Investigation and Design of Coupler Structure in Capacitive Wireless Power Transfer with Free-Positioning Feature

This paper investigate a capacitive coupler, which is proposed to achieve the free-positioning feature in capacitive wireless power transfer system. Firstly, the proposed capacitive coupler is analyzed and designed with the FEM simulation. The simulation results indicate that the capacitance could keep almost constant regardless the misalignment between the transmitter and receiver; The parameters of the coupler are optimized to improve the system's performance. Finally, a capacitive coupler was made by PCB and a 6.78-MHz 5-W prototype with a series-series compensation network was built to validate the theory and idea in this paper. The variation of the input and output capacitance is within 0.3% and 1.5%, respectively. And the experimental results indicate that the free-positioning characteristic was accomplished, the output maintain about 5V/1A regardless the position of the receiver.