LED lamp detection: there is error in the test results

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 have quality problems? Tracing back to the source, the lack of LED lighting standards and the construction of the testing system have not been perfected. 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 the operation of the inductive testing, pointed out that the reasons for the quality inspection are mainly concentrated in 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 It is not safe to isolate 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 error of the system. This error is within the allowable range. Each detection system 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.