| 摘要 |
PURPOSE:To prevent the damage to a backup function even in the variation of supply voltage at a main power source by providing a switching circuit to feed the current from a backup power source when the service interruption is detected at the main power source to supply the power in a normal condition. CONSTITUTION:If a main power source 1 is interrupted and a service interruption signal is outputted with the output of a comparator CP1 turned to 'L', transistor Q3 and Q4 will be turned OFF and a transistor Q5 turned ON. Through a diode D4 from the secondary battery B of a backup power source 2 the current is fed to a working load 5 (including the service interruption detection circuit 3) through a switching regulator 7. On the other hand, if the main power source 1 is not interrupted, with the output of the capacitor CP1 turned to 'H' transistor Q3 and Q4 will be turned ON, the transistor Q5 turned OFF and the power supply from the backup power source 2 interrupted. |
