Patent ID: 8139970

Claim:
An image fixing control system comprising: a power switching unit connected to a power supply; a heating roller; a temperature detector for detecting a temperature of the heating roller; and a controller for detecting a temperature variation slope of the heating roller using the temperature detected by the temperature detector and controlling an on and off switching operation of the power switching unit according to the detected temperature variation slope, wherein the controller causes varying a duty ratio of power to be supplied to the heating roller according to the detected temperature variation slope, when power is supplied to the heating roller; wherein the controller controls the on and off switching operation of the power switching unit according to the duty ratio of power to be supplied to the heating roller; and wherein the duty ratio of power is gradually increased when a temperature decrease slope based on the detected temperature variation slope is below a second predetermined slope, and the duty ratio of power is gradually decreased when a temperature increase slope based on the detected temperature variation slope is below a first predetermined slope.