| 摘要 |
PURPOSE:To prevent stop of an operation of the whole system, by selecting that which is not subjected to power failure, out of electric power sources of plural systems, and supplying electric power to a common device. CONSTITUTION:At a normal time, a switching circuit 5 selects that which can supply electric power, from AC systems 11a, 11b, and outputs it to common devices 8a-8c. For instance, in case when the first power source input line 11a is cut off by some cause, and this AC system becomes a power failure state, a low level detecting circuit 2 detects a drop of output voltage of the first rectifying circuit 1a, and a signal for showing that voltage of the first power source drops is outputted to a controlling circuit 4. DC electric power supplied from the second rectifying circuit 1b is inputted in advance in a regulator 3, and the controlling circuit 4 selects the second power source and outputs it to the common devices 8a-8c. |
