Shanghai Lican: How to use TM-21 to estimate the life of LED lamps?

LEDs are a very long-lived source of light. Depending on the driving power supply and the conditions of use, LEDs can last up to 5W hours or more, but LEDs do not go out like other light sources, but gradually decay. Therefore, after prolonged use, light decay can result in low light output and the product does not meet the requirements. So how to correctly use the TM-21 to estimate the life of LED lamps?

In order to make the LED industry have a clear concept of TM-21, and understand how to make good use of TM-21 to evaluate LED products , we are committed to the development and after-sales of lighting test instruments, EMI/EMC test systems and safety test instruments in the domestic market. The maintenance of Shanghai Lijun uses four procedures to illustrate the application and estimation of LM-80-08 and TM-21-11:

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 denser 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:


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