Voltage dimmable LED display producing multiple colors

• US 6,653,798 B2
• Filed: 09/07/2001
• Issued: 11/25/2003
• Est. Priority Date: 09/29/2000
• Status: Expired due to Fees

• Current Assignee: Aerospace Optics, Inc.
• Original Assignee: Aerospace Optics, Inc.
• Inventors: Coley, Craig Jay, Guthrie, Don W.
• Primary Examiner(s): Philogene, Haissa
• Application Number:
  US09/949,139
• Publication Number:
  US 20020047576A1
• Time in Patent Office: 809 Days
• Field of Search: 315/169.1, 315/169.3, 315/164, 315/291, 315/200.A, 315/136, 315/185.R, 315/186, 362/800, 362/227, 362/231, 362/555, 362/561, 362/583, 323/267, 323/282, 250/552
• US Class Current: 315/200.00A
• CPC Class Codes: H01L 25/167 comprising optoelectronic devices, e.g. LED, photodiodes
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
• CPC Class Codes: H05B 45/20 Controlling the colour of the light
• CPC Class Codes: H05B 45/40 Details of LED load circuits
• CPC Class Codes: H05B 45/44 with an active control inside an LED matrix

Abstract

Multi-color illumination for a single display is achieved by utilizing an array of white light emitting diodes to produce illumination optically filtered by separate filters to produce the two or more desired output illumination colors at a desired luminance when the full rated voltage is applied to the light emitting diodes. Since all of the light emitting diodes have the same bandgap, voltage-controlled dimming produces uniform luminance changes for all colors as the voltage is reduced. A single voltage-controlled dimming driver circuit design and a single control voltage may therefore be utilized to achieve desired and uniform dimming characteristics independent of output illumination color.

Claims

1. For use in an illuminated display, an illumination source for providing illumination of two or more desired colors comprising:

two or more light emitting diodes driven by a single input voltage;

a first filter through which illumination produced by one of the light emitting diodes is passed to produce output illumination of a first color within a first portion of the display; and

a second filter through which illumination produced by another of the light emitting diodes is passed to produce output illumination of a second color within a second portion of the display,

wherein a luminance of the output illumination of the first color is approximately equal to a luminance of the output illumination of the second color.

2. The illumination source as set forth in claim 1, wherein the luminance of the output illumination of the first color is approximately equal to the luminance of the output illumination of the second color for any input voltage across an operating range of input voltages.

3. The illumination source as set forth in claim 1, wherein the output illumination of the first color and the output illumination of the second color may be uniformly dimmed by reducing the input voltage.

4. The illumination source as set forth in claim 1, wherein the two or more light emitting diodes further comprise:

an array of white light emitting diodes,

wherein a first group of the white light emitting diodes within the array produces illumination passed through the first filter and a second group of the white light emitting diodes within the array produces illumination passed through the second filter.

5. The illumination source as set forth in claim 4, further comprising:

a first driver circuit including the first group of the white light emitting diodes and receiving the input voltage; and

a second driver circuit including the second group of white light emitting diodes and receiving the input voltage,

wherein the first and second driver circuits are identical despite differences in the first and second output illumination colors.

6. The illumination source as set forth in claim 5, wherein the input voltage received by both the first and second driver circuits is selectively varied across an operating range of input voltages to alter the luminances of the first and second output illumination colors, and wherein the luminances of the first and second output illumination colors remain approximately equal despite changes in the input voltage.

7. The illumination source as set forth in claim 1, wherein the first and second filters each further comprise:

acrylic, polycarbonate, glass, or a combination thereof containing one or more dyes in concentrations selected to produce a desired output illumination luminance in the first or second output illumination color from illumination produced by one of the light emitting diodes when a full rated voltage is applied as the input voltage.

8. The illumination source as set forth in claim 1, wherein the first and second portions of the display are display regions within a single illuminated switch, indicator or annunciator.

9. The illumination source as set forth in claim 1, wherein the first and second portions of the display are display regions within separate illuminated switches, indicators or annunciators.

10. For use in an illuminated display, a method of providing illumination of two or more desired colors comprising:

driving two or more light emitting diodes with a single input voltage;

directing illumination produced by one or the light emitting diodes through a first filter to produce output illumination of a first color within a first portion of the display; and

directing illumination produced by another of the light emitting diodes through a second filter to produce output illumination of a second color within a second portion of the display,

wherein a luminance of the output illumination of the first color is approximately equal to a luminance of the output illumination of the second color.

11. The method as set forth in claim 10, wherein the step of driving two or more light emitting diodes with a single input voltage further comprises:

filtering the luminance produced by the two or more light emitting diodes through the first and second filters such that the luminance of the output illumination of the first color is approximately equal to the luminance of the output illumination of the second color for any input voltage across an operating range of input voltages.

12. The method as set forth in claim 10, further comprising:

uniformly dimming the output illumination of the first color and the output illumination of the second color by reducing the applied input voltage.

13. The method as set forth in claim 10, wherein the step of driving two or more light emitting diodes with a single input voltage further comprises:

driving an array of white light emitting diodes,

wherein a first group of the white light emitting diodes within the array produces illumination passed through the first filter and a second group of the white light emitting diodes within the array produces illumination passed through the second filter.

14. The method as set forth in claim 13, wherein the step of driving an array of white light emitting diodes further comprises:

driving the first group of white light emitting diodes using a first driver circuit receiving the input voltage; and

driving the second group of white light emitting diodes using a second driver circuit receiving the input voltage,

wherein the first and second driver circuits are identical despite differences in the first and second output illumination colors.

15. The method as set forth in claim 14, further comprising:

selectively varying the input voltage received by both the first and second driver circuits across an operating range of input voltages to alter the luminances of the first and second output illumination colors, wherein the luminances of the first and second output illumination colors remain approximately equal despite changes in the input voltage.

16. The method as set forth in claim 10, wherein the steps of directing illumination produced by one of the light emitting diodes through a first filter to produce output illumination of a first color within a first portion of the display and directing illumination produced by another of the light emitting diodes through a second filter to produce output illumination of a second color within a second portion of the display each further comprise:

directing illumination through a filter comprising acrylic, polycarbonate, glass, or a combination thereof containing one or more dyes in concentrations selected to produce a desired output illumination luminance in the first or second output illumination color from illumination produced by one of the light emitting diodes when a full rated voltage is applied as the input voltage.

17. A voltage-controlled dimming illuminated display comprising:

first and second groups of white light emitting diodes selectively producing illumination for first and second display regions, respectively;

first and second voltage-controlled dimming driver circuits driving the first and second groups of white light emitting diodes, respectively, in response to a single input voltage;

a first optical filter between the first group of white light emitting diodes and the first display region filtering illumination produced by the first group of white light emitting diodes to produce output illumination of a first color on the first display region; and

a second optical filter between the second group of white light emitting diodes and the second display region filtering illumination produced by the second group of white light emitting diodes to produce output illumination of a second color on the second display region,

wherein a luminance of the output illumination of the first color is approximately equal to a luminance of the output illumination of the second color for any input voltage within an operating range of input voltages.

18. The voltage-controlled dimming illuminated display as set forth in claim 17, wherein the first and second voltage-controlled dimming driver circuits each further comprise:

first and second sets of series-connected light emitting diodes connected between an input port and an output port; and

a switching circuit coupled to the first and second sets of light emitting diodes, wherein the switching circuit switches the first and second sets of light emitting diodes between series-connection and parallel-connection.

19. The voltage-controlled dimming illuminated display as set forth in claim 18, wherein switching circuit within each of the first and second voltage-controlled dimming driver circuits further comprises:

a diode connected in series between first and second sets of light emitting diodes, wherein the diode and all light emitting diodes within the first and second sets of light emitting diodes have a common forward bias orientation;

a first resistor connected in parallel with the diode and the first set of light emitting diodes; and

a second resistor connected in parallel with the diode and the second set of light emitting diodes.

20. The voltage-controlled dimming illuminated display as set forth in claim 17, wherein the output illumination of the first color and the output illumination of the second color may be uniformly dimmed by reducing the input voltage.

21. The voltage-controlled dimming illuminated display as set forth in claim 17, wherein the input voltage received by both the first and second driver circuits is selectively varied across an operating range of input voltages to alter the luminances of the first and second output illumination colors, and wherein the luminances of the first and second output illumination colors remain approximately equal despite changes in the input voltage.

22. The voltage-controlled dimming illuminated display as set forth in claim 17, wherein the first and second optical filters each further comprise:

acrylic, polycarbonate, glass, or a combination thereof containing one or more dyes of types and in concentrations selected to produce a desired output illumination luminance in the first or second output illumination color from illumination produced by one of the first and second groups of white light emitting diodes when a full rated voltage is applied as the input voltage.

23. For use in an illuminated display, an illumination source for providing illumination of a desired color comprising:

at least one white light emitting diode selectively driven by an input voltage; and

an optical filter through which illumination produced by the white light emitting diode is passed to produce output illumination of the desired color,

wherein a luminance of the output illumination varies in response to changes in the input voltage and equals one of two or more desired luminances, independent of the desired color, when the input voltage is a corresponding one of two or more predefined input voltages within an operating range of input voltages.

24. The illumination source as set forth in claim 23, wherein the optical filter further comprises:

acrylic, polycarbonate, glass, or a combination thereof containing one or more dyes of types and in concentrations selected to produce a desired output illumination luminance in the desired color from illumination produced by at least one white light emitting diode when a full rated voltage is applied as the input voltage.

25. The illumination source as set forth in claim 23, wherein a driver for the at least one white light emitting diode contains component values selected independent of the desired color.

26. The illumination source as set forth in claim 23, wherein the at least one light emitting diode has a diffused top.

27. A pushbutton cap for retrofitting a pushbutton switch illuminated by incandescent lamps comprising:

a mount holding an array of light emitting diodes;

one or more drivers for selectively causing the light emitting diodes to illuminate in response to an input voltage; and

one or more optical filters between the light emitting diodes and a display surface for producing illumination of at least one desired color at a preselected luminance corresponding to the input voltage,

wherein the mount, the light emitting diodes, the drivers and the optical filters are all contained within a pushbutton cap which is capable of being received by a switch body for the pushbutton switch and, once disposed within the switch body, is operative with control elements within the switch body for operating the incandescent lamps.

28. The pushbutton cap as set forth in claim 27, wherein the drivers and the optical filters cause the illumination to have a luminance equivalent to a luminance of the incandescent lamps at the input voltage.

29. An illumination system for providing multiple levels of fault tolerance comprising:

an illuminated display including first and second adjacent display regions spanned by a legend;

a first illumination source including two or more light emitting diodes serially-connected at least when an input voltage exceeds a threshold and selectively illuminating the first display region; and

a second illumination source including two or more light emitting diodes serially-connected at least when an input voltage exceeds a threshold and selectively illuminating the second display region,

wherein, upon failure of one light emitting diode within one of the first or second illumination sources, one or more remaining light emitting diodes within the respective first or second illumination source continues to illuminate the corresponding first or second display region.

30. The illumination system as set forth in claim 29, wherein the first and second illumination sources operate independently, each continuing to illuminate the corresponding first or second display region after failure of a light emitting diode within the other of the first or second illumination sources.

31. The illumination system as set forth in claim 30, wherein the legend also spans third and fourth display regions illuminated by third and fourth illumination sources, respectively.

33. The illumination system as set forth in claim 29, wherein the four separate drivers produce uniform voltage-controlled dimming by all quadrants.

32. An illumination system for providing flexibility in configuring an illuminated display comprising:

an array of light emitting diodes logically divided into quadrants, each quadrant illuminating a portion of a display; and

four separate drivers independently controlling operation of light emitting diodes within each quadrant,

wherein all drivers are controlled individually to provide a four-way split illuminated display, and

wherein two or more drivers are selectively controlled in unison to provide a full field illuminated display, a two-way split illuminated display, or a three-way split illuminated display.