ASSIST Recommends: Recommendations for the Definition and Specification of Useful Life for Light-Emitting Diode Light Sources (original) (raw)
Related papers
Lumen Maintenance and Light Loss Factors: Consequences of Current Design Practices for LEDs
LEUKOS, 2013
Light loss factors are used to help lighting systems meet quantitative design criteria throughout the life of the installation, but they also carry ancillary consequences such as influencing first cost and energy use. As the type of light sources being specified continues to evolve, it is necessary to carefully evaluate the methods used in calculating light loss factors, as well as understand the broad effects of performance attributes like lumen maintenance during the selection process. Because of the unique operating characteristics of LEDs and lack of a comprehensive lifetime rating-as well as the problematic relationship between lifetime and lumen maintenance-determining an appropriate lamp lumen depreciation (LLD) factor for LED products is difficult. As a result, a unique solution has been advocated: when quantity of light is an important design consideration, the IES simply recommends using an LLD of not greater than 0.70. This method deviates from the typical practice for conventional sources of using the ratio of mean to initial lumen output, and can misrepresent actual performance, increase energy use, and inhibit comparisons between products. This paper discusses the complications related to LLD and LEDs, compares the performance of conventional and LED products, and examines alternatives to the current recommended approach for determining LLDs for LED products.
Projecting LED product life based on application
Fifteenth International Conference on Solid State Lighting and LED-based Illumination Systems, 2016
LED products have started to displace traditional light sources in many lighting applications. One of the commonly claimed benefits for LED lighting products is their long useful lifetime in applications. Today there are many replacement lamp products using LEDs in the marketplace. Typically, lifetime claims of these replacement lamps are in the 25,000-hour range. According to current industry practice, the time for the LED light output to reach the 70% value is estimated according to IESNA LM-80 and TM-21 procedures and the resulting value is reported as the whole system life. LED products generally experience different thermal environments and switching (on-off cycling) patterns when used in applications. Current industry test methods often do not produce accurate lifetime estimates for LED systems because only one component of the system, namely the LED, is tested under a continuous-on burning condition without switching on and off, and because they estimate for only one failure type, lumen depreciation. The objective of the study presented in this manuscript was to develop a test method that could help predict LED system life in any application by testing the whole LED system, including on-off power cycling with sufficient dwell time, and considering both failure types, catastrophic and parametric. The study results showed for the LED A-lamps tested in this study, both failure types, catastrophic and parametric, exist. The on-off cycling encourages catastrophic failure, and maximum operating temperature influences the lumen depreciation rate and parametric failure time. It was also clear that LED system life is negatively affected by on-off switching, contrary to commonly held belief. In addition, the study results showed that most of the LED systems failed catastrophically much ahead of the LED light output reaching the 70% value. This emphasizes the fact that life testing of LED systems must consider catastrophic failure in addition to lumen depreciation, and the shorter of the two failure modes must be selected as the system life. The results of this study show a shorter time test procedure can be developed to accurately predict LED system life in any application by knowing the LED temperature and the switching cycle.
LEDs' operation optimizing for long term lumen maintenance
33rd International Spring Seminar on Electronics Technology, ISSE 2010, 2010
Investigations deals with optimization of operating regimes of LEDs in lighting equipment for obtaining two purposes-maximum light output in dependence of ambient conditions and long term lumen maintenance. Thermal management calculations and heat sink choice are experimentally tested at various ambient conditions (air temperatures from 20ºC to 55ºC) and different current values through LEDs-up to 700 mA. Infrared thermography is used for evaluation of temperature distribution on LEDs and heat sink. Thermal management investigations allow determining safety operating conditions for LEDs at maximum light output in dependence of ambient conditions.
Life of LED-based white light sources Life of LED-Based White Light Sources
—Even though light-emitting diodes (LEDs) may have a very long life, poorly designed LED lighting systems can experience a short life. Because heat at the p-n-junction is one of the main factors that affect the life of the LED, by knowing the relationship between life and heat, LED system manufacturers can design and build long-lasting systems. In this study, several white LEDs from the same manufacturer were subjected to life tests at different ambient temperatures. The exponential decay of light output as a function of time provided a convenient method to rapidly estimate life by data extrapolation. The life of these LEDs decreases in an exponential manner with increasing temperature. In a second experiment , several high-power white LEDs from different manufacturers were life-tested under similar conditions. Results show that the different products have significantly different life values.
Extending the lifespan of LED-lighting products
Http Dx Doi Org 10 1080 17452007 2013 834813, 2015
ABSTRACT Light Emitting Diodes (LED) lighting products require more reliable data to inform Life Cycle Assessment. Understanding why and when they fail under real operating conditions provides better data for this assessment contributing to: (1) understanding of how to extend its lifespan, (2) informing design recommendations to extend their lifespan and (3) reducing the total amount of waste produced by LED lighting products. This paper investigates the life span of LED lighting products under real operating conditions and explores the causes of failure or replacement of the products. The study consisted of close-ended questionnaires distributed to LED lighting product manufacturers and consumers in four EU countries. Out of 140 respondents of the questionnaire survey, 57 were manufacturing organizations and 83 were consumers. The results indicate that: (1) the causes of failure were primarily due to wear and tear of components, and changes in consumer requirements; (2) the consumers' survey showed that, the lifespan is 27,375 h in the best case scenario and 1460 h in the worst case scenario, indicating that the worst case scenarios can be substantially improved through proper use and maintenance, as well as selection of products with features to enhance the lifespan; (3) the manufacturers' survey showed that, the lifespan is 32,850 h in the best case scenario and 3650 h in the worst case scenario, indicating the need for better design and manufacturing guidelines to extend their lifespan. The paper concludes with recommendations for both manufacturers and consumers, based on a combined analysis of the survey data and a comprehensive literature review of recommendations to extend the lifespan of LED lighting products.
Lifetime and optical analyses of LED lamps
Revista Brasileira de Aplicações de Vácuo, 2021
In this study, optical and lifetime analyses of commercial light-emitting diode (LED) lamps were carried out with the objective to better understand these characteristics. Lamps of different manufacturers and powers were used: Ourolux of 9 watts, Kian of 9 watts, Black+Decker of 9 watts, FLC of 8 watts, Galaxy of 7 watts and Brilia of 7 watts. These LED lamps remained on by 24 hours/day for 4,291.16 hours. Illuminance measurements were analyzed once a week by each lamp inside the integrating sphere with a sensor of lux meter coupled. Results showed decrease of illuminance by elapsed time, due to the degradation. Results of the illuminance obtained between the initial moment of the experiment and the final one were calculated, revealing degradation of 19% to Ourolux, 20% to FLC, 26% to Black+Decker, 28% to Kian, 29% to Galaxy and 33% to Brilia. This study suggests that the diffusers can have different transmittance values interfering on the illuminance, since the FLC LED lamp present...
The goal of this paper is to initiate a discussion within the lighting community regarding standardized measurement procedures and a definition for useful life for light emitting diode (LED) technology. In general, LEDs do not fail catastrophically, but instead their light output slowly decreases over their operating period. Presently, some manufacturers use a 50% light output level as the criterion for LED life. Although 50% light loss might be acceptable for noncritical signage applications using monochromatic LEDs, it might not be acceptable for general lighting applications. It is important to develop a method for rating lamp life and a definition of "useful life" for LEDs so that when reported by manufacturers, the lighting community can compare LEDs to traditional light sources. The "useful life" definition for LEDs should consider light loss and color shift. Therefore, an experimental study was conducted to investigate light loss and color shift patterns of white LEDs as a function of operating time. The 5-mm type white InGaN +YAG LEDs evaluated in this experiment, representing technology commercially available in 1999, exhibited high light output degradation rates and color shifts as a function of operating time. It is further shown that using a simple mathematical fit to the data gathered during a short life-test study, and extrapolating it to predict the life of white LEDs, depends on the initial data collection period. Therefore, an alternate method for projecting LED life is investigated by overdriving the LEDs at different currents. Using their degradation patterns at higher drive currents, the life of these LEDs was predicted at normal drive current values. The results show excellent correlations between predicted light loss and actual measured losses at 20 and 30 mA drive currents for the LEDs tested. The authors believe that this technique is applicable for accurately predicting life of any type of LED and hope to verify this using future configurations. This study adds information to the knowledge needed for the lighting community to develop standardized measurement procedures and a definition for useful life for LED technology.
An Efficiency-Decay Model for Lumen Maintenance
IEEE Transactions on Device and Materials Reliability, 2016
Proposed is a multicomponent model for the estimation of light emitting diode (LED) lumen maintenance using test data acquired according to Illumination Engineering Society of North America test standard LM-80-08. Lumen maintenance data acquired with this test do not always follow exponential decay, especially data collected in the first 1,000 hours or under low stress (e.g., low temperature) conditions. This deviation from true exponential behavior makes it difficult to use the full data set in models for the estimation of lumen maintenance decay coefficient. As a result, critical information relevant to the early life or low stress operation of LED light sources may be missed. We present an efficiency-decay model approach where all lumen maintenance data can be used to provide an alternative estimate of the decay rate constant. The approach considers a combined model, one part of which describes an initial "break-in" period, and another part the decay in lumen maintenance. During the break-in period, several mechanisms within the LED can act to produce a small (typically < 10%) increase in luminous flux. The effect of the break-in and its longevity is more likely to be present at low ambient temperatures and currents, where the discrepancy between a standard TM-21 approach and ours is the largest. For high temperatures and currents the difference between the estimates becomes nonsubstantial. Our approach makes use of all collected data and avoids producing unrealistic estimates of the decay coefficient.
Review and Proposals for Upgrade of Metrics of Useful Lifietime of Professional Led Luminaires
PROCEEDINGS OF the 29th Quadrennial Session of the CIE, 2019
The expected useful lifetime of professional LED luminaires has been extended tremendously due to LED technology arriving in a mature stage. On the other hand, there is a market pressure to claim longer and longer useful lifetime, sometimes without knowing the limitations of methods of prediction used and/or having real benefit for the end-users. The paper will review the limitations of predictions and gives proposals how to improve the confidence level. The author also will evaluate whether extreme long useful lifetime claimed by manufacturers have a real benefit for the end-users. There are proposals, how better luminous flux maintenance can be turned to real benefit the lighting installation by modification of metrics.
Development of a fully automated LED lifetime test system | NIST
2012
A fully automated system for light-emitting diode (LED) lifetime test has been developed and is undergoing validation. This system uses a 1 m integrating sphere for both ageing and optical measurements of 480 LEDs. It features six test zones, each of which holds an LED load board with 80 LEDs. Each zone operates independently, executing a user-entered recipe that defines current (to 5 A), voltage (to 200 V), mode (continuous on, pulsing, or cycling), and temperature (from 25 °C to 115 °C). LED ageing and light measurement occurs without the requirement to move the LED load board since the Thermal Electric Cooler (TEC) based temperature zones are enclosed within the sphere. This fully automated system addresses several challenges inherent with existing methods that require costly labour to move LED load boards from thermal control chambers to light measurements spheres. Using the new system, frequent light measurements are possible with small measurement uncertainties and a reduced o...