Hybrid full‐bridge and LLC converter with wide ZVS range and less output inductance

Abstract

This study presents a new hybrid full-bridge and LLC converter with the features of low circulating current loss, wide zero voltage switching range and less output inductance for industry power units. The proposed hybrid circuit has two full-bridge converters and one LLC converter with shared lagging-leg switches. Two full-bridge converters, shared the same lagging-leg switches, are operated at phase-shift pulse-width modulation to regulate the output voltage and share the load power. Half-bridge LLC converter is added at the lagging-leg switches to extend the zero voltage switching range of lagging-leg switches from zero to full load. The output voltage of LLC converter is connected to the secondary sides of two full-bridge converters during the freewheeling interval to eliminate the circulating current loss. The rectified voltage of full-bridge converter during the freewheeling stage is positive instead of zero so that the output filter inductance can be reduced. Finally, experiments with a 1440 W prototype circuit converting 380 V input to an output voltage 24 V/60 A are provided to verify the theoretical analysis and effectiveness of the proposed converter.