IESNA TM-16-2005 Technical Memorandum on Light Emitting Diode (LED) Sources and Systems.pdf

1、IESNA TM-16-05IESNA TechnicalMemorandum onLight Emitting Diode (LED)Sources andSystemsPrepared by:The IESNA Light Sources CommitteeIESThe LIGHTING AUTHORITYIESNA TM-16-05Technical Memorandum onLight Emitting Diode (LED)Sources and SystemsPublication of this Recommended Practice has been approved by

2、the IESNA. Suggestions forrevisions should be directed to the IESNA.Prepared by:The IESNA Light Sources CommitteeIESNA TM-16-05Copyright 2005 by the Illuminating Engineering Society of North America.Approved by the IESNA Board of Directors, April 11, 2005, as a Transaction of the Illuminating Engine

3、eringSociety of North America.All rights reserved. No part of this publication may be reproduced in any form, in any electronic retrieval systemor otherwise, without prior written permission of the IESNA.Published by the Illuminating Engineering Society of North America, 120 Wall Street, New York, N

4、ew York 10005.IESNA Standards and Guides are developed through committee consensus and produced by the IESNA Officein New York. Careful attention is given to style and accuracy. If any errors are noted in this document, please for-ward them to Rita Harrold, Director Educational and Technical Develop

5、ment, at the above address for verificationand correction. The IESNA welcomes and urges feedback and comments.Printed in the United States of AmericaISBN # 0-87995-206-70DISCLAIMERIESNA publications are developed through the consensus standards development process approved by theAmerican National St

6、andards Institute. This process brings together volunteers representing varied view-points and interests to achieve consensus on lighting recommendations. While the IESNA administers theprocess and establishes policies and procedures to promote fairness in the development of consensus, itmakes no gu

7、aranty or warranty as to the accuracy or completeness of any information published herein.The IESNA disclaims liability for any injury to persons or property or other damages of any nature whatso-ever, whether special, indirect, consequential or compensatory, directly or indirectly resulting from th

8、e pub-lication, use of, or reliance on this document.In issuing and making this document available, the IESNA is not undertaking to render professional or otherservices for or on behalf of any person or entity. Nor is the IESNA undertaking to perform any duty owed byany person or entity to someone e

9、lse. Anyone using this document should rely on his or her own indepen-dent judgment or, as appropriate, seek the advice of a competent professional in determining the exerciseof reasonable care in any given circumstances.The IESNA has no power, nor does it undertake, to police or enforce compliance

10、with the contents of thisdocument. Nor does the IESNA list, certify, test or inspect products, designs, or installations for compliancewith this document. Any certification or statement of compliance with the requirements of this document shallnot be attributable to the IESNA and is solely the respo

11、nsibility of the certifier or maker of the statement.IESNA TM-16-05Prepared by the IESNA Light Sources CommitteeIESNA Light Sources CommitteeSarah Carleton, ChairR. BartonF. DourosE. GraffP. HakkarainenR. HornerM. R. MahjoubE. PerkinsL. Reeder*B. RyanJ. WaymouthI. YeoC. You*AdvisoryIESNA TM-16-05CON

12、TENTSForeword . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.0 Brief History of LEDs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

13、 . . . . . . . . . . . . . . . . . . 11.1 Invention and Development . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.2 Product Deployment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

14、. . . . . . . . . . . . . . . . . . . . 12.0 Technology of LEDs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.1 How LEDs Work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15、 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.2 Types of LEDs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.3 Basic Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . .

16、 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22.3.1 Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22.3.2 Size . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

17、 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22.3.3 Energy Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22.3.4 Color . . . . . . . . . . . . . . . . . . . . .

18、 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22.3.5 “White” LEDs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22.3.6 Luminous Flux . . . . . . . . .

19、. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52.3.7 Efficacy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52.3.8 Life . . . . . . .

20、. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52.4 LED System Components and Their Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62.4.1 Electrical Model . . . . .

21、 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62.4.2 Power Source . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72.4.3 Thermal Interface

22、. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72.4.4 Optical Coupling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72.5 Limitations .

23、 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72.5.1 Vibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

24、. . 72.5.2 Moisture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72.5.3 Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

25、 . . . . . . . . 72.5.4 Lumen Depreciation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72.5.5 Reducing Batch Variations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

26、. . . . . . . 72.5.6 Chip-level Light Extraction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82.5.7 Light Degradation and Color Uniformity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

27、 92.6 Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92.7 Safety . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

28、 . . . . . . . . . . . . . 92.8 Environmental and Disposal Issues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93.0 LED Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

29、. . . . . . . . . . . . . . . . . 93.1 Existing Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .93.2 Potential Future Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

30、 . . . . . . . . . . . . . . . . . .10Annex A For Further Reading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11Annex B Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

31、. . . . . . . . . . . . . . . . . . . . . . . . . .12Technical Memorandum on Light EmittingDiode (LED) Sources and SystemsFOREWORDThe purpose of this Technical Memorandum is todescribe Light Emitting Diode (LED) sources and sys-tems and to answer the most common questions thatthe lighting industry r

32、eceives from the curious public.The authors, all members of the IESNA Light SourcesCommittee, represent a wide cross section of lightingdisciplines from LED-source, lamp, and luminairemanufacturers to lighting-controls producers.While LEDs operate by converting electrical energyinto light energy, th

33、is is the only similarity with otherlight sources in general use today. LEDs look different,are manufactured differently, and are handled differ-ently than other light sources. For example, con-sumers cannot go to their local hardware store andpurchase a replacement “LED lamp.”LEDs are currently bei

34、ng used in advertising signs,keychain and full-power flashlights, exit signs, trafficsignals, and vehicle signaling systems literally hun-dreds of unique applications. Research by dozens ofcompanies is underway to deploy LEDs even further.The ultimate goal is to move these special lightsources into

35、common usage for general lighting wher-ever applicable. Therefore, TM-16 will be updatedfrom time to time to report on industry progresstoward that end.1.0 BRIEF HISTORY OF LEDS1.1 Invention and DevelopmentIn 1962, Nick Holonyak of General Electric inventedthe first practical light-emitting diode op

36、erating in thered portion of the visible spectrum. Throughout thelater 1960s and 1970s, further invention and develop-ment produced additional colors and enabled LEDs tobecome a readily available commercial product.Figure 1 illustrates the advances made in LED tech-nology from the 1960s to the year

37、2000.1.2 Product DeploymentLEDs were initially deployed as indicators in electron-ic measurement devices, and later used in seven-segment alpha-numerics that became briefly popularin digital watches and other display applications dur-ing the early 1970s. Later, as output power and colorvariation imp

38、roved, LEDs were adapted into variousother direct displays including traffic lights and auto-motive applications.Most often associated with the LED is the classic T-134lamp “bullet shape” because early LEDs retained theoutline of the indicator they replaced. Later, surfacemount technology (SMT) pack

39、aging was adoptedbecause it did not require a through-hole when usedon printed circuit boards, and it provided better ther-mal transfer. As power levels increased, new high-fluxpackages were developed to handle the increasedthermal loads.2.0 TECHNOLOGY OF LEDs2.1 How LEDs WorkBasically, LEDs are sol

40、id-state semiconductor devicesthat convert electrical energy into visible light. Whencertain elements (see Figure 2) are combined in spe-cific configurations and electrical current is passedthrough them, photons (light) and heat are produced.The heart of LEDs, often called a “die” or “chip,” iscompo

41、sed of two semiconductor layers an n-typelayer that provides electrons and a p-type layer thatprovides holes for the electrons to fall into. The actualjunction of the layers (called the p-n junction) is whereelectrons and holes are injected into an active region.When the electrons and holes recombin

42、e, photons(light) are created. The photons are emitted in a nar-row spectrum around the energy band gap of thesemiconductor material, corresponding to visible andnear-UV wavelengths.Customers can purchase LED products in many dif-ferent forms since the devices are sold as separatedies or in packages

43、. Engineers, specifiers, and buyersshould be directly involved in the specification of theLEDs, drivers, thermal management technology, andother system components to assure that the endproduct (luminaire) has the performance and liferequired. Often thermal management, mechanicalmounting, driver circ

44、uitry, controls, lenses, and opticsare offered as an optimized lighting system package(see Figure 3).2.2 Types of LEDsDiscrete LEDs may be sold as the die itself. However,most LEDs are purchased in a package which is amuch more usable configuration for the luminairemanufacturer. Figure 4 shows examp

45、les of five differ-ent LED packages on the market today and illustratestheir approximate size.1IESNA TM-16-052.3 Basic Characteristics2.3.1 Materials. Assembled as an LED, phosphidesand nitrides of aluminum, indium, and gallium producelight of different colors and efficacies. The two majormaterial g

46、roups are the InGaP (indium-gallium phos-phide) compounds, used to create red and amber,and the GaN (gallium nitride) compounds, used tocreate blue, cyan, and green. These LED materialscan also generate infra-red and ultra-violet radiationoutside the visible range.2.3.2 Size. LED die sizes range fro

47、m tenths of mil-limeters for small-signal devices to greater than asquare millimeter for the power packages availabletoday. By using multiple dies or groups of packagedLEDs, the light needed by the application can beobtained.2.3.3 Energy Output. The output of an LED is dissi-pated as light and heat.

48、 The light is emitted from theLED die in all directions. Based on the shape of the die,the material from which it is constructed, and the pack-age in which it is assembled, light from the surface of apackaged LED can be captured for use in a lightingsystem. Heat is not radiated (as it is with conven

49、tionallighting technology) but is retained in the LED package.Heat must be effectively conducted away from the dieby the packaging materials or the device leads. Withoutproper thermal management, internally-generated heatcan cause packaged LEDs to fail. No infra-red or ultra-violet energy is emitted in the beam of a visible LED.2.3.4 Color. The color of an LED is determined by thedominant wavelength of the device. Typical single-wavelength LED output falls on the standard CIEchromaticity diagram as shown in Figure 5.2.3.5 “White” LEDs. White light can be obtained fromLEDs by any of