Soft and Hard-Switched Synchronous Buck Converter Comparison for USB Power Delivery

The widespread adoption of USB Power Delivery (PD) has revolutionized portable electronics charging, offering fast, efficient, and flexible power transfer solutions. Hard-switched synchronous buck converters (SBC) are widely used for this application. But this topology suffers from high switching losses. Zero voltage switching synchronous buck converter (ZVS SBC) mitigates these issues and could potentially serve as an alternative solution for USB PD application. This paper presents a comparative loss analysis of ZVS SBC against the traditional SBC in the context based on GaN semiconductor switches. The variation in switching, conduction, and core losses with varying input voltage and load conditions are highlighted. The impacts of fixed, variable, and step -varied frequency modulation techniques on power losses of ZVS SBC are analyzed. Experiments are carried out to evaluate the performance of ZVS SBC with different modulation techniques and corresponding power loss breakdowns are presented.