| 摘要 |
PURPOSE:To prevent the response time of the titled circuit from exceeding a predetermined value irrespective of the magnitude of the resistance of a flame by a method wherein a clamp circuit for limiting the amounts of charges to capacitors is provided. CONSTITUTION:When a burner is ignited, AC 100V is rectified due to the rectifying action of the flame to thereby charge the capacitors C1 and C2. Accordingly, the potential at the point A drops and when it drops beyond a comparative reference voltage produced through resistors R4, R5 and the output Vout of a comparator 5 goes to ''H'' level. At this time, the resistance of the flame varies according to the condition of the flame and the amounts of charges accumulated in the capacitors C1 and C2 vary. However, the potential at the point A is prvented from becoming larger than a predetermined value due to the existence of the clamp circuit formed of diodes D2, D3 and a resistor R7 and accordingly, the charges accumulated in the capacitors C1 and C2 are limited. As a consequence, it is possible to prevent the response time of the flame detecting circuit from exceeding the predetermined value. |
