Voltage monitoring circuit for uninterruptable i.e. redundant power supply of e.g. telecommunications system

摘要

The circuit monitors two voltage inputs (NUBAT1,NUBAT2) and includes a connection unit (E), a coupling unit (K) and an output unit (A). If at least one of the input voltages fails, an abnormal voltage signal appears at an output (RWRF). The connection block includes a first transistor (T1) connected to the monitored voltages as well as a reference voltage (PUBAT) and the coupler via a Zener diode (ZD). The coupling element includes a photodiode (FD) and a phototransistor (FT), where the phototransistor forms part of the output unit which has a second transistor (T2) connected to a supply voltage (ULED), and the output. The entire circuit can be formed as a single semiconductor IC.