| 摘要 |
PURPOSE:To accomplish automatic control of power supply in case of power failure by means of a second switch interlocked with the main switch of the equipment body employed for the on/off operation between the main power and the control circuit for the first switch designed to turn the auxiliary power source on or off the main power source depending on the voltage changes of the main power source. CONSTITUTION:A drop in the voltage of the DC main power source due to power failure or the like is detected with a detection circuit 8 while the main switch of the equipment body is closed. Based on the output and a reference potential of a main power source 2 through a second switch remaining closed, a opening/closing control circuit 9 outputs a closing signal to close a first switch 11. Thus power is fed from an auxiliary power source. As the voltage of the main power source 2 rturns to normal, a diode is biased in the reverse direction and a zero voltage is detected to open the switch 11. Thus, the power feeding is halted. When the main switch is opened while the switch 11 is closed, the switch 3 is opened. Due to lack of the reference potential, the action of the opening/closing control circuit 9 is halted leading the switch 11 to be opened. |
