Transient voltage protection circuit

Claim 2

A transient voltage protection circuit for protecting electronic devices connected across a DC voltage source from transient voltages, comprising voltage-transient sensing means for sensing a transient voltage above a predetermined magnitude and loading means having an inactive high impedance, nonconductive state and an active low impedance, conductive state connected across said source, and control means responsive to said sensing means for switching said loading means into its active state to effect loading of the transient voltage when said transient voltage exceeds said predetermined magnitude so as to reduce the peak amplitude of said transient voltage, said loading means being constructed to load said transient voltage until after said transient voltage has been dissipated, and current limiting means connected in series with both said loading means and said control means across said DC voltage source.

Claim 3

A transient voltage protection circuit for protecting electronic devices as defined in claim 1 wherein said loading means includes at least one transistor that has its collector-emitter path coupled in series with said current limiting means in a loading path across the DC voltage source.

Claim 4

A transient voltage protection circuit for protecting electronic devices as defined in claim 1 wherein the voltage-transient sensing means is a voltage-breakdown device having a quiescent high impedance, nonconductive state so that no appreciable quiescent current flows through the protection circuit, said voltage breakdown means being switched to a low impedance, conductive state when said transient voltage exceeds said predetermined magnitude.

Claim 5

A transient voltage protection circuit for protecting electronic devices as defined in claim 3 wherein said loading means includes at least one transistor that has its collector-emitter path coupled in series with said current limiting means in a loading path across the DC voltagE source.

Claim 6

A transient voltage protection circuit for protecting electronic devices connected across a DC voltage source from transient voltage, comprising voltage-transient sensing means for sensing a transient voltage above a predetermined magnitude, and circuit means connected across said DC voltage source, said circuit means comprising control means controlled by said sensing means for developing a control signal when the transient voltage exceeds said predetermined magnitude and loading means having an inactive high impedance, nonconductive state and an active low impedance, conductive state, said loading means being switched into its active state in response to a said control signal to effect loading of a transient voltage by the said loading means when said transient voltage exceeds said predetermined magnitude so as to reduce its peak amplitude, said control means and said loading means being constructed to load said transient voltage until after said transient voltage has been dissipated, and current limiting means connected in series with both said loading means and said control means across said DC voltage source.

Claim 7

A transient voltage protection circuit for protecting electronic devices connected across a DC voltage source from transient voltage, comprising voltage-transient sensing means for sensing a transient voltage above a predetermined magnitude, and circuit means connected across said DC voltage source, said circuit means comprising control means controlled by said sensing means for developing a control signal when the transient voltage exceeds said predetermined magnitude and loading means having an inactive high impedance, nonconductive state and an active low impedance, conductive state, said loading means being switched into its active state in response to a said control signal to effect loading of a transient voltage by the said loading means when said transient voltage exceeds said predetermined magnitude so as to reduce its peak amplitude, said control means and said loading means being constructed to load said transient voltage until after said transient voltage has been dissipated, and current limiting means connected in series with both said loading means and said control means across said DC voltage source.

Claim 8

A transient voltage protection circuit for protecting electronic devices as defined in claim 5 wherein said loading means includes at least one transistor that has its collector-emitter path coupled in a loading path in series with said current limiting means across the DC voltage source.

Claim 9

A transient voltage protection circuit for protecting electronic devices as defined in claim 5 wherein the voltage-transient sensing means is a voltage breakdown device so that no quiescent current flows through the protection circuit, said voltage breakdown means being switched to a low impedance, conductive state when said transient voltage exceeds said predetermined magnitude.

Claim 10

A transient voltage protection circuit for protecting electronic devices as defined in claim 7 wherein said loading means includes at least one transistor that has its collector-emitter path coupled in a loading path in series with said current limiting means across the DC voltage source.

Claim 11

A transient voltage protection circuit for protecting electronic devices as defined in claim 7 wherein the voltage breakdown device is a two-terminal device and the control means is a transistor which has its base connected to one terminal of the voltage breakdown device and its collector connected to the other terminal of the voltage breakdown device.

Claim 12

A transient voltage protection circuit for protecting electronic devices as defined in claim 9 wherein said loading means includes at least one transistor that has its collector-emitter path coupled in series with said current limiting means in a loading path across the DC voltage source and its base coupled to the emitter of the control transistor.

Claim 13

A transient voltage protection circuit for protecting electronic devices across a DC voltage source having a first terminal and a second terminal, comprising a first resistance element connected to the first terminal of the voltage source, a control transistor having its collector-emitter path coupled in series with the first resistance element, a second resistance element connected between the emitter of the control transistor and the second terminal of the voltage source, a two-terminal voltage breakdown device connected between the collector and the base of the control transistor; and at least one loading transistor having its collector connected to the collector of the control transistor and having its collector emitter path in series with said first resistance, its emitter connected to the second terminal of the DC voltage source and its base coupled through a low resistance path to the emitter of the control transistor; the voltage breakdown device, the control transistor and the loading transistors all having an inactive high impedance, nonconductive state and an active low impedance, conductive state and all being switched into their active states to effect tHe loading of a transient voltage across said first and second terminals which exceeds said predetermined magnitude so as to reduce the peak amplitude of said transient voltage; said voltage breakdown means, said control transistor and said loading transistor all being constructed to load said transient voltage until after said transient voltage has been dissipated.

Claim 14

A transient voltage protection circuit for protecting electronic devices across a DC voltage source having a first terminal and a second terminal, comprising a first resistance element connected to the first terminal of the voltage source, a control transistor having its collector-emitter path coupled in series with the first resistance element, a second resistance element connected between the emitter of the control transistor and the second terminal of the voltage source, a two-terminal voltage breakdown device connected between the collector and the base of the control transistor; and at least one loading transistor having its collector connected to the collector of the control transistor and having its collector emitter path in series with said first resistance, its emitter connected to the second terminal of the DC voltage source and its base coupled through a low resistance path to the emitter of the control transistor; the voltage breakdown device, the control transistor and the loading transistors all having an inactive high impedance, nonconductive state and an active low impedance, conductive state and all being switched into their active states to effect tHe loading of a transient voltage across said first and second terminals which exceeds said predetermined magnitude so as to reduce the peak amplitude of said transient voltage; said voltage breakdown means, said control transistor and said loading transistor all being constructed to load said transient voltage until after said transient voltage has been dissipated.

Claim 15

A transient voltage protection circuit for protecting electronic devices as defined in claim 11 wherein the voltage breakdown means is a Zener diode.

Claim 16

A transient voltage protection circuit for protecting electronic devices as defined in claim 11 wherein two or more loading transistors are coupled in parallel with each other and have their bases coupled to the emitter of the control transistor through equalizing resistors.

Claim 17

A transient voltage protection circuit for protecting electronic devices as defined in claim 13 wherein the voltage breakdown means is a Zener diode.

Claim 18

A transient voltage protection circuit for protecting electronic devices connected across a DC voltage source from transient voltages, comprising voltage transient sensing means for sensing a transient voltage above a predetermined magnitude, current limiting means, and loading circuit means including semiconductor switch means, said current limiting means being connected in series with both said switch means and said sensing means across said DC voltage source, said switch means exhibiting the characteristic of having a normal nonconductive high impedance condition and a conductive low impedance condition when said sensing means senses a said transient voltage to thereby load said transient voltage until after said transient voltage has been dissipated.

Claim 19

A transient voltage protection circuit for protecting electronic devices connected across a DC voltage source from transient voltages, comprising voltage transient sensing means for sensing a transient voltage above a predetermined magnitude, current limiting means, and loading circuit means including semiconductor switch means, said current limiting means being connected in series with both said switch means and said sensing means across said DC voltage source, said switch means exhibiting the characteristic of having a normal nonconductive high impedance condition and a conductive low impedance condition when said sensing means senses a said transient voltage to thereby load said transient voltage until after said transient voltage has been dissipated.