Drive circuit for optical display elements, in particular light-emitting diodes (LEDs)

摘要

In power station protection practice, use is frequently made of optical signalling devices which indicate an excitation or triggering (tripping) of the protection branch. These signalling devices also require appropriate drive circuits. A novel drive circuit which renders possible a plurality of signalling variants for an optical display element D1 comprises an operational amplifier (OPA) N1.2 which has in the negative feedback a three-stage slide (sliding-dolly) switch X13 and a diode V12 with a downstream resistor R21. The input of the operational amplifier N1.2 is connected, on the one hand, to the output A of a control source V24 via a resistor R1, and on the other hand with the negative supply voltage (-) via a capacitor C9. The output is connected via a current-limiting resistor R44 with a downstream zener diode V45 in the reverse direction to a light- emitting diode D1 whose cathode is connected to the negative supply voltage (-). Connected to the anode of the negative-feedback diode V12 is a further diode V13 which is followed by a signal-pole (monopole) switch X12. The sliding switch X13 can be used to arrange that the light-emitting diode D1 is either synchronized with the control source V24 or is switched on by it and is switched off by the switch X12, or is always dark. IMAGE