Shorting switch for reducing ground leakage current in inductive charging

Abstract

The present disclosure relates to a bidirectional shorting switch that can be used to short a resonant tank to reduce leakage current associated with a wireless charging pad configured for wireless power transmission. In some embodiments, the wireless charging pad includes a resonant tank and a bidirectional switch. The resonant tank has a first tank terminal and a second tank terminal, and the resonant tank includes a coil. The bidirectional switch has a first switch terminal and a second switch terminal. The first switch terminal is connected to the first tank terminal, and the second switch terminal is connected to the second tank terminal. The bidirectional switch is configured to reduce a common-mode voltage across the coil.

Description

[Technical Field]

[0001] [CROSS-REFERENCE TO RELATED APPLICATIONS] This application claims priority to U.S. Provisional Patent Application No. 63 / 48,7565, entitled "WIRELESS CHARGING CIRCUIT TOPOLOGY," filed February 28, 2023, and U.S. Provisional Patent Application No. 63 / 48,7559, entitled "SHORTING SWITCH TO REDUCE GROUND LEAKAGE CURRENT IN INDUCTIVE CHARGING," filed February 28, 2023, the disclosures of each of which are incorporated herein by reference in their entirety for all purposes.

[0002] FIELD OF THE DISCLOSURE The present disclosure relates to systems and methods for wireless charging. More particularly, embodiments of the present disclosure relate to wireless charging systems and mechanisms for charging vehicles. [Background technology]

[0003] Generally described, inductive charging, commonly referred to as wireless charging, is a type of wireless power transfer. Inductive charging uses electromagnetic induction to generate or supply electricity to a device without necessarily requiring a physical electrical connection. Specifically, various devices can be placed near a charging station or inductive pad, a physical dock, an electrical plug, etc., without precise alignment or electrical contact. Such devices may include, but are not limited to, vehicles, manufacturing equipment, home appliances, medical devices, etc. Summary of the Invention [Problem to be solved by the invention]

[0004] The systems, methods, and devices of the present disclosure each have several innovative embodiments, no single one of which alone is responsible for all of the desirable attributes disclosed herein. Details of one or more implementations of the subject matter described herein are set forth in the accompanying drawings and the description below.

[0005] In some aspects, the technology described herein relates to a wireless charging pad with reduced leakage current, the wireless charging pad including: a resonant tank having a first tank terminal and a second tank terminal, the resonant tank including a coil; and a bidirectional switch having a first switch terminal and a second switch terminal, the first switch terminal connected to the first tank terminal and the second switch terminal connected to the second tank terminal, the bidirectional switch configured to reduce a common mode voltage across the coil, and the wireless charging pad configured for wireless power transfer.

[0006] In some aspects, the technology described herein relates to a wireless charging pad, wherein a bidirectional switch includes a first transistor and a second transistor, the first transistor and the second transistor being connected back-to-back.

[0007] In some aspects, the technology described herein relates to a wireless charging pad, wherein the first transistor and the second transistor are field effect transistors (FETs), the drain of the first transistor is connected to a first switch terminal, the drain of the second transistor is connected to a second switch terminal, and the source of the first transistor and the source of the second transistor are connected to each other.

[0008] In some aspects, the technology described herein relates to a wireless charging pad further including an H-bridge circuit, wherein the first tank terminal and the first switch terminal are connected to a first switching node of the H-bridge circuit, and the second tank terminal and the second switch terminal are connected to a second switching node of the H-bridge circuit.

[0009] In some aspects, the technology described herein relates to a wireless charging pad further including a stacked half-bridge circuit, wherein a first tank terminal and a first switch terminal are connected to a first switching node of the stacked half-bridge circuit, and a second tank terminal and a second switch terminal are connected to a second switching node of the stacked half-bridge circuit.

[0010] In some aspects, the technology described herein relates to a wireless charging pad, wherein a stacked half-bridge circuit includes a first half-bridge including field effect transistors and a second half-bridge including field effect transistors.

[0011] In some aspects, the technology described herein relates to a wireless charging pad in which one field effect transistor of a first half bridge and one field effect transistor of a second half bridge are connected in series between a first switching node and a second switching node.

[0012] In some aspects, the technology described herein relates to a wireless charging pad in which a bidirectional switch includes two field effect transistors connected back to back.

[0013] In some aspects, the technology described herein relates to a wireless charging pad, wherein the bidirectional switch further includes a capacitor connected in series between the two field effect transistors.

[0014] In some aspects, the technology described herein relates to a wireless charging pad, wherein the coil is a segmented coil.

[0015] In some aspects, the technology described herein relates to a wireless charging pad, wherein the wireless charging pad is a vehicle pad that includes terminals configured to connect to a battery pack.

[0016] In some aspects, the technology described herein relates to a wireless charging pad, wherein the wireless charging pad is a grounding pad that includes an electrical connector configured to connect to a power source.

[0017] In some aspects, the technology described herein relates to a method of wireless power transfer with reduced leakage current, the method including energizing a ground pad and wirelessly transferring power from the ground pad to a vehicle pad of a vehicle, the vehicle including a battery pack and configured to charge the battery pack based on the wirelessly transferred power, and at least one of the vehicle pad or the ground pad including a bidirectional shorting switch across a resonant circuit.

[0018] In some aspects, the technology described herein relates to a method, wherein a bidirectional short-circuiting switch includes a first transistor and a second transistor, the first transistor and the second transistor being connected back-to-back.

[0019] In some aspects, the technology described herein relates to a method, wherein the bidirectional short-circuiting switch further includes a capacitor connected in series between the first transistor and the second transistor.

[0020] In some aspects, the technology described herein relates to a method, wherein the resonant circuit includes an induction coil and one or more resonant capacitors.

[0021] In some aspects, the technology described herein relates to a method, wherein a vehicle pad is configured to supply a voltage of up to 800 volts to a battery pack.

[0022] In some aspects, the technology described herein relates to a wireless charging converter that includes a first resonant tank including a first coil and a first electrical switch shunted across the first resonant tank, the first electrical switch configured to reduce a common-mode voltage across the first coil for wireless charging.

[0023] In some aspects, the technology described herein relates to a wireless charging converter further including a second resonant tank including a second coil, and a second electrical switch shunted to the second resonant tank, the second electrical switch configured to adjust a second common mode voltage on the second coil to charge a battery pack of a vehicle.

[0024] In some aspects, the technology described herein relates to a wireless charging converter in which a first resonant tank and a first electrical switch are in a vehicle pad attached to a vehicle, and a second resonant tank and a second electrical switch are in a ground pad connected to an energy source for charging a battery pack of the vehicle.

[0025] In some aspects, the technology described herein relates to a wireless charging converter in which a first electrical switch includes two field effect transistors (FETs) connected back to back.

[0026] In some aspects, the technology described herein relates to a wireless charging converter, wherein the second electrical switch includes two additional FETs and a capacitor connected in series between the two additional FETs.

[0027] In some aspects, the technology described herein relates to a wireless charging converter, wherein the second electrical switch includes two additional transistors connected back to back.

[0028] In some aspects, the technology described herein relates to a wireless charging system that includes a wireless charging pad. [Brief explanation of the drawings]

[0029] Throughout the drawings, reference numbers are reused to indicate correspondence between referenced elements. The drawings are provided to illustrate examples of the subject matter described herein, but not to limit the scope thereof.

[0030] Embodiments of the present disclosure will now be described with reference to the accompanying drawings, in which like reference numerals refer to like elements.

[0031] [Figure 1A] 1 illustrates an exemplary wireless charging environment in which embodiments of the present disclosure may be implemented.

[0032] [Figure 1B] FIG. 1B is a block diagram illustrating the example wireless charging environment of FIG. 1A, in accordance with some embodiments of the present disclosure.

[0033] [Figure 1C] FIG. 1 shows a block diagram of a ground pad that can function as a wireless charging device according to some embodiments of the present disclosure.

[0034] [Figure 2A] 1 illustrates an exemplary wireless charging system with an additional DC / DC converter.

[0035] [Figure 2B] 1 illustrates an exemplary wireless charging system with an additional DC / DC converter.

[0036] [Figure 3A] 1 illustrates an example circuit topology of a wireless charging converter according to some embodiments of the present disclosure.

[0037] [Figure 3B]1 illustrates an example circuit topology of a wireless charging converter according to some embodiments of the present disclosure.

[0038] [Figure 4A] 3B illustrates example waveforms illustrating the operation of the example circuit topology of FIG. 3A in accordance with some embodiments of the present disclosure.

[0039] [Figure 4B] 3C illustrates example waveforms illustrating the operation of the example circuit topology of FIG. 3B in accordance with some embodiments of the present disclosure.

[0040] [Figure 5A] 1 illustrates an example circuit topology including a bidirectional shorting switch, according to some embodiments of the present disclosure. [Figure 5B] 1 illustrates an example circuit topology including a bidirectional shorting switch, according to some embodiments of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0041] The following detailed description of certain embodiments presents various descriptions of specific embodiments. However, the novel ideas described herein may be embodied in many different ways, for example, as defined and covered by the claims. This description refers to the drawings, in which like reference numbers and / or terminology may indicate identical or functionally similar elements. It will be understood that the elements depicted in the drawings are not necessarily drawn to scale. It will also be understood that certain embodiments may include more elements and / or a subset of the elements depicted in the drawings. Furthermore, some embodiments may incorporate any suitable combination of features from two or more drawings. Headings are provided for convenience only and do not affect the scope or meaning of the claims.

[0042] A wireless charging device can be used to wirelessly charge vehicles, such as electric vehicles, that have a battery pack. The wireless charging device (e.g., a grounding pad) can wirelessly transmit (e.g., via induction) power received from an external source, such as a grid, solar cell(s), or the like, to the electric vehicle. The grounding pad can be placed under the vehicle pad of the electric vehicle to charge the electric vehicle. A wireless charging direct current (DC) / DC converter (also called an integrated DC / DC power converter) generally includes a DC / alternating current (AC) inverter inside the grounding pad and an AC / DC rectifier inside the vehicle pad. Power can be wirelessly transmitted from the grounding pad to the vehicle pad. The wireless charging disclosed herein can be applied to any suitable vehicle, including electric vehicles with battery packs and hybrid vehicles that include an internal combustion engine and a battery pack.

[0043] Generally described, one or more aspects of the present disclosure relate to systems and methods for wirelessly charging vehicle battery packs that can have a relatively wide range of battery voltages. Illustratively, aspects of the present disclosure relate to wireless charging circuits that are configurable to operate under various input and output voltages. In some embodiments, a wireless charging DC / DC converter can be configured at the topology level during manufacturing to set the converter voltage gain ratio for a particular vehicle pad. During manufacturing of vehicle pads with different battery packs, the same circuit elements can be connected differently by electrical connectors, such as jumper cables. These different vehicle pads can thus be combined with the same ground pad in a wireless charger to accommodate a wide battery voltage range or a wide range of battery load impedances without utilizing an additional DC / DC converter. More specifically, a wireless charging DC / DC converter that includes the same ground pad in a wireless charger can generate a wide range of output voltage levels at different vehicle pads to charge different battery packs with different nominal and / or maximum voltage ratings. For example, the wireless charging DC / DC converter can be configured to interface with a battery pack having a nominal and / or maximum voltage rating, including, but not limited to, 400 volts (V) or 800V.

[0044] In some embodiments, one or more bidirectional shorting switches can be incorporated into the wireless charging DC / DC converter. For example, the bidirectional shorting switch can be disposed on the vehicle side of the wireless charging DC / DC converter (e.g., inside the vehicle pad). As another example, the bidirectional shorting switch can be disposed on the ground side of the wireless charging DC / DC converter (e.g., inside the ground pad). In certain applications, there may be one bidirectional shorting switch on the vehicle side and another bidirectional shorting switch on the wireless charger side. The bidirectional shorting switch can provide an alternating current (AC) short circuit across the resonant tank. The one or more bidirectional shorting switches can maintain a substantially constant common-mode voltage on the ground pad coil and / or the vehicle pad coil. Thus, leakage currents associated with the wireless charging DC / DC converter can be reduced using the bidirectional shorting switch(es). This can reduce energy consumption and / or minimize conducted and radiated emissions.

[0045] In certain conventional designs, wireless charging systems typically include additional DC / DC converters before or after the wireless charging DC / DC converter to accommodate a wide battery voltage range and a wide battery load impedance range, as compared to the wireless charging system embodiments disclosed herein. For example, to charge a battery pack with a nominal voltage of 400 V and / or a maximum voltage of 800 V, one additional DC / DC converter may be used for just the converter including the vehicle pad and the ground pad. The additional DC / DC converter can expand the voltage gain range of the wireless charger. The additional DC / DC converter may be a buck converter and / or a boost converter between the battery module and the wireless power receiving device. Such an approach may involve extra costs for building the wireless charging system. Furthermore, the additional DC / DC converter may increase the weight of the wireless charging system. In addition, the deployment of an additional DC / DC converter between the battery module and the wireless power receiving device may result in energy loss.

[0046] To avoid an additional DC / DC converter, other wireless charging systems can utilize variations in the coil and resonant capacitor to support different battery charging voltages, however, variations in the coil and / or resonant capacitor introduce additional complexity into the supply chain and production management.

[0047] To address at least some of the above problems, a wireless charging DC / DC converter or its topology according to some embodiments of the present disclosure is disclosed. In some embodiments, the wireless charging DC / DC converter can be configured at the topology level (e.g., using jumpers) during manufacturing or assembly at a factory to set the converter voltage gain ratio, particularly the vehicle pad of the corresponding battery pack of the vehicle. Additionally, an active switch (e.g., a relay or semiconductor switch) can be provided on a PCB and operated (e.g., turned on or off) to reconfigure the wireless charging DC / DC converter in the field (e.g., outside the manufacturing or assembly factory). This can accommodate a wide battery voltage range or a wide range of battery load impedances for wireless charging with the same wireless charger along with various vehicle pads. For example, a vehicle pad can be configured during manufacturing by one or more jumpers installed on a printed circuit board (PCB) to set the circuit topology of the vehicle pad to achieve a desired battery pack voltage range (e.g., 200V to 800V) and / or a wide range of battery load impedances. Advantageously, based on embodiments of the present disclosure, a relatively wide battery pack voltage range can be achieved using ground pads and various vehicle pad topologies without using additional DC / DC converters. The same set of hardware (e.g., the same transistors, the same coils, the same resonant capacitors, etc.) can be configured into different circuit topologies for different battery packs to streamline the manufacturing process. For each circuit topology, the converter can provide further voltage regulation around its nominal voltage by applying control of one or more of the duty cycle, switching frequency, or phase shift between the primary and secondary sides.

[0048] In some embodiments, the disclosed wireless charging DC / DC converter employs the same coil and / or the same resonant capacitor to facilitate charging of batteries across different vehicle battery charging platforms. The wireless charging DC / DC converter may utilize the same PCB or a single PCB to match various input and / or output voltages specified by different battery pack charging platforms. The wireless charging DC / DC converter may be associated with different PCB assemblies (PCBA) to support different vehicle battery charging platforms. Advantageously, the hardware design complexity and cost of building a wireless charging system may be reduced by incorporating the disclosed wireless charging DC / DC converter into the wireless charging system.

[0049] In some embodiments, a bidirectional shorting switch can short out the resonant tank of the ground pad (e.g., a resonant capacitor in series with the ground pad coil) and / or the bidirectional shorting switch can short out the resonant tank of the vehicle pad (e.g., a resonant capacitor in series with the vehicle pad coil). The bidirectional shorting switch can establish a substantially constant common-mode voltage on the ground pad coil and / or the vehicle pad coil. Advantageously, leakage currents associated with the ground pad coil and / or the vehicle pad coil can be reduced by such a bidirectional shorting switch, thereby reducing energy consumption, minimizing conducted and radiated emissions, and / or making the wireless charging DC / DC converter more power efficient.

[0050] While various aspects are described according to exemplary embodiments and feature combinations, those skilled in the art will understand that the examples and feature combinations are exemplary in nature and should not be construed as limiting. More specifically, aspects of the present application may be applicable to various types of vehicle charging mechanisms, power sources, interfaces, etc. Furthermore, while schematic diagrams of particular DC / DC converters for charging batteries and / or battery packs under different voltage levels are described, such illustrative DC / DC converter schematic diagrams should not be construed as limiting. Accordingly, those skilled in the art will understand that aspects of the present application are not necessarily limited in application to any particular type of vehicle, vehicle charging infrastructure, data communications, or exemplary interactions between a vehicle, an owner / user, and a wireless battery charging system.

[0051] Wireless Charging Overview Generally described, inductive charging, commonly referred to as wireless charging, is a type of wireless power transfer. Inductive charging uses electromagnetic induction to generate or supply electricity to a device without the need for a physical electrical connection. Specifically, various devices can be placed near a charging station or inductive pad without precise alignment or electrical contact, or the need for a physical dock, electrical plug, or the like. Such devices include, but are not limited to, vehicles, manufacturing equipment, consumer electronics, medical devices, and the like.

[0052] According to aspects of the present application, an inductive charging system is configured to transfer energy through inductive coupling between components. An exemplary charging system includes a transmitting component, which may be configured as a charging station or charging pad. Alternating current (e.g., input current) from a power source passes through an induction coil within the charging station or charging pad. Based on the input current, charge moving through the induction coil (e.g., ground pad coil) generates (or induces) a magnetic field. Illustratively, the strength of the magnetic field may vary at least in part due to changes or fluctuations in the amplitude of the input current. The changing magnetic field generates an alternating current in the induction coil on the receiving device (e.g., vehicle pad coil). The induced alternating current within the receiving device may then pass through a rectifier, which converts the induced alternating current to direct current. Finally, the receiving vehicle may include additional charging components and / or systems that utilize the converted direct current to charge a battery system, provide operating power, or a combination thereof.

[0053] If an exemplary inductive charging system uses resonant inductive coupling components / techniques, a longer distance between the ground pad and the vehicle pad coil can be achieved. More specifically, in some embodiments, a capacitor can be connected to each inductive coil to create two LC circuits with specific resonant frequencies. The frequency of the alternating current is matched to the resonant frequencies. In addition, the matched frequencies can be further selected depending on the distance between the transmitting and receiving devices, taking peak efficiency into consideration. Furthermore, the use of other materials for the receiving coil, such as silver-plated copper or possibly aluminum to minimize weight and reduce resistance, can be utilized for energy transfer efficiency purposes.

[0054] FIG. 1A is an illustrative diagram of an environment 100 for implementing an inductive-based wireless charging system in accordance with various aspects of the present application. The environment 100 may illustratively correspond to a commercial implementation, such as a parking lot, parking space, or charging booth. The environment 100 may also correspond to a private or other non-commercial implementation, such as a private home. As an illustrative example, an implementation of an inductive-based wireless charging system in a non-commercial implementation may include a grounding pad 102 configured to generate a variable magnetic field according to an inductive charging methodology. As also shown in FIG. 1A , the grounding pad 102, which may also be referred to as a transmitting component, may correspond to a stand-alone component that may be operable to be mounted or positioned on a floor 104 or other flat surface. In some other embodiments, the grounding pad 102 may be integrated into or combined with other devices or components.

[0055] The grounding pad 102 may be connected to one or more power sources, such as input from a utility company, a real-time power source (e.g., a solar or wind energy source), a stored energy cell, or a combination thereof. The power source is configured to provide input AC current as described herein. The grounding pad 102 may be connected to the power source via a direct electrical connection 106, such as through a junction box 108 positioned on a wall surface 118.

[0056] 1A , in one embodiment, the grounding pad 102 corresponds to a form factor that enables positioning of the floor 104 for wireless charging with a vehicle having a vehicle pad coil. The grounding pad 102 may have a form factor such that the vehicle is positioned directly above the top surface of the grounding pad 102. Illustratively, the dimensions of the grounding pad 102 (e.g., the height and width of the grounding pad 102) may be configured such that the distance between the top surface of the grounding pad 102 and the underside of the vehicle meets certain criteria, such as a minimum distance between the grounding pad coil and the vehicle pad coil, a maximum distance between the grounding pad coil and the vehicle pad coil, etc. In some embodiments, the vehicle or the grounding pad 102 (or a combination thereof) may be configured with additional components to adjust (e.g., statically and / or dynamically adjust) such distance or otherwise change the relative orientation between the grounding pad 102 and the vehicle.

[0057] In some embodiments, the grounding pad 102 can be configured to charge a vehicle's battery pack, which can have a nominal voltage greater than 200 volts (e.g., a nominal voltage of approximately 350 volts or 355 volts) and a maximum voltage of 400 volts. In some embodiments, the grounding pad 102 can be configured to provide 800 volts of DC power. In some embodiments, the grounding pad 102 can provide a voltage in the range of approximately 200 volts to 800 volts.

[0058] 1B shows a block diagram of an environment 100 including a wireless charging device 111 (e.g., a grounding pad 102) that communicates wirelessly with a vehicle 112, such as via an induction-based magnetic field. The wireless charging device 111 is further connected to one or more energy sources 110. While the wireless charging device 111 is shown with a direct connection to the energy source 110, at least a portion of the input alternating currently can also be provided via wireless transmission methods. Additionally, in embodiments having multiple power sources, the environment can also include various switching components to allow energy selection from individual energy sources 110 or combinations of energy sources 110.

[0059] 1C shows a block diagram of a ground pad 102 that can function as the wireless charging device 111 (shown in FIG. 1B). The ground pad 102 can include at least a ground pad coil 122 for generating a magnetic field from an input current provided by the energy source 110. As shown in FIG. 1C, the input current can be provided by a direct electrical connection 106.

[0060] In some embodiments, the grounding pad 102 may also include various sensor components 124 related to the charging process. By way of example, the sensor components 124A, 124B, 124C, 124D may be configured for various functions such as vehicle 112 detection, object detection, vehicle distance measurement, environmental sensors (e.g., temperature sensors, moisture sensors), pressure sensors, etc. In one embodiment, the sensor components 124 may include radar sensors. The sensor components 124 may include logic and processing components related to the charging process, including operational measurements, operational control, safety measurements, communication components, and the like.

[0061] Wireless charging system having a wireless charging converter and a DC / DC converter 2A shows an exemplary wireless charging system 200A. As shown in FIG. 2A, the wireless charging system 200A includes a wireless charging DC / DC converter 202A and a DC / DC converter 204A. The DC / DC converter 204A is included on the vehicle side of the wireless charging system 200A (e.g., in a vehicle pad) and converts the output voltage from the DC converter 202A into a voltage for the vehicle's battery pack 206A. The battery pack 206A may be referred to as a battery coil. The DC / DC converter 204A allows the voltage level provided by the wireless charging DC / DC converter 202A to be adjusted to a voltage level specified for the battery pack 206A.

[0062] 2B illustrates an exemplary wireless charging system 200B. As shown in FIG. 2B, wireless charging system 200B includes a wireless charging DC / DC converter 202B and a DC / DC converter 204B. DC / DC converter 204B is included on the ground side (e.g., in the ground pad) of wireless charging system 200B and converts the output voltage from the DC / AC conversion stage to a voltage level such that wireless charging DC converter 202B provides the voltage specified by the vehicle's battery pack 206B.

[0063] The additional DC / DC converters 204A and / or 204B may be buck and / or boost converters, which may involve extra components and costs for the wireless charging system 200A or 200B. Furthermore, the DC / DC converters 204A and / or 204B may increase the weight of the wireless charging system 200A or 200B. Additionally, deploying the additional DC / DC converter 204A between the battery pack 206A and a portion of the vehicle-side wireless charging DC converter 202A may cause energy loss on the vehicle side.

[0064] Exemplary Wireless Charging System 3A-3B illustrate an example circuit topology 300A and an example circuit topology 300B for a wireless charging DC / DC converter, where the vehicle pad topology may be configurable during manufacturing based on a desired battery voltage range. More specifically, vehicle pads having circuit topologies 300A and 300B can be manufactured using the same coil (e.g., vehicle pad coil 330), transistors 360-364, and resonant capacitor 336, which may be configured during manufacturing of the vehicle pad. Such vehicle pads, combined with the same ground pad, can charge battery packs at different voltage ranges (e.g., maximum voltages of 400V and 800V). In some embodiments, the vehicle pad can be configured as either the vehicle pad of circuit topology 300A or circuit topology 300B by manipulating one or more connectors (e.g., jumpers) installed on the vehicle pad's printed circuit board (PCB). In other embodiments, instead of using jumpers, active switches (e.g., relays or semiconductor switches) can be deployed on the PCB and operated (e.g., turned on or off) to reconfigure the vehicle pads in the field (e.g., outside of a manufacturing or assembly factory) to switch between circuit topologies 300A and 300B. In addition to charging the battery pack at different nominal and / or maximum voltages, circuit topologies 300A and 300B can further provide voltage regulation around the nominal voltage through controlling one or more of the duty cycle, switching frequency, or phase shift associated with the vehicle pad-side and ground pad-side signals.

[0065] More specifically, FIG. 3A illustrates circuit topology 300A being utilized to charge battery pack 390A at a first voltage, and FIG. 3B illustrates circuit topology 300B being utilized to charge another battery pack 390B at a second voltage. The second voltage can be approximately twice the first voltage. For example, the first voltage can be up to 400V and the second voltage can be up to 800V. As shown in FIGS. 3A-3B, circuit topology 300A or circuit topology 300B includes at least ground pad coil 332, vehicle pad coil 330, and capacitors 336 and 334, respectively. In a wireless charging situation, the ground pad and vehicle pad need not be physically connected. Power may be supplied from a ground pad (e.g., ground pad 102 of FIG. 1A or wireless charging device 111 of FIG. 1B), and the supplied power may be wirelessly coupled to a vehicle pad (e.g., part of vehicle 112 of FIG. 1B) through operation of circuit topology 300A or circuit topology 300B. In some embodiments, power may be transferred wirelessly from the ground pad (connected to an energy source, such as energy source 110) to the vehicle pad through a link established between ground pad coil 332 on the ground pad and vehicle pad coil 330 on the vehicle pad.

[0066] As shown in FIG. 3A , power from the ground pad is converted by circuit topology 300A to charge battery pack 390A, which can be used to power a vehicle. The maximum voltage of battery pack 390A can be, for example, 400V. In some embodiments, although not explicitly shown in FIG. 3A , the voltage level of the energy source to which the ground pad is connected can output a DC voltage below the maximum voltage of battery pack 390A (e.g., 400V), which is then converted by circuit topology 300A to a voltage for charging battery pack 390A.

[0067] 3A, the ground pad includes transistors 350, 352, 354, and 356 arranged in an H-bridge topology. The ground pad also includes a capacitor 334 and a ground pad coil 332 arranged as a resonant tank. In addition, the ground pad may also include a capacitor 370. In circuit topology 300A, the vehicle pad includes a resonant tank including a vehicle pad coil 330, a capacitor 336, and transistors 360, 362, 364, and 366 arranged in an H-bridge circuit. The H-bridge circuit includes transistors 360, 362, 364, and 366, shown in parallel or shunt with a capacitor 380. The ground pad transistors 350, 352, 354, and 356 and the vehicle pad transistors 360, 362, 364, and 366 may be field effect transistors (FETs) as illustrated. For example, the transistors may be metal oxide semiconductor field effect transistors (MOSFETs), such as n-type MOSFETs and / or p-type MOSFETs. As shown, transistors 350-356 and 360-366 are n-type FETs.

[0068] FIG. 3B illustrates a wireless charging DC / DC converter configured in a different topology (e.g., circuit topology 300B) than the wireless charging DC / DC converter of FIG. 3A. Notably, the vehicle pad includes power electronics arranged differently in FIG. 3B and FIG. 3A. In other cases, the vehicle pads of circuit topologies 300A and 300B may include instances of the same components. During vehicle pad manufacture or assembly, these components may be arranged differently for the vehicle pads shown in FIG. 3A and FIG. 3B to provide different voltage conversion ratios. For example, the wireless charging converter with topology 300B shown in FIG. 3B may have approximately twice the voltage conversion ratio of the wireless converter with topology 300A shown in FIG. 3A. Circuit topology 300B may generate a DC voltage that is approximately twice as high as that of circuit topology 300A.

[0069] As shown in FIG. 3B, transistors 360, 362, 364, and 366 of the vehicle pad are arranged as a stacked half bridge. A stacked half bridge includes two half bridges arranged in series with each other. A first half bridge (e.g., including transistors 360 and 362) of the vehicle pad of FIG. 3B is arranged similarly to one of the half bridges in the vehicle pad of FIG. 3A. The first half bridge is in parallel with capacitor 380, as shown in FIG. 3B. A second half bridge (e.g., including transistors 364 and 366) of the vehicle pad of FIG. 3B is arranged in series with the first half bridge between the HV-MID node and the HV- node. The second half bridge is in parallel with capacitor 382, ​​as shown in FIG. 3B.

[0070] The voltage pads of circuit topology 300B can be used in a vehicle having a battery pack 390B with a higher voltage specification than a vehicle having battery pack 390A of circuit topology 300A. As an example, the vehicle pads of circuit topology 300B can be used in a vehicle having a maximum battery pack voltage of 800V, and the vehicle pads of circuit topology 300A can be used in a vehicle having a maximum battery pack voltage of 400V.

[0071] The hardware components associated with the ground pads and vehicle pads (e.g., transistors 360, 362, 364, and 366, capacitor 336, vehicle pad coil 330, ground pad coil 332, capacitor 334, transistors 350, 352, 354, and 356) may be the same as those shown in FIG. 3A. In some cases, the transistors (e.g., transistors 360, 362, 364, and 366) of the vehicle pads of FIGS. 3A and 3B may be 650V MOSFETs. The vehicle pad coil 330, ground pad coil 332, capacitors 336, 334, and 370 in the ground pads and vehicle pads of FIGS. 3B and 3A may also be the same. Furthermore, in FIG. 3B, the energy source to which the ground pads are connected may output the same DC voltage as in FIG. 3A. In some other embodiments, the ground pads of FIGS. 3A-3B may be connected to different types of energy sources that provide different levels of input voltage to circuit topologies 300A and 300B.

[0072] In some embodiments, the vehicle pad is configured during manufacture to provide a desired conversion ratio between the ground pad coil 332 on the ground pad and the vehicle pad coil 330 on the vehicle pad by connecting (and / or disconnecting) power electronics components on the vehicle pad's PCB using jumpers or any other suitable electrical connectors. For example, jumpers may be attached to a PCB associated with the vehicle pad to connect two points on the PCB to configure the wireless charging DC / DC converter from a first conversion ratio (e.g., 16) to a second conversion ratio (e.g., 32). As another example, jumpers attached to the PCB may be removed from the PCB to configure the wireless charging DC / DC converter to provide different conversion ratios based on different battery charging voltages specified by different batteries. In some embodiments, different forms of jumpers and / or connectors (e.g., jumper wires) may be utilized to configure the wireless charging DC / DC converter into circuit topologies different from circuit topology 300A and circuit topology 300B to achieve different levels of input and output voltages.

[0073] In circuit topologies 300A and 300B, the half bridge connected to the negative tank node 304A or 304B (e.g., HVTANK−) is connected to a different node. In particular, the half bridge including transistors 364 and 366 connected to the negative tank node 304A in the vehicle pad of FIG. 3A is connected between node HV+ and node HV-MID. In contrast, the half bridge including transistors 364 and 366 connected to the negative tank node 304B in the vehicle pad of FIG. 3B is connected between node HV-MID and node HV−. During manufacturing, the half bridge including transistors 364 and 366 can be connected as shown in FIG. 3A or as shown in FIG. 3B. This can include connecting the half bridge using jumpers. In certain applications, the vehicle pad can be pre-configured as shown in FIG. 3A or as shown in FIG. 3B, with the half bridge adjusted to a different configuration as desired during manufacturing.

[0074] Advantageously, by using instances of the same hardware (e.g., same transistors, same coils, same capacitors) for vehicle pads with different conversion ratios while utilizing PCB connectors, the cost to build a vehicle pad and / or wireless charging system can be reduced. Additionally, the vehicle pad and / or wireless charging system can be lighter because less hardware is required to charge different battery packs. Furthermore, the complexity of designing a wireless charging system to meet different input and output voltage specifications can be reduced by using the same coils and capacitors in wireless charging DC / DC converters with different conversion ratios.

[0075] 4A-4B show example waveforms 400A and 400B illustrating the operation of circuit topology 300A and circuit topology 300B according to some embodiments of the present disclosure. Waveforms 400A and 400B are generated based on synchronous rectification operation on the vehicle pad side. The vehicle pad can be configured during manufacturing and used with a ground pad to represent one of waveforms 400A and 400B to provide various voltages (e.g., 400V and 800V) for charging various battery packs. Advantageously, the same set of hardware (e.g., coils, transistors, resonant capacitors, etc.) deployed in the various circuit topologies can provide a wide range of various battery voltages without an additional DC / DC converter, unlike wireless charging system 200A and wireless charging system 200B.

[0076] Figure 4A shows example waveforms illustrating the operation of circuit topology 300A of Figure 3A. As shown in Figure 4A, the voltage between positive tank node 302A (e.g., HVTANK+) and negative tank node 304A (e.g., HVTANK-) has a maximum voltage of 400V and a minimum voltage of -400V. Circuit topology 300A can be utilized to charge a 400V battery pack.

[0077] Figure 4B shows example waveforms illustrating the operation of circuit topology 300B of Figure 3B. As shown in Figure 4A, the voltage between positive tank node 302B (e.g., HVTANK+) and negative tank node 304B has a voltage swing of 800V, with a maximum voltage of 800V and a minimum voltage of 0V. Circuit topology 300B can be utilized to charge an 800V battery pack.

[0078] Exemplary Bidirectional Shorting Switch During operation of a wireless charging converter (e.g., a DC / DC converter including circuit topology 300A or circuit topology 300B), leakage current may be generated across the ground pad coil 332 and / or the vehicle pad coil 330. For example, the ground pad coil 332 of FIG. 3A may generate a leakage current associated with the ground pad. This leakage current may flow through a parasitic capacitor (not shown in FIG. 3A) to a heat sink (not shown in FIG. 3A) associated with circuit topology 300A. As another example, the vehicle pad coil 330 of FIG. 3A may generate a leakage current associated with the vehicle pad. This leakage current may flow through a parasitic capacitor (not shown in FIG. 3A) to a heat sink (not shown in FIG. 3A) associated with circuit topology 300A. More specifically, when the vehicle pad coil 330 is operating, a common-mode voltage amplitude may appear across nodes 302A and 304A. The common mode voltage swing across the vehicle pad coil 330 may cause leakage current to flow through the vehicle pad coil 330 .

[0079] To reduce leakage current, one or more bidirectional shorting switches can be included in the wireless charging DC / DC converter. For example, one or more bidirectional shorting switches can be added to circuit topology 300A and / or circuit topology 300B, respectively, to achieve the circuit topologies shown in FIGS. 5A-5B. The one or more bidirectional shorting switches can reduce leakage current flowing to the heat sink(s) through parasitic capacitance associated with circuit topology 300A and / or circuit topology 300B. As described above, leakage current can be generated by vehicle pad coil 330 and / or ground pad coil 332 (e.g., due to common-mode voltage amplitude resulting from operation of circuit topology 300A or circuit topology 300B). The one or more bidirectional shorting switches can block or reduce the common-mode voltage amplitude so that a constant or relatively constant common-mode voltage can be reached between the vehicle pad coil 330 and the ground pad coil 332, thereby reducing leakage current. With a bidirectional shorting switch, current can flow in either direction across the bidirectional shorting switch.

[0080] Advantageously, by reducing leakage current, less energy may be consumed than circuit topologies 300 A and 300 B. Additionally, conducted and radiated emissions may also be reduced or minimized.

[0081] 5A-5B show example circuit topologies 500A and 500B of a wireless charging DC / DC converter. Circuit topology 500A is similar to circuit topology 300A of FIG. 3A except that a bidirectional short-circuit switch is included in circuit topology 500A. Circuit topology 500A may function the same as or similar to circuit topology 300A except for the function provided by the bidirectional short-circuit switch (e.g., reducing leakage current through a reduction in common-mode voltage swing). Circuit topology 500B is similar to circuit topology 300B of FIG. 3B except that a bidirectional short-circuit switch is included in circuit topology 500B. Circuit topology 500B may function the same as or similar to circuit topology 300B except for the function provided by the bidirectional short-circuit switch (e.g., reducing leakage current through a reduction in common-mode voltage swing).

[0082] As shown in FIG. 5A, a bidirectional shorting switch 522A is shunted across the vehicle pad coil 330, and a bidirectional shorting switch 524 is shunted across the ground pad coil 332. Circuit topology 500A represents an H-bridge converter topology with a bidirectional shorting switch. With an H-bridge converter, the bidirectional shorting switch 524 can be coupled between switching nodes 552 and 554, thereby providing a shunt path for applying zero voltage across the resonant tank. The resonant tank can include the ground pad coil 332 and a capacitor 334, as shown in FIG. 5A. The bidirectional shorting switch 524 can achieve a constant common-mode voltage on the ground pad coil 332, thereby reducing leakage current across the resonant tank, including the ground pad coil 332.

[0083] Similarly, a bidirectional shorting switch 522A for reducing ground current leakage current can be implemented on the vehicle pad of circuit topology 500A. The vehicle-side battery pack can have a relatively high voltage, such as a maximum voltage of 400 volts. The bidirectional shorting switch 522A can be coupled between switching node 502A and switching node 504A, thereby achieving a nearly constant common-mode voltage across vehicle pad coil 330 and reducing leakage current.

[0084] As shown in FIG. 5A , each of the bidirectional short-circuiting switches 522A and 524 can include at least two field-effect transistors (FETs), such as MOSFETs, connected in series back to back. The bidirectional short-circuiting switches 522A and 524 are illustrated as including two FETs arranged in series between two nodes whose sources are connected to each other. Thus, the bidirectional short-circuiting switch 522A can reduce or eliminate a voltage swing of both polarities between the node 502A and the node 504A (i.e., a positive voltage swing between the node 502A and the node 504A and a negative voltage swing between the node 502A and the node 504A). Alternatively, the bidirectional short-circuiting switch can include two FETs arranged in series between two nodes whose drains are connected to each other. The bidirectional short-circuiting switches 522A and 524 can include n-type transistors as shown. In some other examples, the bidirectional short-circuiting switches 522A and 524 can include p-type transistors. The bidirectional shorting switch 524 can reduce or eliminate voltage swings of both polarities between the nodes 552 and 554 (i.e., positive voltage swings between the nodes 552 and 554 and negative voltage swings between the nodes 552 and 554). In some embodiments, when the bidirectional shorting switches 522A and 524 are closed, current can flow in either direction across the bidirectional shorting switches 522A and 524, and when the bidirectional shorting switches 522A and 524 are open, current can be blocked in either direction across the bidirectional shorting switches 522A and 524.

[0085] As shown in FIG. 5B, a bidirectional shorting switch 522B is shunted across the resonant tank including the vehicle pad coil 330, and a bidirectional shorting switch 524 is shunted across the resonant tank including the ground pad coil 332. The bidirectional shorting switch 524 can be coupled between switching nodes 552 and 554, thereby providing a shunt path for applying zero voltage across the resonant tank. The resonant tank can include the ground pad coil 332 and a capacitor 334, as shown in FIG. 5B. The bidirectional shorting switch 524 can achieve a constant common-mode voltage on the ground pad coil 332.

[0086] Similarly, a bidirectional shorting switch 522B for ground current leakage current reduction can be implemented on the vehicle side of circuit topology 500B. The vehicle-side battery pack can have a relatively high voltage, such as a maximum voltage of 800 volts. The bidirectional shorting switch 522B can be coupled between switching node 502B and switching node 504B, thereby achieving a constant common-mode voltage across vehicle pad coil 330 and reducing leakage current.

[0087] 5B, each of the bidirectional short-circuiting switch 522B and the bidirectional short-circuiting switch 524 may include at least two field-effect transistors (FETs), such as MOSFETs, connected in series back to back. Thus, the bidirectional short-circuiting switch 522B can reduce or eliminate a voltage swing of both polarities between the nodes 502B and 504B (i.e., a positive voltage swing between the nodes 502B and 504B and a negative Bollard voltage swing between the nodes 502B and 504B). The bidirectional short-circuiting switch 524 can reduce or eliminate a voltage swing of both polarities between the nodes 552 and 554 (i.e., a positive voltage swing between the nodes 552 and 554 and a negative Bollard voltage swing between the nodes 552 and 554).

[0088] 5B, the vehicle-side circuit topology 500B represents a stacked half-bridge including two half-bridges in series with each other (e.g., four FETs stacked in series). A flying capacitor 560B can be connected in series between the two FETs in the bidirectional shorting switch 522B, thereby providing a shunt path that applies half of the direct current (DC) bus voltage onto a resonant tank that is decoupled from the DC bus to achieve a constant common-mode voltage across the vehicle pad coil 330. In some other embodiments, a stacked half-bridge topology with a flying capacitor can be implemented on the ground side.

[0089] The bidirectional shorting switch disclosed herein can reduce inductive charging ground leakage current in any of the wireless charging pads disclosed herein. A bidirectional switch connected between the switching nodes can be used to short out the resonant tank, so that the common-mode voltage on the coil is relatively constant and stable. The bidirectional shorting switch can be implemented in any of the vehicle pads and / or any of the ground pads disclosed herein.

[0090] The wireless charging circuits disclosed herein can be implemented using one or more bidirectional switches and / or one or more other techniques to reduce charging ground leakage current. Such other techniques include, but are not limited to, (1) a segmented coil to serialize multiple LC resonators and reduce the common-mode voltage on the coil, and (2) additional on-board and off-board DC / DC converters to avoid duty cycle control of the wireless power transfer power stage and thus reduce the common-mode voltage on the coil. For example, any of the coils disclosed herein can be a segmented coil to serialize multiple LC resonators. Such a segmented coil can be implemented in any of the wireless charging pads disclosed herein, such as the ground pad and / or vehicle pad of any of FIGS. 3A, 3B, 5A, and / or 5B.

[0091] conclusion The foregoing disclosure is not intended to limit the present disclosure to the precise form or particular field of use disclosed. Accordingly, various alternative embodiments and / or modifications to the present disclosure, whether expressly described or implied herein, are contemplated in light of the present disclosure. While embodiments of the present disclosure have been described in this manner, those skilled in the art will recognize that changes can be made in form and detail without departing from the scope of the present disclosure. Accordingly, the present disclosure is limited only by the claims.

[0092] It should be understood that not necessarily all objectives or advantages may be achieved in accordance with any particular embodiment described herein. Thus, for example, those skilled in the art will recognize that some embodiments may operate in a manner that achieves or optimizes one advantage or group of advantages as taught herein, without necessarily achieving other objectives or advantages that may be taught or suggested herein.

[0093] All of the processes described herein may be embodied in software code modules executed by a computing system including a computer or processor, and thereby fully automated. The code modules may be stored in any type of non-transitory computer-readable medium or other computer storage device. Some or all of the methods may be embodied in dedicated computer hardware.

[0094] Many variations beyond those described herein will be apparent from this disclosure. For example, depending on the embodiment, some operations, events, or functions of any of the algorithms described herein may be performed in a different order, or may be added, merged, or entirely omitted (e.g., not all described operations or events may be necessary to practice the algorithm). Furthermore, in some embodiments, operations or events may be performed in parallel rather than sequentially, for example, through multithreading, interrupt processing, or multiple processors or processor cores, or on other parallel architectures. Additionally, different tasks or processes may be performed by different machines and / or computing systems that can function together.

[0095] The various illustrative logic blocks and modules described in connection with the embodiments disclosed herein may be implemented or performed by a machine, such as a processing unit or processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof, designed to perform the functions described herein. The processor may be a microprocessor, but in alternative examples, the processor may be a controller, microcontroller, or state machine, combinations thereof, etc. A processor may include electrical circuitry that processes computer-executable instructions. In some embodiments, a processor includes an FPGA or other programmable device that performs logical operations without processing computer-executable instructions. A processor may also be implemented as a combination of computing devices, such as, for example, a combination of a DSP and a microprocessor, multiple microprocessors, a microprocessor in combination with a DSP core, or any other such configuration. Although described herein primarily with reference to digital technology, a processor may also include primarily analog components. The computing environment may include any type of computer system, including, but not limited to, a computer system based on a computational engine within a microprocessor, mainframe computer, digital signal processor, portable computing device, device controller, or appliance, to name a few.

[0096] Elements of a method, process, routine, or algorithm described in connection with the embodiments disclosed herein may be embodied directly in hardware, in a software module executed by a processor device, or in a combination of the two. A software module may reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, a hard disk, a removable disk, a CD-ROM, or any other form of non-transitory computer-readable storage medium. An exemplary storage medium may be coupled to the processor device such that the processor device can read information from, and write information to, the storage medium. Alternatively, the storage medium may be integral to the processor device. The processor device and the storage medium may reside in an ASIC. The ASIC may reside in a user terminal. Alternatively, the processor device and the storage medium may reside as discrete components in a user terminal.

[0097] The processes described herein or illustrated in the figures of this disclosure may be initiated in response to an event, such as a predetermined or dynamically determined schedule, on demand when initiated by a user or system administrator, or in response to some other event. When such processes are initiated, a set of executable program instructions stored on one or more non-transitory computer-readable media (e.g., hard drives, flash memory, removable media, etc.) may be loaded into memory (e.g., RAM) of a server or other computing device. The executable instructions may then be executed by a hardware-based computer processor of the computing device. In some embodiments, such processes, or portions thereof, may be implemented on multiple computing devices and / or multiple processors, either serially or in parallel.

[0098] Unless otherwise specified or understood within the context of use, conditional language such as "can," "could," "might," or "may," among others, is generally used to suggest that some embodiments include certain features, elements, and / or steps, while other embodiments do not. Thus, such conditional language is not generally intended to imply that features, elements, and / or steps are in any way part of an embodiment, or that an embodiment necessarily includes logic for determining whether or not those features, elements, and / or steps are included or performed in any particular embodiment, with or without user input or a request for input.

[0099] Disjunctive language such as the phrase "at least one of X, Y, or Z" is generally understood to be used to indicate that an item, term, etc. can be either X, Y, or Z, or any combination thereof (e.g., X, Y, and / or Z), unless otherwise indicated from context. Thus, such disjunctive language is generally not intended to, and should not, imply that some embodiments require at least one of X, at least one of Y, or at least one of Z, respectively, to be present.

[0100] Any process descriptions, elements, or blocks in the flow diagrams described herein and / or depicted in the accompanying drawings should also be understood as potentially representing modules, segments, or portions of code, including executable instructions for implementing specific logical functions or elements in the process. The scope of the embodiments described herein includes alternative embodiments in which elements or functions may be omitted, performed in a different order than shown or described, or performed substantially simultaneously or in the reverse order, depending on the functionality involved, as can be understood by one of ordinary skill in the art.

[0101] It should be emphasized that many variations and modifications can be made to the above examples, and that the elements thereof should be understood to be among other acceptable embodiments, and all such modifications and variations are intended to be included herein within the scope of this disclosure.

[0102] Any process descriptions, elements, or blocks in the flow diagrams described herein and / or depicted in the accompanying drawings should also be understood as potentially representing modules, segments, or portions of code that contain executable instructions for implementing specific logical functions or elements in the process. The scope of the embodiments described herein includes alternative implementations in which elements or functions may be omitted, performed in a different order than shown or described, or performed substantially simultaneously or in the reverse order, depending on the functionality involved, as can be understood by one of ordinary skill in the art.

[0103] Unless otherwise specified, articles such as "a" or "an" should be construed generally to include one or more described items. Thus, phrases such as "a device configured to" are intended to include one or more listed devices. Such one or more listed devices may also be collectively configured to perform the stated list. For example, "a processor configured to perform list A, B, and C" may include a first processor configured to perform list A working in conjunction with a second processor configured to perform list B and C.

Claims

1. A wireless charging pad with reduced leakage current, a resonant tank having a first tank terminal and a second tank terminal, the resonant tank comprising a coil; a bidirectional switch having a first switch terminal and a second switch terminal, the first switch terminal connected to the first tank terminal and the second switch terminal connected to the second tank terminal; Equipped with the bidirectional switch is configured to reduce a common-mode voltage across the coil; the wireless charging pad is configured for wireless power transfer; Wireless charging pad.

2. 2. The wireless charging pad of claim 1, wherein the bidirectional switch comprises a first transistor and a second transistor, the first transistor and the second transistor being connected back to back.

3. 3. The wireless charging pad of claim 2, wherein the first transistor and the second transistor are field effect transistors (FETs), a drain of the first transistor is connected to the first switch terminal, a drain of the second transistor is connected to the second switch terminal, and a source of the first transistor and a source of the second transistor are connected to each other.

4. 2. The wireless charging pad of claim 1, further comprising an H-bridge circuit, wherein the first tank terminal and the first switch terminal are connected to a first switching node of the H-bridge circuit, and the second tank terminal and the second switch terminal are connected to a second switching node of the H-bridge circuit.

5. 2. The wireless charging pad of claim 1, further comprising a stacked half-bridge circuit, wherein the first tank terminal and the first switch terminal are connected to a first switching node of the stacked half-bridge circuit, and the second tank terminal and the second switch terminal are connected to a second switching node of the stacked half-bridge circuit.

6. 6. The wireless charging pad of claim 5, wherein the stacked half-bridge circuit comprises a first half-bridge comprising a field effect transistor and a second half-bridge comprising a field effect transistor.

7. 7. The wireless charging pad of claim 6, wherein one field effect transistor of the first half bridge and one field effect transistor of the second half bridge are connected in series between the first switching node and the second switching node.

8. 10. The wireless charging pad of claim 1, wherein the bidirectional switch comprises two field effect transistors connected back to back.

9. The wireless charging pad of claim 8 , wherein the bidirectional switch further comprises a capacitor connected in series between the two field effect transistors.

10. The wireless charging pad of claim 1 , wherein the coil is a segmented coil.

11. 10. The wireless charging pad of claim 1, wherein the wireless charging pad is a vehicle pad including terminals configured to connect to a battery pack.

12. 10. The wireless charging pad of claim 1, wherein the wireless charging pad is a grounding pad including an electrical connector configured to connect to a power source.

13. A method for wireless power transmission with reduced leakage current, comprising: energizing the ground pad; wirelessly transmitting power from the ground pad to a vehicle pad of a vehicle; Including, the vehicle includes a battery pack and is configured to charge the battery pack based on the wirelessly transmitted power; At least one of the vehicle pad or the ground pad comprises a bidirectional shorting switch across a resonant circuit; method.

14. 14. The method of claim 13, wherein the bidirectional shorting switch comprises a first transistor and a second transistor, the first transistor and the second transistor being connected back-to-back.

15. 15. The method of claim 14, wherein the bidirectional shorting switch further comprises a capacitor connected in series between the first transistor and the second transistor.

16. The method of claim 13 , wherein the resonant circuit comprises an induction coil and one or more resonant capacitors.

17. The method of claim 13 , wherein the vehicle pad is configured to supply a voltage of up to 800 volts to the battery pack.

18. a first resonant tank comprising a first coil; a first electrical switch shunted across the first resonant tank; Equipped with the first electrical switch is configured to reduce a common mode voltage across the first coil for wireless charging; Wireless charging converter.

19. a second resonant tank comprising a second coil; a second electrical switch shunted to the second resonant tank; Further provided with the second electrical switch is configured to adjust a second common mode voltage on the second coil to charge a vehicle battery pack; 20. The wireless charging converter of claim 18.

20. 20. The wireless charging converter of claim 19, wherein the first resonant tank and the first electrical switch are in a vehicle pad attached to the vehicle, and the second resonant tank and the second electrical switch are in a ground pad connected to an energy source for charging the battery pack of the vehicle.

21. 20. The wireless charging converter of claim 19, wherein the first electrical switch comprises two field effect transistors (FETs) connected back to back.

22. 22. The wireless charging converter of claim 21, wherein the second electrical switch comprises two additional FETs and a capacitor connected in series between the two additional FETs.

23. 20. The wireless charging converter of claim 19, wherein the second electrical switch comprises two additional transistors connected back to back.

24. A wireless charging system comprising the wireless charging pad according to claim 1.

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