Self-Synchronized Class e Resonant Rectifier with Direct Voltage Detection Method

This paper presents a high-frequency self-synchronized class E resonant rectifier for a wireless power transfer (WPT) system using a direct voltage detection method. Synchronous rectification increases the efficiency of the WPT system by replacing diodes into switching devices such as MOSFETs. However, in the high-frequency, mid-range WPT system, it is challenging to carry the gate signal from the transmitting side to the synchronous rectifier. In order to overcome this issue, we propose the self-synchronized rectifier without the gate signal from the inverter. The direct voltage detection method synchronizes the gate signal by sensing the input voltage of the L-C resonant filter. Even though a gate driver and a comparator have a 10 ns total propagation delay, the leading phase of the sensing voltage offsets the driver's propagation delay. In the experiments, the proposed rectifier was connected to a class E resonant inverter operating at 13.56 MHz. At an output power of 244 W and a frequency of 13.56 MHz, the total power conversion efficiency of the DC-DC converter is 88.59%.