Lighting Apparatus Having Multiple Light-Emitting Diodes With Individual Light-Conversion Layers

• US 20100259924A1
• Filed: 04/08/2009
• Published: 10/14/2010
• Est. Priority Date: 04/08/2009
• Status: Active Grant

• Current Assignee: Ledengin, Inc. (Ams-Osram AG)
• Original Assignee: Ledengin, Inc. (Ams-Osram AG)
• Inventors: Dong, Yi
• Granted Patent: US 7,985,000 B2
• Time in Patent Office: Days
• US Class Current: 362/231
• 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: H01L 25/0753 the devices being arranged next to each other
• 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: Y10S 362/80 Light emitting diode

Abstract

A lighting apparatus includes a combination of LED dice that emit light of a first color and a wavelength-shifting material (e.g., phosphor) that converts light of the first color to light of a second color. An appropriate combination of light of the first color and light of the second color can be used to produce light of a target color. In an embodiment, LED dice in the lighting apparatus are divided into two groups. Each LED die in the first group is combined with less wavelength-shifting material than needed to produce light of the target color, while each LED die in the second group is combined with more wavelength-shifting material than needed to produce light of the target color. As a result, the two groups produce light having colors on opposite sides of the target color in the International Commission on Illumination (CIE) chromaticity diagram. In some embodiments, the target color and color variations of both groups are on one straight line in the CIE chromaticity diagram, although it is to be understood that there might be small scattering within the groups. By adjusting the relative brightness of the two groups, the target color can be obtained.

Claims

1. A method for making a lighting apparatus, the method comprising:

for an LED die of a plurality of LED dice configured to emit a first color, determining a target amount of a wavelength-shifting material capable of converting light of the first color to light of a second color, wherein the target amount is an amount that, when combined with light from the LED die, will result in light of a third color;

disposing the plurality of LED dice on a substrate to form a lighting apparatus;

depositing less than the target amount of the wavelength-shifting material over each of a first subset of the plurality of LED dice;

depositing more than the target amount of the wavelength-shifting material over each of a second subset of the plurality of LED dice;

coupling the first subset of the plurality of LED dice and the second subset of the plurality of LED dice to a power controller; and

using the power controller to adjust relative brightness of the first subset and the second subset of the plurality of LED dice such that the lighting apparatus is configured to produce light of the third color.

2. The method of claim 1 wherein the wavelength-shifting material is mixed in a base material to form a light-conversion material, and wherein the amount of wavelength-shifting material deposited is controlled by controlling an amount of light-conversion material deposited.

3. The method of claim 1 wherein the wavelength-shifting material is mixed in a base material to form a light-conversion material, and wherein the amount of wavelength-shifting material deposited is controlled by controlling a ratio of the wavelength-shifting material to the base material in the light-conversion material.

4. The method of claim 1 wherein the first color is blue, the second color is yellow, and the third color is white.

5. The method of claim 4 wherein the wavelength-shifting material comprises yellow phosphor.

6. The method of claim 4 wherein the amount less than the target amount is selected such that the LED dice in the first subset is configured to provide cool white light in conjunction with the wavelength-shifting material, and the amount more than the target amount is selected such that the LED dice in the second subset is configured to provide warm white light in conjunction with the wavelength-shifting material.

7. The method of claim 1 wherein the wavelength-shifting material includes yellow and red phosphors.

8. The method of claim 7 wherein the wavelength-shifting material includes yellow and red phosphors at a weight ratio of about 4:

1.

9. The method of claim 7 wherein the wavelength-shifting material includes yellow and red phosphors at a weight ratio of about 20:

1.

10. The method of claim 1 wherein the first color is green, the second color is magenta, and the third color is white.

11. The method of claim 1 wherein the first color is red, the second color is cyan, and the third color is white.

12. The method of claim 1 wherein adjusting relative brightness of the first subset and the second subset of the plurality of LED dice comprises using one or more variable resistances to adjust currents in the first plurality and second plurality of LED dice.

13. A lighting apparatus, comprising:

a first set of one or more light-emitting diode (LED) dice, each configured to emit light of a first color and having a first amount of a complementary wavelength-shifting material disposed thereover, the complementary wavelength-shifting material being configured to convert light of the first color to light of a second color, the first amount being less than an amount required to produce white light in conjunction with light of the first color;

a second set of one or more LED dice, each configured to emit light of the first color and having a second amount of the complementary wavelength-shifting material disposed thereover, the second amount being more than the amount required to produce white light in conjunction with light of the first color; and

a power control circuit coupled to the first set and the second set of LED dice, the power control circuit being configured to control the relative brightness of the first set and the second set of LED dice.

14. The apparatus of claim 13 wherein the wavelength-shifting material is mixed in a base material to form a light-conversion material, and wherein the first set of LED dice and the second set of LED dice have different amounts of the light-conversion material overlaid thereon.

15. The apparatus of claim 13 wherein the wavelength-shifting material is mixed in a base material to form a light-conversion material, and wherein the first set of LED dice and the second set of LED dice have different ratios of the wavelength-shifting material to the base material in the light-conversion material overlaid thereon.

16. The apparatus of claim 13 wherein the first amount of the wavelength-shifting material is an amount that, in conjunction with light from the first set of LED dice, will produce cool white light, and the second amount of the wavelength-shifting material is an amount that, in conjunction with light from the second set of LED dice, will produce warm white light.

17. The apparatus of claim 13 wherein the first color is blue, and the wavelength-shifting material comprises yellow phosphor.

18. The apparatus of claim 13 wherein the first color is green, and the second color is magenta.

19. The apparatus of claim 13 wherein the first color is red, and the second color is cyan.

20. The apparatus of claim 13 wherein the wavelength-shifting material includes yellow and red phosphors.

21. The apparatus of claim 20 wherein the wavelength-shifting material includes yellow and red phosphors at a weight ratio of about 4:

1.

22. The apparatus of claim 20 wherein the wavelength-shifting material includes yellow and red phosphors at a weight ratio of about 20:

1.

23. The apparatus of claim 13 wherein the power control circuit comprises one or more variable resistances for adjusting currents in the first and second sets of LED dice.

24. A lamp for providing white light, the lamp comprising:

a first set of one or more light-emitting diode (LED) dice, each of which is configured to emit light of a first color and has a first amount of a complementary wavelength-shifting material disposed thereover, the first amount being less than an amount required to produce white light in conjunction with light of the first color;

a second set of one or more LED dice, each of which is configured to emit light of the first color and has a second amount of the complementary wavelength-shifting material disposed thereover, the second amount being more than an amount required to produce white light in conjunction with light of the first color;

a primary lens overlying the first set and the second set of LED dice;

a secondary lens overlying the first set and the second set of LED dice and the primary lens, the secondary lens being configured to mix light from the first set and the second set of LED dice at least partially via total internal reflection; and

a power control circuit coupled to the first set and the second set of LED dice, the power control circuit being configured to control the relative brightness of the first set and the second set of LED dice.

25. The apparatus of claim 24 wherein each of the first set of LED dice is configured to produce cool white light, and wherein each of the second set of LED dice is configured to produce warm white light.

26. The apparatus of claim 24 wherein the wavelength-shifting material is mixed in a base material to form a light-conversion material, and wherein the first set of LED dice and the second set of LED dice have different amounts of the light-conversion material overlaid thereon.

27. The apparatus of claim 24 wherein the wavelength-shifting material is mixed in a base material to form a light-conversion material, and wherein the first set of LED dice and the second set of LED dice have different ratios of the wavelength-shifting material to the base material in the light-conversion material overlaid thereon.

28. The apparatus of claim 24 wherein the first amount of the wavelength-shifting material is an amount that, in conjunction with light from the first set of LED dice, will produce cool white light, and the second amount of the wavelength-shifting material is an amount that, in conjunction with light from the second set of LED dice, will produce warm white light.

29. The apparatus of claim 24 wherein the first color is blue, and the wavelength-shifting material comprises yellow phosphor.