A High-Voltage ZVZCS DC--DC Converter With Low Voltage Stress

A high-voltage zero-voltage-zero-current-switched dc--dc converter with low voltage stress is presented in this paper. Its circuit structure is extended from a previously developed zero-voltage-switched dc--dc converter consisting of six series-connected switching devices, one three-phase transformer, and an output current tripler. The voltage stress on each switching device is only one-third of the input voltage. Compared with the previous converter, apart from retaining the advantage of having low voltage stresses on the switches, the main advancements of the proposed converter have also included (1) wider soft-switching range; (2) elimination of circulating energy on the primary side during the freewheeling stage; and 3) use of phase-shift pulsewidth modulation in output voltage control. Detailed topological operations and steady-state characteristics of the converter will be given. A 2.2-kW, 990-V/110-V dc--dc converter prototype has been built and tested. Experimental results are favorably compared with the theoretical predictions.