A novel hybrid compensation circuit for wirelessly charging electric vehicles

In order to stabilize the output current and voltage of wirelessly charging circuit for electric vehicles, a hybrid compensation circuit (CL-LC/LCL) with less additional switches capable of achieving the transition from constant current to constant voltage is proposed. This novel hybrid compensation circuit can realize not only stable output current and voltage independent of load variations, but also achieve resistive input impedance. Firstly, the conditions for realizing constant output current or voltage are analyzed based on the mutual inductance model. Meanwhile, the input impedance is also mathematically deduced. Then, the energy transfer efficiency is theoretically deduced and the relationships between the transfer efficiency in terms of inductive coupling coefficient and load resistance are analyzed. In addition, the circuit characteristics in terms of loads are studied and the allowable range of connected load is given in order to maintain the constancy of output current or voltage. The experimental results show good agreement with the theoretical analysis.