| 摘要 |
PROBLEM TO BE SOLVED: To prevent fluctuation in the characteristics of parts from having effect on the peak value or the oscillation frequency of high voltage by inputting a pulse width modulated signal to the base of a transistor and separately exciting a booster transformer through an LC oscillation circuit to induce an AC voltage in the secondary coil thereof. SOLUTION: A flame detecting circuit 2 comprises a microcomputer 3 having a PWM port 31 for delivering a PWM signal to a transistor 4 connected with the primary coil 51 of a booster transformer 5 and a capacitor 6 forming an LC oscillation circuit. Since the transistor 4 is turned on/off in synchronism with the PWM signal, the LC oscillation circuit is excited separately to oscillate at a same frequency as the PWM signal. Consequently, a sine wave AC voltage of same frequency as the PWM signal is induced in the secondary coil 52 of the booster transformer 5.
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