Multi-channel single stage high power factor ac to dc converter

Abstract

A multi-channel single stage high power factor AC to DC converter comprising a pair of input terminals for connecting to an a.c. supply voltage, a bridge rectifier connected across the input terminal, for converting the a.c. supply voltage to a d.c. voltage, and a D.C. to D.C. converter connected to the bridge rectifier and including a high frequency switch for converting the d.c. voltage to high frequency intermittent pulses, a transformer having a primary winding connected to the high frequency switch and having at least two secondary windings each connected to a respective rectifier for producing a d.c. output voltage thereacross. A pair of capacitors are connected in the input of the DC to DC converter so that when the switch is OPEN a first one of the capacitors receives energy from the a.c. supply and a second one of the capacitors receives energy from the transformer, whilst when the switch is CLOSED the first capacitor restores energy to the transformer and the second capacitor restores charge to the a.c. supply. Such a configuration avoids the need to split the energy transfer capacitor between the input and output of the DC to DC converter and thus avoids duplication of part of the energy transfer capacitor in each output channel when multiple outputs are provided.