Understanding the Lifespan of LED: Insights and Innovations

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LED technology, originating in the semiconductor sector, is currently thriving in the lighting industry. As a relatively new innovation, it raises numerous questions and opportunities for discovery. LEDs are renowned for their exceptionally long lifespan. Yet, how can we accurately predict the lifespan of an LED without substantial testing? How does it compare to traditional light sources? This article delves into comparisons between LED and traditional lighting and discusses recent standards developments to enhance your understanding of what LED lifespan truly means.

Background on LED Development

The lifespan of conventional light sources largely depends on filament longevity. In contrast, LEDs, which operate on the principle of semiconductor light emission and lack a filament, inherently promise a longer lifespan. Additionally, their low power consumption offers a breakthrough in energy conservation and emission reduction, which is crucial as global energy resources tighten and greenhouse effects intensify.

Confusion Over LED Lifespan

The touted long lifespan of LEDs is central to their appeal, often claimed to exceed 50,000 hours. However, this advantage may not be immediately apparent to end-users. Several factors contribute to this disconnect: the novelty of LED products limits direct consumer experience; market saturation with inferior, low-cost products undermines user satisfaction; unsubstantiated longevity claims lead to skepticism; and questions arise about the necessity of replacing LEDs given their long life. Moreover, LED’s roots in the semiconductor industry mean that its lifespan is influenced by numerous factors and is subject to rapid advancements in technology. This complexity can leave even lighting professionals feeling perplexed. How should traditional lighting manufacturers select LEDs to ensure system longevity (covering both the light source and the fixture)? What selection criteria should be used?

The lifespan of LEDs, unlike that of traditional light sources, involves complex variables and ongoing exploration. This article aims to demystify LED lifespan from a standardized perspective, clarify the interconnected factors, and assist lighting companies in choosing reliable LEDs to build dependable systems. It also guides end consumers in making informed choices when purchasing LED products.

Comparing Traditional Light Source Lifespan with LED Lumen Maintenance Lifespan

To fully grasp the longevity of LED lighting, it’s essential first to understand the lifespan of traditional light sources. Traditional light sources have their lifespan determined through widely accepted methods, which are documented in various standards as shown in the table below. This provides a basis for comparing the effective lifespan of LEDs, particularly in terms of lumen maintenance.

Standard of Lamp Lifespan

The standard outlines the test environment, selection of samples, and methodologies. For example, it requires that compact fluorescent lamps be tested at a constant 25°C, cycling through three hours on and 20 minutes off. The point at which half of the samples fail marks the average rated lifespan of the light source.

Unlike traditional light sources, LEDs do not measure lifespan based on lumen maintenance. Why is this the case? For tungsten filament lamps, brightness loss primarily results from filament degradation. Typically, tungsten filament lamps lose only 10% to 15% of their initial brightness over an average rated lifespan of 1,000 hours. In fluorescent lamps, brightness loss is mainly due to the photodegradation of the phosphor coating and the glass tube. Compact fluorescent lamps (CFLs) do not exceed a 20% loss of their initial brightness over their average rated lifespan of 10,000 hours, while high-quality T8 and T5 lamps using rare-earth phosphors lose no more than 5% over 20,000 hours.

For LEDs, light attenuation can occur due to various factors like drive current, junction temperature, phosphor quality, and lens design. Given LEDs’ long theoretical lifespan, extensive testing over many years is required to determine their end of life, termed as “point failure.” Unlike other traditional light sources, LEDs can continue to function even if their brightness decays to 50%, but at this level, can they still fulfill lighting design requirements?

Lighting designers must be sure that the LEDs will emit no less than the required effective luminous flux for the lifespan of their design, not just until the point of failure. This knowledge is crucial for accurately calculating the costs of installation, maintenance, and replacement, and for making comparisons with traditional light sources. Consequently, LED lifespan is often assessed based on the effective life determined by lumen maintenance rates.

Lifespan of different types light bulbs

LED Component Life

Scope of LED

Before discussing LED lifespan, it’s crucial to define what ‘LED’ encompasses. Generally, the term includes both LED components, such as chips, and LED systems—the complete end products used by consumers, which comprise light sources, modules, and fixtures.

LED Component Lifespan and L70, L50 Standards

The definition of lifespan needs clarification. The European standard predominantly follows the IEC guidelines issued by the International Electrotechnical Commission. The U.S. has a more complex set of standards managed by the North American Illuminating Society (IES), the National Electrical Manufacturers Association (NEMA), and the Underwriters Laboratories (UL).

L70 refers to the point at which an LED’s luminous flux has maintained 70% of its original output, marking the useful life of the LED. This concept is crucial as it connects lifespan directly to lumen maintenance, offering a practical and measurable aspect of LED performance. This shorter lifespan metric compared to total failure time simplifies R&D and testing phases for new LEDs.

Variability in Lifespan: B50 and B10

During operation, variations in LED performance due to manufacturing processes and material quality are common. To address potential defect rates realistically, the industry uses B50 and B10 ratings. A B50 L70 rating means that 50% of LEDs maintain more than 70% luminous flux throughout their life. Similarly, B10 L70 indicates only 10% of LEDs fall below 70% luminous flux or fail.

TM-21 Methodology

LEDs can continue to function even when their light output degrades significantly, which is different from traditional lights that fail when they burn out. TM-21 uses data from the IES LM-80 test, which measures lumen maintenance, to predict the long-term performance of LEDs. It stipulates that the projected lifespan cannot exceed six times the duration of the LM-80 test and expresses longevity in terms of Lp (Yk), where P is the lumen maintenance rate and Y is the duration of the LM-80 test in thousands of hours.

Impact of Temperature on LED Lifespan

Temperature plays a vital role in LED lifespan. The LED junction temperature, a critical performance indicator, is influenced by environmental conditions. During LM-80 testing, manufacturers record temperatures at three standard levels—55°C, 85°C, and a manufacturer-specified temperature suited for expected applications—using thermocouples placed on the LED package. This data then helps infer lifespan variations at different operating temperatures through TM-21 analysis.

This section provides a detailed understanding of the factors defining LED lifespan, emphasizing the need for precise standards and reliable testing to gauge and ensure long-term performance.

Reliability and Lifespan of LED Systems

The reliability and longevity of LED lighting systems are often underestimated. Commonly, the lumen maintenance rate of LED components is mistakenly used to represent the entire system’s lifespan. However, the true lifespan of a well-engineered LED system is not solely dependent on LED light decay.

The lifespan of LED fixtures encompasses numerous interconnected components and subsystems, each with varying lifespans and reliability levels. These cannot be evaluated based on their best or worst attributes alone but must be assessed holistically, considering their interactive effects.

For LED systems, dimming light output isn’t the sole reason for replacement. Factors like color shifts and changes in light distribution due to damaged LEDs must also be considered. LM-80 testing underscores the importance of color stability, necessitating that test reports include data on color drift over time.

Choosing components that match the longevity of LEDs isn’t always cost-effective. The goal in designing long-lived systems is to balance potential data against costs—aiming for a system that maintains an acceptable failure rate at a reasonable cost throughout its expected life. Reliability and lifespan are crucial metrics for assessing an LED system’s effective lifespan.

Factors Affecting LED System Reliability:

• Design Flaws: These often include inadequate thermal management, incompatible chemical use leading to lens or chip degradation, insufficient LED driving, chip overloading, and poor sealing that permits moisture ingress.
• Manufacturing Defects: Inherent in production, these defects are typically linked to early failures which increase with production scale. Manufacturers can mitigate such defects through rigorous factory testing and aging processes.
• End of Life: The failure of critical system components can render an LED system non-functional. Selecting appropriate components and accurately estimating their lifespan is essential.

The complexity of determining LED lamp lifespan through long-term light decay observation is immense. Moreover, as awareness grows, the focus shifts to LED control devices’ lifespan, particularly influenced by the electrolytic capacitors used. Capacitor life declines with increased temperature and operational duration, with a 10-degree rise halving its lifespan.

For a detailed discussion, refer to “Temperature of LED: Do Electrolytic Capacitors Significantly Shorten LED Lifespan?“.

Determining the lifespan of LED lighting products is challenging. Yet, it is vital for consumers to understand these aspects to weigh the energy efficiency, maintenance costs, and initial investment, and make well-informed purchasing decisions.

This discussion aims to deepen your understanding of LED component and system lifespans, guided by current insights and standard developments within the lighting industry. If you have questions or need further clarification, feel free to contact us directly.

FAQs about LED Lifespan