| 摘要 |
<p>PURPOSE:To reduce the heat dissipation of a resistor for current control, by providing a broken line detecting circuit and a current supply circuit to an output side of a voltage comparison circuit comparing signal voltages between a temperature detecting circuit and a temperature set circuit so as to reduce the current flowing to a control element controlling the power to a heater. CONSTITUTION:The temperature set circuit 14 of the temperature controller is constituted with a resistor R1, a variable resistor VR and a resistor R2, and the temperature detecting circuit 15 is constituted with a transistor TRQ1, a thermister TH and a resistor R3. A voltage signal set at the circuit 14 and a voltage signal detected at the circuit 15 are compared at the voltage comparing circuit 16. The output side of the comparing circuit 16 is provided with the broken line detecting circuit 17 comprising the TRQ1, a resistor R4 and a TRQ2 and detecting a broken wire of the thermister TH, and the current supply circuit 18 comprising a TRQ3 and a resistor R6 and the like and supplying a current to the heater 12. Further, the output of the comparing circuit 16 is taken as an input to the circuit 18, power is applied to the heater 12 with the output of the circuit 18, allowing to reduce the heat dissipation of the current limit resistor R5.</p> |
