Abstract

This paper presents a comparative study of modulation strategies for a full-bridge based unidirectional step-down partial power converter (PPC), focusing on a newly proposed Buck Modulation (BM) scheme. Unlike traditional Phase-Shift Modulation (PSM), BM disables transformer utilization by applying identical PWM signals to all switches in the converter's full-bridge, effectively converting the topology into an equivalent buck converter. Thermal simulations were conducted to evaluate efficiency performance across different transformer turns ratios and load conditions. Results demonstrate that BM achieves superior efficiency at light loads when the transformer ratio is below unity, and consistently outperforms PSM across the entire power range when the ratio exceeds unity. Furthermore, BM offers a wider and more flexible operating voltage range. © 2025 IEEE.