Dual source on-board charging system for wireless power transfer

Abstract

An apparatus for transferring power includes a transformer assembly; a first power converter coupled to a first power interface and the transformer assembly, wherein the first power interface is associated with an alternating current grid or direct current charger; a second power converter coupled to the transformer assembly and an electric vehicle power source; and an impedance matching network coupled to a second power interface and the transformer assembly, wherein the second power interface is associated with a wireless power source, wherein the impedance matching network is coupled to the transformer assembly with a center-tapped configuration, the center-tapped configuration includes the impedance matching network and the transformer assembly coupled via connection points between inductors of the transformer assembly.

Description

WiTricity Ref. P0495PCT-W-NPR1DUAL SOURCE ON-BOARD CHARGING SYSTEM FOR WIRELESS POWER TRANSFERCROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of U.S. Provisional Patent Application Serial No.63 / 747,824 filed January 21, 2025, the disclosure of which is incorporated by reference herein in its entirety.TECHNICAL FIELD

[0002] The following disclosure is directed to wireless power transfer, and, in particular, to wired and wireless power transfer to remote systems such as vehicles including batteries.BACKGROUND

[0003] Electric vehicles (EVs) are often charged through some type of wired alternating current (AC) such as household or commercial AC supply sources or special-purpose direct current (DC) sources. The wired charging connections require cables or other similar connectors that are physically connected to a power supply. Cables and similar connectors may be inconvenient or cumbersome and have other drawbacks. Wireless power transfer (WPT) systems that are capable of transferring power in free space (e.g., via a magnetic field) to be used to charge EV traction batteries may overcome some of the deficiencies of wired charging solutions.

[0004] In some designs, an electric vehicle can be configured to receive power through both wired power connections and wireless power transfer. Various dual-source electric vehicles can receive wired and wireless power either alternately or simultaneously. As such, wireless power transfer systems and methods that efficiently and effectively facilitate reception, conditioning, and storage of power by both wired connections and wireless power transfer are needed.Attorney Docket No. P0495PCTWNPR1 1WiTricity Ref. P0495PCT-W-NPR1SUMMARY

[0005] This disclosure relates to a charging system that integrates wired and wireless power transfer capabilities. By utilizing a center-tapped transformer topology and shared power conversion stages, the system alternates between wired charging and wireless charging modes without requiring extensive additional hardware, thereby reducing the overall component count while maintaining galvanic isolation.

[0006] In general, in some aspects, an apparatus for transferring power includes a first power converter coupled to a first power interface, an isolation transformer having a first transformer coil coupled to the first power converter and a second transformer coil magnetically coupled to and galvanically isolated from the first transformer coil, a second power converter coupled to the second coil of the isolation transformer and to a second power interface, a third transformer coil magnetically coupled to and galvanically isolated from the first transformer coil and magnetically coupled to the second transformer coil, and a third power interface for connecting the third transformer coil to another device.

[0007] Implementations may include some or all of the following features, in any order or combination. The first power converter, the isolation transformer, and the second power converter may provide DC-DC conversion for transferring power bidirectionally between the first power interface and the second power interface. Capacitors may be connected between the second transformer coil and the second power converter, and when a wireless power transfer coil is connected to the third power interface, the capacitors may form a resonant circuit with the wireless power transfer coil. A first switch may be coupled between the third transformer coil and the third power interface. The capacitors may form the resonant circuit with the wireless power transfer coil when a first switch is in a configuration coupling the wireless power transfer coil to the third transformer coil through the third interface. A power bypass may route power received at the first power interface to the second power interface, bypassing the first and second power converters and isolation transformer, and the power bypass may be configurable to allow power received at the third power interface to flow directly between the first power interface and the second power interface, while preventingAttorney Docket No. P0495PCTWNPR1 2WiTricity Ref. P0495PCT-W-NPR1such power from leaving the apparatus through an external input to the first power interface. A secondary-side power controller may be included. The secondary-side power controller may include an input for receiving a communication sensor signal from a wireless power transfer coil. A wireless power charging controller and a plurality of sensors may be included. The plurality of sensors may include a WiFi module, a position sensor, and a temperature sensor.

[0008] In general, in some aspects, an apparatus for transferring power includes a first power converter coupled to a first power interface, a second power converter coupled to a second power interface, an isolation transformer connected between the first power converter and the second power converter, a first switch for selectively decoupling the isolation transformer from the second power converter, and a third power interface for connecting the second power converter to another device.

[0009] Implementations may include some or all of the following features, in any order or combination. The first power converter, the isolation transformer, and the second power converter may provide DC-DC conversion for transferring power bidirectionally between the first power interface and the second power interface when the first switch is closed. Capacitors may be connected between the second transformer coil and the second power converter, and when a wireless power transfer coil is connected to the third interface, the capacitors may form a resonant circuit with the wireless power transfer coil. A power bypass may route power received at the first power interface to the second power interface, bypassing the first and second power converters and isolation transformer. The power bypass may be configurable to allow power received at the third power interface to flow directly between the first power interface and the second power interface, while preventing such power from leaving the apparatus through an external input to the first power interface.

[0010] In general, in some aspects, an apparatus for transferring power includes a first wired power interface, a second wired power interface, a wireless power transfer (WPT) interface, an AC-DC power converter, a DC-DC power converter coupled to the AC-DC power converter and to the second wired power interface, and a power bypass coupled to the first wired power interface and to the second wired power interface. The power bypass is Attorney Docket No. P0495PCTWNPR1 3WiTricity Ref. P0495PCT-W-NPR1configured to couple the first wired power interface to an input of the AC-DC power converter, and decouple the first wired power interface from the second wired power interface when an alternating current (AC) power source or load is provided to the first wired power interface, to decouple the first wired power interface from the input of the AC-DC power converter, and couple the first wired power interface to the second wired power interface when a direct current (DC) power source or load is provided to the first wired power interface, and to decouple the first wired power interface from the input of the AC-DC power converter, and couple the first wired power interface to the second wired power interface when a wireless power source or load is coupled to the WPT interface.

[0011] Implementations may include some or all of the following features, in any order or combination. The WPT interface may be selectively coupled to an internal circuit of the DC-DC power converter. The WPT interface may be selectively coupled to the first wired power interface.

[0012] In general, in some aspects, an apparatus for retrofitting wireless power transfer (WPT) into a wired electric vehicle charging system includes an on-board charger (OBC) of the wired electric vehicle charging system, a charging controller coupled to the OBC, a WPT controller coupled to the charging controller, a wireless power interface for coupling the OBC to a wireless power transfer coil, a switch configured to selectively couple the wireless power interface to the OBC under the control of the charging controller, and a plurality of sensors.

[0013] The OBC may be further configured to charge an electric vehicle using power received through the wireless power interface when the switch is closed, and to charge the electric vehicle using power received through a wired power interface of the OBC when the switch is open.

[0014] In general, in some aspects, an apparatus for retrofitting wireless power transfer (WPT) into a wired electric vehicle charging system includes an on-board charger (OBC) of the wired electric vehicle charging system, a charging controller coupled to the OBC, a WPT controller coupled to the charging controller, a plurality of capacitors, a power interface forAttorney Docket No. P0495PCTWNPR1 4WiTricity Ref. P0495PCT-W-NPR1coupling to a wireless power transfer coil, a switch coupled to the plurality of capacitors, configured to selectively couple the wireless power interface to the plurality of capacitors under the control of the charging controller, and a plurality of sensors.

[0015] In general, in some aspects, an apparatus for transferring power, the apparatus comprising: a transformer assembly; a first power converter coupled to a first power interface and the transformer assembly, wherein the first power interface is associated with an alternating current grid or direct current charger; a second power converter coupled to the transformer assembly and an electric vehicle power source; and an impedance matching network coupled to a second power interface and the transformer assembly, wherein the second power interface is associated with a wireless power source, wherein the impedance matching network is coupled to the transformer assembly with a center-tapped configuration, the center-tapped configuration includes the impedance matching network and the transformer assembly coupled via connection points between inductors of the transformer assembly.

[0016] Implementations may include some or all of the following features, in any order or combination. The apparatus is configured to operate in a plurality of modes, the plurality of modes comprising a differential mode of the transformer assembly and a common mode of the transformer assembly. The differential mode of the transformer assembly causes voltage between the first power converter and the second power converter to be equivalent to each other. The common mode of the transformer assembly distributes current between two rectifiers, reducing rectifier conduction loss. The impedance matching network comprises a first of the two rectifiers and the second power converter comprises a second of the two rectifiers. The rectifier conduction loss is reduced 50%.

[0017] Various embodiments can include one or more of the foregoing features, in any combination.Attorney Docket No. P0495PCTWNPR1 5WiTricity Ref. P0495PCT-W-NPR1BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figures 1-4 illustrate electric vehicle charging environments.

[0019] Figure 5 is a schematic diagram of example components of a wireless power transfer system.

[0020] Figure 6 is a block diagram showing high-level components of a wired and wireless power transfer system.

[0021] Figure 7 illustrates a block diagram showing high-level components of a wired and wireless power transfer system in a center-tapped transformer configuration.

[0022] Figure 8 illustrates a circuit diagram showing the center-tapped transformer configuration of Figure 7.

[0023] Figure 9 illustrates a circuit diagram showing a differential mode of operation of the center-tapped transformer configuration of Figures 7-8.

[0024] Figures 10-11 illustrate various circuit diagrams showing a common mode of operation of the center-tapped transformer configuration of Figures 7-8.

[0025] Figures 12-14 illustrate results of a simulation.DETAILED DESCRIPTION

[0026] Wireless power transfer (WPT) for charging electric vehicles is described in detail in patents such as U.S. Patents 8,933,594, titled "Wireless energy transfer for vehicles," and 9,561,730, titled "Wireless power transmission in electric vehicles," which are incorporated here by reference in their entirety. Wireless electric vehicle charging (WEVC) systems according to the SAE J2954 standard, as of the date of filing of this application, provide up to 22 kW of power at each charging station. Lower power levels, such as 11 kW and 7 kW, are commonly used, due to their compatibility with household and industrial electrical systems. At the same time, higher power levels are also used, especially for charging heavier-dutyAttorney Docket No. P0495PCTWNPR1 6WiTricity Ref. P0495PCT-W-NPR1vehicles, like busses or trucks, or for charging light duty vehicles at a higher rate, and proposals have been made to extend existing WEVC standards to such power levels. Lower-power vehicles, such as scooters, golf carts, neighborhood electric vehicles (NEVs), or industrial vehicles like forklifts and automated ground vehicles (AGVs) may also be charged using WPT, but standards for doing so do not currently exist, though several are in development.

[0027] Similarly, plug-in charging systems are generally divided into three categories based on power level - Level 1 alternating current (AC) charging at up to 3.3 kW, Level 2 AC charging up to 22 kW, but more commonly 7 kW or 11 kW, and direct current (DC) fast charging, sometimes called Level 3, at power levels of 50 kW to 350 kW and higher. DC charging at Level 2 power levels is possible, but not common. Vehicles supporting Level 1 and Level 2 AC charging use a power converter on-board the vehicle to convert AC power to DC power for charging the vehicle's traction battery. The electric vehicle service equipment (EVSE), the device which provides that power from the Grid or other electricity source, may simply be a set of isolation switches and the logic circuits to control them. DC charging uses power converters external to the vehicle for converting AC power from the Grid or other power supply to DC power, which is then either provided directly to the vehicle battery or boosted to a higher voltage level by a power converter on board the vehicle, if required. Intermediate conversions to AC or other frequencies may be used, such as DC-DC conversion with an intermediate AC isolation transformer. All of the above types of charging may be bidirectional, with power from the vehicle traction battery provided to the charging system or other external load in a vehicle-to-grid (V2G), vehicle-to-home (V2H), or similar arrangement (generally V2x). In such a case, each of the power conversion stages may be bidirectional, or dedicated power conversion may be used for each direction of current flow, at any or all of the stages involved. References herein to "AC power," "DC power," or "AC" and "DC" alone should be understood as referring to power that is transferred as electricity having the corresponding current waveform.

[0028] Wireless vehicle charging uses power converters on both sides of the WPT connection, to convert 50 Hz or 60 Hz AC power from the Grid to, for example, 87 kHz powerAttorney Docket No. P0495PCTWNPR1 7WiTricity Ref. P0495PCT-W-NPR1(referred to as low-frequency, LF, power) for conversion from electric current to a magnetic field on the transmitter side, and then from the LF magnetic field to LF electric current and then to DC power within the vehicle for charging the battery. Wireless power transfer through an electromagnetic field inherently isolates the vehicle electrical system from the Grid, while wired charging solutions require an isolation stage in the vehicle, in the external charger, or both. Sometimes the isolation is implemented within a power conversion stage, such as an isolation transformer as part of a DC-DC converter. In some examples, as described in U.S. Patents 9,561,730 and 9,381,821, both incorporated here by reference, various power converters or components of the power converters are shared between wired and wireless charging systems.

[0029] Conventional topologies for integrating the WPT into the OBC typically rely on either additional rectifiers for each operation or high-frequency relays to switch between the OBC and WPT modes, leading to higher hardware costs. The increased hardware requirements and costs associated with the hardware requirements leads to decreased adoption of WPT. Manufacturers may find the adoption of WPT less appealing due to the added design implementations for increased hardware and may avoid the designs altogether due to the increased costs.

[0030] To address the above issues, aspects of the present disclosure provide a centertapped transformer with differential and common-mode modulation that can alternate between these two operations without extra relays or switches, offering a solution with reduced hardware demands. By alternating between differential and common-mode modulation of the center-tapped transformer, the OBC and WPT operations can be integrated using the existing OBC hardware, with minimal additional components for the WPT— specifically, VA magnetics and VA IMN. This approach results in significant cost savings and facilitates the easier adoption of WPT technology.

[0031] Figure 1 shows an example of a parking facility 100 with wireless power transfer services. Two vehicles, 102a, 102b are each parked over a WPT pad 104a, 104b. Although shown as cars in Figure 1, any type of vehicle, such as a golf cart, neighborhood electric Attorney Docket No. P0495PCTWNPR1 8WiTricity Ref. P0495PCT-W-NPR1vehicle, delivery van, bus, AGV, etc., can be charged in the same way. WPT pads 106a, 106b in the vehicles are connected to respective power converters 108a, 108b. The power converters 108a, 108b convert power received by the pads 106a, 106b to a form suitable for charging the vehicle's traction battery, not shown. In some examples, the power converters 108a, 108b may be integrated with power converters used for plug-in charging of the vehicle, commonly called on-board chargers (OBC), or other on-board vehicle components. The ground-side WPT pads 104a, 104b are shown with external power converters 110a, 110b, each connected to a power supply bus 112. The power supply bus 112 is in turn connected to a central power distribution unit 114. In some examples, the power distribution unit provides DC power to the bus 112, and the external power converters 110a, 110b include inverters, such as the multi-level inverter (MLI) described in U.S. Patent Applications 18 / 486,830 and 18 / 486,835, both filed October 13, 2023, and incorporated here by reference. The inverters provide low-frequency (LF) power signals, such as the 87kHz signals used for wireless charging according to the SAE J2954 standard, to the pads 104a, 104b, to turn into magnetic fields for wireless power transfer. Alternatively, the power converters 110a, 110b may be implemented as DC-DC converters in combination with H-bridge inverters. In some examples, an MLI may be used at one charging station, and a DC-DC converter and inverter used at another. In some examples, the pads 104a, 104b are referred to as Ground Assembly Resonators (GAR), and the combination of the GAR with the power converter 110 or any other ground-side electronics is referred to as a Ground Assembly (GA), whether integrated or housed separately. Similarly, the WPT pads 106a, 106b may be referred to as Vehicle Assembly Resonators (VAR) and the combination of a VAR and a power converter 108 or any other vehicle-side electronics as a Vehicle Assembly (VA), again, whether integrated or housed separately. Each of the connections shown may be bi-directional, allowing the vehicles to discharge power from their batteries to the power distribution unit or other load in a V2x arrangement.

[0032] Figure 2 shows an example of another parking facility 200 with both wireless and wired charging services. In addition to the WPT stations from Figure 1, two wired charging stations 210a, 210b are connected to the DC bus 112. As shown, the charging stations areAttorney Docket No. P0495PCTWNPR1 9WiTricity Ref. P0495PCT-W-NPR1each plugged into a corresponding vehicle, 202a, 202b via a charging cable 212a, 212b. Within the vehicles, on-board chargers 208a, 208b provide the power from the charging stations to each vehicle's traction battery (not shown). In some examples, the charging stations 210a, 210b include inverters, such as the same multi-level inverter used in the WPT systems, to provide AC power to the vehicle. In other examples, the charging stations include DC-DC power converters, for shifting the DC voltage level of the bus 112 to the voltage required by each vehicle. In other examples, the charging stations provide DC power directly from the bus to the vehicle, with the charging stations themselves serving only as user-interface terminals and isolation switches, and the OBC in the vehicle performing any power conversion necessary to match the bus voltage to the voltage needed for charging the battery.

[0033] While the WPT stations and the wired charging stations are shown separately, both types of charging may be provided at any of the parking locations, and both AC and DC wired charging may be provided at the same station. A fleet operator may need only a single type of charging station, while other charging station operators, such as public parking facilities, may desire to provide many different types of charging.

[0034] In both wired and wireless charging, it may be necessary to provide external cooling facilities. For wireless power transfer, the GARs 104a, 104b and the power converters 110a, 110b may each produce waste heat. For wired connections, any power conversion within the charging stations 210a, 210b may produce waste heat, and it may also be necessary to provide cooling within the charging cables 212a, 212b. While the vehicles themselves generally have on-board cooling facilities, they could also make use of coolant provided through the charging cables to cool the OBC while charging. Figure 3 shows an example of the parking facility 200 from Figure 2 in which distributed cooling is provided. A cooling bus 312 is provided in parallel to the DC bus 112, with coolant from each charging station routed back to a cooling system 314 co-located with the power distribution unit 114, or elsewhere along the bus. The cooling bus312 may contain multiple lines of coolant, in various routing topologies, not shown, based on the needs of the system and the type of cooling provided.Attorney Docket No. P0495PCTWNPR1 10WiTricity Ref. P0495PCT-W-NPR1

[0035] In some examples, as shown by system 400 in Figure 4, the DC bus 112 also allows additional power sources, such as solar arrays 414a, 414b, 414c, to provide additional power for vehicle charging. In some examples, the solar arrays may be mounted over a parking area, to provide shade to the vehicles, or nearby, to provide shade to users of the vehicle while waiting for their vehicle to charge. A power converter 410 boosts the voltage level of DC power from the solar array to match that of the DC bus 112. Bi-directional devices, such as a storage battery 402, can also be connected to the bus. The storage battery 402 may include a built-in power converter (not shown) to match the voltage from the bus to the voltage of the battery. A storage battery stores excess power from the solar array during times that more solar power is produced than is required for charging vehicles and discharges this power to the vehicles orto the power distribution unit 114 as needed. Placing such a battery on the DC bus avoids the need to provide it with an inverter to provide AC power. In some examples, vehicles capable of V2x operation may provide power to the battery 402 for later distribution to other vehicles. While not shown, the battery 402 and the solar power converter 410 may also be connected to the cooling bus 312. The battery could also be charged from the Grid, such as to even out power demand during the day and to decrease surge demand if many vehicles begin charging at the same time.

[0036] Figure 5 shows a WPT system 500 including a ground-side WPT assembly, or GA, 502 and a vehicle-side WPT assembly, or VA, 520. The GA receives power from an external power supply 504, such as the DC bus shown above, or an electrical utility grid, which generally provides AC power. A GA power converter 506 converts the incoming power to an LF waveform suitable for transferring power wirelessly through a GA resonator 508. The GA power converter 506 supplies power to the GA resonator 508 to generate an electromagnetic field for wireless power transfer. The GA resonator 508 is shown as including a resonant capacitor and an induction coil; other topologies, including more resonant components and fixed or tunable impedance matching components, not shown, may be used. In comparison to Figures 1-4, the GA resonator 508 would be included within the ground-side WPT pad 104a, 104b. The GA power converter 506 corresponds to the ground-side power converters 110a,Attorney Docket No. P0495PCTWNPR1 11WiTricity Ref. P0495PCT-W-NPR1110b. As noted above, the ground-side WPT assembly 502 is referred to as the GA regardless of whether the GA resonator and the GA power converter are integrated or separate.

[0037] On the vehicle side, the VA 520 includes a VA resonator 522 that is magnetically coupled to the GA resonator 508 so that power can be transferred between them. The VA resonator 522 provides power to a VA power converter 524. The VA power converter 524 may include, among other things, an LF / DC converter configured to convert power at an operating frequency of the resonator to DC power at a voltage level matched to the voltage level of the traction battery 550. The LF / DC converter may include, or be combined with, various conversion stages, including intermediate AC power or multiple different voltages of DC power. Example hardware may include rectifiers, inverters, and buck or boost converters. The VA power converter 524 provides the converted power to charge the traction battery 550. The VA 520 may also be configured to provide power wirelessly through the VA resonator 522 to the GA resonator 508 to feed power back to the power supply 504 in a V2x mode of operation. In comparison to Figures 1-4, the VA resonator 522 would be included within the vehicle-side WPT pads 106a, 106b. The VA power converter 524 corresponds to the vehicleside power converters 108a, 108b. The vehicle-side WPT assembly 520 is referred to as the VA regardless of whether the VA resonator and the VA power converter are integrated or separate. As discussed below, the power converter and other electronics of the VA may be provided by other vehicle electronic components. In such case, this disclosure uses the term VA to refer to whatever vehicle-side WPT components remain separate from other vehicle systems.

[0038] Each of the VA resonator 522 and the GA resonator 508 may operate in transmit or receive mode based on the direction of the power transfer. Although the power output of the VA 520 is shown as going directly to a vehicle traction battery 550 in Figure 5 and throughout, in actual practice additional electronics are likely to be involved, such as a charge management system (CMS) or battery management system (BMS) which manages the voltage and current levels of the power going to and from the traction battery to assure the most beneficial charge profile is followed. In some examples, the CMS or BMS function is performedAttorney Docket No. P0495PCTWNPR1 12WiTricity Ref. P0495PCT-W-NPR1by electronics within the VA. References to providing power to, charging, or discharging power from the traction battery should be understood to include providing power to or receiving power from whatever other electronics are involved in ultimately providing power to, or discharging power from, whatever type of energy storage is used in a given application, and the battery symbol 550 is used to represent whatever systems are ultimately connected to the power output of the vehicle charging system.

[0039] Electric vehicles equipped for wireless charging are generally also equipped for plug-in charging. While wired and wireless charging systems each include unique components not needed by the other, they also include some components in common, and others that may be optimized differently for the two modes, but for which a single version could work for both. U.S. Patents 9,381,821 and 9,561,730, both incorporated here by reference, describe several ways in which components may be shared between wired charging systems and wireless power transfer systems. Advances in both electric vehicle design and wireless power transfer have enabled further improvements to such integration. In some examples, a vehicle may ship from the manufacturer with only a plug-in charging system, but with some of the components needed to accept wireless power included, so that a simplified VA can be connected later, with minimal additional integration efforts required.

[0040] Figure 6 illustrates an example high-level functional block diagram of a vehicle charging system 600 capable of both wired and wireless power transfer between the EV and appropriate charging stations. The ground side is shown as including both an EVSE 602 and a GA 502 connected to the power supply 504. While some charging stations may include both mechanisms, only one is generally used at a time, and the systems described do not require any connection or interrelation between systems on the ground side. The GA may be any of the WPT systems shown in Figures 1-4, and the EVSE may be any of the wired systems shown in Figures 2-4, for example.

[0041] The vehicle charging system 600 includes a simplified VA 620 and a wireless-capable on-board charger (WOBC) 630, which provides power to the battery 550. Many other devices are also included in the vehicle, but are not shown for simplicity. The vehicle can exchange Attorney Docket No. P0495PCTWNPR1 13WiTricity Ref. P0495PCT-W-NPR1power with the ground side through either a wired connection 606 to the EVSE 602 or a wireless power transfer field 608 between the GA 502 and the VA 620. In the example of Figure 6, the VA 620 is coupled to the WOBC 630, which is in turn coupled to the battery 550. As described in more detail below, the WOBC 630 converts the power received from either the EVSE 602 or the VA 620 into DC power appropriate for charging the battery 550, or, in a V2x configuration, it converts DC power from the battery 550 into either an LF power signal for wireless transfer from the VA 620 to the GA 502, or whichever type of AC or DC power signal the EVSE 602 requires over the wired connection 608. As a general example, the WOBC 630 includes an AC-DC converter 632 and a DC-DC converter 634. Each of those may be implemented as multiple power conversion components and related electronics. Additionally, the WOBC 630 includes a DC bypass 640, that allows a DC EVSE to connect directly to the battery 550. Relays within the DC bypass also prevent the DC output from the OBC from coupling to the input connection 606 when used with an AC power supply. Additional components, such as EMI filters, are not shown. The power from the VA 620 may be inserted into the WOBC's wired charging path at various points. In this example, the WOBC also includes inductors 616 used by the VA to tune output power. Including the inductors 616 in the WOBC allows use of the WOBC's existing water-cooling systems to cool the inductors 616, avoiding the need to provide water cooling connections to the VA. In subsequent figures detailing the inner workings of the vehicle charging system, details of the power supply 504, EVSE 602, GA 502, wired link 606, wireless power transfer field 608, and battery 550 are not considered, and so only the connections 606, 608 are shown.

[0042] Figures 7-11 illustrate various block and circuit diagrams relating to the integration of WPT into the OBC. Coupling the WPT, for example, to an electric vehicle via the OBC may occur in various embodiments. For example, the block diagrams, circuit diagrams, and components thereof as disclosed herein can be similar or identical to and / or incorporate any of the features, components, designs, or any other aspect as described and / or illustrated with respect to any of the devices, assemblies, and / or systems described and / or illustrated in U.S. Provisional Application No. 63 / 556,601, and titled "DUAL SOURCE ON-BOARD CHARGING SYSTEM FOR WIRELESS POWER TRANSFER" incorporated by reference herein.Attorney Docket No. P0495PCTWNPR1 14WiTricity Ref. P0495PCT-W-NPR1

[0043] Figure 7 illustrates a block diagram of an example center-tapped configuration for integrating WPT into the OBC (e.g., OBC 700). In some examples, OBC and WPT combination may occur with a center-tapped transformer configuration. In this configuration, VA coil 702 and IMN 704 are connected to center taps on an isolation transformer 706 between the two sides of the OBC 700. In the illustrated example, the OBC 700 includes a first power converter 708 coupled and a second power converter 710. The first power converter 708 can operate as a power factor correction (PFC) converter, an inverter, or rectifier. The second power converter 710 can operate as a rectifier or an inverter, complementary to the operation of the first power converter 708. The first power converter 708 is coupled to a first power interface 712 and the transformer 706. The first power interface 706 is associated with an alternating current grid (ACGRID) or DC charger (e.g., DC fast charger) 714. The second power converter 710 is coupled to the transformer 706 and a power source, such as an electric vehicle power source (e.g., battery 716).

[0044] The center-tapped transformer configuration may provide reduced hardware components while continuing to provide various sources of power for the OBC. In some cases, the center-tapped configuration may allow reduction in relays and rectifiers to the overall hardware design. Additionally, in some examples, the center-tapped transformer configuration may reduce additional inductors, as compared to other embodiments as described herein. The center-tapped transformer configuration may allow for reduced complexity in controlling whether the OBC operates in various modes. For example, the center-tapped configuration may use an H-bridge modulation as the OBC, reducing the hardware design complexities to include the WPT. In some examples, the center-tapped transformer configuration may include a plurality of modes of operation. For example, the modes of operation may include a first mode and a second mode. In some examples, the first mode may be an OBC operation and the second mode may be WPT operation.

[0045] Figure 8 illustrates an example circuit diagram for implementing the block diagram as illustrated in Figure 7. In the example of Figure 8, OBC 800 is an example of OBC 700 and includes four switches Si through S4 implementing a Power Factor Correction (PFC) stage, fourAttorney Docket No. P0495PCTWNPR1 15WiTricity Ref. P0495PCT-W-NPR1switches S5 through Sg, implementing an H-bridge inverter or bi-directional inverter-rectifier, and four switches S9 through S12, implementing an H-bridge rectifier or bi-directional inverterrectifier. Isolation transformer Ti 806 is shown as an equivalent circuit with a turn ratio of 1:1:1:1 and has two taps at points A and B where VA 810, including VA coil 802 and IMN 804, are connected. The isolation transformerTi 806 is an example of the transformer 706 in Figure 7. VA coil 802 and IMN 804 are examples of the VA coil 702 and the IMN 704, respectively, in Figure 7. Relays 820 for connecting a DC fast charger directly to the battery are also closed for wireless charging, as described below. The transformer Ti 806 includes first power interface comprising a first set of windings (e.g., Li, L3, Lm) between a first pair of terminals, a second power interface comprising a second set of windings (e.g., L2, U, Lm) between a second pair of terminals, and a center-tapped power interface comprising connections from a third pair of terminals to points within the first and second sets of windings.

[0046] Figure 9 illustrates an example circuit diagram of the OBC circuit 800 from Figure 8, configured for the first mode of operation of the center-tapped transformer configuration; the OBC operation. The OBC operation may result in a differential mode of transformer operation. In the OBC operation, a plurality of switches may be in various states, as follows:• SO: off (not shown)• S1-S4 (Figure 8): totem-pole PFC, shown as current source IPFC• S5 & S8, S6 & S7: 180° phase-shifted H-Bridge (HB)• S9 & S12, S10 & Sil: 180° phase-shifted HB.

[0047] In some cases, the OBC operation may result in reduced current flows between A and B. In some cases, while in OBC operation, the circuit can be characterized as a CLLLC converter, and operates at a resonant frequency, such that the voltage at the PFC input is the same as the voltage at the battery, i.e.:• Vci = Vbat.

[0048] In some cases, when S5, S8, S9, S12 are in an "on" state, the voltage is as follows:• VA = Vci / 2• VB = Vbat / 2.

[0049] In some cases, when S6, S7, S10, Sil are in an "on" state, the voltage is as follows: Attorney Docket No. P0495PCTWNPR1 16WiTricity Ref. P0495PCT-W-NPR1• VA= -Vci / 2• VB = -Vbat / 2.

[0050] In this manner, during OBC operation, the voltages are equivalent (or substantially equivalent). Thus, in this operation, no current flows between A and B. The lack of current flowing allows for reducing hardware components, such as relays. In some cases, in the OBC operation, there is a reduced current flowing between A and B due to difference in deadtime, rise and fall time of switching, among other factors relating to the differential mode of the transformer. In some examples, the current frequency for the OBC operation may be different from 85 kHz (used in WPT). The block diagrams, circuit diagrams, and components thereof as disclosed herein can be similar or identical to or incorporate any of the features, components, designs, or any other aspect as described or illustrated with respect to any of the devices, assemblies, or systems described or illustrated in U.S. Provisional Application No. 63 / 556,601, and titled "DUAL SOURCE ON-BOARD CHARGING SYSTEM FOR WIRELESS POWER TRANSFER" incorporated by reference herein.

[0051] Figure 10 illustrates an example circuit diagram of the OBC circuit 800 from Figure 8, configured for the second mode of operation of the center-tapped transformer configuration; the WPT operation. The WPT operation may result in a common mode of transformer operation. In the WPT operation, a plurality of switches may be in various states, as follows:• SO, SI, S4: on, S2, S3: off (this configuration is shown as a continuous connection 1002 across the top and bottom rails of the circuit)• S5 & S6, S7 & S8: adjustable phase-shifted HB• S9 & S10, Sil & S12: adjustable phase-shifted HB.

[0052] In some cases, the state configuration of the switches, such as S5 & S6, S9 & S10, S7 & S8, Sil & S12 may form a typical HB, allowing for ease of modulation and control. The circuit of the WPT operation may result in leakage inductance (LI, L3, L2, L4), which may be used as L3d (I B), and thus, there may be no need for L3d. In some cases, the resonant capacitors in the CLLLC configuration (C2, C4, C3, C5) may be adjusted to achieve the required impedance for WPT (in this way, the frequency may be adjustable from 85 kHz). In this way,Attorney Docket No. P0495PCTWNPR1 17WiTricity Ref. P0495PCT-W-NPR1the current (li_3d) between A and B is shared between one or more of the rectifiers. For example, allowing for a reduction in rectifier conduction loss. In some cases, the rectifier conduction loss is reduced at or between 0%-100%, such as 50%.

[0053] Figure 11 illustrates an example circuit diagram illustrating an equivalent (or substantially equivalent) circuit in Figure 10, with the components re-arranged to show the topology from a wireless power transfer point of view alone. The block diagrams, circuit diagrams, and components thereof as disclosed herein can be similar or identical to or incorporate any of the features, components, designs, or any other aspect as described or illustrated with respect to any of the devices, assemblies, or systems described or illustrated in U.S. Provisional Application No. 63 / 556,601, and titled "DUAL SOURCE ON-BOARD CHARGING SYSTEM FOR WIRELESS POWER TRANSFER" incorporated by reference herein.

[0054] Figures 12-14 show the results of a simulation of operation of the above circuitry. In Figure 12, circuit 1200 represents the OBC circuitry of Figures 7-11, starting from the PFC input 1202 to the inverter 1204. The relays 1206 for connecting the DC charger are shown above and below the center-tapped transformer 1210 and are closed during wireless operation. In addition, circuit 1250 represents a WPT system, including the ground-side inverter 1252, impedance matching network 1254, and GA coil 1256. On the vehicle side, VA coil 1260 and impedance matching network 1262 are connected to the center-tapped transformer 1210 of the OBC circuit 1200 via nodes labelled V_WPT_A and V_WPT_B.

[0055] Figure 13 shows the results of the simulation when the OBC circuit 1200 is used in wired-charging mode. Circuit 1300 corresponds to Figure 9, above. As shown by the voltage and current traces 1302, 1304, 1306, 1308, 1310, and 1312, zero-voltage switching (ZVS) is achieved for all switches, Vci = Vbat, sinusoidal resonant currents are achieved, and no current flows between transformer center taps A and B.

[0056] Figure 14 shows the results of the simulation when the OBC circuit 1200 is used in WPT mode, with passive vehicle-side rectification. Circuit diagram 1402 corresponds to Figure 10, above, with the addition of circuitry 1404 representing the GA power supply, inverter,Attorney Docket No. P0495PCTWNPR1 18WiTricity Ref. P0495PCT-W-NPR1IMN, and coil. As shown by the voltage and current traces 1410, 1412a, 1414b, and 1416, and enlarged versions 1412b and 1414b, the inductor current is shared between the two rectifiers, giving a 50% reduction in rectifier conduction losses. It should be noted that the solid regions in traces 1412a and 1414a are in fact waveforms, as shown in the enlarged versions, but are too dense to differentiate the curves in the non-enlarged figures. The trace for current ILM is shown as a white dashed line to make it visible as it is aligned directly on the x-axis.

[0057] The various illustrative logical blocks, modules, circuits, and methods described in connection with the examples disclosed above may be implemented as electronic hardware, computer software, or combinations of both. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. The described functionality may be implemented in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the described aspects. The various illustrative blocks, modules, and circuits described in connection with disclosed controllers may be implemented or performed with a general-purpose hardware 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. A general-purpose hardware processor may be a microprocessor, but in the alternative, the hardware processor may be any conventional processor, controller, microcontroller, or state machine. A hardware processor may also be implemented as a combination of computing devices.

[0058] The steps of a method and functions described above may be embodied directly in hardware, in a software module executed by a hardware processor, or in a combination of the two. If implemented in software, the functions may be stored on or transmitted as one or more instructions or code on a tangible, non-transitory, computer-readable medium. AAttorney Docket No. P0495PCTWNPR1 19WiTricity Ref. P0495PCT-W-NPR1software module may reside in Random Access Memory (RAM), flash memory, Read-Only Memory (ROM), or any other form of storage medium known in the art. A storage medium is coupled to the hardware processor such that the hardware processor can read information from, and write information to, the storage medium. In another example, the storage medium may be integral to the hardware processor. The hardware processor and the storage medium may reside in an ASIC.

[0059] Unless context dictates otherwise, items represented in the accompanying figures and terms may represent one or more items or terms, and thus reference may be made interchangeably to single or plural forms of the items and terms in this written description. Although subject matter has been described in language specific to structural features or methodological operations, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or operations described above, including not necessarily being limited to the organizations in which features are arranged or the orders in which operations are performed. For example, the context of the above description is wireless charging of electric vehicles, but these techniques may be used in other situations where it is desired to integrate a wireless power supply to a device that is otherwise powered through a wired connection, or vice-versa.

[0060] A number of implementations have been described. Nevertheless, it will be understood that additional modifications may be made without departing from the scope of the concepts described herein, and, accordingly, other embodiments are within the scope of the following claims.Attorney Docket No. P0495PCTWNPR1 20

Claims

WiTricity Ref. P0495PCT-W-NPR1WHAT IS CLAIMED IS:

1. An apparatus for transferring power, the apparatus comprising:a transformer (706, 806) having a first power interface comprising a first set of windings between a first pair of terminals, a second power interface comprising a second set of windings between a second pair of terminals, and a center-tapped power interface comprising connections from a third pair of terminals to points within the first and second sets of windings;a battery interface comprising connection points for transferring power to or from a battery;a wired charging interface comprising a wired charging connection for connecting to an external charger, and an internal power connection;a first power converter coupled between the internal power connection and the first power interface of the transformer;a second power converter coupled between the second power interface of the transformer and the battery interface;a set of bypass relays (820) for selectively connecting the wired charging connection to the battery interface; anda first wireless power transfer (WPT) assembly (810), comprising a WPT coil (802) and a WPT impedance matching network (IMN) (804), and a pair of WPT interface terminals,wherein the WPT interface terminals are coupled to the third pair of terminals of the transformer.Attorney Docket No. P0495PCTWNPR1 21WiTricity Ref. P0495PCT-W-NPR12. The apparatus of claim 1, wherein:in a first mode of operation, when a source or consumer of AC power is connected to the wired charging interface, the bypass relays are opened, the first power converter operates as an inverter or rectifier, the transformer operates as an isolation transformer, and the second power converter operates as a rectifier or an inverter, complementary to the operation of the first power converter, providing for a transfer of power between the battery and the source or consumer of AC power.

3. The apparatus of claim 1, whereinin a second mode of operation, when a second WPT assembly is wirelessly coupled to the first WPT assembly, the bypass relays are closed, and the first power converter, second power converter, and transformer operate collectively providing for a transfer of power between the battery and the second WPT assembly.

4. The apparatus of claim 3, wherein:the first power converter comprises a power factor correction (PFC) converter, and during the second mode of operation, the PFC converter is configured to couple the bypass relays directly to the internal power connection.

5. An apparatus for transferring power, the apparatus comprising:a transformer assembly;a first power converter coupled to a first power interface and the transformer assembly, wherein the first power interface is associated with an alternating current grid or direct current charger;a second power converter coupled to the transformer assembly and an electric vehicle power source; andAttorney Docket No. P0495PCTWNPR1 22WiTricity Ref. P0495PCT-W-NPR1an impedance matching network coupled to a second power interface and the transformer assembly, wherein the second power interface is associated with a wireless power source,wherein the impedance matching network is coupled to the transformer assembly with a center-tapped configuration, in which the impedance matching network and the transformer assembly are coupled via connection points between a plurality of inductors of the transformer assembly.

6. The apparatus of claim 5, wherein the apparatus is configured to operate in a plurality of modes, the plurality of modes comprising a differential mode of the transformer assembly and a common mode of the transformer assembly.

7. The apparatus of claim 6, wherein the differential mode of the transformer assembly causes voltage between the first power converter and the second power converter to be equivalent to each other.

8. The apparatus of claim 6, wherein the first power converter and the second power converter each comprise a rectifier, and wherein the common mode of the transformer assembly distributes current between the two rectifiers.

9. The apparatus of claim 8, wherein the impedance matching network comprises a first of the two rectifiers and the second power converter comprises a second of the two rectifiers.

10. A method of operating an apparatus for transferring power, the method comprising:operating the apparatus in a first mode of operation or a second mode of operation, the apparatus including:a transformer (706, 806) having a first power interface comprising a first set of windings between a first pair of terminals, a second power interface Attorney Docket No. P0495PCTWNPR1 23WiTricity Ref. P0495PCT-W-NPR1comprising a second set of windings between a second pair of terminals, and a center-tapped power interface comprising connections from a third pair of terminals to points within the first and second sets of windings; a battery interface comprising connection points for transferring power to or from a battery;a wired charging interface comprising a wired charging connection for connecting to an external charger, and an internal power connection; a first power converter coupled between the internal power connection and the first power interface of the transformer;a second power converter coupled between the second power interface of the transformer and the battery interface;a set of bypass relays (820) for selectively connecting the wired charging connection to the battery interface; anda first wireless power transfer (WPT) assembly (810), comprising a WPT coil (802) and a WPT impedance matching network (IMN) (804), and a pair of WPT interface terminals,wherein the WPT interface terminals are coupled to the third pair of terminals of the transformer;in the first mode of operation, when a source or consumer of AC power is connected to the wired charging interface, transferring power between the battery and the source or consumer of AC power by:opening the bypass relays;operating the first power converter as an inverter or rectifier; andoperating the second power converter as a rectifier or an inverter, complementary to the operation of the first power converter, andAttorney Docket No. P0495PCTWNPR1 24WiTricity Ref. P0495PCT-W-NPR1in the second mode of operation, when a second WPT assembly is wirelessly coupled to the first WPT assembly, transferring power between the battery and the second WPT assembly by:closing the bypass relays; andoperating the first power converter and second power converter collectively to convert between DC power at the battery and high-frequency power at an operating frequency of the WPT interfaces.Attorney Docket No. P0495PCTWNPR1 25

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