The primary unit of claim 5, wherein:

the first and second conductive elements are arranged in a generation region located in the electrical energy transmission region or arranged in a generation region parallel to the electrical energy transmission region; and

the first and second conductive members are formed and configured such that: at each intersection point where the first conductive member extends through the second conductive member, the first and second conductive members extend in mutually orthogonal directions.

7. The primary unit of claim 6, wherein the first field generating means comprises a plurality of first conductors extending generally parallel to each other and perpendicular to the predetermined direction of the first field generating means, and the second field generating means comprises a plurality of second conductors extending generally parallel to each other and perpendicular to the predetermined direction of the second field generating means.

8. A primary unit as claimed in claim 7, wherein the drive means is arranged to cause current to flow in the same direction through all of the first conductors simultaneously and to cause current to flow in the same direction through all of the second conductors simultaneously.

9. The primary unit of any one of claims 5 to 8, further comprising a magnetic core through which the first and second conductors extend.

10. A primary unit as claimed in any one of claims 5 to 9, wherein each first and/or second conductor is straight.

11. A primary unit as claimed in any one of claims 5 to 9, wherein each first and/or second conductor is not straight.

12. A primary unit as claimed in any one of claims 5 to 9, wherein each of the first conductors is in the form of a loop, and each of the second conductors extends transversely across at least one of the first conductors at a different location around the loop.

13. The primary unit of claim 12 wherein at least one of the second conductors extends laterally across two or more of the first conductors.

14. The primary unit of claim 12 or 13 wherein the loop is generally circular and the second conductor extends radially through the first conductor of the circular ring at different locations around the first conductor of the circular ring.

15. The primary unit of claim 12 or 13 wherein the loop is an irregular loop and each of the second conductors is locally substantially perpendicular to each of the first conductors.

16. A primary unit as claimed in any one of claims 5 to 15, comprising at least a first coil and a second coil, the first conductor being provided by a different part of the first coil and the second conductor being provided by a different part of the second coil.

17. The primary unit of claim 16 wherein each said coil is wound around a magnetic core.

18. A primary unit as claimed in claim 16 or 17, wherein the first coil has a substantially flat spiral shape and the second coil is wound in a toroidal shape through the centre of the first coil and radially out of the periphery of the first coil.

19. The primary unit of any one of claims 5 to 18 wherein the first and second conductors are conductive traces formed on a planar surface.

20. The primary unit of claim 19 wherein the first conductive member is a conductive trace formed on a first plane and the second conductive member is a conductive trace formed on a second plane substantially parallel to the first plane.

21. A primary unit as claimed in any one of claims 5 to 20, wherein the drive means is arranged to alternately provide an electrical drive signal to the first and second field generating means.

22. A primary unit as claimed in any one of claims 5 to 20, wherein the drive means is for providing electrical drive signals to the first and second field generating means in quadrature.

23. A primary unit as claimed in any preceding claim, wherein at any given moment the field lines are substantially parallel to each other across the power transfer region.

24. A primary unit as claimed in any one of claims 1 to 22, wherein the field lines have resolved components which, in or parallel to a plane on the power transfer face, are substantially parallel to one another in the power transfer region at any given moment.

25. A primary unit as claimed in any preceding claim, wherein the field lines are substantially parallel to the power transmission plane in the power transmission region.

26. The primary unit of any one of claims 1 to 24 wherein the field lines have a significant resolved component parallel to the electrical energy transmission plane in the electrical energy transmission region.

27. A primary unit as claimed in any preceding claim, comprising a power transfer face configured to support the secondary device in its said operating configuration when placed in or on the power transfer region.

28. The primary unit of claim 27 wherein the height of the first and second field generating devices, measured in a direction substantially perpendicular to the power transfer region, is less than the width or length of the perimeter of the power transfer region.

29. The primary unit of claim 28 wherein said height is no greater than one-half of the length or one-half of the width of said perimeter.

30. The primary unit of claim 28 wherein said height is no greater than 1/5 for a length or 1/5 for a width of said perimeter.

31. The primary unit of claim 27 wherein said primary unit is in the form of a flat platform having a major face providing said electrical energy transmission face.

32. The primary unit of claim 27 wherein the power transfer surface is substantially flat.

33. The primary unit of claim 27 wherein the power transmission surface is curved.

34. The primary unit of claim 27 wherein said first and second field-generating devices do not extend beyond said electrical energy transfer surface.

35. A system for transferring electrical energy without the need for direct electrically conductive contact, comprising:

a primary unit as claimed in any one of claims 1 to 26; and

a secondary device, separate from the primary unit, comprising at least one conductor with which an electromagnetic field generated by the primary unit couples and induces a current to flow in the conductor when the secondary device is placed in the operating configuration in the power transfer region.

36. The system of claim 35, comprising a power transfer surface configured to support the secondary device in its operating configuration when the secondary device is placed into the power transfer region of the primary unit.

37. The system of claim 35 or 36, wherein the secondary device is loaded into or by an object requiring electrical energy, the secondary device being able to receive electrical energy from the primary unit when the object is placed on or near the electrical energy transmission face such that the loaded secondary device has its said operating configuration.

38. The system of claim 37, wherein the object comprises at least one battery or cell, the secondary device is in the form of a flat adapter that fits over the battery or cell with thin electrodes that can be inserted between terminals of the battery or cell and terminals of the object.

39. A system according to claim 35 or 36, wherein the secondary device is loaded into or by a rechargeable battery or cell fitted or adapted to be fitted into an object requiring electrical energy.

40. The system of claim 39, wherein when the battery or cell is fitted into the object and the object is placed on or near the power delivery surface such that the secondary device has its operating configuration, the battery or cell can be recharged without removing the battery or cell from the object.

41. The system of claim 39 or 40, wherein the rechargeable battery or cell is an industry standard sized battery or cell.

42. The system of claim 39 or 40, wherein the size and/or shape of the rechargeable battery or cell is application specific or customized for a particular application.

43. The system of claim 39, 40, 41 or 42, wherein the rechargeable battery or cell further comprises an energy storage device and an electrical energy conversion device for converting electrical energy inductively received by the secondary device into a form suitable for transmission to the exterior of the battery or cell through its external electrical connection, or into a form suitable for recharging the energy storage device, or both.

44. The system of claim 40, wherein the rechargeable battery or cell further comprises an energy storage device and an electrical energy conversion device for converting electrical energy inductively received by the secondary device into a form suitable for transmission to the outside of the battery or cell through its external electrical connection, or into a form suitable for recharging the energy storage device, or both, wherein the rechargeable battery or cell has a charge control device adapted to meter the inductively received electrical energy supplied to the external electrical connection and to the energy storage device when the secondary device inductively receives electrical energy.

45. The system of any one of claims 39 to 44, wherein the rechargeable battery or cell further comprises a magnetic flux concentration device around which the at least one conductor is wound.

46. The system of claim 45, wherein the magnetic flux gathering device is at least partially wound around a middle portion of the battery or battery cell.

47. The system of any one of claims 37 to 46, wherein the object is portable.

48. The system of any one of claims 37 to 47, wherein the object is a portable electrical or electronic device.

49. The system of any one of claims 37 to 48, wherein the object is a mobile communication device.

50. A system according to any one of claims 37 to 49, wherein the power transfer region is large enough to accommodate two or more such secondary devices simultaneously, loaded into or by different respective such objects.

51. The system of any one of claims 37 to 50, wherein the primary unit is part of a housing of the object.

52. The system of any one of claims 36 to 51, wherein the primary unit is integrated into a component of furniture having a surface for providing the electrical energy transmission face.

53. The system of any of claims 35 to 52, wherein the power transfer area is large enough to encompass a footprint area of the secondary device in more than one position and/or orientation in which the secondary device may be placed, the footprint area being an area parallel to the power transfer face occupied by the at least one conductor and/or by a magnetic core of the secondary device when the secondary device is in its operating configuration.

54. The system of claim 53, wherein the power transfer area is large enough to encompass the footprint area of the secondary device in any of the orientations.

55. The system of any one of claims 36 to 54, wherein the secondary device comprises a coil providing the at least one conductor, the coil being arranged such that a central axis of the coil is not substantially perpendicular to the electrical energy transfer area with the secondary device in its operating configuration.

56. The system of claim 55 wherein the central axis is substantially parallel to the power transfer region with the secondary device in its operating configuration.

57. The system of any one of claims 35 to 56, wherein the at least one conductor in the secondary device is wound around a magnetic core for concentrating magnetic flux therein, and the magnetic core is arranged such that its longitudinal axis is substantially non-perpendicular to the electrical energy transmission area with the secondary device in its operating configuration.

58. The system of claim 57, wherein the longitudinal axis is substantially parallel to the power transfer region with the secondary device in its operating configuration.

59. The system of claim 36, wherein the first and second field generating devices have a height, measured in a direction substantially perpendicular to the power transfer region, that is less than a width or length of the perimeter of the power transfer region.

60. The system of claim 59, wherein the height is no greater than half of the length or half of the width of the perimeter.

61. The system of claim 59, wherein the height is no greater than 1/5 for the length of the perimeter or 1/5 for the width.

62. The system of claim 36, wherein the primary unit is in the form of a flat platform having a major face providing the electrical energy transmission face.

63. The system of claim 36 wherein the power transfer surface is substantially flat.

64. The system of claim 36 wherein the power delivery surface is curved.

65. The system of claim 36, wherein the first and second field generating devices do not extend beyond the electrical energy delivery surface.

66. A method of transferring electrical energy from a primary unit to a secondary device separate from the primary unit without requiring direct electrically conductive contact between the primary unit and the secondary device, the method comprising the steps of:

generating an electromagnetic field with first and second field generating devices, the electromagnetic field passing through an electrical energy transfer region, placing the secondary device in or on the electrical energy transfer region in a fixed operating configuration to receive electrical energy from the primary unit, each of the first and second field generating devices being configured substantially parallel to the electrical energy transfer region and each being configured to: each device, if driven individually, produces an electromagnetic field having field lines extending generally in a predetermined direction through at least a portion of the electrical energy transmission region, and having significant resolved components parallel to the electrical energy transmission region, the predetermined direction of the first field generating device being different from the predetermined direction of the second field generating device; and

providing an electrical drive signal to the first and second field generating means such that the first and second field generating means cooperatively generate field lines in or on at least a portion of the electrical energy transmission region that change direction over time when resolved onto the electrical energy transmission region.