Illuminated sign for traffic control and method for functional monitoring of such a sign

• US 20040201496A1
• Filed: 02/12/2004
• Published: 10/14/2004
• Est. Priority Date: 08/16/2001
• Status: Active Grant

• Current Assignee: Siemens AG
• Original Assignee: Siemens AG
• Inventors: Schierjott, Rudolf, Hering, Bernhard, Treffer, Gerhard
• Granted Patent: US 7,129,856 B2
• Time in Patent Office: Days
• US Class Current: 340/907
• CPC Class Codes: G09G 3/006 Electronic inspection or testing of displays and display drivers, e.g. of LED or LCD displays testing individual LED's G01R31/2635; testing lamps G01R31/44; testing of optical features of LCD displays G02F1/1309
• CPC Class Codes: H05B 45/50 responsive to malfunctions or undesirable behaviour of LEDs; responsive to LED life; Protective circuits
• 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

An illuminated sign is for traffic control, in particular for road traffic, and includes light sources for generation of the sign and a monitoring device for functional monitoring of the light source. The light sources are embodied as light diodes and the monitoring device is embodied as a device for the limited current loading of the light diodes. The functional monitoring of said sign can be achieved with reasonable technical requirements in both the deactivated and activated state thereof.

Claims

1. A sign for traffic control, comprising:

light sources, in the form of light-emitting diodes, for production of light to illuminate the sign; and

a monitoring device for functional monitoring of the light sources, wherein the monitoring device is designed to produce a limited current flow through the light-emitting diodes to restrict light emission from the light-emitting diodes in a manner not perceptible by a viewer of the sign, the monitoring device including switching means for switching off the current flow when a current level reaches a predetermined threshold value.

2. The sign as claimed in claim 1, wherein the switching means include a digital logic circuit with a memory element.

3. The sign as claimed in claim 1, wherein the monitoring device is further designed to measure voltage drop across light-emitting diodes through which a current is being passed.

4. The sign as claimed in claim 1, wherein the light sources are arranged as a chain of series-connected light-emitting diodes.

5. The sign as claimed in claim 1, wherein the light sources are arranged as a cluster of light-emitting diodes connected to one another.

6. A traffic sign, in particular for alternately displaying different signs, including the sign as claimed in claim 1.

7. A light signaling system, including the sign as claimed in claim 1.

11. The sign as claimed in claim 1, wherein the illuminated sign is for road traffic control.

12. The sign as claimed in claim 2, wherein the monitoring device is further designed to measure voltage drop across light-emitting diodes through which a current is being passed.

13. The sign as claimed in claim 3, wherein the light sources are arranged as a chain of series-connected light-emitting diodes.

14. The sign as claimed in claim 12, wherein the light sources are arranged as a chain of series-connected light-emitting diodes.

15. A traffic light including the sign as claimed in claim 1.

8. A method for functional monitoring of sign for traffic control including light-emitting diodes to produce light to illuminate the sign, comprising:

switching on current flow through the light-emitting diodes by generating a current monitoring signal, representing current level through the light-emitting diodes; and

switching off the current flow when the current monitoring signal reaches a predetermined threshold value.

9. The method as claimed in claim 8, further comprising:

generating a voltage monitoring signal, representing the voltage dropped across the light-emitting diodes through which a current is flowing.

10. The method as claimed in claim 8 wherein the current flows at least one of when the light-emitting diodes are in an inactive state, and periodically when the light-emitting diodes are in an inactive phase.

16. The method as claimed in claim 9, wherein the current flows at least one of when the light-emitting diodes are in an inactive state, and periodically when the light-emitting diodes are in an inactive phase.

17. A monitoring method for a sign for traffic control, including light-emitting diodes adapted to produce light to illuminate the sign, comprising:

generating a current monitoring signal, representing current level through the light-emitting diodes, to permit current flow through the light-emitting diodes; and

controlling a switching off of the current flow when the current monitoring signal reaches a predetermined threshold value.

18. The method as claimed in claim 17, further comprising:

generating a voltage monitoring signal, representing the voltage dropped across the light-emitting diodes through which a current is flowing.

19. The method as claimed in claim 18, wherein the current flows at least one of when the light-emitting diodes are in an inactive state, and periodically when the light-emitting diodes are in an inactive phase.

20. A device for a sign for traffic control, including light-emitting diodes adapted to produce light to illuminate the sign, comprising:

means for generating a current monitoring signal, representing current level through the light-emitting diodes, to permit current flow through the light-emitting diodes; and

means for controlling a switching off of the current flow when the current monitoring signal reaches a predetermined threshold value.

21. The sign as claimed in claim 20, wherein the means for controlling a switching off includes a digital logic circuit with a memory element.

22. The sign as claimed in claim 20, wherein the means for generating a current monitoring signal further for measuring voltage drop across light-emitting diodes through which a current is being passed.

23. The sign as claimed in claim 20, wherein the light-emitting diodes are arranged as a chain of series-connected light-emitting diodes.

24. The sign as claimed in claim 20, wherein the light-emitting diodes are arranged as a cluster of light-emitting diodes connected to one another.

25. A traffic sign for alternately displaying different signs, including the sign as claimed in claim 20.

26. A light signaling system including the sign as claimed in claim 20.

27. A sign for traffic control, comprising:

means, including a plurality of light-emitting diodes, for producing light to illuminate the sign; and

means for producing a limited current flow through the light-emitting diodes to restrict light emission from the light-emitting diodes in a manner not perceivable by a viewer of the sign, the means for producing including switching means for switching off the current flow when a current level reaches a predetermined threshold value.

28. The sign as claimed in claim 27, wherein the means for producing a limited current flow includes a digital logic circuit with a memory element.

29. The sign as claimed in claim 27, wherein the means for producing a limited current flow is further for measuring voltage drop across. light-emitting diodes through which a current is being passed.

30. The sign as claimed in claim 27, wherein the light-emitting diodes are arranged as a chain of series-connected light-emitting diodes.

31. The sign as claimed in claim 27, wherein the light-emitting diodes are arranged as a cluster of light-emitting diodes connected to one another.

32. A traffic sign for alternately displaying different signs, including the sign as claimed in claim 27.

33. A light signaling system including the sign as claimed in claim 27.