Technical Insight
LumiLeds demonstrates high-power LEDs (LED News)
LumiLeds Lighting (San Jose, CA) has announced record results from its high-power monochrome and white InGaN-based LEDs, enabled by a combination of developments in large area, high-current chips, as well as light extraction and packaging. The results build on LumiLeds previous announcements in this area (see Compound Semiconductor December 2000/January 2001, p19). The company will shortly introduce these devices as part of its Luxeon family of high-power LEDs. "These are the most efficient, highest flux, large junction devices in the world," said Frank Steranka, LumiLeds materials R&D and product development manager. "Where the rest of the world is talking about 1 lumen devices, we are exhibiting up to 55 lumen devices in certain colors." LumiLeds say the higher flux devices could find use as backlighting for LCD computer monitors and TVs. The use of LEDs could lend these applications brighter colors than the conventional backlight sources, and better power consumption than a CRT. Flashlights that use single high-power LEDs with outputs of 2550 lm are also expected to be on the market within the next year. One of LumiLeds recent demonstrations was a single white LED with a light output of 17 lm, a value that is four times greater than the best commercially available white LED (see ). This device features high current operation at 350 mA and a forward voltage of just 3.2 V. This is a significant achievement as it is the first single point white LED in the light output range required for general lighting applications such as map lights, airplane reading lights and emergency lighting. A well-controlled single point light source allows lighting designers to construct compact fixtures and couple the light to a single optic in the light fixture. This approach is not possible with conventional 5 mm white LEDs which do not provide enough light on their own, necessitating bulky designs with multiple LEDs. LumiLeds also announced a laboratory demonstration of a 425 nm InGaN LED (250 mA DC operation) with a wallplug efficiency of 25%, exceeding the prev-ious record from Cree Lighting of 22% (see Compound Semiconductor August 2000, p25). The wallplug efficiency is the ratio of the light output against the energy input, and is a measure of the amount of energy required to produce the specified light output level. According to LumiLeds, one of the keys to keeping energy requirements low is to retain a low forward voltage. LumiLeds device can be driven at much higher currents: overall, the new high-power device emits over 200 mW, 10 times higher than previous devices. At a current of 1 A, the company has demonstrated over 525 mW of output power.
