Patent ID: 7723964

Claim:
A power supply device that improves, when setting a voltage obtained by converting an alternate-current power supply into a direct-current voltage to a load voltage, a power factor by short-circuiting the alternate-current power supply via a reactor, wherein a switching operation is performed on a switching element of a power-factor improving unit that includes the reactor, an output voltage of the power-factor improving unit is set to the load voltage by switching on and off the switching element based on a result of comparison between an input current and an input-current reference signal of a power-supply voltage waveform, a zero cross of the alternate-current power supply is detected, the switching operation is performed on the switching element a predetermined number of times based on a detection of the zero cross, and number of switching the switching element is set in such a manner that a power supply phase of the alternate-current power supply is within 90 degrees.