Light sources utilizing segmented LEDs to compensate for manufacturing variations in the light output of individual segmented LEDs
View Patent ↗A light source and method for making the same are disclosed. The light source includes a plurality of Segmented LEDs connected in parallel to a power bus and a controller. The power bus accepts a variable number of Segmented LEDs. The controller receives AC power and provides a power signal on the power bus. Each Segmented LED is characterized by a driving voltage that is greater than 3 times the driving voltage of a conventional LED fabricated in the same material system as the Segmented LED. The number of Segmented LEDs in the light source is chosen to compensate for variations in the light output of individual Segmented LEDs introduced by the manufacturing process. In another aspect of the invention, the number of Segmented LEDs connected to the power bus can be altered after the light source is assembled.
1. A light source comprising:
a plurality of Segmented LEDs connected in parallel to a power bus, said bus accepting a variable number of Segmented LEDs, said number being chosen to provide a predetermined brightness for said light source, wherein each Segmented LED is an LED die divided into N segments that are serially connected to one another, and wherein each Segmented LED has an area that is 1/N times an area of a conventional LED; and
a controller that receives AC power and provides a power signal on said power bus.
2. The light source of claim 1 , wherein each Segmented LED is characterized by a driving voltage that is greater than 9.6V.
3. The light source of claim 1 , wherein each Segmented LED generates light at an intensity that is less than 10% of a light intensity generated by said light source.
4. The light source of claim 1 , wherein said power bus includes a breakable link that permanently disconnects one of said Segmented LEDs from said power bus when said link is broken.
5. The light source of claim 4 , wherein said breakable link comprises a region of conductor that is removable by laser ablation.
6. The light source of claim 1 , wherein said power bus includes a switch that disconnects one of said Segmented LEDs in response to a command from said controller.
7. A method for fabricating a light source, said method comprising:
providing a substrate having first and second power rails;
providing a controller that generates a power signal on said first and second power rails;
connecting M Segmented LEDs in parallel between said first and second power rails, each Segmented LED generating an intensity of light within a first predetermined intensity range when powered by said power signal, said first and second power rails accepting a variable number of said Segmented LEDs;
wherein M is chosen to provide a predetermined brightness for said light source, wherein each Segmented LED is an LED die divided into N segments that are serially connected to one another, and wherein each Segmented LED has an area that is 1/N times an area of a conventional LED.
8. The method of claim 7 , further comprising measuring a light output from said light source and altering the number of Segmented LEDs connected to said power rails if said measured light output differs from a target light output.
9. The method of claim 8 , wherein one of said altering includes disconnecting one of said Segmented LEDs from one of said power rails.
10. The method of claim 9 , wherein said one of said Segmented LEDs is permanently disconnected by breaking a link in one of said power rails.
11. A method for fabricating a plurality of light sources having substantially the same target output intensity, said method comprising:
sorting a plurality of Segmented LEDs into a plurality of groups according to a light intensity measured for each Segmented LED, each group being characterized by a mean light intensity and a spread in intensities for that group;
fabricating first and second light sources having said target intensity, said first and second light sources comprising:
a first substrate having first and second power rails;
a controller that generates a power signal on said first and second power rails; and
a plurality of Segmented LEDs from one of said groups connected in parallel between said first and second power rails, said plurality of Segmented LEDs generating a collective light output having an intensity that is substantially said target output intensity,
wherein said first light source comprises Segmented LEDs from a different group than said second light source, and wherein said plurality of Segmented LEDs in said first light source differs in number of Segmented LEDs from said plurality of Segmented LEDs in said second light source.
12. The method of claim 11 , wherein half of the Segmented LEDs from the first or second light source are connected across the first and second power rails in an orientation opposite an orientation of the other half of the Segmented LEDs from the first light source.
13. The method of claim 12 , wherein the controller provides an AC output voltage between the first and second power rails.
14. The method of claim 13 , wherein on each half cycle of an AC power signal, half of the Segmented LEDs generate light while the other half do not generate light.