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Value can be calculated: Understanding LM-80

Value can be calculated: Understanding LM-80

Technology News |
By eeNews Europe



The LED marketplace is often referred to as “The Wild Wild West.” Though you’re unlikely to see cowboys, cattle or tumbleweed at a lighting tradeshow, the comparison is apt. The market is a seemingly lawless place where outlaws are free to roam unpunished, releasing products to the market that may or may not live up to their stated performance and lifetime claims.

At the same time, government agencies, lighting standards organizations and major manufacturers are attempting to tame the market by adapting LED best practices from other industries, such as the automotive and semiconductor industries, which have long-term experience with the technology. The intent here being to implement standards that enable lighting professionals to easily evaluate and compare LED components, lamps and luminaires. (In other words, to “civilize” the Wild West.)

WHAT IS LM-80?

The LM-80 is one such standard. LM-80 refers to a method for measuring the lumen depreciation of solid-state lighting sources, such as LED packages, modules and arrays. Before the advent of LM-80, LED component manufacturers each reported lumen maintenance data using their own disparate and varied systems. To avoid customer confusion, members of the Illuminating Engineering Society (IES), including members from Philips Lumileds, came together to create a standard methodology that would allow customers to evaluate and compare the lumen maintenance of LED components from different companies. LM-80 was born.

LM-80 can be a useful tool for lighting professionals who are looking to analyze LED products; however, it is not a measure of LED system performance or reliability. It only describes how to measure how one part of an LED luminaire—the LED light source—performs over a period of time and under certain set conditions. Other components, including the LED optical system, heat sink, LED drivers and luminaire housing, should also be taken into consideration to form a full picture of an LED luminaire’s projected useable life. LM-80 is merely one critical part of a larger puzzle. LM-80 is also not a measure of the “lifetime” of a component or the LED lamps and luminaires that use that component. Unfortunately, LED component, lamp and luminaire manufacturers, among others, often use the data found in an LM-80 report to substantiate the “lifetime” claims of an LED product, even though that data alone cannot be used to predict the useful life of an LED product or system.

WHAT LM-80 CAN DO FOR YOU

While LM-80 doesn’t provide a full picture of a LED component’s long-term performance, it is an important part of the equation. Luminaire and lamp manufacturers, lighting designers and researchers should know how quickly the light output of an LED will depreciate to help them determine the useful lifetime of the product in which the LED will be used. They should also look at how the LED’s light output has degraded under the various temperature and current conditions, as well as how the color point has shifted at those same conditions. Those measurements will enable them to assess how the LED component is expected to perform under similar circumstances.

Figure 1a/b: Samples of data from a Philips Lumileds LM-80 test report, showing light output over time for the same LED. The first graph show results of the LED tested at 350mA and the second graph at 500mA.

LM-80 can also be useful in helping manufacturers earn a coveted ENERGY STAR® rating for their products. In fact, those who manufacture LED lamps for sale in the U.S. can only obtain an ENERGY STAR product qualification for an LED lamp if the lamp has undergone LM-80 testing. To make it faster for lamp manufacturers to obtain the qualification and get their product to market, the U.S. Environmental Protection Agency (EPA) now allow manufacturers to get an interim ENERGY STAR qualification with only 3,000 hours of testing if the manufacturer can provide an LM-80 test report for the LED component. This allows lamp manufacturers to apply for refund programs up to 18 weeks earlier than manufacturers that do not provide the LED component LM-80 test data to the certification organizations.

Additionally, many other countries outside of the U.S., including Australia, now use the ENERGY STAR program requirements as a benchmark for LED standards in their own country. LM-80 data is thus crucial for manufacturers outside of the U.S. as well who want their LED lamps to meet that benchmark. Luminaire manufacturers that exceed the minimum 6,000 required test hours for LM-80 can extend their “lifetime claims” by six times the actual test hours. For example, Philips Lumileds tests several of its popular LUXEON products for 10,000 hours or longer, so that our customers can claim a 60,000-hour-or-more lifetime for their products as opposed to a 36,000-hour lifetime (based on the minimum 6,000-hour test requirement).

HOW TO ACCESS LM-80 DATA

Despite the fact that LM-80 was created to inform customers of manufacturers’ testing results, many manufacturers don’t allow the public to access their LM-80 data or make accessing the data cumbersome. Sharing the data available online is one way to make it more accessible.

As part of its suite of online LED applications tools, Philips Lumileds now offers an LM-80 reporting tool that enables users to quickly and easily access LM-80 data for the majority of its LED components designed for general lighting. The tool offers customers the ability to generate a custom LM-80 report, tailored to their specific drive conditions. This can help a lamp or luminaire manufacturer streamline their development and qualification process. And because online content is much easier to update than a printed document, an online reporting tool enables manufacturers to keep their LM-80 material current.

Fig. 2: To make LM-80 data more accessible and transparent for its customers, Philips Lumileds has created an online tool that allows customers generate LM-80 test reports based on criteria specific to their application. For higher resolution click here.

In conclusion, to assuage consumers’ fears about LEDs’ long-term performance, manufacturers must make test data, like LM-80 results, available to the public and provide the data in a meaningful, easy-to-use format. Consumers must be reminded, however, that LM-80 is only one part of a larger puzzle. All pieces of the puzzle must be considered to make a fully informed judgment about the long-term performance of an LED-based product.

About the Author:

Rudi Hechfellner is the Director of Applications at Philips Lumileds Lighting. After more than 16 years of developing innovations for technically advanced projects in the semiconductor industry, Hechfellner joined Philips Lumileds Lighting in 2005. Prior to joining Philips Lumileds Lighting he was an applications engineer for ASICs with focus on high-speed I/O interfaces. Hechfellner holds an Electronic Engineering degree from FH Augsburg, Germany.

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