| 摘要 |
PURPOSE:To improve a safety of gas equipment by a method wherein a transistor and a thyristor are connected in series and the safety valve is operated when both switching operations are generated. CONSTITUTION:In case that a pilot flame sensing circuit 9 is in trouble and its output V2 is similarly increased as an output V1 of a power supply 8 at the same time as the turning-ON of the power supply switch 7, a gate current iG of the thyristor 10c is not reached to a current to trigger the thyristor 10c. Therefore, in this case, the safety valve 12 is not operated. Then, in case that a collector-emitter of the transistor 11c are short circuited, the thyristor 10c is connected in series with the transistor 11c and the safety valve 12 is not operated. With this arrangement, even if the pilot flame ignition sensing circuit 9 is troubled or the transistor 11c is troubled, the safety valve 12 is not operated, resulting in that a safe operation can be assured. |
