Patent ID: 8515297

Claim:
An apparatus including a fixing device configured to fix a toner image transferred onto a sheet by causing a heating element to generate heat using an induction heating method, the apparatus comprising: an induction coil configured to generate a magnetic field for induction heating; and a power source circuit configured to supply a high-frequency current to the induction coil, the power source circuit comprising: a resonant capacitor connected to the induction coil; a switching element configured to supply electric power to the induction coil; a driving circuit configured to generate a driving signal for driving the switching element; a temperature detection unit configured to detect a temperature of the heating element; and a current detection unit configured to detect a current corresponding to the supplied electric power; a driving signal generation circuit configured to determine a frequency of the driving signal which becomes equal to or higher than a set minimum frequency, according to a difference between the detected temperature and a target temperature of the fixing device, and to generate the determined driving signal, the electric power supplied to the induction coil being increased as the frequency of the driving signal is closer to the minimum frequency; and a determination unit configured to, if the frequency of the driving signal is the minimum frequency and the detected current is equal to or less than a predetermined value, generate a signal representing abnormality of the power source circuit.