Power supply circuit with power factor correction

摘要

A power supply circuit for powering a load with bi-directional current comprises means for supplying d.c. power from an a.c. voltage, a series half-bridge converter, and a boost converter. The series half-bridge converter alternately impresses a d.c. bus voltage from a bus conductor across a load circuit first with one polarity and then with the opposite polarity. The series half-bridge converter includes a first switch interposed between the bus conductor and a bridge-switch end of the load circuit; a second switch interposed between ground and the bridge-switch end of the load circuit; and a switching control circuit for alternately switching on the first and second switches. The boost converter comprises a boost capacitor connected between the bus conductor and ground and whose level of charge determines the bus voltage on the bus conductor; a boost inductor for storing energy from the means for supplying d.c. power, the boost inductor being connected by a one-way valve to the boost capacitor for discharging its energy into the boost capacitor; and means for periodically connecting a load end of the boost inductor through a low impedance path to ground, such path including a boost switch. A condensed power supply circuit results from making the second switch of the series half-bridge converter additionally serve as the boost switch. An alternative circuit simplification results from making constant the ratio of on time to switching repetition period of the boost switch.