Adequate Usage Rate Control of Switching Cycles for DCM Buck PFC Converter

Buck power factor correction converter is widely used in low-power applications due to its specific advantages. In discontinuous conduction mode operation, the inductor current is zero during part of the switching cycle, leading to a useless period in the whole switching cycle of the power transmission. As a result, the peak value and the root-mean-square (RMS) value of the inductor current as well as the switch current are large. In addition, the current stress of the power devices is high, and so does the switching loss. A new method called adequate usage rate control of switching cycles to improve the effect of the energy transfer is proposed. Compared with the fixed duty ratio control, the critical inductance is increased, and the peak and rms current values of the main power components are reduced. Therefore, the efficiency of the converter is increased. The method brings about higher PF at low input voltages and lower PF at high input voltages. Meanwhile, a reduction of the output ripple voltage is achieved. A prototype is fabricated in the laboratory, and the experimental results are presented to verify the effectiveness of the proposed method.