TEMPERATURE CONTROL CIRCUIT FOR ELECTRIC HEATER

PURPOSE:To simplify the constitution of circuits by a method wherein a heater sensor unit provided with a means for retaining the supply of power to a heater electrode for a fixed period of time after starting the power supply thereto and with a means for detecting the temperature of a heat-sensitive element when power is not supplied, is connected to a commercially available power source. CONSTITUTION:A heater electrode 2a in a heater sensor unit 2 constituted of the heater electrode 2a, a sensor electrode 2b and a heat-sensitive element 2c is connected to a commercially available power source 1 through a relay contact point Ry1 and a power source switch SW. Further, one end of the sensor electrode 2b is connected to a 100V line through an impedance dividing circuit 7 and the other end of the same to a smoothing circuit 3, and a relay drive circuit 8 is allowed to operate by an output from a switching circuit 4 connected to the smoothing circuit 3. Accordingly, a fixed time that is retained after starting the supply of power to the heater electrode 2a is made variable in accordance with a room temperature, whereby it is not required to eliminate unnecessary signals, so that the constitution of the circuits can be simplified.