100,000 Hour Lifetimes And Other LED Fairytalesledtransformations.com/Lightfair_5-28-08.pdf© 2008...

© 2008 LED Transformations, LLC.

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100,000 Hour LifetimesAnd Other LED Fairytales

May 28, 20082:00 PM

Dr. John W. Curran, PresidentShawn P. Keeney, Vice President

LED Transformations, LLC

Your Guide to Solid State Lighting


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1. Introduction2. Terminology3. Measurements4. LED Drivers5. Thermal6. LED Lifetimes7. Color8. Lighting Systems9. LED Economics10. Summary11. Questions

Course Outline


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Fairytale

Attendees of this course will come away with all the knowledge of LEDs they

will ever need

LED light came to town,A-bragging ‘bout its bennies Tripped up many an architect

Who now serve meals at Dennys.

Introduction


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Some LED Milestones

1962 First LED (Holonyak at GE) 0.001 lumens

1960’s Red LEDs (HP & Monsanto) 0.01 lumens

1970’s First consumer products - Watches, calculators

1980’s Green LEDs 0.1 lumens

1990’s Blue LEDs (Nakamura at Nichia) 1 lumen

2000’s High flux packages 100+ lumens

Introduction


5N-Type Dopants

P-Type Dopants

Base Elements

51 Sb Antimony 121.760

50 Sn

Tin 118.710

49 In Indium 114.818

33 As Arsenic 74.921

32 Ge

Germanium 72.61

31 Ga Gallium 69.723

15 P

Phosphorus 30.973

14 Si Silicon 28.0955

13 Al

Aluminum 126.981

7 N

Nitrogen 14.006

6 C Carbon 12.0107

5 B Boron 10.811

Group VAGroup IVAGroup IIIA

AlInGaP

AlInGaN

LED Composition

Introduction


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N Type P Type

Free electrons

Donor atoms

Acceptor atoms

Free holes N Type P Type

Depletion Zone

Junction

{What is a diode?

Anode Cathode

Introduction


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electron

hole

photon

Photon Generation

Introduction


8

Phonon (Heat) Generation

Introduction


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Typical constructionfor a 5mm LED

Typical construction for a

High Flux LED

Typical Flux = 3 lm Typical Flux > 75 lmNumber of LEDs to equal theoutput of a 60W incandescent

light bulb > 250

Number of LEDs to equal theoutput of a 60W incandescent

light bulb < 12

Construction

Silicone Encapsulant

Plastic Case

Gold Wire

Cathode

Lens

LED Chip

Heatsink Slug

Cathode

LED Chip

Gold Wire

Anode

Epoxy Lens

Reflector Cup

Silicone Encapsulant

Introduction


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Fairytale

In the world of LEDs, everyonespeaks the same language

Mary, Mary quite contrary How does your garden glow?

With quantum wells and electron shells And LEDs all in a row.

Terminology


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Terms—Flux• Standard Candle—a candle which emits uniform

luminous intensity in all directions of one candlepower

• Lumen—rate at which luminous flux falls on a one foot square surface of a unit sphere from a uniform source of one candela located at the center of the sphere. The standard candle emits 4π lumens

• Luminous Flux (φ)—rate of flow of luminous energy given by

φ = dQ / dt (in lumens, lm)Where Q is the luminous energy

Terminology


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Blackbody Radiator is a device that absorbs all electro-magnetic radiation that falls on it. Its emissivity is equal to 1.

Planck’s Radiation Law describes the radiationemitted from a blackbody radiator.

U(λ,T) = 8πhcλ-5 / [ehc/λkT – 1]where U(λ,t) = Spectral Energy Densityλ = wavelength (in meters)T = temperature (in degrees Kelvin)c = 3.0 x 108 m/sec (Speed of Light)h = 6.63 x 10-34 Joule sec (Planck’s Constant)k = 1.38 x 10-23 Joule/K (Boltzmann’s Constant)

Terminology


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Terminology

1 400 500 600 700 800 Wavelength λ (in nm)

0.0

0.

2

0.4

0.6

0

.8

1.0

1

.2

1.4

1

.6

1.8

1931

Eye Response

1978

Color Matching Functions(from 1931 & 1978 CIE)

X

YZ


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X, Y and Z are the spectral responsecurves for the three different conereceptors in the eye. If the eyeresponse to a color stimulus is givenby X, Y and Z, we can define a colorcoordinate system as the relativestimulus given by the following equations: With X + Y + Z = 1 by definition only two coordinates are necessary to define a color.

x =X y =

z =

Y

Z

X + Y + Z X + Y + Z

X + Y + Z

Spectral Response

CIE Chart (1931)

Definitions - ColorTerminology

X

Y


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0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

400 450 500 550 600 650 700Wavelength (nm)

Photopic Eye ResponseRadiometric Flux to Luminous Flux

Terminology


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Color is not important in all lighting environments

Color ImportantColor Not Important

Rods Dominant

Cones Dominant

Scotopic Regime

Mesopic Regime

Photopic Regime

10-6

10-5

10-4

10-3

10-2

10-1

101

102

103

104

105

1 106

Luminance (cd/m2)

No moon Full Moon Twilight Office Full Sun

Terminology


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• Forward Voltage Vf is roughly equal to thebandgap energy of the LED semiconductordivided by the elementary charge

Vf = Eg / qwhere q =1.6 x 10-19 coulombs

• Output Intensity of typical high brightness LEDs is dependent on theForward Current If

Forward VoltageTerminology


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Bandgap Energies, Lattice Constants and Vf

Figure courtesy Ian Ferguson, Georgia Tech

Terminology

Figure from “Light Emitting Diodes, 2nd edby E. Fred Schubert

Blue, green and white LEDsgenerally have higher forwardvoltages than do amber, orangeand red


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Fairytale

One + One + One = Three

One, two, more lux or fewThree, four, light on the floor

Five, six, LED flux basicsSeven, eight, do not equateNine, ten, lamp output again

Measurements


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Open fixture (no lens) using 10 LEDs; each LED having a rating of 80 lum/W (@350mamp) and driven at 700 mampYou could just:

Power = Vf x I = 3.2 volts x 0.7amps = 2.24WLight Output = 80 lum/W x 2.24W = 179.2 lumensTotal Light Output = 10 x 179.2 lumens = 1792 lumensInput Power = 10 x 2.24W = 22.4W with a luminaire efficiency = 80 lum/W

BUT YOU WOULD BE WRONG! Why?

Most high power LED manufacturers measurelight output under the following conditions: Junction Temperature 25oC Input current 350 mamps (pulsed)

How does this measurement relate to the real world?

MeasurementsWhat is my light output giventhe following conditions:

Inpu

t Cur

rent

(in

mam

ps)

Time (in sec)

Input Current vs. Time


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• Ambient temperature greater than 25oC will result in lower light output

– Some nighttime outdoor and refrigerated indoor applications may benefit

• Applications will have a duty cycle greater than 2.5%– Higher junction temperature

• LED output goes down as current goes up

• Drivers which power the LEDs lower system efficiency

– Most drivers have efficiencies <90%For the previous example, total light output would be:

10 LEDs x 80 lum/W * 2.24W * 0.75 x 0.84 = 1,129 lumInput power = 10 * 2.24W / 0.9 = 24.9Yielding a luminaire efficiency of 45.3 lum/W

MeasurementsReal World Conditions

Osram Golden Dragon

1.5

84%

350 mamp

700 mamp


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DOE CALiPER Program

“For a number of products, manufacturers publish the LED luminous efficacy (lamp efficacy) and expected lumen output levels based on the LED lamp performance. This could be misleading because the actual measured luminaire efficacy is far less than the LED lamp efficacy (on average, about 1/3 of the LED luminous efficacy).”Source: DOE Solid-State Lighting Commercial Product Testing Program (Round 1—March 2007) p. 5

“For the other nine SSL products [out of 15 tested], information published by the manufacturers regarding product output and/or efficacy overstated performance (by factors ranging from 30 – 600%).”Source: DOE Solid-State Lighting Commercial Product Testing Program (Round 4—January 2008) p. 6

Type of Fixture Light Output (lumens)

Mfg's Published Efficacy (lm/W)

DOE Measured Efficacy (lm/W)

CPTP-06-01 Downlight 193 40 12.82

CPTP-06-02 Under-Cabinet Light 166 55 16.07

CPTP-06-03 Downlight 298 45 19.3

CPTP-06-04 Task Light 114 36 11.6

CPTP-06-05 Outdoor Area Light 2638 24 23.9

Measurements


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On the Other hand—Luminaire Efficiency

The small source (die) size allows for much better control of light output from LED sources as compared with other conventional light sources

LED Sources (75 lum/W)CU = 90%; Driver = 85%; Thermal = 90%Luminaire efficiency = 52 lum/W

Incandescent Source (17 lum/W)CU = 60%

Luminaire efficiency = 10 lum/W

This allows for design of luminaires utilizing sources with less luminousflux (LEDs) that produce higher illuminance on a given surface thanconventional light sources

Measurements


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Some interesting points from LM-79-08:

“For the purpose of rating new SSL products, SSL products shall be tested with no seasoning.”

“The SSL product under test shall be evaluated in the operating orientation recommended by the manufacturer for an intended use of the SSL product.”

“Goniophotometers shall be the type that maintains the burning position unchanged with respect to gravity; therefore only Type C goniophotometers are allowable.”

Measurements

“Traditional luminaire photometry methods do not work for SSL products…using a procedure called relative photometry. In this method, a luminaire under test and the bare lamp(s) used in the luminaire are measured separately…Such test methods cannot be used for SSL products because, in most SSL products, LED lamp sources are not designed to be separated from the luminaire.”

Source: Illuminating Engineering Society Publication: LM-79-08 (just released)


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Fairytale

LEDs are inherently safe because they are low voltage devices

Three dozen dice, three dozen dice See how they run, see how they run

They sometimes run with a switch mode supply Or else on a linear style they rely

Vf’s placed in series can get rather highFor three dozen dice.

LED DRIVERS


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INSIDE THE BLACK BOX

???

Power SuppliesLED DRIVERS


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• Types of drivers

• Cost impact

• Supply efficiency

• Power quality issues

• Ratings and standards

• Reliability

• Safety

• Control system features and issues

• What about AC LEDs?

IssuesLED DRIVERS


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• Why do we need drivers (power supplies) in the first place?– LEDs are non-linear devices (Vf vs. If) and typically require constant

current sources– Incandescent light bulbs are purely resistive loads with PF = 1– Drivers usually incorporate circuitry to produce PF’s close to 1– Drivers also need to control harmonic current effects on the mains

• ATHD regulated in many countries

• Life– LED life versus driver life– Elements which limit driver lifetime

• Electrolytic capacitors—aging due to drying out of electrolytic• FETs, rectifiers, etc. which are stressed by heat and vibration• Other components affected by heat, moisture, environment

• Size– Drivers equivalent to fluorescent ballasts

LED DRIVERSDescription


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TypesLED DRIVERS

• Custom or off-the-shelf?– How many LEDs? Functional requirements?

• AC/DC or DC/DC? – What is the input source?

• Simple driver: resistor in series– OK for low power applications

• Linear regulator– e.g. LM317 regulator IC

• Switch mode power supply (SMPS)– Buck, Boost, Buck-Boost, Flyback, SEPIC, etc.

• Constant current with feedback– Closed loop system gives best performance


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LED DRIVERSCost Impact

• What % of total cost is the driver?

• Consider operating cost due to efficiency loss?

• Comparison to fluorescent and HID ballasts?

• Design complexity increases cost.

• Important to match source based on power needs

80W LED driver

100W HPS

100W metal halide

32W x4 Fluor. T8

$0.00

$10.00

$20.00

$30.00

$40.00

$50.00

$60.00

$70.00

$80.00

$90.00

Ballast costs*

* Data is based on average prices found on various websites.


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LED DRIVERS

• Typical efficiencies range from 75% to 90% for SMPS

• Losses due to switching, resistances, transformers, etc.

• Poor power factor results in excess energy use

• Driver should not draw power if load is not on (Energy Star

requirement)

Efficiency

PF =Volts x Amperes

≤ 1Watts


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LED DRIVERS

LEDs are non-linear loads which gives rise to distortion on the supply lineTotal Harmonic Distortion (THD) is defined as:

Σ harmonic powers divided by fundamental freq. power

Electromagnetic compliance (EMC) is a concern

Power Quality

Pure AC Waveform

Distorted AC Waveform


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LED DRIVERS

• Maximum power rating should be for worst case Vf conditions.

• Is the output constant over the input voltage range?

• Efficiency as a function of load power– 90% at full power– <70% efficiency at partial power

• Tolerances, ripple current, etc.

Ratings

Important


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LED DRIVERS

• Heat affects lifetime – electrolytic caps, proper heat sinking of transistors, active cooling (i.e. fans)

– FETs Typical maximum junction temperatures of 125oC – Capacitors Values can change by 10-20% or more as

temperatures increase and drift as the component ages • Mechanical vibration, shock

– Large ceramic capacitors are sensitive to mechanical stresses which can cause failures

• Overvoltage and overcurrent protection• Environment - water tight enclosures• Manufacturing quality – you get what you pay for• Warranty Period?

Reliability


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SafetyLED DRIVERS

• Proper grounding is important

• Electrical isolation between input and output

• Short circuit and open circuit protection on output– Someday, somewhere, someone will hook up the

device wrong!

• Flammability concerns

• Multiple LEDs in series can add up to “high voltage”—e.g. 20 LEDs in series x 3.4V each equals 68V which would no longer be considered a “Low Voltage” device by UL

– Some manufacturers now use multiple dies in the same package which can be connected in series (e.g. Cree’s new MC-E which would have a Vf of 14V)

• Lawsuits and recalls can tarnish the industry– Customers don’t care what failed; they just know their

“long-lasting” LED light doesn’t work any more


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• Simple vs. complex. Complexity impacts reliability

• RGB control to balance color, DMX interface

• Dimming – can be linear and/or PWM

• Optical and/or thermal feedback

• “Intelligent controls” - compensate for aging, color shift

• Balancing multiple strings

• Light out detect – shorted or open LEDs

• Existing infrastructure - luminaire must look like a light bulb

• Fail-safe requirements (e.g. beacons or rail signals)

Control SystemsLED DRIVERS


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• Light output varies as a function of input voltage– LEDs are typically configured in a full-bridge or half-

bridge configuration

• LEDs only emit light when the voltage is positive and above a certain threshold

– 60 Hz flicker effect if sources are spaced too far apart– Efficacy can be reduced by as much as 50%

LED DRIVERSThe AC LED

Full-bridge rectified

Half-bridge rectified

Seoul SemiconductorAcriche

LynkLabsSnapBrite


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• LED Luminaires evaluated using UL1598 Luminaire Standard and 8750 (Outline of Investigation) LED Light Sources for Use in Lighting

• Power supplies are listed under either UL2108 Low Voltage Lighting Systems; UL1012Power Units Other Than Class 2 or UL1310 Class 2 Power Units

• EN60598--Generic Luminaire standard - split further into 30 sub-sections – e.g. roadway light, stage light, etc.

• EN55015--EMC emission limits are higher for lighting products, additional requirement to test for low frequency magnetic fields; other standards for EMC susceptibility - flicker, brownouts, ESD, etc.

• EN 61000-3-2--Harmonics and power factor

• EN60825 (Class 2)—Laser Standard under which LEDs presently fall; the deep blue LEDs have cause for concern when used with narrow beam optics

• EN61347—control equipment; split into sections for types of control gear - new section in draft for LED control equipment

Standards US / EuropeLED DRIVERS


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Thermal

Fairytale

LEDs don’t generate heat

Humpty LED sat on a wallRaising its temperature unknown to all

Armies of optic and electrical menCouldn’t get Humpty to light up again


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Thermal

Radiated Heat Conducted Heat

Ceiling Tile

Incandescent Fixture LED Fixture

What’s the difference?


41

Thermal

A fixture using LEDs as the light source would require 12 LEDs to achieve the same 900 lumens. The input power to the fixture would be (assuming a Vf of 3.2V and current of 350mA)

Power = 12 x 3.2V x 350mA = 13.4W The fixture would need to conduct approximately 12 watts of heat.

A fixture using a 60W incandescent light bulb produces 900 lumens of light andmust dissipate 3 watts of heat via conduction.

Heat Loss (%)Radiation Convection Conduction

Incandescent 15 90 5 5Fluorescent 90 40 40 20HID 100 90 5 5LED 75 5 5 90

Efficacy (lm/W)Source


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• Philips: Proper thermal design is imperative to keep the LED emitter package below its rated operating temperature

• Cree: The majority of LED failure mechanisms are temperature-dependent. Elevated junction temperatures cause light output reduction and accelerated chip degradation

• Osram: In order to achieve reliability and optimalperformance a proper thermal management designis absolutely necessary

• Nichia: For high power LED applications, the designer must consider how to manage heat, in order to enhance the performance of the LEDs. If heat management is not considered, the lifetime of the LED will be significantly decreased, or the LED will fail.

• Seoul Semiconductor: Heat causes bad reliability and changes of electrical and optical character negatively. So power LEDs must dissipate heat from chip in that package.

How Important Is Thermal Management for LEDs? Ask the manufacturers:

Thermal

Source: Osram data sheet


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Thermal Management Components

Heat Sinks

Metal Core PCBs

Heat Pipes

ThermoelectricCoolers (Peltier)

Thermal

Piezo fans


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Sintered metal or V-groves

HOT ENDHeat in

COLD ENDHeat out

ThermalHow a heat pipe works

Hot water vapor

Cold water


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LED Efficiency As a Function of Input Power

Thermal

Data courtesy Ian Ferguson, Georgia Tech


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Fairytale

LEDs will last 100,000 hoursor more in normal use

Twinkle, Twinkle LEDHow I wonder what thee be

Up above the world so brightBut twenty years of constant light???

LED Lifetimes


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LED LifetimesHow long will an LED source last?


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A little lifetime experiment:

LED Lifetimes


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• The sun >4.5 billion years (so far)• Candle <12 hours• Oil Lamp <24 hours• Incandescent 1k-2k hours• Fluorescent 5k-24k hours• Mercury Vapor 10k-20k hours• Sodium Vapor 24k hours• Metal Halide 20k-30k hours• 5mm LEDs <10k hours• High Power LEDs >50k hours

How long do light sources last?LED Lifetimes


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It must be true….

LED ReplacementFor a 60W incandescent?

LED Lifetimes


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Well….maybe notLED Lifetimes


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LED Lifetimes

A second example

With maybe a betterchance of meetingits publishedspecifications


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For traditional light sources, lifetime was the time it took for 50% of the population to fail

Not all light sources fail catastrophically—Define End Of Life by reduction in light output from initial values. For example 70% or 50% of initial value

Under what conditions are lifetimes measured?What statistics are used to calculate lifetime?For what period of time are measurements taken?How is steady state defined?Does everyone measure the same way?

High Flux LED

5mm LED

Incandescent

How do you define “Lifetime” for LEDs?LED Lifetimes


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Even incandescent light sources will last a long time if you take care of them. This one has been running for over 106 years!

Fire Station #6Livermore-Pleasanton Fire Department

LED Lifetimes

What’s that spell?


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60,000

50,500

27,000

11,000

Lifetime as a function of input current(at a given Tj)

InGaN Luxeon K2

Source: Philips White Paper “Understanding Power LED Lifetime Analysis”

At a junction temperature of 145oCthis LED would last:12k hours @ 1.5amps;27k hours @ 1.0amps;52k hours @ 0.7amps;and >60k hours @ 0.35amps

LED Lifetimes


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60

70

80

90

100

1,000 10,000 100,000 1,000,000

Time (hours)

% L

umin

ous

Flux

.

65758595105115 55

Junction Temperature

Cree White XR-E Lam p Long Term Lum en Maintenance Projections @ If = 700mA

Manufacturer #1 Manufacturer #2

LED LifetimesConsistency in Measuring Lifetimes?

Standards are coming:IESNA LM-79-08 Approved Method: Electrical and Photometric Measurements

of Solid-State Lighting Products (released)IESNA LM-80 Approved Method for Measuring Lumen Depreciation of

LED Light Sources (still in committee)ANSI C78.377-2008 Specifications for the Chromaticity of Solid-State Lighting

Products for Electric Lamps (released)


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Color shift Temperature (Tj) Lifetime

Flux Current (Ij) Efficiency

Flux Temperature (Tj) Lifetime

Cost Current (Ij) Number of LEDs

A series of tradeoffs:LED Lifetimes


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Fairytale

LEDs provide consistent color

Mary had an LEDIts light was white as snow

And everywhere that Mary wentPeople said: “What’s that blue glow?”

Color


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Consistency???Color


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Color

Boeing 787 Dreamliner Interior

Consistency and uniformity will be critical in new applications in terms of color as well as flux


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Downconverting Phosphor•Blue LED + YAG Cool White•Blue LED + YAG + Other phosphor (red, green, etc.) Warm White•UV LED + Red phosphor + Green phosphor + Blue phosphor

RGB Combine monochromatic red, green and blue LEDs (and possibly amber)

Luxeon K2

Creating White LED LightColor


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Heat Sink Slug

Submount

InGaN Die

Phosphor

Phosphor Deposition: Blue + Yellow = White

Convention Coating Conformal Coating

Conformal coating allows for smaller optic size

Color


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Cree Nichia

Osram

Seoul SemiconductorLumileds Lumileds

Samples of phosphor White LEDsColor


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Spectra of various light sources:

Color

HID

FL

LED

Incandescent

The Sun


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0

0.0001

0.0002

0.0003

0.0004

0.0005

0.0006

400 450 500 550 600 650 700 750Wavelength (nm)

Lum

inou

s Fl

ux (a

.u.)

480 hours960 hours1176 hours1464 hours1632 hours1824 hours

Color Temperature Shift as a function of time

As phosphor output decreases with time,overall CCT shifts tohigher temperatures(more blue)

Color

Curran & Peck, Lightfair 2006


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Spectral Change versus Time

0.0E+00

2.0E-04

4.0E-04

6.0E-04

8.0E-04

1.0E-03

1.2E-03

1.4E-03

1.6E-03

1.8E-03

2.0E-03

400 450 500 550 600 650 700Wavelength (nm)

Rel

ativ

e Fl

ux (A

.U.)

0480960117614641632182434084272573662328032

40% Drop

11% Drop

Hours

ColorSecond example of CCT shift

Curran & Peck, Lightfair 2006


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ANSI C78.377-2008 LED Standard

Figure courtesy Mark McClear, Cree

Color

0.31

0.32

0.33

0.34

0.35

0.36

0.37

0.38

0.39

0.40

0.41

0.42

0.43

0.44

0.45

0.30 0.31 0.32 0.33 0.34 0.35 0.36 0.37 0.38 0.39 0.40 0.41 0.42 0.43 0.44 0.45 0.46 0.47 0.48 0.49 0.50

CCx

CC

y

BBL+

2700 K

+

3000 K

+

3500 K

+

4000 K

+

4500 K

+

5000 K

+

5700 K

+

6500 K

7 Step MacAdam Ellipses for DOE Energy Star CFLsANSI C78.377-2008 LED Standard


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0.31

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0.35

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0.37

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0.45

0.30 0.31 0.32 0.33 0.34 0.35 0.36 0.37 0.38 0.39 0.40 0.41 0.42 0.43 0.44 0.45 0.46 0.47 0.48 0.49 0.50

CCx

CC

y

BBL

+

2700 K

+

3000 K

+

3500 K

+

4000 K

+

4500 K

+

5000 K

+

5700 K

+

6500 K

BBL+

++

+

++

+

+


Mfg #1 Standard Chromaticity Binning


Color


69

0.31

0.32

0.33

0.34

0.35

0.36

0.37

0.38

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0.40

0.41

0.42

0.43

0.44

0.45

0.30 0.31 0.32 0.33 0.34 0.35 0.36 0.37 0.38 0.39 0.40 0.41 0.42 0.43 0.44 0.45 0.46 0.47 0.48 0.49 0.50

CCx

CC

y

BBL

+

2700 K

+

3000 K

+

3500 K

+

4000 K

+

4500 K

+

5000 K

+

5700 K

+

6500 K

BBL+

++

+

++

+

+




Color


70

0.31

0.32

0.33

0.34

0.35

0.36

0.37

0.38

0.39

0.40

0.41

0.42

0.43

0.44

0.45

0.30 0.31 0.32 0.33 0.34 0.35 0.36 0.37 0.38 0.39 0.40 0.41 0.42 0.43 0.44 0.45 0.46 0.47 0.48 0.49 0.50

CCx

CC

y

BBL

+

2700 K

+

3000 K

+

3500 K

+

4000 K

+

4500 K

+

5000 K

+

5700 K

+

6500 K

BBL+

+

+

++

+

+




Color


71

0.31

0.32

0.33

0.34

0.35

0.36

0.37

0.38

0.39

0.40

0.41

0.42

0.43

0.44

0.45

0.30 0.31 0.32 0.33 0.34 0.35 0.36 0.37 0.38 0.39 0.40 0.41 0.42 0.43 0.44 0.45 0.46 0.47 0.48 0.49 0.50

CCx

CC

y

BBL

+

2700 K

+

3000 K

+

3500 K

+

4000 K

+

4500 K

+

5000 K

+

5700 K

+

6500 K

BBL+

+

+

++

+

+




Color


72

0.31

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0.33

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0.35

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0.42

0.43

0.44

0.45

0.30 0.31 0.32 0.33 0.34 0.35 0.36 0.37 0.38 0.39 0.40 0.41 0.42 0.43 0.44 0.45 0.46 0.47 0.48 0.49 0.50

CCx

CC

y

BBL

+

2700 K

+

3000 K

+

3500 K

+

4000 K

+

4500 K

+

5000 K

+

5700 K

+

6500 K

BBL+

+

+

++

+

+


Cree Standard Chromaticity Binning


Color


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What color bins can you live with in your design?– Can you combine bins to get the color temperature you desire?– Do you have special requirements for flux and Vf as well?

• Will the LED manufacturer you choose consistently be able to supply that bin?– Can you get those bins from other manufacturers?– What is the standard delivery time?

• What other industries use those same bins?– Will you be the big or little fish?

• Does your local distributor stock those bins as well?– What is the return policy? Remember, improvements come

quickly in the LED world and you don’t want to be stuck with obsolete inventory.

ColorThings to Consider about Binning:


74

CRI is a calculated value based on the difference in chromaticity of a series of 8 (or 14) different colors (CIE Color Space) when illuminated with a

reference light source versus a test subject light source.It is a measure of a light source’s ability to show colors realistically as compared to familiar sources (e.g. an incandescent bulb or the sun)

Color Rendering Index (CRI)Color


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Spectra of the 8 (14) Color Standards Used for CRIColor


76

ΔEi = √ ΔUi2 + ΔVi

2 + ΔWi2

where U, V and W are the 1964 Uniform Color Coordinates

Ri = 100 – 4.6 ΔEi

where Ri is the Color Rendering Index for the specific color sample i

CRI = (1/8) x ∑ Rii = 1

i = 8

Definition of Color Rendering Index (CRI)Color


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CRI 62 CRI 90

Same ColorTemperatureLight Source

CRI 98 / CCT 4100 CRI 93 / CCT 5500

Different ColorTemperatureLight Sources

CRI is not the whole storyColor


78

The problem with CRI and LEDs

In calculating CRI, none of the reflective targets are highly saturated, creating a poor match with the highly saturated color output of LEDs. Color rendering can be poor for saturated colors even when the CRI is good

NIST is in the process of creating a new Color Rendering Standard which takes into account that shifts in hue and saturation should not be weighted equally. The new proposed standard is Color Quality Scale (CQS).

Color

An RGB LED source with the spectra at left yields a CRI of 80, yet produces the test colors shown below


79

Color possibilitiesat nominal valuesfor each LED:red (627)green (530)blue (470)

Potential Color Palette(all LEDs at nominal specifications)

Color


80

Color possibilitiesat potential limitsof each LED:red (620)green (550)blue (490)

Potential Color Palate(all LEDs at extreme specifications)

Color


81

Color possibilitiesat nominal valuesfor each LED:red (627)cyan (505)blue (470)

Another example using cyan(nominal specifications)

Color


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Color possibilitiesat extreme limitsfor each LED:red (620)cyan (490)blue (490)

Another example using cyan(extreme specifications)

Color


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How important is color to your lighting project?

• Television studio—definitely

• Retail environment—probably

• Street lighting—maybe less so

ColorYou decide


84

Fairytale

LEDs are so great that the world will have to adapt

LED, LED, optics man,Make me a light as fast as you canSolder it, cool it and give it a stir

And make sure it works with the infrastructure

Lighting Systems


85

Matching Existing Infrastructure:Needs to Look Like a Light bulb?

+ =

Lighting Systems


86

GE Sylvania Philips

What’s the difference in these 100W light bulbs?

Lighting Systems


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Lumination Osram Lumileds Vio Platinum Dragon K2

What is the commonality in these LED sources?

Lighting Systems


88

Lumileds K2 Lumileds Rebel Cree XR-E

OsramDiamond Dragon Seoul P4 Nichia

NS6W083

Component InterchangeabilityLighting Systems


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What’s the difference in these 1W LEDs?

Lumileds Osram Cree Luxeon K2 Golden Dragon XRE1mm x 1mm 0.8mm x 0.8mm mm x 1mm

Lighting Systems


90

Height of die affectsthe beam pattern

Size of die affectsthe beam pattern

Lighting SystemsOptical performance with different die sizes and heights

Figure courtesy John Peck, Dialight


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Fairytale

Saving Energy = Saving Money

Hey diddle diddle, The engineers fiddle,

Making LEDs light up the moon.The accountants laugh to see such sport,

Knowing payback is none too soon

LED Economics


92

> 50k65-7599Best-in-Class Power LED

30k6290T5 fluorescent

24k55-6595-110High-pressure sodium

20-30k65-7085-90T8 fluorescent

16k65-75120-140Low-pressure sodium

10k-20k35-4065-70Metal halide

20k40-5060T12 fluorescent

10k12-2020Halogen

3k10-1717Incandescent

Lifetime (hrs)

Usable* lm/W

Data Sheet lm/WLight Type

• Typical expected performance in real-life applications. Based on mean lumens, and including ballast/driver, thermal equilibrium. and typical fixture Coefficient of Utilization losses.


Efficacy of Various Light Sources

LED Economics


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Initial Fixture Cost

Energy Costs

Replacement costs (source + labor)

Operating Time

Tota

l Cos

t

LED Source

Traditional Source

{LEDSavings

Assumption: LED lifetime is 4X’s longer than traditional source

LED Economics


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Comparison of HID vs. LED Operating Cost(Oakland, CA Project)

$0

$500

$1,000

$1,500

$2,000

$2,500

$3,000

0 5 10 15 20 25 30

Time (in years)

Ope

ratin

g C

ost

HPS (Group Relamping)

HPS (Spot Relamping)

LED

LED (Cost 40% less)

GroupSpotLower Cost LED

Real Life Example

LED Economics

Breakeven Point


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Sorted by cost/lumen

LED Economics

Light Source Output CostNote1 Cost/Lumen

Incandescent (60W) 830 lum $ 0.42 $0.0005Fluorescent (32W T8) 2,800 lum $ 2.23 $0.0008HPS (100W) 9,500 lum $12.00 $0.0013Metal Halide (100W) 9,500 lum $29.95 $0.0032CFL (30W) 2,000 lum $ 9.99 $0.0050Halogen (60W PAR38) 880 lum $ 6.49 $0.0033LED (@ 1.25W) 100 lum $ 2.20 $0.0220

Note 1 All sources except incandescent and halogen require a ballast or driver; ballast usually included in cost of CFL


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Sorted by efficiency

LED Economics

Light Source Output Efficacy Cost/Lumen

HPS (100W) 9,500 lum 95 lm/W $0.0013Metal Halide (100W) 9,500 lum 95 lm/W $0.0032Fluorescent (32W T8) 2,800 lum 88 lm/W $0.0008 LED (1.25 W) 100 lum 80 lm/W $0.0220CFL (30W) 2,000 lum 67 lm/W $0.0050Halogen (60W PAR38) 880 lum 15 lm/W $0.0033Incandescent (60W) 830 lum 14 m/W $0.0005


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One must look at the total system cost

Ballast 18%

Source 36%

Fixture 45%

80W LED luminaire $440

Ballast 53%

Source 6%

Fixture 40%

128W Fluorescent luminaire $374

Ballast 31%

Source 28%

Fixture 41%

100W HPS luminaire $488Source 3%

Fixture 97%

800W Incandescent luminaire $514

LED Economics


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Effic

acy

(lum

ens/

wat

t)C

ost ($/lumen)

Time

100 lumens/w

2008

2.5 cents/lumen

LED EconomicsDevice Performance Over Time

Haitz’s Law:Output increases by a factor of 20 while costdecreases by a factor of 10 every 10 years

Note: Y axes are logarithmic scales


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Some figures from a recent DOE Energy Star meeting:

LED Economics

Source: Marc Ledbetter, Energy Star SSL Stakeholder Workshop, May 15, 2008

Even at $0.002/lumen an LED light bulb with the same lumen output as a 60W incandescent would cost $1.70

Year

Cool White Efficacy

(Commercial) in lum/W

Warm White Efficacy

(Commercial) in lum/W

Fixture Efficiency

Driver Efficiency

Overall Luminaire

Efficacy (Cool White) in

lum/W

Overall Luminaire Efficacy

(Warm White) in lum/W

Cost / k-lumen

2007 84 59 77% 85% 47 33 $25

2010 147 122 84% 89% 97 80 $10

2012 164 139 88% 91% 121 101 $5

2015 188 163 95% 95% 161 140 $2


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• Are LEDs like other light sources?

• Can LEDs last 100,000 hours?

• Can LEDs be used today in all applications?

• Will LEDs save energy?

• Will LEDs save money?

• Consider LEDs for future projects/designs?

SummarySome questions:

No— Allows many unique solutions (e.g. color changing, tight-fits)

Maybe— Depends on many factors of design/environment

No— The warmer the environment, the more difficult the design

Almost always— Presently one of the most efficient light sources and getting better

Depends— Costs continue to decrease at “Haitz’s Law” rate

Absolutely— If you want to stay in business


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• Ian Ferguson Georgia Tech• John Peck Dialight Corporation• Mark McClear Cree

Acknowledgements


102

Thank You

Please remember to complete the course evaluations.

We hope you enjoy the trade show and conference!

[email protected]

100,000 Hour LifetimesAnd Other LED Fairytales

Presentation available at:www.ledtransformations.com

Please contact authors concerning any referencing errors and they will be corrected

mailto:[email protected]

http://www.ledtransformations.com/

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