Design Methodology of Quasi-Resonant Flyback Converter with a Divided Resonant Capacitor

Abstract

The leakage inductance in flyback converters can induce high-voltage spikes in power switches as well as power losses. Although conventional resistor-capacitor-diode (RCD) snubbers and active clamp circuits can be used to suppress these voltage spikes, the clamping operation of RCD snubbers increases power consumption, while the active clamps require additional power switches. To address these issues, a quasi-resonant flyback converter featuring a divided resonant capacitor is proposed in this article, in order to suppress voltage spikes in power switches and improve the power conversion efficiency. The operational principle of a divided resonant capacitor is analyzed to obtain the design methodology of the divided resonant capacitor. Furthermore, the validity of the proposed design method is verified via experiments, using 15-W prototype quasi-resonant flyback converter. The results indicate that the proposed design effectively reduces voltage spikes and improves power conversion efficiency.