Design of a Half-Bridge Converter for Self-Adapting Capacitive Wireless Power Transfer

Abstract

We present the design of a half-bridge converter for a capacitively coupled wireless power transfer system. The load signal acts as a positive feedback signal for a self-oscillation circuit which generates the driving gate signals for the converter. Our research reveals a robust wireless operation for a large range of load resistors and coupling capacitors. Based on an electric network analysis we obtain design criteria for self-oscillation and for the power transfer. The theoretical predictions are confirmed by circuit simulation and measurement results on a converter prototype with GaN-HEMTs. We report on a transfer efficiency of 92% for a power greater than 50W at a switching frequency of 300kHz and 200V DC link voltage.