| 摘要 |
PURPOSE:To prevent malfunction with a small-size and simple structure and further prevent any trouble by a method wherein a second power supply is not insulated by a commercial power supply, but a connection between an operation control circuit and a motor driving circuit is carried out through a photo-coupler. CONSTITUTION:A rotational speed output circuit 40 may receive a rotational speed signal generated at a frequency responding to a rotational speed of a fan motor M, and is converted into a value in which a photo-diode 22a of a photo-coupler 22 can be driven. It is supplied to the photo-coupler 22 and the photo-coupler 22 causes a photo-diode 22a to be lit (or diminished), to cause a photo-transistor 22b to be conductive (or non-conductive). A rotational speed signal is transmitted to a combustion control circuit 10 while its input side and output side being electrically insulated. Thus, the combustion control circuit 10 may continue its controlling operation while monitoring a rotational speed of the fan motor M. |
