Wide-Range Input-Isolated DC–DC Ultrahigh-Step-Down Converter Containing Buck and Half-Bridge Topologies for Low-Power Applications

This paper proposes an ultrahigh-step-down converter with a high voltage conversion ratio. The primary side of the proposed converter contains a half-bridge converter with a conventional buck converter. This design effectively reduces the voltage stress on the input-side diode and main switch while also recovering leakage inductance energy. The secondary side has a current-doubling rectification architecture, which enables zero-voltage switching and zero-current switching, thereby minimizing switching losses on the secondary-side switches and consequently improving overall efficiency. A 150-W prototype was implemented under an input voltage range of 140 to 170 V and an output voltage of 3.3 V. The efficiency and feasibility of the proposed converter were confirmed through steady-state analyses and a hardware implementation. In experiments, the peak efficiency of the prototype was 93.4% at an input of 140 V and 92.5% at an input of 170 V.