Overvoltage protection circuit

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.

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.

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.