| 摘要 |
PROBLEM TO BE SOLVED: To use a heater for 100 V even in the case of 200 V. SOLUTION: A thyristor 3 is provided between an AC power source terminal 1 and a ceramic heater 12, and the thyristor 3 is triggered by a trigger circuit 9 in this heater control circuit. In this circuit, a charging and discharging circuit 10 is connected with the thyristor 3. In the charging and discharging circuit 10, a capacitor C1 is connected in parallel with a discharging resistance R1, and a back flow preventing diode D1 is connected with one terminal of the parallel circuit. Then, the diode D1 is connected with the cathode terminal of the thyristor 3, and the charging and discharging circuit 10 is charged by ON currents of the thyristor 3. On the other hand, the other terminal of the parallel circuit is connected through a gate circuit 11 with the trigger circuit 9, and the trigger signal to the thyristor 3 is controlled during the discharging time so that current to a ceramic heater 12 can be controlled according to an AD voltage.
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