Power Factor Correction With a Modified Sheppard–Taylor Topology Operating in Discontinuous Capacitor Voltage Mode and Low Output Voltage

In this paper, a modified Sheppard-Taylor converter operating in continuous inductor current mode and discontinuous capacitor voltage mode (CICM/DCVM) is studied and implemented. The operation sequences are described and the averaged model of the converter over a switching cycle is developed. With the obtained, the dc characteristics of the converter were derived, and design criteria for components selection to ensure DCVM operation were reported. The converter is then used for power factor correction in a single-phase rectifier with a front-end diode-bridge. This mode of operation provides the converter some desirable features: zero-voltage turnoff switching and natural purely resistive behavior at low dc output voltage level. This can be achieved by simply using an open-loop control, which offers better reliability than the CICM/CCVM previously reported in the literature, where feedback control is required. The theoretical study of the converter is presented and validated through experimental measurements carried out on a 500 W laboratory prototype. It is shown that this rectifier exhibits an input power factor higher than 99.7% and a source current distortion lower than 6% at small output voltage level.