Patent ID: 8792797

Claim:
A fixing device, comprising: a fuser member subjected to heating; a heater provided in the fuser member to heat the fuser member; a thermometer adjacent to the fuser member to detect an operational temperature of the fuser member; and a power supply controller to control power supply to the heater by adjusting a duty cycle defining a ratio of on-time during which the heater is supplied with electricity within a given control cycle, the controller including: a duty cycle calculator operatively connected to the thermometer to calculate a primary value of the duty cycle based on the operational temperature detected by the thermometer; a driver circuit operatively connected to the duty cycle calculator to supply power to the heater according to the duty cycle being input from the duty cycle calculator during operation of the heater, the duty cycle being gradually increased to the primary value upon initial application of power during activation of the heater, and gradually decreased from the primary value upon final application of power during deactivation of the heater; and a duty cycle modifier connected between the duty cycle calculator and the driver circuit to modify the duty cycle by adding an offset value to the primary value to output a modified, secondary value of the duty cycle during activation or deactivation of the heater, such that a total period of on-time divided by the control cycle during activation or deactivation of the heater equals the primary value of the duty cycle calculated by the duty cycle calculator, wherein the controller further includes a lookup table that associates the primary value of the duty cycle with the offset value of the duty cycle, and the duty cycle modifier determines the offset value to be added to the primary value of the duty cycle based on reference to the lookup table.