| 摘要 |
PURPOSE: A preventing circuit of overheating of a heat radiator is provided to protect a heat radiator by cutting off power fed to the heat radiator when the heat radiator is overheated. CONSTITUTION: A heat radiator(1) generates heat by the supply of power to the heat radiator. If power is fed to a resistance(R1) and a thermistor(10), voltage given to both ends of the resistance and the voltage given to both ends of the thermistor is divided according to the resistance value of the resistance and the thermistor. If the resistance of the thermistor is reduced by the reduction of heat generating in the heat radiator, the voltage given to the both ends of the thermistor is increased thus the voltage given to the both ends of the resistance is decreased. If the voltage is reduced less than Zener voltage, a Zener diode(ZD) is turned off and a thyristor(31) is turned off. Voltage of a voltage terminal(Vcc) is fed to the heat radiator via a passage A. If heat is generated from the heat radiator over a saturation temperature, the voltage fed to the heat radiator is cut off. Thereby, the heat radiator is prevented from being damaged or burned.
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