Patent ID: 7466565

Claim:
A switching power supply unit, comprising: a power supply main section switching a DC input voltage inputted from a first power supply to convert the DC input voltage into an AC voltage, and outputting a DC output voltage into a second power supply, the DC output voltage being obtained by transforming and rectifying the AC voltage; and a voltage detection section having a voltage detection transformer, one or more switching elements, and detection signal lines, wherein the voltage detection transformer includes a first transformer coil as a primary winding being intermittently applied with the DC input voltage in response to on/off of the switching element, and a second transformer coil as a secondary winding being connected to the detection signal lines, and wherein the voltage detection section has two switching elements each disposed in each of both ends of the first transformer coil and a regeneration circuit which regenerates energy stored in the voltage detection transformer for the first power supply, and the first transformer coil and the two switching elements are connected in series with each other between a couple of output terminals of the first power supply.