A Nonisolated High Step-Down DC–DC Converter With Low Voltage Stress and Zero Voltage Switching

This article introduces a general method to modify the traditional buck converter to become a high step-down dc–dc converter, which has a lower voltage gain without changing the voltage stress of switches. From the analysis, an auxiliary circuit is proposed to implement this method. In addition, triangular conduction mode operation is also analyzed to derive zero-voltage switching (ZVS) model of the modified buck converter, which is beneficial for high-frequency applications. Coupled inductor, which is established from two inductors of auxiliary circuit and buck converter, is employed to improve both steady-state and dynamic response performances. By analyzing the influence of coupling coefficient, and the rate between two inductances into inductor current ripple, transient response, and ZVS model, a suitable coupling structure is recommended to employ in the proposed converter. As a result, the design considerations are presented to get the maximum benefits of coupled inductor for this proposed converter. Finally, a prototype of 48 W is built and tested to verify its feasibility.