Patent ID: 8855510

Claim:
An image forming apparatus comprising: an image forming unit to form an image and to transfer the image onto a printing medium; a fixing unit to fix the image transferred onto the printing medium; a power supply to supply operating power to the fixing unit; a temperature sensor to sense a temperature of the fixing unit; a first protection unit to compare the sensed result of the temperature sensor with a first predetermined reference value and to output a signal according to a comparison result between the sensed result of the temperature sensor and the first predetermined reference value, the first protection unit comprising a first comparator to receive a voltage from the temperature sensor and a first predetermined reference voltage and to output a signal according to a comparison result between the received voltage and the first predetermined reference voltage; a switching unit to turn on or off in order to respectively pass through or cut off the operating power supplied to the fixing unit in accordance with a level of the signal output from the first protection unit; a second protection unit to compare the sensed result of the temperature sensor with a second predetermined reference value and to output a signal according to a comparison result between the sensed result of the temperature sensor and the second predetermined reference value, the second protection unit comprising a second comparator to receive a voltage of the temperature sensor and a second predetermined reference voltage and to output a signal according to a comparison result between the received voltage and the second predetermined reference voltage; a relay unit to turn on or off in order to respectively pass through or cut off the operating power supplied to the fixing unit in accordance with a level of the signal output from the second protection unit; and a controller to receive the sensed result of the temperature sensor through an analog digital converter (ADC) port and to control a switching operation of the switching unit in accordance with the received sensed result.