| 摘要 |
PURPOSE:To stabilize mean electric power by applying the output of a pulse generating circuit to the control element of a heater together with the output of a temperature detecting circuit once a triangular wave and a voltage proportional to a power voltage are inputted. CONSTITUTION:When the temperature of a heater 4 is lower than set temperature, a temperature detecting circuit C generates a high-level output. The output of a triangular wave generating circuit D, on the other hand, is applied to an input of the comparator 24 of a pulse generating circuit E. A DC circuit A outputs a DC voltage proportional to a power voltage. Therefore, the DC voltage proportional to the power voltage is applied to the comparator 24. A transistor 26 turns on during a high-level period when the power voltage is high to turn on an optical Triac 3 during the period, thereby applying a voltage to the heater 4. When the voltage is low, on the other hand, mean applied electric power to the heater 4 is held constant. When the heater 4 reaches the set temperature, the resistance value of a thermistor is decreased and the control element 3 turns off to stop powering up the heater 4. |
