A Study on ZCS Problem Due to Phase Change in Inductive Power Transfer Charging System Applying GaN FET

In this paper, we analyze the problem that occurs when the Zero Voltage Switching (ZVS) is changed to Zero Current Switching (ZCS) in a wireless power transfer system where the position of the receiving coil changes frequently. Based on this analysis, the problem caused by the ZVS to ZCS transition is demonstrated by a detailed theoretical analysis that can be solved by using a GaN FET with wide bandgap characteristics instead of the conventional MOSFET. To verify the theory, a 500W IPT prototype with SP compensation circuitry was built. And compare the operation of ZVS and ZCS when MOSFET and GaN FET are applied. In addition, if the GaN FET is applied to the field where the resonance frequency can be changed in the wireless power transfer system, the possibility of solving the problem in the ZCS operation can be confirmed.