LM-80 in LED Lighting

The life of LED is still a characteristic of long -term attention. The theoretical life of LED is very long. Like the traditional light source uses a 2H45MIN and the 15 minutes cycle test to the end of life, the measurement of LED products is obviously unrealistic. Therefore, it is necessary to use the accelerated aging life test for LED products. At the same time, it should also test the performance of LED’s thermal characteristics, environmental tolerance, electromagnetic compatibility resistance, etc., to comprehensively analyze the life of LED.

1. LED reliability and life -related key indicators
Each component and link in LED product manufacturing will affect its reliability and life. For example, the virtual welding of LED knots and substrates, the heat ingening and degradation of LED fluorescent powder, the degradation of packaging materials, and the failure of the drive, etc., etc. The final degradation may be the semiconductor (PN knot) itself. These factors lead to different ways of LED products failure (degradation), and can generally be divided into Gradual Degradation and Abrupt Degradation.

LED’s slowdown (failure) indicator mainly includes:
The lingering maintenance rate decreases, that is, the light decline, which is generally 100%at the initial light flux. When the luminous maintenance rate of LED products drops to 70%or 50%of the initial value, it is considered that the LED fails and the life expectancy of the lumens is L50 or L70;

Color drifting, changes in fluorescent powder or packaging materials, the color of the LED backlight will drift during life. Electrical performance changes, electrical changes can be monitored more intuitive;

The number of switches, the switch may have a certain impact on the driver and other circuits;
The change in thermal resistance and other thermal parameter curves, the heat special is closely related to life, and the measurement and analysis of thermal characteristics helps to find the weak link of LED reliability;

The transient degradation (failure) of LED, that is, the light output of LED suddenly drops to 0, its main degeneration includes: anticroxyomyatoma interference capacity: static discharge, lightning waves, fast group pulses, weekend falling; high and low temperature impact tolerance characteristics; Salt, dampness, vibration, etc.

2. Related standard requirements
In response to the main degeneration of LEDs, relevant standards have been released internationally internationally. Therefore, the North American System and the International Lighting Commission (IEC) system are the most typical. my country’s standards have basically integrated these two systems.

3. The requirements of the North American system and IEC system for LED life and life test methods
The North American system and the IEC system are different in terms of the life requirements and test methods of LED products, but for the evaluation of LED lamps’ life, both propose to direct aging test lamps, or based on an aging test of encapsulation LED, LED modules, etc. Make calculation.

3.1 North American system
As shown in Table 1,
Table 1: The requirements of the United States “Energy Star (Energy Star)” for LED lamp life.

Test Method	Test Sample	Test Sample
Test Object	LED Light Source	LED lamp（Complete Set）
Life/luminous maintenance rate	Home indoor: L70 (6K) ≥25000 hours L70（6K）≥35000 hour	6000H Optical Maintenance Rate Indoor lamps ≥91.8% Outdoor lamps ≥94.1% Commercial lamps ≥94.1%
Standard	LM-80-08， TM-21-11	LM-79-08
Sample Quantity	At least 20 LED packaging, or 10 LED modules in each TS and driver current (refer to TM-21)	3 complete lamps
Aging temperature	High temperature (adapt to the actual temperature in the lamp)	Environmental temperature

Energy Star divides the test method of LED lamps to the life of LED lamps into option 1 and option

1. Among them, option 1 is to test the life of the lamp by testing the light source; and option 2 is only applicable to integrated lamps that are inseparable from light sources and lamps, and directly test the lamps of the lamps. Overnight maintenance rate. Option 1, L70 (6K) indicates that the time of lumites that use 6000H (6K) aging tests to maintain life L70.

The requirements of the two standards of LM-80 and TM-21 are summarized as follows:
Scope of application: LED package, module, array, etc.
Examination object: only examine the life of the light pass, that is, the faulty factor
Aging temperature: Specifying the shell temperature (TS) is 55 ° C, 85 ° C and the third specified temperature, and the TS temperature of the LED light source in the three temperature covering lamps.
Aging time: 6000H, recommended 10000h;
The number of samples and the relationship between its exterior life time: more than 20 samples, the maximum life expectancy is 6 times the aging time; 10-19, the highest life expectancy is 5.5 times the aging time;
Test time for light color parameters: measuring at least once 1000H;
Treatment of sudden failure: observation records, investigation confirmation suddenly fails because of the light source itself;
Record color decay: Yes;
Data records: Each LED’s optical maintenance, intermediate value, standard deviation, minimum and maximum light -pass maintenance rate value;
Curve fitting: 1. The initial value is 1, a normalized light -pass maintenance rate;

2. At each measurement point, find the average value of the return of the sample;
3. Data requirements: Do not adopt measurement data of less than 1000H; aging 6000H-10000h, at least 5000H data; greater than 10000h, with the last 50%data.
Extreme calculation: Recommended index model.

3.2 IEC system
In the IEC system, LX FY is used to characterize the life of LED products. Among them, LX represents the maintenance rate of light flux, such as L70; FY represents failure efficiency, including slow -changing efficiency by and transient loss efficiency CY. For example: L70F50 is 30000h refers to: 50%module is less than 70%after 30000h.

For white light LED products for ordinary lighting, IEC does not emphasize the verification of the life expectancy of claiming, but is graded to the luminous maintenance rate of the limited time.

In particular, in the IEC system, the transient failure and slow change of the LED module or lamps are reflected in the final FY indicator. For a set of LED modules, calculate 20 test samples. If it claims F50, at least N-2 modules pass; if claiming F10, all n modules pass the test.

The temperature in the aging test is also particularly worthy of attention. The aging of the LED module should be aging at the specified point of the shell at the TP temperature, which is equivalent to TS in the North American system; and the lamps inspect their performance under the ambient temperature TQ, and ensure that under the claiming TQ MAX, the module temperature TP will not exceed more Essence.

4. Accelerate aging and life test system
For the test of accelerated aging and life, whether the North American system or IEC system is adopted, its hardware measurement device is basically the same, generally mainly including the constant temperature test box, multi -road power supply, and multi -road temperature inspection instrument. At present, it is also very concerned about the development of LED acceleration aging and life testing systems.

Since the light color performance of LED light sources or lamps is measured at room temperature (25 ℃ ± 1 ℃), foreign typical equipment generally needs to be combined with the integral ball spectrometer system. And the measured LED was taken out of the integral sphere system for optical measurement. The operation process is cumbersome. If the test interval is short, the entire aging test is very time -consuming and laborious. When the test interval is longer, it cannot reflect the change of LED light color parameters in time.

With the support of my country’s 863 project project, LISUN has developed a test system that accelerates aging and optical testing through independent innovation, as shown in Figure 1 as the system photo. The system has 90 skills, which can be divided into three temperature zones and aging testing 90 LEDs (30 × 3). The main characteristic of its structure is to set up light signal sampling devices in the constant thermostat, and connect with light color measurement equipment. The optical parameters of the tested LED can be directly in the box without the need to remove the measurement, which can fully automatically realize the aging test and data analysis.

It makes the long and complicated LED aging, life test, and temperature test become very simple and relaxed, and the data is more accurate and reliable. The equipment contains a number of unique patented technologies for distant companies. The entire device is designed with good overall and beautiful. Whether it is a user or an appraiser, whether it is inside or the appearance, it will be convincing.

Using the above-mentioned measurement device, you can also measure the light color of the LED at different ambient temperature (high temperature state) to obtain the LED optical-ambient temperature curve (temperature characteristics test).

LISUN LEDLM-80PL LED Lumen Maintenance and Aging Life Test System is designed according to IES-LM-80 and TM-21, it used to test & record the optical and electrical Maintenance for single LED or LED module, the software is based on Arrhenius model and TM-21 to calculate the LED life. The LEDLM-80PL needs to work with a GDJW/GW Series High Temperature Chamber and and DC12010 DC Power Source. Please click here to view the test report samples of LM-80 and TM-21.

There are many factors that affect LED products and reliability, and related testing is also complicated. The most important of which is the optical maintenance maintenance rate test. Although the requirements of the international standards have not been the same, the basic test methods and device requirements are basically basically basically. same. With the support of the national 863 project, my country has independently developed high -intelligent accelerated aging and life testing systems, enabling my country’s industrial community to perform a simple, high -precision, and low -cost light -out -and -cost maintenance life detection. At the same time Can test the curve of the light color parameter with the changes in the environmental temperature, to meet the latest international standard requirements, that is, the development trend.

Lisun Instruments Limited was found by LISUN GROUP in 2003. LISUN quality system has been strictly certified by ISO9001:2015. As a CIE Membership, LISUN products are designed based on CIE, IEC and other international or national standards. All products passed CE certificate and authenticated by the third party lab.

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