A Two-Stage GaN-Based ZVS DC-DC Converter with Wide Input Voltage Range

This paper presents a high-frequency, zero-voltage-switching (ZVS) isolated DC-DC converter for applications requiring high efficiency, high power density, and a wide voltage range. The first regulated stage is a four-switch buck-boost (FSBB) converter that uses quadrangle current modulation for the inductor current. Constraints on the control variables are derived, and a quantitative relationship between the RMS value of inductor current and the control variables is established through mathematical calculations. Then a simplified, single-variable, closed-loop control system is proposed to achieve ZVS of all switching and minimum inductor current RMS. The second stage is an LLC DC transformer (DCX) that uses a matrix transformer and flux cancellation to reduce core size and loss. Finally, a 500-W prototype was built to verify performance, achieving a peak efficiency of 95.4% and a power density of 110 W/in³.