Abstract: Metal object detection may be performed in a wireless power system by monitoring the 5th or other order harmonic current of a dual-frequency power transmitter driven by a voltage-fed inverter with square-wave output. While power transfer is maintained by tuning at the fundamental frequency, the transmitter circuit is tuned simultaneously at the 5th order frequency or other harmonic frequencies to increase or decrease the flow of the harmonic current for when a metal object is present. The receiver circuit may include a notch filter to filter out the 5th order frequency. With the dual-frequency tuning configuration, the presence of a metal object causes a significant drop of the increase in the harmonic current at the transmitter side while the receiver behaves as an open circuit with no effect on power transfer. The harmonic tuning circuit may be switched off as necessary to leave only the fundamental frequency for power transfer.

Abstract: A wireless power system has a wireless power transmitting device and a wireless power receiving device. The wireless power transmitting device may include a coil and wireless power transmitting circuitry coupled to the coil. The wireless power transmitting circuitry may include impulse response measurement circuitry that measures the inductance of the power transmitting coil and the quality factor of the power transmitting coil. The measured inductance and quality factor may subsequently be used to determine a position of the wireless power receiving device relative to the wireless power transmitting device. The determined position of the wireless power receiving device relative to the wireless power transmitting device may be used to estimate an expected power loss associated with the power transmitting coil. The power transfer operations may be adjusted based on expected and actual power losses.

Abstract: Metal object detection may be performed in a wireless power system by monitoring the 5th or other order harmonic current of a dual-frequency power transmitter driven by a voltage-fed inverter with square-wave output. While power transfer is maintained by tuning at the fundamental frequency, the transmitter circuit is tuned simultaneously at the 5th order frequency or other harmonic frequencies to increase or decrease the flow of the harmonic current for when a metal object is present. The receiver circuit may include a notch filter to filter out the 5th order frequency. With the dual-frequency tuning configuration, the presence of a metal object causes a significant drop of the increase in the harmonic current at the transmitter side while the receiver behaves as an open circuit with no effect on power transfer. The harmonic tuning circuit may be switched off as necessary to leave only the fundamental frequency for power transfer.

Abstract: A wireless power system has a wireless power transmitting device and a wireless power receiving device. During digital ping operations while the transmitting device and receiving device negotiate to establish a power level to use during normal operation, low-power wireless power signals may be transmitted to the receiving device from the wireless power transmitting device. Information gathered during the digital ping may be evaluated using a wireless-power-transmission-efficiency-to-digital-ping-rectifier-output-voltage relationship and using a normal-operation-wireless-power-transmission-efficiency-to-digital-ping-wireless-power-transmission-efficiency relationship to predict a wireless power transmission efficiency that would be experienced if the system were to enter normal operation. Based on this efficiency prediction, the system can issue alerts and can decide whether or not to enter normal operation.