Friday, 19 March 2010

Tighter binning yields more consistent HB LEDs for indoor apps - PowerSource - Blog on EDN - 1470000147

Tighter binning yields more consistent HB LEDs for indoor apps - PowerSource - Blog on EDN - 1470000147: "Thursday, December 10, 2009
Tighter binning yields more consistent HB LEDs for indoor apps

Dec 10 2009 11:54AM | Permalink |Comments (3) |

HB (high-brightness) LED vendors make white HB LEDs by taking a blue LED and dosing it with a blob of phosphor that emits white light when illuminated by blue light. If cost were no object a manufacturing process could precisely control the LED chip/phosphor combination to get a completely consistent white light color temperature, but that level of control is prohibitively expensive. However, HB LED vendors do provide LEDs that fall within certain color ranges. These ranges are called color bins, and the process is called binning. If your end-fixture uses multiple LEDs, a common design technique for outdoor lights such as street lamps, the lighting will be consistent as the LEDs’ color temperature will average out. However, not all indoor applications have the space to allow multiple LEDs. Applications such as track or spot lighting or can lights may use a single HB LED, and the variation in light color temperature can be visible -- and irritating.

Cree has announced EasyWhite bins in 3500 K, 3000 K and 2700 K color temperatures that are 75 percent smaller than standard color regions. (See the binning diagram below.) Cree then uses EasyWhite LED chips in its multichip XLamp MC-E LEDs to obtain a more consistent white color temperature in a single LED package, which can serve as a replacement for 20 -- 35-watt halogen light bulbs in indoor lighting applications such as accent, track and pendant lighting. The XLamp MC-E EasyWhite LED, at 3000 K CCT, can produce up to 560 lumens when driven at 700 mA. EasyWhite LEDs have about a 15% premium over Cree’s standard-bin LEDs.

Cree EasyWhite binning"

Cree R&D LED reaches 186 lumens per Watt - PowerSource - Blog on EDN - 1470000147

Cree R&D LED reaches 186 lumens per Watt - PowerSource - Blog on EDN - 1470000147 Tuesday, December 1, 2009
Cree R&D LED reaches 186 lumens per Watt

Dec 1 2009 9:35AM | Permalink |Comments (8) |

Cree's tests for the R&D device showed that the LED produced 197 lumens of light output and achieved 186 lumens per watt efficacy at a correlated color temperature of 4577K. The tests were conducted under standard LED test conditions at a drive current of 350mA, at room temperature. Cree says the 186 lumens/W is the highest in the industry to date. In the past, Cree has said that it generally takes only about 12 months before a lab-level LED is commercialized; Early 2011 for a product version?