| 摘要 |
PROBLEM TO BE SOLVED: To provide a technology capable of reducing a risk of occurrence of gas leakage in a solenoid valve drive circuit in which a solenoid valve arranged on a gas supply line of a gas combustion device is driven to be opened or closed through PWM control of a micro computer.SOLUTION: A first switch control circuit 16 is interposed between a PWM output port 22 of a micro computer 6 and a first switch 8 disposed in a power supply passage to a solenoid valve 4, and electrical conduction and non-conduction of the first switch is changed over from a combination of an output of the PWM output port of the micro computer and an output of a hardware safety circuit 14. When the PWM output port of the micro computer becomes a first potential, the first switch becomes non-conduction state irrespective of the output of the hardware safety circuit and in turn when the first output port of the micro computer becomes a second potential, the electrical conduction/non-conduction of the first switch are determined according to the output of the hardware safety circuit. |
