Patent ID: 8180241

Claim:
An image forming apparatus comprising: a printing unit including a fixing unit that uses a heating unit with a heating lamp to fix a toner image onto a printing medium; a power supply unit to receive a source power and to supply electrical power the printing unit; a temperature measuring unit which measures a surface temperature of the heating unit and outputs a signal representing the measured surface temperature, wherein the power supply unit is configured to control a level of electrical power supplied to the heating lamp during a warm-up of the heating unit that involves at least a first warm-up stage and a second warm-up stage, during the first warm-up stage when power begins to be supplied to the heating lamp, the power supply unit gradually increases a level of power supplied to the heating lamp from zero to a defined supply level according to a phase control of an alternating current (AC) of the source power, during the second warm-up stage, the power supply unit maintains the level of power supplied to the heating lamp at the defined supply level until the measured surface temperature of the heating unit has reached a defined target temperature.