Patent ID: 7949885

Claim:
An image forming apparatus comprising: a capacitor that is charged by an external power source, and dischargably stores therein power; a load that receives supply of power; a control unit that controls the load; a switching unit that switches power sources to supply power to the load and the control unit between the external power source and the capacitor; a detecting unit that detects whether the voltage of the external power source has dropped below a first or second threshold level; and a power supply unit that causes the switching unit to switch the power source to supply power to the load and the control unit from the external power source to the capacitor when the detecting unit detects that the voltage of the external power source has dropped below the first threshold level, and supplies power to the load and the control unit, and causes the capacitor to supply power to the load and the control unit before a voltage of the external power source drops below the second threshold level where malfunction of any one of the load and the control unit occurs, and stops the supply of power from the capacitor to the load and the control unit after the voltage exceeds the first threshold level.