An Active Input Current Waveshaping with Zero Switching Losses for Three-Phase Circuit Using Power Diode

In this paper a zero voltage switched active network (Fig. 1) which can be used in conjunction with single-phase or three-phase ac to dc diode rectifiers is presented. It is shown that application of the proposed switching network in threephase ac to dc boost converter yields zero switching losses while maintaining a unity input power factor. Active network capacitor, Cs, diodes D7, and D8, maintain a zero voltage during turn-off of Q1, and Q2, Capacitor, Cs, discharges through the boost inductors of the circuit thus limiting the rate of rise of current during turn-on. Moreover, the advantage of the proposed active network is that it can maintain a zero voltage switching over the entire range of the duty cycle of the operation. Consequently, boost stage can be used directly to control the dc bus voltage by varying the duty cycle at Constant switching frequency. The resulting advantages include higher switching frequencies, and better efficiency. Finally the operation of the active switching network is verified experimentally on a prototype three-phase ac to dc converter.