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For more information, please refer to "High - tech LED - Technology and Application" 1 February issue 
LED luminaire inspection: test results have error life test
[Source: "High-tech LED - Technology and Applications" December issue Reporter / He Wei]
The call for a unified standard for LED lighting is a topic that has been discussed in the industry. Although local governments are already developing and testing their own local standards, the standard confusion is also lacking an authoritative testing platform, and the whole industry is in a mess.
The government is in a dilemma, the company shakes its head and sighs, the people look at the flowers in the fog, do not know who is right and who is wrong, who is right and who is wrong, who is good and who is bad.
Due to the lack of uniform standard specifications and testing methods, the wide variety of LED application products on the market today have different performances and uneven quality, which brings severe challenges to the development of the entire industry.
From the perspective of the current LED product structure and technology development, the evaluation criteria for the quality of LED products for lighting mainly consider optical parameters, electrical properties, thermal properties, radiation safety and life parameters, among which the optical properties of LEDs mainly involve Luminous flux, radiant flux, luminous efficiency, chromaticity coordinates, correlated color temperature, color rendering index, etc. At present, photoelectric detection, light distribution detection, light energy detection, attenuation test and collision resistance test are routine inspection items for LED lamps.
The results of the random inspection are not optimistic
Recently, the Guangdong Provincial Bureau of Quality Supervision released the results of provincial-level special supervision and inspection of the quality of LED light products in Guangdong Province. The sampling results showed that in the batch of 23 batches of self-ballasted LEDs, 17 batches were rejected, and the failure rate was as high as 73.9%. It is understood that the unqualified project involves accidental contact with the protection of live parts, insulation resistance and dielectric strength after wet treatment, mechanical strength, fault condition, color tolerance, general color rendering index, disturbance voltage, lamp power, heat resistance Sex, interchangeability, power factor, initial efficacy / luminous flux, fire and flame protection.
The news about the failure of LED lighting products testing has appeared many times in the near future. Why do LEDs frequently have quality problems? It is the key to the lack of LED lighting standards and the lack of perfection of the detection system. From power supply to finished products, LED lighting has not yet had a set of national or industry standard systems, and there is no requirement for mandatory testing and certification.
“Although the lamps are routinely tested before they leave the factory, not all companies will strictly follow the regulations. This has the factors that do not have the complete conditions for testing equipment, but also the consideration of cost reduction.†The relevant person in charge of Shang Optoelectronics Co., Ltd. pointed out that at present, large enterprises have nationally recognized laboratories in the field of lighting detection, and the testing equipment is relatively perfect. SMEs often only pass the test for a few hours, and the testing equipment is lacking. This caused a large number of unqualified quality problems in some previous government agencies during the sampling inspection of LED lamps, which had a great negative impact on the market penetration of LED products.
Generally, in the detection results of LED lamps, problems such as lack of light flux and display index, color temperature and power deviation are common. Li Sheng, director of operations for inductive testing, pointed out that the reasons for the quality inspection are mainly concentrated in the following four aspects: First, the electrical insulation requirements can not be met, mainly in the internal electrical clearance and creepage distance of the product, the human body can touch The conductor is not safely isolated from low voltage. In particular, some small-sized lamps, due to their compact structure, often neglect the requirements of electrical insulation distance. Second, the driver used does not meet the corresponding LED driver safety requirements, or use a simple step-down circuit to drive the LED. Third, the product electromagnetic disturbance voltage exceeds the standard, most LEDs use cheap drive circuit, no electromagnetic disturbance suppression measures are taken in the circuit, resulting in excessive conduction voltage and radiation. Fourth, can not meet the light color performance requirements of the lamp, the principle of LED lamp illumination and the traditional light source have a big difference, the designer only cares about whether the lamp is illuminated, neglecting the requirements of luminosity and chroma quality, resulting in large deviation of color temperature of the lamp The color rendering index is low.
"The color rendering index can not be lower than 80 according to the requirements, otherwise the initial light effect can not meet the energy efficiency requirements, and can not achieve the effect of energy saving." A test industry insider said that some products currently unilaterally pursue high light efficiency, ignoring lumen maintenance. The service life causes the actual service life of the lamp to be low, resulting in the product not meeting the energy saving index.
There is an error in the test results
In the process of luminaire detection, there is often a problem that the results of the two test parameters of the same luminaire before and after the enterprise are inconsistent. In this regard, Zhu Jungao, technical support manager of Zhejiang University Tricolor Instrument Co., Ltd. said that the reasons for the above errors are mainly in the following three aspects: The first is the system error, which is within the allowable range, each set of detection system It may be inconsistent and there is a certain error. The error of traditional lamps is only qualified within 1.5%, but the standard of LED lamps has not been standardized. The allowable error range of LED lamps in the industry is also vague, generally between 3% and 5%.
The second is the environmental error. The environment in which the luminaire is located and the contamination of the surface will have a great impact on the test results. The error level can reach 7%-8%, especially with some illuminating surfaces and secondary optical lens surfaces. The product. Since these products have a concave-convex structure, they are easy to be contaminated and are not easy to clean, thereby seriously affecting the luminous flux and further affecting the light distribution.
The third is the error between the equipment and the standard. The equipment used for conventional luminaire detection mainly includes the integrating sphere, the distribution photometer and the optical radiation detecting equipment. These devices are used to measure the luminous flux, light distribution performance and photobiosafety of the luminaire. Among them, the optical radiation detection is for the ultraviolet content detection of the export EU and the blue and infrared energy detection required by the US Energy Star. Due to the lack of standards and testing specifications at the national level, the testing methods, testing equipment and testing standards used by testing centers vary from one test to another, resulting in different test results for the same product in different testing organizations. .
Specifically, the luminous sphere is tested for luminous flux. Although the method is relatively simple, only the light intensity meter or the spectrometer can be used with the integrating sphere to complete the test, and no other parameters need to be measured. However, Li Sheng emphasized that due to factors such as the inner ball screen, seams, ball wall opening and spraying effect of the integrating sphere, the accuracy of the integrating sphere is affected, so the technical requirements for the integrating sphere manufacturer are also raised.
“The integrating sphere is a set of precision measuring equipment. It is necessary to purchase a brand with quality assurance. Otherwise, it seems that the integrating sphere seems to be the same, but the result of the measurement will be greatly deviated from the true value, and the stability is poor.†Li Sheng said. At the same time, the integrating sphere test also has certain requirements for the environment, usually requiring an ambient temperature of 25 ± 1 °C. The size of the integrating sphere is not too strict, only related to the size of the lamp under test. In general, the total surface area of ​​the product under test must be less than 2% of the total area of ​​the inner wall of the sphere, and the longest physical dimension of the linear product must be less than 2/3 of the diameter of the sphere. For example, for an LED tube, the longest dimension that an integrating sphere can test does not exceed 2/3 of the diameter of the sphere. These are all issues that manufacturers need to pay attention to when testing.
Life test is as deep as
The long life characteristics of LEDs have always been the gimmick of various companies. However, many luminaires often end up dead without reaching the advertised lifespan. Whether there is a test basis for the 50,000-hour profit life is also the focus of consumers' current questioning.
Li Sheng said that LED does not have a strict life test standard. At present, the standard that everyone generally follows is a test method for assessing lumen maintenance proposed by the US IES, which is the LM-80 of the US Energy Star. This standard is the first test method of comparative system proposed in the industry. Considering the influence of temperature, current and time on LED, it is currently adopted by various certification bodies in the world.
It is understood that the LM-80 lumen maintenance test method is to allow 25 samples to work for 6000 hours at a rated current of 55 ° C, 85 ° C and the third temperature specified by the manufacturer, and then test the total luminous flux, with 6000 hours. Compared with the total luminous flux before the test, if the percentage of the initial luminous flux is greater than 91.8%, the L70 of the LED can be considered to be 25000 hours; if it is greater than 95.8%, the L70 of the LED can be considered to be 50,000 hours. Of course, the standard recommended test is 8000 hours or more.
"How many hours the manufacturer has announced the life expectancy is actually calculated. The 6,000-hour test time mentioned above is the shortest time requirement, because there are too many factors affecting the maintenance of LED lumens, so it is impossible to use faster test. The method is to judge the lumen maintenance rate of the LED." Li Sheng said frankly.
Zhu Jungao also confirmed this statement. He said that for the real life of LED lamps, companies in the industry are more taboo, but they have a common calculation value, and there is no standard. At present, the domestic LM-80 testing equipment is used for rough evaluation. This evaluation is unfounded. "The test of the luminaire is not as strict as the lamp bead. What to do, what conditions to add, there will be a lot of data for reference and explanation after the evaluation." He pointed out that for the street lamp can reach 50,000 hours of life, strictly speaking, there is no Based on. Because the streetlight detection faces more uncertain factors, involving the heat dissipation of the particles, the quality of the test equipment, the stability of the current and voltage, and the compatibility of the device.
For the LM-80 lumen maintenance test, many manufacturers said that 6000 hours of test time can not afford. Therefore, some manufacturers generally adopt the previous semiconductor test method, using the voltage and temperature method to do the rapid aging test to evaluate the LED life. In this regard, Li Sheng believes that this can be used to judge the reliability of LED, but can not calculate the lumen maintenance rate of LED. "Because in addition to the chip, phosphors, silica gel, stents and packaging processes all affect lumen maintenance, it is not possible to simply transfer the experience of previous ICs to LEDs, because LEDs are much more complex than ICs."
Evaluation criteria need to be standardized
At present, developed countries attach great importance to the research of LED test methods and standards. For example, the National Institute of Standards Testing organizes internationally renowned test experts to conduct LED test research, focusing on test methods such as LED luminescence characteristics, temperature characteristics and light fading characteristics, and attempts to establish a complete set of LED test methods and technical standards.
In order to seize the commanding heights of LED research, developed countries have invested a lot of manpower and resources in LED standards and testing. In China, LED test methods currently have no clear national standards, so they are often produced between different manufacturers and users. dispute.
As far as testing standards are concerned, at present, our government and enterprises are competing to formulate some standards. For example, Guangdong Province, Jiangxi Province, Shandong Province, Jiangsu Province, Sichuan Province and Shenzhen City have their own standards.
Guangdong LED street light standards stipulate some detailed testing methods, but it also attracted a lot of controversy, such as 2000 hours or 5000 hours? Since LED street lights are new things, many of the content is in the process of exploration, so there is a dispute that is inevitable.
"Most of the domestic standards are imported from abroad, and the pace of standard setting is five years slower than the international one." Li Sheng said that there is no uniform performance standard for LED lamps, and the standard for traditional lamps is still used in safety standards. To demand LEDs, the industry urgently needs to establish a unified standard for LED performance.
Li Yang, director of sunshine lighting technology, pointed out that the current LED development has the drawbacks of testing equipment, testing methods and standard setting work that cannot meet the requirements of rapid industrial development. The standard and testing system of LED products needs to be improved.
In the process of setting standards, Li Yang emphasized that since the most important point of the standard is that everyone can abide by it, there are two issues to be considered when formulating: First, how much credibility of local standards, whether it can be used in a wide range, How long does it apply? Second, the timeliness of the standard is introduced. Because LED is an emerging technology that is in the process of development and change, the technological route changes rapidly and the product performance improves rapidly, which makes the pace of some product standards unable to keep up with the development of product performance. Therefore, the formulation of basic standards such as reliability test methods needs to be more In-depth research, the development of standards also requires a longer cycle.
The call for a unified standard for LED lighting is a topic that has been discussed in the industry. Although local governments are already developing and testing their own local standards, the standard confusion is also lacking an authoritative testing platform, and the whole industry is in a mess.
The government is in a dilemma, the company shakes its head and sighs, the people look at the flowers in the fog, do not know who is right and who is wrong, who is right and who is wrong, who is good and who is bad.
Due to the lack of uniform standard specifications and testing methods, the wide variety of LED application products on the market today have different performances and uneven quality, which brings severe challenges to the development of the entire industry.
From the perspective of the current LED product structure and technology development, the evaluation criteria for the quality of LED products for lighting mainly consider optical parameters, electrical properties, thermal properties, radiation safety and life parameters, among which the optical properties of LEDs mainly involve Luminous flux, radiant flux, luminous efficiency, chromaticity coordinates, correlated color temperature, color rendering index, etc. At present, photoelectric detection, light distribution detection, light energy detection, attenuation test and collision resistance test are routine inspection items for LED lamps.
The results of the random inspection are not optimistic
Recently, the Guangdong Provincial Bureau of Quality Supervision released the results of provincial-level special supervision and inspection of the quality of LED light products in Guangdong Province. The sampling results showed that in the batch of 23 batches of self-ballasted LEDs, 17 batches were rejected, and the failure rate was as high as 73.9%. It is understood that the unqualified project involves accidental contact with the protection of live parts, insulation resistance and dielectric strength after wet treatment, mechanical strength, fault condition, color tolerance, general color rendering index, disturbance voltage, lamp power, heat resistance Sex, interchangeability, power factor, initial efficacy / luminous flux, fire and flame protection.
The news about the failure of LED lighting products testing has appeared many times in the near future. Why do LEDs frequently have quality problems? It is the key to the lack of LED lighting standards and the lack of perfection of the detection system. From power supply to finished products, LED lighting has not yet had a set of national or industry standard systems, and there is no requirement for mandatory testing and certification.
“Although the lamps are routinely tested before they leave the factory, not all companies will strictly follow the regulations. This has the factors that do not have the complete conditions for testing equipment, but also the consideration of cost reduction.†The relevant person in charge of Shang Optoelectronics Co., Ltd. pointed out that at present, large enterprises have nationally recognized laboratories in the field of lighting detection, and the testing equipment is relatively perfect. SMEs often only pass the test for a few hours, and the testing equipment is lacking. This caused a large number of unqualified quality problems in some previous government agencies during the sampling inspection of LED lamps, which had a great negative impact on the market penetration of LED products.
Generally, in the detection results of LED lamps, problems such as lack of light flux and display index, color temperature and power deviation are common. Li Sheng, director of operations for inductive testing, pointed out that the reasons for the quality inspection are mainly concentrated in the following four aspects: First, the electrical insulation requirements can not be met, mainly in the internal electrical clearance and creepage distance of the product, the human body can touch The conductor is not safely isolated from low voltage. In particular, some small-sized lamps, due to their compact structure, often neglect the requirements of electrical insulation distance. Second, the driver used does not meet the corresponding LED driver safety requirements, or use a simple step-down circuit to drive the LED. Third, the product electromagnetic disturbance voltage exceeds the standard, most LEDs use cheap drive circuit, no electromagnetic disturbance suppression measures are taken in the circuit, resulting in excessive conduction voltage and radiation. Fourth, can not meet the light color performance requirements of the lamp, the principle of LED lamp illumination and the traditional light source have a big difference, the designer only cares about whether the lamp is illuminated, neglecting the requirements of luminosity and chroma quality, resulting in large deviation of color temperature of the lamp The color rendering index is low.
"The color rendering index can not be lower than 80 according to the requirements, otherwise the initial light effect can not meet the energy efficiency requirements, and can not achieve the effect of energy saving." A test industry insider said that some products currently unilaterally pursue high light efficiency, ignoring lumen maintenance. The service life causes the actual service life of the lamp to be low, resulting in the product not meeting the energy saving index.
There is an error in the test results
In the process of luminaire detection, there is often a problem that the results of the two test parameters of the same luminaire before and after the enterprise are inconsistent. In this regard, Zhu Jungao, technical support manager of Zhejiang University Tricolor Instrument Co., Ltd. said that the reasons for the above errors are mainly in the following three aspects: The first is the system error, which is within the allowable range, each set of detection system It may be inconsistent and there is a certain error. The error of traditional lamps is only qualified within 1.5%, but the standard of LED lamps has not been standardized. The allowable error range of LED lamps in the industry is also vague, generally between 3% and 5%.
The second is the environmental error. The environment in which the luminaire is located and the contamination of the surface will have a great impact on the test results. The error level can reach 7%-8%, especially with some illuminating surfaces and secondary optical lens surfaces. The product. Since these products have a concave-convex structure, they are easy to be contaminated and are not easy to clean, thereby seriously affecting the luminous flux and further affecting the light distribution.
The third is the error between the equipment and the standard. The equipment used for conventional luminaire detection mainly includes the integrating sphere, the distribution photometer and the optical radiation detecting equipment. These devices are used to measure the luminous flux, light distribution performance and photobiosafety of the luminaire. Among them, the optical radiation detection is for the ultraviolet content detection of the export EU and the blue and infrared energy detection required by the US Energy Star. Due to the lack of standards and testing specifications at the national level, the testing methods, testing equipment and testing standards used by testing centers vary from one test to another, resulting in different test results for the same product in different testing organizations. .
Specifically, the luminous sphere is tested for luminous flux. Although the method is relatively simple, only the light intensity meter or the spectrometer can be used with the integrating sphere to complete the test, and no other parameters need to be measured. However, Li Sheng emphasized that due to factors such as the inner ball screen, seams, ball wall opening and spraying effect of the integrating sphere, the accuracy of the integrating sphere is affected, so the technical requirements for the integrating sphere manufacturer are also raised.
“The integrating sphere is a set of precision measuring equipment. It is necessary to purchase a brand with quality assurance. Otherwise, it seems that the integrating sphere seems to be the same, but the result of the measurement will be greatly deviated from the true value, and the stability is poor.†Li Sheng said. At the same time, the integrating sphere test also has certain requirements for the environment, usually requiring an ambient temperature of 25 ± 1 °C. The size of the integrating sphere is not too strict, only related to the size of the lamp under test. In general, the total surface area of ​​the product under test must be less than 2% of the total area of ​​the inner wall of the sphere, and the longest physical dimension of the linear product must be less than 2/3 of the diameter of the sphere. For example, for an LED tube, the longest dimension that an integrating sphere can test does not exceed 2/3 of the diameter of the sphere. These are all issues that manufacturers need to pay attention to when testing.