DCM Flyback PFC converter with optimum utilization control of switching cycles

The discontinuous current mode (DCM) flyback power factor correction (PFC) converter features zero-current turn-on for the switch, no reverse recovery in the secondary diode and constant frequency operation. However, due to DCM, the energy transfer does not cover the whole switching cycle, the peak and RMS values of the inductor current are large, which also occurs to the switch and diode. This increases not only the current stress of the power components but also the conduction and switching turn-off loss, which lowers the efficiency of the converter. An optimum utilization control of switching cycles (OUCSC) is proposed in this paper. The efficiency is improved as the critical inductance is increased and the peak and RMS current values are therefore decreased. The proposed method also achieves an output voltage ripple or an output storage capacitance reduction. The simulation results show the effectiveness of the method.