Three level DC-DC converter based on cascaded dual half-bridge converter for circulating loss reduction

An improved two-half-bridge cascaded three-level (TL) DC-DC converter with reduced circulating current is proposed in this paper. The converter contains two transformers but without clamping diodes or flying capacitors. The rectifier stage is composed of four diodes and four windings of the two transformers. Because of the proper sequence of the windings, the circulating currents on the primary side of the transformers decay to zero during the freewheeling period. Although the circulating current is reduced, the primary switches still achieve zero voltage switching (ZVS). Furthermore, the proposed converter can reduce the current ripple of the filter inductor, leading to a reduction in output filter inductance. Due to the advantages mentioned above, the proposed converter can meet the high efficiency, low size, and light weight requirements. Lastly, a 1kW prototype is built to verify the performance of the proposed converter.