Design and Analysis of GaN Based Isolated Double-Step-Down Converter for High-Step-Down Application

This paper presents a new isolated topology for high-step-down applications. The proposed converter derives from DSD (double-step-down) converter employing one flying capacitor as energy bus and dual-inductor output stage. Unlike other PWM isolated DC-DC topologies, the new design achieves exceptionally high component utilization and features a simplified structure, resulting in reduced voltage and current stress on switches and negative components. These benefits contribute to lower costs, decreased conduction losses, and enhanced reliability of power systems, particularly in applications with high conversion ratios. By appropriately adjusting the dead time, the switches on the secondary side can operate in zero-voltage-switching (ZVS) soft-switching mode. After optimization of the switching scheme and analysis of non-ideal effects, simulation validation is performed. To demonstrate the practical applicability of the new topology in high step-down applications, a 100KHz prototype featuring 60V/48V-to-1V transfer with up to 70A output current is built up with 92.6% peak efficiency.