Solid state lamp using light emitting strips
In one embodiment, an LED lamp has a generally bulb shape. The LEDs are low power types and are encapsulated in thin, narrow, flexible strips. The LEDs are connected in series in the strips to drop a desired voltage. The strips are affixed to the outer surface of a bulb form to provide structure to the lamp. The strips are connected in parallel to a power supply, which may be housed in the lamp. Since many low power LEDs are used and are spread out over a large surface area, there is no need for a large metal heat sink. Further, the light emission is similar to that of an incandescent bulb. In other embodiment, there is no bulb form and the strips are bendable to have a variety of shapes. In another embodiment, a light sheet is bent to provide 360° of light emission. Many other embodiments are described.
1. A solid state lamp comprising:
a base connector configured to electrically connect the solid state lamp to a power source, the base connector defining an axis; and
a bulb portion extending along the axis and attached to the base connector, the bulb portion comprising a strip, the strip comprising:
an elongate substrate extending from a first end to a second end opposite the first end;
a plurality of spaced-apart light-emitting diode (LED) unpackaged dies;
electrical connectors configured to provide power to the LED unpackaged dies; and
an encapsulant encapsulating the LED unpackaged dies on the substrate,
wherein the substrate comprises a reflective material.
2. The solid state lamp of claim 1 , wherein each of the LED unpackaged dies has a first surface configured to reflect light from within the LED unpackaged die, the first surface facing the substrate.
3. The solid state lamp of claim 1 , wherein the encapsulant comprises a phosphor and a binder.
4. The solid state lamp of claim 3 , wherein the binder comprises a silicone.
5. The solid state lamp of claim 1 , wherein the elongate substrate comprises a dielectric reflective material.
6. The solid state lamp of claim 1 , wherein the elongate substrate comprises a polymer, a glass, or a metal.
7. The solid state lamp of claim 1 , wherein the elongate substrate is a straight elongate substrate.
8. The solid state lamp of claim 1 , wherein the elongate substrate is a curved elongate substrate.
9. The solid state lamp of claim 8 , wherein the curved elongate substrate is a flexible curved substrate.
10. The solid state lamp of claim 1 , further comprising a support structure, wherein the strip is supported by the support structure.
11. The solid state lamp of claim 10 , wherein the support structure comprises wires.
12. The solid state lamp of claim 10 , wherein the strip is coupled to the support structure at at least one end of the strip.
13. The solid state lamp of claim 10 , wherein the support structure comprises a rod.
14. The solid state lamp of claim 10 , wherein the support structure maintains a curved shape of the strip.
15. The solid state lamp of claim 10 , wherein the electrical connectors comprise terminals coupled to the support structure.
16. The solid state lamp of claim 1 , wherein the substrate has a width of less than 5 mm and a thickness of less than 2 mm.
17. The solid state lamp of claim 1 , further comprising one or more additional strips each comprising an elongate substrate extending from a corresponding first end to a corresponding second end opposite said first end, each elongate substrate supporting a corresponding plurality of spaced-apart LED unpackaged dies encapsulated on the elongate substrate.
18. The solid state lamp of claim 17 , wherein the strips are symmetrically distributed around the axis.
19. The solid state lamp of claim 17 , wherein at least one of the additional elongate substrates of the one or more additional strips are straight.
20. The solid state lamp of claim 19 , wherein at least some of the strips are parallel to each other.
21. The solid state lamp of claim 1 , wherein a radial distance between the strip and the axis varies along the axis.
22. The solid state lamp of claim 21 , wherein the radial distance increases closer to the base connector.
23. The solid state lamp of claim 1 , wherein the strip is arranged in the form of a spiral or a helix.
24. The solid state lamp of claim 1 , wherein the LED dies are operatively interconnected without wire bonds.
25. The solid state lamp of claim 1 , wherein the LED unpackaged dies are flip-chip LED dies that are operatively connected via traces.
26. The solid state lamp of claim 1 , wherein the LED unpackaged dies are arranged on the substrate between some of the electrical connectors.
27. The solid state lamp of claim 1 , wherein the LED unpackaged dies are uniformly arranged in a row along the elongate substrate.
28. The solid state lamp of claim 1 , wherein the elongate substrate, the LED unpackaged dies, and the encapsulant are configured to mimic the appearance of a filament in an incandescent light bulb during operation.
29. The solid state lamp of claim 1 , wherein sides of the substrate are exposed along a length of the strip.
30. The solid state lamp of claim 1 , wherein the LED unpackaged dies are disposed on a surface of the elongate substrate and the encapsulant extends only to the edge of the surface.