A Dual-Transformer-Based Three-Level DC-DC Converter With Wide ZVZCS Switching Range

In this letter, a dual-transformer-based three-level DC-DC converter (TLDC) with wide zero-voltage and zero-current switching (ZVZCS) switching range is proposed. Compared with traditional ZVZCS TLDCs, this converter can achieve zero-voltage switching (ZVS) for the leading switches and zero-current switching (ZCS) for the lagging switches without any extra auxiliary components. By introducing an additional transformer, the energy can be transmitted during the whole switching period, and the current ripple of the output filter inductor can be reduced, resulting in a reduction in output filter inductance. Besides, the control strategy is a traditional simple phase-shift control. The circuit, operation principle and some steady-state characteristics are discussed in this letter. Finally, a 1-kW 650-800 V input and 250 V output experimental prototype is designed to demonstrate the validity and features of the proposed converter.