美国能源部(DoE)最近发布的名为《LED灯具使用寿命：测试与报告建议（LED LUMINAIRE LIFETIME: Recommendations for Testing and Reporting）》的最新修订版指南对这一问题做了解答。该报告坚持认为，LED系统的真正使用寿命一般并不确定。同时指出，除二极管自身外，不同LED系统的元件构造都对使用寿命有重要的影响，有效的LED系统可靠性评估必须将所有这些因素考虑在内。
DoE指南指出，与照明系统中的其他元件一样，用于将交流电源转换为适合驱动和控制LED的器件及元件都会影响到使用寿命和可靠性。电容、电感、变压器、光隔离器以及其他电气元件都有不同的设计使用寿命，它们受工作及环境温度的影响，并容易受到浪涌、尖峰等电气工作参数变化的影响。
能效利益相关者会发现有关电源转换的部分特别有趣。该指南指出，设计拓扑结构会影响元件的数量及类型，进而影响到产品的使用寿命。工作温度也是一个重要因素（温度越高，使用寿命就越短），而高效率和低热阻能降低工作温度并延长使用寿命。
该指南还包含有关LED性能（亮度/输出和色差/稳定性）的信息，并对将来的贴标应如何反映使用寿命测定提出了建议。
该指南30页，下载完整指南，请访问DoE网站http://apps1.eere.energy.gov/buildings/publications/pdfs/ssl/led_luminaire-lifetime-guide_june2011.pdf。
LED LUMINAIRE LIFETIME: Recommendations for Testing and Reporting
Solid-State Lighting Product Quality Initiative
SECOND EDITION JUNE 2011
Next Generation Lighting Industry Alliance with the U. S. Department of Energy
CONTENTS
Introduction .......................................................... 3
Understanding SSL Luminaire Lifetime .............................. 3
What This Guide Is and Is Not ..................................... 4
Failure, Reliability, and Lifetime .................................... 5
Reliable Design and Manufacturing ................................. 8
End of Life ....................................................... 11
Serviceability and Lifetime ....................................... 12
Lifetime for Non-Serviceable LED-Based Luminaires ............... 12
Lifetime for Serviceable LED-Based Luminaires ................... 13
Key Issues for Reliability and Lifetime ............................... 14
LED Lumen Depreciation ............................................ 14
LED Drivers and Controls .......................................... 14
Types of Power Conversion ....................................... 15
LED Drivers ..................................................... 15
Standards, Regulations, and Protection .......................... 16
Color Shift ....................................................... 17
Relation of Color Shift to Lifetime ............................. 17
Segmentation of the Luminaire Market ............................ 21
Standards and Measurement Work .................................. 21
Specifying and Demonstrating Lifetime ................................. 22
Lifetime Specification............................................. 22
Optional Specifications ......................................... 23
Determining and Maintaining Specified Lifetime .................... 24
New Platform Lumen Maintenance .................................. 24
Product Variation of New Platform ............................... 25
Additional Considerations ............................................. 26
Design for System Reliability ..................................... 26
Labeling Recommendations .......................................... 27
Other Options ................................................... 27
The Role of Warranties .......................................... 28
Recommended Further Reading ........................................... 29
Acknowledgements ...................................................... 30
Surprisingly to many, the true reliability and lifetime of light-emitting diode (LED) lighting systems is generally not known. Even worse, lumen maintenance values of LED devices are widely used as a proxy for the lifetime of an LED lighting system, which is misleading since lumen maintenance is but one component of a luminaire’s reliability. In fact, quite often the lifetime of a well-designed and manufactured luminaire is not determined by LED lumen depreciation. For many manufacturers estimating the luminaire lifetime using LED lumen maintenance, results can be ascribed to dependence on readily available numbers without developing actual luminaire data. In many cases, neither product providers nor customers are aware of the differences, perhaps in part because the problem has not been sufficiently explored and communicated.
It isn’t just about the LED. Good LEDs can be incorporated into poorly engineered products and turn the Methuselah of lighting into the exponent of “live fast, die young.” The promise of LED lifetime is often presented in terms of hours and years but with little background data. Warranties as well may be misstated because of this lack of data, at the manufacturer’s peril. The statement “100,000 hours of LED luminaire lifetime” is gradually giving way to the realization that there is little consistency, very little published data, and few hard facts around so-called luminaire lifetime numbers. The situation is better at the LED package level, where reputable manufacturers have thousands of hours of data under varying conditions. But this is not enough.
To manufacturers and specifiers in the solid-state lighting (SSL) community, the dawning realization is that we need to work together toward understanding the issues surrounding true lifetime and reliability. We need to begin by cataloguing failures and developing good models for underlying failure mechanisms. This process of understanding and explanation is very common in technological progress—steam engines existed long before deep comprehension of thermodynamic processes. With LEDs, we have a substantial head start on the underlying physics, many years of experience in both lighting and semiconductors, and reliability of related products.
As stated in the first edition of this guide, released in June 2010, there is no reason not to begin this journey and every reason to start. Now, one year later, we continue to pursue better reliability methods and metrics and explore the underlying root causes of failure.
