Isolator circuit
View Patent ↗An isolator circuit ( 25 ) for a unit of a safety system ( 10 ) includes a power control line ( 14 ) connectable to a first loop of a safety system and a power connection ( 16 ) connectable to a second loop of the safety system. A switch ( 26 ) is connected to the power control line ( 14 ), and the switch has a closed configuration and an open configuration. A controller ( 28 ) controls the configuration of the switch ( 26 ). If a voltage across the circuit ( 10 ) from the power connection ( 16 ) to the power control line ( 14 ) falls below a predetermined level, the controller ( 28 ) opens the switch ( 26 ), thereby causing a disconnection to occur in the first loop.
1. An isolator circuit for a unit of a detection system, the isolator circuit comprising:
a first power control line and a second power control line;
a first power connection connected to the first power control line and a second power connection connected to the second power control line;
a switch in the first power control line, the switch having a closed configuration and an open configuration; and
a controller for operating the switch;
wherein the controller is arranged to measure a power supply voltage across the circuit from the first and second power control lines, and if the voltage falls below a predetermined level, the controller opens the switch, thereby causing a disconnection to occur in the first power control line, wherein a first input connects the controller to the first power control line at a first point of the first power control line and a second input connects the controller to the first power control line at a second point of the first power control line, the first point and the second point of the first power control line are positioned on opposing sides of the switch with respect to each other, and the controller is configured to receive power via both the first input and the second input regardless of the switch being open.
2. An isolator circuit according to claim 1 , wherein the switch comprises a solid-state switch.
3. An isolator circuit according to claim 1 , wherein the switch comprises a pair of field-effect transistors connected in series.
4. An isolator circuit according to claim 1 , wherein the power control line is arranged to carry a negative voltage.
5. An isolator circuit according to claim 1 , wherein the controller is arranged to receive power from the power control line on both sides of the switch.
6. An isolator circuit according to claim 5 , wherein the controller includes a diode arrangement to separate the power control line on each side of the switch.
7. An isolator circuit according to claim 1 , wherein the isolator circuit is incorporated into an ASIC.
8. An isolator circuit according to claim 1 , further comprising a second power control line, and wherein the controller is such that, if a voltage between the power control lines falls below a predetermined level for less than a predetermined period of time, the controller does not open the switch.
9. A unit for a safety system, comprising an isolator circuit, the isolator circuit comprising:
a first power control line and a second power control line;
a first power connection connected to the first power control line and a second power connection connected to the second power control line;
a switch in the first power control line, the switch having a closed configuration and an open configuration; and
a controller for operating the switch;
wherein the controller is arranged to measure a power supply voltage across the circuit from the first and second power control lines, and if the voltage falls below a predetermined level, the controller opens the switch, thereby causing a disconnection to occur in the first power control line, wherein a first input connects the controller to the first power control line at a first point of the first power control line and a second input connects the controller to the first power control line at a second point of the first power control line, the first point and the second point of the first power control line are positioned on opposing sides of the switch with respect to each other, and the controller is configured to receive power via both the first input and the second input regardless of the switch being open.
10. A unit according to claim 9 , further comprising an optical data receiver for receiving an optical data signal from an external source.
11. A unit according to claim 10 , wherein the switch is operable via the optical data receiver.
12. A unit according to claim 9 , further comprising a visual indicator for indicating when the switch is open.
13. A unit according to claim 12 , wherein the visual indicator is an LED.
14. A unit according to claim 9 , wherein the safety system is a detector system and the unit is a detector unit.
15. A detection system comprising an isolator circuit, the isolator circuit comprising:
a first power control line and a second power control line;
a first power connection connected to the first power control line and a second power connection connected to the second power control line;
a switch in the power control line, the switch having a closed configuration and an open configuration; and
a controller for operating the switch; and
a remote control device arranged to communicate with the circuit;
wherein the controller is arranged to measure a power supply voltage across the circuit from the first and second power control lines, and if the voltage falls below a predetermined level, the controller opens the switch, thereby causing a disconnection to occur in the first power control line, wherein a first input connects the controller to the first power control line at a first point of the first power control line and a second input connects the controller to the first power control line at a second point of the first power control line, the first point and the second point of the first power control line are positioned on opposing sides of the switch with respect to each other, and the controller is configured to receive power via both the first input and the second input regardless of the switch being open.
16. An isolator circuit according to claim 1 , wherein the controller opens the switch via an isolator control of the isolator circuit in response to the voltage between the second power control line and either one of the first input connecting the controller to the first power control line and the second input connecting the controller to the first power control line being below the predetermined level.
17. An isolator circuit according to claim 16 , wherein the controller continues to receive power via one of the first or second inputs connecting the controller to the first power control line when the switch is in an open configuration and the voltage between the second control line and one of the first and second inputs connecting the controller to the first power control line remains above the predetermined level.
18. An isolator circuit according to claim 1 , wherein the controller opens the switch via an isolator control of the isolator circuit in response to the voltage between the second power control line and either one of the first input connecting the controller to the first power control line and the second input connecting the controller to the first power control line being below 20 volts.
19. An isolator circuit according to claim 1 , wherein the controller includes a diode arrangement to separate portions of the first power control line on different sides of the switch.