A 6.78 MHz Class-E Amplifier Based Capacitive Power Transfer System with Approximate Constant Current Output Characteristic

Increasing the operating frequency of capacitive power transfer (CPT) systems is conducive to reducing the system volume and the port voltage of the coupler. Class-E power amplifier (PA) is a typical circuit suitable for high-frequency inverter because of fewer components and higher reliability. However, Class-E amplifier is extremely sensitive to the load, and changes in load may cause the Class-E amplifier to lose its zero-voltage switching (ZVS) operation and withstand a current spike. In this paper, a 6.78 MHz Class-E amplifier based capacitive power transfer (CPT) system with approximate constant current (ACC) output characteristic is proposed. The model of the capacitive coupler is established and a series-parallel (SP) compensation network is selected. The influence of load resistance variation on the system operation is analyzed, and the ACC output and wide-range ZVS characteristics of the system is proved. A 145 W prototype is built and the experimental results verified the theoretical analysis.