How to use the experimental data to effectively estimate the LED life?

The Environmental Protection Agency (EPA) and the Department of Energy (DOE) have released Energy Star® and Lighting Facts standards for LED light source lamps/light bulbs since 2010. The specifications of LED lighting products have been followed. At present, the international LED manufacturers are relying on the life evaluation and product specifications of LED products. In other words, if LED manufacturers want to enter the international LED lighting market, they are bound to obtain the LED Energy Star certification.

In the ENERGY STAR section, on July 6th, 2011 (2011), the EPA integrated the two large-scale luminaire specifications for residential lighting (RLF) and solid-state lighting (SSL Luminaires) into [ENERGY STAR] in order to simplify the qualification review program. ® Luminaires Program Requirement V1.1], which was officially launched on April 1 this year (2012), and the bulbs are also integrated into [ENERGY STAR® Program Requirements for Integral LED Lamps V1.4], two specifications. In addition to the increase in the number of audited data items, the requirements for [LM-82 Photoelectric Characteristics Specification] and [TM-21 Life Prediction Specification] have been included in the discussion.

The LM-82 is currently not officially published in the North American Lighting Association (IESNA). Its content is mainly for the verification of the electrical and optical properties of LED Light Engines and Integrated LED Lamps at different temperatures. The measurement method is similar to LM-79. -08 plan, but the focus is on the characteristic impact assessment of temperature versus electrical/optical parameters.

The other part is TM-21-11 (Projecting Long Term Lumen Maintenance of LED Light Sources) published by IESNA on July 25, 2011. This specification mainly predicts the performance and life of LED light sources, and is announced with the date. The LM-80-08 LED lumen maintenance test was performed using the experimental data of LM-80-08 to estimate the long-term performance of LED components and lamps/bulbs.

First, use TM-21 to estimate the life steps of LED lamps

In order to give the LED industry a clearer concept of TM-21 and understand how to make good use of TM-21 to estimate LED products, the author will explain the application and estimation of LM-80-08 and TM-21-11 in four procedures. the way:

Step 1: The LED component supplier performs an LM-80-08 experiment on its LED Source (Package/Array/Module) for 3 temperatures (55 ° C / 85 ° C / self-selected temperature) for at least 6,000 hours.

Number of samples required: (related to the estimable time)

Test time requirements: (connected with estimation accuracy)

At least 6,000 hours, recommended for 10,000 hours, the LED light attenuation data required to be tested every 1,000 hours, the shorter the interval (for example: 500 hours) can improve the accuracy of the estimation.

Step 2: Estimate the long-term life data of the three test temperatures (55 ° C / 85 ° C / optional temperature) according to the TM-21-11 formula.

Obtain the average value of each temperature experiment data, and the test data take-out time rule is:

The slope m (Slope) and the intercept b (Intercept) are obtained by Exponential Least Squares Curve-Fit. When m and b are calculated, the longer the test time is, the more dense the interval is, the higher the accuracy will be, and then the calculation will be performed. B and alpha values ​​are derived.

y=mx+b, B=exp(b), a=-m

The life time value of the LED of each temperature experiment at 70% of the lumen maintenance rate specified by ENERGY STAR was calculated according to the following formula.

L70 : Time of use when the LED lumen maintenance rate is 70%

The standard judgment of the multiple of the time can be estimated by the number of samples in the first step:

Expressed as: L70(6K) = XX, XXX hours

(6K) : LM-80 test time, (6K) = 6,000 hours; (10K) = 10,000 hours

XX, XXX Hours : Sample ≧20ea, test time = 6,000, can be estimated 6 times for 36,000 hours

Using the Exponential formula to calculate the lumen maintenance rate for each time, the calculated data can be calculated to plot the estimated life of each test temperature:

Step 3: Obtain the In Situ Temperature of the LED component placed on the LED lamp.

Please refer to the ISTMT (In Situ Temperature Measurement Test) test program to obtain the temperature of the LED component placed in the LED luminaire. The test temperature position must be the same as the Ts setting position of the LM-80-08. The temperature data taken out is called TMPLED (LED). Temperature Measurement Point).

Step 4: Interpolate the calculated results of the measured TMPLED and TM-21 calculations to obtain the estimated lifetime value of the TMPLED.

The two nearest temperature points of the TMPLED are selected from the three test temperature points as the calculation reference point.

Calculate the Arrhenius Model temperature acceleration parameter A and obtain Decay Rate: α and the setting parameter B0.

The L70 value of the TMPLED is calculated by the above formula, and the same program represents the result of the TMPLED.

L70(6K) > XX, XXX hours

Nest the relevant time values ​​and plot the lifetime estimation of TMPLED and three Ts.

Second, ENERGY STAR / Lighting Facts for LED lamps / bulb life requirements

ENERGY STAR has only two specifications in the luminaire. The luminaire manufacturer can use the whole lamp to illuminate 6,000Hrs., or submit the component manufacturer's 6,000Hrs LM-80 report and TM-21 estimation results to confirm the lumen maintenance of the finished lamp. Some standards are more flexible, and the standards will be fine-tuned for different purposes, as shown in the following table:

Third, the key to the success of LED lighting is the key to success: LED quality

Lighting products are regarded as the biggest business opportunity for LEDs. However, in the past, LED prices were too high. Although they have the advantages of energy saving and environmental protection, prices are still unable to compete with incandescent and energy-saving bulbs. In addition, a few years ago, due to the lack of relevant quality verification standards, the quality of LEDs was uneven (light fade, color change, etc.), which also led to many negative experience, and also caused the LED lighting usage to be delayed and explosive growth.

However, in 2012, the sweet spot of LED lighting prices has arrived in advance, and it is expected that LED demand will rise sharply in the next two years. When the price of LED products reaches the acceptable price for consumers, LED manufacturers can stand out from the crowd at this moment of demand, and the key to success is the quality and longevity of LEDs.

At present, the US Energy Star has provided quantitative standards for LED quality, which enables the LED industry to follow the specifications. The author will also hold the “LED Energy Star certification process and reliability at Hsinchu Technology and Intertek HK on November 8th. "Verification Technology Seminar", to further share the normative content of ENERGY STAR LEDs, and to provide experience sharing and response measures, and also welcome the industry to come together to communicate.

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