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The present invention provides a power supply apparatus which can suppress a raising and hunting of output (DC voltage) to a load which is light. The power supply apparatus comprises an AC-to-DC converter for supplying a load with a DC voltage, and a switching operation controller for correcting a p

The present invention provides a power supply apparatus which can suppress a raising and hunting of output (DC voltage) to a load which is light. The power supply apparatus comprises an AC-to-DC converter for supplying a load with a DC voltage, and a switching operation controller for correcting a power factor and controlling a switching element so that an output or a DC voltage of the AC-to-DC converter becomes a predetermined target value. The switching operation controller has a low-pass filter for smoothening the DC voltage with a variable cut off frequency. By varying the cut-off frequency of the low-pass filter, it is possible to recognize a rising of the DC voltage to suppress and stabilize a boost and hunting of the DC voltage in a light load state.

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[ What is claimed is:] [1.]1. A power supply apparatus comprising:an AC-to-DC converter for supplying a DC voltage converted from output of an AC power supply, the AC-to-DC converter including at least a switching element, a reactor and a diode;a current detecting section for detecting a value of cu

[ What is claimed is:] [1.]1. A power supply apparatus comprising:an AC-to-DC converter for supplying a DC voltage converted from output of an AC power supply, the AC-to-DC converter including at least a switching element, a reactor and a diode;a current detecting section for detecting a value of current of the AC power supply;an input voltage detecting section for detecting a value of voltage of the AC power supply;a DC voltage detecting section for detecting a value of DC voltage supplied from the AC-to-DC converter;a switching operation controller for correcting a power factor based on each value obtained by the current detecting section, the input voltage detecting section and the DC voltage detecting section, and for controlling an operation of the switching element to control the DC voltage to a target voltage; anda low-pass filter for smoothening the DC voltage from the DC voltage detecting section, which is included in the switching operation controller and has a variable cut-off frequency.