SCALING UP: KiloLumen Solid-State Lighting Exceeding 100 LPW via Remote Phosphor
Investigating Organization
Light Prescriptions Innovators, LLC
Principal Investigator(s)
Mr. Waqidi Falicoff
Subcontractor
Fisk University
L&L Optical Services
Lawrence Berkeley National Laboratory–Lighting Research Group
LPI Precision Optics LTD
Northeast Photosciences
Osram Opto Semiconductors Inc.
University of California, Merced–Center for Nonimaging Optics
Funding Source
Building Technologies Program/NETL
Award
DOE Share: $1,156,644; Contractor Share: $291,829
Contract Period
04/11/05 - 09/15/08
Light Prescriptions Innovators, LLC (LPI) of Irvine, California, a nonimaging optics R&D company with wide experience in LED lighting optical design, proposes to team with LED chip-making giant OSRAM Opto Semiconductors, Lawrence Berkeley National Laboratory, University of California, Merced, and Fisk University, in a collaborative project applying for DOE funding. The project objective is to apply new technologies to fabricate a prototype that can prove that mass-produced high-flux LED modules can compete with fluorescent, incandescent and halogen lighting in efficacy, flux, and cost/watt.
LPI and OSRAM plan to break through the limits formerly holding back makers of LEDs (Light Emitting Diodes) seeking to create general illumination sources using white Solid-State Lighting (SSL). The most popular method being used today is by coating a blue LED with a phosphor coating. When the blue light hits the phosphor, it glows white.
Some of the drawbacks with this method are that the LED heats up and can damage the longevity of the phosphor conversion and, therefore, the life of the LED. Also, the efficiency of the LED suffers because half of the phosphor's omni directional emission goes back toward the LED chip. Much of this light gets trapped in the LED package and is reabsorbed by the chip, causing it to heat up even more than it did by the initial blue light production.
There is a further inefficiency in the conventional set-up, one that is also suffered by single-color LEDs. That is, if you try to gang several adjacent LEDs to act as a single light source, the great heat load is difficult to remove. This, in turn, prevents the higher currents possible with one chip alone.
What is proposed by the LPI/OSRAM team is to optically unite a number of separate, top-emitting OSRAM ThinGaN blue LEDs, using LPI's patent pending "combiner" optics that feed an exit aperture coated with phosphor. This avoids the separated chips heating each other. Also, the phosphor is far removed from the source of the heat that can reduce its efficiency, or even damage it. Further, part of the white light that tries to go back to the source will be recycled by special optics, which increases efficacy and alleviates overheating of the LED chip. The result is that the chip can now be driven harder and generate more light. A side benefit is that the proposed optics homogenizes the light, so that variations of phosphor brightness and color are minimized, in the case of flux reductions, or even a total failure, of an LED in the array.