A Double-Sided LC-Compensation Circuit for Loosely Coupled Capacitive Power Transfer

This paper proposes a double-sided LC-compensation circuit for a loosely coupled, long-distance capacitive power transfer (CPT) system. A CPT system usually contains two pairs of metal plates as the capacitive coupler. An LC-compensation circuit resonates with the coupler to generate high voltages, and corresponding electric fields, to transfer power. When the compensation circuit is used on both the primary and secondary sides, it results in a double-sided LC-compensated CPT system. The working principle and frequency properties of the CPT system are analyzed. The results show a similarity with the series-series-compensated inductive power transfer system, which has both constant-voltage (CV) and constant-current (CC) working modes. LC-compensation is also compared with LCLC -compensation in terms of power, frequency properties, and output efficiency. A 150-W double-sided LC -compensated CPT prototype is designed and implemented to demonstrate a loosely coupled CPT system with 2.16% coupling coefficient. For both CC and CV working modes, the experimental results achieve dc-dc efficiencies higher than 70% across an air-gap distance of 180 mm with a switching frequency of 1.5 MHz.