Constant Current and Constant Voltage Charging of Wireless Power Transfer System Based on Three-Coil Structure

Constant current (CC) and constant voltage (CV) charging are two charging stages for li-ion batteries in an electric vehicle wireless charging system. Based on the three-coil structure, this letter proposes a novel reconfigurable topology to achieve CC and CV charging. The transmitting coil is split into two windings with one winding having a turn number much smaller than the other. The two windings are fully compensated and connected to the corresponding inverter phase. The system can be reconfigured to perform as the two-coil structure with a CC output or as the three-coil structure with CV output. Unlike existing methods, the working frequency is fixed and only one relay is utilized to achieve the shift of CC and CV charging, which has the advantages of simpleness and low cost. An experimental prototype with 94.4% maximum efficiency is implemented to validate the proposal.