| 摘要 |
PROBLEM TO BE SOLVED: To inexpensively detect a fan motor current in a combustion equipment without being affected by a temperature. SOLUTION: A resistance R of a current.voltage converting means is connected to an output side of a fan motor driving circuit. A voltage.duty ratio converting circuit 30 is connected in both ends of the resistance R to convert a voltage between the both ends into a pulse signal of a duty ratio corresponding to the height of the voltage. The pulse signal of the duty ratio in response to a voltage value converted by the voltage.duty ratio converting circuit 30 transmits accurately a fan motor current because the duty ratio is not affected even when its frequency varys with change of an ambient temperature. The pulse signal is transmitted using a photocoupler 35 while keeping an insulated condition between a driving side of a fan motor and a control circuit side, so as to be converted into a voltage signal in response to the duty ratio by a smothing circuit 43. A fan motor current value free from influence of a temperature is provided by a control circuit 40 based on the voltage signal. |
