POWER SUPPLY DEVICE, POWER SUPPLY SYSTEM, AND ZERO-CROSS POINT DETECTION METHOD OF AC COMMERCIAL VOLTAGE IN POWER SUPPLY DEVICE

摘要

To provide a power supply device allowing accurate detection of a zero-cross point with a reduced size of a circuit.SOLUTION: A power supply device 1 comprises: an insulation-type flyback AC/DC converter 2 loaded with an active PFC function converting the AC voltage of an AC commercial power source into a DC voltage V; an AC coupling part or an offset part 3 taking out a ripple voltage waveform Vfrom the DC voltage Voutputted from the AC/DC converter; a half-wave rectifier circuit 5 connected to the AC coupling part or a latter part of the offset part and making the ripple voltage waveform Vto a half-wave form; and a zero-cross point detection part 4 connected to a latter part of the half-wave rectifier circuit and having a Schmidt trigger circuit 6 outputting a binary signal on the basis of the half-wave.SELECTED DRAWING: Figure 1