High voltage transient protection circuit for voltage regulators

Claim 2

In combination with a voltage regulator of the type using an error amplifier to provide a constant output voltage and possessing an input terminal and a common terminal, and improved high voltage transient protection structure comprising: a first NPN transistor having an emitter, a collector and a base, a selected one of said first emitter and said first collector operatively connected to said common terminal; and means connected between said input terminal and said first base for biasing said first transistor into conduction in response to a voltage transient applied to said input terminal having a magnitude exceeding a selected value, whereby the magnitude of said constant output voltage from said voltage regulator is not increased during said voltage transient, said means including a second NPN type transistor having an emitter, a collector and a base, said second emitter connected to said first base; a third PNP type transistor having an emitter, a collector and a base, said third collector connected to said second base forming a first control node, said third base connected to said second collector; a first resistor connected between said first control node and said second emitter; a second resistor connected between said third emitter form a second control node thereat and said third base; and a plurality of zener diodes connected in series, anode to cathode, possessing an end anode terminal, an end cathode terminal and at least one intermediate diode connection terminal, said end anode terminal connected to said input terminal of said voltage regulator, said end cathode terminal connected to said first control node and a selected said at least one intermediate diode connection terminal connected to said second control node.

Claim 3

The improved high voltage transient protection structure of claim 1 wherein said plurality of zener diodes connected in series comprises: a fourth, a fifth, a sixth and a seventh NPN type transistor each having an emitter, a collector and a base, said fourth emitter connected to said fourth, fifth, sixth and seventh collectors to form said end anode terminal, said fourth base connected to said fifth emitter, said fifth base connected to said sixth emitter, said sixth base connected to said seventh emitter, forming said at least one intermediate diode connection terminal and said seventh base constituting said end cathode terminal.

Claim 4

The improved high voltage transient protection structure of claim 2 embodied as an integrated circuit in a chip of semiconductor material.

Claim 5

An improved shunt voltage regulator of the type possessing an input terminal, an output terminal and a common terminal with a shunt resistor connected across said input and said output terminals, a shunt transistor having an emitter, a collector and a base, said emitter and said collector operatively connected across said output and said common terminals in parallel with a voltage divider having an intermediate voltage tap, said base connected to the output of an error amplifier having one input connected to said intermediate voltage tap and another input connected to a voltage reference, wherein the improvement comprises: a first NPN transistor having an emitter, a collector and a base, said emitter and said collector of said first transistor operatively connected across said output terminal and said common terminal; and means connected between said input terminal and said base of said first transistor for biasing said first transistor into conduction in response to a voltage transient applied at said input terminal whose magnitude exceeds a selected value, whereby said output terminal is protectively coupled to said common terminal during said voltage transient, said means including a second NPN type transistor having an emitter, a collector and a base, said second emitter connected to said first base; a third PNP type transistor having an emitter, a collector and a base, said third collector connected to said second base forming a first control node, said third base connected to said second collector; a first resistor connected between said first control node and said second emitter; a second resistor connected between said third emitter forming a second control node thereat and said third base; and a plurality of zener diodes connected in series, anode to cathode, possessing an end anode terminal, an end cathode terminal and at least one intermediate diode connection terminal, said end anode terminal connected to said input terminal of said shunt voltage regulator, said end cathode terminal connected to said first control node and a selected said at least one intermediate diode connection terminal connected to said second control node.

Claim 6

An improved shunt voltage regulator of the type possessing an input terminal, an output terminal and a common terminal with a shunt resistor connected across said input and said output terminals, a shunt transistor having an emitter, a collector and a base, said emitter and said collector operatively connected across said output and said common terminals in parallel with a voltage divider having an intermediate voltage tap, said base connected to the output of an error amplifier having one input connected to said intermediate voltage tap and another input connected to a voltage reference, wherein the improvement comprises: a first NPN transistor having an emitter, a collector and a base, said emitter and said collector of said first transistor operatively connected across said output terminal and said common terminal; and means connected between said input terminal and said base of said first transistor for biasing said first transistor into conduction in response to a voltage transient applied at said input terminal whose magnitude exceeds a selected value, whereby said output terminal is protectively coupled to said common terminal during said voltage transient, said means including a second NPN type transistor having an emitter, a collector and a base, said second emitter connected to said first base; a third PNP type transistor having an emitter, a collector and a base, said third collector connected to said second base forming a first control node, said third base connected to said second collector; a first resistor connected between said first control node and said second emitter; a second resistor connected between said third emitter forming a second control node thereat and said third base; and a plurality of zener diodes connected in series, anode to cathode, possessing an end anode terminal, an end cathode terminal and at least one intermediate diode connection terminal, said end anode terminal connected to said input terminal of said shunt voltage regulator, said end cathode terminal connected to said first control node and a selected said at least one intermediate diode connection terminal connected to said second control node.

Claim 7

The improved shunt voltage regulator of claim 4 wherein said plurality of zener diodes connected in series comprises: a fourth, a fifth, a sixth and a seventh NPN type transistor each having an emitter, a collector and a base, said fourth emitter connected to said fourth, fifth, sixth and seventh collectors to form said end anode terminal, said fourth base connected to said fifth emitter, said fifth base connected to said sixth emitter, said sixth base connected to said seventh emitter forming said at least one intermediate diode connection terminal and said seventh base constituting said end cathode terminal.

Claim 8

The improved shunt voltage regulator of claim 5 embodied as an integrated circuit in a chip of semiconductor material.

Claim 9

An improved series pass voltage regulator of the type possessing an input terminal, an output terminal, a common terminal and a series pass transistor having an emitter, a collector and a base, said emitter and said collector operatively connected across said input and said output terminals, a voltage divider having an intermediate voltage tap connected across said output and said common terminals, a current source connected between said input terminal and said base, an error amplifier having an output connected to said base, one input connected to said intermediate voltage tap and another input connected to a voltage reference, wherein the improvement comprises: a first NPN transistor having an emitter, a collector and a base, said emitter and said collector of said first transistor operatively connected between said base of said series pass transistor and said common terminal; and means connected between said input terminal and said base of said first transistor for biasing said first transistor into conduction in response to a voltage transient applied at said input terminal whose magnitude exceeds a selected value, whereby said base of said series pass transistor is protectively coupled to said common terminal during said voltage transient, said means including a second NPN type transistor having an emitter, a collector and a base, said second emitter connected to said first base; a third PNP type transistor having an emitter, a collector and a base, said third collector connected to said second base forming a first control node, said third base connected to said second collector; a first resistor connected between said first control node and said second emitter; a second resistor connected between said third emitter forming a second control node thereat and said third base; and a plurality of zener diodes connected in series, anode to cathode, possessing an end anode terminal, an end cathode terminal and at least one intermediate diode connection terminal, said end anode terminal connected to said input terminal of said series pass voltage regulator, said end cathode connected to said first control node and a selected said at least one intermediate diode connection terminal connected to said second control node.

Claim 10

An improved series pass voltage regulator of the type possessing an input terminal, an output terminal, a common terminal and a series pass transistor having an emitter, a collector and a base, said emitter and said collector operatively connected across said input and said output terminals, a voltage divider having an intermediate voltage tap connected across said output and said common terminals, a current source connected between said input terminal and said base, an error amplifier having an output connected to said base, one input connected to said intermediate voltage tap and another input connected to a voltage reference, wherein the improvement comprises: a first NPN transistor having an emitter, a collector and a base, said emitter and said collector of said first transistor operatively connected between said base of said series pass transistor and said common terminal; and means connected between said input terminal and said base of said first transistor for biasing said first transistor into conduction in response to a voltage transient applied at said input terminal whose magnitude exceeds a selected value, whereby said base of said series pass transistor is protectively coupled to said common terminal during said voltage transient, said means including a second NPN type transistor having an emitter, a collector and a base, said second emitter connected to said first base; a third PNP type transistor having an emitter, a collector and a base, said third collector connected to said second base forming a first control node, said third base connected to said second collector; a first resistor connected between said first control node and said second emitter; a second resistor connected between said third emitter forming a second control node thereat and said third base; and a plurality of zener diodes connected in series, anode to cathode, possessing an end anode terminal, an end cathode terminal and at least one intermediate diode connection terminal, said end anode terminal connected to said input terminal of said series pass voltage regulator, said end cathode connected to said first control node and a selected said at least one intermediate diode connection terminal connected to said second control node.

Claim 11

The improved series pass voltage regulator of claim 7 wherein said plurality of zener diodes connected in series comprises: a fourth, a fifth, a sixth and a seventh NPN type transistor each having an emitter, a collector and a base, said fourth emitter connected to said fourth, fifth, sixth and seventh collectors to form said end anode terminal, said fourth base connected to said fifth emitter, said fifth base connected to said sixth emitter, said sixth base connected to said seventh emitter forming said at least one intermediate diode connection terminal and said seventh base constituting said end cathode terminal.

Claim 12

The improved series pass voltage regulator of claim 8 embodied as an integrated circuit in a chip of semiconductor material.