| 摘要 |
PROBLEM TO BE SOLVED: To prevent an increase in temperature ripples, and the generation of switching noise and harmonics of a heater. SOLUTION: A switching element 7 is made on by the input of a trigger signal, and made on and off with a microcomputer 9 in a unit of an integral multiple of a half wave of a power source wave form according to a control signal outputted from the microcomputer 9 so that a heating part 6 keeps a specified temperature. A switching element 8 carries current by the input of the trigger signal and breaks current in zero cross of the power source wave form. Load current of heaters 4, 5 and power supplied to the heaters 4, 5 can finely controlled by wave number control and phase control of the switching elements 7, 8.
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