An Overview and Comprehensive Comparative Evaluation of Constant-Frequency Voltage Buck Control Methods for Series Resonant DC-DC Converters

The paper focuses on galvanically isolated series-resonant dc-dc converters with a low quality factor of a magnetically integrated resonant tank. These converters can be controlled at a constant switching frequency to achieve the input voltage buck regulation. The paper compares various buck control methods, such as conventional pulse-width modulation, hybrid pulse-width modulation, shifted pulse-width modulation, hybrid shifted pulse-width modulation, improved shifted pulse-width modulation, asymmetrical pulse-width modulation, pulse-width modulation, and hybrid pulse-width modulation applied to the series-resonant dc-dc converter. The study considers step-up implementation of the series-resonant dc-dc converter topology with the voltage doubler rectifier, which makes it suitable as a front-end dc-dc converter for the integration of renewable energy sources in dc microgrids. The voltage buck control methods considered were compared analytically in terms of the cumulative power losses calculated theoretically. The theoretical results were compared with the experimental measurements to confirm the calculations and benchmark the voltage buck control methods. The experimental validation was performed using a 250 W prototype that demonstrated the hybrid PSM achieves the best performance. The experimental results were found in good agreement with analytically predicted values of the power loss.