Opto-electronic isolator system in light modulators - uses infrared emitting diode with coupled infrared phototransistor emitter

摘要

The system uses an optically coupled isolator to replace the isolating transformer. The isolator has at its input an infrared emitting diode and an infrared phototransistor transmitter. The source does not supply pulses capable of actuating the diode. The diode emitting infrared radiations will change the characteristics of the coupled phototransistor. To increase the sensitivity of the system a 47 mf 25 volt capacitor (a) plus a 1.2 volt Zener diode and a 570 ohm resistance (n) prebias the diode of the optoelectronic circuit. The Zener diode limits the current at the terminals of the diode. The prebiassing current is tapped again at the supply output of the secondary part of the optoelectronic circuit.