Tunable impedance circuit for wireless charging device

Abstract

The invention relates to a tunable impedance circuit for a wireless charging device. The wireless charging pad may include a switching circuit, a resonant tank, and an impedance control circuit. The resonant tank may have a resonant frequency and be electrically connected to the switching circuit. The resonant tank may include a coil arranged for wireless power transfer and a tunable impedance circuit. The impedance control circuit may be configured to adjust an impedance of the tunable impedance circuit to adjust a resonant frequency of the resonant tank.

Description

Cross-references

[0001] This application claims priority to U.S. Provisional Patent Application No. 63 / 705,359, filed October 9, 2024, entitled “Tunable Impedance Circuit for Wireless Charging Device,” and U.S. Patent Application No. 19 / 324,982, filed September 10, 2025, entitled “Tunable Impedance Circuit for Wireless Charging Device,” the technical disclosures of which are incorporated herein by reference in their entirety and for all purposes. Technical Field

[0002] This disclosure relates to systems and methods for wireless charging. More specifically, embodiments of the invention relate to efficient wireless power transfer between a wireless power transmitter and a receiver by adjusting impedance. Background Technology

[0003] Batteries are components in a wide range of battery-powered devices, components, or various transportation platforms, such as electric vehicles, robots, electric bicycles, electric motorcycles, drones, and many other types of equipment. Batteries can be paired with wireless charging devices and arranged to receive energy via electromagnetic coupling with the wireless charging device through a receiver pad. Specifically, the wireless charging device can use one or more internal coils to sense electromagnetic fields, and one or more corresponding receiver coils connected to the battery can trap these fields within a certain proximity to the charging device. Various technical challenges exist associated with wireless charging. Summary of the Invention

[0004] The systems, methods, and apparatuses of the present invention each have several innovative embodiments, wherein no single embodiment is solely responsible for all the desired properties disclosed herein. Details of one or more implementations of the subject matter described herein are set forth in the accompanying drawings and the following description.

[0005] In some aspects, the technology herein relates to a wireless charging pad comprising: a switching circuit; a resonant circuit having a resonant frequency and electrically connected to the switching circuit, the resonant circuit including a coil arranged for wireless power transmission and including a tunable impedance circuit; and an impedance control circuit configured to adjust the impedance of the tunable impedance circuit to adjust the resonant frequency of the resonant circuit.

[0006] In some aspects, the technology described herein relates to a wireless charging pad in which a tunable impedance circuit includes a switch and a capacitor, and an impedance control circuit is configured to adjust the impedance of the tunable impedance circuit by changing the state of the switch.

[0007] In some respects, the technology described herein relates to a wireless charging pad in which a switch is connected in parallel with a capacitor.

[0008] In some respects, the technology described herein relates to a wireless charging pad in which a switch is connected in series with a capacitor.

[0009] In some aspects, the technology described herein relates to a wireless charging pad in which a tunable impedance circuit comprises a plurality of series circuits connected in parallel with each other, and each series circuit comprises a switch connected in series with a capacitor.

[0010] In some aspects, the technology described herein relates to a wireless charging pad in which a tunable impedance circuit comprises a plurality of parallel circuits connected in series with each other, and each of the parallel circuits comprises a switch connected in parallel with a capacitor.

[0011] In some respects, the technology described herein relates to a wireless charging mat, wherein the wireless charging mat is a floor mat.

[0012] In some respects, the technology described herein relates to a wireless charging mat, wherein the wireless charging mat is a vehicle mat.

[0013] In some respects, the technology described herein relates to a wireless charging pad in which the switching circuitry includes an H-bridge circuit.

[0014] In some aspects, the technology described herein relates to a wireless charging pad in which the switching circuitry includes stacked half-bridge circuitry.

[0015] In some aspects, the technology described herein relates to a wireless charging pad in which an impedance control circuit is configured to adjust impedance based on a mismatch between the resonant frequency of a resonant circuit and the resonant frequency of a second resonant circuit circuit of a second wireless charging pad, the second wireless charging pad being positioned adjacent to the wireless charging pad for wireless charging.

[0016] In some aspects, the technology described herein relates to a wireless charging pad in which a resonant circuit includes a capacitor, and in which a tunable impedance circuit, a coil, and a capacitor are connected in series.

[0017] In some aspects, the technology described herein relates to a wireless charging pad in which a resonant circuit includes a capacitor connected in series with a coil, and in which a tunable impedance circuit is connected in parallel with the coil.

[0018] In some aspects, the technology described herein relates to a wireless charging pad in which the resonant circuit has an LCC architecture and in which a tunable impedance circuit is connected in series with an inductor of the resonant circuit.

[0019] In some aspects, the technology described herein relates to a wireless charging pad in which the resonant circuit has an LCC architecture and in which a tunable impedance circuit is connected in parallel with an inductor of the resonant circuit.

[0020] In some respects, the technology described herein relates to a wireless charging pad in which a tunable impedance circuit is connected in series with a coil.

[0021] In some aspects, the technology described herein relates to a method for wireless power transmission, the method comprising: detecting a mismatch in resonant frequencies between a first resonant circuit of a floor mat and a second resonant circuit of a vehicle mat; adjusting the impedance of a tunable impedance circuit based on the detection to reduce the mismatch in resonant frequencies; and wirelessly transmitting power from the floor mat to the vehicle mat after adjustment.

[0022] In some respects, the techniques described herein relate to a method in which the first resonant circuit of the ground mat includes a tunable impedance circuit.

[0023] In some respects, the techniques described herein relate to a method in which the second resonant circuit of a vehicle includes a tunable impedance circuit.

[0024] In some respects, the techniques described herein involve a method in which a mismatch in resonant frequencies is associated with misalignment between a floor mat and a vehicle mat.

[0025] In some respects, the techniques described herein relate to a method in which a mismatch in resonant frequencies is associated with at least one of a vehicle platform, an object positioned between a floor mat and a vehicle mat, or a manufacturing process.

[0026] In some aspects, the techniques described herein relate to a method in which the tunable impedance circuit includes a switch and a capacitor, and wherein adjusting the impedance includes switching the state of the switch.

[0027] In some aspects, the techniques described herein relate to a method in which the tunable impedance circuit includes a switch and a capacitor, and the adjustment includes changing the state of the switch.

[0028] In some respects, the techniques described herein relate to a method in which the switch is connected in parallel with the capacitor.

[0029] In some respects, the techniques described herein relate to a method in which the switch is connected in series with the capacitor.

[0030] In some aspects, the techniques described herein relate to a method in which the tunable impedance circuit comprises a plurality of series circuits connected in parallel with each other, and each of the series circuits comprises a switch connected in series with a capacitor.

[0031] In some aspects, the techniques described herein relate to a method in which the tunable impedance circuit comprises a plurality of parallel circuits connected in series with each other, and each of the parallel circuits comprises a switch connected in parallel with a capacitor. Attached Figure Description

[0032] These and other features, aspects, and advantages of the invention are described with reference to drawings of certain embodiments. It should be understood that the drawings, which are incorporated in and constitute a part of this specification, are for illustrative purposes and are not drawn to scale.

[0033] Figure 1A An exemplary wireless charging environment in which embodiments of the present disclosure can be implemented is shown.

[0034] Figure 1B This illustrates some embodiments according to the present disclosure. Figure 1A A block diagram of an example wireless charging environment.

[0035] Figure 1C This illustration depicts a floor mat that can function as a wireless charging device according to some embodiments of the present invention.

[0036] Figure 2A-2D An example circuit diagram of a wireless charging system according to some embodiments of the present disclosure is shown.

[0037] Figure 3 Example block diagrams illustrating wireless charging pads according to some embodiments of the present invention.

[0038] Figures 4A-4D Some embodiments according to this disclosure are shown. Figure 3 An exemplary switch configuration for the H-bridge circuit of a wireless charging pad.

[0039] Figures 5A-5E This is an example circuit diagram of a wireless charging system with a tunable impedance circuit according to some embodiments of the present disclosure.

[0040] Figures 6A-6E An example circuit diagram of a tunable impedance circuit for wireless charging according to some embodiments of the present disclosure is shown. Detailed Implementation

[0041] The following detailed description of specific embodiments presents various descriptions of specific embodiments. However, the innovations described herein can be implemented in many different ways, such as those defined and covered by the claims. In this specification, reference is made to the accompanying drawings, wherein the same reference numerals and / or terms may denote the same or functionally similar elements. It should be understood that the elements shown in the figures are not necessarily drawn to scale. Furthermore, it should be understood that some embodiments may include more elements than shown in the figures and / or a subset of the elements shown in the drawings. Additionally, some embodiments may combine any suitable combination of features from two or more figures. The headings provided herein are merely for convenience and do not necessarily affect the scope or meaning of the claims. introduction

[0042] Various aspects of this invention relate to systems and methods for wirelessly charging battery packs via wireless power transfer. This disclosure discloses a wireless charging device including a tunable impedance circuit. The tunable impedance circuit can be specifically designed to adjust the impedance of the wireless power charging system. Illustratively, the tunable impedance circuit can be implemented on the transmitter side and / or receiver side of the wireless charging system. The tunable impedance circuit can adjust the impedance on the transmitter side and / or receiver side to efficiently transfer wireless power.

[0043] Overall, effective wireless power transfer between the transmitter and receiver in a wireless charging system can be achieved by reducing the mismatch in resonant frequencies between the transmitter and receiver sides. For example, if the resonant frequencies of the transmitter and receiver resonant circuits in a wireless charging system are mismatched, the wireless power generated at the transmitter's coil may not be fully (or effectively) transferred to the receiver's coil. Therefore, reducing the mismatch between the transmitter and receiver resonant frequencies is crucial for achieving effective wireless power transfer. The resonant frequency is based on the impedance of the transmitter and receiver in the wireless charging system. For example, tuning the impedance of the resonant circuit of the transmitter or receiver can change the resonant frequency of the resonant circuit. Tuning impedance can include adjusting the capacitance and / or inductance of the resonant circuit. Since the resonant frequency of the resonant circuit can be set based on the capacitance and inductance of the resonant circuit, the tuning impedance can change the resonant frequency of the resonant circuit. Maximum power transfer between the transmitter and receiver in a wireless charging system can be achieved when their resonant frequencies are the same.

[0044] As disclosed herein, a tunable impedance circuit can adjust the resonant frequency of an energy storage circuit before and / or during the wireless charging process. Illustratively, the wireless charging device may incorporate circuitry that generates an AC signal and a transmitter coil that induces an electromagnetic field. An AC signal can be provided to the transmitter coil at a specific resonant frequency. The resonant frequency can be based on the impedance of the tunable impedance circuit of the resonant circuit. When the resonant frequencies of the energy storage circuit, including these coils, are matched, power can be efficiently transferred from the transmitter coil to the receiver coil. The tunable impedance circuit disclosed herein can adjust the impedance in various wireless charging environments.

[0045] In various embodiments, wireless charging devices can be used to charge vehicles, such as electric vehicles with battery packs. In these embodiments, the wireless charging device can be implemented as a ground pad or a vehicle pad. For example, a ground pad can be placed under a vehicle pad of an electric vehicle to charge the electric vehicle. A wireless charging DC / DC converter (also known as an aggregated DC / DC power converter) can include a DC / AC inverter in the ground pad and an AC / DC rectifier in the vehicle pad. Power can be wirelessly transferred from the ground pad to the vehicle pad. In some embodiments, the vehicle pad can also transfer wireless power by receiving DC signals from the vehicle's battery pack. For example, the vehicle pad can receive DC signals from the battery pack and convert them to AC signals by implementing a DC / AC inverter.

[0046] Wireless power transfer in a wireless charging system can be technically limited in its efficiency by factors such as inductance variations that lead to lower efficiency in power transfer between the wireless power transmitting device (e.g., a ground mat) and the wireless power receiving device (e.g., a vehicle mat). Such inductance variations can be caused by a variety of factors, such as misalignment between the charging mat and the vehicle, differences in vehicle platforms (cars, SUVs, trucks, etc.), metallic objects such as steel reinforcement in or under the floor, manufacturing tolerances, etc. This inductance variation can affect the resonant frequency on the ground mat (ground side), and / or the vehicle mat (e.g., the vehicle receiving coil on the vehicle side) can cause mismatch. This resonant frequency mismatch between the ground mat and the vehicle mat can lead to low efficiency in wireless power transfer by drawing higher current, causing the system to draw more current to maintain the same power level, thus increasing energy consumption. This resonant frequency mismatch can also cause a large phase shift. Furthermore, the current waveform between the charging mat and the vehicle mat may become misaligned, resulting in additional energy consumption and higher power loss. The combination of higher current and phase shift can translate into significant energy consumption. This low efficiency reduces the overall effectiveness of the wireless charging system. The inadequacy can also increase costs due to the implementation of larger and more robust electrical and mechanical components to compensate for power loss.

[0047] Typically, both the wireless charging device (e.g., included in a floor mat) and the vehicle's receiving device (e.g., included in a vehicle mat) are incorporated into corresponding resonant circuits with resonant frequencies for wireless power transfer. Matching the resonant frequencies of the resonant circuits can result in efficient wireless power transfer. However, as mentioned above, one or more environmental conditions can cause variations in the resonant frequencies on the charging and / or receiving sides. These mismatched resonant frequencies can be significant contributors to inefficiencies in wireless power transfer.

[0048] To address at least some of the aforementioned technical problems, embodiments of this disclosure relate to circuits and methods for mitigating resonant frequency mismatch and / or inductance variations. This may include reducing the resonant frequency mismatch between energy storage circuits on the ground side (e.g., a ground mat) and the vehicle side (e.g., a vehicle mat). Embodiments of this disclosure provide various configurations of tunable impedance circuits. These tunable impedance circuits have various switching configurations, capacitor array configurations, switch positions, and capacitor array positions in wireless charging systems.

[0049] A tunable impedance circuit can be implemented in the resonant circuit of a floor mat and / or vehicle mat. The tunable impedance circuit can be connected to the transmitting charging coil (e.g., in a floor mat) or receiving coil (e.g., in a vehicle mat) of a wireless charging system. The tunable impedance circuit can affect the resonant frequency of the resonant circuit. Advantageously, the resonant frequency of the resonant circuit can be adjusted for various environmental conditions that may cause inductance changes and resonant frequency mismatch.

[0050] In some embodiments, the tunable impedance circuit can match the resonant frequency of the resonant circuit of the floor mat to the resonant frequency of the resonant circuit of the vehicle mat. For example, the tunable impedance circuit can adjust the resonant frequency of the floor mat's resonant circuit by controlling one or more switches of the tunable impedance circuit to match its resonant frequency to the resonant frequency of the vehicle mat's resonant circuit. In the various examples disclosed herein, each switch of the tunable impedance circuit may include one or more switches, such as metal-oxide-semiconductor field-effect transistors (MOSFETs).

[0051] The tunable impedance circuit can adjust the impedance so that the resonant frequency associated with the capacitance and inductance of the energy storage circuit of the ground mat is approximately equal to the resonant frequency associated with the capacitance and inductance of the energy storage circuit of the vehicle mat, wherein the ground mat and the vehicle mat are coupled for wireless charging.

[0052] The tunable impedance circuit can be adjusted once or multiple times for a wireless charging cycle. The tunable impedance circuit can be adjusted before a wireless charging cycle. Alternatively or additionally, the tunable impedance circuit can be adjusted during a wireless charging cycle. This adjustment can be dynamic or periodic. The tunable impedance circuit can be adjusted based on one or more of the inductance, capacitance, and coupling coefficient of the energy storage circuit. As an example, an adjustable capacitor circuit can be adjusted based on the inductance, capacitance, and coupling coefficient of the energy storage circuit. As another example, an adjustable capacitor circuit can be adjusted based on the inductance of the grooves in the floor mat, the capacitance of the grooves in the floor mat, the coupling coefficient between the floor mat and the vehicle mat, the inductance of the grooves in the vehicle mat, and the capacitance of the grooves in the vehicle mat.

[0053] Various tunable impedance circuit configurations that can be implemented in floor mats and / or vehicle mats are disclosed. These tunable impedance circuits can be configured in various ways by changing the state of one or more switches to adjust the effective impedance of the tunable impedance circuit. For example, in... Figures 6A-6E An example of this configuration is described in [the document / document].

[0054] While various aspects will be described based on combinations of illustrative embodiments and features, those skilled in the art will recognize that these combinations of examples and features are illustrative in nature and should not be construed as limiting. More specifically, aspects of this application are applicable to various types of vehicle charging mechanisms, power supplies, interfaces, etc. Furthermore, although specific tunable impedance circuit configurations will be described, such illustrative configurations should not be construed as limiting. Therefore, those skilled in the art will understand that aspects of this application are not necessarily limited to application to any particular type of vehicle, vehicle charging infrastructure, communication or illustrative interaction between the vehicle, owner / user, and wireless battery charging system. Wireless charging overview

[0055] In general, inductive charging (often called wireless charging) is a form of wireless power transfer. Inductive charging uses electromagnetic induction to generate or otherwise provide power to devices without requiring physical electrical connections. Specifically, various devices can be placed near charging stations or inductive pads without requiring precise alignment or electrical contact, physical docking, plugs, etc. Such devices include, but are not limited to, vehicles, manufacturing equipment, consumer electronics, and medical devices.

[0056] According to various aspects of this application, an inductive charging system is configured to transfer energy via inductive coupling between components. An illustrative charging system includes a transfer component, which can be configured as a charging station or a charging mat. A charging mat for wirelessly transferring power to a vehicle may be referred to as a floor mat. Alternating current (AC) from a power source (e.g., an input current) passes through an induction coil in the charging station or mat. Based on the input current, a magnetic field is generated (or drawn out) by the moving charge in the induction coil (e.g., a floor mat coil). Illustratively, the strength of the magnetic field may fluctuate at least in part according to variations or fluctuations in the amplitude of the input current. The varying magnetic field generates an alternating current in an induction coil (e.g., a vehicle mat coil) on a receiving device. The induced AC in the receiving device can then be converted to direct current (DC) by a rectifier. Finally, the receiving vehicle may include additional charging components and / or systems that utilize the converted DC to charge a battery system, provide operating power, or a combination thereof.

[0057] When the illustrative inductive charging system uses resonant inductive coupling components / techniques, a greater distance can be achieved between the ground mat and the vehicle mat coils. More specifically, in some embodiments, capacitors can be connected to each induction coil to create two LC circuits with a specific resonant frequency. The frequency of the alternating current is matched to the resonant frequency. Furthermore, considering peak efficiency, the matched frequency can be further selected based on the typical distance between the transmitting and receiving devices. Moreover, for energy transfer efficiency purposes, other materials can be used for the receiver coil, such as silver-plated copper or sometimes aluminum, to minimize weight and reduce resistance.

[0058] Figure 1A This is a schematic diagram of an environment 100 for implementing an inductive wireless charging system according to various aspects of this application. Environment 100 can illustratively correspond to a commercial implementation, such as a parking lot, parking space, toll booth, etc. Environment 100 can also correspond to a private or other non-commercial implementation, such as a private residence. As an illustrative example, an implementation of an inductive wireless charging system in a non-commercial manner may include a floor mat 102 configured to generate a variable magnetic field according to an inductive charging method. Furthermore... Figure 1A As shown, the floor mat 102 (which may also be referred to as a transmission component) may correspond to a separate component operable to be installed or placed on the floor 104 or another flat surface. In some other embodiments, the floor mat 102 may be integrated or combined with other devices or components.

[0059] The floor mat 102 can be connected to one or more power sources, such as input from a utility company, real-time power (e.g., solar or wind power), energy storage batteries, or a combination thereof. The power source is configured to provide input AC power as described herein. The floor mat 102 can be connected to the power source via a direct electrical connection 106, for example via a junction box 108 located on the wall surface 118.

[0060] like Figure 1A As shown, in one embodiment, the floor mat 102 corresponds to a shape factor that allows a location on the floor 104 to be wirelessly charged by a vehicle with a vehicle mat coil. The floor mat 102 may have a shape factor that allows the vehicle to be directly positioned above the top surface of the floor mat 102. Illustratively, the dimensions of the floor mat 102 (e.g., the height and width of the floor mat 102) may be configured such that the distance between the top surface of the floor mat 102 and the bottom surface of the vehicle meets specific criteria, such as a minimum distance between the floor mat coil and the vehicle mat coil, a maximum distance between the floor mat coil and the vehicle mat coil, etc. In some embodiments, the vehicle mat and / or the floor mat 102 (or a combination thereof) may be configured with additional components for adjusting (e.g., statically and / or dynamically) this distance or otherwise changing the relative orientation between the floor mat 102 and the vehicle.

[0061] In some embodiments, the floor mat 102 may be configured to charge a vehicle's battery pack, wherein the battery pack may 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 floor mat 102 may be configured to supply 800 volts of DC power. In some embodiments, the floor mat 102 may provide a voltage range from approximately 200 volts to 800 volts. The floor mat 102 may wirelessly transmit sufficient power to charge the battery pack with such a voltage.

[0062] Figure 1B A block diagram of an environment 100 is shown, which includes a wireless charging device 111 (e.g., a floor mat 102) that wirelessly communicates with a vehicle 112, for example, via an inducted 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 input AC power may be provided via a wireless transmission method. Additionally, in embodiments with multiple power sources, the environment may also include various switching components to allow selection of energy from individual energy sources 110 or combinations of energy sources 110.

[0063] Figure 1C It can be used as a wireless charging device 111 ( Figure 1BA block diagram of a floor mat 102 (shown in the diagram). The floor mat 102 may include at least one floor mat coil 122 for generating a magnetic field from an input current supplied from an energy source 110. Figure 1C As shown, the input current can be provided by direct electrical connection 106.

[0064] In some embodiments, the floor mat 102 may further include various sensor components 124A, 124B, 124C, and 124D related to the charging process. For illustration, sensor components 124A, 124B, 124C, and 124D can be configured for various functions, such as vehicle 112 detection, object detection, distance measurement to the vehicle, environmental sensors (e.g., temperature sensors, humidity sensors), pressure sensors, etc. In one embodiment, sensor components 124A, 124B, 124C, and 124D may include radar sensors. Sensor components 124A, 124B, 124C, and 124D may include logic and processing components related to the charging process, including operational measurements, operational control, safety measurements, communication components, etc. Wireless charging system with H-bridge circuit

[0065] Figure 2A-2D A circuit diagram of an exemplary wireless charging system 200A-200D is shown. Figure 2A-2D As shown, each of the wireless charging systems 200A-200D may include a floor mat (e.g., floor mat 102) and a vehicle mat attached to or otherwise integrated with the vehicle. For example, as Figure 2A As shown, the ground mat of the wireless charging system 200A may include a capacitor 212A, an H-bridge circuit 202A, and a resonant circuit 204A. For example, as Figure 2A As shown, the vehicle pad of the wireless charging system 200A may include a capacitor 214A, an H-bridge circuit 208A, and a resonant circuit 206A. In some embodiments, power can be drawn from a power source via the H-bridge circuit 202A, resonant circuit 204A, resonant circuit 206A, and H-bridge circuit 208A. Figure 2A (not shown) transmitted to the vehicle's battery pack ( Figure 2A (Not shown in the image). This power transfer may include wireless power transfer from coil L1 of the ground mat to coil L2 of the vehicle mat. Any of the wireless charging systems 200A to 200D may be implemented in accordance with any suitable principles and advantages disclosed herein.

[0066] Figure 2A A circuit diagram of the wireless charging system 200A is shown. (For example...) Figure 2AAs shown, the wireless charging system 200A corresponds to an LCC-LCC circuit structure. As illustrated, the wireless charging system 200A includes a capacitor 212A, an H-bridge circuit 202A, resonant circuits 204A and 206A, an H-bridge circuit 208A, and a capacitor 214A. In the LCC-LCC circuit structure, inductor Lf1 and capacitors Cf1 and C1 are coupled between the H-bridge circuit 202A and the ground mat coil L1 in the ground mat, while inductor Lf2 and capacitors Cf2 and C2 are coupled between the H-bridge circuit 208A and the vehicle mat coil L2 in the vehicle mat.

[0067] Figure 2B A circuit diagram of the wireless charging system 200B is shown. (For example...) Figure 2B As shown, the wireless charging system 200B corresponds to an LCC series circuit structure. As illustrated, the wireless charging system 200B includes a capacitor 212B, an H-bridge circuit 202B, a resonant circuit 204B, a resonant circuit 206B, an H-bridge circuit 208B, and a capacitor 214B. In the LCC series circuit structure, inductor Lf1 and capacitors Cf1 and C1 are coupled between the H-bridge circuit 202A and the ground mat coil L1 in the ground mat, and series capacitor C2 is coupled between the H-bridge circuit 208A and the vehicle mat coil L2 in the vehicle mat.

[0068] Figure 2C A circuit diagram of the wireless charging system 200C is shown. (For example...) Figure 2C As shown, the wireless charging system 200C corresponds to a series circuit structure. As illustrated, the wireless charging system 200C includes a capacitor 212C, an H-bridge circuit 202C, a resonant circuit 204C, a resonant circuit 206C, an H-bridge circuit 208C, and a capacitor 214C. In the series LCC circuit structure, the series capacitor C1 is coupled between the H-bridge circuit 202A and the ground mat coil L1 in the ground mat, and the inductor Lf2 and capacitors Cf2 and C2 are coupled between the H-bridge circuit 208A and the vehicle mat coil L2 in the vehicle mat.

[0069] Figure 2D A circuit diagram of the wireless charging system 200D is shown. (For example...) Figure 2D As shown, the wireless charging system 200D corresponds to a series circuit structure. As illustrated, the wireless charging system 200D includes a capacitor 212D, an H-bridge circuit 202D, a resonant circuit 204D, a resonant circuit 206D, an H-bridge circuit 208D, and a capacitor 214D. In the series circuit structure, series capacitor C1 is coupled between the H-bridge circuit 202A and the ground mat coil L1 in the ground mat, and series capacitor C2 is coupled between the H-bridge circuit 208A and the vehicle mat coil L2 in the vehicle mat. Exemplary wireless charging pad

[0070] Figure 3 An exemplary wireless charging pad 300 according to some embodiments of the present disclosure is shown. The wireless charging pad 300 may include an H-bridge circuit 322, a resonant circuit 324, a tunable impedance circuit 600, a switch control circuit 326, and an impedance control circuit 336. The tunable impedance circuit 600 may be implemented within the resonant circuit 324. The tunable impedance circuit 600 may also be a separate circuit and may be configured according to, for example, regarding… Figures 6A-6E The various configurations described are connected to the resonant circuit 324.

[0071] The wireless charging pad 300 can charge a vehicle's battery pack over a relatively wide voltage range by switching the H-bridge circuit 322. The H-bridge circuit 322 is an example of a switching circuit that can provide voltage for wireless power transfer to the resonant circuit 324. Any suitable principles and advantages of the wireless charging pad 300 can be found in [the following text is missing from the original] Figures 1A to 1C Implement it in any suitable environment that combines the principles and advantages of [the principle / principle].

[0072] The wireless charging mat 300 can be any floor mat or vehicle mat implementing the wireless charging systems 200A to 200D. In some embodiments, the H-bridge circuit 322 can correspond to any of H-bridge circuits 202A, 208A, 202B, 208B, 202C, 208C, 202D, and 208D. The H-bridge circuit 322 is an example of a switching circuit. In some other embodiments, any other suitable switching circuit can be implemented instead of the H-bridge circuit 322. As an example, a stacked half-bridge can be implemented instead of the H-bridge circuit in higher voltage applications. The resonant circuit 324 can correspond to any of resonant circuits 204A, 206A, 204B, 206B, 204C, 206C, 204D, and 206D.

[0073] The tunable impedance circuit 600 can be implemented in the resonant circuit 324, as follows: Figures 5A-5E As shown. Furthermore, the tunable impedance circuit 600 can correspond to the following: Figures 6A-6B Any configuration shown. Impedance control circuit 336 can control some switches included in tunable impedance circuit 600, as follows: Figures 6A-6E As shown. In some embodiments, the switch of the tunable impedance circuit 600 can be implemented as a field-effect transistor (FET), such as a metal-oxide-semiconductor field-effect transistor (MOSFET), and / or a mechanically engineered device, such as a mechanical switch. In these embodiments, the impedance control circuit 336 can provide a control signal to the gate of the transistor. In this case, the impedance control circuit 336 can be referred to as a gate drive circuit.

[0074] Impedance control circuit 336 can generate a control signal based on the mismatch in resonant frequencies between the resonant frequencies of the resonant circuits 204A-D included in the ground mat and the resonant circuits 206A-206D included in the vehicle mat. Therefore, impedance control circuit 336 can reduce such mismatches in the resonant frequencies and increase the efficiency of wireless power transmission. In some examples, the control signal can exceed the resonant frequency match and depends on one or more of the following, in addition to the resonant frequencies (inductance and capacitance values) on the ground and vehicle sides: the ground mat DC voltage, the vehicle mat DC voltage (battery voltage), the charging power level, or the coupling coefficient.

[0075] like Figures 4A-4D As shown, the H-bridge circuit 322 may include switches 322-1, 322-2, 322-3, and 322-4. In some embodiments, instead of periodically switching each of switches 322-1, 322-2, 322-3, and 322-4, the switch control circuit 326 may control some of switches 322-1, 322-2, 322-3, and 322-4 to periodically switch between open and closed states, and control some of switches 322-1, 322-2, 322-3, and 322-4 to remain open or closed without switching.

[0076] Switch control circuit 326 can provide control signals to control the switching of H-bridge circuit 322 (e.g., Figures 4A to 4D The state of switches 322-1 to 322-4. The switch control circuit 326 can be implemented by any suitable circuit to control the state of the switches in the H-bridge circuit 322. When the switches in 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 this case, the switch control circuit 326 can be referred to as a gate drive circuit. Example H-bridge switch configuration

[0077] Figures 4A-4D An exemplary switching configuration of an H-bridge circuit 322 that can be controlled by a switch control circuit 326 according to some embodiments of the present disclosure is shown. Figure 4A The H-bridge circuit 322 is shown to be configured by the switch control circuit 326 as a switch configuration 410, which can be referred to as a positive configuration. Figure 4B The H-bridge circuit 322 is shown to be configured by the switch control circuit 326 as a switch configuration 420, which can be referred to as a negative configuration. Figure 4C The H-bridge circuit 322 is shown to be configured by the switch control circuit 326 as a switch configuration 430, which may be referred to as a zero-1 configuration. Figure 4DThe H-bridge circuit 322 is shown to be configured by the switch control circuit 326 as a switch configuration 440, which may be referred to as a zero-2 configuration.

[0078] The H-bridge circuit 322 includes four switches: switch 322-1 (also referred to herein as "AP"), switch 322-2 (also referred to herein as "AN"), switch 322-3 (also referred to herein as "BN"), and switch 322-4 (also referred to herein as "BP"). These switches can be any suitable switches for power electronics, such as n-type field-effect transistors arranged to switch a sufficient voltage for wireless charging disclosed herein. In some applications, the H-bridge circuit 322 may include metal-oxide-semiconductor field-effect transistors (MOSFETs). Alternatively or additionally, the H-bridge circuit 322 may include insulated-gate bipolar transistors (IGBTs). The H-bridge circuit 322 may include a first half-bridge and a second half-bridge. The first half-bridge may include switches 322-1 and 322-2. The second half-bridge may include switches 322-3 and 322-4.

[0079] like Figure 4A As shown, in switch configuration 410 (e.g., the positive configuration), switch 322-1 is closed, switch 322-2 is open, switch 322-3 is closed, and switch 322-4 is open. Figure 4B As shown, in switch configuration 420 (e.g., negative configuration), switch 322-1 is open, switch 322-2 is closed, switch 322-3 is open, and switch 322-4 is closed. Figure 4C As shown (e.g., configuration 01), 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. Figure 4D As shown, in switch configuration 440 (e.g., zero 2 configuration), switch 322-1 is closed, switch 322-2 is open, switch 322-3 is open, and switch 322-4 is closed. Example of a tunable impedance circuit in a wireless charging pad

[0080] Figures 5A-5E Five examples of a tunable impedance circuit 600 included in a ground mat of a wireless conversion system are shown. Figures 5A-5E As shown, the tunable impedance circuit 600 can be implemented in the resonant circuits 204A-204D of the floor mat. The resonant frequency of the resonant circuits 204A-204D can be adjusted by regulating the impedance of the tunable impedance circuit 600. Adjusting the impedance of the tunable impedance circuit 600 may include controlling one or more switches (e.g., Figures 6A-6E(One or more switches shown). By adjusting the impedance of the tunable impedance circuit 600, the mismatch between the resonant frequencies of the energy storage circuit of the ground mat and the energy storage circuit of the vehicle mat can be reduced.

[0081] Adjusting the impedance of the tunable impedance circuit 600 can compensate for inductance variations between the inductor L1 of the floor mat and the inductor L2 of the vehicle mat. For example, one or more environmental conditions can cause such inductance variations. These environmental conditions may include, but are not limited to, misalignment between the floor mat and the vehicle mat. Alternatively or additionally, manufacturing processes may result in impedance differences between the resonant circuits of the floor mat and the vehicle mat.

[0082] The adjustable impedance circuit 600 of the floor mat can adjust the resonant frequency of the floor mat's resonant circuit to reduce mismatch with the resonant frequency of the vehicle mat's resonant circuit. Although Figures 5A-5E A tunable impedance circuit 600 implemented in a floor mat is shown, but the tunable impedance circuit 600 may alternatively or additionally be implemented in a vehicle mat in a similar manner to that implemented on a floor mat. In some applications, both the floor mat and the vehicle mat may include their respective tunable impedance circuits.

[0083] Figure 5A This section describes an example of a wireless charging system 500A with an LCC-LCC circuit architecture. As shown in the figure, the wireless charging system 500A includes a resonant circuit that includes a tunable impedance circuit 600 connected in series with an inductor Lf1.

[0084] Figure 5B This section describes an example of a wireless charging system 500B that can be built based on an LCC-LCC circuit architecture. For example... Figure 5B As shown, the tunable impedance circuit 600 can be connected in parallel with the inductor Lf1 in the resonant circuit.

[0085] Figure 5C An example of a wireless charging system 500C with a series circuit structure is shown. As shown, the wireless charging system 500C may include a tunable impedance circuit 600 connected in series with a capacitor C1 in a resonant circuit.

[0086] Figure 5D This section illustrates an example of a 500D wireless charging system that can be formed based on a series circuit architecture. For example... Figure 5D As shown, the tunable impedance circuit 600 is connected in parallel with the capacitor C1 in the resonant circuit.

[0087] Figure 5E An example of a wireless charging system 500E including a tunable impedance circuit 600 is shown. Figure 5EAs shown, the tunable impedance circuit 600 implements the capacitor of the energy storage circuit of the ground mat. This tunable impedance circuit 600 can be an adjustable capacitor circuit. Apart from the tunable impedance circuit 600, the energy storage circuit of the ground mat in the wireless conversion system 500E does not include any capacitors. It is directly connected to L1.

[0088] The tunable impedance circuit 600 can be implemented in any other suitable architecture, such as, but not limited to, the LCC series circuit architecture 200B (e.g., as...). Figure 2B (as shown) and series LCC circuit architecture 200C (e.g., as shown) Figure 2C (As shown). For example, in the LCC series circuit structure 200B, the tunable impedance circuit 600 can be similar to... Figure 5A and 5B This is implemented as shown. Furthermore, in the series IC circuit structure 200C, the tunable impedance circuit 600 can be similar to... Figure 5C and 5D Implement it as shown. Example of a tunable impedance circuit

[0089] The resonant circuit in a wireless charging system may include a tunable impedance circuit. The tunable impedance circuit can be any suitable circuit that adjusts the impedance of the resonant circuit to improve the performance of the wireless charging system. An exemplary tunable impedance circuit includes a switched capacitor circuit, which includes one or more switches to connect or disconnect one or more corresponding capacitors from the effective impedance of the tunable impedance circuit. The switched capacitor circuit may include any suitable number of switches and any suitable number of capacitors. The switched capacitor circuit may include any suitable series and / or parallel arrangement of one or more capacitors and one or more switches.

[0090] Figures 6A-6E Examples of tunable impedance circuits 600A-600E are shown. Without limitation, any of the tunable impedance circuit configurations 600A-600E can implement the tunable impedance circuit 600 of any of the wireless charging systems 500A-500E. In some embodiments, switch control circuitry 326 may be coupled to the control terminal of each switch included in the tunable impedance circuits 600A-600E and control these switches to adjust the effective impedance of the tunable impedance circuit. For purposes of description, Figures 6A-6E Two switching circuits are shown. However, any suitable principles and advantages of the invention can be applied to three or more switching circuits. Furthermore, Figures 6A-6E Any combination of the characteristics can be achieved in a tunable impedance circuit.

[0091] Figure 6AAn example of a tunable impedance circuit 600A is shown. The tunable impedance circuit 600A may include two switching circuits 610-1 and 610-2 connected in series. For example... Figure 6A As shown, the first switching circuit 610-1 may include a first capacitor 612-1, a second capacitor 612-2, and a switch 614-1 connected in parallel with each other. Furthermore, the second switching circuit 610-2 may include two capacitors 612-3 and 612-4 and a switch 614-2. The two capacitors 612-3 and 612-4 and the switch 614-2 are connected in parallel. The capacitance values ​​of each of the capacitors 612-1 to 612-4 may be determined based on a specific application, and the invention does not limit these values. For example, but not limited to, the capacitance values ​​of each of the capacitors 612-1 to 612-4 may be different, or one or more capacitors 612-1 to 612-4 may have the same capacitance value.

[0092] Figure 6B Another example of a 600A adjustable impedance circuit is shown. Figure 6B As shown, the tunable impedance circuit 600B may include a tunable impedance circuit 600A connected in series with capacitor circuits 620-1 and 620-2. In some embodiments, the tunable impedance circuit 600A and the two capacitor circuits 620-1 and 620-2 are connected in series with each other. Each of the capacitor circuits 620-1 and 620-2 may include two capacitors connected in parallel with each other. Capacitors 622-1 and 622-2 are connected in parallel in capacitor circuit 620-1. Capacitors 622-3 and 622-4 are connected in parallel in capacitor circuit 620-2. Figure 6B The diagram shows that a tunable impedance circuit may include a switched capacitor circuit and a fixed capacitor.

[0093] Figure 6C An example of a tunable impedance circuit 600C is shown. The tunable impedance circuit 600C includes a hybrid parallel-series and series-parallel switched capacitor array. The tunable impedance circuit 600C includes a fixed capacitor circuit 630-1, a switched capacitor circuit 630-2, and a tunable impedance circuit 600B. (As shown...) Figure 6C As shown, the fixed capacitor circuit 630-1 and the switched capacitor circuit 630-2 are connected in parallel.

[0094] The fixed capacitor circuit 630-1 may include a parallel combination of series capacitors. For example, capacitors 632-1 and 632-2 are connected in series with each other and in parallel with a series combination of capacitors 632-3 and 632-4. In some embodiments, the fixed capacitor circuit 630-1 may include four capacitors 632-1-632-4, with each of two pairs of capacitors connected in series and the two pairs of series capacitors connected in parallel with each other. For example, the first pair of capacitors 632-1 and 632-2 are connected in series, and the second pair of capacitors 632-3 and 632-4 are connected in series. Then, the first pair of capacitors 632-1 and 632-2 and the second pair of capacitors 632-3 and 632-4 are connected in parallel, and this parallel connection forms the fixed capacitor circuit 630-1.

[0095] The switched capacitor circuit 630-2 may include multiple series circuits, each including a capacitor connected in series with a switch, wherein the series circuits are connected in parallel with each other. For example, the first series circuit includes switch 634-1 connected in series with capacitors 632-5 and 632-6, and the second series circuit includes switch 634-2 connected in series with capacitors 632-7 and 632-8. The first series circuit is connected in parallel with the second series circuit in the switched capacitor circuit 630-2. Figure 6C As shown, the switched capacitor circuit 630-2 may include four capacitors 632-5-632-8 and two switches 634-1-634-2. As shown, the first group of switches 634-1, capacitors 632-5 and 632-6 can be connected in series, and the second group of switches 634-2, capacitors 632-7 and 632-8 can be connected in series. The first and second groups can also be connected in parallel.

[0096] Figure 6D An example of a tunable impedance circuit 600D is shown. The tunable impedance circuit 600D may include a switch 644 connected (in series) with a tunable impedance circuit 600A. The tunable impedance circuit 600A includes capacitors 612-1-612-4 and switches 614-1 and 614-2. As shown, one end of switch 644 is coupled at node 647 to the first end of capacitors 612-1, 612-2, and switch 614-1. Switch 644 can selectively electrically connect the tunable impedance circuit 600A to the node or selectively electrically disconnect the tunable impedance circuit 600A from the node.

[0097] Figure 6E Another example of the tunable impedance circuit 600E is shown. For example... Figure 6EAs shown, the tunable impedance circuit 600E may include four capacitors 652-1-652-4 and switches 654-1-654-3. In some embodiments, the first switch 654-1, the first capacitor 652-1, and the second capacitor 652-2 may be connected in series to form a first switch group 650-1. The second switch 654-2, the third capacitor 652-3, and the fourth capacitor 652-4 may be connected in series to form a second switch group 650-2. The first switch group 650-1, the second switch group 650-2, and the third switch 654-3 may be connected in parallel with each other.

[0098] In some other embodiments, a varactor diode capacitor can be implemented instead of a switched capacitor circuit including a capacitor and a switch. In these embodiments, the switch control circuit 326 can adjust the capacitance of the varactor diode capacitor by applying a bias voltage to it. Furthermore, in some other embodiments, a tunable impedance circuit can tune an inductor or a combination of inductor and capacitor.

[0099] In some embodiments, various architectures of the tunable impedance circuits 600A-600E can be configured by combining two or more tunable impedance circuits 600D-600E. For example, tunable impedance circuits 600D and 600E can be connected in series. As another example, tunable impedance circuits 600A and 600C can be connected in series. These embodiments are provided for illustrative purposes, and this disclosure is not limited to these embodiments.

[0100] The foregoing disclosure is not intended to limit this disclosure to the precise form disclosed or to any particular field of application. Therefore, various alternative embodiments and / or modifications of this disclosure are possible, whether expressly described or implied herein. Since embodiments of this disclosure have been so described, those skilled in the art will recognize that changes in form and detail may be made without departing from the scope of this disclosure. Therefore, this disclosure is defined only by the claims.

[0101] It should be understood that not all purposes or advantages can be achieved according to any particular example described herein. Therefore, by way of example, those skilled in the art will recognize that some examples can achieve or optimize one or more advantages as taught herein without necessarily achieving other purposes or advantages as taught or suggested herein.

[0102] All the processes described herein can be embodied in software code modules executed by a computing system, including a computer or processor, and are fully automated via these software code modules. The code modules can be stored on any type of non-transitory computer-readable medium or other computer storage device. Some or all of the methods can be implemented in dedicated computer hardware.

[0103] Based on this disclosure, many other variations besides those described herein will be apparent. For example, depending on the example, some actions, events, or functions of any algorithm described herein may be executed in a different order, may be added, combined, or omitted entirely (e.g., not all described actions or events are necessary for the practice of the algorithm). Furthermore, in some examples, actions or events may be executed simultaneously rather than sequentially, for example, through multithreading, interrupt handling, or multiple processors or processor cores, or on other parallel architectures. Moreover, different tasks or processes may be performed by different machines and / or computing systems that can work together.

[0104] The various illustrative logic blocks and modules described in conjunction with the examples disclosed herein can be implemented or executed by a machine designed to perform the functions described herein, 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. The processor may be a microprocessor, but alternatively, it may be a controller, a microcontroller, or a state machine, or a combination thereof. The processor may include circuitry for processing computer-executable instructions. In some examples, the processor includes an FPGA or other programmable device that performs logic operations without processing computer-executable instructions. The processor may also be implemented as a combination of computing devices, such as a combination of a DSP and a microprocessor, multiple microprocessors, a microprocessor incorporating a DSP core, or any other such configuration. Although the description herein is primarily directed to digital technologies, the processor may also primarily comprise analog components. The computing environment may include any type of computer system, including but not limited to microprocessor-based computer systems, mainframe computers, digital signal processors, portable computing devices, computing engines within device controllers or appliances, etc.

[0105] Elements of the methods, processes, routines, or algorithms described in conjunction with the embodiments disclosed herein may be implemented directly in hardware, in software modules executed by a processor device, or a combination of both. The software modules may reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disks, removable disks, CD-ROMs, or any other form of non-transitory computer-readable storage media. Exemplary storage media may be coupled to a processor device such that the processor device can read information from and write information to the storage media. Alternatively, the storage media may be integrated into the processor device. The processor device and storage media may reside in an ASIC. The ASIC may reside in a user terminal. Alternatively, the processor device and storage media may reside as discrete components in the user terminal.

[0106] The processes described herein or illustrated in the accompanying drawings can be initiated in response to events, 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 drives, 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 the 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.

[0107] In this context, unless otherwise specifically stated, conditional language such as “can,” “able,” “may,” or “may” should be understood as generally used to express that certain examples include but do not include certain features, elements, and / or steps. Therefore, such conditional language is generally not intended to imply that features, elements, and / or steps are in any way examples, or that examples must include logic for determining whether such features, elements, and / or steps are included in or to be performed in any particular example, with or without user input or prompts.

[0108] Unless otherwise specifically stated, 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 items, terms, etc., can be X, Y or Z or any combination thereof (e.g., X, Y and / or Z). Therefore, such disjunctive language is generally not intended and should not imply that some instances require at least one of X, at least one of Y or at least one of Z to be present individually.

[0109] Any process description, element, or block described herein and / or depicted in the accompanying drawings should be understood as potentially representing a module, segment, or portion of code comprising executable instructions for implementing a particular logical function or element within the process. Alternative examples are included within the scope of the examples described herein, wherein, depending on the functionality involved, an element or function may be removed from the order shown or discussed (including substantially simultaneously or in reverse order).

[0110] It should be emphasized that many variations and modifications can be made to the above examples, and these variations 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.

[0111] Any process description, element, or block described herein and / or depicted in the flowcharts in the accompanying drawings should be understood as potentially representing a module, segment, or portion of code comprising executable instructions for implementing a particular logical function or element within the process. Alternative implementations are included within the scope of the examples described herein, wherein elements or functions may be removed from the order shown or discussed, depending on the functionality involved, including substantially simultaneously or in reverse order, depending on the understanding of a person skilled in the art.

[0112] Unless otherwise explicitly stated, articles such as “a” or “an” should generally be interpreted as including one or more of the stated items. Therefore, phrases such as “configured to” are intended to include one or more of the stated devices. Devices of one or more such statements may also be configured collectively to perform the stated statements. For example, “processors configured to perform statements A, B, and C” could include a first processor configured to perform statement A, which works in conjunction with a second processor configured to perform statements B and C.

Claims

1. A wireless charging pad, comprising: Switching circuit; A resonant circuit having a resonant frequency and being electrically connected to the switching circuit, the resonant circuit including a coil arranged for wireless power transmission, and the resonant circuit including a tunable impedance circuit. as well as An impedance control circuit is configured to adjust the impedance of the tunable impedance circuit to adjust the resonant frequency of the resonant circuit.

2. The wireless charging pad of claim 1, wherein the tunable impedance circuit includes a switch and a capacitor, and the impedance control circuit is configured to adjust the impedance of the tunable impedance circuit by changing the state of the switch.

3. The wireless charging pad according to claim 2, wherein the switch is connected in parallel with the capacitor.

4. The wireless charging pad according to claim 2, wherein the switch is connected in series with the capacitor.

5. The wireless charging pad of claim 1, wherein the tunable impedance circuit comprises a plurality of series circuits connected in parallel with each other, and each of the series circuits comprises a switch connected in series with a capacitor.

6. The wireless charging pad of claim 1, wherein the tunable impedance circuit comprises a plurality of parallel circuits connected in series with each other, and each of the parallel circuits comprises a switch connected in parallel with a capacitor.

7. The wireless charging pad according to claim 1, wherein the wireless charging pad is a floor mat.

8. The wireless charging pad according to claim 1, wherein the wireless charging pad is a vehicle mat.

9. The wireless charging pad according to claim 1, wherein the switching circuit includes an H-bridge circuit.

10. The wireless charging pad of claim 1, wherein the switching circuit comprises a stacked half-bridge circuit.

11. The wireless charging pad of claim 1, wherein the impedance control circuit is configured to adjust the impedance based on a mismatch between the resonant frequency of the resonant circuit and the resonant frequency of the second resonant circuit of the second wireless charging pad, the second wireless charging pad being positioned adjacent to the wireless charging pad for wireless charging.

12. The wireless charging pad of claim 1, wherein the resonant circuit includes a capacitor, and wherein the tunable impedance circuit, the coil, and the capacitor are connected in series.

13. The wireless charging pad of claim 1, wherein the resonant circuit includes a capacitor connected in series with the coil, and wherein the tunable impedance circuit is connected in parallel with the coil.

14. The wireless charging pad of claim 1, wherein the resonant circuit has an LCC architecture, and wherein the tunable impedance circuit is connected in series with the inductor of the resonant circuit.

15. The wireless charging pad of claim 1, wherein the resonant circuit has an LCC architecture, and wherein the tunable impedance circuit is connected in parallel with the inductor of the resonant circuit.

16. The wireless charging pad according to claim 1, wherein the tunable impedance circuit is connected in series with the coil.

17. A method for wireless power transmission, the method comprising: The mismatch in resonant frequency between the first resonant circuit of the floor mat and the second resonant circuit of the vehicle mat was detected. Based on the detection, the impedance of the tunable impedance circuit is adjusted to reduce the mismatch at the resonant frequency; as well as After the adjustment, power is wirelessly transmitted from the floor mat to the vehicle mat.

18. The method of claim 17, wherein the first resonant circuit of the ground mat includes the tunable impedance circuit.

19. The method of claim 17, wherein the second resonant circuit of the vehicle pad includes the tunable impedance circuit.

20. The method of claim 17, wherein the mismatch of the resonant frequency is associated with the misalignment between the floor mat and the vehicle mat.

21. The method of claim 17, wherein the mismatch of the resonant frequency is associated with at least one of the following: a vehicle platform, an object located between the floor mat and the vehicle mat, or a manufacturing process.

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