Light-emitting diode display

• US 4,298,869 A
• Filed: 06/25/1979
• Issued: 11/03/1981
• Est. Priority Date: 06/29/1978
• Status: Expired due to Term

• Current Assignee: Zaidan Hojin Handotai Kenkyu Shinkokai
• Original Assignee: Zaidan Hojin Handotai Kenkyu Shinkokai
• Inventors: Okuno, Yasuo
• Primary Examiner(s): TRAFTON, DAVID
• Application Number:
  US06/052,014
• Time in Patent Office: 862 Days
• Field of Search: 340/46, 340/84, 340/332, 340/366 R, 340/378 R, 340/782, 340/762, 313/500, 357/17, 362/800
• US Class Current: 345/82
• CPC Class Codes: F21K 9/23 Retrofit light sources for lighting devices with a single fitting for each light source, e.g. for substitution of incandescent lamps with bayonet or threaded fittings
• CPC Class Codes: F21W 2111/02 for roads, paths or the like
• CPC Class Codes: F21Y 2115/10 Light-emitting diodes [LED]
• CPC Class Codes: G08B 5/36 using visible light sources
• CPC Class Codes: G08G 1/095 Traffic lights
• CPC Class Codes: G09F 13/0472 Traffic signs
• CPC Class Codes: G09F 13/22 electroluminescent electroluminescent light sources per se H05B33/00
• CPC Class Codes: G09F 2013/222 with LEDs
• CPC Class Codes: G09F 2013/227 Electroluminescent displays for vehicles
• CPC Class Codes: H05B 45/395 Linear regulators
• CPC Class Codes: H05B 45/54 in a series array of LEDs
• CPC Class Codes: Y02B 20/30 Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]
• CPC Class Codes: Y10S 362/80 Light emitting diode

Abstract

A plurality of light-emitting diodes are connected in series to elevate the working voltage. A plurality of said series connection are connected in parallel to maintain display even upon a disconnection accident. The total number of light-emitting diodes provides a bright and failure-safe colored light display at a low power consumption. The conventional colored-light-emitting display can be easily substituted by the novel light-emitting diode display to reduce the power consumption and elongate the service lifetime.

Claims

1. A light-emitting diode (LED) lamp comprising:

a housing including a lamp base of a predetermined shape adapted for effecting electrical connection to a commercial AC power source, said AC power source having a predetermined maximum voltage;

a current-regulating means electrically connected to said lamp base and disposed in said base to facilitate dissipation of heat generated by said current-regulating means through said base; and

a display panel connected mechanically to said housing and electrically to said current regulating means and including a multiplicity of light-emitting diodes, groups of said diodes being connected in series, said series connected group having an operating threshold voltage at least about one half of said predetermined maximum voltage said groups being electrically connected in parallel said multiplicity of light emitting diodes being driven simultaneously by the current from said regulating means.

2. A light-emitting diode lamp according to claim 1, wherein:

said display panel comprises a plurality of display units, each display unit including at least one series connection of substantially the same number of light-emitting diodes.

3. A light-emitting diode lamp according to claim 2, wherein:

said plurality of display units are connected in series and each of said display units includes a parallel connection of a plurality of said series connection.

4. A light-emitting diode lamp according to claim 2, wherein:

said plurality of display units are connected in parallel.

5. A light-emitting diode lamp according to claim 2, wherein:

said plurality of display units are connected in a plurality of series connections which are connected in parallel.

6. A light emitting diode lamp according to claim 1, 2, 3, 4 or 5, wherein:

said display panel comprises a reflector having concave reflecting surfaces registered with the respective light-emitting diodes.

7. A traffic signal system adapted to be driven by a commercial AC power signal having a predetermined maximum voltage, comprising:

a red and a green signal lamp, each signal lamp including a plurality of display units connected in parallel, each display unit including a plurality of series connected light-emitting diodes and a current adjusting means, said plurality of series connected light-emitting diodes having an operating threshold voltage of at least about one half of said predetermined maximum voltage.

8. A light-emitting diode display device adapted to be driven by a commercial AC power source having a predetermined maximum voltage said device comprising:

a display surface having a plurality of sections; and

a multiplicity of light-emitting diodes disposed in each of said sections, groups of said light-emitting diodes being electrically connected in series such that said group has an operating threshold voltage at least approximately one half of said predetermined maximum voltage, said groups being electrically connected in parallel,

means for limiting the current through each group in said section,

said light-emitting diodes in each section emitting lights of a single color,

said display surface including a first number of sections emitting light of a first color and a second number of sections emitting light of a second color.

9. A light-emitting diode display device according to claim 8, wherein:

said display surface further includes a third number of sections emitting light of a third color.

10. A light-emitting diode display device according to claim 8 or 9, wherein:

said first color is red and said second color is green.

11. A light-emitting diode display device according to claim 9, wherein:

said first color is red, said second color is green and said third color is yellow.

12. A light-emitting diode (LED) display adapted to be driven by a commercial AC power source having a predetermined instantaneous maximum voltage (E_m), said display comprising:

at least one group of luminescent units, each said luminescent unit comprising a plurality of serially connected LED'"'"'s, each of said units having an operating threshold voltage (V_th) equal to at least approximately one half of said predetermined maximum voltage (E_m) and being electrically connected in parallel to the other luminescent units in said group so that all units in said group are concurrently driven by said AC power source; and

current limiting means for limiting the current through each of said units.

13. Light-emitting diode display according to claim 12, wherein:

said plurality of light-emitting diodes simultaneously emit lights of a same color.

14. Light-emitting diode display according to claim 12, further comprising:

a rectifying circuit for rectifying an alternating current from said AC source and supplying a rectified electric power to said parallel connection of units.

15. Light-emitting diode display according to claim 14, further comprising:

a charge-storing means for charging and discharging electric charge, connected between said rectifying circuit and said parallel connection.

16. Light-emitting diode display according to claim 12, further comprising:

a total current-limiting means connected in series with said parallel connection for supplying a limited total current thereto.

17. Light-emitting diode display according to claim 16, wherein:

said current limiting means comprises a current-adjusting resistance in each unit serially connected to said series connection of light-emitting diodes.

18. Light-emitting diode display according to claim 17, wherein:

said total current limiting means includes a current stabilizing circuit for supplying a predetermined constant current.

19. Light-emitting diode display according to claim 16, further comprising:

a housing for accommodating said group of luminescent units, including a lamp base of a predetermined shape for providing electrical connections to said source;

said total current-limiting means being thermally connected to said lamp base.

20. Light-emitting diode display according to claim 12, further comprising:

a housing for accomodating said group of luminescent units and for providing electrical connections to said source.

21. Light-emitting diode display according to claim 12, further comprising:

at least one other group of luminescent units.

31. The display of claim 17, 18, or 30 wherein:

said operating threshold voltage is at most about 0.9 of said maximum voltage.

22. A light-emitting diode lamp adapted to be driven by chargeable battery, comprising:

a housing including a standard lamp base having at least first and second terminals;

means for limiting current flowing therethrough and electrically connected to said first terminal, and disposed at least partially in said lamp base such that heat generated by said means for limiting current is dissipated through said lamp base;

a light-emitting surface coupled to said housing; and

light emitting diode circuitry provided in said light-emitting surface and electrically connected between current-limiting means and said second terminal, the circuitry including a plurality of lines connected in parallel, each line including a current-adjusting resistor and a plurality of light-emitting diodes connected in series, all the light-emitting diodes in said circuitry being arranged to be driven simultaneously.

23. A light-emitting diode lamp according to claim 22, wherein:

said housing includes a third terminal;

another means for limiting current flowing therethrough and electrically connected to said third terminal and disposed at least partially in said lamp base with low heat resistance therebetween; and

another light-emitting diode circuit provided in said light-emitting surface and electrically connected between said third current-limiting means and said second terminal,

said another circuit including a plurality of lines connected indiodes connected in series, al the light-emitting diodes in said circuitry being arranged to be driven simultaneously.

24. A light-emitting diode lamp according to claim 22 or 23, wherein:

said light-emitting surface comprises a reflector having concave reflecting surfaces registered with the respective light-emitting diodes.

25. A light-emitting diode (LED) display adapted for cooperating with a standard light fixture, comprising:

a housing including a base portion configured to cooperate with said standard fixture and to effect first and second respective electrical connections with said fixture;

at least one group of luminescent units, each said unit comprising a plurality of LED'"'"'s and a current adjusting device electrically connected in series, each of said units being electrically connected in parallel between said first electrical connection with said fixture and a common node; and

current limiting means, for limiting the current flow therethrough, disposed at least partly within said base portion such that heat generated by said current limiting means is dissipated through said base portion and electrically connected between said common node and said second electrical connection with said fixture.

26. A light-emitting diode (LED) display adapted to be driven by a commercial AC power source having a maximum voltage E_m, said display comprising:

at least two groups of luminescent units, each group including a plurality of luminescent units connected in parallel and each unit including a plurality of LED'"'"'s connected in series, the respective groups being connected in series so as to drive all the LED'"'"'s in the respective groups simultaneously from said AC power source, said series connected groups having an operating threshold voltage at least about one half of said maximum voltage E_m ; and

current limiting means for limiting the current through each of said units.

27. Light-emitting diode display according to claim 26, wherein:

said respective groups of luminescent units have substantially the same electric and optical characteristics.

28. The display of claim 27 further comprising a current limiting device connected in series with said respective groups of luminescent units.

29. Light-emitting diode display according to claim 28, wherein:

said current limiting means comprises a current-adjusting resistance in each luminescent unit electrically connected in series with said plurality of serially connected LEDs.

30. Light-emitting diode display according to claim 28 wherein:

said current limiting device has a saturating current versus voltage characteristics.

32. A light-emitting diode (LED) display adapted to be driven by an AC power source, said source providing a voltage E_ac, where E_ac =E_m sin wt, said display comprising a plurality of luminescent units, each unit comprising a plurality of series-connected LED'"'"'s, said LED'"'"'s emitting substantial light only in response to voltages applied across said unit at least equal to a predetermined operating threshold voltage V_th, where V_th ≧

0.5 E_m,

means for electrically connecting respective ones of said units in parallel to form respective groups of units;

current limiting means for limiting the current through each of said units; and

means for electrically connecting said groups of units to said source such that each unit in a group is concurrently drawn by said source.

33. The display of claim 32 wherein each unit further comprises a current limiting resistance.

34. The display of claim 32 or 33 further comprising means for rectifying said voltage E_ac.

35. The display of claim 34 wherein V_th is equal to at least approximately 0.9 E_m.

36. The display of claim 34 wherein V_th equals approximately √

2×

E_m.

37. The display of claim 34 wherein V_th equals a value in the range of approximately 0.6 E_m to approximately 0.7 E_m.

38. The display of claim 32 or 33 wherein V_th is equal to at least approximately 0.9 E_m.

39. The display of claim 32 or 33 wherein V_th equals approximately √

2×

E_m.

40. The display of claim 32 or 33 wherein V_th equals a value in the range of approximately 0.6 E_m to approximately 0.7 E_m.