ABSTRACT
Conventional boost converters are usually adopted as a PFC stage. Especially, a boost converter in discontinuous-conduction-mode (DCM) and its modified topologies are widely used because high power factor can be achieved without complex control scheme. However, the output voltage of the DCM boost converter stage should be much larger than the peak value of the input voltage in order to obtain high power factor. Similarly, buck converters can be used as a PFC stage. Its output voltage is lower than the peak value of the input voltage. However, its input current has dead angles. Also, a SEPIC converter is adopted for PFC applications [1]–[5]. Since it has a step up/down capability, the output voltage can be lower than the peak value of the input voltage. All of these PFC circuits have a full-bridge diode. Therefore, conduction losses caused by this full-bridge diode lower down power conversion efficiency especially at low ac line. In order to overcome these problems, a PFC converter based on SEPIC topology is proposed in this paper. The circuit diagram of the proposed PFC converter is shown in Fig. 1. Since there is no bridge diode, the conduction loss can be reduced and the efficiency can be raised.
