Isolated Active-Clamped SEPIC PFC Converter Based on SiC Devices and Integrated Magnetics

An isolated active-clamped SEPIC PFC converter based on SiC devices and integrated magnetics is presented. Multiple advantageous features are achieved with a single integrated four-winding magnetic structure, including zero voltage switching (ZVS) for the SiC MOSFETs, isolated output, lossless clamp for the output diode and ripple steering for the input inductor current. Power density is significantly improved by integrating the input inductor with the isolation transformer. Input current ripple reduction can be achieved by adjusting the leakage inductances. A fourth winding together with a low cost, low current rating diode is used to suppress the resonance induced by the parasitic capacitance of the output diode and to clamp the peak voltage across the output diode. With the integrated magnetic structure (IMS), the favorable features of the SiC devices are exploited and their parasitics induced adverse impact is reduced. The performance of the converter with the IMS is verified with a 1.5kW prototype switching at 200 kHz. The power density of the converter is increased by 21% compared to the converter with discrete magnetics.