Proposal for the Optimum Switching Frequency Search Method Based on Transmission Side Information of Wireless Power Transfer Circuit

Wireless power transfer could increase the convenience and operating rates of battery-equipped electrical equipment. Since the positional relationship between the transmitter and receiver coils is not fixed, selecting an optimal operating frequency for each positional relationship is necessary to maximize power conversion efficiency. This paper focuses on the search method for an optimal operating frequency for a wireless power transfer circuit. We propose a search method for a frequency that maximizes the input power factor and transmission efficiency without using radio communication between the power transmitter and receiver. The circuit examined is a combined resonance circuit in which both the power transmission side and the reception side are series resonance, and its operating frequency range is 79–90 kHz. It is clarified that the optimal operating frequency can be found by detecting the input current of the circuit on the transmission side without radio communication between the power transmitter and receiver.