美國(guó)能源部(DoE)最近發(fā)布的名為《LED燈具使用壽命：測(cè)試與報(bào)告建議（LED LUMINAIRE LIFETIME: Recommendations for Testing and Reporting）》的最新修訂版指南對(duì)這一問(wèn)題做了解答。該報(bào)告堅(jiān)持認(rèn)為，LED系統(tǒng)的真正使用壽命一般并不確定。同時(shí)指出，除二極管自身外，不同LED系統(tǒng)的元件構(gòu)造都對(duì)使用壽命有重要的影響，有效的LED系統(tǒng)可靠性評(píng)估必須將所有這些因素考慮在內(nèi)。
DoE指南指出，與照明系統(tǒng)中的其他元件一樣，用于將交流電源轉(zhuǎn)換為適合驅(qū)動(dòng)和控制LED的器件及元件都會(huì)影響到使用壽命和可靠性。電容、電感、變壓器、光隔離器以及其他電氣元件都有不同的設(shè)計(jì)使用壽命，它們受工作及環(huán)境溫度的影響，并容易受到浪涌、尖峰等電氣工作參數(shù)變化的影響。
能效利益相關(guān)者會(huì)發(fā)現(xiàn)有關(guān)電源轉(zhuǎn)換的部分特別有趣。該指南指出，設(shè)計(jì)拓?fù)浣Y(jié)構(gòu)會(huì)影響元件的數(shù)量及類型，進(jìn)而影響到產(chǎn)品的使用壽命。工作溫度也是一個(gè)重要因素（溫度越高，使用壽命就越短），而高效率和低熱阻能降低工作溫度并延長(zhǎng)使用壽命。
該指南還包含有關(guān)LED性能（亮度/輸出和色差/穩(wěn)定性）的信息，并對(duì)將來(lái)的貼標(biāo)應(yīng)如何反映使用壽命測(cè)定提出了建議。
該指南30頁(yè)，下載完整指南，請(qǐng)?jiān)L問(wèn)DoE網(wǎng)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 “l(fā)ive 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.
