Getakteter Schaltnetzteil mit Leistungsfaktorkorrektur

摘要

A switched mode power supply is provided which combines voltage regulation and power factor correction in a single converter stage. The power supply comprises a bridge rectifier (39) feeding a double rectified voltage sine wave to a flyback converter comprising input and output circuits (40, 41) connected by an energy-storing transformer (42). The input circuit (40) comprises an energy-storing inductor (43), a switching device (44) connected in series with the inductor across the output of the bridge rectifier, a control arrangement (60-71) for controlling the cyclic turning on and off of the switching device (44), and a coupling capacitor (45) connected in series with the primary winding (46) of the transformer across the switching device. The control arrangement comprises switch-on timing means (60-65) for turning on the switching device upon a turn-on condition being reached in which the inductor (43) and transformer (42) have stored energy levels such that the inductor and transformer are equally balanced to charge one another, and on-time control means (65-71) for maintaining the switching device (44) on for a period dependent on the desired value of said regulated dc output voltage. In this manner, the converter input current is made proportional to the input voltage giving the desired high power factor.