Short circuit protection apparatus for a regulated power supply

Claim 2

In a regulated power supply of the type in which a pair of transistors are arranged in a differential amplifier configuration to compare a substantially constant voltage with a voltage derived at an output terminal of said supply, in providing control signals to a third transistor in a direction to stabilize said output voltage at a predetermined level, the combination therewith of: means including a semi-conductor rectifier coupled between said output terminal and one of said pair of transistors to control it to render said third transistor non-conductive when the voltage provided at said output terminal is indicative of a short circuit condition of said power supply.

Claim 3

The combination of claim 1 wherein said means includes a semi-conductor rectifier biased to be nonconductive during normal operation of said power supply, but to be rendered conductive upon the occurrence of a short circuit to cause said one transistor to control said third transistor toward its non-conductive state.

Claim 4

In a regulated power supply, the combination comprising: first, second and third terminals; a first transistor having an input electrode coupled to said first terminal, an output electrode coupled to said second terminal, and a control electrode; second and third transistors, each also having input, output and control electrodes, with the output electrode of said second transistor being coupled to the control electrode of said first transistor; means for providing an unregulated direct current voltage to said first terminal; means for providing a substantially constant direct current voltage to the control electrode of said second transistor; means coupled intermediate said second and third terminals for providing a direct voltage to the control electrode of said third transistor for comparison with said substantially constant voltage to provide a control signal for the control electrode of said first transistor to stabilize the direct current voltage developed at said second terminal at a predetermined level; and means including a semi-conductor rectifier coupled between said output terminal and the control electrode of said second transistor to alter the conductivity condition of said second transistor in a direction to render said first transistor non-conductive when the voltage provided at said second terminal is indicative of a short circuit condition in said power supply.

Claim 5

In a regulated power supply, the combination comprising: first, second and third terminals; a first transistor having an input electrode coupled to said first terminal, an output electrode coupled to said second terminal, and a control electrode; second and third transistors, each also having input, output and control electrodes, with the output electrode of said second transistor being coupled to the control electrode of said first transistor; means for providing an unregulated direct current voltage to said first terminal; means for providing a substantially constant direct current voltage to the control electrode of said second transistor; means coupled intermediate said second and third terminals for providing a direct voltage to the control electrode of said third transistor for comparison with said substantially constant voltage to provide a control signal for the control electrode of said first transistor to stabilize the direct current voltage developed at said second terminal at a predetermined level; and means including a semi-conductor rectifier coupled between said output terminal and the control electrode of said second transistor to alter the conductivity condition of said second transistor in a direction to render said first transistor non-conductive when the voltage provided at said second terminal is indicative of a short circuit condition in said power supply.

Claim 6

In a regulated power supply, the combination comprising: first, second and third terminals; first, second and third transistors, each having emitter, base and collector electrodes; direct current connections from the emitter electrode of said first transisTor to said first terminal and from the collector electrode of said first transistor to said second terminal; a first resistor coupling the emitter electrodes of said second and third transistors to said third terminal; means adapted to provide an unregulated direct current voltage to said first terminal; first and second coupling paths between said second and third terminals, said first path including second and third resistors connected in series and said second path including a fourth resistor and a zener diode, also connected in series; direct current connections from the base electrode of said second transistor to the junction of said fourth resistor and said zener diode and from the base electrode of said third transistor to the junction of said second and third resistors; a fifth resistor coupling the collector electrode of said third transistor to said second output terminal; means coupling the collector electrode of said second transistor to the base electrode of said first transistor; and a semi-conductor rectifier coupled between said second terminal and the base electrode of said second transistor, biased to be nonconductive by said direct current voltage provided during normal operation of said power supply but to be rendered conductive upon the occurrence of a short circuit condition at said second terminal.

Claim 7

In a regulated power supply, the combination comprising: first, second and third terminals; first, second and third transistors, each having emitter, base and collector electrodes; direct current connections from the emitter electrode of said first transisTor to said first terminal and from the collector electrode of said first transistor to said second terminal; a first resistor coupling the emitter electrodes of said second and third transistors to said third terminal; means adapted to provide an unregulated direct current voltage to said first terminal; first and second coupling paths between said second and third terminals, said first path including second and third resistors connected in series and said second path including a fourth resistor and a zener diode, also connected in series; direct current connections from the base electrode of said second transistor to the junction of said fourth resistor and said zener diode and from the base electrode of said third transistor to the junction of said second and third resistors; a fifth resistor coupling the collector electrode of said third transistor to said second output terminal; means coupling the collector electrode of said second transistor to the base electrode of said first transistor; and a semi-conductor rectifier coupled between said second terminal and the base electrode of said second transistor, biased to be nonconductive by said direct current voltage provided during normal operation of said power supply but to be rendered conductive upon the occurrence of a short circuit condition at said second terminal.

Claim 8

The combination of claim 4 wherein said first transistor is of a conductivity type opposite from that of said second and third transistors.

Claim 9

The combination of claim 5 wherein said first transistor is of N-P-N conductivity type, wherein said second and third transistors are of P-N-P conductivity type, wherein the anode electrode of said zener diode and the cathode electrode of said semi-conductor rectifier are connected to the base electrode of said second transistor, and wherein the cathode electrode of said zener diode is connected to said third terminal.

Claim 10

The combination of claim 6 wherein there is further included a sixth resistor and a capacitor serially connected between said first and third terminals, the junction between which is directly connected to the base electrode of said second transistor.

Claim 11

The combination of claim 7 wherein said means coupling the collector electrode of said second transistor to the base electrode of said first transistor includes a second zener diode having its anode electrode connected to the base electrode of said first transistor.

Claim 12

The combination of claim 8 wherein said means adapted to provide a direct current voltage to the emitter electrode of said first transistor provides a negative direct voltage so as to bias said semi-conductor rectifier to be non-conductive during normal operation of said power supply, but with said semi-conductor rectifier arranged to be rendered conductive upon the occurrence of a short circuit at said second terminal.