A Novel Efficiency-oriented Frequency Tracking Method for WPT Systems

The deviation from resonant conditions in wireless power transfer (WPT) systems caused by variations of compensation parameters will result in reduced power transfer efficiency and deteriorated output characteristics. To handle with these problems, the time difference between the rising edge of the driving signal and the zero-crossing point of the primary current is detected. The phase angle of the input impedance is obtained, which works as the feedback parameter to control the switching frequency of the inverter. The proposed WPT systems always operate under resonant conditions. Hence, the output power and efficiency are improved, and zero-voltage switching is achieved under all load conditions.