Patent ID: 7542693

Claim:
A phase controlling device controlling a phase of alternating current (AC) power to regulate to a predetermined temperature an exothermic temperature of a fuser of an image forming apparatus, the phase controlling device comprising: a first signal generating unit generating an error signal that corresponds to a difference between the predetermined temperature of the fuser and an actual temperature of the fuser; a second signal generating unit generating a soft start signal that drives the fuser to prevent transient current flow from occurring during a start of the fuser, and providing the soft start signal to the control signal generating unit; a pulse generating unit generating a sawtooth wave pulse signal that increases with time during a half period of the AC power; and a control signal generating unit comparing the error signal and the sawtooth wave pulse signal and outputting a phase control signal controlling the phase of the AC power, wherein the second signal generating unit comprises a differential circuit between a power supply voltage having a first predetermined voltage level and a second predetermined voltage level.