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Copyright © 2009 Cree, Inc. pg. 1 Lumen Maintenance.

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Presentation on theme: "Copyright © 2009 Cree, Inc. pg. 1 Lumen Maintenance."— Presentation transcript:

1 Copyright © 2009 Cree, Inc. pg. 1 Lumen Maintenance

2 Copyright © 2009 Cree, Inc. pg. 2 Lumen Maintenance Definition Definition: change in light output of a light source over operational life, relative to initially measured light output L xx = time to xx% of original light output L 70 = time to 70% of original light output L 50 = time to 50% of original light output pg. 2

3 Copyright © 2009 Cree, Inc. pg. 3 50,000 Hours Is Trivia Point: 50,000 hours is: 137Years at 1 hour/day 68.5Years at 2 hours/day 34.2Years at 4 hours/day 22.8Years at 6 hours/day 17.1Years at 8 hours/day 11.4Years at 12 hours/day 5.7Years at 24 hours/day pg. 3

4 Copyright © 2009 Cree, Inc. pg. 4 LED Lumen Maintenance History <1990 LEDs were used as indicators. Lifetime did not matter too much Lumileds (Philips) introduces first High Power LED. Lifetime testing gets more serious LRC/ASSIST publishes first work on the topic. Basic science understood LRC/ASSIST publishes ASSIST recommends test procedure for lifetime testing of High Power LEDs, which becomes the basis for IESNA LM standard 2007 Philips Lumileds publishes white paper, extending the knowledge of the industry on the topic (I F ) 2008 IES LM is published 2009 Cree publishes reliability white paper (T AIR ) 1990s LEDs used for traffic signals and exit signs. First basic studies on LED lifetime performed.

5 Copyright © 2009 Cree, Inc. pg. 5 LED Lumen Maintenance Critical Parameters 1. T AIR Ambient Air Temperature 2. T J Junction Temperature 3. T SP / T C / T S Solder-Point Temperature / Case Temperature 4. I F Forward Current / Drive Current

6 Copyright © 2009 Cree, Inc. pg. 6 Cree Lumen Maintenance Model Degradation in first 5,000 hours is mostly due to degradation in the silicone encapsulant. After 5,000 hours, this mechanism drops out and the slower chip degradation dominates. Good quality LEDs in well-designed fixtures will last for decades under normal use and operating conditions.

7 Copyright © 2009 Cree, Inc. pg. 7 How Do You Know They Last >50,000 Hours? L 70 Lifetime Prediction – I F = 350 mA

8 Copyright © 2009 Cree, Inc. pg. 8 L 70 Lifetime Prediction – T AIR = 45ºC

9 Copyright © 2009 Cree, Inc. pg. 9 L 70 Lifetime Prediction – T AIR = 55ºC

10 Copyright © 2009 Cree, Inc. pg. 10 L 70 Lifetime Prediction – I F = 700 mA

11 Copyright © 2009 Cree, Inc. pg. 11 L 70 Lifetime Prediction – I F = 700 mA

12 Copyright © 2009 Cree, Inc. pg. 12 L 70 Lifetime Prediction – I F = 1000 mA

13 Copyright © 2009 Cree, Inc. pg. 13 Low temp (25ºC) testing is a good surrogate for the LED chip depreciation – T J = 65ºC 40,000 Hour / 4.5 Year XLamp Long-Term Data At lower ambient air temperature, LEDs hardly depreciate at all. pg. 13

14 Copyright © 2009 Cree, Inc. pg. 14 System Lifetime is What Counts System Lifetime is What Creates Value LED Lamps: Practically never fail; depreciate very slowly in a well-designed system Optical Components: Can (rarely) yellow over time and lose light; system design choice Driver: Much improvement on rel and performance especially with the large suppliers. Heat Sink: Linchpin of the entire system. If this is poorly designed, all the other components can be compromised

15 Copyright © 2009 Cree, Inc. pg. 15 Binning

16 Copyright © 2009 Cree, Inc. pg. 16 What is LED binning? Used to define similar groups of parts by performance characteristics Not unlike other industries that bin based on performance, ie: microprocessor Cree XLamp ® LED binning based on two parameters: –Flux (total light output) –Chromaticity (white), Dominant wavelength (color) Even fluorescent tubes are binned by chromaticity –daylight, warm white, etc.

17 Copyright © 2009 Cree, Inc. pg. 17 Two Main Types of Binning Brightness or Flux Binning – Minimum luminous flux or radiant Flux – Bin sizes (flux range) varies by supplier Chromaticity or Color Binning – Some defined Box in the white area on or near the Black Body Locus (White LEDs) – Dominant Wavelength (Color LEDs)

18 Copyright © 2009 Cree, Inc. pg. 18 Brightness or Flux Binning Flux = total light emitted in all directions Measured using an integrating sphere

19 Copyright © 2009 Cree, Inc. pg. 19 Luminous Flux Binning LEDs are tested & sorted into luminous flux bins Performance binning is very standard in the semiconductor industry (e.g., CPUs), but confusing to the lighting industry where performance is very standardized lm Driver 350 mA Flux:

20 Copyright © 2009 Cree, Inc. pg. 20 Chromaticity Binning Driver 350 mA CCy: 0.35 CCx: 0.32

21 Copyright © 2009 Cree, Inc. pg. 21 Design & Specification Strategies Insist on the tightest bin available Pay the highest price possible Strategy #1 Understand light, binning, and your application needs Do the mixing yourself in your fixture if the application will allow it Save money Strategy #2

22 Copyright © 2009 Cree, Inc. pg. 22 Let Cree do the mixing for you...EasyWhite Consistent color No complicated mixing recipes Reduced inventory Ease of manufacturing Strategy #3 Design & Specification Strategies

23 Copyright © 2009 Cree, Inc. pg. 23 EasyWhite


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