Design and Comparison of Power Combining Architectures for Capacitive Wireless Power Transfer Systems

Abstract

State-of-the-art high-frequency capacitive wireless power transfer (WPT) systems are limited in their power transfer capability due to the limited power rating of the current wide-bandgap semiconductor devices used in their inverters. This paper presents several passive power-combining architectures to operate multiple inverters in parallel in high-power high-frequency capacitive WPT systems. A comprehensive methodology to design each of these power combining architectures with an objective to ensure balanced current sharing and minimal circulating currents between the paralleled inverters is presented. A novel circuit technique to maximize the power processing capability of each inverter module while ensuring complete soft-switching of the inverter transistors is also presented. Furthermore, a comparative study of these power combining architectures is performed to investigate their effectiveness in mitigating the timing and component tolerance related mismatches between paralleled inverters. Finally, the outcomes of this analysis are experimentally validated using a 6.78-MHz, 12-cm air-gap prototype capacitive WPT system implemented using two paralleled inverters which is tested upto 2.3 kW. The experimental results are in good agreement with theoretical predictions.