US 5,210,481 A · Voltage/current characteristics control circuit particularly for protecting power transistors

Abstract

Voltage/current characteristics control circuit particularly for protecting power transistors, which comprises at least one power transistor; the emitter terminal of a first transistor is directly connected to the output of the power transistor; the emitter terminal of a second transistor is connected to the first terminal of the power transistor by means of a first resistor. The collector terminal and the base terminal of the first transistor are connected to a current source. The base terminal of the first transistor is connected to the base terminal of the second transistor, and the circuit furthermore comprises a protection circuitry. The circuitry is connected to the collector terminal of the second transistor through a differential stage which comprises a third transistor and a fourth transistor; the third transistor and fourth transistor have a respective second resistor and third resistor arranged in series. Divider means are furthermore provided and are interposed between the second terminal of the power transistor and the base terminals of the third transistor and fourth transistor.

Claims15

Dependent claims

A voltage/current characteristics control circuit particularly for protecting at least one power transistor, said power transistor having a first and second terminal, said circuit having an emitter terminal of a first transistor directly connected to the first terminal of said power transistor, an emitter terminal of a second transistor connected to the first terminal of said power transistor by means of a first resistor, a collector terminal and a base terminal of said first transistor connected to a current source, a base terminal of said second transistor connected to the base terminal connected to the collector terminal of said second transistor through a branch of a differential stage which comprises a third transistor and fourth transistor, said third transistor and fourth transistor having a respective second resistor and third resistor arranged in series, and a divider means interposed between the second terminal of said at least one power transistor and the base terminals of said third transistor and fourth transistor.

A voltage/current characteristics control circuit for protecting at least one power transistor, said power transistor having at least first and second terminals, said circuit comprising

a first resistive means connected between said first terminal of said power transistor and a first supply voltage;
a first transistor having an emitter connected to said first terminal of said power transistor, a collector connected to a constant current source, and a base terminal connected to said collector terminal;
a second transistor having an emitter connected to said first supply voltage, a base connected to said base of said first transistor, and a collector;
first and second current paths connected in parallel to said collector of said second transistor;
a protection circuit in said first current path for turning off said one power transistor when current in said first current path exceeds a predetermined value;
and
means connected to said first and second current paths and to said second terminal of said one power transistor for dividing current through said second transistor between said first and second current paths responsive to voltage at said first terminal of said one power transistor;
whereby said one power transistor is protected from operating outside of its Safe Operating Area.

5 more elements

Dependencies are inferred from the claim text.

Voltage/current characteristics control circuit particularly for protecting power transistors

Life of this patent

Voltage/current characteristics control circuit particularly for protecting power transistors

Life of this patent

Abstract

Claims15