| 摘要 |
PURPOSE:To prevent the occurrence of troubles such as overheating and fire, by stopping the operation of an apparatus immediately when a temperature sensitive element is disconnected. CONSTITUTION:In the normal operation, DC voltages which appear in output terminals (a) and (b) of a bridge circuit 1 are changed in accordance with the change of the resistance value of a temperature sensitive element 4. However, if the element 4 is disconnected, the element 4 has a very high resistance value, and therefore, the base and the emitter of a transistor TR9 have the same potential approximately, and the TR9 becomes nonconductive. Thus, the supply of a power source voltage +Vcc to an active element 6 is stopped. Consequently, the element 6 is not operated to cut off the power supply to a heater control circuit 8 for heating. |
