Power Factor Improvement of Flyback PFC Converter Operating at the Light Load

We propose a duty-ratio feed-forward controller for flyback power factor correction (PFC) converters operating in discontinuous conduction mode (DCM). For PFC applications, the power factor (PF) of the input current must be high under most load conditions. To improve PF of the flyback converter even under light load, we propose a compensation method for input capacitor current. The proposed controller significantly improves the displacement factor as well as the distortion factor, and therefore fly-back PFC converter can achieve the high power quality. Meanwhile, the output voltage of the PFC converter is well regulated. The derivation of the proposed method is presented and effectiveness of the proposed method is demonstrated in experiments with a 100-W rated power prototype.