Light-emitting-diode-based light bulb

1. A light-emitting-diode-based (LED-based) light bulb, comprising:

a bulb;

a housing, wherein the bulb is disposed on the housing;

a base, wherein the housing is disposed on the base, and wherein the base is configured to make electrical contact of a power source; and

an LED assembly, wherein the LED assembly includes an upper substrate for supporting one or more upper LED emitters and a lower substrate for supporting a plurality of lower LED emitters, wherein the lower substrate is at the same level as, or higher than, an interface between the bulb and the housing, and wherein the LED assembly also includes a reflective surface extending between an outer edge of the upper substrate and an inner edge of the lower substrate, wherein the reflective surface is configured to direct at least a portion of light generated by the lower LED emitters toward a backside of the LED-based light bulb, and wherein the reflective surface has a surface profile between the upper substrate and the lower substrate, the surface profile comprising a saw-patterned, or roughened profile, and wherein the inner edge of the lower substrate has a first radius and the outer edge of the upper substrate has a second radius, and wherein a ratio of the first radius to the second radius is in a range from about 0.4 to about 0.95.

2. The LED-based light bulb of claim 1 , wherein the reflective surface and the lower substrate defines an angle ranging from about 30° to about 85° .

3. The LED-based light bulb of claim 1 , wherein a percentage of the upper LED emitters of all LED emitters of the LED-based light bulb is in a range from about 30% to about 50%.

4. The LED-based light bulb of claim 1 , wherein a top surface of the upper substrate has a height above the top surface of the lower substrate, wherein the height is in a range from about 5 mm to about 30 mm.

5. The LED-based light bulb of claim 4 , wherein the bulb has a bulb radius and wherein a ratio of the height to the bulb radius is in a range from about 0.2 to about 0.5.

6. The LED-based light bulb of claim 1 , wherein a portion of the light generated by the lower LED emitters that is reflected by the reflective surface falls in a region between about 135° to about 180° or between about −135° to about −180° from a front center of the LED-based light bulb, and wherein the portion of light is at least 5% of the overall light emitted by the LED-based light bulb.

7. The LED-based light bulb of claim 1 , wherein the lower LED emitters are at least partially covered by the upper substrate when viewed from above the upper substrate.

8. The LED-based light bulb of claim 1 , wherein the shape of the upper substrate comprises circle, rectangle, square, oval, triangle, pentagon, hexagon, or octagon.

9. The LED-based light bulb of claim 1 , wherein the bulb is coated with a layer of phosphor coating, light diffuser coating, or a combination thereof.

10. The LED-based light bulb of claim 1 , further comprising: a cooling device coupled to upper substrate to dissipate heat generated by the upper LED emitters.

11. The LED-based light bulb of claim 1 , further comprising: a cooling device coupled to lower substrate to dissipate heat generated by the lower LED emitters.

12. The LED-based light bulb of claim 1 , further comprising:

an electrical circuit assembly, wherein the electrical circuit assembly adjusts power taken in from the power source to current and/or voltage for lighting the upper and lower LED emitters.

13. The LED-based light bulb of claim 1 , wherein the reflective surface is made of a reflective metal or has a white reflective coating.

14. An LED assembly for an LED-based light bulb, comprising:

an upper substrate for supporting one or more upper LED emitters, wherein the upper substrate has a first radius;

a lower substrate for supporting a plurality of lower LED emitters, wherein the lower substrate has a second radius, and wherein a ratio of the second radius to the first radius is in a range from about 0.4 to about 0.95; and

a reflective surface disposed between the upper substrate and the lower substrate, and wherein an outer edge of the upper substrate is connected to an inner edge of the lower substrate by the reflective surface, and wherein the reflective surface is slanted away from the LED-based light bulb, and wherein the reflective surface reflects light generated by the lower LED emitters toward the backside of the LED-based light bulb.

15. The LED assembly of claim 14 , wherein the reflective surface is at an angle with the top surface of the lower substrate, and wherein the angle is in a range from about 30° to about 85° .

16. The LED assembly of claim 14 , wherein the reflective surface has a surface profile between the upper substrate and the lower substrate selected from a group consisting of saw-patterned and roughened.

17. The LED assembly of claim 14 , wherein the inner edge of the lower substrate has a first radius and the outer edge of the upper substrate has a second radius, and wherein a ratio of the first radius to the second radius is in a range from about 0.4 to about 0.95.

18. An LED assembly for an LED-based light bulb, comprising:

a lower substrate for supporting a plurality of lower LED emitters;

an upper substrate for supporting one or more upper LED emitters, wherein a top surface of the upper substrate has a height above the top surface of the lower substrate, wherein the height is in a range from about 5 mm to about 30 mm;

a reflective surface disposed between the upper substrate and the lower substrate, and wherein an outer edge of the upper substrate is connected to an inner edge of the lower substrate by the reflective surface, and wherein the reflective surface is slanted away from the LED-based light bulb, and wherein the reflective surface reflects light generated by the lower LED emitters toward the backside of the LED-based light bulb; and

a bulb that covers the lower substrate and the upper substrate, wherein the bulb has a shape of a partial sphere having a radius, and wherein a ratio of the height of the upper substrate to the radius of the bulb is in a range from about 0.2 to about 0.5.

19. The LED assembly of claim 18 , wherein the reflective surface has a saw-patterned or roughened surface profile.