Differential rectifier for use in a wireless power receiver and method for rectifying a power signal - Patents.com

Abstract

A differential rectifier for use in a receiver for receiving wireless power by inductive coupling, comprising first and second capacitors, first and second switching elements, and first and second inductors. The first capacitor and the first inductor are electrically connected in series, and the second capacitor and the second inductor are electrically connected in series. The first switching element is connected in parallel between the first capacitor and the first inductor, and the second switching element is connected in parallel between the second capacitor and the second inductor. The first capacitor is electrically connected to a terminal of the coil for wirelessly receiving power by inductive coupling, and the second capacitor is electrically connected to another terminal of the coil for wirelessly receiving power by inductive coupling. The first and second switching elements are electrically connected to taps of the coil for wirelessly receiving power by inductive coupling.

Description

[Technical field]

[0001] The present disclosure relates generally to wireless power transfer, and in particular to a differential rectifier for use in a receiver to receive wireless power by inductive coupling, a receiver and coil for use in a wireless power transfer system, a load independent inverter, and a method for rectifying a power signal received at a receiver of a wireless power transfer system. [Background technology]

[0002] Wireless power transfer systems, such as wireless charging, are becoming an increasingly important technology for powering the next generation of devices. The potential benefits and advantages offered by this technology are evident as more and more manufacturers and companies are investing in this technology.

[0003] Various wireless power transfer systems are known. A typical wireless power transfer system includes a power source electrically connected to a wireless power transmitter and a wireless power receiver electrically connected to a load.

[0004] In magnetic induction systems, the transmitter has a transmitter coil with some inductance that transfers electrical energy from a power source to a receiver, and the receiver has a receiver coil with some inductance. Power transfer occurs through magnetic field coupling between the transmitter and receiver coils or inductors. These magnetic induction systems have a limited range, and the transmitter and receiver coils or inductors must be tightly coupled, i.e., have a coupling coefficient greater than 0.5, and be optimally aligned for efficient power transfer.

[0005] There are also resonant magnetic systems in which power is transferred by the coupling of magnetic fields between the coils or inductors of the transmitter and receiver. The inductors of the transmitter and receiver may be loosely coupled, i.e., have a coupling coefficient below 0.5. However, in resonant magnetic systems, the inductors are resonated using at least one capacitor. Furthermore, in resonant magnetic systems, the transmitter is self-resonant and the receiver is self-resonant. The range of power transfer in resonant magnetic systems is increased beyond that of magnetic induction systems, and alignment problems are reduced. While electromagnetic energy is generated in magnetic induction and resonant magnetic systems, the majority of power transfer is done by magnetic fields. Little, if any, power is transferred by electrical induction or resonant electrical induction.

[0006] In an electrical induction system, the transmitter and receiver have capacitive electrodes. Power transfer occurs through the coupling of an electric field between the capacitive electrodes of the transmitter and receiver. Similar to resonant magnetic systems, there are resonant electrical systems where the capacitive electrodes of the transmitter and receiver are created using at least one inductor. The inductor may be a coil. In resonant electrical systems, the transmitter is self-resonant and the receiver is self-resonant. Resonant electrical systems increase the range of power transfer compared to that of electrical induction systems and correct alignment issues. While electromagnetic energy is generated in electrical induction and resonant electrical systems, the majority of the power transfer occurs through the electric field. Little, if any, power is transferred by magnetic induction or resonant magnetic induction.

[0007] Although some wireless power transfer systems are known, improvements are desirable. It is therefore an object to provide novel wireless power transfer transmitters, receivers, systems and methods for wirelessly transferring power.

[0008] This background merely serves to set the context so that those skilled in the art can better appreciate the following brief detailed description. Thus, nothing in the above should necessarily be construed as an admission that the description is part of the state of the art or is commonly known fact. One or more aspects / embodiments described below may or may not address one or more of the background problems. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] U.S. Patent Application Publication No. 2021 / 0083634A1 [Patent Document 2] U.S. Patent No. 9,653,948 [Patent Document 3] U.S. Patent No. 11,139,690 [Patent Document 4] U.S. Patent Application Serial No. 17 / 472,002 Summary of the Invention [Means for solving the problem]

[0010] Thus, in one aspect, a differential or push-pull rectifier is provided for use in a receiver for wirelessly receiving power. The power may be received by inductive or magnetic coupling. Inductive coupling is the generation of a current by electromagnetic induction from a magnetic field. In wireless power transfer, a transmitter may generate a magnetic field, which induces a current in the receiver when the receiver is placed within the generated field.

[0011] The signal received at the receiver is a differential alternating current (AC) signal. In many applications, the receiver load requires a direct current (DC) signal. A rectifier is used to rectify the received AC signal to the required DC signal.

[0012] The described differential rectifiers may improve efficiency and performance compared to conventional rectifiers. Furthermore, the described differential rectifiers may include fewer components than conventional rectifiers. This may result in a rectifier with reduced size, and therefore useful in a wider variety of applications.

[0013] The differential rectifier may be for use with a receiver coil of a receiver of a wireless power transfer system. The coil may be for extracting power from a generated field by induction or magnetic field coupling. The coil may extract power by resonant magnetic field coupling. The coil may be center tapped.

[0014] The differential rectifier may include a pair of capacitive elements, a pair of switching elements, and a pair of inductive elements. Each capacitive element may include a capacitor. Each switching element may include a switch, such as an active switch, a diode, or a field effect transistor (FET). Each inductive element may include an inductor.

[0015] The differential rectifier may include as few as two switching elements or diodes, which may provide a rectifier that has fewer diodes and therefore occupies less space than a conventional rectifier, which may therefore be useful in applications where there are size constraints.

[0016] The inductor may include an iron-core inductor. The inductor may include an air-core inductor.

[0017] The diode may include a Schottky diode.

[0018] The first capacitor and the first inductor may be electrically connected in series. The second capacitor and the second inductor may be electrically connected in series. The first switching element may be electrically connected in parallel between the first capacitor and the first inductor. The second switching element may be electrically connected in parallel between the second capacitor and the second inductor. The first capacitor may be electrically connected to a terminal of the coil to wirelessly receive power by inductive coupling. The second capacitor may be electrically connected to another terminal of the coil to wirelessly receive power by inductive coupling. The first and second switching elements may be electrically connected to a tap of the coil to wirelessly receive power by inductive coupling.

[0019] The differential rectifier may further include a capacitor electrically connected in parallel to one of the first and second switching elements. The capacitor may damp or reduce voltage ringing at the rectifier. Voltage ringing may adversely affect power transfer because the load does not receive a stable power signal. Thus, reducing or damping the voltage ringing may improve the stability of the power signal received at the load.

[0020] The capacitor may have a capacitance equal to 0.175 divided by the operating frequency multiplied by the output load. The operating frequency may be the operating frequency of the differential rectifier. In other words, the capacitance of the capacitor may be given by the following formula:

[0021]

number

[0022] The rectifier may be a passive rectifier.

[0023] The rectifier may be current driven: the AC current input to the rectifier, and therefore output by the receiving coil, may have a constant amplitude regardless of the load.

[0024] Because the rectifier is current driven, the rectifier may provide a constant DC current that is independent of the load. Because the output of the rectifier is a constant DC current, a DC / DC converter may not be required between the rectifier and the load. This may result in a reduced space, making the rectifier suitable for a specific application or a broader range of applications.

[0025] According to another aspect, a receiver for use in a wireless power transfer system is provided, the receiver for receiving power by inductive coupling.

[0026] The receiver may include any of the differential rectifiers described.

[0027] The receiver may further comprise a coil for extracting power from the generated field by inductive coupling.

[0028] The coil may include at least two windings, with an outer turn of a first winding and an inner turn of a second winding forming a first sub-coil of the coil, and an inner turn of the first winding and an outer turn of the second winding forming a second sub-coil of the coil.

[0029] A winding is understood to include both an outer turn and an inner turn. Additionally, a winding may include one or more turns between the inner turn and the outer turn. For example, a winding may be defined by an outer turn, n turns, and an inner turn.

[0030] A turn is understood to define a circumferential loop or path around an enclosed area or volume.

[0031] The coil may include three or more windings. Each winding may include more than two turns, for example, four, six, eight, or more turns. The turns may be interconnected such that the turns are mirrored about a central axis of a plane defined by the windings. For example, if there are four turns, the first turn may be connected to the third turn, the second turn may be connected to the fourth turn, and so on.

[0032] The coil may be generally planar. In other words, the turns of the winding of the coil may be in the same plane. One skilled in the art will recognize that while the windings are generally in the same plane, portions of the windings may be out of plane to connect the turns. For example, the windings may be in the same layer of a printed circuit board (PCB), but the turns are connected on adjacent layers of the same PCB.

[0033] The coil may comprise a first sub-coil comprising an outer turn of a first winding of the coil and an outer turn of a second winding of the coil, and a second sub-coil comprising an inner turn of the first winding and an inner turn of the second winding.

[0034] The first terminal may be formed at an end of an outer or inner turn of the first winding, and the second terminal is formed at an end of an outer or inner turn of the second winding.

[0035] A tap or third terminal may be formed between the first and second terminals to split the coil into a first and a second sub-coil. The tap may be approximately at the center of the coil, i.e., a center tap.

[0036] The first and second switching elements of the differential rectifier may be electrically connected to the tap.

[0037] The first inductor may be electrically connected to the first terminal.The first capacitor may be electrically connected to the first terminal.

[0038] The second inductor may be electrically connected to the second terminal.The second capacitor may be electrically connected to the second terminal.

[0039] The second capacitor and the second inductor may be electrically connected in series with a second switching element electrically connected in parallel between the second capacitor and the second inductor.

[0040] The first capacitor and the first inductor may be electrically connected in series with a first switching element electrically connected in parallel between the first capacitor and the first inductor.

[0041] The second inductor may comprise a second iron-core or air-core inductor.

[0042] The second switching element may include a switch, such as an active switch, a diode, such as a Schottky diode, or a FET.

[0043] The coil may include at least two windings, an outer turn of a first winding and an inner turn of a second winding forming a first sub-coil of the coil, an inner turn of the first winding and an outer turn of the second winding forming a second sub-coil of the coil, a first terminal formed at an end of the outer or inner turn of the first winding and a second terminal formed at an end of the outer or inner turn of the second winding, and a tap formed between the first and second terminals to divide the coil into the first and second sub-coils, the tap being electrically connected to ground.

[0044] At least one of the windings may include one or more additional turns between the inner turn and the outer turn. The winding may include n additional turns between the inner turn and the outer turn, where n is a positive integer greater than or equal to 1.

[0045] The coil may include one or more additional windings. The coil may include n additional windings, where n is a positive integer greater than or equal to 1.

[0046] The receiver may further comprise at least one additional inductor electrically connected to one of the terminals or taps of the coil. The additional inductor may beneficially minimize distortion and / or improve the performance of the rectifier.

[0047] The additional inductor may be electrically connected to the first terminal, the second terminal, or the tap of the coil.

[0048] The diodes can cause distortion when in the off state. The distortion can include additional second and / or third harmonics. As a result of the distortion, the rectifier may no longer be able to produce the required output current, i.e. the current may be less or more than required by the load.

[0049] The additional inductor can minimize distortion and therefore reduce its impact on the rectifier performance. The inductor's inductance value can be selected based on the diode junction capacitance. The value can be up to 100 nH.

[0050] The receiver may further include a third inductor electrically connected to the first terminal of the coil and a fourth inductor electrically connected to the second terminal of the coil. The third and fourth inductors may introduce an inductive impedance that negates a portion of the capacitive impedance of the nonlinear junction capacitance (of the diode) of the switch element.

[0051] Additional inductors, e.g., the third and fourth inductors, may minimize distortion and therefore reduce its impact on the rectifier performance. The additional inductors introduce an impedance that negates part of the capacitive impedance of the nonlinear junction capacitance of the diode. The value of the inductance of the additional inductors depends on the value of the junction capacitance of the diode. The value may be up to 100nH.

[0052] The additional inductor may result in power loss, therefore a single additional inductor electrically connected to the coil tap may result in reduced power loss while still minimizing distortion and reducing its impact on rectifier performance.

[0053] The receiver may therefore comprise a third inductor electrically connected to a tap of the coil.

[0054] The rectifier may be a synchronous rectifier.

[0055] The rectifier may further include a first transistor electrically connected to the tap of the coil and the first terminal of the coil, and a second transistor electrically connected to the tap of the coil and the second terminal of the coil.

[0056] The rectifier may further comprise a first signal generator electrically connected to the first transistor for generating a pulse signal for driving the first transistor, and a second signal generator electrically connected to the second transistor for generating a pulse signal for driving the second transistor.

[0057] The rectifier may further include a first delay line or a first RC delay circuit electrically connected to a first terminal of the coil, the first delay line for synchronizing operation of the first transistor, and a second delay line or a second RC delay circuit electrically connected to a second terminal of the coil, the second delay line for synchronizing operation of the second transistor.

[0058] Synchronizing the operation of the first and / or second transistors may include delaying an output from the coil.

[0059] The receiver may further include a load electrically connected to the rectifier.

[0060] The receiver may further comprise a capacitor electrically connected in parallel between the inductor and the load, the capacitor for filtering the power signal output by the rectifier.

[0061] The receiver may further comprise a shield disposed adjacent the coil to protect the coil from electrical interference.

[0062] The shield may be configured to add capacitance to the coil.

[0063] The location of the tap or third terminal along the coil may be based on the distance from the coil to the shield, and may be based on the size and shape of the coil and shield.

[0064] According to another aspect, a coil in a wireless power transfer system for transferring power by inductive coupling is provided.

[0065] The coil may comprise a first sub-coil comprising an outer turn of a first winding of the coil and an outer turn of a second winding of the coil, and a second sub-coil comprising an inner turn of the first winding and an inner turn of the second winding.

[0066] The coil may comprise an outer turn of a first winding and an inner turn of a second winding forming a first sub-coil of the coil, and an inner turn of the first winding and an outer turn of the second winding forming a second sub-coil of the coil, a first terminal formed at an end of the outer or inner turn of the first winding and a second terminal formed at an end of the outer or inner turn of the second winding, and a tap formed between the first terminal and the second terminal to divide the coil into the first sub-coil and the second sub-coil, the tap being electrically connected to ground.

[0067] A winding is understood to include both an outer turn and an inner turn. Additionally, a winding may include one or more turns between the inner turn and the outer turn. For example, a winding may be defined by an outer turn, n turns, and an inner turn.

[0068] A turn is understood to define a circumferential loop or path around an enclosed area or volume.

[0069] The coil may include three or more windings. Each winding may include more than two turns, for example, four, six, eight, or more turns. The turns may be interconnected such that the turns are mirrored about a central axis of a plane defined by the windings. For example, if there are four turns, the first turn may be connected to the third turn, the second turn may be connected to the fourth turn, and so on.

[0070] The coil may be generally planar. In other words, the turns of the winding of the coil may be in the same plane. One skilled in the art will recognize that while the windings are generally in the same plane, portions of the windings may be out of plane to connect the turns. For example, the windings may be in the same layer of a printed circuit board (PCB), but the turns are connected on adjacent layers of the same PCB.

[0071] The tap may be a center tap that divides the coil approximately into half a coil. The first sub-coil may form a first half-coil. The second sub-coil may form a second half-coil.

[0072] The first and second sub-coils may be electrically balanced.

[0073] The capacitance of the first sub-coil may be approximately equal to the capacitance of the second sub-coil.

[0074] An outer turn of the first winding may at least partially overlap an outer turn of the second winding.

[0075] The inner turn of the first winding may at least partially overlap the inner turn of the second winding.

[0076] At least one of the windings may include one or more additional turns between the inner turn and the outer turn. The winding may include n additional turns between the inner turn and the outer turn, where n is a positive integer greater than or equal to 1.

[0077] The coil may include one or more additional windings. The coil may include n additional windings, where n is a positive integer greater than or equal to 1.

[0078] The coil may further comprise a shield disposed adjacent the coil to protect the coil from electrical interference.

[0079] The shield may be configured to add capacitance to the coil.

[0080] The sub-coils may be physically identical. The sub-coils may not be physically identical. The sub-coils may have the same number of turns or a different number of turns.

[0081] The location of the tap or third terminal along the coil may be based on the distance from the coil to the shield, and may be based on the size and shape of the coil and shield.

[0082] According to another aspect, a load-independent inverter is provided. The inverter can be adapted to provide a constant output voltage (constant amplitude and phase) regardless of the load. The inverter can be suitable for use with the coil, rectifier, and receiver described. The rectifier can provide a constant DC current and thus improve compatibility with the inverter that provides a constant output voltage.

[0083] The inverter may comprise a switch-mode zero-voltage switching (ZVS) amplifier comprising a pair of circuits comprising at least one transistor and at least one capacitor arranged in parallel and at least one inductor arranged in series with the transistor and capacitor, a single ZVS inductor electrically connected to the pair of circuits, an impedance transformation stage electrically connected to the ZVS inductor, and at least one capacitor electrically connected to the impedance transformation stage and arranged in series with the at least one inductor and at least one resistor.

[0084] The inverter may have a constant current output.

[0085] According to another aspect, a system for wireless power transfer is provided, the system including a receiver comprising any of the described coils and any of the described differential rectifiers electrically connected to the coils, and a transmitter comprising any of the described coils and any of the described inverters electrically connected to the transmitter coils, the transmitter and receiver coils adapted to inductively couple to transfer power from the transmitter to the receiver.

[0086] The receiver may additionally comprise a load electrically connected to the rectifier.

[0087] The transmitter may additionally include a power source electrically connected to the inverter.

[0088] According to another aspect, a method for rectifying a power signal received at a receiver of a wireless power transmission system is provided. This method can provide a constant DC current that is independent of the load. Since the output is a constant DC current, a DC / DC converter may not be required. Therefore, this method can provide a method for rectifying a power signal that requires a reduced space.

[0089] The method may include extracting power from a generated field by inductive coupling at a coil to generate an AC power signal, and rectifying the AC power signal with a differential rectifier, the differential rectifier comprising first and second capacitors, first and second switching elements, and first and second inductors, where the first capacitor and the first inductor are electrically connected in series, the second capacitor and the second inductor are electrically connected in series, the first switching element is electrically connected in parallel between the first capacitor and the first inductor, the second switching element is electrically connected in parallel between the second capacitor and the second inductor, the first capacitor is electrically connected to a terminal of the coil, the second capacitor is electrically connected to another terminal of the coil, and the first and second switching elements are electrically connected to taps of the coil.

[0090] According to another aspect, a method is provided for manufacturing a rectifier for use in a receiver, the method including integrating or manufacturing a circuit forming the rectifier, the differential rectifier circuit comprising first and second capacitors, first and second switching elements, and first and second inductors, the first capacitor and the first inductor being electrically connected in series, the second capacitor and the second inductor being electrically connected in series, the first switching element being electrically connected in parallel between the first capacitor and the first inductor, the second switching element being electrically connected in parallel between the second capacitor and the second inductor, the first capacitor being electrically connected to a terminal of the coil to receive power wirelessly by inductive coupling, the second capacitor being electrically connected to another terminal of the coil to receive power wirelessly by inductive coupling, and the first and second switching elements being electrically connected to taps of the coil to receive power wirelessly by inductive coupling.

[0091] The circuits may be manufactured by additive manufacturing. A common example of additive manufacturing is three-dimensional (3D) printing, but other methods of additive manufacturing are available. Rapid prototyping or rapid manufacturing are also terms that are sometimes used to describe the additive manufacturing process.

[0092] As used herein, additive manufacturing generally refers to a manufacturing process in which successive layers of material are laid down on top of each other to "build up" or "additively create" a three-dimensional component layer by layer. This is in comparison to some subtractive manufacturing methods (such as milling or drilling) in which material is successively removed to create a part. The successive layers generally fuse together to form a monolithic component that may have various integral subcomponents. In particular, the manufacturing process may allow an example of the present disclosure to be integrally formed and include various features not possible using previous manufacturing methods.

[0093] The additive manufacturing methods described herein allow for the production of any suitable size and shape with a variety of features that may not have been possible using previous manufacturing methods. Additive manufacturing can create complex shapes without the use of tools, molds, or fixtures of any kind and with little to no waste. Rather than machining a component from a solid billet of plastic or metal, most of which is cut out and discarded, the only material used in additive manufacturing is that needed to mold the part.

[0094] Suitable additive manufacturing techniques according to the present disclosure include, for example, 3D printing by fused deposition modeling (FDM), selective laser sintering (SLS), stereolithography (SLA), etc., direct selective laser sintering (DSLS), electron beam sintering (EBS), electron beam melting (EBM), laser direct deposition modeling (LENS), electron beam additive manufacturing (EBAM), laser net shape manufacturing (LNSM), direct metal deposition (DMD), digital light processing (DLP), continuous digital light processing (CDLP), direct selective laser melting (DSLM), selective laser melting (SLM), direct metal laser melting (DMLM), direct metal laser sintering (DMLS), material jetting (MJ), nanoparticle jetting (NPJ), drop on demand (DOD), binder jetting (BJ), multi-jet fusion (MJF), additive object manufacturing (LOM).

[0095] The additive manufacturing processes described herein can be used to form components using any suitable material.

[0096] As mentioned above, the additive manufacturing processes disclosed herein allow a single component to be formed from multiple materials. For example, a component may include multiple layers, segments, or parts formed using different materials, processes, and / or with different additive manufacturing machines. In this manner, components having different materials and material properties may be constructed to meet the needs of any particular application. Additionally, while the components described herein are constructed exclusively by additive manufacturing processes, it should be appreciated that in alternative embodiments, all or part of these components may be formed by casting, machining, and / or any other suitable manufacturing process. Indeed, any suitable combination of materials and manufacturing methods may be used to form these components.

[0097] Additive manufacturing processes generally create components based on 3D information of the component, such as a three-dimensional computer model (or design file).

[0098] The design file may employ any now known or later developed file format. For example, the design file may be in the Stereolithography or "Standard Tessellation Language" (.stl) format created for 3D Systems' stereolithography CAD programs, or it may be in the Additive Manufacturing File (.amf) format, which is an American Society of Mechanical Engineers (ASME) standard, Extensible Markup Language (XML)-based format designed to allow any CAD software to describe the shape and composition of any three-dimensional object to be created on any additive manufacturing printer.

[0099] Further examples of design files include AutoCAD (.dwg) files, Blender (.blend) files, Parasolid (.x_t) files, Manufacturing Format (.3mf) files, Autodesk (3ds) files, Collada (.dae) files, and Wavefront (.obj) files, although many other file formats exist.

[0100] The design file may be generated using modeling (eg, CAD modeling) software and / or by scanning the surface of the product to measure the product's surface geometry.

[0101] Once obtained, the design file may be converted into a set of computer-executable instructions that, when executed by a processor, cause the processor to control an additive manufacturing device to produce a product according to the geometry specified in the design file. The conversion may convert the design file into slices or layers that are sequentially formed by the additive manufacturing device. The instructions (sometimes known as geometric code or "G-code") may be tailored to a particular additive manufacturing device and may specify the exact location and amount of material to be formed at each stage of the manufacturing process. As explained above, the forming may be by layering, by sintering, or by any other form of additive manufacturing method.

[0102] The code or instructions may be translated between different formats, converted into a set of data signals, transmitted, received as a set of data signals, converted into code, stored as needed, etc. The instructions may be input to the additive manufacturing system and may come from a part designer, intellectual property (IP) provider, design firm, operator, or owner of the additive manufacturing system, or from other sources. The additive manufacturing system may execute the instructions to create a product using any of the techniques or methods disclosed herein.

[0103] The design file or computer executable instructions may be stored in a (transient or non-transient) computer readable storage medium (e.g., memory, storage system, etc.) that stores code or computer readable instructions that represent the product to be produced. As mentioned, the code or computer readable instructions that define the product may be used to physically generate an object when the code or instructions are executed by an additive manufacturing system. For example, the instructions may include a precisely defined 3D model of the product, which may be generated from any of a wide variety of well-known computer-aided design (CAD) software systems, such as AutoCAD®, TurboCAD®, DesignCAD 3D Max, etc. Alternatively, a model or prototype of the component may be scanned to determine the three-dimensional information of the component.

[0104] Thus, by controlling an additive manufacturing device according to computer-executable instructions, the additive manufacturing device can be instructed to print out one or more parts of the rectifier or receiver. These can be printed either in assembled or unassembled form. For example, different parts of the receiver can be printed separately (as a kit of unassembled parts) and then assembled afterwards. Alternatively, the different parts can be printed in assembled form.

[0105] In light of the above, embodiments include a method of manufacturing by additive manufacturing, which includes obtaining a design file representing a rectifier or receiver, and instructing an additive manufacturing device to manufacture the rectifier or receiver in assembled or unassembled form according to the design file. The additive manufacturing device may include a processor configured to automatically convert the design file into computer-executable instructions for controlling the manufacture of the rectifier or receiver. In these embodiments, the design file itself, when input to the additive manufacturing device, may automatically trigger the production of the rectifier or receiver. Thus, in this embodiment, the design file itself may be considered the computer-executable instructions that cause the additive manufacturing device to manufacture the product. Alternatively, the design file may be converted into instructions by an external computing system, and the resulting computer-executable instructions are provided to the additive manufacturing device. The instructions are suitable for execution by the processor and for storage in a non-transitory computer-readable storage medium.

[0106] Although additive manufacturing techniques are described herein as enabling the creation of complex objects by building the object up, generally vertically, point-by-point, layer-by-layer, other methods of creation are possible and are within the scope of this disclosure. For example, while the description herein refers to the addition of material to form successive layers, one skilled in the art will appreciate that the methods and structures disclosed herein may be practiced using additive manufacturing techniques or other manufacturing techniques.

[0107] In another aspect, a computer readable medium is provided that includes instructions that, when executed by a processor, perform any of the described methods. The instructions may operate a controller to perform the described methods. The controller may include a proportional-integral-derivative (PID) controller.

[0108] In another aspect, a computer-readable medium is provided that includes instructions that, when executed by a processor, cause the processor to control an additive manufacturing apparatus to manufacture any of the described rectifiers, receivers, or coils.

[0109] In another aspect, a method of manufacturing a device by additive manufacturing is provided, the method including obtaining an electronic file representing a shape of a product, the product being any of a receiver, rectifier, or coil as described, and controlling an additive manufacturing apparatus to manufacture the product according to the shape specified in the electronic file over one or more additive manufacturing steps.

[0110] This method may provide any of the advantages discussed with respect to the described system, and vice versa.

[0111] The computer-readable medium may be non-transitory. The computer-readable medium may include a storage medium other than a propagating signal. The computer-readable medium may include any suitable memory or storage device, such as a random access memory (RAM), a static RAM (SRAM), a dynamic RAM (DRAM), a non-volatile RAM (NVRAM), a read-only memory (ROM), or a flash memory.

[0112] The processor may comprise a single core processor or a multi-core processor constructed from silicon, polysilicon, high-K dielectrics, copper, and the like.

[0113] In view of the above, the design and manufacture of implementations and operation of the subject matter described in this disclosure may be realized using digital electronic circuitry, or in computer software, firmware, or hardware, including rectifiers and receivers and their structural equivalents, or in a combination of one or more of them. For example, the hardware may include a processor, a microprocessor, an electronic circuit, an electronic component, an integrated circuit, and the like. Implementations of the subject matter described in this disclosure may be realized using one or more computer programs, i.e., one or more modules of computer program instructions, encoded on a computer storage medium for execution by or to control the operation of a data processing device. Alternatively, or in addition, the program instructions may be encoded on an artificially generated propagated signal, e.g., a machine-generated electrical, optical, or electromagnetic signal, that is generated to encode information for transmission to a receiver device suitable for execution by the data processing device. The computer storage medium may be or be included in a computer-readable storage device, a computer-readable storage substrate, a random or serial access memory array or device, or a combination of one or more of them. Additionally, a computer storage medium is not a propagating signal, although a computer storage medium may be a source or destination of computer program instructions encoded in an artificially generated propagating signal. A computer storage medium may also be, or be contained in, one or more separate physical components or media (e.g., multiple CDs, disks, or other storage devices). The media may be a non-transitory computer-readable medium.

[0114] It should be understood that features described with respect to one aspect, example, or embodiment may also be used with respect to other aspects, examples, or embodiments of the disclosure. Other advantages of the present disclosure may become apparent to those skilled in the art from the following detailed description in conjunction with the drawings.

[0115] Embodiments will now be described more fully with reference to the accompanying drawings. [Brief description of the drawings]

[0116] [Figure 1] FIG. 1 is a block diagram of a wireless power transmission system. [Diagram 2] FIG. 1 is a perspective view of a coil for use in a wireless power transfer system. [Diagram 3] FIG. 3 is a perspective view of the coil of FIG. 2 with a shield. [Figure 4] FIG. 3 is a schematic diagram showing tapping of the coil of FIG. 2. [Figure 5a] FIG. 1 is a perspective view of another embodiment of a coil for use in a wireless power transfer system. [Figure 5b] FIG. 5b is a cross-sectional perspective view of a portion of the coil of FIG. 5a. [Figure 6a] FIG. 13 is a plan view of another embodiment of a coil for use in a wireless power transfer system. [Figure 6b] FIG. 6b is a perspective view of the coil of FIG. 6a. [Figure 6c] FIG. 6b is a perspective view of the coil of FIG. 6a with a shield. [Figure 7] FIG. 1 is a schematic diagram of a receiver with a current-driven differential rectifier. [Figure 8] FIG. 8 is a more detailed schematic diagram of the receiver of FIG. [Figure 9] 8 is a graph of normalized voltage versus time in radians across one of the diodes of the rectifier of the receiver of FIG. 7. [Figure 10] 8 is another graph of normalized voltage versus time in radians across one of the diodes of the rectifier of the receiver of FIG. 7. [Figure 11] 8 is another graph of normalized voltage versus time in radians across one of the diodes of the rectifier of the receiver of FIG. 7. [Figure 12] FIG. 13 is a schematic diagram of a receiver with another embodiment of a current-driven differential rectifier. [Figure 13]FIG. 13 is a schematic diagram of a receiver with another embodiment of a current-driven differential rectifier. [Figure 14] FIG. 13 is a schematic diagram of a receiver with another embodiment of a current-driven differential rectifier. [Figure 15] 15 is a graph of normalized voltage versus time in radians across one of the diodes of the rectifier of the receiver of FIG. 14. [Figure 16] FIG. 13 is a schematic diagram of a receiver with another embodiment of a current-driven differential rectifier. [Figure 17] FIG. 13 is a schematic diagram of a receiver with another embodiment of a current-driven differential rectifier. [Figure 18] FIG. 15 is a schematic diagram of a receiver with the current-driven differential rectifier of FIG. 14 connected to a battery. [Figure 19] FIG. 13 is a plan view of another embodiment of a coil for use in a wireless power transfer system. [Figure 20] FIG. 1 is a top perspective view of a receiver for use in a wireless power transfer system. [Figure 21] FIG. 21 is a bottom perspective view of the receiver of FIG. 20. [Figure 22] FIG. 21 is a side view of the receiver of FIG. 20. [Diagram 23] FIG. 21 is a front view of the receiver of FIG. 20. [Figure 24] FIG. 2 is a schematic diagram of a portion of a transmitter with a current-fed inverter. [Diagram 25] FIG. 13 is a schematic diagram of a portion of another embodiment of a transmitter with a current-fed inverter. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0117] The above summary, as well as the following detailed description of some examples, will be better understood when read in conjunction with the accompanying drawings. As used herein, an element or feature introduced in the singular and preceded by the word "a" or "an" should be understood not to necessarily exclude a plurality of elements or features. Furthermore, references to "one example" or "one embodiment" are not intended to be interpreted as excluding the existence of additional examples or embodiments that also incorporate the described element or feature. Furthermore, unless expressly stated otherwise, an example or embodiment that "comprises" or "has" or "includes" an element or feature or elements or features having a particular property may include additional elements or features that do not have that property. It will also be appreciated that the terms "comprise", "have", and "include" mean "including but not limited to", and that "comprising", "having", and "including" have equivalent meanings. It will also be appreciated that like reference numerals will be used throughout the description and drawings to refer to like elements.

[0118] As used herein, the terms "adapted" and "configured" mean that an element, component, or other subject matter is designed and / or intended to perform a given function. Thus, use of the terms "adapted" and "configured" should not be interpreted to mean that a given element, component, or other subject matter is merely "capable" of performing a given function, but rather that the element, component, and / or other subject matter is specifically selected, created, implemented, utilized, and / or designed to perform that function. It is also within the scope of this application that elements, components, and / or subject matter described as adapted to perform a particular function may additionally or alternatively be described as configured to perform that function, and vice versa. Similarly, subject matter described as configured to perform a particular function may additionally or alternatively be described as operable to perform that function.

[0119] When an element is referred to as being "on," "attached," "connected," "coupled," "in contact with," or the like, another element, it will be understood that the element may be directly on, attached, connected, coupled, or in contact with the other element, or intervening elements may be present.

[0120] Use of the word "exemplary" should be understood to mean "as an example" or "one example" rather than to imply a preferred or optimal design or implementation, unless specifically stated otherwise.

[0121] 1, there is shown a wireless power transfer system generally identified by reference numeral 100. The wireless power transfer system 100 includes a transmitter 110 including a power source 112 electrically connected to a transmitting element 116, and a receiver 120 including a receiving element 124 electrically connected to a load 128. Power is transferred from the power source 112 to the transmitting element 116. Power is then transferred from the transmitting element 116 to the receiving element 124 by resonant or non-resonant electric or magnetic field coupling. Power is then transferred from the receiving element 124 to the load 128. An exemplary wireless power transfer system 100 includes a high frequency inductive wireless power transfer system as described in Applicant's U.S. Patent Application Publication No. 2021 / 0083634A1, or a resonant capacitively coupled wireless power transfer system as described in Applicant's U.S. Patent Application Publication No. 9,653,948, the relevant portions of which are incorporated herein by reference.

[0122] In a resonant or non-resonant magnetic (inductive) power transfer system, the transmitting element 116 and the receiving element 124 each comprise a coil. The coils form a magnetically coupled inductor through which the power signal is transmitted / extracted. An exemplary coil is shown in FIG. 2 and is generally identified by reference numeral 200. The coil 200 generally comprises a length of wire arranged in generally concentric rings. In the illustrated arrangement, the coil 200 is a non-planar coil for an inductive (magnetically coupled) wireless power transfer system. The coil 200 is symmetrical along a plane 230.

[0123] In particular, the coil 200 includes at least two turns of wire connected in series. The turns are either inner turns or outer turns. In the illustrated arrangement, the symmetric non-planar coil 200 includes four turns. Two of the turns are outer turns and two are inner turns. The coil 200 has two terminals, namely a first terminal 201 and a second terminal 202. The terminals are located at opposite ends of the wire forming the coil 200.

[0124] As shown in FIG. 3, the coil 200 may be used with a shield 250. The shield 250 may include a passive electrode as described in Applicant's U.S. Pat. No. 11,139,690, the relevant portions of which are incorporated herein by reference. As shown in FIG. 3, the plane formed by the major surfaces of the shield 250 is generally parallel to the plane formed by the major surfaces of the coil 200. In other words, the shield 250 is parallel to the coil 200. The shield 250 is positioned in close proximity to the coil 200. The shield 250 is said to cover the coil 200 to at least partially eliminate the effects of the environment on the coil.

[0125] In this disclosure, shield 250 is said to cover coil 200 when at least one of the following occurs: (i) when the area defined by the perimeter of coil 200 is projected onto the area of ​​shield 250, the projection is entirely within the area of ​​shield 250, (ii) the projected area of ​​coil 200 is surrounded by the area of ​​shield 250, or (iii) the area of ​​shield 250 is greater than the total area defined by the perimeter of coil 200 by at least the inner area defined by the inner turns of coil 200.

[0126] In use, the shield 250 may increase the capacitance of the wireless power transfer system 100. The shield 250 may lower the inductance required to achieve resonance.

[0127] While a particular coil 200 is described, it may be advantageous to provide an alternative coil that is split or tapped. Tapping a coil generally refers to adding an additional terminal to the coil at an end or intermediate the terminals of the coil. The additional terminal forms a third terminal, called a tap. The process of tapping the coil 200 is illustrated in FIG. 4. The coil 200 is tapped to form a coil 300 having terminals 301, 302 at its ends and a third terminal or tap 303 intermediate the first and second terminals 301, 302. The terminals 301, 302, 303 may be connected to components of the receiver 120 as described.

[0128] In the illustrated arrangement, the tap 303 is located approximately at the midpoint of the coil 300, thereby forming a center tap. The process of forming such a tap is called center tapping. The tap 303 evenly divides the coil 300 into two equally balanced sub-coils 310, 320. The sub-coils 310, 320 are electrically coupled to each other at the tap 303 and are electrically balanced.

[0129] The coil 300 is further illustrated in Figures 5a and 5b. In the illustrated arrangement, the coil 300 includes two windings, a first winding including an outer turn and an inner turn, and a second winding including an inner turn and an outer turn.

[0130] A turn is understood to define a circumferential loop or path around an enclosed area or volume.

[0131] In the illustrated arrangement, the first subcoil 310 includes an outer turn of a first winding and an inner turn of a second winding, and the second subcoil 320 includes an inner turn of a first winding and an outer turn of a second winding.

[0132] A first terminal 301 is at the end of the outer turn of the first winding and a second terminal 302 is at the end of the outer turn of the second winding. A tap 303 is between the first terminal 301 and the second terminal 302. Although not shown, during use the tap 303 is electrically connected to ground.

[0133] FIG. 5 b is a cross-sectional perspective view of coil 300 made along line 330 .

[0134] The center tap 303 effectively divides the non-planar coil 300 into sub-coils 310, 320, which are theoretically electrically balanced (equal capacitance).

[0135] The word "center" in center-tapped non-planar coil 300 and the associated figures may indicate that tap 303 physically divides non-planar coil 200 from Figures 2 and 3 into center-tapped non-planar coil 300 including two identical, symmetric coils 310 and 320, although this is not necessarily the case. The third terminal 303 or tap indicates that the two sub-coils 310 and 320 are electrically identical (i.e., have the same inductance, L RXa = L RXb). The two electrically identical sub-coils 310 and 320 of coil 300 may or may not be physically identical and / or symmetrical. It is possible that one sub-coil is not physically identical to the other sub-coil.

[0136] For example, one sub-coil may be larger and / or have more turns than the other sub-coil, or vice versa. The exact location of the third terminal or tap 303 is determined based on the size and shape of the coil 300.

[0137] As identified in the schematic diagram of FIG. 4, the inductance of the coil 200 prior to tapping is L RX and the inductances of the sub-coils 310 and 320 are given as L RXa and L RXb The location of the tap 303 is such that the inductance of each coil 310, 320 is equal, i.e., L RXa =L RXb The coupling coefficient between the coils 310, 320 may be selected as k ab The following equations 1 and 2 are given by L RX , L RXa , and L RXb Explain the relationship between. L RX =L RXa +L RXb +2M ab (Formula 1)

[0138]

number

[0139] However, M ab is the mutual inductance between the sub-coils 310 and 320, and k ab is the coupling coefficient between the sub-coils 310, 320.

[0140] The schematic diagram in Figure 4 shows the coupling coefficient k abis positive.

[0141] Although a particular embodiment of a center-tapped non-planar coil 300 is shown, other configurations are also possible. For example, in another embodiment, the turns of the first subcoil 210 and the second subcoil 220 are in the same plane, referred to as a planar center-tapped coil. Using a planar version of the center-tapped coil 300 has the advantage that it requires less volume, thus allowing the overall size of the associated transmitter or receiver to be reduced.

[0142] 6a and 6b, a planar center-tapped coil 300' is shown. Coil 300' includes all of the elements of coil 300 described above, with the reference numerals followed by "'".

[0143] The planar center-tapped coil 300' includes at least two turns in the same plane and three terminals 301', 302', 303'. The coil 300' includes two windings. In the illustrated arrangement, the coil 300' includes four turns equally spaced with air gaps between the turns, with a first terminal 301' at one end of the coil 300' and a second terminal 302' at the opposite end of the coil 300'. Each winding has two turns. A third terminal or tap 303' is at the tapping point of the inner turn of the coil 300'. Similar to the two-layer non-planar coil 300 previously described, the third terminal or tap 303' electrically divides the coil 300' into two electrically balanced sub-coils 310', 320'.

[0144] Unlike the non-planar coil 300 with subcoils 310, 320, the subcoils 310', 320' of the planar coil 300' are visually indistinguishable due to their planar arrangement. The first subcoil 310' of the planar coil 300' starts from a first terminal 301' and ends at a third terminal or tap 303'. Similarly, the second subcoil 320' of the planar coil 300' starts from a second terminal 302' and ends at a third terminal or tap 303'. As shown in Figures 6a and 6b, the terminals 301', 302', 303' extend in the same direction, which is perpendicular to the plane formed by the turns of the coil 300'.

[0145] In the illustrated arrangement, the first turn 300'a is the outermost turn of the first subcoil 310'. The first turn 300'a is electrically connected to or integral with the second turn 300'b, which is surrounded by the first turn 300'a. In this context, surrounded refers to the first turn 301'a at least partially surrounding the second turn 300'b in the same xy plane.

[0146] The third turn 300'c is the outermost turn of the second sub-coil 320'. The third turn 300'c is electrically connected to or integral with the fourth turn 300'd, and the fourth turn 300'd is surrounded by the third turn 300'c. In this context, surrounded refers to the third turn 300'c at least partially surrounding the fourth turn 300'd in the same xy-plane.

[0147] The first turn 300'a crosses over the third turn 300'c at its midpoint, or vice versa. The second turn 300'b crosses over the fourth turn 300'd at its midpoint, or vice versa. The end of the first turn 300'a / beginning of the second turn 300'b crosses over the end of the third turn 300'c / beginning of the fourth turn 300'd, or vice versa.

[0148] The second and fourth turns 300'b, 300'd are connected at a third terminal or tap 303'.

[0149] 6c, coil 300' is shown with previously described shield 250 adjacent coil 300'. Terminals 301', 302', 303' extend through openings in shield 250 for electrical connection to other components of receiver 120, as will be described.

[0150] As previously described, the first sub-coil 310 and the second sub-coil 320 are electrically coupled to each other and each have a L RXa and L RXb The addition of a third terminal or tap 303 to the coil 300 may compensate for the electrical imbalance caused by the presence of the shield 250.

[0151] The third terminal or tap 303 may not be at the center of the coil 300. The exact location of the third terminal or tap 303 may be determined based on the distance of the shield 250 from the coil 300, and may be determined by the size and shape of the coil 300 and shield 250 structures. This is because the placement of the shield 250 affects the capacitance of the turns of the coil 300 differently depending on the size and proximity of the coil 300 to the shield 250. For example, the outer turn of the first subcoil 310 will be closer to the shield 250 than the outer turn of the second subcoil 320. Similarly, the inner turn of the first subcoil 310 will be closer to the shield 250 than the inner turn of the second subcoil 320. This slight difference in the distance between the subcoils 310, 320 to the shield 250 may cause a slight change in the electrical balance of each of the subcoils 310, 320 in the presence of the shield 250. A symmetric physical division of the non-planar coil 200 can therefore result in a center-tapped coil 300 having two electrically unbalanced sub-coils 310, 320.

[0152] While operating in a vacuum, and in the absence of a shield 250, a physically symmetric split of the non-planar coil 200 would theoretically result in a center-tapped coil 300 consisting of an electrically balanced first sub-coil 310 and a second sub-coil 320. The introduction of a shield 250 or other structure in proximity to the center-tapped coil 300 and its sub-coils 310, 320 can change the electrical balance of the physically symmetric split of the coil 300, resulting in two electrically unbalanced sub-coils 310, 320.

[0153] Although the above description has been presented with respect to coil 300, it is equally applicable to coil 300' shown in Figures 6a to 6c.

[0154] The transmitting element 116 or the receiving element 124 may comprise the coil 300, 300' described. Furthermore, the signal received by the receiving element 124 of the receiver 120 may be a differential AC signal. In many applications, the load 128 of the receiver 120 requires a direct current (DC) signal. A rectifier may be used to rectify the received AC signal to the required DC signal.

[0155] Since the coils 300, 300' are center tapped, a specific rectifier is required to rectify the received / extracted AC power signal. In particular, the coils 300, 300' act like an AC power source and therefore a rectifier compatible with the AC power source is required.

[0156] 7, a portion of a receiver for use in a wireless power transfer system is generally identified by the reference numeral 400. The receiver 400 includes a non-planar center-tapped coil 300 electrically connected to a current-driven differential rectifier 402. The rectifier 402 is electrically connected to a load 404.

[0157] Although the receiver 400 comprises a non-planar center-tapped coil 300, the following description is equally applicable to the planar center-tapped coil 300' described.

[0158] As will be explained, the unique topology of rectifier 402 allows for a significant reduction in the number of diodes required to efficiently operate rectifier 402. For example, compared to traditional full-wave bridge rectifier designs, the number of diodes required is reduced by fifty percent (50%).

[0159] The current-driven differential rectifier 402 comprises first and second capacitors 410, 412, each having a capacitance C1, first and second switching elements including first and second diodes 414, 416 (D1, D2) in the arrangement shown, and first and second inductors 418, 420, each having an inductance L.

[0160] The first capacitor 410 and the first inductor 418 are electrically connected in series. The second capacitor 412 and the second inductor 420 are electrically connected in series. The first diode 414 is electrically connected in parallel between the first capacitor 410 and the first inductor 418. The second diode 416 is electrically connected in parallel between the second capacitor 412 and the second inductor 420. The first capacitor 410 is electrically connected to the first terminal 301 of the coil 300. The second capacitor 412 is electrically connected to the second terminal 302 of the coil 300. The first and second diodes 414, 416 are electrically connected to the third terminal or tap 303 of the coil 300.

[0161] In the illustrated arrangement, the rectifier 402 further includes a capacitor 422 electrically connected in parallel between the first inductor 418 and the load 404. The capacitor 422 is for filtering the power signal output by the rectifier 402. The capacitor 422 is optional.

[0162] The rectifier 402 is current driven, meaning that the AC current supplied by the coil 300 has a constant amplitude that is independent of the load 404. In a conventional wireless power transfer system, the coil of the system's receiver supplies a constant AC voltage. Thus, in contrast to conventional rectifier designs where the rectifier provides a nearly constant DC voltage that is independent of the load, the rectifier 402 provides a nearly constant output DC current that is independent of the load 404.

[0163] In practice, the output DC current may vary slightly based on changes in the load 404 due to non-linear effects, and therefore the values ​​of the electrical components of the rectifier 402 derived by the formula may have to be adjusted based on experimentation.

[0164] 7, the capacitance value C1 of each of the capacitors 410, 412 is determined by the capacitance of the capacitors 410, 412 when the capacitors 410, 412 are connected to the total inductance L of the non-planar receiver coil 300. RX It is tuned to resonate with, but L RX are the inductances L of the sub-coils 310 and 312, respectively. RXa +L RXb The capacitance value C1 is given by Equation 3:

[0165]

number

[0166] In use, wireless power is extracted by the coil 300 and supplied by the rectifier 402. In particular, the coil 300 supplies a constant AC current to the rectifier 402. The AC current is rectified by the rectifier 402 and filtered by the capacitor 422 to provide an approximately constant output DC current to the load 404.

[0167] As previously mentioned, the rectifier 402 is current driven. Figure 8 shows a more detailed schematic of the receiver 400. Figure 8 shows the bond wires of the diodes 414, 416 connected to the L int and the loop inductance is Lloop 8 includes additional inductors 430, 432 that represent the internal inductance of the diodes 414, 416 by having a value of C j 8 further includes capacitors 434, 436 representing the diode internal junction capacitance having a capacitance of C parasitic The capacitance of the capacitor is 0.01V.

[0168] In the current-driven differential rectifier 402, the internal inductors 430, 432 and parasitic capacitors 438, 440 form an impedance network that can therefore result in voltage ringing and oscillations when driven by a constant current (from the coil 300). In particular, the internal inductance of each diode 414, 416, the respective junction capacitances of the diodes (value C j ), and the external parasitic capacitance (value C parasitic Due to the high-side rectification voltage (given by

[0169] Voltage ringing is an undesirable side effect of the rectifier 402 because the ringing and oscillations can cause the voltage to exceed the maximum rated voltage of the diodes 414, 416. Additionally, the ringing and oscillations can also cause a significant increase in electromagnetic interference (EMI). Voltage ringing may be less of an issue with conventional voltage-driven rectifiers because current is a function of voltage, and voltage-driven rectifiers do not pump current into the internal and parasitic networks of the respective diodes.

[0170] To illustrate the voltage ringing and oscillations, as well as other characteristics of the receiver 400, an experimental wireless power transfer system with the described receiver 400 was tested.

[0171] In the experimental setup, the non-planar coil 300 includes four turns: two large outer turns with dimensions of 80×60 mm and two inner turns with dimensions of 68.6 mm×48.6 mm. The distance between each turn is 4 mm in the x and y directions and 3 mm in the z direction. The non-planar coil 300 has a total inductance value L of 861 nH at 6.78 MHz. RX Each of the sub-coils 310 and 320 has an inductance L RXA and L RXB is 298nH at 6.78MHz. The tuning capacitance at 6.78MHz is 2170pF with a tuning capacitor Q of 1000. Therefore, the mutual inductance can be calculated to be 132.5nH at 6.78MHz by the formula previously explained.

[0172] In receiver 400, the receiver coil is center tapped with the tap moved 3 mm to the right to make the two receiver sub-coils electrically balanced (have the same inductance) when shield 250 is present.

[0173] In the experimental setup, the shield 250 was spaced 3 mm from the coil 300 .

[0174] On the transmit side, the transmitter has a similar transmit coil and shield with the same values ​​unless otherwise stated. The inductance of the transmitter coil with shield is 900nH and its tuning capacitance at 6.78MHz is 2170pF with a tuning capacitor Q of 1000. The transmitter resonator Q is 132 and the transmitter self-resonance is 108MHz.

[0175] Using the described experimental setup, the voltage ringing that occurs across the diodes 414, 416 during a transition from an on state to an off state in the current driven rectifier 402 is shown for only one of the diodes 414, 416 in Figure 9. In particular, Figure 9 shows the normalized voltage versus time (in radians) across one of the diodes 414, 416 of the rectifier 402.

[0176] The theoretical voltage waveform across a single diode 414 is shown in solid line, and the actual voltage waveform across diode 414 is shown in dashed line. As shown in Figure 9, the actual voltage waveform exhibits undesirable voltage ringing beyond the value of the theoretical voltage waveform.

[0177] Another effect of the parasitic capacitors 438, 440, the internal and loop inductances (inductors 430, 432), and the nonlinear junction capacitances (capacitors 434, 436) of the diodes 414, 416 is distortion of the voltage waveform across the diodes 414, 416 when they are in the off state. This distortion may include additional second and / or third harmonics. Figures 10 and 11 show two examples of distorted waveforms.

[0178] The nonlinear junction capacitance C of the diodes 414 and 416 j It should be noted that the larger the , the larger the distortion.

[0179] As a result of the described ringing and / or distortion, the rectifier 402 may not be able to generate the required output current. In other words, the output current may be greater or less than what is required by the load 404.

[0180] To minimize distortion and reduce the effect of distortion on the performance of the rectifier, an additional inductor may be included at each of the output terminals (terminals 301, 302) of the coil 300. This embodiment is shown in FIG. 12. In the illustrated arrangement, the receiver 500 comprises the coil 300, a rectifier 502, and a load 404. The rectifier 502 comprises the same elements as the rectifier 402, and like features have reference numbers incremented by 100. The rectifier 502 comprises an additional inductor connected to the terminals 301, 302 of the coil 300. In particular, the rectifier 502 comprises a third inductor 550 electrically connected to the first terminal 301 via the first capacitor 510. The third inductor 550 is electrically connected in series with the first capacitor 510 and electrically connected in series with the first inductor 518. The first diode 514 is electrically connected in parallel with the first and third inductors 518 , 550 .

[0181] The rectifier 502 further includes a fourth inductor 552 electrically connected to the first terminal 302 through the second capacitor 512. The fourth inductor 552 is electrically connected in series with the second capacitor 512 and electrically connected in series with the second inductor 520. The second diode 516 is electrically connected in parallel with the second and fourth inductors 520, 552.

[0182] The third and fourth inductors 550, 552 have an inductance of L1. The third and fourth inductors 550, 552 are coupled to the nonlinear junction capacitance of the diodes 514, 516, i.e., C j The inductance L1 of these two additional inductors 550, 552 introduces an inductive impedance that negates a portion of the capacitive impedance of the diodes 514, 516. j In this embodiment, the inductance L1 of the inductors 550, 552 can be up to 100 nH.

[0183] The third and fourth inductors 550, 552 may introduce power losses and result in a reduced efficiency of the differential rectifier 502. Therefore, the inductors 550, 552 may be removed and a single additional inductor may be electrically connected to the third terminal or tap of the coil. Such an arrangement is shown in FIG. 13. In the illustrated arrangement, the receiver 600 comprises the coil 300, a rectifier 602, and a load 404. The rectifier 602 comprises the same elements as the rectifier 402, and similar features have reference numbers incremented by 200. The rectifier 602 comprises an additional inductor connected to the terminal or tap 303 of the coil 300. In particular, the rectifier 602 comprises a third inductor 654 electrically connected to the third terminal or tap 303. The third inductor 654 is electrically connected to the first and second diodes 614, 616.

[0184] Although the third inductor 654 may still introduce power loss into the differential rectifier 602 , that power loss will be smaller compared to the power loss introduced into the differential rectifier 502 by the third and fourth inductors 550 , 552 .

[0185] The third inductor 654 is connected to the junction capacitance C j In this embodiment, the inductance L1 of the inductor 654 can be up to 100 nH.

[0186] To further minimize the described voltage ringing, the current-driven differential rectifier may further include a capacitor electrically connected in parallel with one of the first and second switching elements. The capacitor may damp or reduce the voltage ringing at the rectifier. The voltage ringing may adversely affect the power transfer because the load does not receive a stable power signal. Thus, reducing or damping the voltage ringing may improve the power signal stability received at the load.

[0187] Additional capacitors are shown in Figure 14, illustrating another arrangement of a receiver generally identified by reference numeral 700. Rectifier 702 includes the same elements as rectifier 402, unless otherwise noted, with like features having reference numerals incremented by 300. In the arrangement shown, rectifier 702 includes a third capacitor 756 electrically connected in parallel with first diode 714 and a fourth capacitor 758 electrically connected in parallel with second diode 716. The third and fourth capacitors 756, 758 have a capacitance C2.

[0188] The capacitance C2 of the capacitors 756, 758 depends on the operating frequency and the operating voltage and current. In contrast to the class E rectifier, there is no specific formula readily available for determining the capacitance C2. However, as a general rule, and based on simulations and experimental tests, it can be assumed that the capacitance C2 is given by Equation 4 below:

[0189]

number

[0190] The added third and fourth capacitors 756, 758 damp the ringing across the diodes 714, 716 so that the diodes 714, 716 conduct most of the current during the transition from the on state to the off state. int.+loop , C j and C parasitic The internal and parasitic inductors and capacitors, having values ​​of .gtoreq..times ...

[0191] The reduction in voltage ringing that occurs across the diodes 714, 716 during the transition from an ON state to an OFF state in the current driven rectifier 702 using the experimental setup previously described is shown in FIG. 15 for only one of the diodes 714, 716. In particular, FIG. 15 shows the normalized voltage versus time (in radians) across one of the diodes 714, 716 of the rectifier 702. As shown in FIG. 15, the theoretical voltage waveform matches the actual voltage waveform across the diode 714. No voltage ringing is observed. The resulting waveform is very similar to that seen in a class E rectifier.

[0192] The described current-driven differential rectifier is a passive rectifier, i.e., the rectifier is a diode-only rectifier. Passive rectifiers operated at low output voltages or high output currents may be less efficient due to power losses associated with the diode forward voltage drops. This may limit the use of such passive rectifiers in applications requiring fast charging rates.

[0193] The rectifier may be operated as a synchronous rectifier by replacing the diode with a FET. Such a synchronous rectifier may have higher efficiency than the described passive rectifier, especially at low output voltages or high output currents. The synchronous rectifier may also have better performance over the entire load range, since the duty cycle of the FET can always be controlled and maintained at 50%. This is not the case with passive rectifiers, where the duty cycle of the diode is affected by the load and thus may result in detuning of the entire wireless power transfer system, i.e., the transmitter and receiver.

[0194] 16, there is shown another arrangement of a receiver generally identified by reference numeral 800. The receiver 800 comprises an inductor 300, a rectifier 802, and a load 404. The rectifier 802 comprises the same elements as the rectifier 702, and like features have reference numerals incremented by 100 unless otherwise noted. In the arrangement shown, the rectifier 802 further comprises first and second FETs 860, 862. The first FET 860 is electrically connected to the first terminal 301 of the inductor 300 via a first capacitor 810 and a third terminal or tap 303. The second FET 862 is electrically connected to the second terminal 302 of the inductor 300 via a second capacitor 812 and a third terminal or tap 303. A first diode 814 is electrically connected in parallel with the first FET 860 and the third capacitor 856. The second diode 816 is electrically connected in parallel with the second FET 862 and the fourth capacitor 858 .

[0195] The rectifier 802 further includes a first delay line 864a, a first signal generator 864b, a second delay line 866a, and a second signal generator 866b. The first delay line 864a is electrically connected to the first terminal 301 of the coil 300 and the first signal generator 864b. The first signal generator 864b is electrically connected to the first delay line 864a and the first FET 860. The first delay line 864a is for synchronizing the operation of the first FET 860. The first signal generator 864b is for generating a pulse signal for driving the first FET 860.

[0196] The second delay line 866a is electrically connected to the second terminal 302 of the coil 300 and the second signal generator 866b. The second signal generator 866b is electrically connected to the second delay line 866a and the second FET 862. The second delay line 866a is for synchronizing the operation of the second FET 862. The second signal generator 866b is for generating a pulse signal for driving the second FET 862.

[0197] The switching signals for the FETs 860, 862 are self-generated. The voltage across each of the center-tapped sub-coils 310, 320 is sensed and connected to respective first and second delay lines 864a, 866a, which are then connected to respective first and second signal generators 864b, 866b, which generate pulsed square waves to drive the respective first and second FETs 860, 862. Each delay line 864a, 866a is designed such that each signal generator 864b, 866b is triggered in time, and the FETs 860, 862 are switched on when the drain voltage across the FETs 860, 862 reaches zero. Further details of synchronous rectification may be found in Applicant's own U.S. Patent Application Serial No. 17 / 472,002, the relevant portions of which are incorporated herein by reference.

[0198] 17, another arrangement of the synchronous rectifier is shown. In this arrangement, the rectifier 802 further comprises an additional inductor electrically connected to the third terminal or tap 303 of the coil to reduce distortion as previously described. In particular, in the arrangement shown, the rectifier 802 further comprises a third inductor 868 electrically connected to the tap 303 and the FETs 860, 862. The third inductor 868 has an inductance L1. The third inductor 868 is for reducing distortion of the voltage to the FETs 860, 862 due to the nonlinear output capacitance of the FETs 860, 862.

[0199] As mentioned before, the current-driven rectifier described above outputs a constant DC signal. The rectifier is therefore suitable for charging a cell or battery without the need for an intermediate DC / DC converter. An example of such an arrangement is shown in FIG. 18. In this arrangement, a receiver 700' comprises a coil 300, a rectifier 702 (described with reference to FIG. 14) and a battery 880. The battery 880 is directly electrically connected to the output of the rectifier 702. That is, the battery is directly connected to the rectifier 702 without a DC / DC converter.

[0200] Although particular coils 300, 300' have been described, those skilled in the art will appreciate that variations are possible, in particular, alternative coils may be used to address one or more of the issues discussed with respect to the described inverter.

[0201] For example, Figure 10 shows a distorted waveform. Such distortion can be caused by parasitic capacitors 438, 440, internal and loop inductances (inductors 430, 432), and nonlinear junction capacitances (capacitors 434, 436) of diodes 414, 416, which can distort the voltage waveform across them when they are in the off state. This distortion can include additional second and / or third harmonics.

[0202] The distortion shown in the actual normalized voltage waveform of FIG. 10 may be referred to as a "double hump" in contrast to the desired theoretical "single hump" waveform. To address this distortion, additional inductors may be added, as described and illustrated in FIGS. 12 and 13. For example, additional inductors 550, 552 (FIG. 12) may be added to the output of the first and second terminals 301, 302 of the coil 300, or an additional inductor 654 (FIG. 13) may be added to the output of the third terminal or tap 303 of the coil 300. Such additional inductors may have the effect of canceling a portion of the capacitive mutual reactance such that second harmonic distortion in the diode is reduced. This may eliminate the "double hump" distortion shown in FIG. 10.

[0203] However, such additional inductors may increase the size of the described differential rectifier, which may be problematic in space-constrained applications, such as mobile devices, and therefore alternative solutions may be desirable for certain applications.

[0204] 19, another embodiment of a coil 2300 is shown. Similar to coil 300, coil 2300 has a first terminal 2301 and a second terminal 2302. Coil 2300 also has a third terminal or tap 2303 intermediate the first terminal 2301 and the second terminal 2302. Coil 2300 includes two windings. In the illustrated arrangement, coil 300' includes four turns equally spaced with gaps between the turns, with the first terminal 2301 at one end of coil 2300 and the second terminal 2302 at the opposite end of coil 2300. Each winding has two turns.

[0205] A first terminal 2301 is at the end of an outer turn of the first winding and a second terminal 2302 is at the end of an outer turn of the second winding. A tap 2303 is between the first terminal 2301 and the second terminal 2302. Although not shown, during use the tap 2303 is electrically connected to ground.

[0206] The tap 2303 evenly divides the coil 2300 into two equally balanced sub-coils 2310, 2320. The sub-coils 2310, 2320 are electrically coupled to each other and are electrically balanced at the tap 2303. As shown in Figure 19, the tap 2303 divides the coil 2300 along a line 2330. The line 2330 defines the central axis of the coil 2300 about which the windings are mirrored.

[0207] In the illustrated arrangement, the first turn 2300a is the outermost turn of the first subcoil 2310. The first turn 2300a is electrically connected to or integral with the second turn 2300b, and the second turn 2300b is surrounded by the first turn 2300a. In this context, surrounded refers to the first 2300a at least partially surrounding the second turn 2300b in the same xy plane.

[0208] The third turn 2300c is the outermost turn of the second sub-coil 2320. The third turn 2300c is electrically connected to or integral with the fourth turn 2300d, which is surrounded by the third turn 2300c. In this context, surrounded refers to the third turn 2300c at least partially surrounding the fourth turn 2300d in the same xy plane. The second and fourth turns 2300b, 2300d are connected at a third terminal or tap 2303.

[0209] The first turn 2300a crosses over or under the third turn 2300c and the fourth turn 2300d at its midpoint. The second turn 2300b crosses over or under the third turn 2300c and the fourth turn 2300d at its midpoint. The third turn 2300c crosses over or under the first turn 2300a and the second turn 2300b at its midpoint. The fourth turn 2300d crosses over or under the first turn 2300a and the second turn 2300b at its midpoint. The second and third turns 2300b, 2300c cross over or under each other at their end points, or the first or fourth turns 2300a, 2300b cross over or under each other at their end points.

[0210] Although traversing above or below a turn is described and shown in FIG. 19, the turns generally lie in the same xy plane.

[0211] The illustrated coil 2300 exhibits reduced mutual coupling k compared to the previously described coils 300, 300'. However, the described and illustrated winding pattern minimizes the turn overlap between the sub-coils 2310, 2320, thereby minimizing the mutual inductance. The reduced mutual inductance results in the reduction or elimination of the previously described voltage waveform distortion. Thus, the coil 2300 does not require an additional inductor when in the described current-drive operated rectifier. The coil 2300 may be more suitable for space-constrained applications.

[0212] To demonstrate this reduction, experimental setups were tested for coil 300, and coil 2300, previously described. Table 1 below contains example values ​​for coil 300, 2300 components of the experimental setup.

[0213] [Table 1]

[0214] The subject coil 2300 has a significantly lower mutual inductance and coupling coefficient than the coil 300 .

[0215] An experimental setup of coils 300, 2300 was constructed and tested with the transmit coil aligned. For testing, the transmit coil was tuned resonant and disconnected from the double impedance transformer. A load impedance of 12 Ω was used to determine X21. The results of the testing are listed in Table 2 below.

[0216] [Table 2]

[0217] Values ​​were determined using a Vector Network Analyzer (VNA). Note that the values ​​shown in Table 2 include losses from the connectors at both the transmitter and receiver. Also note that X21 is lower for Coil 2300, but the power transfer efficiency is about the same.

[0218] Further testing of inductor 2300 showed stable operation at no load and a rectifier voltage of 10V, with reduced voltage distortion at full load and with similar resonance and zero voltage switching (ZVS) capabilities at rectifier voltages up to 21V.

[0219] 20 to 23 are various views of an experimental receiver 2700 described herein used for testing purposes. The receiver 2700 comprises the same elements as the receiver 700 described previously, with similar features having reference numbers incremented by 2000. The components of the rectifier 2702, namely inductors, capacitors, and diodes, are mounted on a PCB 2701. The PCB 2701 is made of aluminum. The PCB 2701 acts as a shield, as described with respect to the shields 250 or 250' shown in Figures 3 and 6c, respectively.

[0220] The described receiver extracts power from the transmitter by inductive coupling. The transmitter and receiver thereby form a wireless power transfer system. The wireless power transfer system comprises either a transmitter or a receiver. The wireless power system operates by transferring power from a transmitter that is non-resonant or not self-resonant to a receiver that is resonant at the operating frequency of the transmitter.

[0221] The transmitter is configured to wirelessly transmit power by magnetic inductive coupling. An electric field may also be generated, but little, if any, power is transferred by electric field coupling. As described in applicant's own U.S. Patent Application Publication No. 2021 / 0083634, the relevant portions of which are incorporated herein by reference, the transmitter may wirelessly transmit power by magnetic inductive coupling.

[0222] As described, the described receiver non-planar coil 300 provides a constant AC current, and therefore the corresponding coil and inverter of the transmitter also provides a constant output voltage (constant amplitude and phase) independent of the load.

[0223] In general, the transmitter comprises a power supply, a transmitter DC / DC converter, a DC / AC inverter, and a transmitter coil. The power supply is electrically connected to the transmitter DC / DC converter. The power supply is configured to generate a DC power signal. The power supply is configured to output the DC power signal to the transmitter DC / DC converter. In this embodiment, the DC power signal is 24-48V. The transmitter DC / DC converter is electrically connected to the power supply. The transmitter DC / DC converter is electrically connected to the DC / AC inverter. The transmitter DC / DC converter couples the power supply to the DC / AC inverter. The transmitter DC / DC converter is configured to convert the DC power signal from the power supply to a voltage level for transmission to the DC / AC inverter.

[0224] The DC / AC inverter is electrically connected to the transmitter DC / DC converter. The DC / AC inverter is electrically connected to the transmitter coil. The DC / AC inverter is configured to convert a DC power signal from the transmitter DC / DC converter into a sinusoidal radio frequency (RF) power signal. The sinusoidal RF power signal is output from the DC / AC inverter to the transmitter coil.

[0225] The transmitter operates at a given frequency. In this embodiment, the operating frequency of the transmitter is 13.56 MHz. Furthermore, in this embodiment, the transmitter coil is identical to the described coil of the receiver, for example coil 300 or coil 300'.

[0226] Although the transmitter has been described as including a transmitter DC / DC converter, one skilled in the art will appreciate that other configurations are possible. In another embodiment, the transmitter does not include a transmitter DC / DC converter. In this embodiment, the power source is electrically connected to the DC / AC inverter. The power source is configured to generate a DC power signal that is acceptable to the DC / AC inverter.

[0227] The receiver is configured to extract power from the transmitter by magnetic inductive coupling. Although electric fields may also be generated, little, if any, power is extracted by electric field coupling.

[0228] 24, a schematic diagram of a DC / AC inverter 900 of a wireless power transfer system is shown. The DC / AC inverter 900 forms part of the transmitter of the system for use with a receiver as described. The DC / AC inverter 900 is load independent. The DC / AC inverter 900 has a voltage mode output. The voltage mode output indicates that the DC / AC inverter 900 has a constant voltage output. Thus, the DC / AC inverter 900 and its impedance transformation network provide a constant output voltage (constant amplitude and phase) regardless of the load.

[0229] In the illustrated arrangement, the DC / AC inverter 900 includes a load independent circuit 902 and an impedance inverter circuit 904. The DC / AC inverter 900 is current mode output (constant output current).

[0230] The load independent circuit 902 is configured to convert an input DC signal to an output AC signal. The load independent circuit 902 is a voltage mode output (constant output voltage). The load independent circuit 902 converts a voltage V in The inductors 910, 930 have inductances L1 and L2 and receive an input voltage having a capacitance of 1. Each inductor 910, 930 is connected in series with a combination of a transistor 912, 932 (Q1 and Q2) and a capacitor 914, 934, respectively. The capacitors 914, 934 have capacitances C1 and C2, respectively. In particular, the transistor 912 and the capacitor 914 are arranged in parallel and connected to the inductor 910. The transistor 932 and the capacitor 934 are arranged in parallel and connected to the inductor 930. Both pairs of transistors 912, 932 and capacitors 914, 934 are grounded. The inductances LZVS An inductor 940 having a capacitance C1 is connected in parallel between the inductors 910 and 912.

[0231] The impedance inverter circuit 904 is configured to convert the load independent circuit 902 from a voltage mode output (constant output voltage) to a current mode output (constant output voltage) and then back to voltage mode (constant output voltage), i.e., the impedance inverter circuit 904 is a double impedance network.

[0232] The impedance inverter circuit 904 has a T-network circuit configuration. The impedance inverter circuit 904 has an inductance L 3a , L 3b , L 4a , L 4b , L 5a , L 5b , and L Tx and inductors 950, 952, 980, 982, 984, 986, and 976 having capacitances C 3a , C 3b , C 3a , and C 3b Capacitors 954, 956, 958, 960 having capacitances C4 and C5, respectively, and resistor R L and a resistor 980 having a

[0233] To simplify the derivation of the formulas and the evaluation of the component values, the inductances L3 and L4 are 3a and inductance L 3b (L3= L 3a + L 3b ) The inductance L4 is introduced as 4a and inductance L 4b (L4 = L 4a + L 4b ).

[0234] Capacitances C3 and C6 are also different. Capacitance C3 is the capacitance C3a and capacitance C 3b (C3= (C 3a + C 3b ) / 2). The capacitance C6 is introduced as 6a and capacitance C 6b (C6= (C 6a + C 6b ) / 2).

[0235] Each inductor 950, 952 is connected in series with a capacitor 954, 956, respectively. The inductor / capacitor pairs 950, 954 and 952, 956 are connected across an inductor 940 of the load independent circuit 902. A capacitor 970 is connected in parallel with the inductor 940. Inductors 980, 982 are connected across the capacitor 970. A capacitor 988 is connected in parallel with the capacitor 970. Additionally, the inductor 984, the capacitor 958, the inductor 976, the resistor 980, the capacitor 960, and the inductor 986 are connected in series, which together are connected in parallel with the capacitor 988.

[0236] The values ​​of the described components are determined by the following equations: capacitance C1, capacitance C2, and inductance L ZVS The relationship between is given by Equation 5 below:

[0237]

number

[0238] The inductance L3 is given by Equation 6 below.

[0239]

number

[0240] The inductance L4 is given by Equation 7 below.

[0241]

number

[0242] The inductance L5 is given by Equation 8 below.

[0243]

number

[0244] 24 is defined as the ratio of the AC voltage across resistor 980 to the input DC voltage. The voltage gain is given by Equation 9:

[0245]

number

[0246] Although a particular DC / AC inverter 900 has been described, one skilled in the art will appreciate that other configurations are possible. Referring now to Figure 25, there is shown a schematic layout diagram of another embodiment of a DC / AC inverter, generally identified by reference numeral 1700. In this embodiment, the DC / AC inverter 1700 comprises a load independent circuit 1702 and an impedance inverter circuit 1704. The DC / AC inverter 1700 is a voltage mode output (constant output voltage).

[0247] The load independent circuit 1702 is configured to convert an input DC signal to an output AC signal. The load independent circuit 1702 is a voltage mode output (constant output voltage).

[0248] The load independent circuit 1702 is connected to a voltage V inThe inductors 1710, 1730 have inductances L1 and L2 and receive an input voltage having a capacitance of 1714, 1734, respectively. Each inductor 1710, 1730 is connected in series with a combination of a transistor 1712, 1732 (Q1 and Q2) and a capacitor 1714, 1734, respectively. The capacitors 1714, 1734 have capacitances C1 and C2, respectively. In particular, the transistor 1712 and the capacitor 1714 are arranged in parallel and connected to the inductor 1710. The transistor 1732 and the capacitor 1734 are arranged in parallel and connected to the inductor 1730. Both pairs of transistors 1712, 1732 and capacitors 1714, 1734 are grounded. The inductances L ZVS An inductor 1740 having a capacitance C1 is connected in parallel between the inductors 1710 and 1712.

[0249] The impedance inverter circuit 1704 is configured to convert the load independent circuit 1702 from a voltage mode output (constant output voltage) to a current mode output (constant output voltage) and back to voltage mode (constant output voltage). In contrast to the impedance inverter circuit 904, the impedance inverter circuit 1704 has a pi network circuit configuration. The impedance inverter circuit 1704 includes an inductance L 3a , L 3b , L 4a , L 4b , L 5a , L 5b , and L Tx Inductors 1750, 1752, 1980, 1982, 1984, 1986, and 1770 each having a capacitance C 4a , C 4b , C 3a , C 3b , C 6a , C 6a , and C5, respectively, and resistors R L and a resistor 1780 having a

[0250] Capacitance C 3aA capacitor 1764 having a capacitance C 3b A capacitor 1766 having a capacitance C5 is connected in parallel to the capacitors 1760, 1762. Capacitor 1766 is also connected in parallel to the inductors 1980 and 1982. A capacitor 1988 having a capacitance C5 is connected in parallel to the inductors 1980 and 1982. Capacitor 1988 is also connected in parallel to the inductors 1984 and 1986. Inductor 1984, capacitor 1958, inductor 1770, resistor 1780, capacitor 1960, and inductor 1986 are connected in series and are connected together in parallel to capacitor 1988.

[0251] To simplify the derivation of the formulas and the evaluation of the component values, the inductances L3 and L4 are 3a and inductance L 3b (L3= L 3a + L 3b ) The inductance L4 is introduced as 4a and inductance L 4b (L4 = L 4a + L 4b ) Inductance L5 is the inductance L 5a and inductance L 5b (L5= L 5a + L 5b ).

[0252] Capacitances C3 and C6 are also different. Capacitance C3 is the capacitance C 3a and capacitance C 3b (C3= (C 3a + C 3b ) / 2). C4 is the capacitance C 4a and capacitance C 4b (C4= (C 4a + C 4b ) / 2). C6 is the capacitance C6a and capacitance C 6b (C6= (C 6a + C 6b ) / 2).

[0253] The values ​​of the described components are determined by the following equations: capacitance C1, capacitance C2, and inductance L ZVS The relationship between is given by Equation 10 below.

[0254]

number

[0255] The inductance L4 is given by Equation 11 below.

[0256]

number

[0257] The inductance L5 is given by Equation 12 below.

[0258]

number

[0259] The voltage gain of inverter 1700 is defined as the ratio of the AC voltage across resistor 1780 to the input DC voltage. The voltage gain is given by Equation 13 below:

[0260]

number

[0261] The DC / AC inverter 1700 allows the voltage at the transmitter coil to be set independent of the input DC voltage and the inductance of the transmitter coil.

[0262] Although particular arrangements have been described with reference to particular figures, one skilled in the art will appreciate that arrangements may be combined. For example, the arrangement shown in Figure 12 with additional third and fourth inductors 550, 552 may be combined with the synchronous rectifier arrangement shown in Figure 15. Other similar combinations of arrangements are within the scope of the present disclosure.

[0263] Although the embodiments have been described with reference to the figures, those skilled in the art will appreciate that variations and modifications can be made without departing from the scope thereof, which is defined by the appended claims. [Explanation of symbols]

[0264] 100 Wireless power transmission system 110 Transmitter 112 Power supply 116 Sending elements 120 Receiver 124 Receiving elements 128 Load 200 Coil 201 First Terminal 202 Second Terminal 230 plane 250 Shield 300 coils 301 First Terminal 302 Second Terminal 303 Third Terminal or Tap 310 First sub-coil 320 Second sub coil 330 lines 400 Receiver 402 Rectifier, Current Driven Differential Rectifier 404 Load 410 First Capacitor 412 Second Capacitor 414 First Diode 416 Second Diode 418 First Inductor 420 Second Inductor 422 Capacitor 430 inductor, internal inductor 432 Inductor, Internal Inductor 434 Capacitor 436 Capacitor 438 Capacitor, Parasitic Capacitor 440 Capacitor, Parasitic Capacitor 500 Receiver 502 Rectifier, differential rectifier 510 First Capacitor 512 Second Capacitor 514 First Diode 516 Second Diode 518 First Inductor 520 Second Inductor 550 3rd inductor 552 4th Inductor 600 Receiver 602 Rectifier, differential rectifier 614 First Diode 616 Second Diode 654 Third Inductor 700 Receiver 702 Rectifier, Current Driven Rectifier 714 First Diode 716 Second Diode 756 Third Capacitor 758 4th Capacitor 800 Receiver 802 rectifier 810 First Capacitor 812 Second Capacitor 814 First Diode 816 Second Diode 856 Third Capacitor 858 4th Capacitor 860 First FET 862 Second FET 864a First Delay Line 864b First signal generator 866a Second Delay Line 866b Second Signal Generator 868 Third Inductor 880 Battery 900 DC / AC Inverter 902 Load independent circuit 904 Impedance Inverter Circuit 910 Inductor 912 Transistor 914 Capacitor 930 Inductor 932 Transistor 934 Capacitor 940 Inductor 950 Inductor 952 Inductor 954 Capacitor 956 Capacitor 958 Capacitor 960 Capacitor 970 Capacitor 976 Inductor 980 Inductors and resistors 982 Inductor 984 Inductor 986 Inductor 988 Capacitor 1700 DC / AC Inverter 1702 Load independent circuit 1704 Impedance Inverter Circuit 1710 Inductor 1712 Transistor 1714 Capacitor 1730 Inductor 1732 Transistor 1734 Capacitor 1740 Inductor 1750 Inductor 1752 Inductor 1760 Capacitor 1762 Capacitor 1764 Capacitor 1766 Capacitor 1770 Inductor 1780 resistor 1958 Capacitor 1960 Capacitor 1980 Inductor 1982 Inductor 1984 Inductor 1986 Inductor 1988 Capacitor 2300 Coil 2301 1st terminal 2302 Second Terminal 2303 Third Terminal or Tap 2310 1st sub coil 2320 Second sub coil 2330 line 2700 Receiver 2701 Printed circuit boards (PCB) 2702 Rectifier

Claims

1. 1. A differential rectifier for use in a receiver for receiving wireless power by inductive coupling, the rectifier comprising first and second capacitors, first and second switching elements, and first and second inductors; the first capacitor and the first inductor are electrically connected in series, and the second capacitor and the second inductor are electrically connected in series; the first switching element is electrically connected in parallel between the first capacitor and a first inductor, and the second switching element is electrically connected in parallel between the second capacitor and a second inductor; the first capacitor is electrically connected to a terminal of the coil for wirelessly receiving power by inductive coupling, and the second capacitor is electrically connected to another terminal of the coil for wirelessly receiving power by inductive coupling; A differential rectifier, wherein the first and second switching elements are electrically connected to taps of a coil for wirelessly receiving power by inductive coupling.

2. 10. The differential rectifier of claim 1, further comprising a capacitor electrically connected in parallel with one of the first and second switching elements.

3. 3. The differential rectifier of claim 2, wherein the capacitors have a capacitance equal to 0.175 divided by the operating frequency multiplied by the output load.

4. 4. The differential rectifier of claim 1, wherein the differential rectifier is a passive rectifier.

5. A differential rectifier as claimed in any preceding claim, wherein the differential rectifier is current driven.

6. 6. A differential rectifier as claimed in any one of claims 1 to 5, wherein the differential rectifier is configured to provide a constant DC current independent of the load.

7. 1. A receiver for use in a wireless power transfer system, the receiver being for receiving power by inductive coupling; A differential rectifier according to any one of claims 1 to 6; A coil for extracting power by inductive coupling from the generated field; A receiver comprising:

8. the coil comprises at least two windings; an outer turn of the first winding and an inner turn of the second winding form a first sub-coil of the coil; an inner turn of the first winding and an outer turn of the second winding form a second sub-coil of the coil.

8. The receiver of claim 7.

9. a first terminal is formed at an end of the outer or inner turn of the first winding and a second terminal is formed at an end of the outer or inner turn of the second winding; the tap is formed between the first terminal and the second terminal to split the coil into the first sub-coil and the second sub-coil.

9. The receiver of claim 8.

10. The receiver of claim 9 , wherein the first and second switching elements are electrically connected to the tap.

11. 11. The receiver of claim 9 or 10, wherein the first inductor and / or the first capacitor are electrically connected to the first terminal.

12. 12. The receiver of claim 9, wherein the second inductor and / or the second capacitor are electrically connected to the second terminal.

13. the first capacitor and the first inductor are electrically connected in series with the first switching element electrically connected in parallel between the first capacitor and the first inductor; and / or the second capacitor and the second inductor are electrically connected in series with the second switching element electrically connected in parallel between the second capacitor and the second inductor. Receiver according to any one of claims 9 to 12.

14. 14. The receiver of claim 7, further comprising at least one additional inductor electrically connected to one of the terminals or taps of the coil.

15. 15. The receiver of claim 14, further comprising: a third inductor electrically connected to the first terminal; and a fourth inductor electrically connected to the second terminal.

16. The receiver of claim 14 further comprising a third inductor electrically connected to the tap.

17. the rectifier is a synchronous rectifier; a first transistor electrically connected to the tap of the coil and to the first terminal of the coil; a second transistor electrically connected to the tap of the coil and to the second terminal of the coil; 17. The receiver of claim 9, further comprising:

18. a first signal generator electrically connected to the first transistor for generating a pulse signal for driving the first transistor; a second signal generator electrically connected to the second transistor for generating a pulse signal for driving the second transistor; The receiver of claim 17 further comprising:

19. a first delay line electrically connected to the first terminal of the coil for synchronizing operation of the first transistor; and a second delay line electrically connected to the second terminal of the coil for synchronizing operation of the second transistor; and 19. The receiver of claim 17 or 18, further comprising:

20. A load electrically connected to the rectifier.

20. The receiver of claim 7, further comprising:

21. 21. The receiver of claim 20, further comprising a capacitor electrically connected in parallel between the inductor and a load, the capacitor for filtering the power signal output by the rectifier.

22. 1. A coil for use in a wireless power transfer system for transferring power by inductive coupling, the coil comprising at least two windings; an outer turn of the first winding and an inner turn of the second winding form a first sub-coil of the coil; an inner turn of the first winding and an outer turn of the second winding form a second sub-coil of the coil; a first terminal is formed at an end of the outer or inner turn of the first winding and a second terminal is formed at an end of the outer or inner turn of the second winding; A coil, wherein a tap is formed between the first terminal and the second terminal to split the coil into the first sub-coil and the second sub-coil, the tap being electrically connected to ground.

23. The coil of claim 22 , wherein the first and second sub-coils are electrically balanced.

24. 24. A coil as claimed in claim 22 or 23, wherein the capacitance of the first sub-coil is approximately equal to the capacitance of the second sub-coil.

25. 25. A coil as claimed in any one of claims 22 to 24, wherein the outer turn of the first winding at least partially overlaps the outer turn of the second winding.

26. 26. A coil as claimed in any one of claims 22 to 25, wherein the inner turn of the first winding at least partially overlaps the inner turn of the second winding.

27. 26. A coil as claimed in any one of claims 22 to 25, wherein the at least one winding includes one or more further turns between an inner turn and an outer turn.

28. 28. The coil of claim 22, further comprising a shield disposed adjacent the coil to protect the coil from electrical interference.

29. 30. The coil of claim 28, wherein the shield is configured to add capacitance to the coil.

30. A load independent inverter comprising a switch mode zero voltage switching (ZVS) amplifier, A pair of circuits, at least one transistor and at least one capacitor arranged in parallel; at least one inductor arranged in series with the transistor and the capacitor; a pair of circuits comprising: a single ZVS inductor electrically connected to said pair of circuits; an impedance transformation stage electrically connected to the ZVS inductor; at least one capacitor electrically connected to the impedance transformation stage and arranged in series with at least one inductor and at least one resistor; An inverter comprising:

31. 31. The inverter of claim 30, wherein the inverter has a constant current output.

32. 1. A method for rectifying a power signal received at a receiver in a wireless power transfer system, comprising: extracting power from the generated field by inductive coupling at a coil to generate an AC power signal; rectifying the AC power signal with a differential rectifier, the differential rectifier comprising first and second capacitors, first and second switching elements, and first and second inductors; Including, the first capacitor and the first inductor are electrically connected in series, and the second capacitor and the second inductor are electrically connected in series; the first switching element is electrically connected in parallel between the first capacitor and a first inductor, and the second switching element is electrically connected in parallel between the second capacitor and a second inductor; the first capacitor is electrically connected to a terminal of the coil and the second capacitor is electrically connected to another terminal of the coil; The method of claim 1, wherein the first and second switching elements are electrically connected to taps of the coil.

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