Design of an Inductive Power Transfer System with Constant Current and Constant Voltage Outputs Based on Multi-frequency Circuit

Inductive power transfer (IPT) systems have been widely employed in the application of battery charging. The charging process usually requires constant current (CC) stage and constant voltage (CV) stage to extend the lifetime of the battery. This paper proposes an IPT system with CC and CV output characteristics based on multi-frequency circuit. The fundamental and the third harmonic components of the input voltage in the resonant circuit are used in CC and CV modes, respectively. The equivalent compensation circuit is S-S in CC mode and S-LCC in CV mode. One ac switch (ACS) is used at the primary side. Slightly changing the operating frequency is applied to realize CC and CV charging accurately. Finally, a 520W prototype is built to verify the proposed method. The experimental results show that the proposed IPT system can achieve the target CC and CV charging profile with the operating frequency ranging from 67–70 kHz.