Flexible led backlighting circuit

• US 20020130985A1
• Filed: 12/28/2001
• Published: 09/19/2002
• Est. Priority Date: 01/16/2001
• Status: Active Grant

• Current Assignee: Visteon Global Technologies Incorporated (Visteon Corporation)
• Original Assignee: Visteon Global Technologies Incorporated (Visteon Corporation)
• Inventors: Anderson, David R., Weindorf, Paul F. L.
• Granted Patent: US 6,697,130 B2
• Time in Patent Office: Days
• US Class Current: 349/61
• CPC Class Codes: F21K 9/00 Light sources using semiconductor devices as light-generating elements, e.g. using light-emitting diodes [LED] or lasers
• CPC Class Codes: F21Y 2115/10 Light-emitting diodes [LED]
• CPC Class Codes: G02B 6/0068 Arrangements of plural sources, e.g. multi-colour light sources
• CPC Class Codes: G02B 6/0083 Details of electrical connections of light sources to drivers, circuit boards, or the like
• CPC Class Codes: G02B 6/0085 Means for removing heat created by the light source from the package heat extraction or cooling elements for semiconductor light sources in general H01L33/64
• CPC Class Codes: G02F 1/133603 with LEDs
• CPC Class Codes: G02F 1/133612 Electrical details
• CPC Class Codes: G02F 1/133615 Edge-illuminating devices, i.e. illuminating from the side
• CPC Class Codes: G09G 2320/041 Temperature compensation
• CPC Class Codes: G09G 3/342 using several illumination sources separately controlled corresponding to different display panel areas, e.g. along one dimension such as lines
• CPC Class Codes: H05B 45/18 using temperature feedback
• CPC Class Codes: H05B 45/46 having LEDs disposed in parallel lines
• CPC Class Codes: H05B 45/52 in a parallel array of LEDs
• CPC Class Codes: H05K 1/189 characterised by the use of a flexible or folded printed circuit H05K3/326 takes precedence

Abstract

A flexible circuit board mounted with top-light LEDs and LED control circuits provides a convenient and space efficient way to backlight an LCD. The flexible circuit board may have multiple tabs that are folded such that the top-light LEDs provide light into a light pipe from multiple directions. The top-light LEDs and LED control circuits may be located on the same side of the flexible circuit board for improved cost savings and manufacturability.

Claims

1. A light emitting diode (LED) device, comprising:

a light emitting diode;

a light emitting diode drive circuit;

a flexible circuit board having a tab region;

wherein the light emitting diode and the light emitting diode drive circuit are mounted on a first side of the flexible circuit board and wherein the tab region is folded such that the light emitting diode emit light toward a center region of the flexible circuit board.

2. The LED device of claim 1, wherein the light emitting diode comprise a top-light light emitting diode.

3. The LED device of claim 2, further comprising:

a stiffener attached with a second side of the flexible circuit board.

4. The LED device of claim 3, wherein the tab region of the flexible circuit board is folded twice.

5. The LED device of claim 4, wherein each of the tab regions of the flexible circuit board are folded twice such that the light emitting diode emits light substantially parallel to the central region of the flexible circuit board.

6. The LED device of claim 4, wherein the light emitting diode drive circuit is connected with a first portion of the tab region that is substantially at a forty-five degree angle relative to the center region of the flexible circuit board and the light emitting diode is connected with a second portion of the tab region that is substantially perpendicular to the center region of the flexible circuit board.

7. The LED device of claim 6, further comprising a second stiffener attached on the second side of the flexible circuit board in the center region of the flexible circuit board.

8. The LED device of claim 1, wherein the first side of the flexible circuit board comprises an exposed ground plane that can be connected directly to a frame member.

9. The LED device of claim 8, wherein the exposed ground plane transfers heat generated by the light emitting diode to the frame member.

10. The LED device of claim 9, further comprising a thermally conductive material between the exposed ground and the frame member.

11. The LED device of claim 1, further comprising:

a temperature sensor; and

a temperature control circuit;

wherein the temperature sensor and the temperature control circuit are mounted on the first side of the flexible circuit board and the temperature sensor and the temperature control circuit monitor a temperature of the light emitting diodes.

13. The LCD device of claim 12, wherein the light emitting diode comprises a top lighting light emitting diode.

14. The LCD device of claim 12, further comprising a stiffener attached with a first side of the flexible circuit board.

15. The LCD device of claim 14, wherein the side of the flexible circuit board is opposite the plurality of light emitting diode.

16. The LCD device of claim 14, further comprising a second stiffener attached on the second side of the flexible circuit board in the center region of the flexible circuit board.

17. The LCD device of claim 12, wherein the tab region of the flexible circuit board is folded twice.

18. The LCD device of claim 17, wherein the light emitting diode drive circuit is connected with a first portion of the tab region that is substantially at a forty-five degree angle relative to a center region of the flexible circuit board and the light emitting diode is connected with a second portion of the tab region that is substantially perpendicular to the center region of the flexible circuit board.

19. The LCD device of claim 12, wherein a first side of the flexible circuit board comprises an exposed ground plane that can be connected directly to a frame member.

20. The LCD device of claim 19, wherein the exposed ground plane transfers heat generated by the light emitting diode to the frame member.

21. The LCD device of claim 20, further comprising a thermally conductive material between the exposed ground and the frame member.

22. The LCD device of claim 12, wherein the tab region of the flexible circuit board is folded twice such that the light emitting diode emits light substantially parallel to a central region of the flexible circuit board.

23. The LCD device of claim 12, further comprising:

a temperature sensor; and

a temperature control circuit;

wherein the temperature sensor and the temperature control circuit are mounted on a first side of the flexible circuit board and the temperature sensor and the temperature control circuit monitor a temperature of the light emitting diode.

25. The LED device of claim 24, wherein a first side of the flexible circuit board comprises an exposed ground plane that can be connected directly to a frame member to transfer heat generated by the light emitting diode to the frame member.

26. The LED device of claim 25, further comprising a thermally conductive material between the exposed ground and the frame member.

12. A liquid crystal display (LCD) device, comprising:

a light pipe;

a light emitting diode;

a light emitting diode control circuit;

a flexible circuit board having a tab region;

wherein the light emitting diode and the light emitting diode control circuit are connected with the tab region of the flexible circuit board such that the light emitting diode emit light into the light pipe;

a light extracting surface located near a first side of the light pipe;

a diffuser located near a second side of the light pipe, where the first and second sides are opposite each other;

a reflective polarizer located above the diffuser; and

a liquid crystal display located above the reflective polarizer;

wherein the light pipe emits light that passes through the diffuser, the reflective polarizer, then the liquid crystal display.

24. A light emitting diode (LED) device comprising:

a top lighting light emitting diode;

a light emitting diode drive circuit;

a flexible circuit board having a tab region;

wherein the tab region of the flexible circuit board is folded at substantially a right angle relative to a center region of the flexible circuit board and the light emitting diode is mounted with a first side of the tab region and the light emitting diode drive circuit is mounted on a second side of the tab region.