Switch configuration control for wireless charging circuits

Abstract

To provide a wireless charging system and mechanism for charging a vehicle using a wireless charging circuit.SOLUTION: A method of wireless power transfer includes: energizing a first wireless charging pad that includes a switching circuit; repeatedly toggling the switching circuit between a first switch configuration and a second switch configuration; and causing wireless power transfer from the first wireless charging pad to a second wireless charging pad using a voltage generated from the repeatedly toggling. During the repeatedly toggling, switches of a first half bridge of the switching circuit change a state between the first switch configuration and the second switch configuration, and switches of a second half bridge of the switching circuit remain in a same state for the first switch configuration and the second switch configuration.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] [CROSS-REFERENCE TO RELATED APPLICATIONS] This application claims priority to U.S. Provisional Patent Application No. 63 / 653,055, filed May 29, 2024, entitled "SWITCH CONFIGURATION CONTROL FOR WIRELESS CHARGING CIRCUITS," the entire technical disclosure of which is incorporated herein by reference 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 using wireless charging circuitry. [Background technology]

[0003] Generally, inductive charging and capacitive charging are types of wireless power transfer. Wireless power transfer can be referred to as wireless charging. 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 induction pad without precise alignment or electrical contact, and without a physical dock, electrical plug, or the like. Such devices can include, but are not limited to, vehicles, manufacturing equipment, home appliances, medical devices, and the like. Summary of the Invention

[0004] The systems, methods, and devices of the present disclosure each have several innovative embodiments, no single one of which is solely responsible for all of the desirable attributes disclosed herein. The 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 techniques described herein relate to a method that includes energizing a first wireless charging pad that includes a switching circuit; repetitively switching the switching circuit between a first switch configuration and a second switch configuration, wherein switches of a first half-bridge of the switching circuit change state between the first switch configuration and the second switch configuration and switches of a second half-bridge of the switching circuit remain in the same state in the first switch configuration and the second switch configuration; and using a voltage generated by the repetitive switching to cause wireless power transfer from the first wireless charging pad to a second wireless charging pad.

[0006] In some aspects, the techniques described herein relate to a method further comprising detecting one or more conditions, wherein the iterative switching is performed in response to detecting the one or more conditions.

[0007] In some aspects, the technology described herein relates to a method, wherein the one or more conditions relate to at least one of a load interfaced with the switching circuit, a voltage of a battery pack of a vehicle including a second wireless charging pad, or a voltage of a power source associated with a first wireless charging pad.

[0008] In some aspects, the technology described herein relates to a method in which the vehicle includes a second wireless charging pad and the voltage of the battery pack of the vehicle is in the range of 200 volts to 1000 volts.

[0009] In some aspects, the technology described herein relates to a method in which there is an imbalance in duty cycles between a first switch configuration and a second switch configuration due to repetitive switching.

[0010] In some aspects, the technology described herein relates to a method, wherein repetitive switching of a switching circuit between a first switch configuration and a second switch configuration results in a lower voltage swing across a resonant tank of a first wireless charging pad electrically connected to the switching circuit compared to switching of the switching circuit between a third switch configuration, the first switch configuration, and the second switch configuration.

[0011] In some aspects, the technology described herein relates to a method in which the switching circuit includes an H-bridge circuit.

[0012] In some aspects, the technology described herein relates to a method of wireless power transfer that includes wirelessly receiving power from a ground pad at a vehicle pad of a vehicle, the vehicle pad including a switching circuit; and repeatedly switching the switching circuit between a first switch configuration and a second switch configuration, wherein switches of a first half-bridge of the switching circuit change state between the first switch configuration and the second switch configuration, and switches of a second half-bridge of the switching circuit are in the same state in both the first switch configuration and the second switch configuration.

[0013] In some aspects, the techniques described herein relate to a method further comprising detecting one or more conditions, wherein the iterative switching is performed in response to detecting the one or more conditions.

[0014] In some aspects, the technology described herein relates to a method, wherein the one or more conditions relate to at least one of a load interfaced with the switching circuit, a voltage range of a battery pack of the vehicle, or a voltage range of a power source associated with the ground pad.

[0015] In some aspects, the technology described herein relates to a method, wherein the voltage range of the battery pack of the vehicle is within the range of 200 volts to 1000 volts.

[0016] In some aspects, the technology described herein relates to a method in which there is an imbalance in duty cycles between a first switch configuration and a second switch configuration due to repetitive switching.

[0017] In some aspects, the technology described herein relates to a method, wherein repetitive switching of a switching circuit between a first switch configuration and a second switch configuration results in a lower voltage swing across a resonant tank of a vehicle pad electrically connected to the switching circuit compared to switching of the switching circuit between a third switch configuration, the first switch configuration, and the second switch configuration.

[0018] In some aspects, the technology described herein relates to a method further including charging a battery pack of a vehicle based on power received wirelessly from the ground pad.

[0019] In some aspects, the technology described herein relates to a wireless charging pad including: a switching circuit including a first half bridge and a second half bridge; a resonant tank electrically connected to the switching circuit, the resonant tank including a coil arranged for wireless power transmission; and a switch control circuit configured to repeatedly switch the switching circuit between a first switch configuration and a second switch configuration, wherein the first half bridge changes state between the first switch configuration and the second switch configuration and the second half bridge is in the same state in both the first switch configuration and the second switch configuration, wherein the wireless charging pad is configured to transmit wireless power sufficient to charge a battery pack at an operating voltage of at least 350 volts.

[0020] In some aspects, the technology described herein relates to a wireless charging pad, wherein the switch control circuit is further configured to detect one or more conditions, and wherein the switch control circuit is configured to iteratively switch the switching circuit between a first switch configuration and a second switch configuration in response to detecting the one or more conditions.

[0021] In some aspects, the technology described herein relates to a wireless charging pad, wherein the one or more conditions relate to at least one of a load interfaced with a switching circuit, a voltage range of a vehicle battery pack, or a voltage range of a power source associated with the wireless charging pad.

[0022] In some aspects, the technology described herein relates to a wireless charging pad, wherein the wireless charging pad is a grounding pad.

[0023] In some aspects, the technology described herein relates to a wireless charging pad in which repetitive switching of a switching circuit between a first switch configuration and a second switch configuration results in a lower voltage swing across a resonant tank compared to switching of the switching circuit between a third switch configuration, the first switch configuration, and the second switch configuration.

[0024] In some aspects, the technology described herein relates to a wireless charging pad in which the switching circuitry includes an H-bridge circuit. [Brief explanation of the drawings]

[0025] 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 its scope.

[0026] Embodiments of the present disclosure will be described with reference to the accompanying drawings, in which like reference numerals refer to like elements.

[0027] [Figure 1A] 1 illustrates an exemplary wireless charging environment in which implementations of the present disclosure can be implemented.

[0028] [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.

[0029] [Figure 1C] 1A-1C are diagrams of a grounding pad that can function as a wireless charging device according to some embodiments of the present disclosure.

[0030] [Figure 2A] 1 illustrates an exemplary circuit schematic diagram of a wireless charging system according to some embodiments of the present disclosure. [Figure 2B] 1 illustrates an exemplary circuit schematic diagram of a wireless charging system according to some embodiments of the present disclosure. [Figure 2C] 1 illustrates an exemplary circuit schematic diagram of a wireless charging system according to some embodiments of the present disclosure. [Figure 2D] 1 illustrates an exemplary circuit schematic diagram of a wireless charging system according to some embodiments of the present disclosure.

[0031] [Figure 3] FIG. 1 illustrates an exemplary block diagram of a wireless charging pad according to some embodiments of the present disclosure.

[0032] [Figure 4A] 4 illustrates an example switch configuration of the H-bridge circuit of the wireless charging pad of FIG. 3 in accordance with some embodiments of the present disclosure. [Figure 4B] 4 illustrates an example switch configuration of the H-bridge circuit of the wireless charging pad of FIG. 3 in accordance with some embodiments of the present disclosure. [Figure 4C] 4 illustrates an example switch configuration of the H-bridge circuit of the wireless charging pad of FIG. 3 in accordance with some embodiments of the present disclosure. [Figure 4D] 4 illustrates an example switch configuration of the H-bridge circuit of the wireless charging pad of FIG. 3 in accordance with some embodiments of the present disclosure.

[0033] [Figure 5A] 4 illustrates example waveforms of voltage amplitudes associated with operation of the wireless charging pad of FIG. 3 in accordance with some embodiments of the present disclosure. [Figure 5B]4 illustrates example waveforms of voltage amplitudes associated with operation of the wireless charging pad of FIG. 3 in accordance with some embodiments of the present disclosure. [Figure 5C] 4 illustrates example waveforms of voltage amplitudes associated with operation of the wireless charging pad of FIG. 3 in accordance with some embodiments of the present disclosure.

[0034] [Figure 6] 4 illustrates example waveforms of voltage amplitudes associated with operation of the wireless charging pad of FIG. 3 in accordance with some embodiments of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0035] The following detailed description of some embodiments presents various descriptions of specific embodiments. However, the innovations described herein can be embodied in many different ways, for example, as defined and encompassed 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 some embodiments can 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.

[0036] Generally described, one or more aspects of the present disclosure relate to systems and methods for wirelessly charging battery packs that may have a relatively wide range of battery voltages. Illustratively, aspects of the present disclosure relate to a wireless charging circuit that can operate under various input and output voltages by controlling power electronic switches. In some embodiments, to wirelessly charge a vehicle, a switch control circuit can control some switches of the H-bridge circuit to switch and other switches of the H-bridge circuit not to switch, rather than periodically switching each switch of an H-bridge circuit in a wireless vehicle charging pad (e.g., switching from open to closed or from closed to open) during transitions between states of the H-bridge. In this manner, during transitions between states of the H-bridge for wirelessly transmitting and / or receiving power, some switches of the H-bridge circuit may remain closed, some switches of the H-bridge circuit may remain open, or some switches of the H-bridge circuit may switch between closed and open states. For example, an H-bridge may repeatedly switch between two switch configurations, with one half-bridge of the H-bridge remaining in the same state for the two switch configurations and the other half-bridge of the H-bridge changing state between the two switch configurations.

[0037] Advantageously, the repeated switching between particular switch configurations of the H-bridge circuit controlled by the switch control circuit can result in a lower voltage swing across the resonant tank of the wireless charging pad (e.g., a ground pad and / or a vehicle pad), thereby enabling the wireless charging pad to charge the battery pack under a relatively wide voltage range (e.g., 200V to 800V or 200V to 1000V). Furthermore, fewer switching events associated with switching between particular switch configurations controlled by the switch control circuit can result in less energy loss.

[0038] 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 or vehicle pad) can wirelessly (e.g., by induction) transmit power received from an external source, such as a power grid or a solar cell, to the electric vehicle. To charge the electric vehicle, a grounding pad can be placed under the vehicle pad of the electric vehicle. A wireless charging direct current (DC) / DC converter (also called an integrated DC / DC power converter) can include a DC / alternating current (AC) inverter in the grounding pad and an AC / DC rectifier in the vehicle pad. Power can be transmitted wirelessly from the grounding pad to the vehicle pad.

[0039] A wireless charging system can be used to wirelessly charge a vehicle under various operating environments or conditions, such as aligned or misaligned parking positions and / or one or more different vehicle power receiving platforms, air gaps, vehicle metal bodies, battery voltages, coupling coefficients, or coil inductance values. Some wireless charging systems use additional hardware to wirelessly charge a vehicle under different conditions. For example, some wireless charging systems may include additional hardware to accommodate a relatively wide battery or power supply voltage range (e.g., 200 V, 400 V, 800 V, etc.). The additional hardware may increase the cost of building a wireless charging system. Furthermore, achieving efficient wireless power transfer to a vehicle may be difficult due to energy losses resulting from the switching of several power electronics within the wireless charging pad. For example, the switches of an H-bridge circuit within the wireless charging pad may switch frequently, resulting in dead-time losses.

[0040] To address at least some of the above technical problems, some embodiments of the present disclosure disclose a wireless charging pad capable of charging a battery pack over a wide voltage range by controlling switches in an H-bridge circuit to switch between specific configurations. As described above, when transitioning from one configuration to another, a switch control circuit can control some switches in the H-bridge circuit to switch and other switches in the H-bridge circuit not to switch, rather than cyclically switching each switch in the H-bridge circuit.

[0041] In some embodiments, the switch control circuit can control a first switch and a second switch disposed in one half bridge of the H-bridge circuit to switch between an open state and a closed state. The switch control circuit can also control a third switch and a fourth switch disposed in the other half bridge of the H-bridge circuit not to switch. For example, the switch control circuit can control the H-bridge circuit to operate in a first switch configuration and a second switch configuration. In the first switch configuration, the first switch is closed, the second switch is open, the third switch is closed, and the fourth switch is open. When transitioning from the first configuration to the second switch configuration, the first switch opens, the second switch closes, the third switch remains closed, and the fourth switch remains open.

[0042] Compared to a situation in which each of the first switch, the second switch, the third switch, and the fourth switch is controlled to periodically switch between an open state and a closed state, controlling the H-bridge circuit to operate under the first switch configuration and the second switch configuration can result in a lower voltage swing (e.g., a 50% reduction) across the resonant tank of the wireless charging pad, thereby enabling the wireless charging pad to charge the battery pack under a relatively wide voltage range (e.g., 200V to 800V or 200V to 1000V). More specifically, the lower voltage swing can be attributed to the resonant tank's ability to maintain a more stable voltage when fewer switches are switching, as opposed to switching all of the switches in the switching circuit (e.g., the H-bridge circuit). Stability can reduce transient effects and / or energy dissipation. Furthermore, fewer switching events associated with switching between the first and second switch configurations controlled by the switch control circuit can result in less energy loss, such as dead-time loss. In some examples, the switching techniques of the present disclosure (e.g., controlling an H-bridge circuit to operate under a first switch configuration and a second switch configuration) may be applicable to capacitive power transfer (e.g., power transfer based on electric field coupling rather than magnetic field coupling).

[0043] In some embodiments, the switch control circuit may initially control the H-bridge circuit such that each of the first switch, the second switch, the third switch, and the fourth switch periodically switches between a closed state and an open state. Upon detecting one or more conditions, the switch control circuit may control the H-bridge circuit to switch between the first switch configuration and the second switch configuration, or to switch between other switch configurations such that some switches remain open or closed when switching between the other switch configurations. In some embodiments, the one or more conditions may include, but are not limited to, a lighter load interfaced with the H-bridge circuit, a lower voltage range or a higher voltage range associated with a battery pack or power source being charged. Alternatively or additionally, the one or more conditions may include one or more of: a battery voltage being within a particular range (e.g., due to different voltage levels of multiple battery packs or different levels of state of charge of the battery packs); a voltage supplied to the ground pad being within a particular range; a predetermined power level being within a particular range; a coupling coefficient associated with an H-bridge circuit being within a particular range; a parking inaccuracy being within a particular range; or a measured inductance variation being within a particular range.

[0044] While various aspects are described according to exemplary embodiments and combinations of features, those skilled in the art will understand that the examples and combinations of features are exemplary in nature and should not be construed as necessarily 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 H-bridge circuits for charging batteries and / or battery packs under different voltage levels are described, such exemplary H-bridge circuit schematic diagrams should not be construed as necessarily 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, communication or exemplary interaction between vehicles, owners / users, and wireless battery charging systems. Wireless Charging Overview

[0045] Generally, inductive charging, commonly referred to as wireless charging, is a type of wireless power transfer. Inductive charging uses electromagnetic induction to generate or deliver 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 the need for precise alignment or electrical contact, a physical dock, an electrical plug, or the like. Such devices include, but are not limited to, vehicles, manufacturing equipment, home appliances, medical devices, and the like.

[0046] 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 transmission component that may be configured as a charging station or charging pad. A charging pad for wirelessly transferring power to a vehicle may be referred to as a grounding pad. An alternating current (AC) current from a power source (e.g., input current) passes through an induction coil in the charging station or pad. Based on the input current, moving charges through the induction coil (e.g., grounding pad coil) generate (or elicit) 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 AC current in an induction coil (e.g., vehicle pad coil) on a power receiving device. The induced AC current in the power receiving device can then pass through a rectifier to convert the induced AC current to DC current. Finally, the power receiving vehicle may include additional charging components and / or systems that utilize the converted DC current to charge a battery system, provide operating power, or a combination thereof.

[0047] If an exemplary inductive charging system uses resonant inductive coupling components / techniques, a greater 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 matches the resonant frequencies. Additionally, this matching frequency can be further selected based on the typical distance between the power transmitting device and the power receiving device, taking peak efficiency into consideration. Furthermore, the use of other materials for the receiver coil, such as silver-plated copper or possibly aluminum, to minimize weight and reduce resistance can be utilized for energy transfer efficiency purposes.

[0048] FIG. 1A illustrates an environment 100 for implementing an inductive-based wireless charging system in accordance with various aspects of the present application. Environment 100 may illustratively correspond to a commercial implementation, such as a parking lot, parking stall, or charging booth. 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 in accordance with an inductive charging methodology. As also shown in FIG. 1A , grounding pad 102, which may also be referred to as a power transmission component, may correspond to a standalone component that may be mountable or positionable on a floor 104 or other flat surface. In some other embodiments, grounding pad 102 may be integrated or combined with other devices or components.

[0049] 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 alternating current as described herein. The grounding pad 102 may 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.

[0050] As shown in FIG. 1A , in some embodiments, the grounding pad 102 corresponds to a form factor that allows it to be positioned on the floor 104 for wireless charging in a vehicle having a vehicle pad coil. The grounding pad 102 may have a form factor that allows the vehicle to be 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 so 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, or a maximum distance between the grounding pad coil and the vehicle pad coil. In some embodiments, the vehicle pad and / or grounding pad 102 (or a combination) may be configured with additional components to adjust such distance (e.g., statically and / or dynamically) or to change the relative orientation between the grounding pad 102 and the vehicle.

[0051] 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 1000 volts, such as in the range of approximately 200 volts to 800 volts. The grounding pad 102 can wirelessly transmit sufficient power to charge a battery pack at such voltages.

[0052] 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 as being directly connected to the energy sources 110, at least a portion of the input AC current may be provided by wireless transmission methods. Additionally, in embodiments having multiple power sources, the environment may further include various switching components for selecting energy from individual energy sources 110 or combinations of energy sources 110.

[0053] 1C shows a block diagram of a ground pad 102 that can function as a 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 an energy source 110. As shown in FIG. 1C, the input current can be provided by a direct electrical connection 106.

[0054] In some embodiments, the ground pad 102 can further include various sensor components 124A, 124B, 124C, 124D related to the charging process. By way of example, the sensor components 124A, 124B, 124C, 124D can be configured for various functions such as vehicle 112 detection, object detection, vehicle distance measurement, environmental sensors (e.g., temperature sensors, humidity sensors), pressure sensors, etc. In one embodiment, the sensor components 124A, 124B, 124C, 124D can include radar sensors. The sensor components 124A, 124B, 124C, 124D can include logic and processing components related to the charging process, including operational measurements, operational control, safety measurements, communication components, etc. Wireless charging system with an H-bridge circuit

[0055] 2A-2D show circuit schematics of exemplary wireless charging systems 200A-200D. As shown in FIGS. 2A-2D, each of wireless charging systems 200A-200D can include a ground pad (e.g., ground pad 102) and a vehicle pad attached to or integrated with the vehicle. For example, the ground pad of wireless charging system 200A can include capacitor 212A, H-bridge circuit 202A, and resonant tank 204A, as shown in FIG. 2A. The vehicle pad of wireless charging system 200A can include capacitor 214A, H-bridge circuit 208A, and resonant tank 206A, as shown in FIG. 2A. In some embodiments, power can be transferred from a power source (not shown in FIG. 2A) to a vehicle battery pack (not shown in FIG. 2A) via H-bridge circuit 202A, resonant tank 204A, resonant tank 206A, and H-bridge circuit 208A. This power transfer may include wireless power transfer from the ground pad coil L1 to the vehicle pad coil L2. Any of the wireless charging systems 200A-200D may be implemented according to any suitable principles and advantages disclosed herein.

[0056] 2A shows a circuit schematic diagram of a wireless charging system 200A. As shown in FIG. 2A, the wireless charging system 200A corresponds to an LCC-LCC circuit architecture. As shown, the wireless charging system 200A includes a capacitor 212A, an H-bridge circuit 202A, a resonant tank 204A, a resonant tank 206A, an H-bridge circuit 208A, and a capacitor 214A. In the LCC-LCC circuit architecture, an inductor L f1 and capacitor C f1 and C1 are coupled between the H-bridge circuit 202A and the ground pad coil L1 in the ground pad, and inductor L f2 and capacitor C f2 and C2 are coupled between the H-bridge circuit 208A and a vehicle pad coil L2 in the vehicle pad.

[0057] 2B shows a circuit schematic diagram of a wireless charging system 200B. As shown in FIG. 2B, the wireless charging system 200B corresponds to an LCC-series circuit architecture. As shown, the wireless charging system 200B includes a capacitor 212B, an H-bridge circuit 202B, a resonant tank 204B, a resonant tank 206B, an H-bridge circuit 208B, and a capacitor 214B. In the LCC-series circuit architecture, an inductor L f1 and capacitor C f1 and C1 are coupled between the H-bridge circuit 202A and the ground pad coil L1 in the ground pad, and a series capacitor C2 is coupled between the H-bridge circuit 208A and the vehicle pad coil L2 in the vehicle pad.

[0058] 2C shows a circuit schematic diagram of wireless charging system 200C. As shown in FIG. 2C, wireless charging system 200C corresponds to a series-LCC circuit architecture. As shown, wireless charging system 200C includes capacitor 212C, H-bridge circuit 202C, resonant tank 204C, resonant tank 206C, H-bridge circuit 208C, and capacitor 214C. In the series-LCC circuit architecture, a series capacitor C1 is coupled between H-bridge circuit 202A and ground pad coil L1 in the ground pad, and an inductor L f2 and capacitor C f2 and C2 are coupled between the H-bridge circuit 208A and a vehicle pad coil L2 in the vehicle pad.

[0059] 2D shows a circuit schematic diagram of wireless charging system 200D. As shown in FIG. 2D, wireless charging system 200D corresponds to a series-series circuit architecture. As shown, wireless charging system 200D includes capacitor 212D, H-bridge circuit 202D, resonant tank 204D, resonant tank 206D, H-bridge circuit 208D, and capacitor 214D. In the series-series circuit architecture, series capacitor C1 is coupled between H-bridge circuit 202A and ground pad coil L1 in the ground pad, and series capacitor C2 is coupled between H-bridge circuit 208A and vehicle pad coil L2 in the vehicle pad. Exemplary Wireless Charging Pad

[0060] 3 illustrates an exemplary wireless charging pad 300 according to some embodiments of the present disclosure. The wireless charging pad 300 includes an H-bridge circuit 322, a resonant tank 324, and a switch control circuit 326. The wireless charging pad 300 can charge a vehicle's battery pack over a relatively wide voltage range by switching the switches in the H-bridge circuit 322. Any suitable principles and advantages of the wireless charging pad 300 can be implemented in an environment according to any suitable principles and advantages of FIGS. 1A-1C.

[0061] Wireless charging pad 300 may be mounted on any ground pad or vehicle pad of wireless charging systems 200A-200D to extend the operable voltage range and / or improve wireless charging efficiency. For example, wireless charging pad 300 may be the ground pad and / or vehicle pad of any of wireless charging systems 200A-200D. In some embodiments, H-bridge circuit 322 may correspond to any of H-bridge circuit 202A, H-bridge circuit 208A, H-bridge circuit 202B, H-bridge circuit 208B, H-bridge circuit 202C, H-bridge circuit 208C, H-bridge circuit 202D, and H-bridge circuit 208D. Resonant tank 324 may correspond to any of resonant tank 204A, resonant tank 206A, resonant tank 204B, resonant tank 206B, resonant tank 204C, resonant tank 206C, resonant tank 204D, and resonant tank 206D.

[0062] 4A-4D, the H-bridge circuit 322 may include switches 322-1, 322-2, 322-3, and 322-4. In some embodiments, rather than periodically switching each of the switches 322-1, 322-2, 322-3, and 322-4, the switch control circuit 326 may control some of the switches 322-1, 322-2, 322-3, and 322-4 to periodically switch between an open state and a closed state, and some of the switches 322-1, 322-2, 322-3, and 322-4 to remain open or closed without switching. Thus, as shown in FIGS. 5A-5C, the voltage amplitude across the resonant tank 324 may be reduced compared to other switching schemes, allowing the wireless charging pad 300 to charge the battery pack under a wider voltage range.

[0063] The switch control circuit 326 can provide control signals for controlling the states of the switches of the H-bridge circuit 322 (e.g., switches 322-1 to 322-4 in FIGS. 4A to 4D). The switch control circuit 326 can be implemented by any suitable circuit for controlling the states of the switches of the H-bridge circuit 322. If the switches of the H-bridge circuit 322 have gates (e.g., the switches are FETs or IGBTs), the switch control circuit 326 can provide control signals to the gates of the H-bridge. In such cases, the switch control circuit 326 can be referred to as a gate drive circuit.

[0064] In some other examples, any other suitable type of switching circuit (e.g., a switching circuit including two stacked half-bridge circuits) may be implemented in place of H-bridge circuit 322. For example, switch control circuit 326 may control some switches of the switching circuit to switch and other switches of the switching circuit not to switch during transitions between states of the switching circuit to wirelessly charge a vehicle, according to any suitable principles and advantages disclosed herein. Any suitable principles and advantages disclosed herein with reference to an H-bridge circuit may be applied to any other suitable switching circuit. Exemplary H-Bridge Switch Configuration

[0065] 4A-4D illustrate example switch configurations of an H-bridge circuit 322 that may be controlled by a switch control circuit 326, according to some embodiments of the present disclosure. FIG. 4A illustrates that the H-bridge circuit 322 may be configured by the switch control circuit 326 into switch configuration 410, which may be referred to as a positive configuration. FIG. 4B illustrates that the H-bridge circuit 322 may be configured by the switch control circuit 326 into switch configuration 420, which may be referred to as a negative configuration. FIG. 4C illustrates that the H-bridge circuit 322 may be configured by the switch control circuit 326 into switch configuration 430, which may be referred to as a zero-one configuration. FIG. 4D illustrates that the H-bridge circuit 322 may be configured by the switch control circuit 326 into switch configuration 440, which may be referred to as a zero-two configuration.

[0066] The H-bridge circuit 322 includes four switches: 322-1, 322-2, 322-3, and 322-4. These switches may be any suitable switches for power electronics, such as n-type field-effect transistors configured to switch voltages sufficient for wireless charging as disclosed herein. In some applications, the H-bridge circuit 322 may include metal-oxide field-effect transistors (MOSFETs). Alternatively or additionally, the H-bridge circuit 322 may include insulated-gate bipolar transistors (IGBTs). The switches of the H-bridge circuit 322 may be configured to pass hundreds of volts. The H-bridge circuit 322 includes a first half-bridge and a second half-bridge. The first half-bridge includes switches 322-1 and 322-2. The second half-bridge includes switches 322-3 and 322-4.

[0067] As shown in Figure 4A, in switch configuration 410, switch 322-1 is closed, switch 322-2 is open, switch 322-3 is closed, and switch 322-4 is open. As shown in Figure 4B, in switch configuration 420, switch 322-1 is open, switch 322-2 is closed, switch 322-3 is open, and switch 322-4 is closed. As shown in Figure 4C, in switch configuration 430, switch 322-1 is open, switch 322-2 is closed, switch 322-3 is closed, and switch 322-4 is open. As shown in Figure 4D, in switch configuration 440, switch 322-1 is closed, switch 322-2 is open, switch 322-3 is open, and switch 322-4 is closed.

[0068] In some embodiments, switch control circuit 326 can control the H-bridge circuit to switch between switch configurations 410 and 430 or between switch configurations 420 and 440, rather than switching between switch configurations 410 and 420. Compared to switching between switch configurations 410 and 420, switching between switch configurations 410 and 430 or between switch configurations 420 and 440 can result in a smaller (e.g., 50% reduced) voltage swing across the resonant tank (e.g., resonant tank 324 in FIG. 3 ) such that a wireless charging pad (e.g., wireless charging pad 300) can be used to charge a battery pack under a wider voltage range (e.g., between 200V and 800V or between 200V and 800V). When switching between switch configurations 410 and 430, the switches in the second half-bridge remain in the same state, and the switches in the first half-bridge change state. Similarly, the switches in the first half-bridge remain in the same state while the switches in the second half-bridge change state when switching between switch configurations 420 and 440. Additionally, fewer switching events compared to switching between switch configurations 410 and 420 may result in less energy losses, such as less dead-time losses.

[0069] In some embodiments, switch control circuit 326 may initially control H-bridge circuit 322 to switch between switch configuration 410 and switch configuration 420. Upon detecting one or more conditions, switch control circuit 326 may control H-bridge circuit 322 to switch between switch configuration 410 and switch configuration 430 or between switch configuration 420 and switch configuration 440, such that switches in only one half-bridge of the H-bridge change state during switching between the two switch configurations. In some embodiments, the one or more conditions may include, but are not limited to, one or more of a lighter load interfaced with H-bridge circuit 322, a lower voltage range associated with the battery pack or power source, or a higher voltage range associated with the battery pack or power source being charged. Alternatively or additionally, the one or more conditions may include one or more of: the battery voltage being within a particular range (e.g., due to different voltage levels of multiple battery packs or different levels of state of charge of the battery packs); the voltage supplied to the ground pad being within a particular range; the predetermined power level being within a particular range; the coupling coefficient associated with the H-bridge circuit 322 being within a particular range; the parking inaccuracy being within a particular range; or the measured inductance variation being within a particular range. Example Voltage Amplitude Waveform

[0070] The H-bridge circuit of the present disclosure can be repeatedly switched between two switch configurations. Examples of switching between the two switch configurations are described with reference to FIGS. 5A-6. Such switching between the two switch configurations can be performed by an H-bridge circuit on the ground pad, an H-bridge circuit on the vehicle pad, or an H-bridge circuit on both the ground pad and the vehicle pad. In some cases, such switching between the two switch configurations can be performed by an H-bridge circuit on the ground pad, where the vehicle pad may have a different switching circuit topology. According to some other examples, such switching between the two switch configurations can be performed by an H-bridge circuit on the vehicle pad, where the ground pad may have a different switching circuit topology.

[0071] 5A shows example waveforms 550A and 560A associated with the operation of the wireless charging pad 300 of FIG. 3 in accordance with some embodiments of the present disclosure. More specifically, waveforms 550A and 560A show the voltage amplitude and voltage across the resonant tank 324 as the H-bridge circuit 322 switches between various switch configurations. The voltage across the resonant tank 324 can correspond to either the voltage v1 associated with the resonant tank 204A, the resonant tank 204B, the resonant tank 204C, and the resonant tank 204D (shown in FIGS. 2A-2D ) or the voltage v2 associated with the resonant tank 206A, the resonant tank 206B, the resonant tank 206C, and the resonant tank 206D (shown in FIGS. 2A-2D ). Waveform 550A shows that the voltage amplitude across the resonant tank 324 can be 2V as the H-bridge circuit 322 switches between switch configuration 410 and switch configuration 420. In contrast, waveform 560A shows that the voltage amplitude across resonant tank 324 when H-bridge circuit 322 switches between switch configuration 410 and a zero switch configuration (switch configuration 430 or switch configuration 440) can be v.

[0072] Waveform 550A is associated with H-bridge circuit 322 repeatedly switching between switch configuration 410 and switch configuration 420. When H-bridge circuit 322 is in switch configuration 410, the voltage across resonant tank 324 may be approximately v. When H-bridge circuit 322 is in switch configuration 420, the voltage across resonant tank 324 may be approximately −v. In some embodiments, v may be in the range of 200V to 400V.

[0073] Waveform 560A is associated with H-bridge circuit 322 repeatedly switching between switch configuration 410 and switch configuration 430 or switch configuration 440. When H-bridge circuit 322 is in switch configuration 410, the voltage across resonant tank 324 may be approximately v. When H-bridge circuit 322 is in switch configuration 430 or switch configuration 440, the voltage across resonant tank 324 may be approximately zero (e.g., ground voltage).

[0074] FIG. 5B shows example waveforms 550A and 560B associated with the operation of the wireless charging pad 300, according to some embodiments of the present disclosure.

[0075] As described above, waveform 550A is associated with H-bridge circuit 322 switching between switch configuration 410 and switch configuration 420. When H-bridge circuit 322 is in switch configuration 410, the voltage across resonant tank 324 may be approximately v. When H-bridge circuit 322 is in switch configuration 420, the voltage across resonant tank 324 may be approximately −v.

[0076] Waveform 560B is associated with H-bridge circuit 322 switching between a zero switch configuration (switch configuration 440 or switch configuration 430) and switch configuration 420. When H-bridge circuit 322 is in switch configuration 420, the voltage across resonant tank 324 may be approximately -v. When H-bridge circuit 322 is in switch configuration 440 or switch configuration 430, the voltage across resonant tank 324 may be approximately 0 (e.g., ground). Waveform 560B is similar to waveform 560A, except that waveform 560B switches between v and 0, while waveform 560B switches between -v and 0. Both waveforms 560A and 560B have a voltage switch of magnitude v.

[0077] FIG. 5C shows example waveforms 550C and 560A associated with the operation of the wireless charging pad 300, according to some embodiments of the present disclosure.

[0078] Waveform 550C is associated with H-bridge circuit 322 switching between switch configuration 410, switch configuration 420, and switch configuration 430. When H-bridge circuit 322 is in switch configuration 410, the voltage across resonant tank 324 may be approximately v. When H-bridge circuit 322 is in switch configuration 420, the voltage across resonant tank 324 may be approximately -v. When H-bridge circuit 322 is in switch configuration 430, the voltage across resonant tank 324 may be approximately 0. In waveform 550C, switching between voltage configurations results in a voltage switch of magnitude v, and the total voltage amplitude of the waveform is 2v.

[0079] As described above, waveform 560A is associated with H-bridge circuit 322 switching between switch configuration 410 and switch configuration 430. When H-bridge circuit 322 is in switch configuration 410, the voltage across resonant tank 324 may be approximately v. When H-bridge circuit 322 is in switch configuration 430, the voltage across resonant tank 324 may be approximately 0 (e.g., ground).

[0080] In some embodiments, switch control circuit 326 can control H-bridge circuit 322 to alternately switch between switch configuration 440 and switch configuration 420 or between switch configuration 410 and switch configuration 430 without switching between switch configuration 410 and switch configuration 420. Compared to switching between switch configuration 410 and switch configuration 420, the voltage amplitude across resonant tank 324 can be reduced by approximately 50%, as shown by waveforms 560A and 560B, thereby enabling wireless charging under a wider voltage range. At the same time, the duty cycle can remain unchanged. Furthermore, wireless power transfer via wireless charging pad 300 can be more efficient in some applications due to fewer switching events due to the lack of switching between switch configuration 410 and switch configuration 420.

[0081] 6 shows example waveforms 660 and 670 associated with the operation of the wireless charging pad 300, in accordance with some embodiments of the present disclosure. More specifically, waveforms 660 and 670 illustrate the various duty cycles associated with the voltage across the resonant tank 324 as the H-bridge circuit 322 switches between switch configuration 410 and switch configuration 430.

[0082] Waveform 660 illustrates that, in each switching cycle, H-bridge circuit 322 may be in switch configuration 410 longer than switch configuration 430. Waveform 670 illustrates that, in each switching cycle, H-bridge circuit 322 may be in switch configuration 430 longer than switch configuration 410. Waveforms 660 and 670 illustrate that switching between switching configurations, where one half-bridge of the H-bridge switches state and the other half-bridge remains unchanged, can be performed at different duty cycles. Switching between switch configurations 410 and 430 can be performed at any suitable duty cycle. Similarly, switching between switch configurations 420 and 440 can be performed at any suitable duty cycle. In some cases, the H-bridge circuit may repeatedly switch between two switch configurations such that the two switch configurations have unequal duty cycles. conclusion

[0083] The foregoing disclosure is not intended to limit the disclosure to the precise form or particular field of use disclosed. Accordingly, various alternative embodiments and / or modifications to the disclosure, whether expressly described or implied herein, are contemplated as possible 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 in form and detail can be made without departing from the scope of the present disclosure. Accordingly, the present disclosure is limited only by the scope of the claims.

[0084] It is to be understood that not necessarily all objectives or advantages may be achieved in accordance with any particular example described herein. Thus, for example, those skilled in the art will understand that some examples may be implemented to achieve or optimize one or more advantages as taught herein without necessarily achieving other objectives or advantages as may be taught or suggested herein.

[0085] All of the processes described herein may be embodied and fully automated via software code modules executed by a computing system including a computer or processor. The code modules may be stored on any type of non-transitory computer-readable medium or other computer storage device. Some or all of the methods may be implemented in dedicated computer hardware.

[0086] Many other variations beyond those described herein will be apparent from this disclosure. For example, depending on the example, certain acts, events, or functions of any of the algorithms described herein may be performed in a different order, added, combined, or omitted entirely (e.g., not all acts or events described may be required to implement an algorithm). Furthermore, in some examples, acts or events may be performed simultaneously rather than sequentially, for example, via multithreading, interrupt processing, or multiple processors or processor cores, or on other parallel architectures. Furthermore, different tasks or processes may be performed by different machines and / or computing systems that can function together.

[0087] The various illustrative logic blocks and modules described in connection with the examples 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 for processing computer-executable instructions. In some examples, 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, e.g., a combination of a DSP and a microprocessor, multiple microprocessors, a microprocessor in combination with a DSP core, or any other such configuration. While 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.

[0088] Elements of the methods, processes, routines, or algorithms 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. The 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.

[0089] 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 in multiple computing devices and / or multiple processors, either serially or in parallel.

[0090] In particular, conditional language such as "can," "could," "might," or "may" is understood within the context in which it is generally used to convey that some examples include certain features, elements, and / or steps, while other examples do not, unless otherwise specified. Thus, such conditional language generally does not imply that the features, elements, and / or steps are in any way exemplary, or that the examples necessarily include logic for determining whether those features, elements, and / or steps should be included in or performed in any particular example, with or without user input or prompting.

[0091] Disjunctive language such as the phrase "at least one of X, Y, and Z" is understood in its commonly used context, unless otherwise indicated, 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). Thus, such disjunctive language is not intended to, and should not, generally imply that some instances require at least one of X, at least one of Y, and at least one of Z, respectively, to exist.

[0092] Any process descriptions, elements, or blocks in the flow diagrams described herein and / or shown in the accompanying drawings should 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. As will be appreciated by those skilled in the art, alternative examples are included within the scope of the examples described herein in which elements or functions may be omitted, performed, or described in a different order than that shown or described, including substantially simultaneously or in reverse order, depending on the functionality involved.

[0093] It should be emphasized that many variations and modifications can be made to the above examples, and that these elements should be understood as being among other acceptable examples, and all such modifications and variations are intended to be included within the scope of this disclosure.

[0094] Any process descriptions, elements, or blocks in the flow diagrams described herein and / or shown in the accompanying drawings should be understood as potentially representing modules, segments, or portions of code containing executable instructions for implementing specific logical functions or elements in the process. As will be appreciated by those skilled in the art, alternative implementations in which elements or functions may be omitted, performed, or described in a different order than that shown or described, including substantially simultaneously or in reverse order, depending on the functionality involved, are included within the scope of the examples described herein.

[0095] Unless otherwise specified, articles such as "a" or "an" should generally be construed to include one or more described items. Thus, phrases such as "a device configured to" are intended to include one or more described devices. Such one or more described devices can also be collectively configured to perform the stated description. For example, "a processor configured to perform descriptions A, B, and C" can include a first processor configured to perform description A working in conjunction with a second processor configured to perform descriptions B and C.

Claims

1. 1. A method of wireless power transmission, comprising: energizing a first wireless charging pad, the first wireless charging pad including a switching circuit; repeatedly switching the switching circuit between a first switch configuration and a second switch configuration, wherein switches of a first half-bridge of the switching circuit change state between the first switch configuration and the second switch configuration, and switches of a second half-bridge of the switching circuit remain in the same state in the first switch configuration and the second switch configuration; using a voltage generated by the repetitive switching to cause wireless power transfer from the first wireless charging pad to a second wireless charging pad; A method comprising:

2. detecting one or more conditions; The method of claim 1 , wherein the repeated switching is performed in response to detecting the one or more conditions.

3. 3. The method of claim 2, wherein the one or more conditions relate to at least one of a load interfaced with the switching circuit, a voltage of a battery pack of a vehicle including the second wireless charging pad, or a voltage of a power source associated with the first wireless charging pad.

4. 10. The method of claim 1, wherein a vehicle includes the second wireless charging pad and the voltage of a battery pack of the vehicle is in the range of 200 volts to 1000 volts.

5. The method of claim 1 , wherein there is an unequal duty cycle between the first switch configuration and the second switch configuration due to the repetitive switching.

6. 2. The method of claim 1, wherein the repetitive switching of the switching circuit between the first switch configuration and the second switch configuration results in a lower voltage swing across a resonant tank of the first wireless charging pad electrically connected to the switching circuit compared to switching of the switching circuit between a third switch configuration, the first switch configuration, and the second switch configuration.

7. The method of claim 1 , wherein the switching circuit comprises an H-bridge circuit.

8. 1. A method of wireless power transmission, comprising: receiving power wirelessly from a ground pad at a vehicle pad of the vehicle, the vehicle pad including a switching circuit; repeatedly switching the switching circuit between a first switch configuration and a second switch configuration, wherein switches of a first half-bridge of the switching circuit change state between the first switch configuration and the second switch configuration, and switches of a second half-bridge of the switching circuit are in the same state in both the first switch configuration and the second switch configuration; A method comprising:

9. detecting one or more conditions; The method of claim 8 , wherein the repeated switching is performed in response to detecting the one or more conditions.

10. 10. The method of claim 9, wherein the one or more conditions relate to at least one of a load interfaced with the switching circuit, a voltage range of a battery pack of the vehicle, or a voltage range of a power source associated with the ground pad.

11. 9. The method of claim 8, wherein the voltage range of the vehicle's battery pack is within the range of 200 volts to 1000 volts.

12. The method of claim 8 , wherein there is an unequal duty cycle between the first switch configuration and the second switch configuration due to the repetitive switching.

13. 9. The method of claim 8, wherein the repeated switching of the switching circuit between the first switch configuration and the second switch configuration results in a lower voltage swing across a resonant tank of the vehicle pad electrically connected to the switching circuit compared to switching of the switching circuit between a third switch configuration, the first switch configuration, and the second switch configuration.

14. The method of claim 8 , further comprising charging a battery pack of the vehicle based on the power received wirelessly from the ground pad.

15. A wireless charging pad, a switching circuit including a first half bridge and a second half bridge; a resonant tank electrically connected to the switching circuit, the resonant tank including a coil arranged for wireless power transmission; a switch control circuit configured to repeatedly switch the switching circuit between a first switch configuration and a second switch configuration, the first half-bridge changing state between the first switch configuration and the second switch configuration, and the second half-bridge being in the same state in both the first switch configuration and the second switch configuration; Equipped with The wireless charging pad is configured to transmit sufficient wireless power to charge a battery pack at an operating voltage of at least 350 volts.

16. 16. The wireless charging pad of claim 15, wherein the switch control circuit is further configured to detect one or more conditions, and wherein the switch control circuit is configured to repeatedly switch the switching circuit between the first switch configuration and the second switch configuration in response to detecting the one or more conditions.

17. 17. The wireless charging pad of claim 16, wherein the one or more conditions relate to at least one of a load interfaced with the switching circuit, a voltage range of a vehicle battery pack, or a voltage range of a power source associated with the wireless charging pad.

18. The wireless charging pad of claim 15 , wherein the wireless charging pad is a grounding pad.

19. 16. The wireless charging pad of claim 15, wherein the repetitive switching of the switching circuit between the first switch configuration and the second switch configuration results in a lower voltage swing across the resonant tank compared to switching of the switching circuit between a third switch configuration, the first switch configuration, and the second switch configuration.

20. 16. The wireless charging pad of claim 15, wherein the switching circuit comprises an H-bridge circuit.

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