ZVS Analysis of Half Bridge LLC-DCX Converter Considering the Influence of Resonant Parameters and Loads

Using LLC converter as a DC-DC transformer (LLC-DCX), which operates near the resonant frequency, is a suitable solution to achieve maximum conversion efficiency. This paper presents ZVS analysis of a half bridge LLC converter used as a dc-dc transformer (DCX) under "Synchronous turn-on and Synchronous turn-off" modulation strategy, with consideration of resonant parameters and loads. By analyzing the major operation modes and establishing time-domain model, ZVS conditions are obtained, which reveal that ZVS is not only related to the magnetizing inductance as in previous studies, but also related to the loads and resonant parameters. The related parameters including the magnetizing inductance and dead time range to achieve full load ZVS for both primary-side and secondary-side switches are analyzed. The simulation and experimental results verify the correctness of theoretical analysis.