Research Specifications

t This paper proposes a new isolated high step-down dc-dc converter with a more extensive output range and high efficiency. The interleaved output and ZVS-ZCS switching for all semiconductors have made the converter appropriate for high output current applications. An auxiliary inductor is used to achieve the ZVS (zero-voltage switching) and ZVZCS (zero-voltage zero-current switching) condition, which charges and discharges the parallel snubber capacitors of the power switches at different modes of operation. Therefore, the switching losses of semiconductor components are reduced significantly, which results in enhanced efficiency. Moreover, the connection of an auxiliary capacitor in series with the transformer has prevented the probability of DC-current saturation. The proposed converter could be controlled with duty-cycle or switching frequency variations. However, the output voltage control with the switching frequency variations gives an extended range of output voltage compared with the other presented converters. Moreover, a coupled inductor is used to relate the output gain with the turn ratios, which causes a more extensive range for output voltage gain. Finally, the theoretical analysis is given and is compared with a 140 W experimental prototype, which converts a higher input voltage 300v to 7.5 V of the output voltage