An Interleaved Nonisolated ZVS Ultrahigh Step-Down DC–DC Converter With Low Voltage Stress

This paper presents a nonisolated ultrahigh step-down dc–dc converter for low-voltage high-current applications. The converter provides extended duty cycle for all power switches while low voltage and current stresses are imposed on semiconductor devices that cause low conduction losses and low output current ripple. In addition, soft-switching condition is achieved for all semiconductor devices without adding any active element. To achieve the improved voltage conversion ratio, a pair of coupled inductors and series capacitors is used in the interleaved step-down structure. The two auxiliary inductors provide zero-voltage zero-current switching turn on for all switches and zero-current switching turn on and turn off for all diodes. Thus, the losses associated with semiconductor components are reduced impressively and the overall efficiency of the proposed converter is improved considerably. The accuracy of the converter operation is confirmed by a 450-W laboratory prototype operating at 400-V input, 12-V output, and 100 kHz switching frequency.