Solid state light with self diagnostics and predictive failure analysis mechanisms

• US 6,448,716 B1
• Filed: 08/17/2000
• Issued: 09/10/2002
• Est. Priority Date: 08/17/2000
• Status: Expired due to Fees

• Current Assignee: Light Vision Systems Incorporated
• Original Assignee: General Signal Technology Corp. (SPX Corporation)
• Inventors: Hutchison, Michael C.
• Primary Examiner(s): VU, DAVID HUNG
• Application Number:
  US09/641,424
• Time in Patent Office: 754 Days
• Field of Search: 315/106, 315/129, 315/130, 315/131, 315/134
• US Class Current: 315/129
• CPC Class Codes: H05B 45/12 using optical feedback
• CPC Class Codes: H05B 45/325 Pulse-width modulation [PWM]
• CPC Class Codes: H05B 45/58 involving end of life detection of LEDs
• CPC Class Codes: H05B 47/20 Responsive to malfunctions or to light source life; for protection

Abstract

A solid state light apparatus ideally suited for use in traffic control signals having a Self Diagnostic/Predictive Failure Analysis (SD/PFA) function facilitating a real time status of the signal as well as prediction of failure years in advance of the actual failure. Unlike incandescent signals, all LED based signals degrade over time until they are no longer in DOT light output specifications. Current state of the art solid state signals must be periodically monitored to see if the light output is in specification. This is done by having DOT or contracted personnel ascend in a bucket truck and place a light meter on the signal typically on an annual basis. A signal system with SD/PFA coupled with a modem or RF link provides real time data, without the use of a bucket truck on the status of the signal. The system also provides data which allows the determination via an algorithm of when the signal will go below light output specifications in the future.

Claims

1. A solid state light, comprising;

a solid state light source producing light output; and

a monitoring circuit coupled to said light source predicting, prior to a degradation of said solid state light output below a first predetermined threshold, when said light output will fall below said first predetermined threshold.

2. The light as specified in claim 1, wherein said solid state light source is driven by a power circuit having a drive current, wherein said monitor circuit monitors said drive current to predict when said light output will fall below said first predetermined threshold.

3. The light as specified in claim 1, wherein said solid state light source is driven by a power circuit having a drive voltage, wherein said monitor circuits monitors said drive voltage to predict when said light output will fall below said first predetermined threshold.

4. The light as specified in claim 1, wherein said solid state light source is driven by a power circuit having a pulse width modulated (PWM) drive voltage, wherein said monitor circuit monitors a duty cycle of said PWM drive voltage to predict when said light output will fall below said first predetermined threshold.

5. The light as specified in claim 1, wherein the duty cycle of said drive voltage is increased as said solid state light source degrades in light output, wherein said monitor circuit monitors when said duty cycle exceeds a second predetermined threshold to predict when said light output will fall below said first predetermined threshold.

6. The light as specified in claim 1, wherein said solid state light source increases in operating temperature as said solid state light source degrades, wherein said monitoring circuit monitors said light source operating temperature to predict when said light output fall below said first predetermined threshold.

7. The light as specified in claim 1, further comprising a notification circuit generating an output signal indicative of said prediction when said light output will fall below said first predetermined threshold.

8. The light as specified in claim 2 further comprising a notification circuit generating an output signal indicative of said prediction when said light output will fall below said first predetermined threshold.

9. The light as specified in claim 3 further comprising a notification circuit generating an output signal indicative of said prediction when said light output will fall below said first predetermined threshold.

10. The light as specified in claim 4 further comprising a notification circuit generating an output signal indicative of said prediction when said light output will fall below said first predetermined threshold.

11. The light as specified in claim 5 further comprising a notification circuit generating an output signal indicative of said prediction when said light output will fall below said first predetermined threshold.

12. The light as specified in claim 6 further comprising a notification circuit generating an output signal indicative of said prediction when said light output will fall below said first predetermined threshold.

13. The light as specified in claim 7 wherein said notification circuit generates said output signal as an RF signal.

14. The light as specified in claim 7 wherein said notification circuit has a modem generating an electric signal as said output signal.

15. The light as specified in claim 7 wherein said modification circuit modifies said solid state light source output from a normal operation to indicate said light output is predicted to fall below said first predetermined threshold within a predetermined time period.

16. A method of operating a solid state light source, comprising the steps of:

driving the solid state light providing a light output source and having operating parameters; and

monitoring at least one said operating parameter to predict when said light output, prior to a degradation of said solid state light output below a first predetermined threshold, will fall below said first predetermined threshold.

17. The method of operating a solid state light source in claim 16 wherein said monitored operating parameter is selected from the group comprising:

a drive current, a drive voltage, a drive voltage duty cycle, an operating temperature and time.

18. The method of operating a solid state light source in claim 16 further comprising the step of generating a notification signal indicative of said prediction when said light output will fall below said first predetermined threshold.

19. The method of operating a solid state light source in claim 18 wherein said notification signal is selected from the group comprising

an RF signal, an electrical signal, and an optical signal indicative of when said light output is predicted to fall below said first predetermined threshold within a predetermined time period.

20. The method of operating a solid light source in claim 16 wherein said first predetermined threshold is the minimum light required of a traffic signal for signaling automobiles.