Shallow reflector cup for phosphor-converted LED filled with encapsulant
An LED die conformally coated with phosphor is mounted at the base of a shallow, square reflector cup. The cup has flat reflective walls that slope upward from its base to its rim at a shallow angle of approximately 33 degrees. A clear encapsulant completely fills the cup to form a smooth flat top surface. Any emissions from the LED die or phosphor at a low angle are totally internally reflected at the flat air-encapsulant interface toward the cup walls. This combined LED/phosphor light is then reflected upward by the walls and out of the package. Since a large percentage of the light emitted by the LED and phosphor is mixed by the TIR and the walls prior to exiting the package, the color and brightness of the reflected light is fairly uniform across the beam. The encapsulant is intentionally designed to enhance TIR to help mix the light.
1. A light emitting device comprising:
a reflective cup comprising a specular material and having reflective surfaces that slope monotonically upward from a central portion of the cup at an angle between 28 degrees and 38 degrees;
a light emitting diode (LED) die mounted in the central portion of the cup and emitting a first light of a first wavelength;
a phosphor positioned over the LED die; and
a clear encapsulant filling the cup to cover at least a top of the phosphor coating, the encapsulant having a flat outer surface substantially parallel to a top surface of the LED die,
wherein the phosphor absorbs a portion of the first light and emits a second light of a second wavelength,
wherein the encapsulant has an air-encapsulant interface arranged such that at least a portion of the first light unabsorbed by the phosphor coating and at least a portion of the second light intercept the air-encapsulant interface at an angle less than a critical angle and are totally internally reflected (TIR) as a first reflected light in a direction toward at least one of the reflective surfaces,
wherein the reflective surfaces reflect the first reflected light as a second reflected light in a direction that passes through the air-encapsulant interface.
2. The device of claim 1 , wherein the cup comprises a rectangular aperture.
3. The device of claim 1 , wherein the specular material comprises a coating of the cup.
4. The device of claim 1 , wherein the LED die emits blue light and wherein the phosphor emits a light that, combined with the blue light, creates a white light.
5. The device of claim 1 , wherein at least a portion of the first light unabsorbed by the phosphor and at least a portion of the second light exit the encapsulant after a maximum of a single reflection off the air-encapsulant interface and a single reflection off the reflective surfaces.
6. The device of claim 1 , wherein the cup comprises a metal film.
7. The device of claim 1 , wherein the cup comprises plastic molded around a lead frame.
8. The device of claim 1 , wherein the cup comprises a diffusing material.
9. The device of claim 1 , wherein the specular material comprises a reflective metal.
10. A light emitting device, comprising:
a reflective cup which comprises a specular material and reflective surfaces sloping monotonically upward from a central area of the cup at an angle between 28 degrees and 38 degrees;
a light emitting diode (LED) mounted in the cup and configured to emit a first light of a first wavelength;
a phosphor material mounted in the cup and configured to absorb a portion of the first light and emit a second light of a second wavelength;
an encapsulant filling the cup to a level covering at least a top surface of the phosphor material, the encapsulant comprising an air-encapsulant interface configured such that at least a portion of the first light unabsorbed by the phosphor material and at least a portion of the second light intercept the air-encapsulant interface at an angle less than a critical angle and are reflected toward at least one of the reflective surfaces as reflected light, the reflective surfaces configured to reflect at least a portion of the reflected light toward the air-encapsulant interface.
11. The device of claim 10 , wherein the cup comprises a rectangular aperture.
12. The device of claim 10 , wherein the specular material comprises a coating of the cup.
13. The device of claim 10 , wherein the LED is configured to emit blue light and wherein the phosphor is configured to emit a light that, combined with the blue light, creates a white light.
14. The device of claim 10 , wherein at least a portion of the first light unabsorbed by the phosphor coating and at least a portion of the second light exit the encapsulant after a maximum of one reflection off the air-encapsulant interface and one reflection off one of the reflective surfaces.
15. The device of claim 10 , wherein the cup comprises a metal film.
16. The device of claim 10 , wherein the cup comprises plastic molded around a lead frame.
17. The device of claim 10 , wherein the cup comprises a diffusing material.
18. The device of claim 10 , wherein the specular material comprises a reflective metal.