Abstract: One general aspect includes methods, systems, and apparatus, including computer programs encoded on a computer storage medium, for fault protection of a bidirectional wireless power transfer system. The method includes the actions of detecting, by control circuitry of a wireless power transfer device, a fault for the bidirectional wireless power transfer system. Identifying an operating personality of the wireless power transfer device and a hardware configuration of the wireless power transfer device. Identifying, in response to detecting the fault and based on the operating personality and the hardware configuration, protection operations for protecting the wireless power transfer device from the fault. Controlling operations of the wireless power transfer device according to the protection operations.

Abstract: Methods, systems, and devices for protecting a wireless power transfer system. One aspect features a sensor network for a wireless power transfer system. The sensor network includes a differential voltage sensing circuit and a current sensing circuit. The differential voltage sensing circuit is arranged within a wireless power transfer system to measure a rate of change of a voltage difference between portions of an impedance matching network and generate a first signal representing the rate of change of the voltage difference. The current sensing circuit is coupled to the differential voltage sensing circuit and configured to calculate, based on the first signal, a current through a resonator coil coupled to the wireless power transfer system.

Abstract: Disclosed herein are systems and methods for determining a current of a resonator coil during operation of a wireless power system having the resonator coil, in which the resonator coil is coupled to a fixed capacitive network and a reactance circuit. The systems and methods can include determining a first signal which can include receiving a current in an inductor of the reactance circuit; converting the current to a voltage signal; and scaling the voltage signal. The systems and methods can include determining a second signal which can include receiving an output voltage at an output of the reactance circuit; dividing the output voltage; and integrating the divided scaled voltage to produce an inverted differentiated voltage signal. The methods can include summing the first signal and the second signal to produce a summed signal; and determining the current in the resonator coil based on the summed signal.

Abstract: In certain aspects, an enclosure for a wireless power transfer pad is disclosed. The enclosure includes a cover shell configured to be positioned over a portion of the wireless power transfer pad configured to face a wireless power receiver when wirelessly transferring power, wherein at least a portion of the cover shell is made of a heat resistant material.

Abstract: A wireless electric vehicle charging system comprises base-side equipment for generating a magnetic field and vehicle-side equipment for receiving energy via the magnetic field to supply power to a vehicle-driving battery. Monitoring circuitry monitors one or more of voltage, current, or phase associated with the base-side equipment and halts generation of the magnetic field in response to a change in the voltage, current, or phase associated with the operation of the base-side equipment that indicates a fault condition at the vehicle-side equipment, which may include a loss of power or disconnection of a battery. Based on detection of the change, the monitoring circuitry can halt generation of the magnetic field to prevent damage at the vehicle-side equipment.

Abstract: The present disclosure describes techniques for detecting foreign objects. In some aspects, an apparatus for detecting objects is provided. In particular, the apparatus includes a circuit for measuring changes of a mutual impedance between sense coils of a plurality of sense circuits. The described implementations relate to configurations for driving and measurement circuitry for one or more sense circuits that allow for higher accuracy, sensitivity, and temperature stability as needed for detecting smaller objects. Implementations based on mutual impedance sensing allow for improved detection sensitivity e.g., in a presence of strong temperature variations such as may be experienced in an outdoor environment. The apparatus includes a driver circuit, a measurement circuit, and a plurality of sense circuits, each of the plurality of sense circuits including a primary sense coil, a secondary sense coil, and a capacitor connected to each of the primary sense coil and the secondary sense coil.

Abstract: A multi-purpose detection circuit for object detection and vehicle position determination is described. For example, the circuit is configurable for detecting foreign metallic objects, living objects, and a vehicle or type of vehicle above an inductive wireless power transmitter. The circuit is also configurable for determining the vehicle's position relative to the inductive wireless power transmitter. An example apparatus includes a measurement circuit including a multiplexer, electrically connected to a plurality of inductive and capacitive sense circuits, for measuring one or more electrical characteristics in each of the inductive and capacitive sense circuits according to a predetermined time multiplexing scheme.

Abstract: Systems and methods are described that reduce magnetic flux density proximate to a wireless charging pad, such as a WEVC pad. These systems and methods control peak magnetic flux density in air around a WEVC pad to reduce potentially dangerous heat produced in foreign metal objects affected by a magnetic field generated by a coil of the WEVC pad. Controlling the peak magnetic flux density results in a safer WEVC pad. Aspects include ferrite tiles being separated by gaps having predefined sizes to increase a magnetic reluctance of a path of the magnetic flux through the ferrite tiles, which reduces a peak magnetic flux density experienced in areas proximate to the coil. In addition, the ferrite tiles can be arranged such that a combination of gaps are aligned with a region overlapping the coil.

Abstract: An apparatus is disclosed for a hybrid foreign-object detection and position system. In an example aspect, a foreign object detection (FOD) system of the base power-transfer system detects a passive beacon of an electric vehicle power-transfer system based on a beacon loop of the passive beacon overlapping an array of FOD sense loops effective to cause a change in impedance or admittance of one or more of the FOD sense loops. In aspects, the impedance reflects a modulation signal from the passive beacon. A position detection system integrated with the FOD system determines a passive beacon response in the input data based on the modulation frequency from the passive beacon. Then, a position of the beacon loop is determined relative to the array of FOD sense loops using a result of the passive beacon response canceled from input data.

Abstract: Systems and methods are described for extended foreign object detection (FOD) signal processing. In aspects, an oscillator reset is implemented in a FOD system to mitigate the effects of intermodulation products. In addition, dynamic frequency allocation is implemented to avoid high noise desensitizing the FOD system. Also, a slow sampling mode is implemented to increase a tolerance to transient foreign objects. Reference tracking and auto-recovery is implemented to bridge power outages. Additionally, the FOD system is configured to support position finding for determining an alignment between the vehicle pad and the base pad using a passive beacon transponder circuit and to perform beacon response cancellation as needed in concurrent FOD operation.

Abstract: The disclosure features wireless energy transfer sources that include at least two source resonators and a power source, where: each of the at least two source resonators has a nominal impedance when a device resonator is not positioned on or near any of the at least two source resonators, the nominal impedances of each of the at least two source resonators varying by 10% or less from one another; and the at least two source resonators are configured so that during operation of the wireless energy transfer source, when a device resonator is positioned on or near a first one of the at least two source resonators: (a) the impedance of the first source resonator is reduced to a value smaller than the nominal impedances of each of the other resonators by a factor of 2 or more.

Abstract: Methods, systems, and devices for controlling a variable capacitor. One aspect features a variable capacitance device that includes a capacitor, a first transistor, a second transistor, and control circuitry. The control circuitry is configured to adjust an effective capacitance of the capacitor by performing operations including detecting a zero-crossing of an input current at a first time. Switching off the first transistor. Estimating a first delay period for switching the first transistor on when a voltage across the capacitor is zero. Switching on the first transistor after the first delay period from the first time. Detecting a zero-crossing of the input current at a second time. Switching off the second transistor. Estimating a second delay period for switching the second transistor on when a voltage across the capacitor is zero. Switching on the second transistor after the second delay period from the second time.

Abstract: Certain aspects of the present disclosure provide methods and apparatus for multi-phase coil control in power transfer systems. One example power transfer device generally includes a plurality of coils configured to generate at least one charging field, the plurality of coils comprising a first coil and a second coil, and a controller configured to identify that a coupling factor between the first coil and a third coil, which is external to the power transfer device, is at or below a threshold, and to adjust, based on the identification, one or more parameters associated with a current applied to the first coil to transfer power from the first coil to the second coil.

Abstract: In certain aspects, methods and systems for controlling power transfer at a wireless power receiver are disclosed. In certain aspects, a method includes determining a duty cycle of a DC-DC converter of the wireless power receiver. The method further includes determining a duty cycle limit for an AC switching controller based on the determined duty cycle. The method further includes determining an operational duty cycle for the AC switching controller. The method further includes comparing the operational duty cycle to the duty cycle limit. The method further includes adjusting at least one of a desired voltage and current input to the DC-DC converter when the operational duty cycle is greater than the duty cycle limit.

Abstract: Systems and methods are described for thermal feedback for power transfer optimization. Aspects include a wireless power-transfer system including a base power-transfer apparatus, a power supply unit, at least one temperature sensor, and a system controller. The base power-transfer apparatus includes a coil configured to generate a magnetic field based on an electric current. The power supply unit includes switching and power electronics configured to drive the electric current in the coil. The temperature sensor(s) are configured to measure a temperature of the base power-transfer apparatus or the power supply unit. The system controller is coupled to the base power-transfer apparatus, the power supply unit, and the temperature sensor(s) and is configured to control operation of at least one of the base power-transfer apparatus or the power supply unit based on the measured temperature to shift losses and dissipate heat in the base power-transfer apparatus or the power supply unit.

Abstract: Systems and methods are described for active harmonics cancellation. A wireless charging apparatus includes a wireless-power transfer circuit comprising a wireless-power transfer coil configured to generate or couple to a magnetic field to transfer or receive power and a plurality of tuning capacitors electrically coupled to the wireless-power transfer coil. The apparatus also includes a power converter circuit electrically coupled to the wireless-power transfer circuit. Additionally, the apparatus includes a signal generation circuit different from the power converter circuit and electrically coupled to one or more nodes between capacitors of the plurality of tuning capacitors. The signal generation circuit is configured to generate and inject a signal into the wireless-power transfer circuit at the nodes between the capacitors. The signal generation circuit includes a rejection filter tuned to an operating frequency of the wireless-power transfer coil.

Abstract: Systems and methods are described for a flush mount wireless charging power-transfer system. The techniques described in this document provide high mutual inductance with low leakage fields. These techniques also provide low surface flux densities in a base power transfer system, particularly for a component of a magnetic field that is tangential to the surface of the base power transfer system. Aspects include mechanical gaps located between ferrite structures in the coil window in the base power transfer system, and protrusions of ferrite on opposing sides of each gap. In addition, ferrite extensions are located beyond an outer boundary of the coil (e.g., in an x-direction) and extend upward above the plane of the coil (e.g., in a z-direction). The gaps, protrusions, and extensions separate the main flux from the side flux, reduce flux leakage, and improve mutual inductance between the base pad and a vehicle pad.

Abstract: The present disclosure describes techniques for estimating or measuring changes in peak magnetic flux levels based on the influence of a receive coil to the overall flux density over a transmit coil. The estimated or measured changes in peak magnetic flux levels are used to adjust currents in the coils to reduce the flux density while maintaining sufficient power transfer. In some aspects, an apparatus for controlling power transfer is provided. The apparatus includes a controller configured to receive or determine a measured or estimated magnetic flux level on or outside a housing configured to house a transmit coil. The controller is further configured to determine an electrical current level for at least one or both of the transmit coil or a receive coil that reduces a peak magnetic flux density level in proximity to the transmit coil based on the measured or estimated magnetic flux level.

Abstract: A wireless power receiver includes one or more tunable capacitors in parallel with an inductor. The wireless power receiver adapted to receive an induced voltage input at the inductor due to a magnetic field generated by a wireless power transmitter. The rectifier has an output with a rectified voltage and a rectified current. A controller has a first input for receiving a signal representative of the rectified voltage and a first output for supplying an adjustment signal to the tunable capacitor. The controller includes a processor coupled to the first input and is configured to operate on the signal representative of rectified voltage to produce a desired capacitance value for capacitor and provide the adjustment signal determined so as to adjust a capacitance value of capacitor to the desired capacitance value.

Abstract: In certain aspects, methods and systems for converting DC power to AC power by a wireless power receiver are disclosed. Certain aspects provide a wireless power receiver including a resonant circuit. The wireless power receiver includes a first switching circuit coupled to the resonant circuit, the first switching circuit configured to act as an inverter and generate a first signal, based on an output from a battery, at a resonant frequency of the resonant circuit, the first signal having an envelope at a first frequency. The wireless power receiver includes a second switching circuit coupled to the resonant circuit that is configured to bias the second switching circuit at the resonant frequency in response to the first signal, wherein the second switching circuit is configured to act as a rectifier and is configured to extract the envelope to generate a second signal at half of the first frequency.