| 摘要 |
PURPOSE:To improve fail-safe function of an apparatus for burning gas or other fuel, by constructing its circuit such that a sequence of procedures required from generation of a thermal demand signal to ignition are controlled through associated operation of a pre-purging shift register and a trial shift register. CONSTITUTION:When a safety switch heater SSH is energized via an integration circuit 1, NAND-circuits NA1, NA2 and an AND-circuit AN3through operation of a thermal demand signal generating section TH and a pre-purging shift register PSR is energized, shift is effected in synchronism with clock signals OSC1. When the shift is completed, the heater SSH is turned OFF and a fan BM is set into operation. On the other hand, since shifting by clock signals OSC2 of a trial shift register TRS is also effected via a matching circuit MP, a valve circuit V1C and an ignition controlling circuit IGC are set into operation successively. The conditions of ignition are checked by a film detector FD. Thus, it is enabled to improve fail-safe function of the apparatus. |
