Optimal Design of Planar Magnetic Components for a Two-Stage GaN-Based DC–DC Converter

This paper develops a 200-W wide-input-range (64-160-to-24-V) rail grade dc-dc converter based on gallium nitride devices. A two-stage configuration is proposed. The first regulated stage is a two-phase interleaved buck converter (>400 kHz), and the second unregulated stage is an LLC (2-MHz) dc transformer. In order to achieve high frequency and high efficiency, the critical-mode operation is applied for the buck converter, and the negative coupled inductors are used to reduce the frequency and the conduction losses. Then, a systematical methodology is proposed to optimize the planar-coupled inductors. For the unregulated LLC converter, it can always work at its most efficient point, and an analytical model is used to optimize the planar transformer. Finally, the proposed dc-dc converter, built in a quarter brick form factor, is demonstrated with a peak efficiency of 95.8% and a power density of 195 W/in
³
.