Circuit arrangement for limiting and regulating the collector current of the control element transistor of a switching network component

Claim 1

A circuit arrangement for limiting and regulating the collector current of a transistor having a collector, an emitter and a base and in a switching network component which comprises a current transformer including a primary connected in series with the collector and a secondary, said circuit arrangement comprising: a variable resistor, including a first tap, and a diode connected in series, the series combination connected across said secondary, the setting of said variable resistor representing the maximum collector current; a half-wave rectifier, including a charging capacitor, connected across the secondary; a voltage divider, including a second tap, connected across said charging capacitor; first and second bistable switches, each including first and second inputs and an output; an integrated regulating module including a reference voltage source, a current regulating operational amplifier having first and second inputs and an output, a disconnect device including an input and operable to disconnect the collector current, and at least one output connected to and controlling said base; said first input of said first bistable switch connected to said reference voltage source, said second input of said first bistable switch connected to and driven by said module output, and said output of said first bistable switch connected to said second input of said current regulating operational amplifier, said first input of said current regulating operational amplifier connected to and sensing the voltage at said second tap as representing the voltage across said charging capacitor; and said first input of said second bistable switch connected to a reference potential, said second input of said second bistable switch connected to said first tap to sense whether the collector current is above the set maximum, and an output connected to drive said input of said disconnect device.