Abstract: A system and method to detect the presence of conductive foreign objects for a multi-coil wireless power system is described. A wireless power receiver resonant circuit quality information may be obtained without any costly hardware or termination of power delivery to the power receiver load. The power receiver free-running coil current or voltage may be measured during a very short time window. In this time window, the measurement may be unaffected by transmitter and receiver load due to the transmitter coil disconnection and because the wireless power receiver has sufficient DC-bus capacitance.

Abstract: A power-transmitter-unit comprises a power-transmitting-coil and a resonant-capacitor that define an LC circuit. A controller defines a power-transmission-mode of operation and a foreign-object-detection-mode of operation. In the power-transmission-mode of operation: a power-stage provides a potential-difference across a first-end and a second-end of the LC circuit. In the foreign-object-detection-mode of operation: for a recuperation-time-interval, the power-stage provides a potential-difference across the first-end and the second-end of the LC circuit that has the opposite polarity to the current through the power-transmitting-coil; after expiry of the recuperation-time-interval, the first-end of the LC circuit is connected to the second-end of the LC circuit such that the LC circuit is short-circuited and defines a closed-LC-circuit; and the controller receives measured-signalling that is representative of an operating parameter of the power-transmitter-unit.

Abstract: A system and method to detect the presence of conductive foreign objects for a multi-coil wireless power system is described. A wireless power receiver resonant circuit quality information may be obtained without any costly hardware or termination of power delivery to the power receiver load. The power receiver free-running coil current or voltage may be measured during a very short time window. In this time window, the measurement may be unaffected by transmitter and receiver load due to the transmitter coil disconnection and because the wireless power receiver has sufficient DC-bus capacitance.

Abstract: A power-transmitter-unit includes a power-transmitting-coil for wirelessly providing power to a power-receiver-unit, and a resonant-capacitor connected to the power-transmitting-coil, such that together they define an LC circuit. The LC circuit includes a first-end and a second-end. A controller defines a foreign-object-detection-mode of operation, wherein, in the foreign-object-detection-mode of operation, the first-end of the LC circuit is connected to the second-end of the LC circuit such that the LC circuit is short-circuited and defines a closed-LC-circuit, and the controller is configured to receive a coil-current-signal that is representative of the current through the closed-LC-circuit.

Abstract: Foreign object detection (FOD) is provided for wireless energy transfer systems. A transmitter receives an input voltage, converts it to an output current, supplies the output current to a transmit coil, and samples a first set of analog signals to generate a first set of digital values. A receiver converts a current induced in a receive coil by energy transferred from the transmit coil into an output voltage, samples a second set of analog signals to generate a second set of digital values, and communicates the second set of digital values to the transmitter. The transmitter generates a FOD signal based upon the first and second sets of digital values that indicates detection or non-detection of a foreign object within the energy transfer. In further embodiments, a comparison of the detected power loss or efficiency to expected power loss or efficiency is used to generate the FOD signal.

Abstract: A power-transmitter-unit comprises a power-transmitting-coil and a resonant-capacitor that define an LC circuit. A controller defines a power-transmission-mode of operation and a foreign-object-detection-mode of operation. In the power-transmission-mode of operation: a power-stage provides a potential-difference across a first-end and a second-end of the LC circuit. In the foreign-object-detection-mode of operation: for a recuperation-time-interval, the power-stage provides a potential-difference across the first-end and the second-end of the LC circuit that has the opposite polarity to the current through the power-transmitting-coil; after expiry of the recuperation-time-interval, the first-end of the LC circuit is connected to the second-end of the LC circuit such that the LC circuit is short-circuited and defines a closed-LC-circuit; and the controller receives measured-signalling that is representative of an operating parameter of the power-transmitter-unit.

Abstract: A power-transmitter-unit includes a power-transmitting-coil for wirelessly providing power to a power-receiver-unit, and a resonant-capacitor connected to the power-transmitting-coil, such that together they define an LC circuit. The LC circuit includes a first-end and a second-end. A controller defines a foreign-object-detection-mode of operation, wherein, in the foreign-object-detection-mode of operation, the first-end of the LC circuit is connected to the second-end of the LC circuit such that the LC circuit is short-circuited and defines a closed-LC-circuit, and the controller is configured to receive a coil-current-signal that is representative of the current through the closed-LC-circuit.

Abstract: A wireless charging transmitter has a phase-shift controlled inverter, a capacitor, a transmitter coil, and a control circuit. The phase-shift controlled inverter has an input for receiving a phase-shift signal, and first and second output terminals for providing an inverter output voltage. The capacitor has a first terminal coupled to the first output terminal of the phase-shift controlled inverter, and a second terminal. The transmitter coil having a first terminal coupled to the second terminal of the capacitor, and a second terminal coupled to the second terminal of the phase-shift controlled inverter. The control circuit has an input coupled to the second terminal of the capacitor for sampling a capacitor voltage of the capacitor, and an output for providing the phase-shift signal corrected for the phase error. The control circuit determines the phase error of the capacitor voltage relative to a phase of an inverter output voltage to ensure the wireless charging transmitter operates in resonance.

Abstract: Foreign object detection (FOD) is provided for wireless energy transfer systems. A transmitter receives an input voltage, converts it to an output current, supplies the output current to a transmit coil, and samples a first set of analog signals to generate a first set of digital values. A receiver converts a current induced in a receive coil by energy transferred from the transmit coil into an output voltage, samples a second set of analog signals to generate a second set of digital values, and communicates the second set of digital values to the transmitter. The transmitter generates a FOD signal based upon the first and second sets of digital values that indicates detection or non-detection of a foreign object within the energy transfer. In further embodiments, a comparison of the detected power loss or efficiency to expected power loss or efficiency is used to generate the FOD signal.

Abstract: A wireless charging transmitter has a phase-shift controlled inverter, a capacitor, a transmitter coil, and a control circuit. The phase-shift controlled inverter has an input for receiving a phase-shift signal, and first and second output terminals for providing an inverter output voltage. The capacitor has a first terminal coupled to the first output terminal of the phase-shift controlled inverter, and a second terminal. The transmitter coil having a first terminal coupled to the second terminal of the capacitor, and a second terminal coupled to the second terminal of the phase-shift controlled inverter. The control circuit has an input coupled to the second terminal of the capacitor for sampling a capacitor voltage of the capacitor, and an output for providing the phase-shift signal corrected for the phase error. The control circuit determines the phase error of the capacitor voltage relative to a phase of an inverter output voltage to ensure the wireless charging transmitter operates in resonance.