Patent ID: 8818224

Claim:
An apparatus including a fixing device which fixes a toner image transferred onto a sheet by causing a heating element, consisting of a magnetic material which has a characteristic that a magnetic property decreases at a temperature higher than a Curie temperature, to generate heat using an induction heating method, the apparatus comprising: an induction coil configured to generate a magnetic field for induction heating; a resonant capacitor connected to the induction coil; a switching element configured to supply electric power to the induction coil; a driving signal generation circuit configured to determine a frequency of a driving signal for driving the switching element according to the supplied electric power so that a frequency of the driving signal does not become lower than a received data corresponding to a lower limit of the frequency and to generate the driving signal; a temperature detection unit configured to detect a temperature of the heating element; and a setting unit configured to set a lower limit of the frequency of the driving signal generated by the driving signal generation circuit according to the detected temperature so that a frequency of the driving signal does not become lower than a resonant frequency determined by an inductance of the induction coil and an inductance of the heating element, the inductance being variable according to a temperature, and a capacitance of the resonant capacitor, and to transmit data corresponding to the lower limit of the frequency of the driving signal to the driving signal generation circuit.