Output voltage ripple reduction of a high power factor mode operated isolated charge-pump AC/DC converter

Output voltage ripple reduction technique for a new AC/DC-converter topology based on a half-bridge driven transformer isolated charge pump is presented and studied experimentally. The main principle is that the double line frequency output voltage ripple related to high power factor mode operated resonant AC/DC converters is reduced by the switching frequency variation controlled by instantaneous line voltage feed forward. Among output voltage ripple the line current waveform and conducted electromagnetic interference (EMI) are considered as well. The measurements with a prototype proved output voltage ripple reduction from 1.4 (rms) to 0.3V (rms) by using the principle suggested in the paper. Other interesting observations were that this also shaped the input current waveform from EN61000-3-2 Class D to A and also reduced the low frequency differential mode average emissions by approximately 15 dB.