Interface circuit between LV and HV networks - using LED and phototransistor forming optical coupling between electronic circuit and electromechanical device

摘要

The interface circuit is used to transfer signals between a LT network and a HT network, e.g. between an electronic unit and an electromechanical device. It comprises an input stage including a light emitting diode (D1) and an output stage with a phototransistor (PT), optically coupled to the latter. The phototransistor (PT) is associated with a transistor amplifier (T1, T2) and a HT voltage divider (R2, R3). The centre-top of the voltage divider, coupled to the emitter of the phototransistor (PT), for limiting the collector-emitter potential.