| 摘要 |
PURPOSE:To obtain a service interruption detector conforming to the required specification of an information processor without employing a large capacity smoothing capacitor by a method wherein two sets of service interruption detecting circuits having different reference voltages are provided and a switching signal is generated when signals of both the circuits are outputted. CONSTITUTION:If power supply is interrupted, a comparator 12 makes a signal rise when an input voltage becomes lower than a first reference voltage V2 which is a little lower than a rated input voltage and a timer 13 generates a first service interruption detection signal (S1) after a predetermined time passes. A comparator 22 generates a second service interruption detection signal (S2) when the input voltage becomes lower than a second reference voltage V3 which is a little higher than the input limit of a power supply apparatus. An AND circuit 3 generates a signal (S) for switching a power supply to a backup power supply. With this constitution, as the service interruption signal (S) is not generated for a predetermined time and the second reference voltage is set at a low value, the capacity of a smoothing capacitor can be reduced. |
