| 摘要 |
PURPOSE:To prevent a supply voltage fluctuation effect without using a stabilized power supply by arranging a preheat control circuit to generate a preheat control signal as a result of amplification of a difference between a detection signal corresponding to the supply voltage and the preheat standard signal. CONSTITUTION:A preheat control circuit 11 draws through a bridge rectifier RFD, a rectifying diode D3 and a smoothing capacitor C1, a supply voltage (e) stepped down with a step-down transformer T3 as a d.c. voltage with a pulsating current eliminated. Further, the d.c. voltage is divided by a dividing circuit consisting of registers R4 and R5 to obtain a detected voltage Vb corresponding to the supply voltage (e). The detected voltage Vb is input into a differential amplifier 3 in which a control signal Vc is generated by amplifying a difference from a standard voltage E2 which specifies a control target value at a preheat control time with a specified rate of amplification.
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