Short circuit 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-circuit a resonant tank to reduce leakage current associated with a wireless charging pad configured for wireless power transfer. In some embodiments, the wireless charging pad includes a resonant tank and a bidirectional switch. The resonant tank has a first loop terminal and a second loop 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 loop terminal and the second switch terminal is connected to the second loop terminal. The bidirectional switch is configured to cause a common mode voltage across the coil to be reduced.

Description

[0001] Cross Reference to Related Applications

[0002] This application claims priority to U.S. Provisional Patent Application No. 63 / 48,7565, filed February 28, 2023, entitled “WIRELESS CHARGING CIRCUIT TOPOLOGY,” and U.S. Provisional Patent Application No. 63 / 48,7559, filed February 28, 2023, entitled “SHORTING SWITCH TO REDUCE GROUND LEAKAGE CURRENT IN INDUCTIVE CHARGING,” the respective disclosures of which are incorporated herein by reference in their entirety and for all purposes. TECHNICAL FIELD

[0003] The present disclosure relates to systems and methods for wireless charging. More specifically, embodiments of the present disclosure relate to wireless charging systems and mechanisms for charging vehicles. BACKGROUND

[0004] Generally, inductive charging, often referred to as wireless charging, is a form of wireless power transfer. Inductive charging uses electromagnetic induction to generate or otherwise provide power to a device without the need for physical electrical connectivity. Specifically, a variety of devices can be placed near a charging station or inductive pad without the need for precise alignment or making electrical contact, physical docking, electrical plug-in, etc. Such devices can include, but are not limited to, vehicles, manufacturing equipment, consumer electronics, medical devices, etc. SUMMARY

[0005] The systems, methods, and devices of the application each have several innovative aspects, no single one of which is solely responsible for the overall desirable attributes of the application disclosed herein. The one or more implementations of the subject matter described in this specification exploit at least the following benefits.

[0006] In some aspects, the technology described herein relates to a wireless charging pad having reduced leakage current, the wireless charging pad comprising: a resonant tank having a first tank terminal and a second tank terminal, the resonant tank comprising 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, wherein the bidirectional switch is configured to cause a common mode voltage across the coil to be reduced, and wherein the wireless charging pad is configured for wireless power transfer.

[0007] In some aspects, the technology described herein relates to a wireless charging pad, wherein the bidirectional switch comprises a first transistor and a second transistor, wherein the first transistor and the second transistor are connected back-to-back

[0008] 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), wherein the drain of the first transistor is connected to the first switch terminal, wherein the drain of the second transistor is connected to the second switch terminal, and wherein the source of the first transistor and the source of the second transistor are connected to each other.

[0009] In some aspects, the technology described herein relates to a wireless charging pad, further comprising an H-bridge circuit, wherein the first return terminal and the first switch terminal are connected to a first switch node of the H-bridge circuit, and wherein the second return terminal and the second switch terminal are connected to a second switch node of the H-bridge circuit.

[0010] In some aspects, the technology described herein relates to a wireless charging pad, further comprising a stacked half-bridge circuit, wherein the first return terminal and the first switch terminal are connected to a first switch node of the stacked half-bridge circuit, and wherein the second return terminal and the second switch terminal are connected to a second switch node of the stacked half-bridge circuit.

[0011] In some aspects, the technology described herein relates to a wireless charging pad, wherein the stacked half-bridge circuit comprises a first half-bridge and a second half-bridge, the first half-bridge comprising a field effect transistor, the second half-bridge comprising a field effect transistor.

[0012] In some aspects, the technology described herein relates to a wireless charging pad, 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 switch node and the second switch node.

[0013] In some aspects, the technology described herein relates to a wireless charging pad, wherein the bidirectional switch comprises two field effect transistors connected back-to-back.

[0014] In some aspects, the technology described herein relates to a wireless charging pad, wherein the bidirectional switch further comprises a capacitor connected in series between the two field effect transistors.

[0015] In some aspects, the technology described herein relates to a wireless charging pad, wherein the coil is a segmented coil.

[0016] In some aspects, the technology described herein relates to a wireless charging pad, wherein the wireless charging pad is a vehicle pad, the vehicle pad comprising a terminal configured to be connected to a battery pack.

[0017] In some aspects, the technology described herein relates to a wireless charging pad, wherein the wireless charging pad is a ground pad, the ground pad comprising an electrical connector configured to be connected to a power source.

[0018] In some aspects, the technology described herein relates to a method of wireless power transfer with reduced leakage current, the method comprising: energizing a ground pad; and wirelessly transferring power from the ground pad to a vehicle pad of a vehicle, wherein the vehicle comprises a battery pack, and the vehicle is configured to charge the battery pack based on the wirelessly transferred power, and wherein at least one of the vehicle pad or the ground pad comprises a bidirectional shorting switch across a resonant circuit.

[0019] In some aspects, the technology described herein relates to a method, wherein the bidirectional shorting switch comprises a first transistor and a second transistor, wherein the first transistor and the second transistor are connected back-to-back.

[0020] In some aspects, the technology described herein relates to a method, wherein the bidirectional shorting switch further comprises a capacitor connected in series between the first transistor and the second transistor.

[0021] In some aspects, the technology described herein relates to a method, wherein the resonant circuit comprises an inductive coil and one or more resonant capacitors.

[0022] In some aspects, the technology described herein relates to a method, wherein the vehicle pad is configured to provide a voltage of up to 800 volts to the battery pack.

[0023] In some aspects, the technology described herein relates to a wireless charging converter, comprising: a first resonant tank comprising a first coil; and a first electrical switch shunted across the first resonant tank, wherein the first electrical switch is configured to cause a common mode voltage across the first coil to be reduced for wireless charging.

[0024] In some aspects, the technology described herein relates to a wireless charging converter, further comprising: a second resonant tank comprising a second coil; and a second electrical switch shunted to the second resonant tank, wherein the second electrical switch is configured to adjust a second common mode voltage on the second coil for charging a battery pack of a vehicle.

[0025] In some aspects, the technology described herein relates to a wireless charging converter, wherein the first resonant tank and the first electrical switch are in a vehicle pad attached to the vehicle, and wherein the second resonant tank and the second electrical switch are in a ground pad connected to a source of energy for charging the battery pack of the vehicle.

[0026] In some aspects, the technology described herein relates to a wireless charging converter, wherein the first electrical switch comprises two field effect transistors (FETs) connected back-to-back.

[0027] In some aspects, the technology described herein relates to a wireless charging converter, wherein the second electrical switch comprises two additional FETs and a capacitor connected in series between the two additional FETs.

[0028] In some aspects, the technology described herein relates to a wireless charging converter, where the second electrical switch includes two additional transistors connected back-to-back.

[0029] In some aspects, the technology described herein relates to a wireless charging system including a wireless charging pad. BRIEF DESCRIPTION OF DRAWINGS

[0030] Throughout the drawings, reference numbers are re-used to indicate correspondence between referenced elements wherever possible. The drawings are provided to illustrate examples of the subject matter described herein and not to limit the scope thereof.

[0031] Embodiments of the disclosure are described with reference to the accompanying drawings, wherein like reference numerals are used to indicate like elements, and wherein:

[0032] Figure 1A An example wireless charging environment in which embodiments of the disclosure can be implemented is shown.

[0033] Figure 1B is a block diagram illustrating an example wireless charging environment Figure 1A according to some embodiments of the disclosure.

[0034] Figure 1C is a block diagram illustrating a ground pad that can act as a wireless charging device according to some embodiments of the disclosure.

[0035] Figure 2A An example wireless charging system with an additional DC / DC converter is shown.

[0036] Figure 2B An example wireless charging system with an additional DC / DC converter is shown.

[0037] Figure 3A An example circuit topology of a wireless charging converter according to some embodiments of the disclosure is shown.

[0038] Figure 3B An example circuit topology of a wireless charging converter according to some embodiments of the disclosure is shown.

[0039] Figure 4A An example waveform illustrating the operation of an example circuit topology of Figure 3A according to some embodiments of the disclosure is shown.

[0040] Figure 4B An example waveform illustrating the operation of an example circuit topology of Figure 3B according to some embodiments of the disclosure is shown.

[0041] Figures 5A-5B An example circuit topology including a bidirectional shorting switch according to some embodiments of the disclosure is shown. DETAILED DESCRIPTION

[0042] The following detailed description of particular embodiments presents various descriptions of particular embodiments. However, the innovations described herein can be embodied in a multitude of different ways. For example, the innovations described herein can be implemented in various ways including as defined and encompassed by the claims. In this description, reference is made to the drawings where like reference numerals can indicate like elements among the figures. It will be appreciated that the elements in the figures are not necessarily drawn to scale. Furthermore, it will be appreciated that certain embodiments can include more elements than shown in a figure and / or a subset of the elements shown in a figure. Additionally, some embodiments can incorporate aspects from two or more figures. Headings are provided for convenience only and do not affect scope or meaning.

[0043] Wireless charging devices can be used to wirelessly charge vehicles, such as electric vehicles having a battery pack. A wireless charging device, such as a ground pad, can wirelessly transmit (e.g., via induction) power received from an external source (e.g., a power grid, solar cell(s), etc.) to an electric vehicle. The ground pad can be positioned under a vehicle pad of the electric vehicle to charge the electric vehicle. A wireless charging direct current (DC) / DC converter (also referred to as an aggregated DC / DC power converter) generally includes a DC / alternating current (AC) inverter inside the ground pad and an AC / DC rectifier inside the vehicle pad. Power can be wirelessly transmitted from the ground pad to the vehicle pad. The wireless charging disclosed herein can be applied to any suitable vehicle, including electric vehicles having a battery pack and hybrid vehicles including an internal combustion engine and a battery pack.

[0044] One or more aspects of the present disclosure relate generally to systems and methods for wirelessly charging a battery pack of a vehicle, which can have a relatively wide range of battery voltages. Illustratively, aspects of the present disclosure relate to a wireless charging circuit configurable for operation at different input and output voltages. In some embodiments, a wireless charging DC / DC converter can be configured at a topology level during manufacturing time to set a converter voltage gain ratio of the converter including a particular vehicle pad. During manufacturing of vehicle pads with different battery packs, the same circuit elements can be connected differently through electrical connectors such as jumper cables. Thus, these different vehicle pads with the same ground pad in the wireless charger can accommodate a wide range of battery voltages or a wide range of battery load impedances without the need to utilize additional DC / DC converters. More specifically, a wireless charging DC / DC converter including the same ground pad of the wireless charger can generate a wide range of output voltage levels with 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 battery packs having nominal and / or maximum voltage ratings including, but not limited to, 400 volts (V) or 800 V.

[0045] In some embodiments, one or more bidirectional shorting switches can be integrated into the wireless charging DC / DC converter. For example, a bidirectional shorting switch can be deployed on the vehicle side of the wireless charging DC / DC converter (e.g., inside the vehicle pad). As another example, a bidirectional shorting switch can be deployed on the ground side of the wireless charging DC / DC converter (e.g., inside the ground pad). In certain applications, there can be one bidirectional shorting switch on the vehicle side and another bidirectional shorting switch on the wireless charger side. The bidirectional shorting switches can provide an alternating current (AC) short across the resonant tank. The one or more bidirectional shorting switches can maintain a generally constant common mode voltage across the ground pad coil and / or the vehicle pad coil. In this way, use of the bidirectional shorting switch(s) can reduce leakage current associated with the wireless charging DC / DC converter. This can reduce energy consumption and / or minimize conducted and radiated emissions.

[0046] In certain conventional designs, wireless charging systems often include additional DC / DC converters relative to the embodiments of the wireless charging systems disclosed herein, either before or after the wireless charging DC / DC converter, to accommodate a wide battery voltage range and a wide battery load impedance range. For example, to charge a battery pack at a nominal and / or maximum voltage of 400V and 800V, respectively, one additional DC / DC converter can be used relative to a converter that includes only a vehicle pad and a ground pad. The additional DC / DC converter can increase the range of wireless charger voltage gain. The additional DC / DC converter can be a step-down and / or step-up converter between the battery module and the wireless power receiver. Such an approach can involve additional cost for building the wireless charging system. Moreover, the additional DC / DC converter can increase the weight of the wireless charging system. Additionally, deploying the additional DC / DC converter between the battery module and the wireless power receiver can result in energy loss.

[0047] To avoid the additional DC / DC converter, other wireless charging systems can utilize variations of the coil and resonant capacitor to support different battery charging voltages. However, variations of the coil and / or resonant capacitor result in additional complexity for supply chain and production management.

[0048] To address at least some of the above issues, a wireless charging DC / DC converter or topology thereof is disclosed in accordance with some embodiments of the present disclosure. In some embodiments, the wireless charging DC / DC converter can be configured (e.g., using jumpers) at a topology level during manufacturing or assembly in a factory to set a converter voltage gain ratio in a particular vehicle pad for a corresponding battery pack of a vehicle. Additionally, active switches (e.g., relays or semiconductor switches) can be deployed 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 of a factory for manufacturing or assembly). This can accommodate a wide range of battery voltages 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 a circuit topology of the vehicle pad to achieve a converter voltage gain ratio according to a desired battery pack voltage range (e.g., from 200V to 800V) and / or a wide range of battery load impedances. Advantageously, based on embodiments of the present disclosure, a relatively wide range of battery pack voltages can be achieved using a ground pad and various vehicle pad topologies without using additional DC / DC converters. The same set of hardware (e.g., same transistors, same coils, 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 exerting control over one or more of a duty cycle, a switching frequency, or a phase shift between the primary side and the secondary side.

[0049] In some embodiments, the disclosed wireless charging DC / DC converter employs the same coils and / or the same resonant capacitors to facilitate battery charging across different vehicle battery charging platforms. The wireless charging DC / DC converter can utilize the same or a single PCB to match different input and / or output voltages specified by different battery pack charging platforms. The wireless charging DC / DC converter can be associated with different PCB assemblies (PCBAs) to support different vehicle battery charging platforms. Advantageously, hardware design complexity and cost of building a wireless charging system can be reduced by integrating the disclosed wireless charging DC / DC converter into a wireless charging system.

[0050] In some embodiments, the bidirectional shorting switch can short a resonant tank of the ground pad (e.g., a resonant capacitor in series with a ground pad coil), and / or the bidirectional shorting switch can short a resonant tank of the vehicle pad (e.g., a resonant capacitor in series with a vehicle pad coil). The bidirectional shorting switch can establish a generally 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 using 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.

[0051] While various aspects will be described in terms of illustrative combinations of features, it should be appreciated that the combinations are not limited to just those combinations described but are intended to include all possible combinations of these features. More generally, the various aspects of the application can apply to various types of vehicle charging mechanisms, power sources, interfaces, etc. Moreover, while a particular DC / DC converter schematic will be described for charging batteries and / or battery packs at different voltage levels, this illustrative DC / DC converter schematic should not be construed as limiting. Thus, those skilled in the art will appreciate that the various aspects of the application are not necessarily limited to application to any particular type of vehicle, vehicle charging infrastructure, data communication, or illustrative interactions between a vehicle, owner / user, and a wireless battery charging system.

[0052] Wireless Charging Overview

[0053] Generally speaking, inductive charging (often referred to as wireless charging) is a form of wireless power transfer. Inductive charging uses electromagnetic induction to generate or otherwise provide power to a device without the need for physical electrical connectivity. Specifically, various devices can be placed in proximity to a charging station or inductive pad without the need for precise alignment or making electrical contact, physical docking, electrical plug-in, etc. Such devices include, but are not limited to, vehicles, manufacturing equipment, consumer electronics, medical devices, etc.

[0054] According to aspects of the present application, an inductive charging system is configured to transfer energy through inductive coupling between components. An illustrative charging system includes a transfer component, which can be configured as a charging station or charging pad. Alternating current (e.g., input current) from a power source is passed through an inductive coil in the charging station or pad. Based on the input current, a magnetic field is generated (or induced) by the moving charges through the inductive coil (e.g., ground pad coil). Illustratively, the strength of the magnetic field can fluctuate at least in part according to variations or fluctuations in the amplitude of the input current. The varying magnetic field induces an alternating current in an inductive coil (e.g., vehicle pad coil) on a receiving device. The inductive alternating current in the receiving device can then be converted to direct current by a rectifier. Finally, the receiving vehicle can include additional charging components and / or systems that utilize the converted direct current to charge a battery system, provide operational power, or a combination thereof.

[0055] When the illustrative inductive charging system uses resonant inductive coupling components / techniques, greater distances between the ground pad and vehicle pad coils can be achieved. More specifically, in some embodiments, a capacitor can be connected to each inductive coil to create two LC circuits with a specific resonant frequency. The frequency of the alternating current is matched to the resonant frequency. Moreover, the matched frequency can be further selected according to the distance between the transmitting device and the receiving device for peak efficiency. In addition, other materials for the receiver coil can be used (such as silver-plated copper or sometimes aluminum) for the purpose of energy transfer efficiency to minimize weight and reduce resistance.

[0056] Figure 1A is a schematic diagram of an environment 100 for implementing an inductive-based wireless charging system according to aspects of the present application. The environment 100 illustratively can correspond to a commercial implementation, such as a parking lot, parking space, toll booth, etc. The environment 100 can correspond to a private or other non-commercial implementation, e.g., a private residence, etc. As an illustrative example, an implementation of an inductive-based wireless charging system in a non-commercial implementation can include a ground pad 102 configured to generate a variable magnetic field according to an inductive charging method. Also as shown, the ground pad 102 (which can also be referred to as a transfer component) can correspond to a standalone component that is operable to be installed or placed on a floor 104 or other flat surface. In some other embodiments, the ground pad 102 can be integrated or combined with other devices or components. Figure 1A

[0057] ​The ground pad 102 can be connected to one or more power sources, such as input from a utility company, a real-time power source (e.g., a solar cell or wind energy source), an energy storage battery, or a combination thereof. The power source is configured to provide input AC power as described herein. The ground pad 102 can be connected to the power source via a direct electrical connection 106, such as via a junction box 108 located on a wall surface 118.

[0058] like Figure 1A As shown, in one embodiment, the ground mat 102 corresponds to a form factor that allows for wireless charging of a vehicle having a vehicle mat coil located on a floor 104. The ground mat 102 can have a form factor that allows a vehicle to be positioned directly above the top surface of the ground mat 102. Illustratively, the dimensions of the ground mat 102 (e.g., the height and width of the ground mat 102) can be configured such that the distance between the top surface of the ground mat 102 and the bottom surface of the vehicle meets certain criteria, such as a minimum distance between the ground mat coil and the vehicle mat coil, a maximum distance between the ground mat coil and the vehicle mat coil, etc. In some embodiments, the vehicle or the ground mat 102 (or a combination) can be configured with additional features for adjusting (e.g., statically and / or dynamically adjusting) this distance or otherwise changing the relative orientation between the ground mat 102 and the vehicle.

[0059] In some embodiments, the ground pad 102 can be configured to charge a battery pack of a vehicle, wherein the battery pack can have a nominal voltage exceeding 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 ground pad 102 can be configured to supply 800 volts DC power. In some embodiments, the ground pad 102 can provide a voltage ranging from approximately 200 volts to 800 volts.

[0060] Figure 1B A block diagram of an environment 100 is shown that includes a wireless charging device 111 (e.g., a grounding pad 102) that wirelessly communicates with a vehicle 112, for example, via an induction-based magnetic field. The wireless charging device 111 is also connected to one or more energy sources 110. Although the wireless charging device 111 is shown as having a direct connection to the energy source 110, at least some portion of the current alternate input can also be provided via wireless transmission methods. Additionally, in embodiments with multiple power sources, the environment can also include various switching components to enable selection of energy from individual energy sources 110 or combinations of energy sources 110.

[0061] Figure 1C Description can be used as wireless charging device 111 ( Figure 1BA block diagram of a ground pad 102 (as shown in FIG. 1) is shown. The ground pad 102 can include at least one ground pad coil 122 for inducing a magnetic field from an input current provided by the energy source 110. As shown, the input current can be provided by the direct electrical connection 106. Figure 1C

[0062] In some embodiments, the ground pad 102 can also include various sensor components 124 related to the charging process. By way of illustration, the sensor components 124A, 124B, 124C, 124D can be configured for various functions, such as detection of the vehicle 112, detection of objects, measurement of distance to the vehicle, environmental sensors (e.g., temperature sensors, humidity sensors), pressure sensors, etc. In one embodiment, the sensor components 124 can include a radar sensor. The sensor components 124 can include logic and processing components related to the charging process, including operational measurements, operational controls, safety measurements, communication components, etc.

[0063] Wireless charging system with wireless charging converter and DC / DC converter

[0064] Figure 2A An exemplary wireless charging system 200A is shown. As shown, Figure 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 (e.g., within a vehicle pad) of the wireless charging system 200A to convert the output voltage from the DC converter 202A to a voltage provided by a battery pack 206A of the vehicle. The battery pack 206A can be referred to as a battery coil. With the DC / DC converter 204A, the voltage level provided by the wireless charging DC / DC converter 202A can be adjusted to a voltage level specified for the battery pack 206A.

[0065] Figure 2B An exemplary wireless charging system 200B is shown. As shown, Figure 2B The wireless charging system 200B includes a wireless charging DC / DC converter 202B and a DC / DC converter 204B. The DC / DC converter 204B is included on the ground side (e.g., within a ground pad) of the wireless charging system 200B to convert the output voltage from the DC / AC conversion stage to a voltage level such that the wireless charging DC converter 202B provides a voltage specified by a battery pack 206B of the vehicle.

[0066] ​The additional DC / DC converter 204A and / or 204B can be a buck and / or boost converter that can involve additional components and cost of the wireless charging system 200A or 200B. Further, the DC / DC converter 204A and / or 204B can add weight to the wireless charging system 200A or 200B. Additionally, deploying the additional DC / DC converter 204A between the battery pack 206A and the portion of the wireless charging DC converter 202A on the vehicle side can result in energy loss on the vehicle side.

[0067] Example wireless charging system

[0068] Figures 3A-3B Example circuit topologies 300A and 300B of a wireless charging DC / DC converter are shown, where the topology of the vehicle pad can be configured during manufacturing based on a desired battery voltage range. More specifically, a vehicle pad with circuit topology 300A and 300B can be manufactured using the same coil (e.g., vehicle pad coil 330), transistors 360-364, and resonant capacitor 336, which can be configured during manufacturing of the vehicle pad. Such a vehicle pad, together with the same ground pad, can charge battery packs with different voltage ranges (e.g., 400V and 800V maximum voltages). In some embodiments, the vehicle pad can be configured to be a vehicle pad of circuit topology 300A or circuit topology 300B by manipulating one or more connectors (e.g., jumpers) mounted on a printed circuit board (PCB) of the vehicle pad. 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 pad in the field (e.g., outside of a factory for manufacturing or assembly) for switching between circuit topology 300A or circuit topology 300B. In addition to charging battery packs at various nominal and / or maximum voltages, circuit topology 300A and circuit topology 300B can also provide voltage regulation around the nominal voltage by associating with one or more of control duty cycle, switching frequency, or phase shift of the signals on the vehicle pad side and the ground pad side.

[0069] More specifically, Figure 3A Circuit topology 300A is shown to be used to charge a battery pack 390A at a first voltage, while Figure 3B Circuit topology 300B is shown to be used 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 Figures 3A-3BAs shown, the circuit topology 300A or the circuit topology 300B each includes at least a ground pad coil 332, a vehicle pad coil 330, a capacitor 336 and 334. In the case of wireless charging, the ground pad and the vehicle pad can not be physically connected. Electrical power can be provided from the ground pad (e.g., the ground pad 102 of the wireless charging system 100 of Figure 1A Figure 1B the wireless charging device 111 of the wireless charging system 100 of Figure 1B FIG. 1) and the provided electrical power can be wirelessly coupled to the vehicle pad (e.g., a portion of the vehicle 112 of the wireless charging system 100 of

[0070] As shown in Figure 3A FIG. 3A, the electrical power from the ground pad is converted by the circuit topology 300A to charge a battery pack 390A that can be used to power the vehicle. The battery pack 390A can have a maximum voltage of, for example, 400 V. In some embodiments, although not explicitly shown in Figure 3A FIG. 3A, the voltage level of the energy source to which the ground pad is connected can output a DC voltage that is lower than the maximum voltage of the battery pack 390A (e.g., 400 V) that is then converted by the circuit topology 300A to a voltage used to charge the battery pack 390A to charge the battery pack 390A.

[0071] As shown in Figure 3A FIG. 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 can also include a capacitor 370. In the circuit topology 300A, the vehicle pad includes a resonant tank that includes the 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 shunted with a capacitor 380. The transistors 350, 352, 354, and 356 of the ground pad and the transistors 360, 362, 364, and 366 of the vehicle pad can be field effect transistors (FETs), as shown. For example, the transistors can be metal oxide semiconductor field effect transistors (MOSFETs), such as N-type MOSFETs and / or P-type MOSFETs. As shown, the transistors 350-356 and 360-366 are N-type FETs.

[0072] Figure 3B FIG. 3B shows the circuit topology 300B configured to wirelessly charge a vehicle pad (e.g., the vehicle pad 130 of the wireless charging system 100 of Figure 3A ​a wireless charging DC / DC converter of a different topology (e.g., circuit topology 300B) than the wireless charging DC / DC converter of the vehicle pad of FIG. 3. Specifically, the vehicle pad includes power electronics arranged differently in Figure 3B and Figure 3A . Otherwise, the vehicle pads of circuit topologies 300A and 300B can include examples of the same components. During manufacturing or assembly of the vehicle pad, these components can be arranged differently for the vehicle pad shown in Figure 3A and 3B to provide different voltage conversion ratios. For example, the wireless charging converter having the topology 300B shown in Figure 3B may have approximately twice the voltage conversion ratio of the wireless converter having the topology 300A shown in Figure 3A . The circuit topology 300B can generate a DC voltage that is approximately twice the voltage of the circuit topology 300A.

[0073] As shown in Figure 3B , the transistors 360, 362, 364, and 366 of the vehicle pad are arranged as a stacked half-bridge. The stacked half-bridge includes two half-bridges arranged in series with each other. Figure 3B The first half-bridge (e.g., including transistors 360 and 362) of the vehicle pad of Figure 3A is arranged the same as one of the half-bridges in the vehicle pad of Figure 3B . The first half-bridge is in parallel with the capacitor 380, as shown in Figure 3B . The second half-bridge (e.g., including transistors 364 and 366) of the vehicle pad of Figure 3B is arranged in series with the first half-bridge and between the HV-MID and the HV node. The second half-bridge is in parallel with the capacitor 382, as shown in

[0074] The vehicle pad of the circuit topology 300B can be used in a vehicle having a battery pack 390B with a higher voltage specification than a vehicle having a battery pack 390A with the circuit topology 300A. As one example, the vehicle pad of the circuit topology 300B can be used in a vehicle having a maximum battery pack voltage of 800 V, and the vehicle pad of the circuit topology 300A can be used in a vehicle having a maximum battery pack voltage of 400 V.

[0075] The hardware components (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) associated with the ground pad and the vehicle pad can be the same as those shown in Figure 3A . In some examples, Figure 3A and 3B the transistors (e.g., transistors 360, 362, 364, and 366) of the vehicle pad can be 650 V MOSFETs.Figure 3B and Figure 3A The vehicle pad coil 330, the ground pad coil 332, and the capacitors 336, 334, and 370 in the ground pad and the vehicle pad in Figure 3B may also be the same. Further, in Figure 3A the energy source to which the ground pad is connected can output the same DC voltage as in Figure 3A-3B In some other embodiments, the ground pad in may be connected to different types of energy sources that provide different levels of input voltage to the circuit topology 300A and the circuit topology 300B.

[0076] In some embodiments, the vehicle pad is configured during manufacturing to connect (and / or disconnect) the power electronics components on the PCB of the vehicle pad using jumpers or any other suitable electrical connectors to provide the desired conversion ratio between the ground pad coil 332 on the ground pad and the vehicle pad coil 330 on the vehicle pad. For example, a jumper can be attached to the PCB associated with the vehicle pad to connect two points on the PCB for configuring 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, the jumper attached to the PCB can 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 cables) can be utilized to configure the wireless charging DC / DC converter to different circuit topologies than the circuit topology 300A and the circuit topology 300B to achieve different levels of input and output voltages.

[0077] Figure 3A In the circuit topologies 300A and 300B, the half-bridge connected to the negative loop node 304A or 304B (e.g., HVTANK-) is connected to a different node. Specifically, the half-bridge including transistors 364 and 366 connected to the negative loop node 304A in the vehicle pad of Figure 3B is connected between the nodes HV-MID and HV-. During manufacturing, the half-bridge including transistors 364 and 366 can be connected as shown in Figure 3A or as shown in Figure 3B This can include connecting the half-bridge using jumpers. In certain applications, the vehicle pad can be provided with a pre-configured half-bridge as shown in Figure 3A or as shown in Figure 3B and adjusted to different configurations as needed during manufacturing.

[0078] Advantageously, by using the same hardware (e.g., same transistors, same coils, same capacitors) for vehicle pads with different conversion rates while utilizing PCB connectors, the cost of building the vehicle pad and / or wireless charging system can be reduced. Additionally, the vehicle pad and / or wireless charging system can be made lighter because less hardware is involved to charge different battery packs. Furthermore, by using the same coils and capacitors in wireless charging DC / DC converters with different conversion rates, the complexity of designing a wireless charging system to meet different input and output voltage specifications can be reduced.

[0079] Figures 4A-4B Exemplary waveforms 400A and 400B are shown 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 exhibit one of waveforms 400A and 400B to provide various voltages (e.g., 400V and 800V) for charging various battery packs. Advantageously, unlike wireless charging systems 200A and 200B, the same set of hardware (e.g., coils, transistors, resonant capacitors, etc.) arranged in various circuit topologies can provide a wide range of battery voltages without the need for additional DC / DC converters.

[0080] Figure 4A Shows the instructions Figure 3A Example waveforms of the operation of the circuit topology 300A. Figure 4A As shown, the voltage across the positive loop node 302A (eg, HVTANK+) and the negative loop node 304A (eg, HVTANK-) has a maximum voltage of 400 V and a minimum voltage of -400 V. The circuit topology 300A may be used to charge a 400 V battery pack.

[0081] Figure 4B Shows the instructions Figure 3B Example waveforms of the operation of the circuit topology 300B. Figure 4A As shown, the voltage across the positive return node 302B (eg, HVTANK+) and the negative return node 304B has a voltage swing of 800 V, with a maximum voltage of 800 V and a minimum voltage of 0 V. The circuit topology 300B can be used to charge an 800 V battery pack.

[0082] Example Bidirectional Shorting Switch

[0083] 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 vehicle pad coil 330 and / or the ground pad coil 332. For example,Figure 3A The ground pad coil 332 can generate a leakage current associated with the ground pad. The leakage current can flow through a parasitic capacitor (not shown in Figure 3A to a heat sink (not shown in Figure 3A associated with the circuit topology 300A. As another example, Figure 3A The vehicle pad coil 330 can generate a leakage current associated with the vehicle pad. The leakage current can flow through a parasitic capacitor (not shown in Figure 3A to a heat sink (not shown in Figure 3A associated with the circuit topology 300A. More specifically, when the vehicle pad coil 330 is active, a common mode voltage swing can occur across the nodes 302A and 304A. The common mode voltage swing across the vehicle pad coil 330 can cause the leakage current to flow through the vehicle pad coil 330.

[0084] To reduce the 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 the circuit topology 300A and / or the circuit topology 300B to achieve the circuit topologies shown in Figures 5A-5B The one or more bidirectional shorting switches can reduce the leakage current that flows through the parasitic capacitor(s) associated with the circuit topology 300A and / or the circuit topology 300B to the heat sink(s). As described above, the leakage current can be generated by the vehicle pad coil 330 and / or the ground pad coil 332 (e.g., due to a common mode voltage swing caused by the operation of the circuit topology 300A or the circuit topology 300B). The one or more bidirectional shorting switches can prevent or reduce the common mode voltage swing such that a constant common mode voltage or a relatively constant common mode voltage can be achieved across the vehicle pad coil 330 and the ground pad coil 332, thereby reducing the leakage current. With the bidirectional shorting switches, current can flow in either direction across the bidirectional shorting switches.

[0085] Advantageously, with the reduced leakage current, less energy can be dissipated compared to the circuit topology 300A and the circuit topology 300B. Additionally, conducted and radiated emissions can also be reduced or minimized.

[0086] Figures 5A-5B Example circuit topology 500A and example circuit topology 500B of a wireless charging DC / DC converter are shown. The circuit topology 500A is similar to the circuit topology 300A of Figure 3A except that a bidirectional shorting switch is included in the circuit topology 500A. The circuit topology 500A can function the same or similarly to the circuit topology 300A except for the functionality provided by the bidirectional shorting switch (e.g., reducing the leakage current by reducing the common mode voltage swing). The circuit topology 500B is similar to the circuit topology 300B except that a bidirectional shorting switch is included in the circuit topology 500B. The circuit topology 500B can function the same or similarly to the circuit topology 300B except for the functionality provided by the bidirectional shorting switch (e.g., reducing the leakage current by reducing the common mode voltage swing).Figure 3B Circuit topology 500B may function the same as or similar to circuit topology 300B, except for the functionality provided by the bidirectional shorting switch (eg, reducing leakage current by reducing the common-mode voltage swing).

[0087] like Figure 5A As shown, bidirectional shorting switch 522A is shunted across vehicle pad coil 330, and bidirectional shorting switch 524 is shunted across ground pad coil 332. Circuit topology 500A represents an H-bridge converter topology with bidirectional shorting switches. With an H-bridge converter, bidirectional shorting switch 524 can be coupled between switch nodes 552 and 554, thereby providing a shunt path to apply zero voltage across the resonant tank. The resonant tank can include ground pad coil 332 and capacitor 334, as shown in FIG. Figure 5A By utilizing the bidirectional shorting switch 524 , a constant common mode voltage can be achieved across the ground pad coil 332 , which can reduce leakage current across the resonant tank including the ground pad coil 332 .

[0088] Similarly, a bidirectional shorting switch 522A can be implemented on the vehicle mat of circuit topology 500A for ground current leakage reduction. The battery pack on the vehicle side can have a relatively high voltage, such as a maximum voltage of 400 volts. Bidirectional shorting switch 522A can be coupled between switch nodes 502A and 504A to achieve a substantially constant common-mode voltage across the vehicle mat coil 330 to reduce leakage current.

[0089] like Figure 5AAs shown, each of bidirectional shorting switch 522A and bidirectional shorting switch 524 can include at least two field effect transistors (FETs), such as MOSFETs, connected in a back-to-back fashion in series. Bidirectional shorting switch 522A and 524 are each shown as including two FETs arranged in series between two nodes with sources connected to each other. In this way, bidirectional shorting switch 522A is capable of reducing or eliminating voltage swings of both polarities across nodes 502A and 504A (i.e., positive voltage swings between nodes 502A and 504A, and negative voltage swings between nodes 502A and 504A). Alternatively, the bidirectional shorting switch can include two FETs arranged in series between two nodes with drains connected to each other. Bidirectional shorting switches 522A and 524 can include N-type transistors as shown. In some other examples, bidirectional shorting switches 522A and 524 can include P-type transistors. Bidirectional shorting switch 524 is capable of reducing or eliminating voltage swings of both polarities across nodes 552 and 554 (i.e., positive voltage swings between nodes 552 and 554, and negative voltage swings between nodes 552 and 554). In some embodiments, when bidirectional shorting switches 522A and 524 are closed, current can flow in either direction across bidirectional shorting switches 522A and 524, and when bidirectional shorting switches 522A and 524 are open, current can be blocked in either direction across bidirectional shorting switches 522A and 524.

[0090] As Figure 5B shown, bidirectional shorting switch 522B is shunted across the resonant tank including vehicle pad coil 330, and bidirectional shorting switch 524 is shunted across the resonant tank including ground pad coil 332. Bidirectional shorting switch 524 can be coupled between switch nodes 552 and 554, providing a shunt path to apply zero voltage across the resonant tank. The resonant tank can include ground pad coil 332 and capacitor 334, as Figure 5B shown. With bidirectional shorting switch 524, a constant common mode voltage on ground pad coil 332 can be achieved.

[0091] Similarly, bidirectional shorting switch 522B for ground current leakage current reduction can be implemented on the vehicle side of circuit topology 500B. The battery pack on the vehicle side can have a relatively high voltage, for example, a maximum voltage of 800 volts. Bidirectional shorting switch 522B can be coupled between switch nodes 502B and 504B, enabling a constant common mode voltage across vehicle pad coil 330 to reduce leakage current.

[0092] As Figure 5BAs shown, each of bidirectional shorting switch 522B and bidirectional shorting switch 524 can include at least two field effect transistors (FETs), such as MOSFETs, connected in a back-to-back fashion in series. As such, bidirectional shorting switch 522B is capable of reducing or eliminating voltage swings of both polarities across nodes 502B and 504B (i.e., positive voltage swings between nodes 502B and 504B, and negative voltage swings between nodes 502B and 504B). Bidirectional shorting switch 524 is capable of reducing or eliminating voltage swings of both polarities across nodes 552 and 554 (i.e., positive voltage swings between nodes 552 and 554, and negative voltage swings between nodes 552 and 554).

[0093] As shown, circuit topology 500B on the vehicle side represents a stacked half-bridge including two half-bridges (e.g., four FETs in a series stack) in series with each other. Fly capacitor 560B can be connected in series between two FETs in bidirectional shorting switch 522B, thereby providing a shunt path to apply half of the direct current (DC) bus voltage on the resonant tank circuit decoupled from the DC bus in order to achieve a constant common mode voltage across vehicle pad coil 330. In some other embodiments, a stacked half-bridge topology with a fly capacitor can be implemented on the ground side. Figure 5B Bidirectional shorting switches disclosed herein can reduce inductive charging ground leakage current in any of the wireless charging pads disclosed herein. Bidirectional switches connected between switch nodes can be used to short the tank circuit such that the common mode voltage on the coil is relatively constant and stable. Bidirectional shorting switches can be implemented as any of the vehicle pads and / or any of the ground pads disclosed herein.

[0094] Wireless charging circuitry disclosed herein can be implemented with 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) segmented coils to make multiple LC resonators in series to reduce the common mode voltage on the coil, and (2) additional DC / DC converters on-board and off-board 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 segmented coils to make multiple LC resonators in series. Such segmented coils can be implemented in any of the wireless charging pads disclosed herein, such as in any of the ground pads and / or any of the vehicle pads in 3B, 5A, and / or 5B.

[0095] Figure 3A Conclusion

[0096] Conclusion

[0097] ​The foregoing disclosure is not intended to be exhaustive or to limit the disclosure to the precise forms disclosed. Thus, various alternatives and modifications will be apparent to those skilled in the art in view of the disclosure, whether explicitly described or implied herein. Embodiments of the disclosure have been described so as to enable a person of ordinary skill in the art to make and use the disclosure, and changes in form and detail can be made without departing from the scope of the disclosure. Thus, the disclosure is not limited to the precise examples described herein, but rather, the scope of the disclosure is defined by the appended claims.

[0098] It should be understood that all the objectives or advantages can not necessarily be achieved according to any particular example described herein. Thus, for example, one skilled in the art will recognize that some examples can operate to achieve one advantage or a group of advantages as taught herein without necessarily achieving other objects or advantages as taught or suggested herein.

[0099] All processes described herein can be embodied in software code modules executed by a computing system including a computer or processor, and fully automated via the software code modules. The code modules can be stored in any type of non-transitory computer-readable medium or other computer storage device. Some or all of the methods can be implemented in specialized computer hardware.

[0100] Many other variations will be apparent from this disclosure. For example, depending on the example, some actions, events, or functions can be performed in a different order, may be added, modified or removed altogether (e.g., not all described actions or events are required to practice a described algorithm), depending on the example. In addition, functions or acts may

[0101] The various illustrative logical blocks, modules, and circuits described in connection with the examples disclosed herein can be implemented or performed with a machine (e.g., processing unit or processor, digital signal processor (DSP), application specific integrated circuit (ASIC), 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. A processor can be a microprocessor, but in the alternative, the processor can be a controller, microcontroller, or state machine, combinations of the above, or the like. A processor can include electrical circuitry for processing computer-executable instructions. In some examples, a processor includes an FPGA or another programmable device that performs logic operations without processing computer-executable instructions. A processor can also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, a microprocessor combined with a DSP core, or any other such configuration. Although described herein primarily with respect to digital technology, a processor can also include primarily analog components. The computing environment can include any type of computer system, including, but not limited to, a mainframe computer system, a desktop computer system, a laptop or notebook computer system, a tablet computer system, a handheld computer system, a personal digital assistant (PDA), a server, a client, a mobile telephone, a television with one or more processors embedded therein, a gaming console, a handheld media player, an automobile computer system, an appliance, an end-user system, or the like.

[0102] The elements of a method, process, routine, or algorithm described in connection with the embodiments disclosed herein can be embodied directly in hardware, in a software module executed by a processor device, or in a combination of the two. A software module can reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, a removable disk, a CD-ROM, or any other form of non-transitory computer-readable storage medium. An example storage medium can be coupled to the processor device such that the processor device can read information from, and write information to, the storage medium. In the alternative, the storage medium can be integral to the processor device. The processor device and the storage medium can reside in an ASIC. The ASIC can reside in a user terminal. In the alternative, the processor device and the storage medium can reside as discrete components in a user terminal.

[0103] The processes described herein, or in the figures accompanying this disclosure, can be initiated in response to an event, such as on 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 a process is initiated, a set of executable program instructions stored on one or more non-transitory computer-readable media (e.g., hard disk drive, flash memory, removable media, etc.) can be loaded into the memory (e.g., RAM) of a server or other computing device. The executable instructions can then be executed by a hardware-based computer processor of the computing device. In some embodiments, such a process, or portions thereof, can be implemented serially or in parallel on multiple computing devices and / or multiple processors.

[0104] In this context, unless specifically stated otherwise, conditional language such as "may," "could," "might," or "could" is understood to be generally used to convey that some examples include, while other examples do not, certain features, elements, and / or steps. Thus, such conditional language is generally not intended to imply that features, elements, and / or steps are in any way examples, or that examples necessarily include logic for determining, with or without user input or prompting, whether such features, elements, and / or steps are included or to be performed in any particular example.

[0105] Unless specifically stated otherwise, disjunctive language such as the phrase "at least one of X, Y, or Z" should be understood in context as generally used to indicate that an item, term, etc., can be X, Y, or Z, or any combination thereof (e.g., X, Y, and / or Z). Thus, such disjunctive language is generally not intended to, and should not, imply that some instance requires that at least one of X, at least one of Y, or at least one of Z each be present.

[0106] Any process descriptions, elements, or blocks in the flowcharts described herein and / or depicted in the accompanying drawings should be understood to potentially represent modules, segments, or portions of code that include executable instructions for implementing the specific logical functions or elements in the process. Alternative examples are included within the scope of the examples described herein, in which elements or functions may be deleted, performed, or performed from the order shown or discussed (including substantially simultaneously or in reverse order), depending on the functionality involved as will be understood by those skilled in the art.

[0107] It should be emphasized that many changes and modifications may be made to the above examples, and the elements of these changes and modifications should be understood as other acceptable examples. All such modifications and variations are intended to be included within the scope of this disclosure.

[0108] Any process description, element or block in the flowcharts described herein and / or depicted in the accompanying drawings should be understood to potentially represent a module, segment or portion of code that includes executable instructions for implementing the specific logical functions or elements in the process. Alternative implementations are included within the scope of the examples described herein, in which elements or functions can be deleted, performed from the order shown or discussed, including substantially simultaneously or in reverse order, depending on the functionality involved as will be understood by those skilled in the art.

[0109] Unless specifically stated otherwise, the terms "a," "an" and "the" are not intended to refer to only a singular entity but can include one or more entities. For example, the term "a" or "an" entity should be understood to include one or more of those entities. As such, the terms "a" (or "an"), "one or more" and "at least one" can be used interchangeably herein. Further, the term "plurality" shall mean a number greater than one.

Claims

1. A wireless charging pad with reduced leakage current, the wireless charging pad comprising: a resonant circuit having a first circuit terminal and a second circuit terminal, the resonant circuit including a coil; and a bidirectional switch having a first switch terminal and a second switch terminal, the first switch terminal being connected to the first return terminal and the second switch terminal being connected to the second return terminal, wherein the bidirectional switch is configured to cause a common mode voltage across the coil to be reduced, and The wireless charging pad is configured for wireless power transfer. 2 . The wireless charging pad of claim 1 , wherein the bidirectional switch comprises a first transistor and a second transistor, wherein the first transistor and the second transistor are connected back-to-back.

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

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

5. The wireless charging pad of claim 1 , further comprising a stacked half-bridge circuit, wherein the first loop terminal and the first switch terminal are connected to a first switch node of the stacked half-bridge circuit, and wherein the second loop terminal and the second switch terminal are connected to a second switch node of the stacked half-bridge circuit. 6 . The wireless charging pad of claim 5 , wherein the stacked half-bridge circuit comprises a first half-bridge and a second half-bridge, the first half-bridge comprising a field effect transistor, and the second half-bridge comprising a field effect transistor. 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 . 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. The wireless charging pad of claim 1 , wherein the wireless charging pad is a vehicle pad, the vehicle pad comprising terminals configured to connect to a battery pack. 12 . The wireless charging pad of claim 1 , wherein the wireless charging pad is a ground pad comprising an electrical connector configured to connect to a power source.

13. A method for wireless power transmission with reduced leakage current, the method comprising: Excitation ground pad; as well as wirelessly transmitting power from the ground pad to the vehicle pad of the vehicle, wherein the vehicle includes a battery pack, and the vehicle is configured to charge the battery pack based on the wireless transmission power, and Wherein at least one of the vehicle mat or the ground mat includes a bidirectional shorting switch across a resonant circuit. 14 . The method of claim 13 , wherein the bidirectional shorting switch comprises a first transistor and a second transistor, wherein the first transistor and the second transistor are connected back-to-back. 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 provide a voltage of up to 800 volts to the battery pack.

18. A wireless charging converter, comprising: a first resonant circuit comprising a first coil; as well as a first electrical switch shunted across said first resonant tank, The first electrical switch is configured to reduce a common mode voltage across the first coil for wireless charging.

19. The wireless charging adapter according to claim 18, further comprising: a second resonant circuit including a second coil; as well as a second electrical switch shunted to the second resonant circuit, The second electrical switch is configured to adjust a second common-mode voltage on the second coil for charging a battery pack of a vehicle.

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

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

22. The wireless power 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. The wireless power 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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