Circuit for detection of short voltage interruptions in supply voltage produces voltage reversal in comparator input to initiate voltage interruption signal

摘要

A comparator (C) has two inputs (VP) plus and (VN) negative across a voltage divider connected between the supply voltage (Vsup) of the circuit monitored and ground. The negative is connected through a transistor (N1) and to ground through a first capacitor (C1). On the occurrence of an interruption this switch is turned off by the action of a capacitor (C3) and a second transistor (P1) preventing the first capacitor discharging holding steady the negative input. A capacitor (C2) connected to the positive input and ground now discharges so that effectively the polarity of the comparator inputs reverse and a voltage failure signal is given.