Download - Cree Presentation LED
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Copyright 2009 Cree, Inc. pg. 1
Lumen Maintenance
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Copyright 2009 Cree, Inc. pg. 2
Lumen Maintenance Definition
Definition: change in light output of a light source over operationallife, relative to initially measured light output
Lxx= time to xx% of original light output
L70= time to 70% of original light output
L50= time to 50% of original light output
pg. 2
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Copyright 2009 Cree, Inc. pg. 3
50,000 Hours Is
Trivia Point: 50,000 hours is:
137 Years at 1 hour/day
68.5 Years at 2 hours/day
34.2 Years at 4 hours/day
22.8 Years at 6 hours/day17.1 Years at 8 hours/day
11.4 Years at 12 hours/day
5.7 Years at 24 hours/day
pg. 3
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LED Lumen Maintenance History
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LED Lumen Maintenance Critical Parameters
1. TAIRAmbient Air Temperature
2. TJJunction Temperature
3. TSP/ TC/ TSSolder-Point Temperature /Case Temperature
4. IFForward Current /Drive Current
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Copyright 2009 Cree, Inc. pg. 6
Cree Lumen Maintenance Model
Degradation in first 5,000 hours is mostly due to degradation inthe silicone encapsulant.
After 5,000 hours, this mechanism drops out and the slower chipdegradation dominates.
Good quality LEDs in well-designed fixtures will last for decades
under normal use and operating conditions.
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Copyright 2009 Cree, Inc. pg. 7
How Do You
Know TheyLast >50,000
Hours?
L70Lifetime PredictionIF= 350 mA
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L70Lifetime PredictionTAIR= 45C
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L70Lifetime PredictionTAIR= 55C
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L70Lifetime PredictionIF= 700 mA
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L70Lifetime PredictionIF= 700 mA
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L70Lifetime PredictionIF= 1000 mA
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Low temp (25C) testing is a good surrogate forthe LED chip depreciation1-2% @ TJ= 65C
40,000 Hour / 4.5 Year XLamp Long-Term Data
At lower ambient air temperature, LEDs hardly depreciate at all.
pg. 13
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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 especiallywith the large suppliers.
Heat Sink: Linchpin of the entire system.
If this is poorly designed, all the other
components can be compromised
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Binning
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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.
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Two Main Types of Binning
Brightness or Flux Binning
Minimum luminous flux orradiant Flux
Bin sizes (flux range)varies by supplier
Chromaticity or Color Binning
Some defined Boxin thewhite area on or near theBlack Body Locus (White LEDs)
Dominant Wavelength (ColorLEDs)
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Brightness or Flux Binning
Flux = total light emitted in all directions
Measured using an integrating sphere
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Luminous Flux Binning
LEDs are tested & sorted into luminous flux bins
Performance binning is very standard in the semiconductorindustry (e.g., CPUs), but confusing to the lighting industry whereperformance is very standardized
102.3 lm
Driver
350 mA
Flux:
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Chromaticity Binning
Driver350 mA
CCy: 0.35
CCx: 0.32
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Design & Specification Strategies
Insist on the tightest binavailable
Pay the highest pricepossible
Strategy #1
Understand light, binning,and your application needs
Do the mixing yourself inyour fixture if theapplication will allow it
Save money
Strategy #2
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Let Cree do the mixing for
you...EasyWhite Consistent color
No complicated mixing recipes
Reduced inventory
Ease of manufacturing
Strategy#3
Design & Specification Strategies
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EasyWhite