Two phase PFC circuit to keep constant output voltage even under momentary power outages
One of the important functions of AC/DC converters is to supply a stable output DC voltage to electronic equipment even if momentary power outages occur. During the momentary power outage, the power is supplied from the storage capacitor of a PFC circuit to load through an isolated converter. Therefore very large capacitors should be necessary to compensate during interruption of AC power. Furthermore, because the storage capacitor voltage decreases according to discharge of the storage energy, the isolated converter should be necessary to design corresponding to a wide input voltage range. This causes increasing the power loss and volume of the isolated converter. This paper proposes a two-phase PFC circuit for keeping a constant output-voltage even under momentary power outages. When the momentary power outage occurs, the proposed PFC circuit operates as a boost regulator in order to keep the constant output voltage. This circuit is simple topology in which a diode and a mode change switch are added to a conventional two-phase PFC circuit. Effectiveness of the proposed PFC circuit is tested by a simulation and an experiment.