A Novel Series Capacitor Isolated DC–DC Converter With Reduced Voltage Stress of Primary Switches, Full-Range ZVS Operation, and Improved Light-Load Efficiency

To target the 80 Plus 380 Vdc Titanium specifications, this article proposed a novel fixed-frequency isolated dc–dc converter with full-range zero voltage switching (ZVS). Different from the conventional phase-shift full-bridge (PSFB) converter, the series capacitor structure and series-connected two transformers are incorporated in the proposed converter to achieve full-range ZVS operation and light-load efficiency improvement. First, the voltage stress of three primary switches is reduced to half of the input voltage because of the special series capacitor structure. Correspondingly, the energy needed for obtaining the ZVS operation of all primary-side switches is reduced by one-fourth of conventional methods. Furthermore, the employed series-connected two transformers not only achieve the full-range ZVS operation but also eliminate an output inductor presented in conventional PSFB converters. Therefore, higher efficiency can be achieved. In conclusion, low voltage stress, full-range ZVS operation, and fixed switching frequency are the main advantages of the proposed converter. A 360–440 V, 12 V/50 A prototype is built to verify the claimed features of the proposed converter. Experimental waveforms show the ZVS operation under the entire range. The measured efficiency is higher than 95% from 14 A load up to full load, and the peak efficiency of 96.7% can be achieved for 360 V at 25 A load.