Semiconductor light emitting devices having selectable and/or adjustable color points and related methods
Semiconductor light emitting devices include a first string of at least one blue-shifted-yellow LED, a second string of at least one blue-shifted-green LED, and a third string of at least one LED that emits light in the red color range. These devices include at least a first circuit that is configured to provide an operating current to at least one of the first LED or the second LED and a second circuit that is configured to provide an operating current to the third light source. The drive currents supplied by the first and second circuits may be independently controlled to set a color point of the light emitting device at a desired color point.
1. A light emitting device, comprising:
a first string of at least one light emitting diode (“LED”);
a second string of at least one LED;
a third string of at least one LED;
a drive circuit that is configured to set the relative drive currents provided to the first string and to the second string so that the color point on the 1931 CIE Chromaticity Diagram of the combined output of the first string and the second string is approximately on a line that extends on the 1931 CIE Chromaticity Diagram through a pre-selected color point and a color point of an output of the third string, and that is further configured to set the relative drive currents provided to the third string relative to the drive currents provided to the first and second strings so that the color point on the 1931 CIE Chromaticity Diagram of the combined output of the light emitting device is approximately at the pre-selected color point
wherein one of the first through third strings includes at least one blue-shifted-yellow LED, and wherein one of the first through third strings of LEDs includes at least one blue-shifted-green LED.
2. The light emitting device of claim 1 , wherein the first string of LEDs includes the at least one blue-shifted-yellow LED, and wherein the second string of LEDs includes the at least one blue-shifted-green LED.
3. The light emitting device of claim 2 , wherein the third string includes at least one LED that emits radiation having a spectral power distribution that has a peak with a dominant wavelength between 600 and 660 nm.
4. The light emitting device of claim 3 , wherein the color point on the 1931 CIE Chromaticity Diagram of the combined output of the light emitting device is within three MacAdam ellipses from the pre-selected color point.
5. A method of tuning a multi-emitter semiconductor light emitting device to a desired color point, the method comprising:
setting the relative drive currents provided to a first string of at least one light emitting diode (“LED”) and to a second string of at least one LED so that the color point on the 1931 CIE Chromaticity Diagram of the combined output of the first string and the second string is approximately on a line that extends on the 1931 CIE Chromaticity Diagram through the desired color point and a color point of a combined output of a third string of at least one LED; and
setting a drive current provided to the third string of at least one LED so that the color point on the 1931 CIE Chromaticity Diagram of the combined output of the multi-emitter semiconductor light emitting device is approximately at the desired color point
wherein one of the first through third strings of LEDs includes at least one blue-shifted-yellow LED, and wherein one of the first through third strings of LEDs includes at least one blue-shifted-green LED.
6. The method of claim 5 , wherein the first string of LEDs includes the at least one blue-shifted-yellow LED, and wherein the second string of LEDs includes the at least one blue-shifted-green LED.
7. The method of claim 6 , wherein the color point on the 1931 CIE Chromaticity Diagram of the combined output of the multi-emitter semiconductor light emitting device is within three MacAdam ellipses from a selected color point on the black-body locus.
8. The method of claim 5 , wherein the third string of at least one LED includes at least one LED that emits radiation having a spectral power distribution that has a peak with a dominant wavelength between 600 and 660 nm.
9. A semiconductor light emitting device, comprising:
a first light emitting diode (“LED”) that emits radiation having a peak wavelength between 400 and 490 nm that includes a first recipient luminophoric medium, wherein a color point of the combined light output of the first LED and the first recipient luminophoric medium falls within the region on the 1931 CIE Chromaticity Diagram defined by x, y chromaticity coordinates (0.32, 0.40), (0.36, 0.48), (0.43 0.45), (0.36, 0.38), (0.32, 0.40);
a second LED that emits radiation having a peak wavelength between 400 and 490 nm that includes a second recipient luminophoric medium, wherein a color point of the combined light output of the second LED and the second recipient luminophoric medium falls within the region on the 1931 CIE Chromaticity Diagram defined by x, y chromaticity coordinates (0.35, 0.48), (0,26, 0.50), (0.13 0.26), (0.15, 0.20), (0.26, 0.28), (0.35, 0.48);
a third light source that emits radiation having a dominant wavelength between 600 and 720 nm;
a first circuit that is configured to provide an operating current to at least one of the first LED or the second LED; and
an independently controllable second circuit that configured to provide an operating current to the third light source.
10. The semiconductor light emitting device of claim 9 , wherein the first circuit is configured to provide an operating current to the first LED, and wherein the semiconductor light emitting device further includes a third circuit that is configured to provide an operating current to the second LED.
11. The semiconductor light emitting device of claim 10 , wherein the first, second and third circuits are controllable such that they can provide different operating currents to the respective first LED, second LED and third light source.
12. The semiconductor light emitting device of claim 11 , wherein the third light source comprises an InAlGaP based LED.
13. The semiconductor light emitting device of claim 11 , wherein the third light source comprises a third LED that emits radiation having a peak wavelength between 400 and 490 nm that includes a third recipient luminophoric medium that emits radiation having a dominant wavelength between 600 and 660 nm.
14. The semiconductor light emitting device of claim 11 , further comprising a fourth LED that emits radiation having a dominant wavelength between 490 and 515 nm.
15. The semiconductor light emitting device of claim 14 , wherein one of the first circuit or the second circuit is further configured to provide an operating current to the fourth LED.
16. The semiconductor light emitting device of claim 11 , wherein the first, second and third circuits are configured to deliver operating currents to the respective first LED, the second LED and the third light source that cause the semiconductor light emitting device to generate radiation that is within three MacAdam ellipses from a selected color point on the black-body locus.
17. The semiconductor light emitting device of claim 10 , further comprising:
at least one additional first LED that emits radiation having a peak wavelength between 400 and 490 nm that includes another first recipient luminophoric medium, wherein a color point of the combined light output of the at least one additional first LED and the another first recipient luminophoric medium falls within the region on the 1931 CIE Chromaticity Diagram defined by x, y chromaticity coordinates (0.32, 0.40), (0.36, 0.48), (0.43 0.45), (0.36, 0.38), (0.32, 0.40);
at least one additional second LED that emits radiation having a peak wavelength between 400 and 490 nm that includes another second recipient luminophoric medium, wherein a color point of the combined light output of the at least one additional second LED and the another second recipient luminophoric medium falls within the region on the 1931 CIE Chromaticity Diagram defined by x, y chromaticity coordinates (0.35, 0.48), (0.26, 0.50), (0.13 0.26), (0.15, 0.20), (0.26, 0.28), (0.35, 0.48);
at least one additional third light source that emits radiation having a dominant wavelength between 600 and 660 nm;
wherein the first circuit is configured to provide an operating current to the first LED and the at least one additional first LED;
wherein the third circuit is configured to provide an operating current to the second LED and the at least one additional second LED; and
wherein the second circuit is further configured to provide an operating current to the at least one additional third light source.
18. The semiconductor light emitting device of claim 10 , wherein the semiconductor light emitting device emits a warm white light having a correlated color temperature between about 2500K and about 4100K and a CRI Ra value of at least 90.
19. A semiconductor light emitting device, comprising:
a first light emitting diode (“LED”) string that includes at least one first type of LED;
a second LED string that includes at least one second type of LED;
a third LED string that includes at least one third type of LED;
a circuit that allows an end user of the semiconductor light emitting device to adjust the relative values of the drive current provided to the LEDs in the first and second LED strings to adjust a color point of the light emitted by the semiconductor light emitting device.
20. The semiconductor light emitting device of claim 19 , wherein:
the at least one first type of LED comprises an LED that emits radiation having a peak wavelength between 400 and 490 nm that includes a first recipient luminophoric medium, wherein a color point of the combined light output of the at least one first type of LED and the first recipient luminophoric medium falls within the region on the 1931 CIE Chromaticity Diagram defined by the following x, y chromaticity coordinates: (0,32, 0.40), (0.36, 0.48), (0.43 0.45), (0.36, 0.38), (0.32, 0.40);
the at least one second type of LED comprises an LED that emits radiation having a peak wavelength between 400 and 490 nm that includes a second recipient luminophoric medium, wherein a color point of the combined light output of the at least one second type of LED and the second recipient luminophoric medium falls within the region on the 1931 CIE Chromaticity Diagram defined by the following x, y chromaticity coordinates: (0.35, 0.48), (0.26, 0.50), (0.13 0.26), (0.15, 0.20), (0.26, 0.28), (0.35, 0.48);
the at least one third type of LED comprises an LED that has one or more emission peaks that includes an emission peak having a dominant wavelength between 600 and 720 nm.
21. The semiconductor light emitting device of claim 20 , wherein the circuit that allows an end user of the semiconductor light emitting device to adjust the relative values of the drive current provided to the LEDs in the first and second LED strings is configured to keep the overall luminous flux output by the semiconductor light emitting device relatively constant.
22. The semiconductor light emitting device of claim 19 , wherein the circuit comprises a first circuit, and wherein the device further includes a second circuit that allows an end user of the semiconductor light emitting device to adjust the amount of drive current provided to the LEDs in the first and second LED strings relative to the drive current provided to the LEDs in the third LED string.
23. The semiconductor light emitting device of claim 22 , wherein the circuit is configured to adjust the amount of drive current provided to the LEDs in the first through third strings of LEDs to one of a plurality of pre-defined levels that correspond to pre-selected color points.