Optically coupled control circuit

Claim 2

A power control circuit for controlling the flow of electrical current from a plurality of power lines to a load device, said control circuit comprising, in combination: current responsive means for responding to a predetermined load condition in one of said power lines to provide an output signal; a control circuit responsive to said output signal to provide a control signal; and a switch circuit including a switch electrically isolated from said current responsive means and said control circuit and adapted to be serially connected in only one of the other of said power lines, said switch switchable in response to a triggering signal between a first state permitting the conduction of current to said load device and a second state for interrupting such conduction of current, said switch circuit further including a switch driver circuit electrically isolated from said current responsive means and said control circuit and connected to said switch, said driver circuit responsive to said control signal when provided by said control circuit to provide such a triggering signal to said switch.

Claim 3

The power control circuit of claim 1 further including means for conducting said control signal from said control circuit to said switch driver circuit while maintaining electrical isolation between said driver circuit and said control circuit.

Claim 4

The power control circuit of claim 1 wherein the type of load device to be controlled by said power control circuit is one connected in a fluid flow system, and wherein said control means includes means adapted to be connected to said fluid flow system for providing said control signal in response to a condition in said fluid flow system.

Claim 5

The power control circuit of claim 1 wherein said current responsive means includes delay means for inhibiting response to said predetermined load condition except when said load condition is present for a predetermined period of time.

Claim 6

The power control circuit of claim 1 including a plurality of said switch circuits each including a switch adapted to be serially connected in only one of said other of said power lines, each of said switch circuits electrically isolated from each other, said control circuit and said current responsive means, and a plurality of said switch driver circuits each connected to only one of said switches and electrically isolated from each other, said control circuit and said current responsive means.

Claim 7

The power control circuit of claim 5 further including means for conducting said control signal from said control circuit to each of said switch driver circuits while maintaining electrical isolation between said switch driver circuits and said control circuit.

Claim 8

The power control circuit of claim 5 wherein each of said switches includes a diode bridge circuit and an SCR connected to permit conduction of current through said diode bridge circuit.

Claim 9

The power circuit of claim 5 wherein said control signal is a light signal and said control circuit includes light emitting means for providing said light signal in response to said output signal, and said switch driver circuits each include light responsive means optically coupled to said light emitting means for responding to light signals form said light emitting means.

Claim 10

The power control circuit of claim 8 wherein said light responsive means is a light sensitive semiconductor device.

Claim 11

The power control circuit of claim 1 wherein said control signal is a light signal and said control circuit includes light emitting means providing said light signal in response to said output signal, and said switch driver circuit includes light responsive means optically coupled to said light emitting means for responding to light signals form said light emitting means.

Claim 12

The power control circuit of claim 10 wherein said light responsive means is a light sensitive semiconductor device.

Claim 13

The power control circuit of claim 10 wherein said predetermined load condition is a current overload, and said light emitting means provides said light signal in absence of said overload, and wherein said switch driver circuit responds to the absence of said light signal to cause said switch means to interrupt the flow of current to said load.

Claim 14

A power control circuit for controlling the application of power from a plurality of power lines in a multi-phase power line system to a load device, comprising, in combination: control means for responding to a predetermined operating condition of said load device to provide a control signal, said control means being electrically isolated from at least one line of any pair of said power lines, and a plurality of separate switch circuits each adapted to be connected to control the flow of electrical current in only one of said power lines to said load device, each of said switch circuits electrically isolated from said control means and the other switch circuits and each including a switch connected in the respective only one of said power lines and switchable in response to a trigger signal from a first state permitting such flow of electrical current to a second state for interrupting such flow of electrical current, each of said switch circuits further including a switch driver circuit connected to the respective switch and responsive to said control signal to provide said trigger signal.

Claim 15

A power control circuit for controlling the application of power from a plurality of power lines in a multi-phase power line system to a load device, comprising, in combination: control means for responding to a predetermined operating condition of said load device to provide a control signal, said control means being electrically isolated from at least one line of any pair of said power lines, and a plurality of separate switch circuits each adapted to be connected to control the flow of electrical current in only one of said power lines to said load device, each of said switch circuits electrically isolated from said control means and the other switch circuits and each including a switch connected in the respective only one of said power lines and switchable in response to a trigger signal from a first state permitting such flow of electrical current to a second state for interrupting such flow of electrical current, each of said switch circuits further including a switch driver circuit connected to the respective switch and responsive to said control signal to provide said trigger signal.

Claim 16

The power control circuit of claim 13 wherein a switch is provided for each of all but one of said power lines and said control means includes means adapted to respond to a predetermined current condition in one of said power lines to provide said control signal.

Claim 17

The power control circuit of claim 14 wherein the type of load device to be controlled by said power control circuit is one connected in a fluid flow system, and wherein said control means also includes means adapted to respond to a predetermined fluid flow condition in said fluid flow system to provide said control signal.

Claim 18

The power control circuit of claim 13 wherein the type of load device to be controlled by said power control circuit is one connected in a fluid flow system and said control means Includes means adapted to respond to a predetermined fluid flow condition in said fluid flow system to provide said control signal.

Claim 19

The power control circuit of claim 16 wherein said last mentioned means includes a pressure switch for responding to a fluid pressure condition in said fluid flow system.

Claim 20

An overload control circuit for controlling the application of power from a plurality of power lines in a multi-phase power line system to a load device, comprising, in combination: separate light responsive solid state switching means each adapted to be connected to one of all but one of said multi-phase lines to permit the conduction of current to a load, each such switching means switchable between a state permitting conduction of current to said load device and a state interrupting such conduction of current and being responsive to receipt at an input of a light signal to change between such states; sensor means for sensing a predetermined current condition in said but one of the multi-phase lines; and control means connected to said sensor means and responsive thereto to emit a light signal when a predetermined change in a current condition in said one line is sensed, said light signal being coupled to said input of each of said switching means.

Claim 21

An overload control circuit for controlling the application of power from a plurality of power lines in a multi-phase power line system to a load device, comprising, in combination: separate light responsive solid state switching means each adapted to be connected to one of all but one of said multi-phase lines to permit the conduction of current to a load, each such switching means switchable between a state permitting conduction of current to said load device and a state interrupting such conduction of current and being responsive to receipt at an input of a light signal to change between such states; sensor means for sensing a predetermined current condition in said but one of the multi-phase lines; and control means connected to said sensor means and responsive thereto to emit a light signal when a predetermined change in a current condition in said one line is sensed, said light signal being coupled to said input of each of said switching means.