Overvoltage protection circuit

Claim 2

An overvoltage protection circuit for a circuit array comprised of one or more semiconductor devices each having anode, cathode and gate electrodes, said array being connected intermediate a source of electrical power and a load and serving, upon the application of gating pulses to the gate electrodes, to deliver electrical power from the source to the load, said overvoltage protection circuit comprising: (a) means to provide a unidirectional current proportional to the instantaneous voltage across the array; (b) change storage means responsive to said unidirectional current to develop an electrical charge of a predetermined magnitude; (c) means responsive to said unidirectional current to develop a signal proportional to the instantaneous voltage across the array; and, (d) switch means, responsive to said signal, operative to discharge said charge storage means to thereby develop a firing signal for rendering each device of the array conductive.

Claim 3

The invention in accordance with claim 1 wherein said charge storage means includes a capacitor.

Claim 4

The invention in accordance with claim 2 wherein said switch means includes; (a) a cascade arrangement of first, second and third transistors; (b) diode means having a predetermined reverse breakdown voltage connecting said signal developing means to said first transistor to thereby render it conductive in response to said signal; (c) means interconnecting said first, second and third transistors whereby said second and third transistors are rendered conductive in response to the conduction of said first transistor; and, (d) latch circuit means innerconnecting said second and third transistors to provide a holding current to said third transistor.

Claim 5

An overvoltage protection circuit for a circuit array comprised of one or more semiconductor devices each having anode, cathode and gate electrodes, said array being connected intermediate a source of electrical power and a load and serving, upon the application of gating pulses to the gate electrodes, to deliver electrical power from the source to the load, said overvoltage protection circuit comprising: (a) means connected across said circuit array for providing a unidirectional current as a result of the instantaneous voltage existing across the circuit array by virtue of the array's connection to the source of power; (b) charge storage means; (c) means for delivering said current to such charge storage mean whereby an electrical charge is developed and stored therein; (d) means for limiting the magnitude of said electrical charge; (e) signal developing means responsive to said current to develop a signal proportional thereto; and, (f) switch means responsive to a predetermined magnitude of said signal for discharging said charge storage means to thereby generate a gating signal for application to the gate electrodes of each semiconductor device of the array to thereby render each such device capable of conduction.

Claim 6

An overvoltage protection circuit for a circuit array comprised of one or more semiconductor devices each having anode, cathode and gate electrodes, said array being connected intermediate a source of electrical power and a load and serving, upon the application of gating pulses to the gate electrodes, to deliver electrical power from the source to the load, said overvoltage protection circuit comprising: (a) means connected across said circuit array for providing a unidirectional current as a result of the instantaneous voltage existing across the circuit array by virtue of the array's connection to the source of power; (b) charge storage means; (c) means for delivering said current to such charge storage mean whereby an electrical charge is developed and stored therein; (d) means for limiting the magnitude of said electrical charge; (e) signal developing means responsive to said current to develop a signal proportional thereto; and, (f) switch means responsive to a predetermined magnitude of said signal for discharging said charge storage means to thereby generate a gating signal for application to the gate electrodes of each semiconductor device of the array to thereby render each such device capable of conduction.

Claim 7

The invention in accordance with claim 4 wherein said means for limiting the magnitude for said charge includes a diode having a predetermined reverse breakdown voltage connected in a basically parallel relationship with said capacitor.

Claim 8

The invention in accordance with claim 5 wherein said diode is a Zener diode.

Claim 9

The invention in accordance with claim 5 wherein said signal developing means comprises resistive means connected in series with said diode.

Claim 10

An overvoltage protection circuit for a plurality of series connected semiconductor devices comprising: (a) means to provide a unidirectional current proportional to the instantaneous voltage across the series connected semiconductor devices; (b) means including charge storage means responsive to said unidirectional current to develop a charge of a predetermined magnitude; (c) means responsive to said unidirectional current to develop a control signal proportional to the instantaneous voltage across the semiconductor devices; and, (d) switch means responsive to said control signal operative to discharge said charge storage means to thereby develop a firing signal for rendering each of said semiconductor devices conductive.

Claim 11

An overvoltage protection circuit for a plurality of series connected semiconductor devices comprising: (a) means to provide a unidirectional current proportional to the instantaneous voltage across the series connected semiconductor devices; (b) means including charge storage means responsive to said unidirectional current to develop a charge of a predetermined magnitude; (c) means responsive to said unidirectional current to develop a control signal proportional to the instantaneous voltage across the semiconductor devices; and, (d) switch means responsive to said control signal operative to discharge said charge storage means to thereby develop a firing signal for rendering each of said semiconductor devices conductive.

Claim 12

An overvoltage protection circuit for a plurality of series connected semiconductor devices, each having a gate electrode, adapted to be rendered conductive by single firing pulse operative to apply simultaneous gating pulses to the individual gate electrodes of the semiconductor devices comprising: (a) means to provide a unidirectional current proportional to the instantaneous voltage across the series connected semiconductor devices; (b) charge storage means responsive to said unidirectional current to develop an electrical charge of a predetermined magnitude; (c) means responsive to said unidirectional current to develop a control signal proportional to the instantaneous voltage across the semiconductor devices; and, (d) switch means, responsive to said control signal, operative to discharge said charge storage means to thereby develop a firing signal for rendering of said semiconductor devices conductive.

Claim 13

An overvoltage protection circuit for a plurality of series connected semiconductor devices, each having a gate electrode, adapted to be rendered conductive by single firing pulse operative to apply simultaneous gating pulses to the individual gate electrodes of the semiconductor devices comprising: (a) means to provide a unidirectional current proportional to the instantaneous voltage across the series connected semiconductor devices; (b) charge storage means responsive to said unidirectional current to develop an electrical charge of a predetermined magnitude; (c) means responsive to said unidirectional current to develop a control signal proportional to the instantaneous voltage across the semiconductor devices; and, (d) switch means, responsive to said control signal, operative to discharge said charge storage means to thereby develop a firing signal for rendering of said semiconductor devices conductive.