- What is Lumen Maintenance ?
It is important to get know well of lumen first. As usually, we refer to the amount of light emitted by the LED light source per unit time as the luminous flux, unit: lumen, LM. The amount of light is for light source, description of size of the total amount of light emitted by the light source, equivalent to the luminous power, and greater the luminous flux of the light source, the more light is emitted. When a luminaire ignites under specified conditions, the ratio of the luminous flux at a particular time during the life of the lamp to that of the initial of the lamp, expressed as a percentage. The luminous flux will be decreasing as increasing ignition time, so the effective life is defined by the lumen maintenance rate. When the luminous flux maintenance rate is lower than 50%, it can be regarded as the lamp has reached the service life, but the national standard requires the lumen maintenance rate of 2000H to be not less than 78%, the advanced level in foreign countries requires not less than 90% on same situation; the standard of the US Energy Star is that the lumen maintenance rate is not less than 80% at 40% of rated life.
A noun refers to “light degradation”, corresponding to the lumen maintance, of which is inversely proportional each other. The light degradation of LED is mainly affected by the following two factors:
1. LED quality: LED chip in it is not good, and brightness is attenuation in a faster speed. There exsits defect craft during production, and the heat dissipation of the LED chip cannot be well derived from the PIN pin, resulting in an excessive temperature of the LED chip, which intensifies the chip attenuation.
2. Using surroundings: The LED is driven by a constant current, and some of the LEDs are driven by voltage, which will make the LED attenuate faster. Obviously, the lumen maintenance rate is the core factor for judging the advantages and disadvantages of LED light sources.
- What is LM-80 ?
As is well -known, working under a standard current and condition, LED will keep a long worklife, 50000 hours even longer. During spending the entire life, the LED light output is slowly depreciation , the spectrum may shift, resulting in color and luminious efficacy failure. In order to better promote the standard development, testing and certification of LED lighting product and regulate the LED market flourish, IESNA and ANSI jointly issued the LM-80 certification and TM-21.
In generally, LM-80 is a test for LED packages, arrays, and maintance lumen and color of modules. The testing time need to reach 6000 hours according to standard of Energy Start and IESNA LM-80, which can allow to do LM-80 testing certificate and reports using LED package, array, module optics. This report is a world-recognized international certification for the performance of products with a world-recognized and credible method, an important criterion for the quality of LED light sources.
In the LM-80 report, testing is required at least one product, at the same current, at three different temperatures (55 ° C / 85 ° C / optional temperature). When the LED device is used in the finished product, it will test the temperature of its corresponding point and the driving current of the LED. Comparing the temperature and current conditions of the finished product with the temperature and current conditions in the report, if the conditions in the report are more stringent, the reported data can be adopted.
During the LM-80 test, the aging process needs to be separated from the test process. The aging process must strictly control the temperature of the Tc to 55 degrees, 85 degrees, or the temperature specified by the supplier. After aging to the specified test interval, return to the test environment for photometric testing. The LM-80 requires testing of luminous flux and color parameters, and has high requirements for environmental control, temperature control of Tc, and power supply equipment, also has detailed requirements for tracking and recording of samples and aging processes. It can be said that passing the LM-80 certification is the highest recognition of the product, and it also means that it has achieved international leadership in terms of lumen maintenance and life, and can meet the demanding needs of the high-end LED intelligent lighting market.
- How to judge a qualified LM-80 report?
How to assess the lumen maintenance rate of LED products is an important parameter to determine the quality of products, and is also an important indicator to distinguish the quality of light sources. The importance of LM80 to LED products is self-evident. So, how to judge whether a LM-80 report is qualified or not? In this regard, There are several points that are worthy of attention: 1, The luminous attenuation percentage and attenuation curve of the test product. 2, The color drift of the test product, that is, the color difference between 6000 hours and 0 hours.
Secondly, it is also worth noting whether the LM-80 reports has authorization, whether it meets the standard of test requirements, whether the sample quantity meets the requirements of the finished product energy efficiency certification, whether the color difference meets the standard requirements, whether the percentage of attenuation and its estimated life can meet the requirements.