Hybrid PFM and PWM Modulation Scheme for Series Resonant Bidirectional DC/DC Converter

Resonant bidirectional DC/DC converter is achieving more and more attention due to excellent performance of high efficiency and power density. However, it is difficult to maintain these features under a wide gain range. A hybrid PFM and PWM modulation scheme for series resonant bidirectional DC/DC converter is proposed in this paper. The switching time of upper switches is controlled to realize soft switching, while the conduction period of lower switches is controlled to regulate the delivered power. Almost all the switches realize soft switching and all the instantaneous power generated by each full bridge is positive achieving resulting in low RMS resonant current. Thus, high power efficiency can be achieved even under a wide gain range. The modulation scheme is theoretically analyzed and experimentally validated in a 1kW prototype.