Patent ID: 8224203

Claim:
A fixing device comprising: a fixing member; an excitation coil for induction-heating the fixing member; an induction heating power supply that supplies high-frequency power to the excitation coil; an output power detection circuit that detects an output power of the induction heating power supply; a power control circuit that variably controls the output power of the induction heating power supply to increase or decrease; and a temperature sensor that detects temperature of a surface portion of the fixing member, wherein the power control circuit decreases the output power in step wise manner between an upper limit and a lower limit, which is a minimum power above 0 W, and wherein when the power applied to the excitation coil reaches a minimum power set larger than 0 W, the power control circuit maintains the minimum power while the detected temperature detected by the temperature sensor is within a predetermined control temperature range and controls the output power of the induction heating power supply to shift from the minimum power to 0 W when the detected temperature deviates from the predetermined control temperature range.