Bidirectional power transmission system, method of operating the bidirectional power transmission system, and wireless power system

Abstract

The bidirectional wireless power transfer system for transferring power comprises a power stage electrically connected to a transceiver element for the electric and / or magnetic fields and for extracting power from the generated electric and / or magnetic fields. The power stage is for inverting an input power signal and for rectifying a received power signal. The system further comprises a trigger circuit for synchronizing the wireless power transfer and a clock generator for generating a clock signal. The system further comprises a switching element electrically connected to the power stage and selectively electrically connected to the trigger circuit and the clock generator, such that when the switching element electrically connects the clock generator to the power stage, the transceiver element is configured to transfer power by generating the electric and / or magnetic fields, and when the switching element electrically connects the trigger circuit to the power stage, the transceiver element is configured to extract power from the generated electric and / or magnetic fields.

Description

[Technical Field]

[0001] The present disclosure relates generally to wireless power transfer, and more particularly to a bidirectional wireless power transfer system for transferring power, a method of operating the bidirectional wireless power transfer system, and a wireless power system. [Background technology]

[0002] Wireless power transfer systems, such as wireless chargers, are becoming an increasingly important technology for enabling the next generation of devices. The potential benefits and advantages offered by the technology are evident with a growing number of manufacturers and companies investing in the technology.

[0003] Various wireless power transmission systems are known. A typical wireless power transmission 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, a transmitter has a transmitter coil with a certain inductance that transfers electrical energy from a power source to a receiver having a receiver coil with a certain inductance. Power transfer occurs due to magnetic field coupling between the transmitter and receiver coils or inductors. These magnetic induction systems have limited range, and the transmitter and receiver coils or inductors must be closely coupled, i.e., have a coupling coefficient above 0.5, and be optimally aligned, for efficient power transfer.

[0005] Furthermore, resonant magnetic systems exist in which power is transferred due to magnetic field coupling between the coils or inductors of the transmitter and receiver. The transmitter and receiver inductors are loosely coupled, i.e., may 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 issues are corrected. While electromagnetic energy is generated in magnetic induction and resonant magnetic systems, the majority of power transfer occurs via magnetic fields. Little, if any, power is transferred via electric induction or resonant electric induction.

[0006] In an electrical induction system, the transmitter and receiver have capacitive electrodes. Power transfer occurs due to the coupling of electric fields between the capacitive electrodes of the transmitter and receiver. Similar to resonant magnetic systems, resonant electrical systems exist in which the capacitive electrodes of the transmitter and receiver are made resonant using at least one inductor. The inductor can be a coil. In a resonant electrical system, the transmitter is self-resonant and the receiver is self-resonant. Resonant electrical systems have an increased range of power transfer compared to the range of power transfer in electrical induction systems, and alignment issues are corrected. While electromagnetic energy is generated in electrical induction and resonant electrical systems, the majority of power transfer occurs via electric fields. Little, if any, power is transferred via magnetic induction or resonant magnetic induction.

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

[0008] This background is merely intended to set the stage so that those skilled in the art can better grasp the summary and detailed description that follow. Therefore, none of the above discussion should necessarily be taken as an admission that the discussion is part of the state of the art or is common general knowledge. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] U.S. Provisional Application No. 62 / 899,165 [Patent Document 2] U.S. Patent No. 9,653,948 [Patent Document 3] U.S. Patent No. 9,979,206 [Patent Document 4] U.S. Patent Application No. 17 / 193,539 [Patent Document 5] U.S. Patent No. 10,424,942 [Patent Document 6] U.S. Patent No. 10,033,225 [Patent Document 7] U.S. Patent Application Publication No. 2021 / 0021160 [Patent Document 8] U.S. Patent Application Publication No. 2020 / 0227941 [Patent Document 9] U.S. Patent Application Publication No. 2020 / 0203997 [Patent Document 10] U.S. Patent Application Publication No. 2020 / 0203998 [Patent Document 11] U.S. Patent Application Publication No. 2020 / 0099254 Summary of the Invention

[0010] Accordingly, in one aspect, a bidirectional wireless power transfer system for transferring power is provided.

[0011] The system may allow for wireless power transfer in a forward power flow direction and in an opposite reverse power flow direction, which is opposite to the forward power flow direction.

[0012] The system may include a power stage electrically connected to a transceiver element for transferring power by generating an electric field and / or a magnetic field and for extracting power from the generated electric field and / or the generated magnetic field, the power stage for inverting an incoming power signal and rectifying a received power signal; a trigger circuit for synchronizing the wireless power transfer; a clock generator for generating a clock signal; and a switching element electrically connected to the power stage and selectively electrically connected to the trigger circuit and the clock generator, such that when the switching element electrically connects the clock generator to the power stage, the transceiver element is configured to transfer power by generating an electric field and / or a magnetic field, and when the switching element electrically connects the trigger circuit to the power stage, the transceiver element is configured to extract power from the generated electric field and / or the generated magnetic field.

[0013] Operation of the switching elements allows controlled operation of the bidirectional system, such that the transceiver elements can extract power to receive power or generate fields to transmit power.

[0014] The switching elements may be operated manually or autonomously, may be operated remotely, or may be operated by a controller.

[0015] The bidirectional power transfer system forms a transmitter for transferring power by generating a magnetic and / or electric field when the clock generator is electrically connected to the power stage via the switching element, and forms a receiver for extracting power from the generated magnetic and / or electric field when the trigger circuit is electrically connected to the power stage via the switching element.

[0016] The system may include a transceiver element.

[0017] The clock generator may generate a clock signal to control the power stage. The clock generator may comprise an oscillator.

[0018] The power stage may comprise an amplifier, which may be a class E power amplifier.

[0019] The power stage may comprise an input stage for at least one of optimizing load performance, regulating current or load, and reducing harmonics.

[0020] The input stage may include a matching network.

[0021] The matching network may comprise a single impedance inverter or a dual impedance inverter.

[0022] The power stage may include a gate driver for controlling the power stage. The amplifier may include a gate driver electrically connected to a main switch of the amplifier. Control of the gate driver by the oscillator may be used to control operation of the main switch of the amplifier to invert an incoming power signal. Control of the gate driver by the trigger circuit may be used to control operation of the main switch of the amplifier to extract the received power signal.

[0023] The trigger circuit may be for controlling operation of the power stage to synchronize the power signal received by the transceiver element.

[0024] The trigger circuit may comprise a sampling circuit for sampling the current or the voltage.

[0025] The sampling circuit may be configured to sample the voltage drop.

[0026] The sampling circuit may be configured to sample a current or to sample a voltage.

[0027] The sampled current may be load independent, which may be defined as the current being constant with respect to load variations.

[0028] The sampled voltage may be load independent, which may be defined as the voltage being constant with respect to load variations.

[0029] The system may further include a converter for converting the voltage of the power signal. The converter may be a DC / DC (direct current to direct current) converter. The converter may be a buck-boost converter. The converter may be a bidirectional buck-boost converter.

[0030] The transceiver element may transfer power from a power source. The transceiver element may transfer power from the power source to another transceiver element in a forward power flow direction. When operating to transfer power to another transceiver element, the power stage is electrically connected to the clock generator via the switching element.

[0031] The transceiver element may transmit power to a load. The transceiver element may extract power from another transceiver element in a reverse power flow direction. The extracted power may be transmitted to the load. When operating to extract power from another transceiver element, the power stage is electrically connected to the trigger circuit via the switching element.

[0032] The transceiver element may comprise at least one capacitive or inductive element.

[0033] The capacitive element may comprise an electrode.

[0034] The inductive element may comprise an inductive coil.

[0035] According to another aspect, a first transceiver or transmitter for wirelessly transmitting power by magnetic and / or electric field coupling includes a first transceiver element for transmitting power by generating an electric and / or magnetic field and for extracting power from the generated electric and / or magnetic field; a first power stage electrically connected to the first transceiver element for inverting an input power signal in a forward power flow and for rectifying a received power signal in a reverse power flow; and a first power stage electrically connected to the first transceiver element for inverting an input power signal in a forward power flow and for rectifying a received power signal in a reverse power flow. a first trigger circuit for synchronizing power transfer, a first clock generator for generating a clock signal, and a first switching element electrically connected to the first power stage; and a first switching element selectively electrically connected to the first trigger circuit and the first clock generator, such that when the first switching element electrically connects the first clock generator to the first power stage, the first transceiver element is configured to transfer power by generating an electric field and / or a magnetic field; and the first switching element electrically connects the first trigger circuit to the first power stage. a first switching element configured to extract power from the generated electric field and / or the generated magnetic field when the first transceiver element is coupled to the first power stage; a second transceiver or receiver for wirelessly extracting power by magnetic field or electric field coupling, the second transceiver element for transmitting power by generating the electric field and / or the magnetic field and for extracting power from the generated electric field and / or the generated magnetic field; and a second power stage electrically connected to the second transceiver element, the second power stage being configured to transmit power in a countercurrent power flow direction. a second power stage for inverting an incoming power signal in the forward power flow direction and for rectifying a received power signal in the forward power flow direction; a second trigger circuit for synchronizing wireless power transmission; a second clock generator for generating a clock signal; and a second switching element electrically connected to the second power stage and selectively electrically connected to the second trigger circuit and the second clock generator, such that when the second switching element electrically connects the second clock generator to the second power stage, the second transceiver element:and a second switching element configured to transfer power to the transmitter or first transceiver by generating an electric field and / or a magnetic field, wherein the second transceiver element is configured to extract power from the generated electric field and / or the generated magnetic field from the transmitter or first transceiver when the switching element electrically connects a second trigger circuit to a second power stage.

[0036] The first transceiver or transmitter may be for wirelessly transmitting power in a forward power flow mode or for wirelessly extracting power by magnetic and / or electric field coupling in a reverse power flow mode.

[0037] The second transceiver or receiver may be for wirelessly extracting power in a forward power flow mode or for wirelessly transmitting power by magnetic or electric field coupling in a reverse power flow mode.

[0038] When the system is operating in a forward power flow direction, the first transceiver transmits power to the second transceiver, and when operating in the forward power flow direction, the first switching element connects the first clock generator to the first power stage and the second switching element connects the second trigger circuit to the second power stage.

[0039] When the system is operating in the reverse power flow direction, the second transceiver transfers power to the first transceiver, and when operating in the reverse power flow direction, the first switching element connects the first trigger circuit to the first power stage and the second switching element connects the second clock generator to the second power stage.

[0040] Operating the respective switching elements may cause the system to switch between operating in a forward power flow direction and operating in a reverse power flow direction.

[0041] The transmitter may further comprise a load and / or a power supply. The power supply may be a direct current (DC) power supply. The load may be a DC load.

[0042] The power supply may provide an input power signal for wireless power transfer.

[0043] The load may be powered by a power signal extracted by wireless power transmission.

[0044] The receiver may further comprise a load and / or a power supply. The power supply may be a DC power supply. The load may be a DC load.

[0045] The power supply may provide an input power signal for wireless power transfer.

[0046] The load may be powered by a power signal extracted by wireless power transmission.

[0047] The system may include any of the features and / or elements described with respect to the bidirectional wireless power transfer system.

[0048] According to another aspect, there is provided a method of operating a bidirectional wireless power transfer system comprising: a transceiver element for transferring power by generating an electric field and / or a magnetic field and for extracting power from the generated electric field and / or the generated magnetic field; a power stage electrically connected to the transceiver element, the power stage for inverting an input power signal and for rectifying a received power signal; a trigger circuit for synchronizing the wireless power transfer; a clock generator for generating a clock signal; and a switching element electrically connected to the power stage and selectively electrically connected to the trigger circuit and the clock generator, whereby when the switching element electrically connects the clock generator to the power stage, the transceiver element is configured to transfer power by generating the electric field and / or the magnetic field, and when the switching element electrically connects the trigger circuit to the power stage, the transceiver element is configured to extract power from the generated electric field and / or the generated magnetic field, the method including the step of connecting the power stage to the trigger circuit for extracting power or connecting the power stage to the clock generator for transferring power.

[0049] Contrary may be defined as operation in the opposite direction with respect to wireless power transmission, e.g., a transmitter may transmit power to a receiver, and in the opposite direction, a receiver may transmit power to a transmitter.

[0050] The step of connecting the power stage to the trigger circuit or the clock generator may include operating a switching element.

[0051] The method may further include the step of decoupling the power stage from the clock generator or decoupling the power stage from the trigger circuit.

[0052] Decoupling the power stage from the trigger circuit or the clock generator may include operating a switching element.

[0053] The step of connecting the power stage to a trigger circuit to extract power or to a clock generator to transmit power may be automated. This automated connection may be controlled by a controller. The controller may operate to connect elements in response to detected signals such as impedance, resistance, pressure, temperature, etc.

[0054] The method may provide any of the advantages discussed with respect to the described system, and vice versa.

[0055] In another aspect, a computer-readable medium is provided that includes instructions that, when executed by a processor, perform any of the described methods.

[0056] The computer-readable medium may be non-transitory. The computer-readable medium may include storage media other than propagating signals. The computer-readable medium may include any suitable memory or storage device, such as random-access memory (RAM), static RAM (SRAM), dynamic RAM (DRAM), non-volatile RAM (NVRAM), read-only memory (ROM), or flash memory.

[0057] The processor may have a single core processor or multiple core processors composed of various materials such as silicon, polysilicon, high-k dielectrics, copper, and the like.

[0058] It should be understood that any feature described in connection with one aspect, example, or embodiment can also be used in connection with any other aspect, example, or embodiment of the present disclosure. Other advantages of the present disclosure may become apparent to those skilled in the art from the detailed description taken in conjunction with the drawings that follow.

[0059] The embodiments will now be more fully described with reference to the accompanying drawings. [Brief explanation of the drawings]

[0060] [Figure 1] FIG. 1 is a block diagram of a wireless power transmission system. [Figure 2] FIG. 1 is a block diagram of a bidirectional wireless power transfer system according to aspects of the present disclosure. [Figure 3A] FIG. 1 is a block diagram of a wireless power transfer system operating in a forward power flow direction in accordance with aspects of the present disclosure. [Figure 3B] FIG. 3B is a block diagram of the wireless power transfer system of FIG. 3A operating in a reverse power flow direction. [Figure 4] FIG. 1 is a block diagram of a wireless power transfer system according to aspects of the present disclosure. [Figure 5] FIG. 5 is a block diagram of a portion of the wireless power transfer system of FIG. 4. [Figure 6A] FIG. 5 is an equivalent circuit diagram of a portion of the wireless power transmission system of FIG. [Figure 6B] 5 is another equivalent circuit diagram of a portion of the wireless power transfer system of FIG. 4. [Figure 7] FIG. 5 is a block diagram of a portion of the wireless power transfer system of FIG. 4. [Figure 8] Figure 7 is a circuit diagram of the dual impedance inverter of the wireless power transfer system. [Figure 9] FIG. 8 is a circuit diagram of an amplifier of the wireless power transfer system of FIG. 7. [Figure 10] FIG. 8 is a block diagram of the trigger circuit, switching element, auxiliary DC / DC converter, and amplifier of the wireless power transfer system of FIG. [Figure 11] FIG. 11 is a circuit diagram of a sampling circuit of the trigger circuit of FIG. 10. [Figure 12] FIG. 11 is a circuit diagram of a portion of the trigger circuit of FIG. 10. [Figure 13]FIG. 11 is a circuit diagram of a portion of the trigger circuit, switching element, and auxiliary DC / DC converter of FIG. 10. [Figure 14] FIG. 5 is a block diagram of a portion of the wireless power transfer system of FIG. 4. [Figure 15A] FIG. 15 is an equivalent circuit diagram of a portion of the wireless power transmission system of FIG. [Figure 15B] FIG. 15 is another equivalent circuit diagram of a portion of the wireless power transfer system of FIG. [Figure 16] FIG. 5 is a block diagram of a portion of the wireless power transfer system of FIG. 4. [Figure 17] FIG. 17 is a circuit diagram of a single impedance inverter of the wireless power transfer system of FIG. 16. [Figure 18] FIG. 17 is a circuit diagram of an amplifier in the wireless power transfer system of FIG. [Figure 19] FIG. 17 is a block diagram of the transceiver elements, impedance inverter, trigger circuit, switching elements, auxiliary DC / DC converter, and amplifier of the wireless power transfer system of FIG. [Figure 20] FIG. 20 is a circuit diagram of a portion of the transceiver elements, amplifier, impedance inverter, and trigger circuit of FIG. 19. [Figure 21] FIG. 20 is a circuit diagram of a portion of the trigger circuit of FIG. 19. [Figure 22] FIG. 20 is a circuit diagram of a portion of the trigger circuit, switching element, and auxiliary DC / DC converter of FIG. 19. [Figure 23A] FIG. 1 is a plan view of a portion of a bidirectional wireless power transfer system according to aspects of the present disclosure. [Figure 23B] FIG. 10 is a plan view of a portion of another bidirectional wireless power transfer system according to aspects of the present disclosure. [Figure 24A] 1 is a graph of input power and output power with respect to load current for a wireless power transfer system operating in a forward power flow direction in accordance with aspects of the present disclosure. [Figure 24B]1 is a graph of power transfer efficiency with respect to load current for a wireless power transfer system operating in a forward power flow direction in accordance with aspects of the present disclosure. [Figure 24C] 1 is a graph of voltage with respect to load current for a wireless power transfer system operating in a forward power flow direction in accordance with aspects of the present disclosure. [Figure 25A] 1 is a graph of switch node voltages of a wireless power transfer system in a no-load condition operating in a forward power flow direction in accordance with an aspect of the present disclosure. [Figure 25B] 1 is a graph of switch node voltages of a wireless power transfer system under full load conditions operating in a forward power flow direction in accordance with an aspect of the present disclosure. [Figure 26A] 1 is a graph of input power and output power with respect to load current for a wireless power transfer system operating in a reverse power flow direction in accordance with aspects of the present disclosure. [Figure 26B] 10 is a graph of power transfer efficiency with respect to load current for a wireless power transfer system operating in a reverse power flow direction in accordance with aspects of the present disclosure. [Figure 26C] 1 is a graph of voltage with respect to load current for a wireless power transfer system operating in a reverse power flow direction in accordance with aspects of the present disclosure. [Figure 27A] 1 is a graph of switch node voltages of a wireless power transfer system under no-load conditions operating in a reverse power flow direction in accordance with an aspect of the present disclosure. [Figure 27B] 10 is a graph of switch node voltages of a wireless power transfer system under full load conditions operating in a reverse power flow direction in accordance with an aspect of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0061] The foregoing summary, and the following detailed description of certain embodiments, will be better understood when read in conjunction with the accompanying drawings. As used herein, elements or features referred to in the singular and preceded by the word "a" or "an" should be understood as not necessarily excluding the plural of the element or feature. Furthermore, references to "one embodiment" or "one example" are not intended to be construed as excluding the existence of additional embodiments that also incorporate the described element or feature. Moreover, unless expressly stated to the contrary, an embodiment or example that "comprises," "has," or "includes" an element or feature or elements or features having a particular characteristic may include additional elements or features that do not have that characteristic. It will be further understood that the terms "comprise (third person singular present tense)," "have (third person singular present tense)," and "including (third person singular present tense)" mean "including but not limited to," and that the terms "comprise (present participle)," "have (present participle)," and "including (present participle)" have equivalent meanings. It will be further understood that like reference numerals will be used throughout the description and drawings to refer to like elements.

[0062] 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. As such, use of the terms "adapted" and "configured" should be understood to mean that a given element, component, or other subject matter is specifically selected, created, implemented, utilized, and / or designed for the purpose of performing a function, rather than that the given element, component, or other subject matter is simply "potentially capable" of performing a given function. It is further within the scope of this disclosure that elements, components, and / or other subject matter that are 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 that is described as configured to perform a particular function may additionally or alternatively be described as operable to perform that function.

[0063] When an element is referred to as being "on," "attached to," "connected to," "coupled to," "in contact with," or otherwise, it will be understood that the element may be directly on, attached to, connected to, coupled to, or in contact with the other element, or that intervening elements may even be present.

[0064] Use of the word "exemplary" should be understood to mean "by way of illustration" or "one example," rather than to mean a preferred or best design or implementation, unless otherwise stated.

[0065] Turning now to FIG. 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 having a power source 112 electrically connected to a transmitting element 116, and a receiver 120 having 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. Exemplary wireless power transfer systems 100 include a high frequency inductive wireless power transfer system such as described in applicant's U.S. Provisional Application No. 62 / 899,165, or a resonant capacitively coupled wireless power transfer system such as described in applicant's U.S. Patent No. 9,653,948, relevant portions of which are incorporated herein by reference.

[0066] In the wireless power transfer system 100, power is transferred from the transmitting element 116 to the receiving element 124. It may be desirable to be able to transfer power to and from each respective element, i.e., from the receiving element 124 to the transmitting element 116. Turning now to FIG. 2 , a bidirectional power system, generally identified by reference numeral 130, is shown. As will be described, the bidirectional power system 130 is configured to transfer power in a forward power flow direction and extract power in a reverse power flow direction opposite the forward power flow direction. The bidirectional power system 130 may even transfer power in a reverse power flow direction and extract power in the forward power flow direction. In this context, forward and reverse refer to components of the system 130, as will be described.

[0067] The bidirectional power system 130 is for wirelessly transferring power and includes a transceiver element 140, a power stage 138, a switching element 136, a trigger circuit 132, and a clock generator 134.

[0068] The transceiver element 140 is for transmitting power by generating electric and / or magnetic fields and for extracting power from the generated electric and / or magnetic fields. Thus, the transceiver element 140 essentially forms, in a single component, a transmitting element for transmitting power by generating magnetic and / or electric fields and a receiving element for extracting power from the generated magnetic and / or electric fields. Although both electric and magnetic fields have been described, the transceiver element 140 may operate to transmit or extract power by a single field, electric or magnetic.

[0069] Although electromagnetic energy can be produced, the majority of power transmission or extraction may occur by only one of electrical induction, i.e., electric field coupling, and magnetic induction, i.e., magnetic field coupling. Little, if any, power is transmitted by the other one of magnetic induction and electric induction. Furthermore, induction may be resonant, i.e., resonant magnetic induction or resonant electric induction.

[0070] The transceiver element 140 comprises one or more capacitive electrodes and an inductive element, i.e., inductor. The capacitive electrodes may be laterally spaced elongated electrodes; however, one skilled in the art will recognize that other configurations are possible, including, but not limited to, concentric, coplanar, circular, elliptical, disc, and other electrodes. Other suitable electrode configurations are described in applicant's U.S. Pat. No. 9,979,206, relevant portions of which are incorporated herein by reference. The inductive element may comprise one or more coils. The coils may include booster or shield coils, such as those described in applicant's U.S. patent application Ser. No. 17 / 193,539, relevant portions of which are incorporated herein by reference.

[0071] The transceiver element 140 is electrically connected to the power stage 138. The power stage 138 is for inverting an input power signal and for rectifying a received power signal, as will be described. The power stage 138 inverts the power signal and inputs the inverted power signal to the transceiver element 140 for power transmission by generating magnetic and / or electric fields. Additionally, the power stage 138 rectifies the power signal received by the transceiver element 140 by extraction from the generated magnetic and / or electric fields.

[0072] The switching element 136 is a power stage 138 The switching element 136 is further selectively electrically connected to the clock generator 134 and the trigger circuit 132. Although the switching element 136 is described as a single element, those skilled in the art will appreciate that the switching element 136 may comprise multiple elements and may form a switching network.

[0073] Trigger circuit 132 is for synchronizing wireless power transfer. Trigger circuit 132 controls the operation of power stage 138 to synchronize the power signal received by transceiver element 140, as will be described.

[0074] The clock generator 134 is for generating a clock signal. In this embodiment, the clock generator 134 comprises an oscillator. The clock generator 134 is for providing a clock signal to the power stage 138. The clock signal controls the operation of the power stage 138 to invert an input power signal. The inverted power signal can then be transmitted by wireless power transmission in the transceiver element 140.

[0075] Operation of the switching element 136 causes the switching element 136 to electrically connect the power stage 138 to either the trigger circuit 132 or the clock generator 134 .

[0076] When switching element 136 electrically connects clock generator 134 to power stage 138, transceiver element 140 is configured to transmit power by generating electric and / or magnetic fields, as previously described. Power stage 138 is for inverting an input power signal such that transceiver element 140 receiving the inverted power signal can generate electric and / or magnetic fields. Clock generator 134 provides a clock signal to power stage 138 for inverting the input power signal.

[0077] When switching element 136 electrically connects trigger circuit 132 to power stage 138, transceiver element 140 is configured to extract power from the generated electric and / or magnetic fields, as previously described. Power stage 138 is for extracting power from the generated electric and / or magnetic fields to rectify the power signal received by the transceiver element. Trigger circuit 132 controls the operation of power stage 138 to synchronize the operation of power stage 138 with the power signal received by transceiver element 140.

[0078] Electrically connecting the power stage 138 to the trigger circuit 132 configures the transceiver element 140 to extract power. Electrically connecting the power stage 138 to the clock generator 134 configures the transceiver element 140 to transmit power.

[0079] The bidirectional power transfer system 130 may form part of a wireless power transfer system. An exemplary wireless power transfer system is shown in Figures 3A and 3B and is generally identified by reference numeral 150. The wireless power transfer system 150 comprises a first bidirectional power transfer system 152.

[0080] The first bidirectional power transmission system 152 forms a transmitter for transmitting power by generating magnetic and / or electric fields when the system 150 is operating in a forward power flow direction, as shown in Figure 3A. The first bidirectional power transmission system 152 forms a receiver for extracting power from the generated magnetic and / or electric fields when the system 150 is operating in a reverse power flow direction, as shown in Figure 3B. The system 150 further comprises a second bidirectional power transmission system 154.

[0081] The second bidirectional power transmission system 154 forms a receiver for extracting power from the magnetic and / or electric fields generated by the first bidirectional power transmission system 152 (transmitter) when the system 150 is operating in the forward power flow direction, as shown in Figure 3A. The second bidirectional power transmission system 154 forms a transmitter for transmitting power to the first bidirectional power transmission system 152 (receiver) by generating magnetic and / or electric fields when the system 150 is operating in the reverse power flow direction, as shown in Figure 3B.

[0082] The first bidirectional power transfer system 152 includes all of the previously described elements of the bidirectional power transfer system 130. The second bidirectional power transfer system 154 includes the same elements with an ' added to the reference numerals, e.g., the transceiver 140'.

[0083] 3A , wireless power transfer system 150 is configured to operate in a forward power flow direction such that power is transferred from first bidirectional wireless power transfer system 152 to second bidirectional power transfer system 154. Switching element 136 of first bidirectional wireless power transfer system 152 electrically connects power stage 138 to clock generator 134. Switching element 136′ of second bidirectional power transfer system 154 electrically connects power stage 138′ to trigger circuit 132′. These connections and the subsequent power transfer are outlined in dashed lines.

[0084] 3B, wireless power transfer system 150 is configured to operate in a reverse power flow direction such that power is transferred from second bidirectional power transfer system 154 to first bidirectional wireless power transfer system 152. Switching element 136' of second bidirectional power transfer system 154 electrically connects power stage 138' to clock generator 134'. Switching element 136 of first bidirectional power transfer system 152 electrically connects power stage 138 to trigger circuit 132. These connections and the subsequent power transfer are outlined in dashed lines.

[0085] Although not shown in Figures 3A and 3B, the bidirectional power transfer system 152, 154 may further include a power source for generating an input power signal for transferring power and a load for receiving the extracted power.

[0086] Additionally, while wireless power transfer system 150 has been described as including two bidirectional power transfer systems 152, 154, those skilled in the art will appreciate that other configurations are possible. For example, wireless power transfer system 150 may include a single bidirectional power transfer system that transfers power to a conventional wireless power transfer receiver or extracts power from a conventional wireless power transfer transmitter. Exemplary transmitters and receivers are described in commonly owned U.S. Patent Nos. 9,653,948, 10,424,942, and 10,033,225, as well as U.S. Patent Application Publication Nos. 2021 / 0021160, 2020 / 0227941, 2020 / 0203997, 2020 / 0203998, and 2020 / 0099254, the relevant portions of which are incorporated herein by reference.

[0087] 4, another embodiment of a wireless power transfer system is shown, generally identified by the reference numeral 200. The wireless power transfer system comprises a first bidirectional power transfer system 210 and a second bidirectional power transfer system 220.

[0088] In the forward power flow direction, the first bidirectional power transfer system 210 operates as a transmitter to transfer power to the second bidirectional power transfer system 220, which operates as a receiver to extract power from the magnetic and / or electric fields generated by the transmitter. In the reverse power flow direction, the second bidirectional power transfer system 220 operates as a transmitter to transfer power to the first bidirectional power transfer system 210, which operates as a receiver to extract power from the magnetic and / or electric fields generated by the transmitter.

[0089] Wireless power transfer system 200 includes a power supply 212, a load 213, a DC / DC converter 214, and a first bidirectional power transfer system 210. First bidirectional power transfer system 210 includes circuitry 216 and a transceiver element 222. Power supply 212 and load 213 are electrically connected to DC / DC converter 214. DC / DC converter 214 is electrically connected to circuitry 216. Circuitry 216 is electrically connected to transceiver element 222.

[0090] Power supply 212 is for generating an input power signal for transmission of power. In this example, the input power signal is a DC power signal. In this example, load 213 is a DC load. Load 213 can be static or variable. Although power supply 212 and load 213 are depicted as a single block, the power supply and load comprise two separate electrical components.

[0091] DC / DC converter 214 is for converting a received DC voltage signal to a desired voltage level. The received DC voltage can be from circuitry 216 or power supply 212, as will be described. While first bidirectional power transfer system 210 includes DC / DC converter 214, those skilled in the art will recognize that other configurations are possible. In another embodiment, there is no DC / DC converter.

[0092] Circuitry 216 includes clock generator 134, trigger circuit 132, switching element 136, and power stage 138, previously described.

[0093] The transceiver element 222 comprises one or more capacitive electrodes and an inductive element, i.e., inductor. The capacitive electrodes may be elongated electrodes spaced laterally apart; however, one skilled in the art will appreciate that other configurations are possible, including, but not limited to, concentric, coplanar, circular, elliptical, disk, and other electrodes. Other suitable electrode configurations are described in the previously mentioned U.S. Pat. No. 9,979,499. , No. 206. The inductive element may comprise one or more coils, which may include booster or shield coils as described in the previously mentioned U.S. patent application Ser. No. 17 / 193,539.

[0094] When operating in the forward power flow direction, power source 212 provides a DC input power signal to DC / DC converter 214, which converts the signal to a desired voltage level. Circuitry 216 receives the converted DC power signal and functions as an inverter by inverting the converted DC power signal to generate magnetic and / or electric fields in transceiver element 222 for transmitting power. Switching element 136 in circuitry 216 electrically connects clock generator 134 to power stage 138. In the forward power flow direction, first bidirectional power transfer system 210 acts as a transmitter.

[0095] When operating in the reverse power flow direction, transceiver element 222 extracts power from the generated magnetic and / or electric fields generated by transceiver element 229. Network 216 acts as a synchronous rectifier and rectifies the received power signal. DC / DC converter 214 converts the rectified power signal to a desired power level received by load 213. Switching element 136 in network 216 electrically connects trigger circuit 132 to power stage 138. In the reverse power flow direction, first bidirectional power transfer system 210 acts as a receiver.

[0096] The wireless power transfer system 200 includes a power supply 227, a load 228, a DC / DC converter 226, and a second bidirectional power transfer system 220. The second bidirectional power transfer system 220 includes circuitry 224 and a transceiver element 229. 7 and load 22 8 is electrically connected to a DC / DC converter 226. The DC / DC converter 226 is electrically connected to circuitry 224. The circuitry 224 is electrically connected to a transceiver element 229.

[0097] The power supply 228 is for generating an input power signal for transmission of power. In this embodiment, the input power signal is a DC power signal. In this embodiment, the load 22 8 is the DC load. Load 22 8 can be static or variable. 8 Although depicted as a single block, the power supply and load comprise two separate electrical components.

[0098] DC / DC converter 226 is for converting a received DC voltage signal to a desired voltage level. The received DC voltage can be from circuitry 224 or power supply 227, as will be described. Although second bidirectional power transfer system 220 includes DC / DC converter 226, one skilled in the art will recognize that other configurations are possible. In another embodiment, there is no DC / DC converter.

[0099] In this embodiment, DC / DC converters 214, 226 are bidirectional buck-boost converters. Buck / boost converters may have DC-DC converter inputs and outputs, which may be used interchangeably.

[0100] Circuitry 224 includes the previously described clock generator 134', trigger circuit 132', switching element 136', and power stage 138'.

[0101] The transceiver element 229 comprises one or more capacitive electrodes and an inductive element, i.e., inductor. The capacitive electrodes may be laterally spaced elongated electrodes; however, one skilled in the art will recognize that other configurations are possible, including, but not limited to, concentric, coplanar, circular, elliptical, disc, and other electrodes. Other suitable electrode configurations are described in the previously mentioned U.S. Pat. No. 9,979,206. The inductive element may comprise one or more coils. The coils may include booster or shield coils, such as those described in the previously mentioned U.S. patent application Ser. No. 17 / 193,539.

[0102] The transceiver elements 222, 229 of the bidirectional power transfer systems 210, 220 form a wireless link 230. The transceiver elements 222, 229 are separated by a wireless gap, which may be formed by the atmosphere, i.e., air. Power is transferred from one element to the other across the wireless link 230 by resonant or non-resonant magnetic and / or electric field coupling, i.e., electric or magnetic induction.

[0103] When operating in the forward power flow direction, transceiver element 229 extracts power from the magnetic and / or electric fields generated by transceiver element 222. Circuitry 224 includes synchronous rectification. vessel In the forward power flow direction, the second bidirectional power transfer system 220 acts as a receiver, rectifying the received power signal. The DC / DC converter 226 converts the rectified power signal to a desired power level to be received by the load 228. The switching element 136' in the network 224 electrically connects the trigger circuit 132' to the power stage 138'. In the forward power flow direction, the second bidirectional power transfer system 220 acts as a receiver.

[0104] When operating in the reverse power flow direction, power source 227 provides a DC input power signal to DC / DC converter 226, which converts the signal to a desired voltage level. Circuitry 224 functions as an inverter by receiving the converted DC power signal and inverting it to generate magnetic and / or electric fields in transceiver element 229 for transmitting power. Switching element 136' in circuitry 224 electrically connects clock generator 134' to power stage 138'. In the reverse power flow direction, second bidirectional power transmission system 220 acts as a transmitter.

[0105] 5, a portion of wireless power transfer system 200 is further illustrated including first bidirectional power transfer system 210. Circuitry 216 is shown enclosed by a dashed line. As previously described, when first bidirectional power transfer system 210 is operating as a transmitter in the forward power flow direction, power stage 138 of circuitry 216 is for inverting an incoming power signal. Switching element 136 electrically connects power stage 138 to clock generator 134.

[0106] In this embodiment, circuitry 216 includes a power stage 138 that includes an amplifier 215 and a matching network or circuit. Circuitry 216 further includes a switching element 136 and a clock generator 134 electrically connected to power stage 138.

[0107] In this embodiment, amplifier 215 is a class E amplifier. Amplifier 215 includes a gate driver 218 and a main switch. Gate driver 218 drives the main switch of amplifier 215. In this embodiment, the main switch includes an n-type MOSFET 218A. Although an n-type MOSFET 218A is illustrated, those skilled in the art will understand that other FETs and switching devices may be used. Clock generator 134 is electrically connected to gate driver 218 via switching element 136. Clock generator 134 includes an oscillator. Those skilled in the art will understand that clock generator 134 may include any non-controllable signal generator.

[0108] As previously described, power stage 138 includes a matching network or circuit. Various matching networks are possible. In this embodiment, the matching network includes an input stage in the form of a single-stage impedance inverter 219. Single-stage impedance inverter 219 is electrically connected to amplifier 215.

[0109] The clock generator 134 is configured to generate a clock signal to control a gate driver 218 connected to a main switch (MOSFET 218A) to convert an input power signal from a power source 212 (via a DC / DC converter 214) back into a radio frequency (RF) or alternating current (AC) signal. The current at the output of the single stage inverter 219 is load independent.

[0110] Although the network 216 has been described as having a discrete configuration, those skilled in the art will appreciate that other designs are also possible. For example, an additional stage with a 180 degree phase difference in the clock signals of the clock generator 134 may be implemented to make the network 216 a differential circuit.

[0111] As shown in FIG. 6A, a power supply 212, a DC / DC converter 214, and a network 216 including an amplifier 215 and a single stage impedance inverter 219 generate a current I s , and the impedance source 304 is modeled as a Norton equivalent circuit with a current source 302 generating a finite impedance Z s1 I s The value of Z depends on the input DC voltage to the network 216. The wireless link 230, including the transceiver elements 222, 229, is configured to have a Z impedance matrix 306 and a value Z that ensures resonance at the switching frequency in the network 216 of the first bidirectional power transfer system 210 and the network 224 of the second bidirectional power transfer system 220, respectively. t and Z r The impedances 308, 310 may be modeled as tuning impedances having

[0112] From the perspective of the circuitry 224 of the second bidirectional power transfer system 220, the power supply 212, the DC / DC converter 214, the circuit 216, and the wireless link 230 can be further modeled as a Thevenin equivalent circuit, as shown in FIG. oc and a dependent voltage source 312 having Z (s-r) and a source impedance 314 having an impedance of r and a series inductor 318 having capacitance C r The inductor 318 and the capacitor 316 resonate at the switching frequency. V oc and Z (s-r) The values ​​of Is, Z are expressed as shown in Equation 1 and Equation 2 below. s1 , Z t , Z r , and may be calculated based on the impedance matrix 306 (Z) of the wireless link 230.

number

[0113] For example, at a switching or resonant frequency of 27.12 MHz, a capacitive (field-coupled) wireless power transfer system using a 100 Ω resonator exhibits a V oc =36V rms voltage source, and Z s-r = 2.5Ω source impedance.

[0114] 7, the second bidirectional power transfer system 220, the DC / DC converter 226, and the load 228 are further illustrated. The circuitry 224 is shown enclosed by a dashed line. As previously described, when the second bidirectional power transfer system 220 is operating as a receiver in the forward power flow direction, the power stage 138' of the circuitry 224 is for rectifying the received power signal. The switching element 136' electrically connects the power stage 138' to the trigger circuit 132'.

[0115] In the illustrated arrangement, circuitry 224 includes a power stage 138' that includes an amplifier 240 and a matching network or circuit. Circuitry 224 further includes a switching element 136', a trigger circuit 132', and an auxiliary DC / DC converter 250. Amplifier 240 is electrically connected to the matching network or circuit.

[0116] In this embodiment, amplifier 240 is a class E amplifier, although other amplifier configurations are possible. Amplifier 240 includes a gate driver 260 and a main switch. Gate driver 260 drives the main switch of amplifier 240. In this embodiment, the main switch includes an n-type MOSFET 241. Although an n-type MOSFET 241 is illustrated, those skilled in the art will appreciate that other FETs and switching devices may be used.

[0117] Furthermore, although a class E amplifier has been illustrated and described, other amplifier types are possible as will be appreciated by those skilled in the art.

[0118] The auxiliary DC / DC converter 250 is electrically connected to a trigger circuit 132'. The trigger circuit 132' is electrically connected to an amplifier 240 via a switch 136'. The trigger circuit 132' is further electrically connected to a transceiver 229. The output of the amplifier 240 is electrically connected to the DC / DC converter 226 and the auxiliary DC / DC converter 250. The gate terminal of the MOSFET 241 is electrically connected to a gate driver 260.

[0119] The gate driver 260 is electrically connected to the main switch (MOSFET 241) of the amplifier 240 such that the amplifier 240 is controlled by the trigger circuit 132' via the gate driver 260 as will be described.

[0120] As previously described, the power stage 138' comprises a matching network or circuit. Various matching networks are possible. In this embodiment, the matching network comprises an input stage in the form of a dual-stage impedance inverter 231.

[0121] Typically, in a Class E amplifier, rectifier performance is optimized for a specified output load, i.e., the desired load. During operation, when the output load varies from the desired load, the amplifier DC voltage fluctuates significantly. Furthermore, when the output load varies from the desired load, the zero-voltage-switching (ZVS) operation of the main switch (MOSFET 241) of the amplifier 240 is impaired, resulting in unstable operation. In contrast, a load-independent Class E amplifier maintains ZVS operation of the switch of the amplifier 240 from no-load conditions, i.e., from zero load to full-load conditions. In addition, the rectified voltage remains relatively constant between no-load and full-load conditions. Switching losses from no-load to full-load conditions are approximately constant, and performance remains stable.

[0122] The class E amplifier design is adapted to convert input RF power to DC. The operating or switching frequency of amplifier 240 can be, for example, 6.78 MHz, 13.56 MHz, and 27.12 MHz. The voltage output by amplifier 240 is V rect-r Dual-Stage Impedance Inverter 23 1 The RF voltage input to the in In this example, the DC voltage V rect-r is unregulated. Because amplifier 240 comprises a load-independent amplifier, the switch node waveform does not vary significantly with load, as previously explained. Thus, the voltage is relatively stable.

[0123] Auxiliary DC / DC converter 250 converts V by amplifier 240 to power trigger circuit 132'. rect-r The output is set to an auxiliary voltage range, V, for example, in the 5V range. aux-rThe auxiliary signal V aux-r powers the trigger circuit 132'. Until the auxiliary DC / DC converter 250 is able to regulate, the MOSFET 241 is off and the amplifier 240 acts as a passive (diode) rectifier. In this embodiment, the auxiliary DC / DC converter 250 comprises a low-power buck converter.

[0124] The trigger circuit 132' receives a signal from the auxiliary DC / DC converter 250, e.g., V aux-r The trigger circuit 132' is powered by the RF power V output by the transceiver element 229. in and samples the signal at a properly timed trigger voltage V trig-r Produces a trigger voltage or signal V trig-r is the gate drive voltage or gate signal V by the gate driver 260. gate-r Output is input V in The trigger circuit 132' is timed to be in phase with the gate drive voltage or gate signal V gate-r As will be explained, the trigger circuit 132' receives an input signal V in Recover timing using trigger signal V trig-r In the illustrated arrangement, the trigger signal V trig-r includes a pulse signal.

[0125] Ideally, the main switch (MOSFET 241) of amplifier 240 is open when the incoming current is positive and closed when the incoming current is negative, thereby resulting in proper rectification. Assuming perfect tuning, V gate-r is V in should be in phase with

[0126] Gate driver 260 outputs a signal to switch MOSFET 241. In particular, gate driver 260 controls the operation of amplifier 240, e.g., controls the switching of MOSFET 241 of amplifier 240 by providing a gate drive voltage or gate signal V gate-r Output.

[0127] In this embodiment, the gate drive voltage V gate-r is the trigger voltage V into the gate driver 260 trig-r A delayed and more powerful replica of the input.

[0128] The gate driver 260 and the trigger circuit 132' exhibit a non-negligible propagation delay. To address the challenge of a non-negligible propagation delay from the gate driver 260 and the trigger circuit 132', the trigger circuit 132' is configured to gate-r V in To ensure that the trigger circuit 132' is synchronized with the output signal V trig-r is designed to further delay

[0129] As previously discussed, power supply 212, DC / DC converter 214, network 216, and wireless link 230 can be modeled as a Thevenin equivalent circuit, as shown in FIG. 6B. Source impedance Z s-r is small and resistive at the operating frequency.

[0130] This model assumes that both transceiver elements 222, 229 are well tuned, exhibit a high unloaded quality factor, and are well coupled, resulting in a high, i.e., greater than 90%, power transfer efficiency across the wireless link 230. As a result, the input voltage V in is a smooth sinusoid that remains relatively constant as the load changes, i.e., is load independent.

[0131] For the network 224 of the second bidirectional power transfer system 220 to be load independent, the phase of the pulse that triggers the MOSFET 241 is independent of the value of the load 228. According to equation (1), V oc The size of I s , and thereby varying the DC voltage on network 216. (s-r) Assuming a small value for , the voltage V in Figure 6B in can be used to generate a trigger signal for MOSFET 241 since its phase is independent of the value of load 228 .

[0132] 8 through 13, elements of the network 224 of the second bidirectional power transfer system 220 are better illustrated. As previously described, the network 224 comprises a matching network or circuit, which in this arrangement takes the form of an input stage. The input stage comprises a dual impedance inverter 231. An exemplary arrangement of the input stage implemented as a dual impedance inverter 231 is depicted in FIG. 8. The dual impedance inverter 231 is configured to match the optimum impedance of the network 224 to the impedance at the transceiver element 229. In this embodiment, the dual impedance inverter 231 is further configured to reduce harmonic content generated by the amplifier 240.

[0133] As shown in FIG. 8, the dual impedance inverter 231 is realized as two stages of an LC "T" network. Each of the two LC "T" networks comprises three series-connected inductors 320, 322, and 324, each having an inductance L2, L1+L2, and L1, respectively. A capacitor 326 with capacitance C2 is connected in parallel between the inductors 320 and 322. A capacitor 328 with capacitance C1 is connected in parallel between the inductors 322 and 324. The inductor 320 and capacitor 326 pair and the inductor 324 and capacitor 328 pair resonate at the switching frequency. The output voltage from the dual impedance inverter 231 to the amplifier 240 is V in-rx is.

[0134] The input impedance of amplifier 240 is Z (in-rx) and the impedance of the transceiver element 229 extracting power in the forward power flow direction is Z (in-r) At the switching frequency, their impedances are related by Equation 3, as shown below:

number

[0135] Although a particular network topology has been described, one skilled in the art will appreciate that other matching network topologies are possible, such as a "Pi" or "L" network.

[0136] 9, there is shown a circuit diagram of amplifier 240. Amplifier 240 receives an input RF signal V at the switching frequency from an input stage. in-rx , DC and voltage signals V rect-r In this embodiment, amplifier 240 comprises a class E amplifier.

[0137] The amplifier 240 includes an inductance L f-r +L a-ran inductor 330 having a capacitance C f-r and a capacitor 332 having an inductance L zvs-r and an inductor 334 having a D 1-r and a diode 336 designated as zvs-r a capacitor 338 having a rect-r The main switch (MOSFET 241), the capacitor 338, and the diode 336 are connected in parallel between the capacitor 332 and the inductor 334. The capacitor 340 has a voltage V rect-r and ground.

[0138] Additional filtering of the amplifier 240 input current is achieved by adding an additional inductance L in inductor 330, which is also resonant at the switching frequency. (f-r) , and capacitance C (f-r) The input current is assumed to be sinusoidal or approximately sinusoidal, so the following design equations 4 and 5 below may be applied to achieve load independence and zero voltage switching (ZVS) at 50% duty cycle of MOSFET 241.

number

[0139] where ω0 is the radian switching frequency.

[0140] C (j-r) is the junction capacitance of diode 336.

[0141] C oss-r is the drain terminal Q 1-r is the output capacitance of the MOSFET 241 at

[0142] and L a-ris the portion of the series inductance of inductor 330 required for proper ZVS.

[0143] Rectified DC voltage V rect-r Although the load is unregulated, the implementation of the load-independent topology ensures that the switch-node waveform does not vary significantly with load. Thus, the rectified voltage is relatively stable and amplifier 240 is load-independent.

[0144] Although a class E amplifier is depicted, other amplifiers are possible. For example, identical stages can be added to the amplifier depicted. In this configuration, the signal V gate-r is compared with the signal V rect-r A complementary gate signal connected to may be added to create a differential class E amplifier 240 stage.

[0145] The loads may require a separate voltage, and the previously described DC / DC converter 226 may then be used to provide the desired output voltage. rect-r V out-r Convert to.

[0146] The trigger circuit 132' is configured to synchronize wireless power transfer. The trigger circuit 132' controls the operation of the gate driver 260 and therefore the amplifier 240 to synchronize the operation of the amplifier 240 with the power signal received by the transceiver element 229.

[0147] Timing recovery is required to ensure proper switching of MOSFET 241. Ideally, synchronous MOSFET 241 is in the open position when the incoming current is positive and closed when the incoming current is negative, thereby resulting in rectification. Assuming input stage 230 is perfectly tuned, this means that V gate-r V in To achieve this, the trigger circuit 132' inand generates a properly timed trigger voltage V for the gate driver 260. trig-r produces.

[0148] Both the gate driver 260 and the trigger circuit 132' exhibit non-negligible propagation delays. To address these non-negligible propagation delays, the trigger circuit 132' uses a V gate-r V in The trigger circuit 132' is designed to further delay the signal until it is synchronized with the

[0149] As such, trigger circuit 132' is an “RX time recovery trigger circuit.” Trigger circuit 132' operates to achieve synchronous rectification in the forward power flow direction.

[0150] 10, a block diagram of trigger circuit 132', switching element 136', auxiliary DC / DC converter 250, and amplifier 240 is depicted. Trigger circuit 132' is outlined in dashed lines and receives input voltage V from transceiver element 229. in 7. The trigger circuit 132' receives the extracted power signal at the amplifier 240 via the switching element 136' and is electrically connected to the auxiliary DC / DC converter 250. In particular, the trigger circuit 132' is electrically connected to the gate driver 260 of the amplifier 240 via the switching element 136', as shown in FIG. 7. The amplifier 240 is electrically connected to the auxiliary DC / DC converter 250.

[0151] The gate driver 260 of the amplifier 240 generates the appropriate waveform to switch the MOSFET 241 on or off. The associated gate drive voltage V gate-r is essentially the input trigger voltage V trig-r It is a delayed and more powerful replica of

[0152] As previously described, the auxiliary DC / DC converter 250 powers the trigger circuit 132'.

[0153] The trigger circuit 132' includes a sampling circuit 272, a delay line 274, and a comparator circuit 276. The sampling circuit 272 is a voltage sampling circuit. In this embodiment, the voltage sampling circuit is a voltage divider. The sampled input voltage V in is fed from the voltage divider into a delay line 274. The delay line 274 comprises a lumped element delay circuit. A comparator circuit 276 outputs the delayed signal V d-r is used to generate a clock signal by comparing the voltage V to a DC level. The resulting trigger voltage V trig-r is fed to the amplifier 240, and in particular to the gate driver 260, which provides a trigger voltage in the form of a suitable waveform V to drive the MOSFET 241 of the amplifier 240. gate-r The voltage sampling circuit 272, delay line 274, and comparator circuit 276 convert V gate-r V in It is configured to be synchronized with.

[0154] 11, sampling circuit 272 is further illustrated. Sampling circuit 272 is a voltage sampling circuit. Sampling circuit 272 is implemented using a capacitive voltage divider network to reduce the voltage swing to a range suitable for comparator circuit 276. The voltage divider network has a capacitance C s1-r and a capacitor 342 having an inductance L s-r an inductor 344 having a capacitance C s2-r and a capacitor 346 having a capacitance of 1. The capacitor 342 is connected in series with the inductor 344. The capacitor 346 is connected in parallel between the capacitor 342 and the inductor 344.

[0155] The inductor 344 is configured to cancel the associated capacitive reactance before the delay line 274 .

[0156] Turning now to FIG. 12, a circuit diagram of delay line 274 is shown. In this embodiment, delay line 274 is implemented as a multi-stage lumped-element transmission line circuit. Each lumped element comprises an LC element. In the illustrated arrangement, the lumped-element transmission line circuit comprises four lumped-element stages uniformly spaced along the line circuit. While FIG. 12 illustrates a uniformly spaced delay line 274, the components in each stage need not necessarily be identical, and the number of stages may be less than or greater than four.

[0157] Although discrete lumped elements of passive inductors and capacitors have been described for delay line 274, those skilled in the art will appreciate that other configurations of delay circuits are possible, such as integrated analog or digital delay circuits.

[0158] In the illustrated arrangement, the lumped element transmission line circuit comprises four inductors 350, 352, 354, 356 arranged in series and four capacitors 360, 362, 364, 366 arranged in parallel between the inductors 350, 352, 354, 356 and a resistor 368 having a resistance value Z0. dr and C dr The total inductance and capacitance associated with delay line 274, represented by inductors 350, 352, 354, 356 and capacitors 360, 362, 364, 366, respectively, is divided (L d-r and C d-r components).

[0159] Assuming that delay line 274 is match terminated, the associated time delay is given by Equation 6 below.

number

[0160] If it is further assumed that the delay line 274 is lossless, the characteristic impedance Z0 can be given by Equation 7 below.

number

[0161] As a result, Z0 and τ d is chosen, the inductance L of the inductor for a delay line with uniform division of, say, four stages. d-r , and the capacitance of the capacitor C d-r is given by the following equation 8.

number

[0162] The delay is terminated by a resistor 368 having a value of Z0, the characteristic impedance, and the voltage across this termination is V d-r V, represented by in is a scaled and delayed version of

[0163] V in and V gate-r To achieve the precise delay required to synchronize the delay lines 274, it may be necessary to reduce or increase the delay in one of the stages, or to have more or fewer than four stages. Reducing or increasing the delay in one or more of the stages requires using different inductance or capacitance values ​​for any individual stage. However, the selected inductor and capacitor values ​​must satisfy Equation 7, since the characteristic impedance must be the same.

[0164] 13, a circuit diagram of a portion of trigger circuit 132', switching element 136', gate driver 260, and auxiliary DC / DC converter 250 is shown. In particular, comparator circuit 276 of trigger circuit 132' is illustrated. Comparator circuit 276 compares signal V delayed by delay line 274 with d-r13, a comparator circuit 276 is provided for generating a clock signal by comparing the output of the auxiliary supply voltage V aux-r A comparator 277 (A 1-r ) is provided.

[0165] The input to comparator 277 is V aux-r The positive comparator input V +r For R2, this is accomplished using two equal value resistors 372, 376, each with a resistance of R2.

[0166] Negative comparator input V -r is achieved using two equal value resistors 370, 374, each with a resistance of R1.

[0167] The voltage signal V delayed by the delay line 274 d-r The output is capacitance C b-r The negative comparator input V -r and then the trigger voltage V trig-r is the delayed voltage signal V d-r V gate-r V in In terms of the overall delay required to ensure that the delay line 274 is in phase with the input signal, this effectively accounts for half the switching period, thus reducing the burden on the delay line 274. As a result, the overall delay (τ dr ) is given by the following equation 9:

number

[0168] where Ts is the switching period, τc is the propagation delay of the comparator 277, and τg is the propagation delay of the gate driver 260.

[0169] The output of the gate driver 260 is the gate signal V gate-r to the MOSFET 241 through resistor R g-r is connected to a resistor 380 having a

[0170] Shortly after start-up, the output voltage V out-r will be less than the turn-on voltage of auxiliary DC / DC converter 250 because MOSFET 241 of amplifier 240 is off and diode 336 is performing rectification. out-r When V exceeds this turn-on threshold voltage of the auxiliary DC / DC converter 250, V aux-r begins to rise to its nominal value. The presence of capacitor 371 reduces the negative input V -r This has the effect of slowing the rise time of V. +r Unless otherwise specified, a significant time interval during which its positive input V +r is the negative input V -r and thus the trigger voltage V trig-r There may be significant periods of time during which the capacitance C st-r A shunt capacitor 378 having a negative input voltage V -r During start-up, the positive input voltage V +r To ensure that the positive input V +r This capacitance C of the shunt capacitor 378 is added to st-r is the capacitance C of the blocking capacitor 371 b-r In an exemplary arrangement, C b-r If is 200nF, then C st-r may be 470nF.

[0171] As previously described, when operating in the forward power flow direction, the first bidirectional power transfer system 210 operates as a transmitter. The power supply 212 outputs a voltage, which is converted to the required level by the DC / DC converter 214. The amplifier 215 of the power stage 138 receives the converted voltage. The gate driver 218 of the amplifier 215 drives the main switch (MOSFET 218A) of the amplifier 215 under the control of the clock signal generated by the clock generator 134 via the switching element 136 to invert the input power signal (converted voltage). The single-stage impedance inverter 219 receives this signal to output a current that is load-independent. The impedance inverter 219 drives the first transceiver element 222 of the first bidirectional power transmission system 210 to transmit power by wireless coupling (electric field and / or magnetic field coupling) to the second transceiver element 229 of the second bidirectional power transmission system 220.

[0172] When operating in the forward power flow direction, the second bidirectional power transmission system 220 operates as a receiver. The received voltage V at the second transceiver element 229 in The trigger circuit 132′ and the power stage 13 of the second bidirectional power transmission system 220 are 8 ' (network 224). The dual-stage impedance inverter 231 of network 224 generates a voltage V in and matches the voltage to the optimum impedance of the network 224. The trigger circuit 132' controls the operation of the gate driver 260 of the amplifier 240 via the switching element 136'. Specifically, the trigger circuit 132' receives the input voltage V in and generates a properly timed trigger voltage V for the gate driver 260. trig-r The gate driver 260 generates the trigger voltage V received from the trigger circuit 132′. trig-r , to control the operation of amplifier 240, e.g., to control the switching of MOSFET 241 of amplifier 240, a gate drive voltage or gate signal V gate-rThe amplifier 240 then outputs a DC voltage V rect-r to a DC / DC converter 226. The DC / DC converter 226 outputs a DC voltage V rect-r The desired V out-r Convert to DC voltage V rect-r is further used by the auxiliary DC / DC converter 250 to power the trigger circuit 132'.

[0173] The wireless power transfer system will now be described as operating in the reverse power flow direction.

[0174] 14 , a portion of wireless power transfer system 200 is further illustrated including second bidirectional power transfer system 220. Circuitry 224 is shown enclosed by a dashed line. As previously described, when second bidirectional power transfer system 220 is operating as a transmitter in the reverse power flow direction, power stage 138′ of circuitry 224 is for inverting an incoming power signal. Switching element 136′ electrically connects power stage 138′ to clock generator 134′.

[0175] The network 224 includes a power stage 138' that includes an amplifier 240 and a matching network or circuit. In this embodiment, the matching network or circuit takes the form of a dual stage impedance inverter 231.

[0176] As previously explained, amplifier 240 is a class E amplifier and comprises a gate driver 260 and a main switch in the form of a MOSFET 241. Clock generator 134' is connected to gate driver 260 via switching element 136'. Clock generator 134' comprises an oscillator. Those skilled in the art will appreciate that clock generator 134' may comprise any non-controllable signal generator.

[0177] The clock generator 134' is configured to generate a clock signal to control a gate driver 260 connected to the main switch (MOSFET 241) to convert the input power signal from the power source 227 (via the DC / DC converter 226) back into an RF or AC signal. The voltage at the output of the dual stage inverter 231 is load independent.

[0178] Although the network 224 has been described as having a discrete configuration, one skilled in the art will appreciate that other designs are also possible. For example, an additional stage with a 180 degree phase difference in the clock signals of the clock generator 134' may be implemented to make the network 224 a differential circuit.

[0179] The network 224, including the power supply 227, the DC / DC converter 226, the amplifier 240, and the dual-stage impedance inverter 231, may be modeled as a Thevenin equivalent circuit, as shown in Figure 15A. s and a voltage source 402 generating an impedance Z s2 and an impedance source 404 having V s The value of Z depends on the input DC voltage to the network 224. The wireless link 230, including the transceiver elements 222, 229, is configured to have a Z impedance matrix 408 and a value Z that ensures resonance at the switching frequency in the network 224 of the second bidirectional power transfer system 220 and the network 216 of the first bidirectional power transfer system 210, respectively. t and Z r The impedances 410, 406 may be modeled as tuning impedances having

[0180] The power supply 227, DC / DC converter 226, circuitry 224, and wireless link 230 can be further modeled as a Norton equivalent circuit, as shown in Figure 15B. This equivalent circuit has a current I sc and a dependent current source 412 having Z s-tand a source impedance 414 having a finite source impedance of r and a series inductor 418 having capacitance C r The inductor 418 and capacitor 416 resonate at the switching frequency. I sc and Z s-t The value of V is expressed as shown in Equation 10 and Equation 11 below. s , Z s2 , Z t , Z r , and the impedance matrix (Z) of the wireless link 230.

number

[0181] 16 , a portion of the wireless power transfer system 200 is further illustrated, including the first bidirectional power transfer system 210. Circuitry 216 is shown enclosed by a dashed line. As previously described, when the first bidirectional power transfer system 210 is operating as a receiver in the reverse power flow direction, the power stage 138 of the circuitry 216 is for rectifying the received power signal. The switching element 136 electrically connects the power stage 138 to the trigger circuit 132.

[0182] As previously described, circuitry 216 includes a power stage 138 that includes an amplifier 215 and a matching network or circuit in the form of a single stage impedance inverter 219. Circuitry 216 further includes a trigger circuit 132 that is electrically connected to a gate driver 218 of amplifier 215 via a switching element 136. Circuitry 216 further includes an auxiliary DC / DC converter 250' that is electrically connected to trigger circuit 132.

[0183] As previously described, amplifier 215 is a class E amplifier. Amplifier 215 comprises a gate driver 218 and a main switch in the form of a MOSFET 218A.

[0184] Typically, in a Class E amplifier, rectifier performance is optimized for a specified output load, i.e., the desired load. During operation, when the output load varies from the desired load, the amplifier DC voltage fluctuates significantly. Furthermore, when the output load varies from the desired load, the zero-voltage switching (ZVS) operation of the main switch (MOSFET 218A) of amplifier 215 is impaired, resulting in unstable operation. In contrast, a load-independent Class E amplifier maintains ZVS operation of the switch of amplifier 215 from no-load conditions, i.e., from zero load to full-load conditions. In addition, the rectified voltage remains relatively constant between no-load and full-load conditions. Switching losses from no-load to full-load conditions are approximately constant, and performance remains stable.

[0185] The class E amplifier design is adapted to convert input RF power to DC. The operating or switching frequency of amplifier 215 can be, for example, 6.78 MHz, 13.56 MHz, and 27.12 MHz. The voltage output by amplifier 215 is V rect-t The RF current input into the single stage impedance inverter 219 is I in In this example, the DC voltage V rect-t is unregulated. Because amplifier 215 comprises a load-independent amplifier, the switch node waveform does not vary significantly with load, as previously explained. Thus, the voltage is relatively stable.

[0186] Auxiliary DC / DC converter 250' converts V by amplifier 215 to power trigger circuit 132. rect-t The output is set to an auxiliary voltage range, V, for example, in the 5V range. aux-t The auxiliary signal V aux-tpowers the trigger circuit 132. Until the auxiliary DC / DC converter 250' is able to regulate, MOSFET 218A is off and amplifier 215 acts as a passive (diode) rectifier. In this embodiment, auxiliary DC / DC converter 250' comprises a low-power buck converter.

[0187] The trigger circuit 132 receives a signal from the auxiliary DC / DC converter 250′, e.g., V aux-t The trigger circuit 132 is powered by the RF power input I output by the transceiver element 222. in and samples the signal at a properly timed trigger voltage V trig-t Produces a trigger voltage or signal V trig-t is the gate drive voltage or gate signal V by the gate driver 218. gate-t The output is the input current I in The trigger circuit 132 is timed to be 90 degrees out of phase with the gate driver 218. gate-t As will be explained, the trigger circuit 132 is connected to the input current I in Recover timing using trigger signal V trig-t In the illustrated arrangement, the trigger signal V trig-t includes a pulse signal.

[0188] Ideally, the main switch (MOSFET 218A) of amplifier 215 is open when the incoming current is positive and closed when the incoming current is negative, thereby resulting in proper rectification. Assuming perfect tuning, V gate-t I in It should be 90 degrees out of phase with the

[0189] Gate driver 218 outputs a signal to switch MOSFET 218A. In particular, gate driver 218 controls the operation of amplifier 215, e.g., controls the switching of MOSFET 218A of amplifier 215 by providing a gate drive voltage or gate signal V gate-t Output.

[0190] In this embodiment, the gate drive voltage V gate-t is the trigger voltage V into the gate driver 218 trig-t A delayed and more powerful replica of the input.

[0191] The gate driver 218 and trigger circuit 132 exhibit a non-negligible propagation delay. To address the challenge of the non-negligible propagation delay from the gate driver 218 and trigger circuit 132, the trigger circuit 132 is configured to provide a gate-t V in To ensure that the trigger circuit 132 is synchronized with the output signal V trig-t is designed to further delay

[0192] Turning now to FIG. 17, the single impedance inverter 219 is realized as a single stage of an LC "T" network. The LC "T" network comprises two series-connected inductors 420, 422, each having an inductance L3. A capacitor 424 with capacitance C3 is connected in parallel between the inductors 420 and 422. The inductors 420, 422 and capacitor 424 resonate at the switching frequency. The output voltage from the single impedance inverter 219 to the amplifier 215 is V in-tx is.

[0193] The input impedance of amplifier 215 is Z in-tx and the impedance of the transceiver element 222 extracting power in the reverse power flow direction is Z in-t At the switching frequency, their impedances are related by Equation 12:

number

[0194] Although a particular network topology has been described, one skilled in the art will appreciate that other matching network topologies are possible, such as a "Pi" or "L" network.

[0195] 18, a circuit diagram of amplifier 215 is illustrated. Amplifier 215 receives an input RF signal V at the switching frequency from the input stage. in-tx , DC and voltage signals V rect-t In this embodiment, amplifier 215 comprises a class E amplifier.

[0196] The amplifier 215 is connected in series with an inductance L f-t +L a-t an inductor 430 having a capacitance C f-t and a capacitor 432 having an inductance L zvs-t and an inductor 434 having a D 1-t and a diode 436 designated as zvs-t a capacitor 438 having a rect-t The main switch (MOSFET 218A), capacitor 438, and diode 436 are connected in parallel between capacitor 432 and inductor 434. Capacitor 440 has a voltage V rect-t and ground.

[0197] The component sizes for amplifier 215 are governed by similar equations already discussed with reference to Equations 4 and 5.

[0198] As with trigger circuit 132' when operating in the forward power flow direction, trigger circuit 132 also operates in the reverse power flow direction to prevent wireless power transfer. The sameThe trigger circuit 132 controls the operation of the power stage gate driver 218 and therefore the amplifier 215 to synchronize the operation of the amplifier 215 with the power signal received by the transceiver element 222.

[0199] Timing recovery is required to ensure proper switching of MOSFET 218A. Ideally, MOSFET 218A is in the open position when the incoming current is positive and closed when the incoming current is negative, thereby resulting in rectification. Assuming all of the input stages 219 are perfectly tuned, this means that V gate-t I in This means that the signal should be 90 degrees out of phase with I. To achieve this, the trigger circuit 132 in and generates a properly timed trigger voltage V for the gate driver 218. trig-t produces.

[0200] Both the gate driver 218 and the trigger circuit 132 exhibit non-negligible propagation delays. To address these non-negligible propagation delays, the trigger circuit 132 gate-t I in The trigger circuit 132 is designed to further delay the signal until it is synchronized with the

[0201] As such, trigger circuit 132 is a “TX time recovery trigger circuit.” Trigger circuit 132 operates to achieve synchronous rectification in the reverse power flow direction.

[0202] 19, there is illustrated a block diagram of transceiver element 222, impedance inverter 219 (comprising inductors 420, 422 and capacitor 424), trigger circuit 132, switching element 136, auxiliary DC / DC converter 250′, and amplifier 215. Trigger circuit 132 is outlined in dashed lines.

[0203] The gate driver 218 of the amplifier 215 generates the appropriate waveform to switch the MOSFET 218A on or off. The associated gate drive voltage V gate-t is essentially the input trigger voltage V trig-t It is a delayed and more powerful replica of

[0204] As previously described, the auxiliary DC / DC converter 250 ′ powers the trigger circuit 132 .

[0205] The trigger circuit 132 comprises a sampling circuit 272', a delay line 274', and a comparator circuit 276'. The trigger circuit 132 samples the voltage across the inductor 420 of the impedance inverter 219. In particular, the sampling circuit 272' is a voltage drop sampling circuit. The voltage drop across the inductor 420 of the impedance inverter 219 is sampled by the sampling circuit 272' and fed into a lumped element delay line circuit 274'. The delay line 274' comprises a lumped element delay circuit. The comparator 276' then outputs the delayed signal V d-t is used to generate a clock signal by comparing the voltage V to a DC level. The resulting trigger voltage V trig-t is fed through switching element 136 to gate driver 218. Gate driver 218 applies a trigger voltage V trig-t The appropriate waveform V gate-t Convert to.

[0206] The sampling circuit 272', the delay line circuit 274', and the comparator circuit 276' all receive the voltage V gate-t But the inductor current I in 90 degrees out of phase with the inductor 420, or the voltage difference ΔV L3 is designed to ensure that the

[0207] 20, there is illustrated transceiver element 222, single stage impedance inverter 219 (comprising inductors 420, 422 and capacitor 424), sampling circuit 272', and amplifier 215. Sampling circuit 272' is shown in dashed lines. Sampling circuit 272' is a voltage drop sampling circuit.

[0208] A single stage impedance inverter 219 is connected between the transceiver element 222 and the amplifier 215. The input current I in The output current (from the transceiver element 222 ) flows through the inductor 420 of the impedance inverter 219 .

[0209] current I in can be difficult to sample. Furthermore, the current I in The phase of can be difficult to track for use as a source signal to generate a trigger signal by trigger circuit 132. As such, the voltage drop across inductor 420 of single stage impedance inverter 219 can be used. This signal may be used as a source signal to generate a trigger signal for MOSFET 241 in network 224. The relationship between the voltage drop across an inductor and the current through that inductor is given by Equation 13 below: v L =jωL×i L (Formula 13)

[0210] If the voltage drop across inductor 420 in impedance inverter 219 is used as the source signal to generate the trigger signal, the generated trigger will be in phase with the voltage drop across inductor 420. Those skilled in the art will appreciate that the current I in It will be appreciated that other methods of sampling and tracking the phase of may be used.

[0211] The sampling circuit 272' scales down the voltage drop across the inductor 420. The sampling circuit 272' scales down the voltage drop across the capacitance Cs1-t and capacitors 450, 452 each with a capacitance C s2-t The capacitors 450 and 452 comprise a capacitive divider network comprising capacitors 456 and 458 each with an inductor 42 0, and capacitors 456, 458 are connected between capacitors 450 and 452, respectively, and ground, in a natural fashion. Capacitors 450, 456 are in series, and capacitors 452, 458 are in series. Inductance L s-t Inductors 454, 460, each with s2-t Each inductor 454, 460 is connected to the middle of a respective capacitor pair 450, 456 and 452, 458. The inductors 454, 460 are positioned to compensate for the output voltage V B In the illustrated arrangement, the balun 462 is an unbalanced-unbalanced balun; however, the balun 462 could be unbalanced-balanced.

[0212] Ideally, the output voltage of the balun 462, V B is in phase with the voltage drop across inductor 420. However, there may be a delay that can be difficult to predict in advance. The delay may be caused by PCB (printed circuit board) wiring or by balun 462.

[0213] The ratio of the capacitor divider network and the turns ratio of the balun 462 is V B The coupling ratio between elements 222, 229 also determines the magnitude of the capacitance C s1-t and C s2-t are taken into account in determining

[0214] The scaled-down sampled voltage is fed into a delay line 274' as shown in Figure 20. The delay line 274' is shown in Figure 21. The delay line 274' functions in the same manner as the delay line 274 of the second bidirectional power transfer system 220.

[0215] In this embodiment, delay line 274' is implemented as a multi-stage lumped-element transmission line circuit. Each lumped element comprises an LC element. In the illustrated arrangement, the lumped-element transmission line circuit comprises four lumped-element stages evenly spaced along the line circuit. While FIG. 21 illustrates a uniformly spaced delay line 274', the components in each stage need not necessarily be identical, and the number of stages may be less than or greater than four.

[0216] Although discrete lumped elements of passive inductors and capacitors have been described for delay line 274', those skilled in the art will appreciate that other configurations of delay circuits are possible, such as integrated analog or digital delay circuits.

[0217] In the illustrated arrangement, the lumped element transmission line circuit comprises four inductors 470, 472, 474, 476 arranged in series and four capacitors 480, 482, 484, 486 arranged in parallel between the inductors 470, 472, 474, 476 and a resistor 488 having a resistance value Z0. dt and C dt The total inductance and capacitance associated with delay line 274', represented by each, is divided among inductors 470, 472, 474, 476 and capacitors 480, 482, 484, 486 (L d-t and C d-t components).

[0218] The time delay and the parameters of the delay line 274′, L dt and C dt is given by equations 6 to 8 discussed above.

[0219] The delayed voltage signal V d-t is then fed into a comparator circuit 276' illustrated in Figure 22. The comparator circuit 276' receives the delayed signal V d-t22, a comparator circuit 276' is provided for generating a clock signal by comparing the output of the auxiliary supply voltage V aux-t A comparator 277' (A 1-t ) The comparator circuit 276' is the same as the comparator circuit 276 illustrated in FIG.

[0220] The input of comparator 277' is V aux-t The positive comparator input V +t For R2, this is achieved using two equal value resistors 508, 510, each with a resistance of R2.

[0221] Negative comparator input V -t This is accomplished using two equal value resistors 504, 506, each with a resistance of R1.

[0222] The voltage signal V delayed by the delay line 274' d-t The output is capacitance C b-t The negative comparator input V -t and then the trigger voltage V trig-t is the delayed voltage signal V d-t The signal is inverted relatively (out of phase by 180°).

[0223] Gate Driver 21 8 The output of the gate signal V gate-t to MOSFET 218A through resistor R g-t is connected to a resistor 514 having a

[0224] As previously described, when operating in the reverse power flow direction, the second bidirectional power transfer system 220 operates as a transmitter. The power supply 227 outputs a voltage, which is converted to the required level by the DC / DC converter 226. The circuitry 224 receives the converted voltage. The gate driver 260 of the amplifier 240 drives the main switch (MOSFET 241) of the amplifier 240 under the control of a clock signal generated by the clock generator 134' to invert the input power signal (the converted voltage). The dual-stage impedance inverter 231 receives this signal to output a load-independent voltage. The impedance inverter 231 drives the second transceiver element 229 to transmit power via wireless coupling (electric and / or magnetic field coupling) to the first transceiver element 222 of the first bidirectional power transfer system 210.

[0225] When operating in the reverse power flow direction, the first bidirectional power transmission system 210 operates as a receiver. In a traditional manner, the received input current I at the first transceiver element 222 is used by the trigger circuit 132 and circuitry 216 of the first bidirectional power transmission system 210. in The single-stage impedance inverter 219 of the network 216 converts the input current I in and matches the current to the optimum impedance of the network 216. The trigger circuit 132 controls the operation of the gate driver 218 of the amplifier 215 via the switching element 136. Specifically, the trigger circuit 132 samples the voltage drop and generates a properly timed trigger voltage V for the gate driver 218. trig-t The gate driver 218 generates the trigger voltage V received from the trigger circuit 132. trig-t , a gate drive voltage or gate signal V to control the operation of amplifier 215, e.g., to control the switching of MOSFET 218A of amplifier 215. gate-t The amplifier 215 then outputs a DC voltage V rect-tThe DC / DC converter 214 outputs a DC voltage V rect-t The desired V out-t Convert to DC voltage V rect-t is further used by the auxiliary DC / DC converter 250 ′ to power the trigger circuit 132 .

[0226] An experimental wireless power transfer system 200 was created to test the performance of the system 200. Turning now to FIG. 23A , there is shown a PCB 602 including a portion of the first bidirectional power transfer system 210. The PCB 602 includes electrical components forming the amplifier 215 in area 1, the single stage impedance inverter 219 in area 2, the sampling circuit 272′ in area 3, the delay line 274′ in area 4, the comparator circuit 276′ in area 5, the switching element 136, the gate driver 218, the clock generator 134 in area 6, and the auxiliary DC / DC converter 250′ in area 7.

[0227] 23B, there is shown a PCB 604 that includes a portion of the second bidirectional power transfer system 220. The PCB 604 includes electrical components that form the amplifier 240 in area 1, the dual stage impedance inverter 231 in area 2, the sampling circuit 272 in area 3, the delay line 274 in area 4, the comparator circuit 276, the switching element 136′, and the gate driver 260 in area 5, the clock generator 134′ in area 6, and the auxiliary DC / DC converter 250 in area 7.

[0228] Testing of the systems 210, 220 was performed at a switching frequency of 27.12 MHz using the PCB illustrated in Figures 23A and 23B with 100 Ω capacitive electrodes as the transceiver elements 222, 229. A solenoidal air-core inductor was used to establish the resonant behavior of the transceiver elements 222, 229.

[0229] The networks 216, 224 were designed for 40 W power output to deliver 35 W to DC loads 228, 213, which are electronic DC loads in the forward and reverse power flow directions, respectively.

[0230] The switching elements 136, 136' of the systems 210, 220 were operated to connect the respective power stages 138, 138' to the clock generators 134, 134' for inverting the incoming power signal or to the trigger circuits 132, 132' for rectifying the received power signal.

[0231] When operating in the forward power flow direction, the DC / DC converter 214 connected to the PCB 602 and power supply 212 of the first system 210 was supplied with a 24V DC power supply, and the DC / DC converter 226 connected to the PCB 604 of the second system 220 output a regulated 24V to the electronic load (DC load 228).

[0232] 24A through 24C, various graphs depicting operation in the forward power flow direction are shown. FIG. 24A depicts the input power of the power supply 212 and the output power delivered to the load 228 in relation to the load current when an experimental wireless power transfer system is operated in the forward power flow direction. As shown in FIG. 24A, with no output load (DC load 228), approximately 21 W is required to power the wireless power transfer system. A nominal output power of 36.48 W is achieved when the load current is 1.5 A.

[0233] Figure 24B depicts the end-to-end power transfer efficiency for the experimental system with respect to load current. The power transfer efficiency is obtained by dividing the output and input power shown in Figure 24A. The peak power transfer efficiency is approximately 55% at 1.5A.

[0234] FIG. 24C depicts the voltage stability of the experimental system. In particular, the input voltage (V INPUT ) at power supply 212, the output voltage (V INPUT ) at DC / DC converter 226, and the out-r ) (output voltage), the output voltage at the DC / DC converter 214 (TX DC voltage), and the rectified voltage with respect to the load current (V rect-r ) (rectified voltage on RX) is depicted.

[0235] The input voltage and output voltage (V out-r ) is generally stable throughout the current range with a voltage of approximately 24V. Out The output voltage is approximately 17.2 V. Thus, the DC / DC converter 214 converts the input voltage from 24 V to 17.2 V. The rectified voltage (V rect-r ) is approximately 23.6V at no load (0A) and decreases to approximately 18.3V at 1.5A load current. This voltage is converted to 24V by a DC / DC converter 226 connected to a load 228.

[0236] 25A and 25B are graphs of the switch node voltage of amplifier 240 on PCB 604 under no-load and full-load conditions, respectively.

[0237] When operating in the reverse power flow direction, the DC / DC converter 226 connected to the PCB 604 and power supply 227 of the second system 220 was supplied with a 24V DC power supply, and the DC / DC converter 214 connected to the PCB 602 of the first system 210 output a regulated 24V to the electronic load (DC load 213).

[0238] 26A through 26C, various graphs are shown depicting operation in the reverse power flow direction. reverse26A depicts the input power of the power supply 227 and the output power delivered to the load 213 in relation to the load current when operated in the row power flow direction. As shown in FIG. 26A, with no output load (DC load 213), approximately 22 W is required to power the wireless power transfer system. A nominal output power of 36.4 W is achieved when the load current is 1.5 A.

[0239] Figure 26B depicts the end-to-end power transfer efficiency for the experimental system with respect to load current. The power transfer efficiency is obtained by dividing the output and input power shown in Figure 26A. The peak power transfer efficiency is approximately 52% at 1.5A.

[0240] FIG. 26C depicts the voltage stability of the experimental system. In particular, the input voltage (V INPUT ) at the power supply 227, the output voltage (V INPUT ) at the DC / DC converter, and the out-t )(out Power pressure ) , the output voltage at the DC / DC converter 226 (RX DC voltage), and the rectified voltage with respect to the load current (V rect-t ) (rectified voltage on TX) is depicted.

[0241] The input voltage and output voltage (V out-t ) is generally stable throughout the current range with a voltage of approximately 24V. The output voltage of the DC / DC converter 226 is approximately 26.4V. Thus, the DC / DC converter 226 converts the input voltage from 24V to 26.4V. The rectified voltage (V rect-t ) is approximately 14.56V at no load (0A) and decreases to approximately 13.2V at 1.5A load current. This voltage is converted to 24V by DC / DC converter 214 connected to load 213.

[0242] 27A and 27B are graphs of the switch node voltage of amplifier 215 on PCB 602 under no-load and full-load conditions, respectively.

[0243] Although embodiments have been described above with reference to the figures, those skilled in the art will appreciate that changes and modifications can be made without departing from the scope of the disclosure and the claims that follow.

Claims

1. A bidirectional wireless power transfer system for transferring power, comprising: a transceiver element for transmitting power by generating an electric and / or magnetic field and for extracting power from the generated electric and / or magnetic field; a power stage electrically connected to the transceiver element for inverting an input power signal and for rectifying a received power signal; a trigger circuit for synchronizing wireless power transfer; a clock generator for generating a clock signal; a switching element electrically connected to the power stage and selectively electrically connected to the trigger circuit and the clock generator, whereby: the transceiver element is configured to transfer power by generating an electric and / or magnetic field when the switching element electrically connects the clock generator to the power stage; a switching element, the transceiver element configured to extract power from a generated electric field and / or a generated magnetic field when the switching element electrically connects the trigger circuit to the power stage; A system comprising:

2. The system of claim 1 , wherein the clock generator generates the clock signal to control the power stage.

3. The system of claim 1 or 2, wherein the power stage comprises an amplifier.

4. The system of claim 3 , wherein the amplifier is a class E power amplifier.

5. The system of claim 1 or 2, wherein the power stage comprises an input stage.

6. The system of claim 5 , wherein the input stage comprises a matching network.

7. The system of claim 6 , wherein the matching network comprises a single impedance inverter or a dual impedance inverter.

8. 3. The system of claim 1, wherein the power stage comprises a gate driver for controlling the power stage.

9. The system of claim 1 or 2, wherein the clock generator comprises an oscillator.

10. 3. The system of claim 1 or 2, wherein the trigger circuit is for controlling operation of the power stage to synchronize a power signal received by the transceiver element.

11. 3. The system of claim 1 or 2, wherein the trigger circuit comprises a sampling circuit for sampling a current or a voltage.

12. The system of claim 11 , wherein the sampling circuit is configured to sample a current or to sample a voltage.

13. The system of claim 12 , wherein the sampled current is load independent.

14. The system of claim 12 , wherein the voltage is load independent.

15. The system of claim 1 or 2, further comprising a converter for converting the voltage of the power signal.

16. 16. The system of claim 15, wherein the converter is a bidirectional buck-boost converter.

17. 1. A transmitter for wirelessly transmitting power by magnetic and / or electric field coupling, comprising: a first transceiver element for transmitting power by generating an electric field and / or a magnetic field and for extracting power from the generated electric field and / or the generated magnetic field; a first power stage electrically connected to the first transceiver element for inverting an incoming power signal in a forward power flow direction and for rectifying a received power signal in a reverse power flow direction; a first trigger circuit for synchronizing wireless power transmission; a first clock generator for generating a clock signal; a first switching element electrically connected to the first power stage and selectively electrically connected to the first trigger circuit and the first clock generator, whereby: the first transceiver element is configured to transfer power by generating an electric field and / or a magnetic field when the first switching element electrically connects the first clock generator to the first power stage; a first switching element configured to extract power from a generated electric field and / or a generated magnetic field when the first switching element electrically connects the first trigger circuit to the first power stage; and a transmitter comprising:

1. A receiver for wirelessly extracting power by magnetic or electric field coupling, comprising: a second transceiver element for transmitting power by generating an electric and / or magnetic field and for extracting power from the generated electric and / or magnetic field; a second power stage electrically connected to the second transceiver element for inverting an incoming power signal in the reverse power flow direction and for rectifying a received power signal in the forward power flow direction; a second trigger circuit for synchronizing the wireless power transfer; a second clock generator for generating a clock signal; a second switching element electrically connected to the second power stage and selectively electrically connected to the second trigger circuit and the second clock generator, whereby: the second transceiver element is configured to transfer power to the transmitter by generating an electric field and / or a magnetic field when the second switching element electrically connects the second clock generator to the second power stage; a second switching element configured to extract power from a generated electric field and / or a generated magnetic field from the transmitter when the second switching element electrically connects the second trigger circuit to the second power stage; and A receiver comprising: A wireless power transmission system comprising:

18. 1. A method of operating a bidirectional wireless power transfer system, the system comprising: a transceiver element for transmitting power by generating an electric and / or magnetic field and for extracting power from the generated electric and / or magnetic field; a power stage electrically connected to the transceiver element for inverting an input power signal and for rectifying a received power signal; a trigger circuit for synchronizing wireless power transfer; a clock generator for generating a clock signal; a switching element electrically connected to the power stage and selectively electrically connected to the trigger circuit and the clock generator, whereby: the transceiver element is configured to transfer power by generating an electric and / or magnetic field when the switching element electrically connects the clock generator to the power stage; a switching element, the transceiver element configured to extract power from a generated electric field and / or a generated magnetic field when the switching element electrically connects the trigger circuit to the power stage; Equipped with The method comprises: connecting the power stage to the trigger circuit to extract power; or connecting the power stage to the clock generator for transmitting power. A method comprising:

19. 20. The method of claim 18, wherein connecting the power stage to the trigger circuit or the clock generator comprises operating the switching element.

20. 20. The method of claim 18 or 19, further comprising the step of decoupling the power stage from the clock generator or decoupling the power stage from the trigger circuit.

21. 21. The method of claim 20, wherein decoupling the power stage from the trigger circuit or the clock generator comprises operating the switching element.

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