An asymmetric PWM for low switching frequency power factor correction circuit

In order to improve the efficiency of the conventional home appliances, brushless DC motors with variable speed controller have been extensively applied to various home appliances, such as air-conditioners, refrigerators, washing machines, etc. However, existing literatures concerning power factor correction (PFC) for home appliances are limited. In this paper, a practical approach is proposed to deal with problems such as harmonic distortion and poor power factor so that the great demand of PFC in variable speed home appliances can be satisfied. A high power factor and low current harmonic distortion PFC circuit is developed based on the idea of low switching frequency asymmetric pulse width modulation (Asy-PWM). Compared with the well-known high frequency active PFC circuits, high switching loss and heavy EMI filters can be eliminated. Theoretical analysis, computer simulation, and experimental results all have demonstrated the effectiveness of the proposed method.