Analysis and Design of 10-MHz Capacitive Power Transfer With Multiple Independent Outputs for Low-Power Portable Devices

This article proposes a multiple-output capacitive power transfer (CPT) system using the LCCL compensation network for low-power (<20 W) battery charging application, e.g., consumer electronics. For CPT, reliable operation is still a challenge under a wide range of receiver configurations due to the variations in receiver position or load impedance. In this article, employing the constant-voltage property of the LCCL network, the proposed multiple-output CPT system is able to achieve output independence among different receivers. Moreover, based on the first-harmonic approximation (FHA), a design method is proposed and studied in depth to maintain minimal current stress on power devices and inductors, as well as zero-voltage switching (ZVS) within a defined range. The proposed method considers the impact of component value ratios to limit the resonant current magnitude and determine the phase angle and selects inductance values for the most efficient system operation. Finally, a constructed 10-MHz experimental prototype achieves CPT from one transmitter to three independent S-W receivers, with plate voltages less than 55 V. The measured power efficiency of the prototype is up to 83.6% at the 15-W output.