Protective means for transistorized load circuit

Claim 2

An electric circuit, comprising a power transistor having a base electrode, emitter electrode and a collector electrode, a load circuit including an electrical load, said emitter electrode and said collector electrode being in series circuit with said load circuit, a multivibrator electrically connected to said base electrode and effective for cyclically producing and applying a timed electrical signal thereto in order to bias said power transistor into conduction thereby completing said load circuit through said emitter and collector electrodes, and means sensitive to an occurencE of an abnormally high current flow through said load circuit as occassioned by a short circuiting of said load for enabling said multivibrator to continue cyclic generation of said timed electrical signal while preventing the application of said timed electrical signal to said base electrode thereby rendering said power transistor nonconductive.

Claim 3

An electric circuit according to claim 1, wherein said means sensitive to an abnormally high current flow comprises normally closed switching means in series circuit with said multivibrator and said base electrode, said switching means being actuated to an electrically open condition upon the occurence of said abnormally high current flow.

Claim 4

An electric circuit according to claim 2, wherein said normally closed switching means comprises a mechanical switch member positionable into either of two positions one of which permits said signal generating means to apply said electrical signal to said power transistor in order to drive said transistor into conduction.

Claim 5

An electric circuit according to claim 1, wherein said means sensitive to an abnormally high current flow comprises normally electrically closed switching means in series circuit with said multivibrator and said base electrode, and electrical inductance means effective for causing said switching means to be inductively actuated to an electrically open condition upon the occurence of said abnormally high current flow.

Claim 6

An electric circuit according to claim 4, wherein said switching means comprises a reed switch.

Claim 7

An electric circuit according to claim 1, wherein said multivibrator comprises a first transistor, a second transistor, said second transistor having an emitter-collector circuit and a base electrode, said emitter-collector circuit of said second transistor being in series circuit with said base electrode of said power transistor, and wherein said means sensitive to an abnormally high current flow comprises normally closed switching means in series circuit with and between said emitter-collector circuit of said second transistor and said base electrode of said power transistor.

Claim 8

An electric circuit according to claim 6 wherein said means sensitive to an abnormally high current flow also comprises a coil serially situated in said load circuit and effective upon the occurrence of said abnormally high current flow to actuate said switching means to an electrically open condition.

Claim 9

An electrical circuit, comprising a power transistor having a base electrode, emitter electrode, a load circuit including an electrical load, said emitter electrode and said collector electrode being in series circuit with said load circuit, electrical signal generating means electrically connected to said base electrode and effective for producing and applying an electrical signal thereto in order to bias said power transistor into conduction thereby completing said load circuit through said emitter and collector electrodes, and means sensitive to an occurence of an abnormally high current flow through said load circuit as occassioned by a short circuiting of said load for eliminating said bias thereby rendering said power transistor nonconductive, a second transistor having it emitter-collector circuit serially connected between said electrical signal generating means and said base electrode of said power transistor, and said means sensitive to an abnormally high current flow comprising a diode electrically connected at one end to a base electrode of said second transistor and electrically connected at its other end to said load circuit at a point which is on the same side of said power transistor as is said load, said diode being polarized to become conductive upon occurrence of said abnormally high current flow.

Claim 10

An electrical circuit, comprising a power transistor having a base electrode, emitter electrode, a load circuit including an electrical load, said emitter electrode and said collector electrode being in series circuit with said load circuit, electrical signal generating means electrically connected to said base electrode and effective for producing and applying an electrical signal thereto in order to bias said power transistor into conduction thereby completing said load circuit through said emitter and collector electrodes, and means sensitive to an occurence of an abnormally high current flow through said load circuit as occassioned by a short circuiting of said load for eliminating said bias thereby rendering said power transistor nonconductive, a second transistor having it emitter-collector circuit serially connected between said electrical signal generating means and said base electrode of said power transistor, and said means sensitive to an abnormally high current flow comprising a diode electrically connected at one end to a base electrode of said second transistor and electrically connected at its other end to said load circuit at a point which is on the same side of said power transistor as is said load, said diode being polarized to become conductive upon occurrence of said abnormally high current flow.

Claim 11

In a transistorized switching circuit such as used in flashers for automotive vehicles, the combination including a transistor free-running multivibrator circuit means, a load circuit, a load switching transistor connecting in sAid load circuit, means connecting an output of said multivibrator circuit means with a control electrode of said load switching transistor in order to cyclically produce and apply a timed electrical signal in said load switching transistor thereby to effect intermittent operation of said switching transistor, and protective means connected to said control element for enabling said multivibrator to continue cyclic production of said timed electrical signal while preventing the application of said timed electrical signal to said control electrode thereby rendering said switching transistor nonconductive upon the occurrence of short in said load circuit.

Claim 12

In a transistorized switching circuit such as used in flashers for automotive vehicles, the combination including a transistor free-running multivibrator circuit means, a load circuit, a load switching transistor connecting in sAid load circuit, means connecting an output of said multivibrator circuit means with a control electrode of said load switching transistor in order to cyclically produce and apply a timed electrical signal in said load switching transistor thereby to effect intermittent operation of said switching transistor, and protective means connected to said control element for enabling said multivibrator to continue cyclic production of said timed electrical signal while preventing the application of said timed electrical signal to said control electrode thereby rendering said switching transistor nonconductive upon the occurrence of short in said load circuit.

Claim 13

A combination as defined in claim 9 in which said protective means includes a normally closed switch member serially connected in the circuit to said control element of the load switching transistor, and a coil for operating said switch member connected in said load circuit, the pull of said coil being insufficient to open said switch member except under short circuit condition.

Claim 14

In a transistorized switching circuit such as used in flashers for automotive vehicles, the combination including a two transistor multivibrator circuit means, a load circuit, a load switching transistor connected in said load circuit, means connecting said multivibrator circuit means with a control electrode of said load switching transistor thereby to effect an intermittent operation of the switching transistor, protective means connected to said control element for rendering said switching transistor nonconductive upon the occurence of a short in said load circuit, said protective means including a transistor connected in the circuit to said control element of the load switching transistor, and a diode connected to a control element of said last named transistor and to said load circuit on the far side of said switching transistor, said diode being polarized to become conductive upon occurence of a short in the load circuit.

Claim 15

In a transistorized switching circuit such as used in flashers for automotive vehicles, the combination including a two transistor multivibrator circuit means, a load circuit, a load switching transistor connected in said load circuit, means connecting said multivibrator circuit means with a control electrode of said load switching transistor thereby to effect an intermittent operation of the switching transistor, protective means connected to said control element for rendering said switching transistor nonconductive upon the occurence of a short in said load circuit, said protective means including a transistor connected in the circuit to said control element of the load switching transistor, and a diode connected to a control element of said last named transistor and to said load circuit on the far side of said switching transistor, said diode being polarized to become conductive upon occurence of a short in the load circuit.

Claim 16

A combination as defined in claim 11 in which said diode is connected to the intermediate point of a voltage divider connected to the control element of said last named transistor.

Claim 17

A combination as defined in claim 11 wherein said multivibrator circuit means includes at least one capacitor means, and a second diode is connected to said capacitor means and to said control element of said load switching transistor, said second diode being polarized to be conductive during nonconductive periods of the load switching transistor.

Claim 18

A combination as defined in claim 11 wherein said multivibrator circuit means includes a pair of capacitor means, and each of said capacitor means is connected to said control element of said load switching transistor through a diode means, said last named diode means being polarized to be conductive during nonconductive periods of the load switching transistor.

Claim 19

A combination as defined in claim 14 in which a capacitance-resistance network is connected to said last named diode means thereby to filter the diode circuit while providing for return of the load circuit to normal operating condition by discharge of said capacitance through said resistance.

Claim 20

In a transistorized switching circuit, such as used for automotive vehicles, the combination including first means for producing an intermittent electrical signal, a load circuit including an electrical load, a load switching transistor connected in said load circuit, circuit means for connecting said first means with a control electrode of said load switching transistor in order to apply thereto said intermittent electrical signal and thereby to effect intermittent operation of said switching transistor, protective means connected to said control element for rendering said switching transistor nonconductive upon the occurence of an abnormally high current flow in said load circuit as occassioned by a short circuit in said load circuit, said protective means comprising a second transistor connected in said circuit means to said control element of the load switching transistor, and a diode connected to a control element of said second transistor and to said load circuit on the same side of said switching transistor as is the said load, said diode being polarized to become conductive upon occurrence of short circuit conditions in said load circuit.

Claim 21

In a transistorized switching circuit, such as used for automotive vehicles, the combination including first means for producing an intermittent electrical signal, a load circuit including an electrical load, a load switching transistor connected in said load circuit, circuit means for connecting said first means with a control electrode of said load switching transistor in order to apply thereto said intermittent electrical signal and thereby to effect intermittent operation of said switching transistor, protective means connected to said control element for rendering said switching transistor nonconductive upon the occurence of an abnormally high current flow in said load circuit as occassioned by a short circuit in said load circuit, said protective means comprising a second transistor connected in said circuit means to said control element of the load switching transistor, and a diode connected to a control element of said second transistor and to said load circuit on the same side of said switching transistor as is the said load, said diode being polarized to become conductive upon occurrence of short circuit conditions in said load circuit.

Claim 22

A transistorized switching circuit according to claim 16 wherein said diode is connected to an intermediate point of a voltage divider connected to the control element of said second transistor.