Design considerations for high frequency DCM flyback converter

This paper presents design considerations for a high frequency (≥1 MHz) Discontinuous Conduction Mode (DCM) flyback converter. As switching frequency increases, the problems such as switching loss and undesirable effects due to the parasitic capacitance of switching device are exacerbated. Considering these issues, design instructions are proposed about DC link capacitance, PCB transformer, snubber, magnetizing inductance, switch, output capacitance and turn ratio. Following the instructions, 1-MHz 65-W flyback converter was implemented. Its output voltage was regulated to 19 V in DC 100-373 V input voltage. The experimental results and loss breakdown analysis are given. To observe the effect of variation in switching device capacitance, Si and SiC MOSFET switches are tested. The switching waveforms and the efficiency of the two cases are compared.