Characteristics Analysis and Design of a Resonant dc–dc Converter With ZCS and Short-Circuit Fault Current Limiting Capability

The series-resonant dc–dc converter (SRC) which features zero current switching (ZCS) and open-loop control is widely used for providing galvanic isolation and voltage scaling. However, output short-circuit (OSC) fault is a challenge for SRC because it will cause dramatically high current in the low-impedance resonant tank. To address this issue, a resonant full-bridge dc–dc converter only using small dc-side capacitors to resonate with the resonant inductor
$L_{r}$
is proposed. Under normal condition, ZCS can be achieved. When OSC fault occurs, the output dc-side capacitor can be bypassed by the antiparalleled diodes of the full bridge and the resonant current can be limited automatically by the resonant inductor
$L_{r}$
without additional control. The operation principle of the converter under normal and faulty condition is analyzed. Based on these analyses, the switching frequency to achieve ZCS is designed. The resonant inductor
$L_{r}$
and dc-side resonant capacitors
$C_{r}$
design considerations are provided. The ZCS characteristics and the current limiting capability of the converter are verified on an experimental prototype.