Abstract: At certain duty cycle, a novel DC-DC converter with larger step-down ratio and low voltage stress of switching devices is studied. The proposed converter consists of a low-side switch type step-down unit cascading with switched inductor step-down unit. Topologically, the low-side switch type step-down unit is equivalent to Buck converter with main switch located on low side. As for the switched inductor step-down unit, it is organized as X-shape connection by two diodes and two inductors. Thanks to stacking two sets of low-side switch type units and configuring two main control switches in the circuit, voltage stress of switching devices are dramatically reduced. Based on the analysis of operation modes and steady-state performance of the converter, SIMPLIS is used to do simulation in order to verify theoretical analysis. A 500 W hardware prototype with 94.1% peak efficiency is built and tested with results demonstrating that the proposed buck converter features large step-down ratio, low voltage stress of switching devices, continuous input current.