Optimal Control Scheme for Single-Stage Dual-Active-Bridge AC-DC Converter

This paper proposes an optimal control for a high step-down ratio single-stage AC-DC converter based on dual-active-bridge (DAB) topology and enhancement mode GaN FET. AC bridge working principle and clamping capacitor operation strategies is introduced. Zero voltage switching (ZVS) condition is analyzed to improve efficiency during whole line period. Optimal control for maximum turn-off current optimization in both variable frequency and fixed frequency condition is explored to reduce switching loss for low voltage DC side transistors. A 240VRMS AC-48V DC, 80-250 k Hz prototype was developed to verify the novel converter.