Patent ID: 7564574

Claim:
An image forming apparatus comprising: a fixing device configured to fix a toner image on a recording medium with a heater which generates heat when applied with power; a main and an auxiliary power supply configured to feed power to said fixing device; a switching circuit configured to selectively establish a usual mode in which said main power supply is connected to said fixing device for feeding power to said fixing device or an auxiliary mode in which said main power supply and said auxiliary power supply both are connected to said fixing device for feeding power to said fixing device; and a control circuit configured to control said switching circuit and including a temperature sensor responsive to a temperature of said fixing device; wherein said control circuit causes said switching circuit to establish said auxiliary mode in the event of continuous fixation, controls, in said usual mode, an amount of power being fed from said main power supply to said heater in accordance with an output of said temperature sensor, and controls, in said auxiliary mode during continuous fixation, an amount of power being fed from said main power supply and said auxiliary power supply to said heater without regard to the output of said temperature sensor.