Presentation on LM 79 & 80

8/17/2019 Presentation on LM 79 & 80

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Capturing the Lighting Edge – August 13, 2012 New York, NY

© 2012 Rensselaer Polytechnic Institute. All rights reserved.

LED Testing Standards Overview

Presented by: Andrew Bierman, MS and Jean Paul Freyssinier, MSwith contributions from Yiting Zhu, PhD and N. Narendran, PhD

Lighting Research Center, Rensselaer Polytechnic Institute, Troy, NY, USA

Meeting and Measuring

ENERGY STAR® Requirements


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Outline

Background

› Relative vs. absolute photometry LED photometric testing standards:

› IES LM-79-08

› IES LM-80-08› IES TM-21-11

› IES LM-82-12

General questions and answers


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Relative and Absolute Photometry

Relative Photometry:› Output is relative to an easily-measured

condition› E.g., bare lamp operated on a referenceballast, base up at 25°C

› Specific lamp performance doesn’t matter

Absolute photometry:› Output is measured in calibrated units

under specific operating and environmentalconditions

• Orientation

• Input voltage• Ambient temperature

› Lamp and system performance matters

3

CFL


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Absolute is more difficult because:

Need to maintain flux standards and calibrate equipment› Calibrate with incandescent, measure other SPDs and directional light

sources

Sampling concerns› How many? How to choose? Are samples representative?

Must reproduce environmental and operating conditionswhile maintaining calibrated equipment› Temperature, input voltage or current (driver)

4

Comfortable and accurate at 25° C, buthow to take measurements at 85° C?


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Relative photometry is used to simplify testing

› Works well when the system is well defined and characterized

• E.g., linear fluorescent lamp systems

– Flux = (rated lumens) x (ballast factor) x (luminaire efficiency)

› Does not work well for making comparisons across differentsystems

• E.g., CFL replacements for incandescent lamps

– Geometry issues, lack of reference ballast definitions, temperatureeffects

› Useful for measuring variations under different testing

conditions• Light output over time

• Elevated temperature

5


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Standard Test Methods for LED Products

Standard Method Purpose

IES LM-79-08 Absolute Light output, efficacy,color for LED products

IES LM-80-08 Relative Light output over time,temperature for LEDpackages

IES LM-82-12 Relative

(references LM-79)

Light output, efficacy,

color over temperature forlight engines

IES TM-21-11 Calculation, modeling Extrapolating LM-80 testdata to predict life

ANSI/UL 153:2002 (Secs.124-128A) ANSI/UL 1574:2004 (Sec.54) ANSI/UL 1598:2008 (Secs.

19.7, 19.10-16)

Portable ElectricLuminairesTrack Lighting Systems

Luminaires

Methods for in-situtemperature method(ISTM) testing forEnergyStar


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IES LM-79-08 Approved method: Electrical and PhotometricMeasurements of Solid-state Lighting Products


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© 2012 Rensselaer Polytechnic Institute. All rights reserved.8

Scope LM-79-08

Solid-state lighting products for illumination purposes Complete systems with electrical drivers and heat sinks

› Powered by AC mains or dc voltage Measurements under standard conditions

› Total luminous flux› Electrical power, input voltage and current› Luminous intensity distribution

› Chromaticity, correlated color temperature (CCT), Color Rendering Index(CRI)

Luminaires (including light source) and integrated LED lamps› e.g., recessed down lights (must include light source)› e.g., A-lamp replacements

Methods for individual product performance. Does not cover howindividual variations affect performance.


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Ambient Conditions

Air Temperature

› 25°C ±1°C

› Measured at the same height as the fixture› Shielded from direct radiation

Thermal Conditions for Mounting SSL Products

› Heat conduction through supporting objects must be negligible

› If sample is provided with a support structure used for thermalmanagement, then the sample shall be tested with the support structureattached

Air Movement

› Keep airflow around SSL sample to a minimum

› Should only be natural convection air current from sample operation


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Power Supply Characteristics

Waveshape of AC power supply

› Shall have a sinusoidal shape with ≤ 3% distortion of the

fundamental frequency

Voltage regulation

±0.2% of the rated value

For a product rated at 120V

119.76V < Vin < 120.24V


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Seasoning of SSL Products

No seasoning of samples priorto testing

› The test committee determinedthis method would produce themost repeatable results

Other light sources

› Incandescent lamps: 0.5% ofrated life

› Fluorescent lamps: 100 hrswith 3-hr on and 20-min off

cycle

› HID: 100 hrs with 11-hr on and1-hr off operating cycle

Initial lumenmaintenance of LEDs


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Stabilization of SSL Products

Stability based on both input power

and light output Stability is when the variation of at

least 3 readings over a period of 30

min, taken 15 min apart, is less than0.5 %


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Test of an SSL Downlight Product

10.00

10.05

10.10

10.15

10.20

10.25

10.30

10.35

10.40

10.45

10.50

0 10 20 30 40 50 60 70 80

Time (min)

I n p u t P

o w e r ( W )

12

12.1

12.2

12.3

12.4

12.5

12.6

R e l a t i v e L

i g h t O u t p u t

Input Power

Light Output


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Test of an SSL Downlight Product

10.00

10.05

10.10

10.15

10.20

10.25

10.30

10.35

10.40

10.45

10.50

0 200 400 600 800 1000

Time (min)

I n p u t P o w e r ( W )

12

12.1

12.2

12.3

12.4

12.5

12.6

R e l a t i v e

L i g h t O u t p u t

Input Power

Light Output

1.4%

0.9%

Efficacy by 2.3%Over next 12 hours


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Operating Orientation

Shall be evaluated in the orientation recommended by themanufacturer for an intended use of the sample

Stabilization and photometric measurements of SSLproducts shall be done in such operating orientation

Note:The light emission process of anLED is not affected by orientation

Orientation can change the thermal

conditions for the LEDs used in theproduct, and so…

The light output may be affected byorientation of the SSL product


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Electrical Settings

Operated at rated voltage according to its normaluse

› No pulsed operation

If the product has dimming capability,measurements shall be performed at the maximum

input power condition If the product has multiple modes of operation

including variable CCT, measurement may be made

at different modes of operation (and CCTs) ifnecessary, and such setting conditions shall beclearly reported

16


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Electrical Instrumentation

Instrumentation Calibration

Uncertainties (u)Expanded uncertainty: 2-sigma, 95%

confidence

ac voltage and current u ≤ 0.2%

ac power u ≤ 0.5%

dc voltage and current u ≤ 0.1%


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Test Methods for Total Luminous Flux Measurement

Two options

1. Integrating Spherea) with spectroradiometer

b) with photometer head (requires spectral mismatch error

correction – not trivial)

2. Goniophotometer

a) Most use photometer head

b) Spectroradiometer needed for color measurements


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Sphere geometry

4 Geometry› total SA of product should be


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Goniophotometer

Primarily used for the measurement of the

luminous intensity distribution of lamps andluminaires

www.npl.co.uk

www.intertek-etlsemko.com


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Goniophotometer measurements

LM-79 specifies type C goniometers› Burning position of the sample is

unchanged relative to gravity› Minimal impact of thermalperformance of sample

Two sub-types› Moving detector

› Moving mirror The speed of rotation should be such

as to minimize the disturbance of thethermal equilibrium of the sample

Relative photometry method,

commonly used in traditionalluminaire testing, cannot be used forSSL products with integral lamps


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Colorimetric calculations

The chromaticity coordinates (x, y ) and/or (u’, v’ ), andcorrelated color temperature (CCT, unit: kelvin) are

calculated from the relative spectral distribution› Commission Internationale de l'Eclairage, Colorimetry , 3rd edition,

CIE 15:2004

The Color Rendering Index (CRI) is calculated according tothe formulae defined in

› Commission Internationale de l'Eclairage, Method of Measuring andSpecifying Colour Rendering of Light Sources, CIE 13.3-1995


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Spatial non-uniformity of chromaticity

Products may have variation of color with angle of emission

Spatial non-uniformity of chromaticity shall be evaluated

› The spatial non-uniformity of chromaticity, u’v’ , is determined as

the maximum deviation among all measured points from the

spatially averaged chromaticity coordinate

› distance on the CIE (u’, v’ ) diagram For this evaluation, accuracy only in chromaticity differences

is critical, and thus, measurements may be made with a

tristimulus colorimeter if a spectroradiometer is not available

If u’v’ < 0.001 a single, directional measurement with a

spectroradiometer suffices for color. Else …


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12.2 Method using spectroradiometer or colorimeter spatially

scanned

Manually positioning theinstrument for given directions

at a constant distance Shall be measured at

› ≤10° intervals for verticalangle over the angle rangewhere light is intentionallyemitted from the source

› Minimum two horizontal angles=0° and 90°

The chromaticity measurements

need to be made only for theangles where the averageluminous intensity is >10% ofthe peak intensity

IES-LM-79-08


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Method using spatially scanned spectroradiometeror colorimeter

May be used when

› Sphere-spectroradiometer system is not available

› Test sample is too large for a sphere-spectroradiometer system

Can be achieved most efficiently by mounting the color-measuring instrument on a goniometer

› Called gonio-spectroradiometer , or gonio-colorimeter Luminous intensity distribution and chromaticity coordinates

can be measured at the same time

› taking readings at appropriate angle intervals over the entire angle

range where the light is intentionally emitted from the product

› Then, the spatially averaged chromaticity is obtained from allmeasured points by spatially-integrated tristimulus values


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IES LM-80-08 Approved Method for Lumen MaintenanceTesting of LED Light Sources


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Scope IES LM-80-08

Measuring lumen maintenance for LED› Packages

› Arrays› Modules

Does not provide guidance or make anyrecommendations regarding predictive estimations orextrapolation beyond that from actual measurements(TM-21 covers this)

CREE LED Supply CREE


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Definitions

LED light source

› An LED package, array, or module that is operated via an auxiliary driver

Lumen maintenance

› Luminous flux output at any selected elapsed operating time

› Usually expressed as a percentage of the maximum output)

Lumen maintenance life

› Elapsed operating time at which the specified lumen maintenance is reached

Rated lumen maintenance

› L70: time to 70% lumen maintenance

› L50: time to 50% lumen maintenance

Case temperature› Temperature of the thermocouple attachment point on the LED source

defined by manufacturer


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LED Life Definitions

› 70% for general lighting, illumination (L70)

• L70 (hrs) = 30% reduction in light output

› 50% for decorative lighting, indicators (L50)• L50 (hrs) = 50% reduction in light output

29

Time

L i g h t O u t p u t

100%

0%

70%

50%

L70 L50


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General Conditions

Conduct test in clean environment

Individual labeling of LED sources

Representative sampling of LEDs and report samplingmethod

Minimize vibration (although not nearly as sensitive as otherlamp types)

Minimize airflow, but do not allow thermal stratification

Operating orientation and spacing

› Orient as specified by manufacturer

› Space to allow air flow around units


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Temperature and humidity

A minimum of 3 case temperatures

› 55°C

› 85°C

› The third is at the discretion of the manufacturer

Temperature tolerance +0, -2° C

Air temperature surrounding case within +0, -5°C

Relative humidity < 65%


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Electrical and instrumentation

Current maintained ± 3% during life test

› ± 0.5% during photometric testing

Thermocouple accuracy limits: ≤ 1.1°C or 0.4%

Elapsed time uncertainty within ± 0.5%

Photometric measurements performed at 25 ± 2°C

Test duration

› At least 6000 hours, preferably 10,000 hours

› Photometry every 1000 hours minimum

Operating cycle

› Constant current (no modulation, e.g. PWM)


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IES TM-21-11Projecting Long Term Lumen Maintenance ofLED Light Sources

34


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IES TM-21-11

Scope:

› Provides a recommendation for projecting longterm lumen maintenance of LED light sourcesusing LM-80-08 lumen maintenance data

34


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IES TM-21-11

Projection method:› Data: LM-80-08 report

• 6000-hour data with 1000-hour interval

• Less than 1000-hour interval is encouraged

• Data beyond 6000 hours is encouraged

› Sample size:• 20 units for a multiplication factor of 6

• 10-19 units for a multiplication factor of 5.5• Not applied for sample size less than 10

units

› Normalization:• Normalize all collected data to 100% at 0

hour for each DUT› Average

• Average the normalized measured data ofall samples

• Miller, C., 2011. IES TM‐21‐11 Overview, History and Q&A Session. EPA ENERGY STAR Lamp Round Table, San Diego, CA, Oct. 24, 2011.

IES‐TM‐21‐11


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IES TM-21-11

6 times rule based on confidence band, which is determinedby:

› Number of samples› Uncertainty of measurement system over time

• Miller, C., 2011. IES TM‐21‐11 Overview, History and Q&A Session. EPA ENERGY STAR Lamp Round Table, San Diego, CA, Oct. 24, 2011.


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IES TM-21-11

Projection method (cont’d):

› Data used for curve-fit

• 6,000 h 10,000 h

– Last 50% of the total test duration shall beused

(Miller, 2011)• Miller, C., 2011. IES TM‐21‐11 Overview, History and Q&A Session. EPA ENERGY STAR Lamp Round Table, San Diego, CA, Oct. 24, 2011.

• Tuttle, R. et al., 2011. TM‐21 Update: Method for Projecting Lumen Maintenance of LEDs. CORM 2011 Technical Conference.


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IES TM-21-11


› Data used for curve-fit

• show that using 1000-6000 hour data vs.

5000-10,000 hour give different lifetimepredictions

• later data show more characteristic decaycurve of interest

– Non-semiconductor related decay(encapsulant, etc.) occurs early on

– Later decay is semiconductordegradation-related and can beconsidered as classic exponential decay

– Long duration data sets (>10,000 h)show better verification

(Miller, 2011)• Miller, C., 2011. IES TM‐21‐11 Overview, History and Q&A Session. EPA ENERGY STAR Lamp Round Table, San Diego, CA, Oct. 24, 2011.• Tuttle, R. et al., 2011. TM‐21 Update: Method for Projecting Lumen Maintenance of LEDs. CORM 2011 Technical Conference.


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IES TM-21-11

Projection method:

› Curve-fit

)exp()( t Bt

• t

= operating

time

in hours

• (t) = averaged normalized luminous flux output

at time t

• B = projected initial constant derived by the least

squares curve‐fit• α = decay rate constant derived by the least

squares curve‐fitIES‐TM‐21‐11


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IES TM-21-11


› Curve-fit

)100ln( p

B

L p

Lp = lumen maintenance life expressed in

hours where p is the percentage of initial

lumen output that is maintained.

)7.0

ln(

70

B

L

For example:

• When α>0, the exponential curve‐fit decays to zero, Lp>0 (valid calculation)

• When α


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IES TM-21-11

Temperature interpolation

› Interpolate Lp (@Ts,i=70C) between Ts,1 (55C) and

Ts,2 (85C)

A = pre‐exponential factor;Ea = activation energy (in eV);

Ts,i = in‐situ absolute temperature (in K);

kB= Boltzmann’s constant (8.6173x10‐5 eV/K)

)exp(,is B

ai

T k

E A

(After Tuttle et al., 2011)Arrhenius equation to calculate in situ decay rate constant.

• Tuttle, R. et al., 2011. TM‐21 Update: Method for Projecting Lumen Maintenance of LEDs. CORM 2011 Technical Conference.

55 C

85

C

70

C??


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IES TM-21-11

Sample size - Sample size - Sample size -

Number of failures - Number of failures - Number of failures -

DUT drive current used

in the test (mA)-


in the test (mA)-


in the test (mA)-

Test duration (hours) - Test duration (hours) - Test duration (hours) -

Test duration used for

projection (hour to hour)-





Tested case

temperature (⁰C)-

Tested case

temperature (⁰C)-

Tested case

temperature (⁰C)-

α - α - α -

B - B - B -

Calculated L70(Dk)(hours)

- Calculated L70(Dk)(hours)

- Calculated L70(Dk)(hours)

-

Reported L70(Dk)

(hours) -

Reported L70(Dk)

(hours) -

Reported L70(Dk)

(hours) -

Table 1: Report at each LM-80 Test Condition

Description of LED Light Source

Tested (manufacturer, model,

catalog number)

Ts,1 (⁰C) -

Ts,1 (K) -

α1 -

B1 -

Ts,2

(⁰C) -

Ts,2 (K) -

α2 -

B2 -

Ea/kb -

A -B0 -

Ts,i (⁰C) -

Ts,i (K) -

αi -

Projected L70(Dk)

(hours)-

Reported L70(Dk)

(hours)-

(projection based on in-situ temperature entered)

55

C

85

C70 C??

55 C

55 C

85

C

85

C

70

C

( A f t e r T u t t l e e

t a l . ,

2 0 1 1 )

www.energystar.gov/TM‐21calculator

www.energystar.gov/

TM‐21calculator


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IES LM-82-12 Approved method: Characterization of LEDLight Engines and LED Lamps for Electrical and

Photometric Properties as a Function ofTemperature

LED Light Engines LED Lamps


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Decorative luminaires

Commonly used in residential andhospitality applications

Can provide a coordinated lookwhile serving different functions› Sconces, chandeliers, pendants, table

and floor lamps

› Available in a variety of shapes, stylesand finishes

Combine “fashion with function,”….according to the AmericanLighting Association

www.americanlightingassoc.com/about_news_detail.php?id=2


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LED industry trend

Manufacturers often design families of decorative luminaires:

› Sconces, pendants, table and floor lamps

› These luminaires can provide a coordinated look while serving

different functions

A large number of decorative luminaires can use a commonlight source (LED light engine).

Photometric testing of complete fixtures is not a feasibleconcept for such luminaires.


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Why LM-82-12?

Luminairephotometry is lessmeaningful forend-users ofdecorativeluminaires

• Alex Baker and Taylor Jantz‐Sell, 2011. ENERGY STAR Luminaires Specification. ENERGY STAR Luminaires Conference Call , March 9, 2011.

• ASSIST, Recommendations for Testing and Evaluating White LED Light Engines and Integrated LED Lamps Used in Decorative Lighting Luminaires, Volume 4, Issue 1, revised April, 2009.

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1x

y

CIE Chromaticity Diagram 1931

Black Body Locus

White Shade

Blue Shade

Amber Shade

Decorative Glass Shade

WAC Lighting luminaires tested by LRC

Glass shade Vin (V) Pin (W) Ф (lm)Efficacy

(lm/W)x y CCT (K) CRI

White 120.1 4.48 165.0 36.8 0.3929 0.3876 3761 73.6Blue 120.1 4.48 129.9 29.0 0.3468 0.3698 4998 72.0

Amber 120.0 4.48 82.6 18.4 0.4507 0.4129 2851 69.0

Highly decorative 120.1 4.48 34.9 7.8 0.4499 0.3942 2711 78.1

IES LM 82 12


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IES LM-82-12

ASSIST recommends formed the basis for LM-82-12.

› LED performance (luminous flux, life) largely depends on theLED junction temperature, which varies depending on how theLED is integrated into the luminaire and the installationenvironment.

LM-82-12 requires testing the performance of the LEDlight engine and the integrated lamp as a function oftemperature, so the performance at in situ temperaturecan be predicted:

› Power (W)› Luminous flux (lm)

› Color

LM 82 12 LM 79 08


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Capturing the Lighting Edge – August 13, 2012 New York, NY© 2012 Rensselaer Polytechnic Institute. All rights reserved.

LM-82-12 vs. LM-79-08

LM-82-12 LM-79-08

Scope • LED light engines• Integrated LED lamps

• LED luminaires• Integrated LED lamps

ENERGY STARLuminaires v1.1

For non-directional luminaires LED light engines GU24 integrated LED lamps

For directional luminaires

Testing ambienttemperature

At different temperatures(*UUT Tb: Tb±2°C)

25°C±1°C

*UUT stands for unit under test; Tb stands for UUT manufacturer‐specified temperature monitoring point temperature

IES LM 82 12


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IES LM-82-12

Thermal environment

› Mounting the UUT to a thermoelectric cooler (TEC)

› Mounting the UUT in a temperature chamber that onlycontrols the local environment around the UUT

Temperature measurement› Tb: UUT

› Td: driver

www.cree.comhttp://m.grainger.com/mobile/details/;jsessionid=A011BDF9B

AE709D7BBC43E004EB6A7FF.prgav06?R=4HGL3

Tb: UUT Td: driver

Th l t t h b LED li ht i


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Thermal test chamber: LED light engines

Temperature

sensor (Td)Driver

LED/LED array

Heat Sink

Heater Insulation

Temperature

sensor (Ts)

Test chamber – painted white on the outside

ASSIST, Recommendations for Testing and Evaluating White LED Light Engines and Integrated LED Lamps Used in

Decorative Lighting Luminaires, Volume 4, Issue 1, revised April, 2009.

Th l t t h b LED li ht i


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Example inside integrating sphere

Thermal test chamber: LED light engines

Proposed method


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Proposed method

First, the LED light engine performance is measured as afunction of temperature.

› LED light engine is placed inside a thermal test chamber.› The heater is turned on until Ts reaches 40% (and 60% and 80% )

of Tj max (specified by the LED manufacturer)

› Photometric and electric quantities and life are measured at these

three temperatures.

Ts (°C)

Flux (lm)

Ts (°C)

CIE x,y

Ts (°C)

Life (L70) (hrs)

Proposed method


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Ts (°C)

Flux (lm)

Ts (°C)

CIE x,y

Ts (°C)

Life (L70) (hrs)

Proposed method

Estimating light engine performance in aluminaire

› Temperature Ts is measured while the light engine isoperating in a luminaire in its operating environment.

› The performance parameter is estimated from theplots generated during the engine’s characterization.

Thermocouple(Ts)

IES LM 82 12


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IES LM-82-12

Troom Troom+25°C Troom+ΔT

Φ

( l m )

Tin‐situ


P ( W )

Tin‐situ


x Tin‐situ


y Tin‐situ


C C T ( K )

Tin‐situ

“Simple curve fit” • Linear• Exponential

• Etc.

IES LM-82-12:Test report


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IES LM-82-12:Test report

Test date, facility, equipment, and operator

UUT description (manufacturer, description, catalog number)

If applicable, UUT driver description (manufacturer, description, catalog number, input and output parameters)

Description of test method including testing configuration.

Internal procedure reference

Initial Temperature First ElevatedTemperature(Initial+25°C)

Second ElevatedTemperature (per TestRequesters)

Measured temperature of Tb (or Td)

Input power (W)

Input voltage (V)

Input current (A)

Luminous flux (lm)

Luminous efficacy (lm/W)

CIE chromaticity (x,y or u’,v’)(optional)

Correlated color temperature (K)(as optional)

Uncertainties


Summary


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Summary

Heat management is critical to LED performance› Short and long term: color shift, lumen depreciation

Performance of bare LEDs is not predictive of thesystem’s performance

Testing luminaires under realistic conditions (as a

function of environment temperature) providesmore useful information to end users and designers

SSL testing standards aim to measure LEDs andLED systems under repeatable conditions, but stillmay not provide all the information needed in thefield.

Acknowledgements


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Acknowledgements

NYSERDA for sponsoring this event

Acuity Brands Lighting forhosting the event

› Jessica Lloyd

LRC faculty, staff, and students

ASSIST program sponsors


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Thank you

Documents

Presentation on LM 79 & 80