Optocoupler with indication of light source power supply failure

1. An optical system, comprising:

at least one photodetector that receives light energy and converts the light energy into one or more electrical signals; and

a comparator module that receives the one or more electrical signals from the at least one photodetector and compares the one or more electrical signals against two different reference values, wherein a comparison of the one or more electrical signals against a first of the two different reference values is used to determine whether a power supply fault condition has occurred for a light source that emitted the light energy, and wherein a comparison of the one or more electrical signals against a second of the two different reference values is used to determine a logic signal conveyed to the at least one photodetector via the light energy emitted by the light source.

2. The optical system of claim 1 , wherein the logic signal corresponds to a first value when the one or more electrical signals is above the second of the two different reference values and wherein the logic signal corresponds to a second value when the one or more electrical signals is below the second of the two different reference values.

3. The optical system of claim 1 , wherein the comparator module comprises a comparison circuit containing a first comparator and a second comparator, wherein the first comparator and second comparator both receive the one or more electrical signals, wherein the first comparator compares the one or more electrical signals with the first of the two different reference values, and wherein the second comparator compares the one or more electrical signals with the second of the two different reference values.

4. The optical system of claim 3 , further comprising a transimpedance amplifier provided between the at least one photodetector and the comparator module, wherein the transimpedance amplifier amplifies the one or more electrical signals output by the at least one photodetector, and wherein the comparator module receives the one or more electrical signals after being amplified by the amplifier.

5. The optical system of claim 1 , further comprising:

a first light source that is electrically isolated from the at least one photodetector; and

an isolation barrier that electrically isolates the first light source from the at least one photodetector.

6. The optical system of claim 1 , further comprising a fault pin and an output voltage pin, wherein the fault pin provides an output indicating a fault condition when the one or more electrical signals do not exceed the first of the two different reference values, and wherein the output voltage pin provides the logic signal.

7. The optical system of claim 1 , wherein the two different reference values correspond to voltage reference values.

8. An optical system, comprising:

at least one photodetector that receives light energy and converts the light energy into one or more electrical signals; and

a comparator module that receives the one or more electrical signals from the at least one photodetector and compares the one or more electrical signals against two different reference values, wherein a comparison of the one or more electrical signals against a first of the two different reference values is used to determine whether a power supply fault condition has occurred for a light source that emitted the light energy, and wherein a comparison of the one or more electrical signals against a second of the two different reference values is used to determine a logic signal conveyed to the at least one photodetector via the light energy emitted by the light source, wherein the first reference value is smaller than the second reference value and is used to determine whether the photodetector is receiving light energy indicative of the light source being driven with at least a fault monitoring current.

9. An optocoupler, comprising:

a light source configured to generate light energy and convey the light energy across an isolation barrier;

a photodetector that receives the light energy and converts the light energy into an electrical signal; and

a comparator module that receives the electrical signal and provides two outputs based on an analysis thereof, wherein the first output provided by the comparator module comprises a fault output that is indicative of a fault condition associated with a power supply of the light source, and wherein the second output provided by the comparator module comprises a logic signal output that corresponds to a logic signal communicated by the light source across the isolation barrier via the light energy.

10. The optocoupler of claim 9 , wherein the comparator module comprises a pair of comparators and a logic circuit connected to the outputs of the pair of comparators.

11. The optocoupler of claim 9 , wherein the comparator module detects the fault condition by comparing the electrical signal with a first reference value and determining whether the electrical signal is greater than or less than the first reference value.

12. The optocoupler of claim 11 , wherein the comparator module detects the logic signal by comparing the electrical signal with a second reference value and determining whether the electrical signal is greater than or less than the second reference value.

13. The optocoupler of claim 12 , wherein the first reference value and second reference value corresponds to voltage reference values.

14. The optocoupler of claim 9 , wherein the light source receives a first driver current controlled by an input signal and wherein the light source also receives a second driver current that corresponds to a fault monitoring current.

15. The optocoupler of claim 14 , wherein the second driver current is substantially continuously provided to the light source unless there is a failure in a driver power supply for the light source.

16. The optocoupler of claim 15 , wherein the first driver current is intermittently provided to the light source depending upon a desired signal that is to be transmitted across the isolation barrier.

17. An isolation device, comprising:

at least one light source configured to generate light energy and convey the light energy across an isolation barrier;

at least one photodetector that receives light energy and converts the light energy into one or more electrical signals; and

a comparator module that receives the one or more electrical signals from the at least one photodetector and compares the one or more electrical signals against a first reference value and a second reference value, wherein a comparison of the one or more electrical signals against the first reference value is used to determine whether a power supply fault condition has occurred for the at least one light source, and wherein a comparison of the one or more electrical signals against the second reference value is used to determine a logic signal conveyed to the at least one photodetector via the light energy emitted by the at least one light source.

18. The isolation device of claim 17 , wherein the at least one light source comprises a first light source and a second light source, wherein the first light source receives a first driver current and intermittently transmits an optical logic signal across the isolation barrier in accordance with the first driver current, and wherein the second light source receives a second driver current and substantially continuously transmits an optical signal across the isolation barrier as long as the second driver current is being received by the second light source.

19. The isolation device of claim 17 , wherein the at least one photodetector comprises a first photodetector and a second photodetector, wherein the first photodetector is used to sense the logic signal, and wherein the second photodetector is used to detector the power supply fault condition.

20. The isolation device of claim 17 , wherein the comparator module comprises a comparison circuit containing a first comparator and a second comparator, wherein the first comparator and second comparator receive both receive the one or more electrical signals, wherein the first comparator compares the one or more electrical signals with the first reference value, and wherein the second comparator compares the one or more electrical signals with the second reference value.