Planar litz coil for wireless power transfer

Abstract

Structures, apparatuses, and methods for wireless power transfer systems are described. The structure may include a plurality of strands arranged in a first coil layer and a second coil layer. The plurality of strands may be formed on parallel paths around a center of the structure. The plurality of strands may extend on the first coil layer away from the center. The plurality of strands may extend on the second coil layer toward the center. For each fixed interval along the length of the structure, a first strand of the plurality of strands may be rewound from the first coil layer to the second coil layer, and a second strand of the plurality of strands may be rewound from the second coil layer to the first coil layer.

Description

Background Art

[0001] The present disclosure generally relates to devices and apparatus including planar Litz coil configurations.

[0002] A wireless power system may include a transmitter with a transmitting coil and a receiver with a receiving coil. The transmitting coil and the receiving coil may be placed close together to form a transformer that can facilitate the inductive transfer of alternating current (AC) power. The transfer of AC power from the transmitter to the receiver can facilitate charging the battery of the device that includes the receiver. Summary of the Invention

[0003] In one embodiment, a structure is generally described. The structure may include a plurality of strands arranged into a first coil layer and a second coil layer. The plurality of strands are formed in parallel paths around the center of the structure. The plurality of strands extend away from the center on the first coil layer. The plurality of strands extend toward the center on the second coil layer. At each fixed interval along the length of the structure, a first strand of the plurality of strands winds back from the first coil layer to the second coil layer, and a second strand of the plurality of strands winds back from the second coil layer to the first coil layer.

[0004] In one embodiment, a device is generally described. The device may include a power rectifier for rectifying alternating current (AC) power into direct current (DC) power. The device may further include a controller connected to the power rectifier. The controller may be configured to control the power rectifier. The device may further include a structure for receiving the AC power. The structure may include a plurality of strands arranged into a first coil layer and a second coil layer. The plurality of strands are formed on parallel paths around the center of the structure. The plurality of strands extend away from the center on the first coil layer. The plurality of strands extend toward the center on the second coil layer. For each fixed interval along the length of the structure, a first strand of the plurality of strands is wound back from the first coil layer to the second coil layer, and a second strand of the plurality of strands is wound back from the second coil layer to the first coil layer.

[0005] In one embodiment, a method for constructing a coil for a device is generally described. The method may include bonding a plurality of strands to a substrate to form a first coil layer and to a second coil layer. The plurality of strands extend away from a center on the first coil layer and toward the center on the second coil layer. At each fixed point on the substrate, the method includes wrapping a first strand of the plurality of strands from the first coil layer back to the second coil layer, and wrapping a second strand of the plurality of strands from the second coil layer back to the first coil layer.

[0006] Further features, structure, and operation of various embodiments are described in detail below with reference to the accompanying drawings. In the drawings, like reference numerals indicate identical or functionally similar elements. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 is a block diagram of an example system for wireless power transfer according to an embodiment.

[0008] Figure 2A is a schematic diagram illustrating components of a receiver that can implement a planar Litz coil for wireless power transfer in one embodiment.

[0009] Figure 2B is another schematic diagram illustrating components of a receiver that can implement a planar Litz coil for wireless power transfer in one embodiment.

[0010] Figure 2C is another schematic diagram illustrating components of a receiver that can implement a planar Litz coil for wireless power transfer in one embodiment.

[0011] Figure 3A is a schematic diagram illustrating a perspective view of an example receiver coil that may implement a planar Litz coil for wireless power transfer in one embodiment.

[0012] Figure 3B An embodiment is shown Figure 3A Schematic diagram of a top view of an example receiver coil.

[0013] Figure 4A is a schematic diagram illustrating a perspective view of an example receiver coil that may implement a planar Litz coil for wireless power transfer in one embodiment.

[0014] Figure 4B An embodiment is shown Figure 3A Schematic diagram of a top view of an exemplary receiver coil.

[0015] Figure 5 is a schematic diagram illustrating a series of steps for rewinding a strand from one layer to another in one embodiment.

[0016] Figure 6 is a flow chart illustrating a process for constructing a planar Litz coil for wireless power transfer in one embodiment. DETAILED DESCRIPTION

[0017] In order to facilitate understanding of the different embodiments of the present application, in the following description, many specific details are set forth, such as specific structures, components, materials, dimensions, processing steps and technologies. However, it will be understood by those skilled in the art that the various embodiments of the present application can be implemented without these specific details. In some cases, in order to avoid obscuring the present application, well-known structures or processing steps are not described in detail.

[0018] Figure 1is a block diagram of an example system 100 for wireless power transmission according to an embodiment. System 100 may include a transmitter 110 and a receiver 120 configured to wirelessly transmit power and data between the transmitter 110 and the receiver 120 via inductive coupling. Although described herein as a transmitter 110 and a receiver 120, each of the transmitter 110 and the receiver 120 may be configured to both transmit and receive power or data between the transmitter 110 and the receiver 120 via inductive coupling.

[0019] The transmitter 110 is configured to receive power from one or more power sources and wirelessly transmit AC power 130 to the receiver 120. For example, the transmitter 110 can be configured to connect to a power source 116, such as an adapter or a DC power source. The transmitter 110 can include a coil TX and can drive the coil TX to generate a magnetic field. The transmitter 110 can be configured to drive the coil TX within a frequency range and configuration range defined by a wireless power standard, such as the Wireless Power Alliance (Qi) standard, the Power Matters Alliance (PMA) standard, the Alliance for Wireless Power (A for WP or Rezence) standard, or any other wireless power standard.

[0020] The receiver 120 can be configured to receive the AC power 130 transmitted by the transmitter 110 and supply the power to one or more loads 126 or other components of a target device. The load 126 can include, for example, a battery charger configured to charge a battery of a target device, such as a computing device, a mobile device, a mobile phone, a smart device, a tablet, a wearable device, or any other electronic device configured to wirelessly receive power. In one embodiment, the target device can include the receiver 120. In other embodiments, the receiver 120 can be provided separately from the target device, with the receiver 120 being connected to the target device via wires or other components that provide power to the target device.

[0021] The receiver 120 may include a controller 122 and a power rectifier 124. The controller 122 may include, for example, a processor, a central processing unit (CPU), a field programmable gate array (FPGA), or any other circuit that can be configured to control and operate the power rectifier 124. The power rectifier 124 includes a coil RX and is configured to rectify power received via the coil RX into the type of power required by the load 126. The power rectifier 124 is configured to rectify the AC power received from the coil RX into DC power 132, which is then supplied to the load 126.

[0022] For example, when the receiver 120 is placed near the transmitter 110, the magnetic field generated by the coil TX induces a current in the coil RX of the power rectifier 124. The induced current causes AC power 130 to be inductively transferred from the transmitter 110 to the power rectifier 124. The power rectifier 124 receives the AC power 130 and converts the AC power 130 into DC power 132. The DC power 132 is then provided by the power rectifier 124 to the load 126.

[0023] Transmitter 110 and receiver 120 are also configured to exchange information or data, such as messages, via inductive coupling between transmitter 110's power driver and power rectifier 124. For example, before transmitter 110 begins transmitting power to receiver 120, a power agreement may be established between receiver 120 and transmitter 110. In another example, in response to receiver 120 being brought into proximity with transmitter 110, e.g., close enough to form a transformer with coils TX and RX to allow power transfer, receiver 120 may be configured to initiate communication by sending a signal to transmitter 110 requesting power transfer. At this point, transmitter 110 may respond to the request from receiver 120 by establishing a power agreement or, if a power agreement already exists, by beginning to transmit power to receiver 120. Transmitter 110 and receiver 120 may transmit and receive communication packets, data, or other information via inductive coupling between coils TX and RX. In some embodiments, communication between the transmitter 110 and the receiver 120 may occur prior to the power transfer phase using various protocols such as near field communication (NFC), Bluetooth, and the like.

[0024] In one aspect, the receiver coil of a wireless power receiver can be made using multiple strands of wire (e.g., Litz wire or a wire comprising multiple strands). Using multiple strands of wire can reduce the skin depth effect, which refers to the tendency of alternating current (AC) to shift from the center of the wire to the surface of the wire. Depending on the shape of the receiver coil, the multiple strands can have different lengths. For example, if the receiver coil includes two strands of wire, such as an inner strand and an outer strand, arranged in parallel paths around the center to form a loop (e.g., a circular loop, a rectangular loop, or other loop shape), the inner strand (e.g., the strand closer to the center) will be shorter than the outer strand (e.g., the strand farther from the center). This difference in length can cause the multiple strands to experience different magnetic flux generated by the AC current generated by the AC power received by the receiver coil. For example, because the outer strand occupies more area of ​​the receiver coil (e.g., has a longer length), it can experience more magnetic flux than the inner strand. The difference in magnetic flux experienced by the strands of different sizes (e.g., different lengths) can induce a loop current between the strands, which can be converted into heat, thereby increasing the temperature of the receiver.

[0025] Figure 1 A receiver coil configuration for reducing skin depth effects and loop currents is shown. The coil RX of the receiver 120 may include a plurality of strands (e.g., coils or wires) arranged into at least a first coil layer 140 ("first layer 140") and a second coil layer 142 ("second layer 142"). In one embodiment, the first layer 140 may be arranged on a first plane z1 and the second layer 142 may be arranged on a second plane z2, wherein the first plane z1 and the second plane z2 are parallel, two-dimensional planes within the xy plane. The first layer 140 and the second layer 142 may be adjacent to each other in a direction (e.g., the z-direction or vertical direction) perpendicular to the first plane z1 and the second plane z2 (and perpendicular to a horizontal or transverse plane, such as the xy plane).

[0026] The multiple strands in the coil RX may be flexible printed coils (FPC). The multiple strands may be arranged into a first layer 140 and a second layer 140. The multiple strands may span the width of the coil RX and alternately loop between the first layer 140 and the second layer 142 to simulate the twisting of a multi-strand coil (e.g., simulating a coil made of Litz wire). For example, a portion 144 of the first layer 140 and a portion 146 of the second layer 142 may be arranged in a first layer 140 and a second layer 142. Figure 1 . In portion 144, multiple strands can be parallel and extend laterally (e.g., on the z1 plane) in a lateral direction toward +x and +y (e.g., from y1 to y2). In portion 146, multiple strands can be parallel and extend laterally (e.g., on the z2 plane) in another lateral direction toward +x and -y (e.g., from y2 to y1). On the first layer 140, if one strand reaches an edge, such as y2, the strand can wrap around to the bottom layer or second layer 142 and begin to stretch or extend toward y1. When the strand reaches y1 in the second layer 142, the strand can wrap around to the top layer, such as the first layer 140, and stretch or extend toward y2. The repeated stretching and wrapping between vertical layers can simulate the twisting of the Litz wire structure, and this stretching and wrapping can allow the multiple strands forming the coil RX to have equal lengths, thereby reducing skin depth effects, proximity effects, and loop currents. Conventional Litz wire can reduce skin depth effects because its twisted configuration allows wiring to be of approximately the same length. However, Litz wire is relatively thick and expensive. Lateral extension of the width of the FPC jumper coil RX and the FPC wrapping between different vertical layers to simulate Litz wire can provide a receiver coil that can be constructed to be relatively small and / or thin while reducing skin depth effects and loop currents.

[0027] Figure 2A 、 2B2C are schematic diagrams illustrating components of a receiver that can implement a planar Litz coil for wireless power transfer in one embodiment. Figure 1 )exist Figure 2A In Figure 2A In the embodiment shown, a plurality of strands A to H (e.g., 8 strands) may form a coil RX. Different subsets of the plurality of strands may be parallel at different portions of the first layer 140. For example, Figure 2B As shown, strands A, B, C, and D may be parallel until strand A reaches a fixed point 208 along the length of coil RX and is rewound to another layer via a set of rewinding desirably 202, such as Figure 1 In addition, as strand A is wrapped back into the second layer 142, strand E is wrapped back from the second layer 142 into the first layer 140 at the fixing point 208.

[0028] Reference Figure 2C In order to wrap around between different layers, each strand can be divided into different parts, and the different parts can overlap at the wrap-around holes so that the conductive contacts can be inserted into the overlapping wrap-around holes. Figure 2C In the cross-sectional area 210 shown, strands F, G, H, and A are parallel on the second layer 142 or plane z2, and strands E, D, C, and B are parallel on the first layer 140 or plane z1. In one embodiment, a substrate layer, such as a layer of dielectric material or other type of non-conductive material, can be positioned between the first layer 140 and the second layer 142.

[0029] As the coil RX progresses from the cross-sectional area 210 to the other cross-sectional area 211 along the length of the coil RX, the width of the plurality of strands may decrease to accommodate the strands wrapping back from the first layer 140 to the second layer 142. Figure 2C In the example shown, cross-sectional area 211 includes strands F, E, D, C, B on first layer 140 and strands F, G, H, A, B on second layer 142. Strands F and B include different portions on first layer 140 and second layer 142, and the different portions are portions that include wraparound holes. Conductive contacts 212 can connect the different portions of strand F, and conductive contacts 214 can connect the different portions of strand B. Conductive contacts 212, 214 can be, for example, metal vias. After the wraparound holes are used to make the connections, as coil RX advances from cross-sectional area 211 to another cross-sectional area along the length of coil RX, strand F is no longer on second layer 142, strand B is no longer on first layer 140 (until the next fixed point along the length of coil RX), and the width of the strands can increase again.

[0030] Figure 3A is a schematic diagram illustrating a perspective view of an example receiver coil that may implement a planar Litz coil for wireless power transfer in one embodiment. Figure 3A A perspective view of a receiver coil 300 is shown. The receiver coil 300 may be implemented Figure 1 The receiver coil 300 may be made using two layers of coils, such as the first layer 140 and the second layer 142 described herein. The coil layers forming the receiver coil 300 may be flexible printed circuits (FPCs). Using FPCs to construct the receiver coil 300 may allow the receiver coil 300 to have any shape and / or size. For example, the receiver coil 300 may be a shape such as circular, rectangular, or any other shape. Figure 3A In the example shown in , the receiver coil 300 may form a ring around a center 301 .

[0031] Receiver coil 300 may include eight strands of wire connected at connector 302. Connector 302 may be a conductive pad made of a conductive material. At connector 302, four strands of wire may extend from connector 302 toward first layer 140, and another four strands of wire may extend from connector 302 toward second layer 142. At a fixed point every 90 degrees around center 301, one of the strands on first layer 140 may wrap around to second layer 142, and one of the strands on second layer 142 may wrap around to first layer 140. For example, at fixed point 308, the outermost strand of the four strands on first layer 140 extending from connector 302 (e.g., furthest from center 301, see FIG. 3 ). Figure 2A and 2C Likewise, at the fixing point 308, the innermost strand (e.g., closest to the center 301, see 2A and 2B) of the four strands extending from the connector 302 on the second layer 142 is wound back to the second layer 142. Figure 2C The strand E) in the first layer 140 can be wrapped back to the first layer 140. After the outermost strand on the first layer 140 is wrapped back to the second layer 142 at the fixing point 308, the adjacent strands (e.g., see 2A and Figure 2C The strand B in the second layer 142 may become the outermost strand on the first layer 140 until the next fixing point 310. In addition, after the innermost strand on the second layer 142 wraps back to the first layer 140 at the fixing point 308, the adjacent strands of the wrapped innermost strand (e.g., see 2A and Figure 2C The strand F) in the middle can become the innermost strand on the second layer 142 until the next fixed point 310.

[0032] Figure 3B An embodiment is shown Figure 3ASchematic diagram of a top view of an example receiver coil. The multiple strands forming receiver coil 300 may be parallel to one another. The innermost strand 312 ("innermost 312") may be the strand closest to center 301, and the outermost strand 310 ("outermost 310") may be the strand farthest from center 301. Each of the multiple strands may be twisted or wrapped around center 301 every 90 degrees. Further, each strand may extend a width in a first lateral direction (e.g., away from center 301) of receiver coil 300 before being twisted, and then extend in a second direction (e.g., toward center 301) after being twisted or wrapped around another layer. Because the strands repeatedly extend across the width of receiver coil 300 in different directions on different layers and are twisted at regular intervals (e.g., 90 degrees), the multiple strands may have equal lengths (or nearly equal lengths) when measured from the starting point at connector 302 to the end point 320 ("end point 320") of receiver coil 300. Having multiple strands of the same length can reduce the difference between the magnetic fluxes experienced by different strands in the receiver coil 300, thereby reducing the loop current. On the one hand, a multi-strand coil such as the receiver coil 300 can reduce skin depth effects, but having multiple strands of wire of different lengths can increase the loop current. Therefore, a receiver coil 300 (or other receiver coils described herein, such as the receiver coil 300) having multiple strands of wire of the same length can reduce the difference between the magnetic fluxes experienced by different strands in the receiver coil 300, thereby reducing the loop current. Figure 1 The coil RX in the circuit can reduce the skin depth effect and loop current.

[0033] When multiple strands extend from the receiver coil 300, the multiple strands may reach the fixed point multiple times along the length of the receiver coil 300. For example, Figure 3A The receiver coil 300 shown in FIG is wound around the center 301 four times in total, and the fixed points 308, 310 and other fixed points are passed by the plurality of strands four times. Therefore, each strand of the plurality of strands can be wound back four times between the first layer 140 and the second layer 142, including two times from the first layer 140 to the second layer 142 and two times from the second layer 142 to the first layer 140. Figure 3B , the outermost strand 310 may extend from the connector 302, and when it reaches the fixing point 308, the outermost strand 310 may wrap back around the second layer 142, as indicated by the protruding mark 330. The outermost strand 310 may wrap back around the center 301 and reach the fixing point 308 again, as indicated by the protruding mark 332. The outermost strand 310 may wrap back from the second layer 142 to the first layer 140 and wrap around the center 301 again on the first layer 140. When the outermost strand 310 reaches the fixing point 308 again, as indicated by the protruding mark 332, the outermost strand 310 may wrap back from the first layer 140 to the second layer 142 again.

[0034] Figure 4A is a schematic diagram illustrating a perspective view of an example receiver coil that may implement a planar Litz coil for wireless power transfer in one embodiment. Figure 4A A perspective view of the receiver coil 400 is shown in FIG. The receiver coil 400 may be implemented Figure 1 The receiver coil 400 may be made using two layers of coils, such as the first layer 140 and the second layer 142 described herein. The coil layers forming the receiver coil 400 may be flexible printed circuits (FPCs). Using FPCs to construct the receiver coil 400 may allow the receiver coil 400 to have any shape and / or size. For example, the receiver coil 400 may be in any shape such as circular, rectangular, or other arbitrary shape. Figure 4A In the example shown in , the receiver coil 400 may form a ring around a center 401 .

[0035] Receiver coil 400 may include eight strands of wire connected at connector 402. Connector 402 may be a conductive pad made of a conductive material. At connector 402, four strands of wire may extend from connector 402 toward first layer 140, and another four strands of wire may extend from connector 402 toward second layer 142. At fixed points every 45 degrees around center 401, one of the strands on first layer 140 (e.g., the outermost strand) may be looped back to second layer 142, and one of the strands on second layer 142 (e.g., the innermost strand) may be looped back to first layer 140.

[0036] Figure 4B In one embodiment, Figure 4A Schematic diagram of a top view of an exemplary receiver coil. The multiple strands forming receiver coil 400 may be parallel to one another. The innermost strand 412 ("innermost 412") may be the strand closest to center 401, and the outermost strand 410 ("outermost 410") may be the strand farthest from center 401. Each of the multiple strands may be twisted or wrapped around center 401 every 45 degrees. Further, each strand may extend for a width in a first lateral direction (e.g., away from center 401) of receiver coil 400 before being twisted, and then extend in a second direction (e.g., toward center 401) after being twisted or wrapped around another layer. Because the strands are repeatedly stretched across the width of receiver coil 300 in different directions and on different layers and twisted at regular intervals (e.g., 45 degrees), the multiple strands may have equal lengths (or nearly equal lengths) when measured from the starting point at connector 402 to the ending point 420 ("end point 420") of receiver coil 400. Having multiple strands of the same length can reduce the difference between the magnetic fluxes experienced by the different strands in the receiver coil 400, thereby reducing loop currents. Figure 3A In the receiver coil 300, the receiver coil 400 having multiple wires of the same length can reduce the skin depth effect and the loop current.

[0037] Figure 5is a diagram illustrating a series of steps for rewinding a strand from one layer to another in one embodiment. In step 501, FPC 510 may be printed or bonded to the upper surface of substrate 508. FPC 510 may be a metal trace layer, such as copper traces, and substrate 508 may be a dielectric layer, such as polyimide. In one embodiment, FPC 510 may be relatively thin, such as less than 0.2 millimeters (0.2 mm). In one embodiment, FPC 510 may be bonded to the upper surface of substrate 508 using an adhesive material or other bonding method, such as vapor deposition. In one embodiment, FPC 510 may be covered with a protective layer, such as gold or solder. In one embodiment, FPC 510 may be printed as a pattern on the upper surface of substrate 508. For example, a panel coated with photoresist may be covered with the pattern of the first and second coil layers, and the covered photoresist-coated panel may be exposed with collimated UV light to transfer the pattern to the product panel. The pattern may be chemically etched using a conveyor system equipped with specialized thin core processing equipment. High-speed, high-precision, small-hole drilling systems can be used to create the desired hole pattern in the product panel, or laser-based systems can be used for ultra-small hole requirements. Figure 5 In the illustrated embodiment, the FPC 510 pattern may include a set of openings, such as at least one wrap-around hole 512 .

[0038] Continuing to step 502, in response to bonding FPC 510 to the upper surface of substrate 508, an opening or hole 509 may be formed in substrate 508. Hole 509 may be formed, for example, by etching through substrate 508 using the pattern of FPC 510 (e.g., wraparound hole 512) as an etch mask. Hole 509 may be aligned with wraparound hole 12 of FPC 510.

[0039] Continuing to step 503, in response to forming the hole 509 in the substrate 508, another FPC 520 may be printed onto or bonded to the lower surface of the substrate 508. The FPC 520 may be a metal trace layer, such as a copper trace, and the FPC 520 may be composed of the same material as the FPC 510. In one embodiment, the FPC 520 may be relatively thin, such as less than two millimeters (2 mm). In one embodiment, the FPC 520 may be bonded to the lower surface of the substrate 508 using an adhesive material or other bonding method such as vapor deposition. In one embodiment, the FPC 520 may be covered with a protective layer such as gold or solder. In one embodiment, the FPC 520 may be printed as a pattern on the lower surface of the substrate 508 using techniques similar to those described above for printing the FPC 510. Figure 5 In the embodiment shown, the pattern of FPC 520 may include a set of openings, such as at least one wraparound hole 522. FPC 520 may be printed on the lower surface of substrate 508, and wraparound hole 522 may be aligned with hole 509 of substrate 508 and wraparound hole 512 of FPC 510.

[0040] Continuing to step 502, in response to bonding FPC 510 to the bottom surface of substrate 508, contacts 522 may be inserted into wraparound holes 512 of FPC 510, holes 509 of substrate 508, and wraparound holes 522 of FPC 520. Contacts 522 may be, for example, solder bumps, metal bonding pads, and / or other types of conductive or metallic contacts. Insertion of contacts 522 connects FPC 510 to FPC 520 and allows current flowing through FPC 510 to continue to flow through FPC 520. Steps 501 to 504 may be repeated to alternately twist or wrap between the top and bottom surfaces of substrate 508 to form a receiver coil, such as the one described above. Figures 1 to 4B The receiver coil shown in . Figures 1 to 2B In the example shown, the upper surface of substrate 508 may be where the first layer 140 is printed, and the lower surface of substrate 508 may be where the second layer 142 is printed. Further alignment and lamination processes may be performed to package multiple FPCs as receiver coils.

[0041] Figure 6 6 is a flow chart illustrating a process for constructing a planar Litz coil for wireless power transfer in one embodiment. The process may include one or more operations, actions, or functions illustrated by one or more of blocks 602, 604, and / or 606. Although illustrated as discrete blocks, various blocks may be divided into additional blocks, combined into fewer blocks, eliminated, performed in a different order, or performed in parallel, depending on the desired implementation.

[0042] Process 600 can be performed to construct a coil for a device, such as a receiver coil for a wireless power receiver. Process 600 can begin at block 602. At block 602, a plurality of strands can be bonded to a substrate to form a first coil layer and a second coil layer. The plurality of strands can extend away from the center on the first coil layer and toward the center on the second coil layer. In one embodiment, bonding the plurality of strands to the substrate is accomplished by bonding a flexible printed circuit (FPC) to the substrate.

[0043] From block 602, process 600 may proceed to block 604 and / or block 606. Block 604 and / or block 606 may be performed at each fixed point on the substrate. At block 604, a first strand of the plurality of strands may be rewound from the first coil layer to the second coil layer. At block 606, a second strand of the plurality of strands may be rewound from the second coil layer to the first coil layer.

[0044] In one embodiment, the first strand can be rewound by rewinding the outermost strand of the plurality of strands from the first coil layer to the second coil layer. The second strand can be rewound by rewinding the innermost strand of the plurality of strands from the second coil layer to the first coil layer. In one embodiment, in response to the first strand being rewound from the first coil layer to the second coil layer, the strand adjacent to the first strand can become the new outermost strand of the plurality of strands on the first coil layer. Furthermore, in response to the second strand being rewound from the second coil layer to the first coil layer, the strand adjacent to the rewound second strand can become the new innermost strand of the plurality of strands on the second coil layer.

[0045] In one embodiment, the first strand can be wound back from the first coil layer to the second coil layer by connecting the first portion of the first strand on the first coil layer to the second portion of the first strand on the second coil layer using a first set of contacts. Furthermore, the second strand can be wound back from the second coil layer to the first coil layer by connecting the first portion of the second strand on the first coil layer to the second portion of the second strand on the second coil layer using a second set of contacts.

[0046] The flowcharts and block diagrams in the accompanying drawings illustrate the architecture, functionality, and operation of possible implementations of the systems, methods, and computer program products according to various embodiments of the present invention. In this regard, each box in the flowchart or block diagram may represent a module, an instruction segment, or an instruction portion, which includes one or more executable instructions for implementing a specified logical function. In some optional embodiments, the functions marked in the box may not occur in the order marked in the figure. For example, two blocks shown in succession may actually be executed substantially simultaneously, or the boxes may sometimes be executed in the opposite order, depending on the functions involved. It should also be noted that each box in the block diagram and / or flowchart, and the combination of boxes in the block diagram and / or flowchart, may be implemented by a dedicated hardware-based system that performs a specified function or action or performs a combination of dedicated hardware and computer instructions.

[0047] The terms used herein are for the purpose of describing specific embodiments only and are not intended to limit the present invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It should also be understood that when the term "comprising" is used in this specification to specify the presence of the features, wholes, steps, operations, elements and / or parts, it does not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, parts and / or combinations thereof.

[0048] In the claims below, the corresponding structures, materials, actions and equivalents of all means or step plus function elements, if any, are intended to include any structure, material or action for performing a function in conjunction with other claimed elements for specific protection. The above description of the application is for the purpose of illustration and description, but is not intended to be exhaustive or limited to the disclosed form. Without departing from the scope and spirit of the invention, many modifications and variations will be apparent to those of ordinary skill in the art. This embodiment is selected and described in order to best explain the principles of the invention and practical applications, and to enable other persons of ordinary skill in the art to understand the present invention for various embodiments with various modifications suitable for the specific use intended.

Claims

1. A structure comprising: A plurality of strands arranged into a first coil layer and a second coil layer, wherein: The plurality of strands are formed in parallel paths about a center of the structure; the plurality of strands extending away from the center on the first coil layer; The plurality of strands extend toward the center on the second coil layer; and For each fixed interval along the length of the structure: A first strand of the plurality of strands is wound back from the first coil layer to the second coil layer; and A second strand of the plurality of strands is wound back from the second coil layer to the first coil layer.

2. The structure according to claim 1, wherein The plurality of strands are flexible printed circuit (FPC) coils.

3. The structure according to claim 1, wherein The plurality of strands have the same length.

4. The structure according to claim 1, wherein: The first coil layer is arranged on a first plane; The second coil layer is arranged on a second plane; as well as The first coil layer and the second coil layer are adjacent to each other in a direction perpendicular to the first plane and the second plane.

5. The structure according to claim 1, wherein The first coil layer and the second coil layer are parts of a wireless power receiver.

6. The structure of claim 1, wherein: the first strand being an outermost strand of the plurality of strands on the first coil layer; and The second strand is an innermost strand among the plurality of strands on the second coil layer.

7. The structure according to claim 6, wherein: In response to the first strand being wound back from the first coil layer to the second coil layer, a strand adjacent to the first strand becomes a new outermost strand among the plurality of strands on the first coil layer; and In response to the second strand being wound back from the second coil layer to the first coil layer, a strand adjacent to the wound back second strand becomes a new innermost strand among the plurality of strands on the second coil layer.

8. The structure of claim 1, wherein: looping the first strand from the first coil layer to the second coil layer by connecting a first portion of the first strand on the first coil layer to a second portion of the first strand on the second coil layer using a first set of contacts; as well as The second strand is looped back from the second coil layer to the first coil layer by connecting the first portion of the second strand on the first coil layer to the second portion of the second strand on the second coil layer using a second set of contacts.

9. A device comprising: Power rectifiers for converting alternating current (AC) power into direct current (DC) power; a controller connected to the power rectifier, the controller being configured to control the power rectifier; Structure for receiving said AC power, said structure comprising a plurality of strands arranged into a first coil layer and a second coil layer, wherein: The plurality of strands are formed in parallel paths about a center of the structure; the plurality of strands extending away from the center on the first coil layer; The plurality of strands extend toward the center on the second coil layer; and For each fixed interval along the length of the structure: A first strand of the plurality of strands is wound back from the first coil layer to the second coil layer; and A second strand of the plurality of strands is wound back from the second coil layer to the first coil layer.

10. The apparatus according to claim 9, wherein The plurality of strands are flexible printed circuit (FPC) coils.

11. The apparatus according to claim 9, wherein The controller, the power rectifier, and the structure are part of a wireless power receiver.

12. The apparatus of claim 9, wherein: The first coil layer is arranged on a first plane; The second coil layer is arranged on a second plane; and The first coil layer and the second coil layer are adjacent to each other in a direction perpendicular to the first plane and the second plane.

13. The apparatus according to claim 9, wherein The plurality of strands have the same length.

14. The apparatus of claim 9, wherein: the first strand being an outermost strand of the plurality of strands on the first coil layer; the second strand being an innermost strand of the plurality of strands on the second coil layer; In response to the first strand being wound back from the first coil layer to the second coil layer, a strand adjacent to the first strand becomes a new outermost strand among the plurality of strands on the first coil layer; and In response to the second strand being wound back from the second coil layer to the first coil layer, a strand adjacent to the wound back second strand becomes a new innermost strand among the plurality of strands on the second coil layer.

15. The apparatus of claim 14, wherein: looping the first strand from the first coil layer to the second coil layer by connecting a first portion of the first strand on the first coil layer to a second portion of the first strand on the second coil layer using a first set of contacts; as well as The second strand is looped back from the second coil layer to the first coil layer by connecting the first portion of the second strand on the first coil layer to the second portion of the second strand on the second coil layer using a second set of contacts.

16. A method for constructing a coil of a device, the method comprising: bonding a plurality of strands to a substrate to form a first coil layer and to a second coil layer, wherein the plurality of strands extend away from the center on the first coil layer and extend toward the center on the second coil layer; At each fixed point on the substrate: rewinding a first strand of the plurality of strands from the first coil layer to the second coil layer; and A second strand of the plurality of strands is looped back from the second coil layer to the first coil layer.

17. The method according to claim 16, wherein Bonding the plurality of strands to the substrate includes bonding a flexible printed coil (FPC) to the substrate.

18. The method of claim 16, wherein: Rewinding the first strand includes rewinding an outermost strand of the plurality of strands from the first coil layer to the second coil layer; and Rewinding the second strand includes rewinding an innermost strand of the plurality of strands from the second coil layer to the first coil layer.

19. The method according to claim 18, wherein: In response to the first strand being wound back from the first coil layer to the second coil layer, a strand adjacent to the first strand becomes a new outermost strand among the plurality of strands on the first coil layer; and In response to the second strand being wound back from the second coil layer to the first coil layer, a strand adjacent to the wound back second strand becomes a new innermost strand among the plurality of strands on the second coil layer.

20. The method of claim 16, wherein: Looping the first strand from the first coil layer to the second coil layer includes: connecting a first portion of the first strand on the first coil layer to a second portion of the first strand on the second coil layer using a first set of contacts; and Looping the second strand from the second coil layer back to the first coil layer includes connecting a first portion of the second strand on the first coil layer to a second portion of the second strand on the second coil layer using a second set of contacts.

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