Magnetic coupling structure

Abstract

In one example aspect, a magnetic coupling structure comprises: a plurality of coils arranged clear of an axis in respective radial directions, with each coil having radially spaced inner and outer segments that overlap a next coil at a first side to substantially decouple therefrom. In one example aspect, a magnetic coupling structure comprises: a coil having radially spaced inner and outer segments partially surrounding an axis, and two intermediate segments interconnecting the inner and outer segments; and an additional coil surrounding the axis, bounded by the outer segment and overlapping the intermediate segments to decouple from the coil. In one example aspect, a magnetic coupling structure comprises: a first coil having radially spaced inner and outer segments staggered about an axis; and a second coil having radially spaced inner and outer segments staggered about the axis and overlapping those of the first coil to decouple from the first coil.

Description

Magnetic coupling structureTECHNICAL FIELD

[0001] The present disclosure generally relates to structures for magnetic coupling used in wireless power charging, particularly for loosely coupled or resonant wireless power transfer. In part it relates to a magnetic coupling structure with decoupled coils and methods of positioning the coils to achieve minimal or no mutual coupling.BACKGROUND

[0002] Magnetic coupling structures improve coupling profiles for wireless power transfer. By designing a magnetic coupling structure (also referred to as a pad) the efficiency and / or ease of wireless power transfer can be improved.

[0003] Mutual decoupling removes all or substantially all coupling between the coils. This allows the coils to act independently, with the current and / or voltage in one coil not affecting the other coils on the pad. However, it is difficult to mutually decouple coils. US11581124 teaches how to decouple two, three, and four coil systems with circular coils. For example, a bipolar pad uses the overlap between two neighbouring coils to offset flux transfer to and from the neighbouring coils. By adjusting the overlap carefully, the flux into and out of each coil is balanced such that the coils are decoupled. In some cases, the overlap is adjusted with consideration the presence of magnetically permeable material (such as ferrite). This is because the magnetically permeable material will affect the coupling and decoupling. Similarly, the presence of a second magnetic coupling structure (i.e., a corresponding transmitter or receiver) may require a change in the overlap to reduce coupling.

[0004] US11581124 and US10958111 show mutually decoupled coil structures with three and four coil examples. In each case the overlap is controlled between each of the coils to balance the flux between each pair of the three coils, and therefore the coupling structure overall. However, the arrangements used require specific alignment or operation to mutually decoupled and / or use of dipole coils.

[0005] It is the intention of the present invention to describe a magnetic coupling structure that substantially mitigates at least one of the above limitations, or at least provides the public with a choice.SUMMARY

[0006] The present disclosure shows a converter for a magnetic coupling structure that mutually decouples the coils and / or provides a low height structure.

[0007] In a first aspect the disclosure may broadly be said to consist in a magnetic coupling structure comprising: a loop coil, the loop coil forming a loop, at least two further coils, the at least two further coils concave and comprising: an inner portion within or overlapping with the loop and substantially parallel the loop coil, and an outer portion outside of the loop, wherein the loop coil and the two further coils are mutually decoupled.

[0008] In an aspect the disclosure may broadly be said to consist in a magnetic coupling structure comprising: a loop coil, the loop coil forming a loop, at least two further coils, the at least two further coils each comprising: an inner portion within or overlapping with the loop, and an outer portion outside of the loop.

[0009] Optionally the loop coil loops about a centre of the magnetic coupling structure.

[0010] Optionally the at least two further coils and the loop coil are mutually decoupled. Optionally the at least two further coils are concave. Optionally a concave portion of each of the at least two further coils is on the inner portion of the at least two further coils. Optionally the at least two further coils each comprise a recess. Optionally the recess is on the inner portion. Optionally the at least two further coils overlap.

[0011] Optionally each inner portion of the at least two further coils are the same shape as a corresponding portion of the loop coil. Optionally the inner portion of each of the at least two further coils is a parallel curve to a corresponding portion of the loop coil. Optionally the inner portion of each of the at least two further coils is parallel to a corresponding portion of the loop coil. Optionally the corresponding portion is the portion of the loop coil between the inner portion and the outer portion of the further coils.

[0012] Optionally the inner portion of each of the at least two further coils is concentric with the loop coil. Optionally the inner portion and outer portion of each of the at least two further coils are concentric.

[0013] Optionally the inner portion and outer portion are connected by connecting portions. Optionally the connecting portions are substantially radial. Optionally the connecting portions of neighbouring further coils are overlapped. Optionally the overlap of the connecting portions creates a space between the neighbouring connecting portions. Optionally the at least two further coils comprise three coils. Optionally the magnetic coupling structure consists of theloop coil and consists of three further coils. Optionally the at least two further coils consist of two or three coils.

[0014] Optionally the combination of the inner portions forms a substantially continuous inner loop. Optionally the combination of the outer portions forms a substantially continuous outer loop. Optionally the outer portions overlap to form the substantially continuous outer loop.

[0015] Optionally each of the at least two further coils I is a serpentine coil. Optionally each serpentine coil crosses the loop coil a plurality of times. Optionally comprising a return coil opposing the serpentine coils. Optionally consisting of two serpentine coils. Optionally the serpentine coils cross the loop coil at offset locations. Optionally the offset locations mutually decouple the serpentine coils.

[0016] Optionally each of the at least two further coils are substantially the same. Optionally the at least two further coils form annular sectors, with a sector centre determined at the apex of the sector, wherein a centre of the loop coil and the sector centre are the same. Optionally the annular sectors overlap. Optionally the annular sectors extend around the loop coil. Optionally each of the at least two further coils have different sector angles. Optionally the loop coil and the at least two further coils are interleaved to reduce the overall height of the coils.

[0017] Optionally each of the loop coils and at least two further coils are configured to be independently controlled. Optionally the at least two further coil extend substantially about the inner perimeter of the loop coil. Optionally the loop coil is a polygon loop, a square loop, or circular loop. Optionally the loop coil extends over the inner portions of the at least two further coils. Optionally the loop coil is within the outer portion of the at least two further coils. Optionally comprising a magnetically permeable material layer behind the loop coil and the at least two further coils.

[0018] Optionally comprising a shield layer behind the loop coil and one or more further coils. Optionally the shield layer is behind the magnetically permeable material layer. Optionally the magnetic coupling structure is one or more of a power transmitting pad, a power receiving pad and a power transceiving pad (or a primary or secondary pad).

[0019] In a further aspect the disclosure may broadly be said to consist in a magnetic coupling structure comprising three coils, each coil comprising concentric inner portions and outer portions connected by connecting portions, wherein the connecting portions of each pair of coils overlap to create inner and outer curves.

[0020] Optionally comprising at least three coils. Optionally comprising a loop coil, the loop coil within the outer loop. Optionally the inner portion and outer portions are substantially parallel. Optionally the inner and outer curves are inner and outer loops. Optionally the inner and outer curves are annular arcs. Optionally the inner and outer curves form sectors of an annulus. Optionally the inner and outer curves are inner and outer loops.

[0021] In a further aspect the disclosure may broadly be said to consist in a system comprising two magnetic coupling structures as herein described the magnetic coupling structures coupled to transmit power.

[0022] In a further aspect the disclosure may broadly be said to consist in a method comprising energizing one or more of the coils of the magnetic coupling structure as herein described

[0023] Optionally the one or more coils are energized independently.

[0024] In a further aspect the disclosure may broadly be said to consist in an electrical vehicle comprising the magnetic coupling structure as herein described.

[0025] In a further aspect the disclosure may broadly be said to consist in an electrical device comprising the magnetic coupling structure as herein described

[0026] Optionally the magnetic coupling structure is arranged on the base of the vehicle or device. Optionally the magnetic coupling structure is configured to charge a battery.

[0027] In a further aspect the disclosure may broadly be said to consist in a magnetic coupling structure comprising at least three coils overlapping with one another, the three coils arranged in in one or both of two layers.

[0028] Optionally the at least three coils comprise: a first coil, a second coil, and a third coil, wherein the first and second coils overlap at one or more first overlap locations and the first and third coils overlap at one or more second overlap locations and the second and third coils overlap at one or more third overlap locations, wherein each of the one or more first, second and third overlap locations are different.

[0029] Optionally one or more of the coils has an upper portion configured to overlie another of the three coils and a lower portion configured to underlie another of the three coils. Optionally the three coils comprise substantially a single layer of wire. Optionally the coils are overlapped such that there is minimal mutual coupling between each of the three coils. Optionally there is substantially no mutual coupling between the coils. Optionally the magnetic coupling structure is configured to concentrate the magnetic flux predominantly in a desired region of the magnetic coupling structure. Optionally the structure comprises a magneticallypermeable layer. Optionally the coils are arranged on a side of the magnetically permeable material layer.

[0030] Optionally the three coils are provided in a coil layer and the magnetically permeable material layer is provided in a separate layer. Optionally the coil layer comprises at least two layers of coil windings. Optionally the magnetically permeable layer extends beyond the periphery of the three coils Optionally each of the three coils has a substantially constant height across the magnetic coupling structure. Optionally the three coils combine to form a loop surrounding a centre of the magnetic coupling structure. Optionally one of the three coils forms a loop about a centre of the magnetic coupling structure. Optionally the other coils of the three coils comprise an inner portion within the loop coil, and an outer portion outside of the loop coil.

[0031] Optionally comprising a loop coil, the loop configured to overlay and / or underlay (or weave between) the three coils. Optionally the loop coil overlaps with the three coils. Optionally the loop coil overlays and underlays each of the three coils. Optionally the loop coil weaves between each of the three coils. Optionally loop coil overlaps with the three coils at loop overlap locations, each of the loop overlap locations different from the other overlap locations. Optionally each of the loop overlap locations are at different locations on the magnetic coupling structure.

[0032] Optionally each of the first, second and third coils comprises an inner portion and an outer portion, wherein the inner portions combine to form an inner loop and the outer portions of the at least two coils combine to form outer loop. Optionally the outer loop has a greater width than the inner loop. Optionally the inner and outer loop form concentric loops. Optionally the inner and outer loops are circular, square, polygonal, and / or rectangular. Optionally comprising an inner space within the inner loop.

[0033] Optionally comprising connecting portions of each of the three coils between the inner and outer loops. Optionally the connecting portions extend offset between the inner and outer loops offset from the radius on the magnetic coupling structure. Optionally the connecting portions of overlapping coils partially overlap. Optionally wherein the connecting portions of the a first of the three coils extend between the inner and outer loop after the overlap the first coil with the other of the three coils, such that the connecting portions of the first coil are closer to the centre of other coils than the first coil. Optionally the connecting portions of each of the three coils extend between the inner and outer loop after the overlap with the adjacent coils,such the respective connecting portions are closer to the centre of the respective adjacent coils than their coil. Optionally the connecting portions sit on the base of the magnetic coupling structure.

[0034] Optionally the loop coil is positioned between the inner and outer loop. Optionally the loop coil substantially spans the distance between the inner and outer loop Optionally the loop coil is arranged within the height of the three coils. Optionally the a first of the three coils overlies a second of the three coils and underlays a third of the three coils. Optionally each of the three coils overlies one of the other three coils and underlays the other of the three coils. Optionally the height of the three coils on the magnetic coupling structure is less than the sum of the heights of the three coils. Optionally a second and third coils of the three coils form serpentine paths along a first of the three coils. Optionally the first coil is a loop coil. Optionally the second and third coils cross the first coil substantially perpendicularly. Optionally the first coil forms a substantially symmetrical loop. Optionally the loop is square and / or circular. Optionally the second and third coils cross the first coil in separate locations. Optionally the second and third coils overlap between each crossing of the first coil.

[0035] In a further aspect the disclosure may broadly be said to consist in a magnetic coupling structure for wireless power transfer, the magnetic coupling structure comprising: a first coil, a second coil, and a third coil, each of the first, second and third coils overlapping one another at at least one position, and wherein the first coil is configured to underlay the second coil at a first position and overlay the third coil at a second position such that the overall height of the first, second and third coils in the magnetic coils is less than the sum of the heights of the first second and third coils.

[0036] Optionally each of the first, second and third coils underlay at least one other coil and overlay at least one other coil.

[0037] In a further aspect the disclosure may broadly be said to consist in a magnetic coupling structure for wireless power transfer comprising: at least three overlapping coils, wherein the at least three coils are overlap one another such that the overall height of the three coils is less than the sum of the heights of the individual coils.

[0038] In a further aspect the disclosure may broadly be said to consist in a magnetic coupling structure for wireless power transfer comprising: at least two overlapping coils, wherein the at least two overlapping coils each comprising an inner portion and an outer portion, wherein theinner portions of the at least two coils combine to form an inner loop and the outer portions of the at least two coils combine to form outer loop.

[0039] Optionally comprising a further coil forming an intermediate loop between the inner loop and the outer loop. Optionally the further coil overlaps each of the at least two coils. Optionally the further coil overlaps and underlaps each of the at least two coils. Optionally the at least three coils overlap in each of the inner loop and the outer loop. Optionally the further coil passes across connecting portions of the at least two coils between the inner and outer portions. Optionally the further coil overlays a connecting portion adjacent to a connecting portion which the further coil underlays. Optionally the further coil overlays the inner loop.

[0040] In a further aspect the disclosure may broadly be said to consist in a magnetic coupling structure comprising three coils, each of the three coils overlapping with each of the other coils, wherein a maximum of two coils of the three coils overlap at any position on the magnetic coupling structure.

[0041] In a further aspect the disclosure may broadly be said to consist in a magnetic coupling structure comprising at least three coils wherein a maximum of one less that number of coils overlap at any position on the magnetic coupling structure.

[0042] In a further aspect the disclosure may broadly be said to consist in a magnetic coupling structure comprising: at least three coils, each of the at least three coils overlapping with each of the other at least three coils, wherein a maximum of two of the at least three coils overlap at any position on the magnetic coupling structure, and wherein the overall height of the at least three coils on the magnetic coupling structure is less than the sum of the heights of the individual at least three coils.

[0043] In a further aspect the disclosure may broadly be said to consist in a magnetic coupling structure comprising at least three coils, each of the at least three coils intersecting with at least two other coils of the other at least three coils, wherein the intersections occur at different positions about the magnetic coupling structure.

[0044] Optionally the height of the coils in the magnetic coupling structure is less than the sum of the height of the first, second and third coils.

[0045] In a further aspect the disclosure may broadly be said to consist in a magnetic coupling structure comprising: a first coil, a second coil, and a third coil, wherein the first and second coils overlap at one or more first overlap locations and the first and third coils overlap at one or more second overlap locations and the second and third coils overlap at one or more thirdoverlap locations, wherein each of the one or more first, second and third overlap locations are different.

[0046] In a further aspect the disclosure may broadly be said to consist in a magnetic coupling structure comprising three coils overlapping with one another, the three coils arranged in two layers.

[0047] In a further aspect the disclosure may broadly be said to consist in a magnetic coupling structure comprising three overlapping coils, the three coils arranged in a first and second layer: the first layer comprising a portion of at least two of the three coils; and the second layer comprising a portion of at least two of the three coils, wherein each of the portions of the coils in the first layer overlaps with portions of the other coils in second layer.

[0048] In a further aspect the disclosure may broadly be said to consist in a system comprising two magnetic coupling structures as described herein, the magnetic coupling structures coupled to transmit power.

[0049] In a further aspect the disclosure may broadly be said to consist in a method comprising energizing one or more of the coils of the magnetic coupling structures as described herein.

[0050] Optionally the one or more coils are energized independently.

[0051] In a further aspect the disclosure may broadly be said to consist in an electrical vehicle comprising the magnetic coupling structures described herein. In a further aspect the disclosure may broadly be said to consist in an electrical device comprising the magnetic coupling structures as described herein. Optionally the magnetic coupling structure is arranged on the base of the vehicle or device.

[0052] In a further aspect the disclosure may broadly be said to consist in a magnetic coupling structure comprising: at least one further coil, the at least one further coil comprising: an inner portion within or overlapping with the loop, and an outer portion outside of the loop. Optionally consisting in one further coil. Optionally the at least one further coil extends substantially about the inner perimeter of the loop coil. Optionally wherein the loop coil overlaps the inner portion of the at least one further coil. Optionally wherein the inner portion is concentric with the loop coil. Optionally comprising any of the features of the other magnetic coupling structures.

[0053] In a further aspect the disclosure may broadly be said to consist in a magnetic coupling structure comprising at least two overlapping coils, the at least two further coils comprising: an inner portion; and an outer portion substantially parallel with the inner portion. Optionallythe at least two coils are concave. Optionally the at least two coils form portions of an annulus. Optionally the inner portion comprises a recess. Optionally the inner portions form at least part of an inner loop, and the outer portions form at least part of an outer loop. Optionally the inner portions form an arc, and the outer portions form an arc. Optionally, the at least two coils are mutually decoupled. Optionally the inner portion and outer portion of each coil are connected by connecting portions. Optionally the connecting portions are overlapped. Optionally the overlap forms a space between adjacent connecting portions. Optionally comprising any of the features of the other magnetic coupling structures.

[0054] In a further aspect the disclosure may broadly be said to consist in a magnetic coupling structure comprising: a plurality of coils arranged clear of an axis in respective radial directions, with each coil having radially spaced inner and outer segments that overlap a next coil at a first side to substantially decouple therefrom.

[0055] In a further aspect the disclosure may broadly be said to consist in a magnetic coupling structure comprising: a coil having radially spaced inner and outer segments partially surrounding an axis, and two intermediate segments interconnecting the inner and outer segments; and an additional coil surrounding the axis, bounded by the outer segment and overlapping the intermediate segments to decouple from the coil.

[0056] In a further aspect the disclosure may broadly be said to consist in a magnetic coupling structure comprising: a first coil having radially spaced inner and outer segments staggered about an axis; and a second coil having radially spaced inner and outer segments staggered about the axis and overlapping those of the first coil to decouple from the first coil.

[0057] In a further aspect the disclosure may broadly be said to consist in a combination of the features of the magnetic coupling structures described herein.

[0058] Features from one or more embodiments or configurations may be combined with features of one or more other embodiments or configurations. Additionally, more than one embodiment or configuration may be used together in a structure or system.

[0059] As used herein the term "(s)" following a noun means the plural and / or singular form of that noun.

[0060] As used herein the term "and / or" means "and" or "or", or where the context allows both.

[0061] The term "comprising" as used in this specification means "consisting at least in part of". When interpreting each statement in this specification that includes the term "comprising",features other than that or those prefaced by the term may also be present. Related terms such as "comprise" and "comprises" are to be interpreted in the same manner.

[0062] It is intended that reference to a range of numbers disclosed herein (for example, 1 to 10) also incorporates reference to all rational numbers within that range (for example, 1, 1.1, 2, 3, 3.9, 4, 5, 6, 6.5, 7, 8, 9 and 10) and also any range of rational numbers within that range (for example, 2 to 8, 1.5 to 5.5 and 3.1 to 4.7) and, therefore, all sub-ranges of all ranges expressly disclosed herein are hereby expressly disclosed. These are only examples of what is specifically intended and all possible combinations of numerical values between the lowest value and the highest value enumerated should be understood to be expressly stated in this application in a similar manner.

[0063] This disclosure may also be said broadly to consist in the parts, elements and features referred to or indicated in the specification of the application, individually or collectively, and any or all combinations of any two or more said parts, elements or features.

[0064] Where specific integers are mentioned herein which have known equivalents in the art to which this disclosure relates, such known equivalents are deemed to be incorporated herein as if individually set forth.

[0065] The disclosure consists in the foregoing and also envisages constructions of which the following gives examples only.BRIEF DESCRIPTION OF THE DRAWINGS

[0066] Specific embodiments and modifications thereof will become apparent to those skilled in the art from the detailed description herein having reference to the figures that follow, of which:

[0067] Figure 1 shows an example magnetic coupling structure, more particularly top and side views of the structure.

[0068] Figure 2 shows an example coil from the magnetic coupling structure of Fig.1.

[0069] Figure 3 shows a profile of the example coil of Fig. 2.

[0070] Figure 4 shows an example magnetic coupling structure.

[0071] Figure 5 shows an example magnetic coupling structure with an overlapping loop coil, more particularly top and side views of the structure.

[0072] Figure 6 shows an example magnetic coupling structure with no loop coil.

[0073] Figure 7 shows an example magnetic coupling structure with coils of varying size.

[0074] Figure 8 shows an example magnetic coupling structure with coils of varying size.

[0075] Figure 9 shows an example magnetic coupling structure with a space between the coils.

[0076] Figure 10 shows an example magnetic coupling structure with two coils arranged about the loop coil.

[0077] Figure 11 shows an example magnetic coupling structure with two coils arranged about the loop coil.

[0078] Figure 12 shows an example magnetic coupling structure with one coil arranged about the loop coil.

[0079] Figure 13 shows an example magnetic coupling structure with two serpentine coils arranged about a circular loop coil.

[0080] Figure 14 shows an example magnetic coupling structure with two serpentine coils arranged about a circular loop coil with return windings.

[0081] Figure 15A shows the wire windings within the structure of Figure 1.

[0082] Figure 15B shows wire windings similar to that of Figure 15A but with no loop coil.

[0083] Figure 16 shows an example magnetic coupling structure with variable dimensions shown.

[0084] Figure 17 shows a side profile of the magnetic coupling structure of Figure 1.

[0085] Figure 18 shows the magnetic coupling structure of Figure 1 associated with a circular pad.

[0086] Figure 19 shows an alternative example arrangement of one coil arranged about the loop coil.

[0087] Figure 20 shows an example of a magnetic coupling structure similar to Figure 10 with no loop coil.

[0088] Figure 21 shows the magnetic coupling structure of Figure 1 in a different representation with different annotations.

[0089] Figure 22 shows the magnetic coupling structure of Figure 10 in a different representation with different annotations.

[0090] Figure 23 shows a magnetic coupling structure with some similarity to that of Figure 19.

[0091] Figure 24 shows the magnetic coupling structure of Figure 13 in a different representation with different annotations.DETAILED DESCRIPTION

[0092] This description relates to magnetic coupling structures. These may be referred to as pads. In wireless power transfer power is transmitted from a transmitter to a receiver. In some cases, this is reversible, or both may be transceivers. Each of the transmitter and the receiver has a magnetic coupling structure to improve or assist the power transfer. The magnetic coupling structures comprise one of more coils of wire. The coils may be placed on a magnetically permeable material to enhance or encourage magnetic flux to flow in the magnetic coupling structure. An example magnetically permeable material is ferrite, but any material which has a high permeability to magnetic flux may be used. A suitable magnetic permeability may have a relative permeability of at least 2, at least 3, at least 5, at least 10, at least 50, or at least 100, for example. Although shown as sheets herein the magnetically permeable material may be formed by one or more sections (i.e., bars or blocks) which may have spacing between them. In some cases, a shield layer, such as aluminium, or other metal, is placed behind the magnetically permeable material, to reduce flux leaving the back of the magnetic coupling structure.

[0093] A coil may refer to a loop of wire, such as Litz wire, which is formed into a loop or spiral. Current passing through the coil creates a magnetic field which is used to transmit power on a transmitter coils. Similarly, a coil placed in a magnetic field will have an induced current on a receiver coil. Where coils are shown by block representations it will be understood this is to simplify the drawing and that the skilled person will be able to construct a suitable winding pattern for the coil based on these drawings.

[0094] Wireless power transfer refers to the ability to use magnetic fields to transfer power over a distance. The coils of the magnetic coupling structure are driven by resonant circuits to increase the distance that power can be transferred efficiently. Wireless power transfer may also be referred to as inductive power transfer (I PT) or resonant power transfer (RPT). Because of the distances between the transmitter (also referred to as a primary) and the receiver (also referred to as a secondary) the structures are loosely coupled. This makes the design more complex than, for example, transformers.

[0095] The present disclosure discusses coils forming loops or paths. These terms should be understood broadly to refer to an item or line which begins and ends (nominally) at the same point, or which forms a closed path. Although shown as circle and / or square paths herein it will be understood that the paths may vary in geometry, forming irregular shapes. The shapesmay be rotationally symmetric in some cases as this can improve power transfer. In some cases, paths may be incomplete, although the shape or nature of the path will be clear from the remaining items.

[0096] The presence of multiple coils on one structure means that the coils typically interact and transfer power between themselves. This reduces the efficiency of and / or maximum power transfer. However, controlling an overlap between coils can balance the transmitted and received magnetic flux between the coils. This can be understood based on Faraday's law of induction and Lenz's law. The change in magnetic flux of time induces a change in magnetic field over the coil area. The reactive mutual inductance can be minimized when the net magnetic flux into and out of one coil due to anther coil is zero. This is achieved by offsetting magnetic flux into the coil and out of the coil (i.e., magnetic flux perpendicular to the coil) from the other coil. Because the coils receive as much flux as they transmit there is no effect due to the presence of the other coil. In this way the effective coupling can be ameliorated, ideally to zero. To determine if two coils are mutual decoupled simulations or experiments may be used. This may be helpful, particularly where magnetically permeable material is present. However, identifying areas in which the magnetic flux can be offset provides an indication of likely decoupled coils for pads. In many cases, particularly where magnetically permeable material is present, it is difficult to fully decouple coils. References to no mutual coupling herein may therefore be understood as substantially no mutual coupling, or negligible mutual coupling. Therefore, mutually decoupled coils may have a low level of coupling remaining, such as less than 5%, less than 2% or less than 1% of the coupling present when not overlapped. In some cases, the mutual coupling may be with respect to a transmitted or received power. For example, the coupling between coils may be less than thirty percent of the coupling between a transmitting and receiving coil. For example, a 10% power transfer coupling between a transmitting and receiving coil would have less than 3 percent coupling between two transmitting coils.

[0097] Figure 1 shows a magnetic coupling structure 100 with four coils 101, 110, 111, 112. These are placed on a magnetically permeable layer 115 (e.g., a layer of magnetically permeable material, such as ferrite), although this is not required. A shielding layer may be present beneath the magnetically permeable layer 115. The magnetically permeable layer 115, and the shielding layer below are square in Figure 1, but this is not required. The magnetically permeable layer 115 and / or the shielding layer may extend past the other perimeter of the coils on the magneticcoupling structure 100. The loop coil 101 forms a loop. It will be referred to as the loop coil 101 herein but may also be referred to as a central coil or a first coil. The loop is shown about a centre of the magnetic coupling structure 100. The loop is shown as a circle. The loop does not need to be a circle. The loop may be square, substantially square or square with rounded corners, for example. The loop substantially or completely surrounds a centre of the magnetic coupling structure.

[0098] The remaining three coils 110, 111, 112 have outer portions 122 outside the radius of the loop coil 101 and inner portions 121 within the radius of the loop coil 101. In some cases, the loop coil 101 extends over some or all of the inner portions 121. The inner 121 and outer portions 122 of the coils 110, 111, 112 are connected by connecting portions 123. The connecting portions 123 may alternatively be referred to as the side potions of the coils, the side portions extending between the inner 121 and outer potions 122, or past the loop coil. The connecting portions 123 are shown as substantially radial from the centre of the magnetic coupling structure 100. However, they may be configured at another angle. For each coil 110, 111, 112 the inner portion 121, outer portion 122 and connecting portions 123 form a loop. These loops are irregularly shaped, so that the overlaps between the coils 101, 110, 111, 112 can be controlled.

[0099] The inner portions 121 may be parallel to the corresponding portion of the loop coil 101. For example, the inner portions 121 may follow the contour of the portion of the loop coil between the inner 121 and outer portion 122 (i.e., between the two connecting portions 123 attached to the inner portion 121). In this way the inner portions are concentric to the loop coil 101. In examples where the loop coil is not present the inner portions 121 may, in combination, form a convex shape, such as a circle or square.

[0100] The four coils 101, 110, 111, 112 of Figure 1 are all mutually decoupled. Each pair of the three coils 110, 111, 112 overlaps with the othertwo of the three coils 110, 111, 112. The overlap is controlled by the positioning of the connecting portions 123. This may be controlled by controlling a spacing between each two neighbouring connecting portions 123 of different coils 110, 111, 112. Therefore, the overlap can be configured to remove any mutual coupling between the three coils 110, 111, 112. Moreover, the loop coil 101 is also mutually decoupled from the other three coils 110, 111, 112. This is because shape and position of the three coils 110, 111, 112 allows the loop of the loop coil 101 to balance flux between each of the threecoils and itself (i.e., each coil balances flux into the loop coil 101 (e.g. within the loop coil 101) and flux out of the loop coil 101 (e.g. outside of the loop coil 101)

[0101] In some cases, each of the coils 110, 111, 112 is concave. In some cases, the inner portion 121 is the concave portion. A concave coil has a kink or bend in it such that it folds back on itself. A concave coil has two points within the coil through which a line may be drawn, the line passing outside of the outer perimeter of the coil. The presence of the concave shape of the inner potion 121 provides a controllable distance between the inner portion 121 and the loop coil 101. In combination with the controllable distances between the loop coil 101 and the outer portion 122 this allows mutual decoupling to be obtained between the coils 110, 111, 112 and the loop coil 101. In some cases the concave shape of the inner portion 121 matches the shape of the loop coil 101 adjacent the inner portion. Each inner portion 121 may form a parallel curve with at least a portion of the loop coil 101. The loop coil 101 may be convex to allow this matching.

[0102] Figure 2 shows a single coil 110 of the three coils 110, 111, 112. The other coils 110, 111, 112 may be substantially identical, although example coils of differing measurements will be illustrated below. In Figure 2 the coil 110 has a wider outer portion 122 relative to the inner portion 121. This is not required but may improve flux transmission or receival in use. The coil 110 spans approximately 145 degrees of a circle so as to completely surround a centre of the magnetic coupling structure 100 when combined with the other two coils 111, 112 and overlap the other two coils. The span is greater than 120 degrees due to the overlap required between coils 110, 111, 112. Each coil in Figure 1 is on top for 120 degrees, but the overlap (depending on the required overlap for mutual decoupling) may range up to 5, 10, 15, 20 or 25 degrees or more additional size. The coil 110 has a perimeter similar to an annular torus, with an opening (i.e., a space without windings) in the middle to form a pole of the coil 110. The coil 110 is shown representatively. In manufacture the coil 110 is formed from a winding of wire (for example Litz wire) with the winding forming a spiral within the area shown.

[0103] The coil 110 of Figure 2 has geometrical parameters that may be varied to enable mutual decoupling. For example, the width of the outer portion 122, inner portion 121 or spacing between the inner 121 and outer portion 122. The width and spacing of the connecting portions 123 may also be varied. The coil 110 may be a flat coil. A flat coil is wound in a single layer, or as close to a single layer as possible for electrical connections to the coil. As shown in Figure 3 the coil 110 may have two levels or be angles so to have a higher portion 130 and alower portion 131. As will be discussed later the higher potion 130 and lower potion 131 may be used to reduce the overall height of the magnetic coupling structure 100.

[0104] Although a particular shape of coil 110 is shown it will be understood this shape or geometry can be varied while maintaining the ability to mutually decouple the coil 110. For example, the corners of the coil 100 may be rounded. Figure 2 shows the outside corners of the inner portion 121 are not square. A chamfer 125 has been used to control the overlap with neighbouring coils. In some cases, the corners may be rounded due to manufacturing processes or tolerances, such as the difficulty in winding the wire in the coil 110. In some cases, the shape of the outside perimeter of the coil 110 may be changed. Typically, the coil will remain substantially an annular sector shape. However, the outer edge or perimeter 127 may appear more planar, or square, extending the coil 110 over more of the pad. In some cases, the shape of the inside perimeter may be changed. The inner perimeter is shown as an annular sector (e.g., a sector of a torus). However, the inner perimeter could be more circular, or substantially circular and / or have rounded or shaped corners and / or sides. The inner perimeter may be a parallel curve to the inner perimeter of a loop coil.

[0105] Figure 2 shows the inner portion 121 and outer portion 122 are substantially concentric. That is to say the shape of the inner portion 121 and outer portion 122 are similar (i.e. similarly shaped), both form an annular sector with the same angle. However, the radius of the outer portion 122 is greater. In some cases, the shape may have further differences, such as chamfers or extensions. The portions 121, 122 may span approximately the same sector angle. The concave nature of the coil 110 means that a portion, inner portion 121 is seen to fold back on itself. In some cases, the coil 110 may not completely fold back, but at least form a straight edge on the inner perimeter of the inner portion 121.

[0106] Returning to Figure 1, it shows that, where the coils 110, 111, 112 extend around the centre of the magnetic coupling structure (i.e., in combination), an inner path 140 and outer path 141 are formed. The inner path 140 is formed by the combination of the inner portions 121 of each of the coils 110, 111, 112. The outer path 141 is formed by the combination of the outer potions 122 of each of the coils 110, 111, 112. Although the paths 140, 141 appear as continuous loops in practice no current flows along the paths 140, 141. In contrast, because the coils 110, 111, 112 are mutually decoupled the currents in each inner portion 122, for example, can flow in different directions, and with different magnitudes. However, it may be helpful to describe the as paths 140, 141 to explain the magnetic coupling structure 100.

[0107] Figure 1 shows the inner path 140 forming a circle within the loop coil 101 with the outer path 141 forming a circle outside the loop coil 101. However, the paths do not have to be circular, they may be loops. The loops may be square, or curved, for example. The paths 140, 141 may be convex so as to match or mirror the shape of the loop coil 101. The paths may be the same shape as the loop coil 101. For example, the inner path 140 of Figure 1 forms a circle, matching the shape of the loop coil 101. The connecting portions 123 of the coils 110, 111, 112 form the connections between the paths 140, 141. The spacing of the connecting portions 140, 141 and the inner and outer paths 140, 141 are adjustable so as to create a coil with substantially no mutual coupling between the coils 101, 110, 111, 112.

[0108] Figure 1 shows a space within the inner path 140. The space in the middle controls the performance of the structure 100 in conjunction with another pad during power transfer. It can be varied based on design requirements. In some cases the inner space is as small as possible. The minimisation of the inner space may be limited by the physical winding limit.

[0109] Figure 4 shows an example magnetic coupling structure 100. Again, a loop coil 101 is positioned as a loop over three coils 110, 111, 112. In this case the three coils 110, 111, 112 have sharp corners on the inner portions 121. The coils 110, 111, 112 are approximately the same shape of those of Figure 1. Their outer perimeter is in the shape of an annular sector, with an annular sector opening or space in the middle of the coils. The space forms a pole of the coil. The inner 121 and outer portions 122 are similar. The inner 121 and outer 122 portions have the same sector angle. The magnetic coupling structure 100 may be defined with respect to a centre 150. The centre 150 does not need to be in the centre of the entire magnetic coupling structure 100. For example, the magnetically permeable layer 115 may not be centred on the centre 150. However, the centre 150 forms the centre of the loop coil 101. As figure 3 shows this is the centre of a circular coil. However, if the loop coil is not circular the centre may be defined for loop coils 101 which are regular polygons by being substantially equidistant from the vertices. In other cases, the centre 150 may be a centroid or centre of gravity of the loop coil 101.

[0110] As shown in Figure 4 the centre 150 is also the centre of the annulus formed by the three coils 110, 111, 112. This is equivalent to the centre 150 being the apex of the sector in which the coils 110, 111, 112 are located. Because the centres 150 of the loop coil 101 and the three coils 110, 11, 112 are the same the magnetic coupling structure 100 has an alignment and, in some cases, a symmetry, which helps to provide no mutual coupling between the coils.

[0111] Figure 5 shows a magnetic coupling structure 100 in which the loop coil 101 overlaps with the inner portions of the three coils 110, 111, 112. The overlap in Figure 5 is complete, meaning that the inner portions are obscured. However, a partial overlap is also possible. The width of the loop coil 101 may be controlled to adjust parameters of the magnetic coupling structure. However, in cases where the loop coil 101 overlaps the inner portions the height of the coils may be thicker, because it is not possible to interleave the loop coil 101. Overlapping the loop coil 101 can affect the pole pitch of the loop coil 101, which in turn affects the coupling between the loop coil 101 and a corresponding primary or secondary pad. The overlapping loop coil 101 may distribute the volt-amp effort to control losses in the magnetic coupling system. In a further example the loop coil 101 may substantially span the space between the inner 121 and outer 122 portions of the coils 110, 111, 112. In a further example the loop coil 101 may be located beneath the coils 110, 111, 112. In some cases, the loop coil extends to an inner perimeter of the outer portions 122. In some cases, the loop coil does not overlap the outer portions 122.

[0112] Figure 6 shows a magnetic coupling structure 100 in which only the three coils 110, 111, 112 are present (l.e., the loop coil 101 has been removed). In some cases, the magnetic coupling structure 100 does not required the loop coil 101. In some cases, the loop coil 101 is optional, or may be added and removed to the magnetic coupling structure 100. This is possible because the coils 101, 110, 111, 112 are substantially mutually decoupled, meaning that the presence of each coil does not affect the remaining coils. However, it may be difficult to ensure the positioning of the loop coil 101 is appropriate when inserting it into the pad. A guide may be used to ensure the loop coil 101 is placed in the required positions(s) for no mutual coupling.

[0113] Figure 7 shows a magnetic coupling structure 100 with a circular loop coil 101 and three coils 110, 111, 112. In this case the three coils 110, 111, 112 are not the same shape. Each of the coils 110, 111, 112 has a different annular sector angle, or spans a different fraction or angle of loop. In this case coil 110 has the largest angle, followed by coil 111 then coil 112. However, provided the overlap between the coils 110, 111, 112 is controlled there may be no mutual coupling between the coils 110, 111, 112 even of different shape and / or size. This asymmetrical arrangement may be useful to provide different charger powers and / or power and communication coils. For example, the largest coil (110 in Figure 6) may be used to supply a high level of power. The smaller coils 111, 112 may be used to provide auxiliary power, or to increase the total amount of power transferred. In one example the structure 100 providesmultiple power levels depending on which, and how many, of the coils 101, 110, 111, 112 are activated. For example, the structure 100 could be a universal charger providing a range of charging rates between say, 5W (a smart watch) and 150W (a laptop).

[0114] Figure 8 shows a further variation in which two of the coils 111, 112 have the same sector angle, with the remaining coil 110 having a larger sector angle. In a further example two of the coils may have the same sector angle, with the remaining coil having a smaller angle. Although the balanced structure where all three coils 110, 111, 112 have the same sector angle may be advantageous, this is not required.

[0115] In a further example, Figure 9 shows only two coils of the three coils 110, 111. This means the inner path 140 and outer path 141 are broken. However, because the coils 110, 111 are operated independently (because they are decoupled) and the paths 140, 141 do not carry a continuous current this would not stop operation of the magnetic coupling structure 100. Also, because the coils 110, 111 are mutually decoupled the magnetic coupling structure 100 would still be able to transfer power. Figure 9 shows the loop coil 101, but again this may be omitted.

[0116] Figure 10 shows an example magnetic coupling structure 100. A loop coil 101 is interleaved with two coils 110, 111. In this example the loop coil 101 is square. The two coils 110, 110 also have straight sides. The inner portion 121 and outer portion 122 form squares. This mirrors the shape of the loop coil 101. Again, the shape of the inner portions 121 is parallel to the shape of the loop coil 101. It is possible to form a similar three coil 101, 110, 111 magnetic coupling structure 100 with a circular shape, if desired. Other shapes are also possible. As with the previous magnetic coupling structures 100 the two coils 110, 111 are concave. The inner portion 121 has a recess 160. The recess 160 is towards the outer portion 122. The concave coils 110, 111 can then overlap with the loop coil 101 and have no mutual coupling. The overlap between the two coils 110, 111 and the size of the recess 160 can be used to reduce the coupling. As with the previous examples the inner portions 121 are concentric with the outer portions - being of the same shape and having a smaller diameter than the outer portions. The magnetic coupling structure 100 does not require the loop coil 101. Because the loop coil is decoupled it can be removed or replaced without effecting coils 110, 111. The centre of the loop coil 101, the inner portions 121 and the outer portions 122 is the same.

[0117] Figure 11 shows another example magnetic coupling structure 100. As with the structure of Figure 9 there is a loop coil 101 and two other coils 110, 111. However, in this case the recess 160 is not in the middle of one side of the coils 110, 111. Instead, the recess 160 is between two adjacent sides of each of the coils 110, 111. The recess 160 extends from a corner of each coil 110, 111. This moves the position of the connection portions 123 from an aligned position, shown horizontally in Figure 10, to offset positions, shown vertically in Figure 11. The inner portion 141 and outer portion 142 still form square loops and the inner portions 141 are still concentric with their outer respective outer portions 142. The position of the connecting portions 123, the overlap between the coils 101, 110, 111 and the size of the recess 160 may be controlled to provide no mutual coupling between the coils. Again, magnetic coupling structure 100 is shown as a square, but a circular structure, or other shape, is also possible.

[0118] The example of magnetic coupling structures 100 may be used without the loop coil 101. For example, Figure 20 shows a magnetic coupling structure 110 with only the two further coils 110, 111. Each of the coils 110, 111 has a recess 160 so that the inner portions 121 are made parallel with the outer portions 122. Other methods to create parallel inner 121 and outer portions 122 may be used. In some cases, a circular shape could be used instead of a square. Similarly, to the three-coil example, shown in Figure 6, the loop coil may be insertable and / or removable, optionally with a guide. The inner portions 121 and outer portions 122 form inner and outer loops. The loops do not overlap. The recess 160 may enable the coil to reduce leakage flux in comparison to, for example, a bipolar coil, or otherwise provide a further degree of freedom in manufacture that may be used to improve the performance of the structure 100 while maintaining the mutual decoupling between the coils.

[0119] In general, for all the magnetic coupling structures 100 shown herein it is possible to remove one or more of the coils 101, 110, 111, 112. This is because the coils are mutually decoupled. Because they are decoupled the coils do not affect one another, so the removal of any one coil will not prevent the remaining coils from operating. This can provide added flexibility to systems, where a selection of one or more of the coils may be operated independently. The selection may be made based on a parameter. The parameter may be measured. An example parameter is output or input power. The number of coils used for a structure 100 may depend on power requirements. For example, a three-coil system may be able to have smaller rated coils, because selections of at least two coils can be used at differenttimes, whereas a two-coil system (such as shown in Figure 20) may require full rating in both coils to be able to provide sufficient power.

[0120] Figure 12 shows an example magnetic coupling structure 100 with a loop coil 101 and a second coil 110. The loop coil 101 and the second coil 110 are mutually decoupled. This is because the flux transmitted and received between the coils 101, 110 is offset. This is achieved by the shape and positioning of the coils 101, 110. The coils 101, 110 share a common centre 150. The loop coil 101 is a loop about the centre 150. The second coil also surrounds the centre 150. The second coil has an outer portion 121 outside of the loop coil 101 and an inner portion122 inside of the loop coil. Connecting portions 123 pass between the inner 121 and outer 122 portions. The connecting portions 123 are spaced apart, which helps control of the coupling. In some cases, because the coils are centred about the same point 150 the inner portion 121 allows the mutual coupling to be minimized.

[0121] Figure 12 shows a circular loop coil 101. Although the design is not limited to circular coils. The second coil 110 is concave, with the inner portion forming a concave portion of the second coil 110. The inner portion 121 and outer portion 122 are similar, both forming almost complete loops between the connecting portions. The second coil 110 is placed above the loop coil 101, but this relationship could be reversed. The inner portion 121 is also similar to the circular shape of the loop coil 101. Matching, or substantially matching, the internal shape of the loop coil 101 helps to balance the magnetic flux transferred between the coils around the whole structure 100. The inner portion 121 and the loop coil 101 are parallel curves.

[0122] The gap 160 between the connecting portions 123 is small, relative to the circumference of the second coil 110. This maximizes the size of the second coil 110 and therefore the balance transfer. The gap 160 may also make the second coil 110 more symmetrical. In some cases, a wider gap 160 may be used. The spacings between the loop coil 101 and the inner perimeter of the outer portion 121 and / or the outer perimeter of the inner portion 122 may also be modified to minimise the mutual coupling between the coils 101, 110. As with the previous examples the width of the coils 101, 110 and the inner and outer portions 121, 122 may also be varied depending on the magnetic coupling structure 100 requirements.

[0123] Figure 19 shows a second example of a loop coil 101 with a single satellite coil 110. Again, the coil 110 has an inner portion 121 and an outer portion 122. Connecting portions123 pass between the inner 121 and outer 122 portions. The loop coil 121 is configured to overlap the inner portion 121 such that it completely overlies (or similarly underlies) the innerportion. The coils 101, 110 are still mutually decoupled. This may be achieved by controlling the size and / or position of the inner portion 121 to balance the flux between the coils. Advantageously overlapping the loop coil 101 may distribute the volt-amp effort to control losses in the magnetic coupling system.

[0124] Figure 13 shows a loop coil 101. The loop coil 101 is again forming a loop about a centre 150 of magnetic coupling structure 100. The loop coil 101 is circular. In this case no magnetically permeable material or shield is shown, but one could be used if desired. However, the two further coils 110, 111 are now serpentine coils. The serpentine coils cross the loop coil 101 multiple times. A series of connecting portions 123 are used to create a plurality of inner portions 121 and outer portions 122 of each coil 110, 111. The locations of the connecting portions 123 of each of the coils 110, 111 are configured to mutually decouple the coils 110, 111. Because of the serpentine shape the loop coil 101 can also be decoupled. Each of the inner portions 121 is parallel to the loop coil 101 between it and the outer portion, or between when it's connecting portions 123 cross the loop coil 101. It can be seen that the inner path 140 is circular like the loop coil 101.

[0125] The inner path 140 may, more generally, be the same shape as the loop coil. The inner path 140 is formed by connecting all of the inner portions 121. Similarly, the outer path 141 encircles the loop coil 101. It is also shown as the same shape as the loop coil 101. However, this may be varied, if required. The loop coil and the serpentine coils 110, 111 are each centred about the same pad centre 150. This provides a symmetry ensuring there is no mutual decoupling about the coil.

[0126] In some cases, the shape of the loop coil 101 is not circular. For example, the loop coil 101 could be square or elliptical or other loop shape. The serpentine coils 110, 111 would also be modified to follow the shape of the loop coil 101. For example, they may form a square or elliptical path. The inner portions 121 would form an inner path 140 which is also, for example, square or elliptical, as each follows the contour or shape of the loop coil 101. The inner path 140 may be continuous, instead of the broken inner path 140 shown in Figure 13. The inner path 140 of Figure 13 in which the inner portions 121 abut and / or overlap one another. The inner path 140 and / or the combination of inner portions 121 may be discontinuous. Similarly, the outer path 141 and / or portions 122 may be discontinuous, as shown. The loop coil 101 and the serpentine coils 110, 111 are centred on the same point, centre 150. The symmetry helps to minimise mutual coupling.

[0127] Figure 14 shows a magnetic coupling structure 100 similar to Figure 13. Again, the loop coil 101 is circular and the serpentine coils 110, 111 cross the loop coil 101 several times as the loop about the loop coil 101. However, the serpentine coils 110, 111 now have return coils, 113, 114. The return coils 113, 114 have inner portions where the coils 110, 111 have outer portions. The return coils 113, 114 may advantageously make connection of the coils 110, 111, 113, 114 more straightforward.

[0128] Figure 15A shows an example winding diagram for the coils 110, 111, 112 of a magnetic coupling structure 100 as in Figure 1. In this case each of the coils 110, 111, 112 are identical. They have been offset from one another about the centre 150 of the pad so as to encircle the loop coil 101. Each coil 110, 111, 112 is formed by loops of wire 190. The shape of the coil 110, 111, 112 is controlled by the position of the wire 190 and / or the spacing of adjacent wire 190 layers. In order to provide connections to and from the coils 110, 111, 112 the wire 190 may have to pass under itself, such as point 119. As shown the inner portions 121 are made thinner than the outer portions 122 because the spacing between the layers of wire 190 is reduced. Coil 101 is also constructed of a wound wire but is represented by an annulus in Figure 15A.

[0129] Figure 15B shows another example winding diagram similar to Figure 15A but without the loop coil 101.

[0130] Figure 16 is a four-coil system with loop coil 101 and three coils 110, 111 and 112. In some cases, the loop coil 101 may be referred to as a sun coil or central coil with coils 110, 111 and 112 being planet or satellite coils. The satellite coils 110, 111, 112 extend about an orbit of the sun coil 101. This magnetic coupling structure 100 may be referred to as a planetary pad 100. Where all three coils 110, 111, 112 are present the entire orbit around the sun coil 101 is full. However, only two coils 110, 111 may be used, in which case a gap may be left. As shown in Figure 16 the connecting portions 123 are spaced apart from one another to allow for substantially no mutual coupling.

[0131] Figure 16 shows various measurements which may be used to control the size, power transfer capability or coupling of the coils 101, 110, 111, 112. The loop coil 101 in an annulus with radius Rq (e.g., to the midpoint of the coil) and width Cq. Each of the coils 110, 111, 112 has an inner radius of R2 (e.g., to the midpoint of the inner portion). An outer radius (e.g., to the midpoint of the outer portion) is not shown but could be configured. The thickness of the inner portion 122(Ci), outer portion 122 (Co) and connecting portion 123 (Cc) may also be configured. The sector angle 0 of the coils 110, 111, 112 specifies the width of the coils relativeto the loop coil 101. In this case the coils 110, 111, 112 are each slightly over 120 degrees (due to the connecting portions 123 overlapping). For example, the coils may be 130 degrees, 140 degrees, or 150 degrees. The coils may be between 100 and 150 degrees, more particularly between 100 and 130 degrees. The width of the coils will depend on the overlap required for decoupling. This may change based, for example, on the presence of ferrite. The magnetically permeable layer 115 may extend to, extend further than, or extend less than the coils 110, 111, 112. It may have dimensions Fx, and Fy.

[0132] Applications for the magnetic coupling structures 100 include low power biomedical scenarios, cellphone charging, factory automation and Electric Vehicle (EV) charging. The ability to operate each coil 101, 110, 111, 112 independently (for example, with different currents and / or at different frequencies) means that the magnetic coupling structure 100 has great flexibility. For example, different coils 101, 110, 111, 112 may be operated depending on a position of magnetic coupling structure to which the magnetic coupling structure 100 is coupled. For example, if a receiver pad (pick-up pad) is on an EV one or more coils may be operated based on the position of the receiver pad relative to the magnetic coupling structure 100. The same approach may be used where the magnetic coupling structure 100 is a receiver pad coupled to a transmitter pad (primary pad). The independent operation of the coils may allow the system to direct or concentrate magnetic flux in a desired region of the magnetic coupling structure 100. This may improve power transfer.

[0133] In another example the coils 101, 110, 111, 112 are used for different purposes. For example, at least one of the coils may be used for communication. The communication may be about the power transfer of the other coils. The communication coil may be smaller than the power transfer coils. In some cases, the loop coil 101 is used as the communication coil. In some cases, the coils 101, 110, 111, 112 may be selectively operated depending on power levels required. For high power transfer all coils may be operated. Where lower power transfer is required one, or a selection of the coils may be operated. In some cases, the coils may be configured to provide multiple phases. For example, the coils 110, 111, 112 may supply three phases. However, because the coils are mutually decoupled the coils can be individually controlled so do not require a specific phase relationship. In some cases, multiple magnetic coupling structures 100 may be used. The structures 100 may be placed next to each other or arrayed on a surface to form a large structure. A separation between the structures 100 would be used to reduce coupling between the structures 100.

[0134] The coils 101, 110, 111, 112, may use different compensation topologies (i.e., be driven by different resonant circuit topologies). For example, the loop coil 101 could be driven by a series tuned topology, with the remaining coils driven by parallel tuned topologies (such as LCL). The reverse could be used, or the series / para I lei topologies could be mixed. The poles of the coils 110, 111, 112 could be positioned to reduce the amount of magnetic flux in the magnetically permeable layer 115 near the centre of the pad. This could be achieved by changing the geometry of the coils 110, 111, 112. Operating the coils independently is possible, due to the mutual decoupling. This may allow each of the coils to have different currents magnitudes and phases to control the structures 100 volt-amps to suit any device (e.g., vehicle) magnetic structure or power class requirement.

[0135] US10958111 B2 shows a three-winding magnetic coupling structure. While additional coils to the magnetic coupling structure can provide increased degrees of freedom for controlling the structure the size of the magnetic coupling structure increases, this makes the magnetic coupling structures increasingly bulky and more difficult to use in applications. For example, the magnetic coupling structures are more difficult to fit in vehicles to provide charging applications.

[0136] Returning to Figure 1 the coils 110, 111, 112 (which may be referred to as satellite coils, or surrounding coils) and the loop coil 101 are overlapped. Advantageously this overlap is used to reduce the height of the coils. The height may refer to the number of layers taken up by the coils (i.e., the maximum height of all coils on a structure 100). A simple arrangement would simply layer the flat coils on top of each other. However, as in US10958111 B2 this can result in a coil which has a maximum height equal to the sum of the individual coils (because at one point all the coils overlap).

[0137] In Figure 1 the coils 101, 110, 111, 112 overlap to control the mutual coupling between them. An overlap is required to mutually decouple the coils. All of the coils must overlap so as each of the coils are not coupled to any other coil. By selecting the overlap locations to be different for each pair of coils 110, 111, 112 the height of the magnetic coupling structure can also be reduced, because there is no point in which all coils 110, 111, 112 must be stacked on top of one another. In some cases, the loop coil 101 adds no additional height to the structure 100, because it can overlap in the spaces already created by the higher and lower portions of the coils 110, 111, 112. This reduction in height allows improved degrees of freedom of operation provided by multiple coils, while also providing a low-profile magnetic couplingstructure. The overlapping also means that the relative distance between the each of the coils (and a ferrite, if present, is reduced) reducing the inductances of the coils. A further advantage of a three-coil system (with or without the loop coil 101) is rotational symmetry.

[0138] The coils are formed by flat coils (i.e., coils of substantially one layer winding). The coils are arranged in layers on one side of the structure 100. This is shown as on one side of a magnetically permeable layer 115 in Figure 1, but this is not required. As shown in Figure 3, by creating a height difference between the ends of the flat coil the coil 110 can be given an upper portion 130 and a lower portion 131. Although the higher and lower portions 130, 131 are shown at the ends of the coil 110, this is not required. A constant slope between the higher and lower portions 130, 131 is shown, but not required. The higher portion 131, or the lower portion, may be in, or towards a centre of the coil. By overlapping the three coils 110, 111, 112 so as the upper portion 130 of one coil sits on the lower portion 131 of the next coil the group of three coils 110, 111, 112 can be formed on one later. Figure 1 shows this arrangement.

[0139] In Figure 1 the loop coil 101 is then placed under upper portions or over lower portions of the coils 110, 111, 112. This may require the slope between the higher and lower portion 130, 131 to be steeper, so as to create a space for the loop coil 101. In this way the four-coil structure 100 uses only two later, instead of previously four layers, each coil having portions on each of the two layers. The loop coil 101 is able to interweave with the other coils 110, 111, 112 because the connecting portions 123 are offset from one another. If the connecting portions 123 overlapped the loop coil 101 would have to form an additional layer.

[0140] In some cases, not all coils are interleaved. For example, Figure 4 shows a magnetic coupling structure 100 in which only coil 111 is interleaved on two layers. Coils 110, 112 are completely on the bottom and top layer respectively. This still allows the coils to be formed in two layers. A fist coil could still be included in those two layers by passing over coil 111 and under coil 112 in each position. Figure 5 shows that the loop coil 101 may not be interleaved. Because the loop coil 101 extends over the inner portions 121 it must sit above (or below) all of the other coils 110, 111, 112.

[0141] Therefore at least some of the coils 101, 110, 111, 112 in the magnetic coupling structure 100 have upper portions and lower portions. The coils configured so as to reduce the maximum height of the structure 100. This is not required to achieve mutual decoupling. In some cases, it improves the balance between the coils 101, 110, 111, 112 because the distance between the coils and the permeable magnetic material 115 is reduced and / or balanced foreach coil. The reduction in height is possible because each coil overlaps each of the other coils at overlap locations on the magnetic coupling structure, but these overlap locations are different for each pair. Alternatively, there is no position in which all the coils overlap. It is important to consider the actual winding of the coils. In some cases, structures are shown with representative windings which do not show the width or full overlap of each of the coils. In some cases when the width of the coils is then considered there will be overlap of multiple coils on the structure. Therefore, the inner and outer edges of the coils should be considered. Figures 15A and 15B show a winding diagram of an example structure 1010 and the actual overlap of the wires can be seen. In this application the borders of each coil 101, 110, 111, 112 are shown to make the overlap clear, instead of representative lines.

[0142] To create the reduced height system at least one of the coils 101, 110, 111, 112 needs to sit above and below one of the other coils 101, 110, 111, 112. There may be advantages for arrangements where each coil does so, at least for symmetry. However, the coils may be arranged with one or more being a single layer (i.e. having no higher and lower portions). This may be advantageous where that coil is expected to deliver most or all of the power. For example, Figure 7 shows the largest coil 110 arranged in a layer next to the permeable material layer 115. Coil 112 is arranged in a second layer above coil 110. The remaining coil 111 has higher and lower portions to span over two layers and are positioned so as the coils 110, 111, 112 form two layers on the structure 100. As shown one or more of the coils 110, 111, 112 may span over two layers.

[0143] Advantageously by selecting the overlap or underlap of the coils, the height of the magnetic coupling structure is reduced. Thus, the magnetic coupling structure can provide the advantages of a multiple coil structure with a reduced height. The structure 100 can be formed where the height of the coils on the structure (or the number of layers in which the coils are arranged) is less than the sum of the heights of the coils. For example, the three coils 110, 111, 112 may be arranged such that one of the three coils is configured to underlay a second coil at a first position and overlay a third coil at a second position such that the overall height of the first, second and third coils in the magnetic coils is less than the sum of the heights of the first second and third coils. This arrangement means that, for a three coil pad a maximum of two coils overlap at any position. This can be maintained even where the loop coil 101 is introduced.

[0144] Figures 10 and 11 show how the overlap of the coils is also controllable to reduce the structure height in a square structure 100 with three coils 110, 111, 101. The concave nature of the coils 110, 111, 112 may help to control the position of the overlaps but is not required for this height reduction. Figure 13 shows this height reduction is also possible with the serpentine coils 110, 111. Although the coils overlap the loop coil 101 more often, they overlap the loop coil 101 in different locations and in the inner path 140 and outer path 141 only the serpentine coils 110, 111 overlap.

[0145] Figure 17 shows a side profile of the magnetic coupling structure 100 of Figure 1. This includes the coils 101, 110, 111, 112 as well as the magnetically permeable layer 115 and the shield layer 116 beneath the magnetically permeable layer 115. Coil 112 is visible transitioning between higher and lower portions. Coil 110 also makes this transition but appears to be two layers high due to the angel. Loop coil 101 is overlapping and underlapping the other coils, so as to fit between them. These two-layer structure enables a low-profile structure 100, which may be easier to add to devices, such as electric vehicles. The coils 101, 110, 111, 112 also require electrical contacts to provide power to, or receive power from the coils. As shown in Figures 15A and 15B these electrical connections may require the wire 190 to pass between the inside and outside of the coils at some points 119. Advantageously the interleaved structure can provide gaps in which these points 119 can be located so as not to have to add to the height or extend from the structure. For example, the wire 190 can pass under a higher portion 130 of the coil, or over a lower portion 130 of the coil. These points 190 may occur where there is no overlapping between the coil formed by the wire 190 and another coil.

[0146] Figure 18 shows a magnetic coupling structure 100 similar to that shown in Figure 1. The loop coil 101 is shown as sitting above the other coils 110, 111, 112(the structure 100 is shown upside down). The structure 100 is associated or coupled with a circular magnetic coupling structure 200. The magnetically permeable layer 115 and shield have been removed from the structure to allow visibility. The power transfer could be from or to either or both structures 100, 200, depending on the requirements of the application. In other cases, the magnetic coupling structure 100 may be coupled to another magnetic coupling structure 100 of the same or related structure, or any other suitable magnetic coupling structure.

[0147] The arrangement of Figure 18 allows a comparison between two circular pads and the proposed magnetic coupling structures 100 by simulation. The coils may be approximated with a lumped structure comparison. Copper volumes for the structures 100, 200 can beapproximated as 2747503 mm3for the circular pad, and 2139973 mm3for the structure 100. The amount of copper may depend on the design and / or size of the structures. The differences in effective coupling between the coils of the circular pad (CP) and the coils of the magnetic coupling structure (MCS) 100 when associated with a circular pad. As can be seen in Table I below, the coupling coefficient (k) is less variable with respect to misalignment of the coil. keff is a geometric magnitude (square root of the sum of the squares of individual coil couplings) of the individual coupling factors in multicoil structures. It is representative of the required effort to deliver power.Table I

[0148] The magnetic coupling structure 100 has multiple coils which can be independently turned on or off based on the position of the coupled pad. This, combined in some cases with the reduction in variable coupling coefficient can greatly simplify the design of the inverter which is required to drive the volt-amps into the coils to deliver power. In some cases, this allows the use of lower current components. In some case the coupling coefficient changes are further reduced by selectively operating coils. By turning off the least aligned coil the copper losses can be reduced.

[0149] The magnetic coupling structure 100 may be interoperable with different magnetic topologies (circular pads, bipolar pads and DD pads), as well as with different power class magnetics (e.g., WPT3 to WPT6 pads). In some cases, the same system design is used for each arrangement, making interoperability easier.

[0150] At least some of the arrangements described hereinabove are further described hereinafter from another perspective.

[0151] With reference to Figure 21 showing a structure 500 identical to that of Figure 1 in a different representation, the present disclosure provides as one example the magneticcoupling structure 500 comprising: first, second and third coils 510, 520, 530 arranged clear of an axis marked as 'A' in respective radial directions. The coils 510, 520, 530 may also be understood to be arranged radially away from the axis in the respective directions, and arranged to surround and define a clearance area marked as 'C' and centred at the central axis.

[0152] In this example, the coils 510, 520, 530 are offset by 120 degrees about the axis and arranged in the given order along an anticlockwise direction about the axis, with each coil 510, 520, 530 having radially spaced inner and outer segments 512, 514, 522, 524, 532, 534. The inner and outer segments 512, 514 of the first coil 510 overlap a next coil, being the second coil 520, at a first side to substantially decouple therefrom, and overlap a previous coil, being the third coil 530, at a second side opposite to the first side to substantially decouple therefrom. The inner and outer segments 522, 524 of the second coil 520 overlap a next coil, being the third coil 530, at a first side to substantially decouple therefrom, and overlap a previous coil, being the first coil 510, at a second side opposite to the first side to substantially decouple therefrom. The inner and outer segments 532, 534 of the third coil 530 overlap a next coil, being the first coil 510, at a first side to substantially decouple therefrom, and overlap a previous coil, being the second coil 520, at a second side opposite to the first side to substantially decouple therefrom. In some arrangements, the first and second sides may not be opposite.

[0153] Each coil 510, 520, 530 overlaps the next and previous coils 510, 520, 530 on different planes. More specifically, each coil 510, 520, 530 is arranged on a first plane and extends, at the first side, away from the first plane to a second plane to overlap the next coil 510, 520, 530. That is, the first coil 510 extends from the first plane to the second plane at the respective first side to overlap the second coil 520, the second coil 520 extends from the first plane to the second plane at the respective first side to overlap the third coil 530, and the third coil 530 extends from the first plane to the second plane at the respective first side to overlap the first coil 510.

[0154] The structure 500 further has an additional coil (or a loop coil) 505 surrounding the central axis (or the clearance area) and overlapping each coil 510, 520, 530 to decouple therefrom. The additional coil 505 of this example extends on the first plane in one part and on the second plane in another part, and is coplanar in part with the coils 510, 520, 530. In this example, the additional coil 505 is bounded by the outer segments 514, 524, 534 and the inner segments 512, 522, 532 of the coils 510, 520, 530. In some examples, the additional coilbounded by the outer segments may instead overlap the inner segments. The first coil 510 further has two intermediate segments 516, 518 interconnecting the inner and outer segments 512, 514 of the first coil 510 and overlapped by the additional coil 505. The second coil 520 further has two intermediate segments 526, 528 interconnecting the inner and outer segments 522, 524 of the second coil 520 and overlapped by the additional coil 505. The third coil 530 further has two intermediate segments 536, 538 interconnecting the inner and outer segments 532, 534 of the third coil 530 and overlapped by the additional coil 505. The additional coil 505 extends through gaps between the intermediate segments of neighbouring coils, more particularly through a first gap formed between the intermediate segments 516, 528, a second gap formed between the intermediate segments 526, 538, and a third gap formed between the intermediate segments 536, 518. With such a configuration, the additional coil 505 can be regarded as "weaving" through the gaps. It should be noted that, in some arrangements, the additional coil can extend in its entirety on a single plane whilst being decoupled from the coils.

[0155] In this example, the inner segments 512, 522, 532 and the outer segments 514, 524, 534 are arranged concentric with respect to the central axis. That is to say, each inner segment 512, 522, 532 forms a curvature concentric to that formed by the corresponding outer segments 514, 524, 534. The outer segments 514, 524, 534 are greater than the inner segments 512, 522, 532 in width in this example, and may be equal to the inner segments 512, 522, 532 in width in other examples. In some examples, the inner segments may form a curvature different from that formed by the outer segments.

[0156] The configuration of the structure 500 can advantageously accommodate the coils 505, 510, 520, 530 on only two or three planes, achieving a low profile suitable for space limited applications.

[0157] With reference to Figure 22 showing a structure 600 identical to that of Figure 10 in a different representation, the present disclosure provides as one example the magnetic coupling structure 600 comprising first and second coils 610, 620 arranged clear of an axis marked as 'B' in respective radial directions. The first and second coils 610, 620 may also be understood to be arranged radially away from the axis in the respective directions, and arranged to surround and define a clearance area marked as 'D' and centred at the central axis.

[0158] In this arrangement, each coil 610, 620 has identical next and previous coils 610, 620. Specifically, the coils 610, 620 are offset by 180 degrees about the axis, with each coil 610, 620having radially spaced inner and outer segments 612, 614, 622, 624. The inner and outer segments 612, 614 of the first coil 610 overlap the second coil 620 at opposite first and second sides to substantially decouple therefrom. The inner and outer segments 622, 624 of the second coil 620 overlap the first coil 610 at opposite first and second sides to substantially decouple therefrom. In some arrangements, the first and second sides may not be opposite.

[0159] In contrast with the arrangement of Figure 21, each coil 610, 620 as shown in Figure 22 overlaps the other coil, on a same plane. That is, the first coil 610 overlaps the second coil 620 at the corresponding first and second sides on a first plane, while the second coil 620 overlaps the first coil 610 at the corresponding first and second sides on a second plane offset from the first plane. That is, with the arrangement of Figure 22, the first coil 610 overlaps the second coil 620 at the first side on the first plane, and overlaps the second coil 620 at the second side on the first plane; and the second coil 620 overlaps the first coil 610 at the first side on the second plane, and overlaps the first coil 610 at the second side on the second plane.

[0160] The structure 600 further has an additional coil (or a loop coil) 605 surrounding the central axis (or the clearance area) and overlapping each coil 610, 620 to decouple therefrom. The additional coil 605 of this example is extend on the first plane in one part and on the second plane in another part, and is coplanar in part with the coils 610, 620. In this example, the additional coil 605 is bounded by the outer segments 614, 624 and the inner segments 612, 622 of the coils 610, 620. In some examples, the additional coil bounded by the outer segments may instead overlap the inner segments. The first coil 510 further has two intermediate segments 616, 618 interconnecting the inner and outer segments 612, 614 of the first coil 610 and overlapped by the additional coil 605. The second coil 620 further has two intermediate segments 626, 628 interconnecting the inner and outer segments 622, 624 of the second coil 620 and overlapped by the additional coil 605. The additional coil 605 extends through gaps between the intermediate segments of neighbouring coils, more particularly through a first gap formed between the intermediate segments 616, 628, and a second gap formed between the intermediate segments 618, 626. With such a configuration, the additional coil 605 can be regarded as "weaving" through the gaps. It should be noted that, in some arrangements, the additional coil can extend in its entirety on a single plane whilst being decoupled from the coils.

[0161] In this example, the inner segments 612, 622 and the outer segments 614, 624 are arranged concentric with respect to the central axis. That is to say, each inner segment 612,622 forms a curvature concentric to that formed by the corresponding outer segments 614, 624. The outer segments 614, 624 are greater than the inner segments 612, 622 in width in this example, and may be equal to the inner segments 612, 622 in width in other examples. In some examples, the inner segments may form a curvature different from that formed by the outer segments.

[0162] With reference to Figure 23 showing a structure 700 with some similarity to that of Figure 19, the present disclosure provides as one example the magnetic coupling structure 700 comprising a coil 710 having radially spaced inner and outer segments 712, 714 partially surrounding a central axis marked as 'E' (or a clearance area marked as 'G' and centred at the axis), and two intermediate segments 716, 718 interconnecting the inner and outer segments 712, 714; and an additional coil 705 surrounding the axis, bounded by the outer segment 714 and overlapping the intermediate segments 716, 718 to decouple from the coil 710. The additional coil 705 further overlaps the inner segment 712 in this example, and may instead be further bounded by the inner segment 712 in other examples (see Figure 12).

[0163] With reference to Figure 24 showing a structure 800 identical to that of Figure 13, the present disclosure provides as one example the magnetic coupling structure 800 comprising a first coil 810 having radially spaced inner and outer segments 812, 814 staggered about a central axis marked as 'F' (or a clearance area marked as 'H' centred as the axis); and a second coil 820 having radially spaced inner and outer segments 822, 824 staggered about the axis and overlapping those 812, 814 of the first coil 810 to decouple from the first coil 810. With such a configuration, the first and second coils 810, 820 surround the axis.

[0164] The first coil 810 further has intermediate segments 816 interconnecting the inner and outer segments 812, 814 of the first coil 810. The second coil 820 further has intermediate segments 826 interconnecting the inner and outer segments 822, 824 of the second coil 820.

[0165] The structure 800 further has an additional coil 805 bounded by the outer segments 814, 824 and overlapping the intermediate segments 816, 826 to decouple from the first and second coils 810, 820. The additional coil 805 is further bounded by the inner segments 812, 822 in this example, and may instead overlap the inner segments 812, 822 in other examples.

[0166] The magnetic coupling structure is advantageous, as can be understood with reference to Table II below, which shows results of comparison of the structure of Figure 15A with a conventional circular-to-circular coil system. The table is shown to include a first column of "CP-CP", a second column of "CP-Lumped Nominal TFQP Sim" and a third column of "CP-Detailed TFQP". The first column "CP-CP" corresponds to a conventional circular-to-circular coil system, whereas the third column of "CP-Detailed TFQP" corresponds to the structure of Figure 15A. The columns include sub-columns "A" representative of an aligned position with a ground clearance of 160 mm, and sub-columns 'MA' representative of any misaligned position with a ground clearance of 210 mm. Further, where the coils are symmetric with respect to the axis, the structure is agnostic to position and rotation. Such rotational symmetry facilitates design and optimisation for any given dimension. It is noteworthy that keff remains constant despite rotation.Table II

[0167] It can be understood from Table II that, for a given pad area, the structure of Figure 15A can achieve a higher minimum effective coupling factor and a lower Ak. The structure of Figure 15A accordingly requires a lower power regulation effort from associated electronics.

[0168] It can also be understood from Table III below that the structure can maintain efficiency and power across a wide range of misalignment positions, without requiring complex control techniques, large input voltage ranges (Vin), or additional electronic converters. In Table III, "GA" and "VA" stand for "ground assembly" and "vehicle assembly", respectively.Table III

[0169] Although certain embodiments and examples are disclosed herein, inventive subject matter extends beyond the specifically disclosed embodiments to other alternative embodiments and / or uses, and to modifications and equivalents thereof. Thus, the scope of the claims or embodiments appended hereto is not limited by any of the particular embodiments described herein. For example, in any method or process disclosed herein, the acts or operations of the method or process may be performed in any suitable sequence and are not necessarily limited to any particular disclosed sequence. Various operations may be described as multiple discrete operations in turn, in a manner that may be helpful in understanding certain embodiments; however, the order of description should not be construed to imply that these operations are order dependent. Additionally, some structures described herein may be embodied as integrated components or as separate components. For purposes of comparing various embodiments, certain aspects and advantages of these embodiments are described. Not necessarily all such aspects or advantages are achieved by any particular embodiment. Thus, for example, various embodiments may be carried out in a manner that achieves or optimizes one advantage or group of advantages as taught herein without necessarily achieving other aspects or advantages as may also be taught or suggested herein.

[0170] It should be emphasized that many variations and modifications may be made to the embodiments described herein, the elements of which are to be understood as being among other acceptable examples. All such modifications and variations are intended to be included herein within the scope of this disclosure and protected by the following claims. Further, nothing in the foregoing disclosure is intended to imply that any particular component, characteristic or process step is necessary or essential.

Claims

CLAIMS1. A magnetic coupling structure comprising: a plurality of coils arranged clear of an axis in respective radial directions, with each coil having radially spaced inner and outer segments that overlap a next coil at a first side to substantially decouple therefrom.

2. The magnetic coupling structure of claim 1, wherein the inner and outer segments of each coil overlap a previous coil at a second side to substantially decouple therefrom.

3. The magnetic coupling structure of claim 1, wherein the next coil is the previous coil .

4. The magnetic coupling structure of claim 3, wherein each coil overlaps the next and previous coils, on a same plane.

5. The magnetic coupling structure of any one of claims 1 to 3, wherein each coil overlaps the next and previous coils on different planes.

6. The magnetic coupling structure of any one of the preceding claims, further comprising: an additional coil surrounding the axis and overlapping each coil to decouple therefrom.

7. The magnetic coupling structure of claim 6, wherein the additional coil is coplanar in part with the coils.

8. The magnetic coupling structure of claim 6 or 7, wherein the additional coil is bounded by the outer segments of the coils.

9. The magnetic coupling structure of claim 8, wherein the additional coil overlaps the inner segments of the coils.

10. The magnetic coupling structure of any one of claims 6 to 9, wherein each coil further has intermediate segments interconnecting the inner and outer segments of the respective coil and overlapped by the additional coil.

11. The magnetic coupling structure of claim 10, wherein the additional coil extends through gaps between the intermediate segments of neighbouring coils.

12. The magnetic coupling structure of any one of the preceding claims, wherein the inner and outer segments of each coil are arranged concentric with respect to the axis.

13. The magnetic coupling structure of any one of the preceding claims, wherein the outer segments are not smaller than the inner segments in width.

14. A magnetic coupling structure comprising: a coil having radially spaced inner and outer segments partially surrounding an axis, and two intermediate segments interconnecting the inner and outer segments; and an additional coil surrounding the axis, bounded by the outer segment and overlapping the intermediate segments to decouple from the coil.

15. The magnetic coupling structure of claim 14, wherein the additional coil further overlaps the inner segment of the coil.

16. A magnetic coupling structure comprising: a first coil having radially spaced inner and outer segments staggered about an axis; and a second coil having radially spaced inner and outer segments staggered about the axis and overlapping those of the first coil to decouple from the first coil.

17. The magnetic coupling structure of claim 16, wherein the first and second coils surround the axis.

18. The magnetic coupling structure of claim 16 or 17, wherein each coil further has intermediate segments interconnecting the inner and outer segments of the respective coil, the structure further comprising: an additional coil bounded by the outer segments and overlapping the intermediate segments to decouple from the first and second coils.

19. The magnetic coupling structure of any one of claims 16 to 18, wherein the additional coil further overlaps the inner segments.

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