Current supply with polarity monitoring for communications appts. - detects DC voltage short-circuit to control output voltage regulator

摘要

The current supply (1) has two DC sources each providing a respective current (I1,I2) and DC voltage (Ua+,Ua-). A polarity monitoring circuit (U umlaut) is connected in parallel with one DC voltage (Ua-), supplying a reference input (Uref) for a regulator (2) which is used for limiting or disconnecting the other DC voltage (Ua+). Pref. the polarity monitoring circuit uses a transistor (T1) controlled by the first DC voltage (Ua-), so that it conducts upon a short-circuit of both DC voltages (Ua+,Ua-), the regulator (2) using an operational amplifier (K) controlled by the reference input (Uref) and comparing the first DC voltage (Ua-) with a given reference value. USE - Pulsed current supply protecting supplied communications appts. from incorrect voltages, e.g. crossing from metallic lead to optical fibre upon short circuit, e.g. caused by trenching work or nearby digging.