POWER SUPPLY DEVICE AND IMAGE FORMING APPARATUS

摘要

PROBLEM TO BE SOLVED: To provide a switching power supply device whose power supply to an external load can be stopped as early as possible when an alternating-current supply voltage is interrupted. SOLUTION: When it has been detected by a light load detection circuit 32 that a power load is low, for example, in power saving mode and interruption of input of AC supply voltage is detected by an AC interruption detection circuit 31, a power supply unit 19 outputs an instructing signal to stop a switching operation from a stop signal output circuit 33 to a switching circuit 28. As a result, a current flow arising from discharging of electric charges accumulated in a smoothing capacitor 23 to the primary side of a transformer 24 is stopped and power supply to an external power load is stopped early. COPYRIGHT: (C)2011,JPO&INPIT