A ZVS APWM Half-Bridge Parallel Resonant DC–DC Converter With Capacitive Output.

In this paper, a modified asymmetric half-bridge (AHB) isolated converter is proposed, which does not have dc current offset in the transformer. The topology operates in the same way as the conventional half-bridge (HB), using asymmetric pulsewidth modulation with constant frequency. A voltage doubler rectifier is used in the output stage, which avoids the flow of the dc component current in the primary side of the transformer. In order to investigate the application of the proposed topology, a parallel-resonant (PR) version of the modified AHB was tested, which uses the parasitic elements of the transformer, such as the leakage inductance and the winding capacitance, to achieve zero voltage switching in the primary side switches over a wide load range. Theoretical and commutation analysis results are reported and design guidelines are presented herein. Experimental data were obtained from a parallel resonant 1-kW prototype, operating with a 50 kHz switching frequency, 400 V input voltage, and 400 V output voltage, to verify the theoretical study, and 97% efficiency was achieved. The proposed solution was also tested at high voltage, operating with a rated power of 1.8 kW, switching frequency of 50 kHz, input voltage of 400 V and series-connected output voltages, the maximum voltage being 8620 V. [ABSTRACT FROM AUTHOR]