Patent ID: 6054845
Filing Date: 2000-04-25
Classification: G05F

Abstract:
A current limiting circuit for a controlled semiconductor power component having a main current path, a source terminal, and a control terminal, the circuit which comprises:a sense resistor connected in series with a main current path of a controlled semiconductor power component, said sense resistor having a terminal connected to a source terminal of the semiconductor power component;a first supply voltage terminal and a second supply voltage terminal;a first bipolar transistor having a collector, an emitter, a base, and load path, a second bipolar transistor having a collector, a base, and a load path, and a current source connected in series with said load paths between said first supply voltage terminal and said terminal of said sense resistor connected to the source terminal of the semiconductor power component, said first bipolar transistor and said second bipolar transistors being connected such that respective collector currents thereof are proportional to one another;a third bipolar transistor having an emitter and a load path, and a fourth bipolar transistor having a base, a collector, and a load path connected in series with said load path of said third bipolar transistor between the control terminal and said second supply voltage terminal, said emitter of said third bipolar transistor receiving a current impressed on said emitter proportional to a collector current of said fourth bipolar transistor;said collector and said base of said first bipolar transistor being connected to said base of said third bipolar transistor;said base of said second bipolar transistor being coupled to a node between said emitter of said third bipolar transistor and said collector of said fourth bipolar transistor;said base of said fourth bipolar transistor being coupled to a node between said emitter of said first bipolar transistor and said collector of said second bipolar transistor;whereby an emitter-to-base voltage of said fourth bipolar transistor contains, as voltage components, a voltage drop across said sense resistor, an emitter-to-base voltage of said second and third bipolar transistors with positive sign, and an emitter-to-base voltage of said first bipolar transistor with negative sign, and further voltage components resulting from differences between emitter-to-base voltages of further bipolar transistors operated with a different emitter current density; andwherein said bipolar transistors are of the same type.