Voltage and current stress reduction in single-stage power factorcorrection AC/DC converters with bulk capacitor voltage feedback

摘要

Single-stage power factor correction (PFC) AC/DC convertersnintegrate a boost-derived input current shaper (ICS) with a flyback ornforward DC/DC converter in one single stage. The ICS can be operated inneither discontinuous current mode (DCM) or continuous current moden(CCM), while the flyback or forward DC/DC converter is operated in CCM.nAlmost all single-stage PFC AC/DC converters suffer from high bulkncapacitor voltage stress and extra switch current stress. The bulkncapacitor voltage feedback with a coupled winding structure is widelynused to reduce both the voltage and current stresses in practicalnsingle-stage PFC AC/DC converters. This paper presents a detailednanalysis of the bulk capacitor voltage feedback, including thenrelationship between bulk capacitor voltage, input current harmonics,nvoltage feedback ratio, and load condition. The maximum bulk capacitornvoltage appears when the DC/DC converter operates at the boundarynbetween CCM and DCM. This paper also reveals that only the voltagenfeedback ratio determines the input current harmonics under DCM ICS andnCCM DC/DC operation. The theoretical prediction of the bulk capacitornvoltage as well as the predicted input harmonic contents is verifiednexperimentally on a 60 W AC/DC converter with universal-line input