Protection circuit with simultaneous voltage and current sensing means

Claim 2

An electrical circuit having short circuit and overload protection, said circuit comprising an electrical component to be protected, input means for supplying an input signal to said electrical component, sensing means connected to said electrical component for separately sensing the current through and the voltage across said electrical component and for supplying first and second outputs in response to said current and voltage respectively, integrating and combining means connected to said sensing means for integrating with respect to time and combining said outputs to produce a control signal which is representative at all times of the current through and the voltage across said electrical component, shunting means for shunting at least a portion of said input signal away from said electrical component and control means responsive to said control signal for operating said shunting means when said control signal is at a predetermined level whereby said protection circuit maintains a steady state, operating range of said electrical component within acceptable limits.

Claim 3

An electrical circuit as in claim 1, wherein said electrical component is an amplifying device.

Claim 4

An electrical circuit as in claim 1, wherein said electrical component is a transistor.

Claim 5

An electrical circuit as in claim 1, wherein the integrating and combining means further includes control means for providing said control signal corresponding to the differential of the thus integrated first and second outputs.

Claim 6

A electrical circuit as in claim 1, wherein said predetermined level of the control signal is a function of the duration and amplitude of current and voltage that said electrical component may safely tolerate.

Claim 7

A electrical circuit as in claim 1, wherein said means for integrating and combining said outputs includes means for combining the thus separately integrated outputs.

Claim 8

A electrical circuit as in claim 1, wherein said sensing and supplying means includes rectifier means for rectifying said outputs.

Claim 9

A transistorized amplifier circuit having short circuit and overload protection, said amplifier circuit comprising at least one transistor, to be protected, input means for supplying an input signal to said amplifier, sensing means connected to said transistor for sensing its operation, said sensing means being responsive to said operation and supplying a first output corresponding to the current flow in said transistor and a second output corresPonding to the voltage across said transistor, integrating means connected to the sensing means for integrating with respect to time each of said first and second outputs, control means connected to said integrating means for providing a control signal output corresponding to the differential of the thus integrated first and second outputs, gate means connected across the input of said amplifier and adapted to shunt at least a portion of said input signal from said amplifier, said gate means being operated by said control signal and arranged to shunt said input when said control signal has a predetermined value corresponding to essentially the maximum duration and amplitude of current and voltage that said transistor may safely tolerate whereby said amplifier is not protected against very large instantaneous currents and voltages of short duration but having amplitude values beyond safe permissible levels.

Claim 10

A transistorized amplifier circuit having short circuit and overload protection, said amplifier circuit comprising at least one transistor, to be protected, input means for supplying an input signal to said amplifier, sensing means connected to said transistor for sensing its operation, said sensing means being responsive to said operation and supplying a first output corresponding to the current flow in said transistor and a second output corresPonding to the voltage across said transistor, integrating means connected to the sensing means for integrating with respect to time each of said first and second outputs, control means connected to said integrating means for providing a control signal output corresponding to the differential of the thus integrated first and second outputs, gate means connected across the input of said amplifier and adapted to shunt at least a portion of said input signal from said amplifier, said gate means being operated by said control signal and arranged to shunt said input when said control signal has a predetermined value corresponding to essentially the maximum duration and amplitude of current and voltage that said transistor may safely tolerate whereby said amplifier is not protected against very large instantaneous currents and voltages of short duration but having amplitude values beyond safe permissible levels.

Claim 11

An amplifier as in claim 8, wherein said transistor includes base, collector and emitter electrodes, and wherein an output load of the amplifier is connected across the collector and emitter electrodes, and said sensing means includes a first impedance means connected between said emitter electrode and a circuit reference point to measure the current flow through the emitter electrode and a second impedance means connected to said load to measure the voltage from the output load to a circuit reference point in said amplifier.

Claim 12

An amplifier as in claim 8, wherein said sensing and supplying means includes rectifier means for rectifying said outputs.

Claim 13

An amplifier as in claim 10, wherein said rectifier means includes first means for rectifying the voltage drops across said impedance means and said integrating means includes capacitor means connected across the output of said first rectifying means and said reference point.

Claim 14

An amplifier as in claim 11, wherein said rectifier means includes second means for rectifying with respect of said reference point the voltage across an output load and said integrating means includes capacitor means connected across the output of said second rectifying means and said reference point.

Claim 15

An amplifier as in claim 12, wherein said gate means includes a switching transistor having base, collector and emitter electrodes, the collector and emitter electrodes being connected to the input of said amplifier and said reference point, and said control means includes coupling impedance means for coupling the outputs of said first and second capacitor means to the base electrode of said switching transistor, said coupling impedance means being arranged to maintain said switching transistor off when said amplifier is under normal operating condition and conductive when the voltage across the output load reaches a predetermined low level corresponding to an unsafe steady state operating condition of said output driving transistor.

Claim 16

A method of protecting an amplifying device comprising supplying an input to said amplifying device, sensing said amplifying device and driving outputs corresponding to the current through and voltage across said amplifying device, combining and integrating with respect to time said outputs to produce a control signal which is representative at all times of the current through and the voltage across said amplifying device and shunting in response to said control signal at least a portion of the input to said amplifying device when said control signal is at a level corresponding essentially the maximum duration and amplitude of current and voltage said amplifying device may safely tolerate. 15. A method of protecting an amplifying device as in claim 12, wherein said outputs are separately integrated and then combined to produce said control signal.

Claim 19

A method of providing overload and short circuit protection as in claim 16, wherein each of said first and second outputs are rectified before being integrated with respect to time.