US3886432A — Overvoltage protective circuit for high power thy…

Claim 1

Independent Claim 142 words

For triggering a high-power thyristor, a circuit including overvoltage sensing means connected in series with energy storing means between main terminals of the thyristor and means for coupling the juncture of said sensing means and said energy storing means to the control means of the thyristor, whereby the thyristor is triggered when said sensing means switches from a blocking state to a current conducting state in response to forward bias voltage across said main electrodes rising to a predetermined threshold magnitude, said sensing means comprising a plurality of PNPN semiconductor elements connected in series with at least one PN semiconductor element and poled to conduct current in the same direction as said thyristor, wherein the improvement comprises at least two resistors connected across said PNPN and PN elements, respectively, so as to divide therebetween any reverse voltage appearing across said main electrodes.

Claim 2

Dependent Claim 142 words

For triggering a high-power thyristor, a circuit including overvoltage sensing means connected in series with energy storing means between main terminals of the thyristor and means for coupling the juncture of said sensing means and said energy storing means to the control means of the thyristor, whereby the thyristor is triggered when said sensing means switches from a blocking state to a current conducting state in response to forward bias voltage across said main electrodes rising to a predetermined threshold magnitude, said sensing means comprising a plurality of PNPN semiconductor elements connected in series with at least one PN semiconductor element and poled to conduct current in the same direction as said thyristor, wherein the improvement comprises at least two resistors connected across said PNPN and PN elements, respectively, so as to divide therebetween any reverse voltage appearing across said main electrodes.

Claim 3

Dependent Claim 66 words

The circuit of claim 1 wherein said overvoltage sensing means comprises a plurality of PNPN elements and a plurality of PN elements interconnected in series with one another, and wherein the resistance values of said resistors are selected so that the reverse voltage across said PN elements is substantially within a range between 20 and 80 percent of the total reverse voltage across said main electrodes.

Claim 4

Dependent Claim 30 words

The circuit of claim 1 wherein said overvoltage sensing means includes means for limiting the increase in said threshold magnitude of forward bias voltage with increasing rates of rise thereof.

Claim 5

Dependent Claim 27 words

The circuit of claim 1 wherein said coupling means comprises an isolating diode poled in agreement with said semiconductor elements and a resistor connected across said diode.

Claim 6

Dependent Claim 117 words

For triggering a high-power thyristor, a circuit including overvoltage sensing means connected in series with a capacitor between main terminals of the thyristor and means for coupling the juncture of said sensing means and said capacitor to the control means of the thyristor, whereby the thyristor is triggered when said sensing means switches from a blocking state to a current conducting state in response to forward bias voltage across said main electrodes rising to a predetermined threshold magnitude which is lower than the breakover level of said main thyristor, wherein the improvement comprises means associated with said overvoltage sensing means for relatively reducing said threshold magnitude of forward bias voltage as the rate of rise thereof increases.

Claim 7

Dependent Claim 117 words

For triggering a high-power thyristor, a circuit including overvoltage sensing means connected in series with a capacitor between main terminals of the thyristor and means for coupling the juncture of said sensing means and said capacitor to the control means of the thyristor, whereby the thyristor is triggered when said sensing means switches from a blocking state to a current conducting state in response to forward bias voltage across said main electrodes rising to a predetermined threshold magnitude which is lower than the breakover level of said main thyristor, wherein the improvement comprises means associated with said overvoltage sensing means for relatively reducing said threshold magnitude of forward bias voltage as the rate of rise thereof increases.

Claim 8

Dependent Claim 78 words

The circuit of claim 5 wherein said overvoltage sensing means comprises a plurality of PNPN semi-conductor elements connected in series with one another and poled to conduct current in the same direction as said thyristor, and wherein said threshold magnitude reducing means comprises a capacitor connected across a first one of said elements and having a capacitive value such that said first element and at least another one of said elements have unequal magnitudes of capacitance associated therewith.

Claim 9

Dependent Claim 83 words

The circuit of claim 5 wherein said overvoltage sensing means comprises a plurality of auxiliary thyristors interconnected in series with one another and poled to conduct current in the same direction as said high-power thyristor, said auxiliary thyristors being arranged to turn on in a voltage breakover mode in response to said forward bias voltage attaining said threshold magnitude, and wherein said threshold magnitude reducing means comprises a capacitor connected between the anode and the gate electrode of one of said auxiliary thyristors.

Claim 10

Dependent Claim 179 words

For protecting a main thyristor having an anode, a cathode, and control means, a circuit including overvoltage sensing means connected in series with energy storing means between said anode and said cathode and means for coupling the juncture of said sensing means and said energy storing means to said control means, whereby the main thyristor is triggered when said sensing means switches from a blocking state to a current conducting state in response to forward bias voltage across said thyristor rising to a predetermined threshold magnitude, said sensing means comprising a plurality of serially interconnected PNPN semi-conductor elements which are poled in the same direction as said main thyristor and which have preselected forward breakover voltage values the sum of which exceeds said threshold magnitude, wherein the improvement comprises a plurality of resistors connected across said PNPN elements, respectively, the relative ohmic values of said resistors being so selected that the voltage across at least one of said elements will attain the breakover value of the corresponding element whenever said forward bias voltage rises to said predetermined threshold magnitude.

Claim 11

Dependent Claim 179 words

For protecting a main thyristor having an anode, a cathode, and control means, a circuit including overvoltage sensing means connected in series with energy storing means between said anode and said cathode and means for coupling the juncture of said sensing means and said energy storing means to said control means, whereby the main thyristor is triggered when said sensing means switches from a blocking state to a current conducting state in response to forward bias voltage across said thyristor rising to a predetermined threshold magnitude, said sensing means comprising a plurality of serially interconnected PNPN semi-conductor elements which are poled in the same direction as said main thyristor and which have preselected forward breakover voltage values the sum of which exceeds said threshold magnitude, wherein the improvement comprises a plurality of resistors connected across said PNPN elements, respectively, the relative ohmic values of said resistors being so selected that the voltage across at least one of said elements will attain the breakover value of the corresponding element whenever said forward bias voltage rises to said predetermined threshold magnitude.

Claim 12

Dependent Claim 57 words

The circuit of claim 8 in which said overvoltage sensing means further comprises at least one PN semiconductor element connected in series and in polarity agreement with said PNPN elements and a resistor connected across said PN element to form with said plurality of resistors a voltage divider for any reverse voltage impressed across said sensing means.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1978-05-26	1978-11-25	1979-05-27	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1982-05-26	1982-11-25	1983-05-27	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	1986-05-26	1986-11-25	1987-05-27	$7700.00	Window Closed / Lapsed

Overvoltage protective circuit for high power thyristors

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