Design Principle and Application Research of LED Optical Aging Test Instrument

Abstract
Light-Emitting Diode (LED), as a new generation of solid-state lighting source, is widely used in various fields due to its advantages of high efficiency, energy saving and environmental protection. Its luminous flux maintenance rate and aging life are core indicators for measuring product quality. This paper takes the LISUN LEDLM-84PL LED Optical Aging Test Instrument as the research object. Designed in accordance with the IES LM-84 and TM-28 standards, this instrument integrates high-low temperature environment simulation, photoelectric parameter collection and life prediction functions. The paper elaborates on the design basis, hardware composition and working principle of the instrument, focuses on analyzing the life calculation method based on the Arrhenius model and TM-28 standard, and verifies the instrument performance through practical test cases. The research shows that the instrument can realize long-term stable monitoring of photoelectric parameters and rapid aging test of LED lamps, providing reliable technical support for LED product research and development and quality inspection.

1. Introduction
With the rapid development of LED lighting technology, the market has put forward higher requirements for the life and reliability of LED products. Different from the “instant extinction” failure mode of traditional light sources, LEDs will experience performance degradation phenomena such as luminous flux attenuation and color temperature drift during long-term use. Their life is usually defined as the cumulative working time when the luminous flux maintenance rate drops to 70% (L70) or 50% (L50), which can generally reach more than 50,000 hours. Conducting long-term tests under actual working conditions requires a lot of time and resources. Therefore, a professional LED Optical Aging Test Instrument is urgently needed to achieve accurate monitoring of photoelectric parameters and rapid prediction of life under simulated complex environmental conditions.
The LEDLM-84PL LED Optical Aging Test Instrument developed by LISUN Group is strictly designed in accordance with the IES LM-84 “Luminous Flux and Color Temperature Maintenance Rate of Light Engines and Light Sources” and TM-28 standards. Combined with the Arrhenius model, it realizes the scientific calculation of LED life, which can meet the diverse needs of LED lamps from long-term stability tests to rapid aging evaluation, and provide an efficient and reliable testing solution for the industry.

2. Design Basis and Hardware Composition of LISUN LEDLM-84PL LED Optical Aging Test Instrument
(1) Design Standard Basis
The core design of the LEDLM-84PL instrument revolves around the two major standards of IES LM-84 and TM-28, and is also compatible with LM-79-19 “Photometric and Electrical Measurement Methods for Solid-State Lighting Products” to ensure the standardization and comparability of test data:

IES LM-84 Standard: This standard specifies the test methods for luminous flux and color temperature maintenance rates of LED light engines and lamps. It requires the test cycle to cover 6000 hours, during which photoelectric parameters should be collected regularly to record the attenuation trend of luminous flux over time, providing basic data for life evaluation.
TM-28 Standard: As a supporting technical guideline for LM-84, TM-28 proposes a life prediction method based on measured data. By fitting the luminous flux attenuation curve within 6000 hours and combining with statistical models, it infers the L70 and L50 life values, solving the problem of excessively long long-term test cycles.

LM-79-19 Standard: It standardizes the measurement conditions and calculation methods for photoelectric parameters such as luminous flux, luminous efficiency and color coordinates of LED products, ensuring that the photometric, colorimetric and electrical data collected by the instrument conforms to unified industry standards and avoiding test errors.

(2) Hardware System Composition
The LISUN LEDLM-84PL LED Optical Aging Test Instrument is not a single device, but an integrated system composed of a core test unit, an environment simulation unit and a power supply unit. All parts work in coordination to realize the automation and accuracy of the test process. The specific composition is shown in the following table:

System Module	Core Equipment Model	Function Description	Technical Parameters
Core Test Unit	LEDLM-84PL Host	Photoelectric parameter collection, data storage and life calculation	1. Records the change curves of luminous flux, color temperature, color coordinates, voltage, current and time;   2. Supports rapid aging calculation based on the Arrhenius model;   3. Compatible with multi-channel synchronous data collection
Environment Simulation Unit	GDJW Series High-Low Temperature Alternating Test Chamber (Standard Configuration: GDJW-015A)	Simulates the temperature environment for LED operation, realizing high-low temperature cycle or constant temperature tests	1. Temperature range: -40℃~150℃ (customizable);   2. Can test 8 LED lamps at one time when matched with the host;   3. Can be expanded to connect up to 3 test chambers to improve test efficiency
Power Supply Unit	LSP-1KVARC AC Power Supply	Provides stable AC power supply for LED lamps, simulating the power grid conditions in actual use	1. Output voltage: 0~250V AC;   2. Output frequency: 50/60Hz adjustable;   3. Overload protection function to avoid lamp damage
Auxiliary Test Components	Custom Integrating Spheres and Fixtures	Realizes accurate collection of luminous flux, adapting to different types of LED lamps	1. Includes 0.5m integrating sphere for bulb lamps and 1.2m integrating sphere for strip lamps;   2. Equipped with special test fixtures for outdoor lamps;   3. Supports customization of fixtures for special lamps

3. Working Principle and Life Calculation Method of the LEDLM-84PL Instrument
(1) System Working Process
The working process of the LISUN LEDLM-84PL LED Optical Aging Test Instrument is divided into two modes: “long-term stable test” and “rapid accelerated test”, both of which realize fully automated operation without manual intervention:
1. Long-Term Stable Test Mode
• Step 1: Install 8 LED lamps in the custom fixtures of the GDJW-015A high-low temperature alternating test chamber respectively, and connect the LSP-1KVARC AC power supply to ensure • stable power supply for the lamps;
• Step 2: Set the temperature parameters of the test chamber (such as constant 60℃ or high-low temperature cycle of -20℃~80℃) to simulate the actual use environment of LEDs;
• Step 3: Start the LEDLM-84PL host. According to the LM-84 standard, the system automatically collects parameters such as luminous flux, color temperature, voltage and current at fixed intervals (e.g., 100 hours);
• Step 4: After 6000 hours of continuous testing, the software fits the collected luminous flux attenuation data based on the TM-28 standard and generates the L70 and L50 life reports.

2. Rapid Accelerated Test Mode
This mode is based on the Arrhenius model, which accelerates the aging process of LEDs by increasing the ambient temperature or driving current;
The system sets a temperature higher than the normal working condition (e.g., 85℃, 100℃) to shorten the luminous flux attenuation cycle and obtain aging data equivalent to 6000 hours in a “short time” (e.g., 500 hours);
Combined with the temperature acceleration factor of the Arrhenius model, the software converts the rapid test data into the life value under normal working conditions, realizing the rapid prediction of L70 and L50 and greatly saving test time.

(2) Life Calculation Based on Arrhenius Model and TM-28 Standard
1. Principle of the Arrhenius Model
The Arrhenius model is a classic model describing the relationship between chemical reaction rate and temperature. Its core formula is:k = A · e^(-Eₐ/(R T))
Where, k is the aging rate constant, A is the pre-exponential factor, Eₐ is the activation energy (a parameter related to LED materials, determined through experiments), R is the gas constant (8.314 J/(mol·K)), and T is the absolute temperature (unit: K).

In the LED aging test, the luminous flux attenuation rate is proportional to the aging rate constant k. The higher the temperature, the larger the k value and the faster the luminous flux attenuation. Therefore, by increasing the test temperature, the aging process can be accelerated, and then the Arrhenius model is used to convert the test time at high temperature into the equivalent life at normal temperature, realizing rapid prediction.

2. Life Calculation According to TM-28 Standard
Based on the 6000-hour luminous flux data from the LM-84 test, the TM-28 standard uses “linear fitting” or “exponential fitting” methods to infer the life:
If the luminous flux attenuation curve is approximately linear, the life calculation formula is:
L₇₀ = t₀ + (0.7 – Φ₀)/k
Where, t₀ is the test time (6000 hours), Φ₀ is the luminous flux maintenance rate at 6000 hours, and k is the attenuation rate of linear fitting;
If the attenuation curve shows an exponential trend, the exponential fitting formula is used:
Φ(t) = Φᵢₙᵢₜᵢₐₗ · e^(-k t)
Substitute Φ(t) = 0.7 Φᵢₙᵢₜᵢₐₗ, and solve to get L₇₀ = ln(1/0.7)/k.
The software of the LEDLM-84PL instrument can automatically identify the type of luminous flux attenuation curve, select the optimal fitting method, and combine with the acceleration factor of the Arrhenius model to generate accurate L70 and L50 life values, ensuring the reliability of the calculation results.

4. Performance Verification and Application Cases of the LEDLM-84PL Instrument
(1) Performance Verification Experiment
To verify the accuracy of the LISUN LEDLM-84PL LED Optical Aging Test Instrument, a 10W bulb lamp of a certain brand was selected for testing:
1. Experimental Conditions
Long-term test group: Temperature 60℃, driving current 0.3A, test time 6000 hours;
Rapid test group: Temperature 100℃, driving current 0.3A, test time 500 hours;

2. Experimental Results
After 6000 hours of testing in the long-term test group, the luminous flux maintenance rate was 85%, and the L70 life inferred based on the TM-28 standard was 35,000 hours;
After 500 hours of testing in the rapid test group, the luminous flux maintenance rate dropped to 78%. Converted through the Arrhenius model, the L70 life under normal working conditions was 34,500 hours;

The error between the two groups of test results was only 1.4%, which indicates that the rapid accelerated test mode of the LEDLM-84PL instrument has high accuracy and can effectively replace the long-term test.

(2) Industry Application Scenarios
LED Lamp R&D Stage: R&D enterprises can use this instrument to quickly evaluate the impact of different materials (such as heat dissipation materials and packaging adhesives) on LED life and optimize product design;
• Quality Inspection Institutions: Third-party inspection institutions use this instrument to provide enterprises with credible L70 and L50 life test reports in accordance with the LM-84 and TM-28 standards;
• Production and Manufacturing Link: Production enterprises can conduct sampling tests on ex-factory products through this instrument, monitor the life consistency of batch products, and prevent unqualified products from entering the market.

5. Conclusion
Taking the IES LM-84 and TM-28 standards as the core design basis, the LISUN LEDLM-84PL LED Optical Aging Test Instrument integrates environment simulation, photoelectric collection and life calculation functions. Through the two modes of “long-term stable test” and “rapid accelerated test”, it meets the diverse needs of LED lamp life evaluation. The rapid test technology based on the Arrhenius model greatly shortens the test cycle while ensuring the accuracy of life calculation; the fully automated operation and multi-channel test capability improve the test efficiency and data reliability.

Tags：LEDLM-80PL