Patent ID: 8491187

Claim:
A temperature detection apparatus configured to detect the temperature of a heating element to which a high voltage is applied, said apparatus comprising: a transformer; a thermistor attached directly to an electrically conductive site of said heating element and having a resistance value varying depending on the temperature of said heating element, said thermistor being connected between secondary coils in said transformer; a DC voltage source and a transistor configured to supply required AC power to a primary coil in said transformer; a current detection resistor configured to detect a current flowing through the primary coil in said transformer that is proportional to a current flowing through said thermistor and secondary coils in said transformer, when said primary coil in said transformer is supplied AC power by said DC voltage source and said transistor; and a current detection circuit detecting a voltage generated across said current detection resistor when current flows through said current detection resistor, and outputting a voltage proportional to the voltage.