1、_SAE Technical Standards Board Rules provide that: “This report is published by SAE to advance the state of technical and engineering sciences. The use of this report is entirely voluntary, and its applicability and suitability for any particular use, including any patent infringement arising theref
2、rom, is the sole responsibility of the user.” SAE reviews each technical report at least every five years at which time it may be revised, reaffirmed, stabilized, or cancelled. SAE invites your written comments and suggestions.Copyright 2012 SAE International All rights reserved. No part of this pub
3、lication may be reproduced, stored in a retrieval system or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of SAE. TO PLACE A DOCUMENT ORDER: Tel: 877-606-7323 (inside USA and Canada) Tel: +1 724-776-4970
4、(outside USA) Fax: 724-776-0790 Email: CustomerServicesae.org SAE WEB ADDRESS: http:/www.sae.orgSAE values your input. To provide feedback on this Technical Report, please visit http:/www.sae.org/technical/standards/J2938_201202SURFACEVEHICLERECOMMENDEDPRACTICEJ2938 FEB2012 Issued 2012-02 LED Light
5、Sources Tests and Requirements Standard Part 2: LED Lumen and Color Maintenance Measurements RATIONALERationale for choosing case temperature (Section 5.2.2) LED lumen degradation and color change over time is a temperature dependent behavior. In general, the higher the junction temperature, the fas
6、ter the lumen depreciation is. The highest or maximum junction temperature is determined and recommended by the LED manufacturer based on the technologies used in the LED package. For LED users, the way in which the LEDs are designed into the automotive lighting application is based on the maximum j
7、unction temperature. Instead of setting a universal case temperature (Ts) to be tested, it is more practical for the LED producers and users, depending on LEDs and the applications, to choose a specific case temperature for a specific type of LED to be tested and reported. In the current practice, s
8、ome LED manufacturers provide LED characteristics relating to case temperature, others refer to junction temperature. Because only case temperature can be directly measured, therefore it is recommended that the case temperature Tsis set, depending on the LED manufacturers specification, either to a
9、temperature such that the junction temperature is within 10 C below the maximum junction temperature claimed by the LED producers. or if the manufacturer only specifies case temperature, then it can be tested within 10 C below the maximum case temperature.Rationale for lumen and color maintenance te
10、sting duration (Section 5.5.4.1) The exterior automotive lighting usage in the US for the life of the vehicle is referred to the reports UMTRI-2008-14 and UMTRI-2008-48 where a 95 percentile duty cycle was assumed which is more appropriate than average usage. In the reports, the annual usage of DRL
11、is presented to be 382.0 h, and for the other (non-DRL) longest use lamps 107.1 h. Based on this information, the life of the vehicle lighting is estimated. If the LEDs used are expected to last the life of vehicle, the lumen maintenance test duration is recommended for 6000 h for DRL and 2000 h for
12、 other lamps.1. SCOPE This SAE Recommended Practice provides test procedures, requirements, and guidelines for the methods of the measurement of lumen maintenance of LED devices (packages, arrays and modules). This document does not provide guidance or make any recommendation regarding predictive es
13、timations or extrapolation for lumen maintenance beyond the limits of the lumen maintenance determined from actual measurements. Copyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-,-SAE J2938 Issued FEB20
14、12 Page 2 of 6 2. REFERENCES 2.1 Applicable Documents The following publications form a part of this specification to the extent specified herein. Unless otherwise indicated, the latest issue of SAE publications shall apply. 2.2 SAE Publications Available from SAE International, 400 Commonwealth Dri
15、ve, Warrendale, PA 15096-0001, Tel: 877-606-7323 (inside USA and Canada) or 724-776-4970 (outside USA), www.sae.org.SAE J1889 LED Signal and Marking Lighting Devices SAE J2650 Performance Requirements for Light Emitting Diode (LED) Road Illumination Device Systems SAE J573 Miniature Lamp Bulbs 2.3 I
16、ES Publications Available from IES, 120 Wall Street, 17thFloor, New York, NY 10005, Tel: 212-248-5000, www.ies.org.IES LM-80-08 Measuring Lumen Maintenance of LED Light Sources IES TM-21-11 Projecting Long Term Lumen Maintenance of LED Light Sources 2.4 Related Publications The following publication
17、s are provided for information purposes only and are not a required part of this SAE Technical Report.UMTRI-2008-14 Rear-World Frequency of Use of Lighting EquipmentUMTRI-2008-48 LEDs and Power Consumption of Exterior Automotive Lighting: Implications for Gasoline and Electric Vehicles3. DEFINITIONS
18、 3.1 DUTDevice Under Test (LED package, arrays and modules) 3.2 LED LIGHT SOURCE (SAE J573) A light source where the visible radiation is emitted from one or more LEDs. An LED light source may or may not require an additional electronic control unit (gear) and may or may not require additional provi
19、sions for thermal management 3.3 LED PACKAGE (ANSI/IES RP-16-10) An assembly of one or more LED dies that includes wire bond or other type of electrical connections, possibly with an optical element and thermal, mechanical, and electrical interfaces. Power source and ANSI standardized base are not i
20、ncorporated into the device.Copyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-,-SAE J2938 Issued FEB2012 Page 3 of 6 3.4 LED MODULE (ANSI/IES RP-16-10) An assembly of LED packages (components), or dies o
21、n a printed circuit board or substrate, possibly with optical elements and additional thermal, mechanical, and electrical interfaces that are intended to connect to the load side of a LED driver. Power source and ANSI standard base are not incorporated into the device.3.5 LUMEN MAINTENANCE (IES LM-8
22、0-08) Lumen maintenance is the luminous flux output remaining (typically expressed as a percentage of the maximum output) at any selected elapsed operating time. Lumen maintenance is the converse of lumen depreciation.3.6 LUMEN MAINTENANCE LIFE (IES LM-80-08) The elapsed operating time at which the
23、specified percentage of lumen depreciation or lumen maintenance is reached, expressed in hours. Operating time does not include the elapsed time when the light source is cycled off or periodically shut down.3.7 LED SOURCE FAILURE The condition where a LED source fails to produce light.3.8 CASE TEMPE
24、RATURE, Ts(IES LM-80-08) Tsis the temperature of the thermocouple attachment point on the LED light source package as defined by the manufacturer of the package. 3.9 MAXIMUM JUNCTION TEMPERATURE, Tj, maxTj, max is the maximum junction temperature for operating LEDs specified by the manufacturer of t
25、he LED package. 4. MARKINGS 4.1 Sample Marking Individual DUTs shall be tracked during life and lumen maintenance testing. Samples can be identified by markings applied directly to the samples or by labels that can be attached to samples during transport and evaluation or to the life test rack posit
26、ion occupied by the sample during life test. 4.2 Sample Selection Sample DUTs shall be selected to be sufficiently representative of the overall population being tested. The sampling method and sample size used shall be reported.5. TESTS 5.1 General Clean DUTs shall be used to limit handling marks o
27、r contaminations of the surface. The manufacturers handling instructions must be observed, in regards to electro-static discharge, ESD. 5.2 Environmental Conditions 5.2.1 Mechanical Static The DUTs should be conducted under mechanically static conditions.Copyright SAE International Provided by IHS u
28、nder license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-,-SAE J2938 Issued FEB2012 Page 4 of 6 5.2.2 Temperature and Humidity The DUT shall be tested at the case temperature Tssuch that Tsis greater than Ts,max minus 10 oC, or Tj, is greater than Tj, max
29、minus 10 C, whatever is appropriate according to the specification of the DUT (See Rationale).Case temperatures shall be controlled to a tolerance of 2 C during lumen maintenance testing. Humidity shall be maintained to less than 65 RH throughout the life and lumen maintenance test. 5.2.3 Airflow Ai
30、rflow shall be minimized for proper DUT starting and operation because of heat flow characteristics that differ due to variation in airflow. Because some air movement is necessary to avoid thermal stratification, care should be taken to minimize any drafts in the immediate vicinity of the devices un
31、der test.5.2.4 Operating Orientation and DUT Spacing The operating orientation of the DUT should be as specified by the manufacturer. In general, orientation will not affect LED light sources as they are solid-state but there may be effects from convection airflow due to heat-sinks and thermal manag
32、ement. The units shall be spaced to allow airflow around each test sample. This is facilitated by designing open life testing racks with minimal structural components to block airflow. 5.3 Electrical Conditions 5.3.1 Input Voltage and Current Input voltage shall conform to the rated input (rms) volt
33、age, the direct current( dc) and ripple voltage shall not exceed 2% of the required dc input voltage. The operating current of the DUT shall be the same current as in typical operation.5.3.2 Input Current Regulation The input current shall be monitored and regulated to within 2 % of the rated rms va
34、lue during life testing and to 0.5 % of the rated rms value during photometric measurements. For low power LEDs in which the operating current is less than 100 mA, the tolerance of 5 % of the rated rms value during life testing is acceptable. The drive currents shall be maintained over the entire pe
35、riod of the operation of the LED light source. The current can be de-rated as a function of temperature in accordance with the manufacturers recommendation. The intent is to test the LEDs at the same current as in typical operation. 5.3.3 Auxiliary Equipment Including Drivers For LED light sources w
36、ithout integrated auxiliary equipment, external drivers compliant with manufacturers guidance shall be used. 5.4 Case Temperature The case temperature Ts, shall be monitored during life testing. Tsis measured directly on the component at the manufacturer-designated case temperature measurement point
37、 (e.g., thermocouple attachment point) on the LED unit. A heat sink meeting the recommendations of the manufacturer should be used. Copyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-,-SAE J2938 Issued FE
38、B2012 Page 5 of 6 5.5 Test and Measurement Procedures 5.5.1 Instrumentation In life and lumen maintenance testing, accurate recording of elapsed operating time is critical. If used, an elapsed time meter shall be connected to the particular test positions and shall accumulate time only when the inst
39、alled DUTs are energized. In the event of a power failure to a position, monitoring devices shall not accumulate time. Video monitoring, current monitoring, or other means shall be used to determine elapsed operating time if designed to provide sufficient temporal accuracy. All equipment calibration
40、 shall be in accordance with manufacturer specifications. Total elapsed time uncertainty should be within 0.5%. 5.5.2 Photometry Measurement Photometric measurements shall be in conformance with the appropriate laboratory method for the LED light source under test. Luminous flux shall be measured at
41、 the drive current used during life testing. Ideally, the drive current should be set at the drive current used in determining the manufacturers literature rating of luminous flux. Because the color stability over life is an important parameter for many lighting applications, the chromaticity values
42、 shall be determined. It is strongly recommended that photometric and colorimetric values be determined from total spectral radiant flux measurements using a spectroradiometer. 5.5.3 Photometry Measurement Temperature The ambient temperature during lumen and chromaticity measurements shall be set at
43、 25 C + 2 C. The ambient temperature throughout the test duration shall be provided in the test report for each photometric measurement. The LED light source shall be permitted to cool to room temperature prior to measurement. 5.5.4 Lumen Maintenance 5.5.4.1 Lumen Maintenance Testing Duration and In
44、terval At the specified case temperature noted in Section 5.4 the DUT shall be operating for at least 2000 h or 6000 h for DRL or Heavy Duty vehicle applications with data collection at minimum intervals of 500 h or 1000 h for DRL or Heavy Duty vehicle applications (see Rationale). For longer than 6
45、000 h lumen maintenance life requirement, IES TM-21-11 shall be used to make a corresponding lumen maintenance projection. 5.5.4.2 Operating Cycle Unlike other sources where power cycling adversely affects lifetime and performance, LEDs can be 100% modulated at high rates with little effect on lifet
46、ime. However, the devices and modules shall be driven at constant current to remove any issues of modulation affecting results. Drive methods shall be reported. 5.5.4.3 Recording Failures Checking for DUT failures either by visual observation or automatic monitoring shall be done at a minimum of eve
47、ry measurement interval. Each failure shall be investigated to make certain that it is actually an LED light source failure and is not caused by improper functioning of the auxiliary equipment or electrical connections. Catastrophic LED light source failure shall be reported and included in the test
48、 report. 5.5.4.4 Chromaticity The chromaticity shift shall be measured and reported over the course of the lumen maintenance test time by measuring chromaticity at each photometric test interval. Copyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-,-SAE J2938 Issued FEB2012 Page 6 of 6 5.6 Test Report The report shall list all pertinent data concerning conditions of testing, type of equipment, and types of devices being tested. The following items shall be included in the test repo
