| 摘要 |
PURPOSE:To operate a microcomputer for as a long time as possible even if a commercial power source has a failure unexpectedly, by powering up the microcomputer and a control circuit other than necessary irreducible relative equipment through a connector controlled by the output of an Ac power source detecting circuit. CONSTITUTION:If a commercial frequency power source 1 has a failure at certain time, the 20V AC output voltage of a power source 2 drops to zero momentarily, so the DC output voltage of an AC power source detecting circuit 4 also drops to zero. Therefore, the connector 5 composed of, for example, a transistor 51 is cut off and the feeding of a DC voltage to control circuits B and C is stopped simultaneously with the power failure. A microcomputer 3 and a control circuit A for necessary irreducible relative equipment are supplied a voltage high enough for their operation for a certain time even after the power failure by charges in a smoothing capacitor 26. |
