| 摘要 |
PURPOSE:To prevent in a safe way an abnormal rise of temperature, by controlling the discontinuation of electric conduction to a heat generator after detecting the state of conduction and cutting off the electric conduction when a fault arises with use of a power supply connecting means. CONSTITUTION:A triac 5 for connection of power supply is turned on by the control signal and via a photocoupler 8 and a rectifier 9 to give the electric conduction to a halogen lamp 2, etc. of a heat generator which is used for exposure of copying. At the same time, a timer is triggered. Then a capacitor 13 is charged via a transformer 11 and in a accordance with the time of conduction corresponding to the rise of temperature of the lamp 2, and the state of conduction is detected. This charging voltage turns on a switching transistor via an AND gate which opens after the lapse of the timer time. Thus a relay is energized and a relay contact 10 opens. As a result, the power supply to the lamp 2 is cut off even when the triac 5 which works in reponse to the control signal has a fault and is kept on. In such way, an abnormal rise of temperature is always prevented in a stable way although some fault arises to the power supply connecting means. |
