Compensation Circuit for Capacitive Power Transfer System to Realize Desirable Constant Voltage or Constant Current Output

Abstract

Since lithium-ion batteries have been used in many energy storage applications, a well compensated capacitive power transfer (CPT) system should provide the load with an efficient charging profile consisting of constant current (CC) and constant voltage (CV), while maintaining nearly unity power factor and soft switching of power switches simultaneously. However, most CPT chargers can only realize CC output or CV output with the input zero phase angle (ZPA). Thus, this paper proposes a compensation circuit for CPT system to realize the transition from CC mode to CV mode by simply switching the operating frequency. After a systematic analysis, one CV frequency and two CC frequencies with input ZPA are derived. Without reactive power in the circuit, a parameter design method is proposed for the proposed CPT system to satisfy the load-required CC or CV output and input ZPA. Finally, an CPT prototype with 2 A charging current and 48 V battery voltage is built to verify the analysis and the CPT prototype performs well within a small X-axis and Y-axis misalignment,