Fixing device usable with an image forming apparatus

A fixing device useable with an image forming apparatus having a fixing roller, a heater to heat the fixing roller to fix an image on a recording medium, and an alternating current (AC) power source to generate an AC electric power such that the heater heats the fixing roller according to the AC electric power, the fixing device comprising:

• a direct current (DC) power supplier to generate a DC power;
• a unit to selectively control the heater according to the AC electric power and the DC power;
• a relay comprising:
• a first relay contact point disposed on a first AC power supply line between the AC power source and the unit;
• and
• a relay coil to open and close the first relay contact point, the relay selectively supplying the AC electric power from AC power source to the heater and the unit;
• a thermoswitch interposed between the relay coil and the DC power supplier so as to interrupt the DC power from the DC power supplier to the relay coil, when a temperature of the fixing roller exceeds a threshold temperature, thereby controlling the supply of the AC electric power to the heater and the unit according to an temperature of the fixing roller.

A fixing device usable with an image forming apparatus having a fixing roller to fix a toner on a recording medium, a heater to heat the fixing roller, and an alternating current (AC) power source to supply an AC electric power to the heater, the fixing device comprising:

• a power converting part to convert the AC electric power from the AC power source into a high frequency power, and to supply the converted high frequency power to the heater;
• a direct current (DC) power supplier to supply a DC power to the power converting part via a DC power supply line;
• and
• a thermoswitch interposed between the power converting part and the DC power supplier and mounted adjacent to the fixing roller to interrupt the supply of the DC power from the DC power supplier to the power converting part when the fixing roller exceeds a threshold temperature.

A fixing device usable with an image forming apparatus having a fixing roller to fix a toner on a recording medium, a heater to heat the fixing roller, and an alternating current (AC) power supplier to supply an AC electric power to the heater, the fixing device comprising:

• a power converting part to convert the AC electric power of the AC power supplier into a high frequency power and to supply the converted high frequency power to the heater;
• a relay disposed between the AC power supplier and the power converting part to selectively interrupt the AC electric power from the AC power supplier to the heater;
• a direct current (DC) power supplier to supply a DC power to the relay, in order to switch the relay;
• and
• a thermoswitch interposed between the relay and the DC power supplier and mounted adjacent to the fixing roller so as to interrupt the DC power from the DC power supplier to the relay if a temperature of the fixing roller exceeds a threshold temperature.

A fixing device usable with an image forming apparatus having a fixing roller, a heater to heat the fixing roller, and an alternating current (AC) power source to that outputs an AC electric power having a first frequency, the fixing device comprising:

• a direct current (DC) power supplier that outputs a DC electric power;
• a power converting part that receives the AC electric power and includes a transistor transistor logic (TTL) that converts the first frequency of the AC electric power into a second frequency being higher than the first frequency in response to receiving the DC electric power;
• and
• a thermoswitch disposed between the DC power supply and the power converting part that disconnects the DC power from the TTL based on a temperature of the fixing roller.