A High Switching Frequency Flyback Converter in Quasi Resonant Mode

The demand for micro-scaling of power systems has boosted the research on high-switching-frequency power converters. A flyback converter operating in resonant mode featuring low switching losses, low transformer losses, and reduced switching noise at higher switching frequencies are investigated in this article as an alternative to the conventional quasi-state resonance based flyback topology to improve power density. In order to get a compromise between the magnet size, electromagnetic interference (EMI), and efficiency the proposed methodology implements a resonant system between transformer and leakage inductance with a snubber capacitor in order to obtain a zero-voltage switching at turn-on and turn-off of the primary switch with reduced core loss due to a continuous magnetizing current to the transformer and also a lower EMI due to low di/dt and dv/dt ranges. Meanwhile, the concept uses the regenerative snubber to recycle the transformer leakage power consisting of two snubber diodes and a snubber capacitor. The proposed methodology has been verified on a 340 kHz 65W prototype design. Compared with the conventional quasi-resonant flyback converter that is operating at the same switching frequency, the proposed concept has 2% efficiency improvement and better EMI performance.