High-efficiency series-parallel resonant converter for the non-contact power supply

Comparing with the conventional transformer without the air gap, a non-contact transformer with a large air gap between the long primary winding and the secondary winding has increased leakage inductance and reduced magnetizing inductance. For transferring the primary power to the secondary one, the high frequency series resonant converter has been widely used for the non-contact power supply system with the increased leakage inductance of a non-contact transformer due to the large air gap. However, the high frequency series resonant converter has the disadvantages of the low efficiency and the high voltage gain characteristics in the overall load range due to the large air gap and the high circulating magnetizing current. In this paper, the characteristics of the high efficiency and unit voltage gain are revealed in the proposed three-level series-parallel resonant converter. The results are verified on the simulation based on the theoretical analysis and the 5 kW experimental prototype.