Analysis of a wide load variation of ZVZCS phase-shifted PWM full-bridge DC-DC converter

This paper presents a wide load variation of the improved ZVZCS phase-shifted PWM full-bridge dc-dc converter, which can deliver power efficiently. The key operation waveforms of the full-bridge converter from absolutely no-load to full-load conditions are described. In order to confirm wide load variations, the converter should not only operate with soft-switching from full load to no-load condition with satisfactory efficiency for the full range of operation, but the voltage across the output diode bridge also needs to be clamped to keep away from any reverse voltage overshoots arising during turn-off of the output rectifying diodes. In order to achieve zero-voltage switching (ZVS) at turn-on for all load conditions, the converter employs auxiliary coupled inductors near lossless auxiliary circuit. Moreover, the proposed topology is based on a current driven rectifier in order to clamp the voltage of the output rectifying diodes and also obtain ZVZCS of the converter operation, resulting in superior efficiency for all load conditions. In this paper, the converter operation is described. Experimental results provided from a 1 kW prototype validate the feasibility.