标签：led test

led test and aging test

If the consumers to describe the perfect light source characteristics, then you might hear in their description requires the lowest energy light output and color adjustable, long time to use a variety of desirable characteristics. Minimum input energy is efficiently input power is converted to lumen output, called efficacy; adjustment related to the dimming of light output with less light brightness, or may be regulated to increase the color of the lighting equipment, so as to simulate daytime relative to the status of the night; and by adjusting the bias current flowing through the LED light led test output can be maintained in a longer service life during.

led test and aging test

Incandescent lamps with energy efficiency is low and the service life is shorter; sodium lamps provide color choices are few and short life; less fluorescent lamps dimmable choice selection, service life is short. High brightness LED lights, which claims to have a good energy efficiency, long service life, easy to choose the color and dimming control and no ultraviolet (UV) rays. Thanks to intelligent control device design or LED driver electronics, the advantages of these claims have now been realized. Intelligent LED driver can be adjusted for brightness decay in use during the period, provides the driving characteristics to adjust the color and alternative sorting (binning) to obtain the desired color and brightness of the LED: the by using spectral tuning for different LED system led test  to get the The desired color and brightness.

The spectral tuning mixing several kinds of LED spectral energy distribution, such as the appropriate mix of red, green, and blue LED can produce white light. This RGB combination is also used to generate almost all colors of light. If the LED drive is not designed for adjusting a set of different LEDs, the designer must select from the separation of the LED in order to produce a specific color. Sorting manufacturers based on light-emitting lumens and color LED classification process, the example of Figure 1 shows a group of industry-standard LED classification criteria.

Sort by plotting rectangular area on the chromaticity diagram. A group containing the LED of the same class will be similar in color and brightness characteristics. However, in a large office or factory led test environment contains many lighting equipment, different classes may still result in uneven light color in a group of large-scale lighting equipment is obvious. Separation of LED design does not provide the method of changing the illumination device color; use the feedback to the tuning system and a set of different colors of LED spectral characteristics of the different LED compensating illumination system, it can be established in an office environment, so that the entire space uniform light. Spectral tuning can also compensate for other effects, such as the edge of the room window outward natural light or reflected into the room corridor lighting.

LED test: errors frequently happened

Usually, in LED test, luminous flux, CRI, color temperature and power deviation are four major aspects that with relatively high failure rates. Unqualified quality testing results mainly concentrate in four aspects: 1. Electrical insulation cannot meet the corresponding requirements: insufficient internal clearance and creepage distance, with touchable conductors (not safely isolated). Especially for some small sized LED lamps, the compact structure forced manufacturers to ignore the requirements of electrical insulation. 2. Using drivers that cannot meet the safety requirements of LED power supplies, or using simple buck circuit to drive LED lamps. 3. Electromagnetic disturbance voltage exceeds standards: most of LED drivers use cheap but weak circuits without any anti-electromagnetic measures, leading to conduction voltage and radiation exceeding. 4. Cannot meet the light and color performance requirements. LED light-emitting principles have huge differences with traditional lighting technologies. Many designers only concerned about whether their products can send out light normally, but ignore the quality of photometric and colorimetric requirements, resulting in the huge differences in color temperature deviation and low CRI.

 

Usually, in LED test, luminous flux, CRI, color temperature and power deviation are four major aspects that with relatively high failure rates.

 

In LED test, lamps from one manufacturer may get different testing results in different testing processes. There are three main reasons that cause to such situation:

 

1)       Testing system errors. This error is within the allowable range. Due to production process deviations, it is very hard for different testing system to stay exactly the same. There must be some errors. Traditional light fitting with error less than 1.5% are qualified. However, tests for LED lighting products have not been standardized. The permissible error range of LED lighting products is relatively vague, generally between 3% and 5%.

 

2)       Error comes from different testing environment. Lamps’ working environment along with the different surface contamination will exert huge influence on testing results, 7%-8% error. Especially for some products which used light-emitting surfaces as the secondary optical lens. These products have concave and convex structures. Dust and dirt can easily accumulate on the surface, hardly to clean up, which seriously affect the luminous flux and furthermore the light distribution.

 

3)       Errors come from equipment deviations and standard errors. Normal LED test includes: spherical integral devices, devices for light distribution measurement and equipments for light radiation. Spherical integral devices are used to measure the luminous flux of LED lights.

LED test: sampling test results are not optimistic

From the current LED product structure and developing direction, the main testing standards for LED-related lighting products are focus on optical performance, electrical performance, terminal conductivity, radiation safety and service life. Optical performance is mainly related to the luminous flux, radiant flux, luminous efficiency, chromaticity coordinates, correlated color temperature (CCT), color rendering index (CRI). Photoelectric detection, light distribution detection, light energy detection, attenuation and anti-vibration test are five major normal testing for G24 LED lighting products.

 

From the current LED product structure and developing direction, the main testing standards for LED-related lighting products are focus on optical performance, electrical performance, terminal conductivity, radiation safety and service life.

 

However, according to a recent sampling LED test report, results are not satisfied. Recently, the Guangdong Provincial Bureau of Quality Supervision issued a product quality supervision and inspection testing report for self-ballasted LED lighting products. The final results showed that among 23 self-ballasted LED lamps, 17 are unqualified. The failure rate is as high as 73.9%. Failure items include accidental contact with live parts, the wet processing insulation resistance and dielectric strength, mechanical strength, fault status, chromatically tolerances, general CRI, harassment voltage, lamp power, heat resistance, interchangeability, power factor, the initial light efficiency / luminous flux, anti-blame capability and so on.

 

Awful LED test results happened frequently in recent years. Tracing the source, lacking of standards and immature testing systems mainly contribute to the high failure rate of LED sampling tests.

 

Although routine performance tests need to be taken before products leaving factories, not all manufacturers will follow testing standards strictly. On one hand, the majority of LED manufacturers do not have complete testing equipments. On the other hand, they need to take cost into account. Current large LED enterprises have nationally recognized LED test laboratories and relatively complete testing equipments. SMEs usually conduct several small simple LED tests (maybe a few hours), also lacking of necessary testing equipments. These phenomena led to the high failure testing rate mentioned previously and consequently a great deal of negative impact in the LED lighting market.

 

CRI should be greater than 80, otherwise the initial luminous efficiency cannot meet the requirements of energy efficiency to reach the energy-saving effect. Currently, some LED suppliers blindly pursue high luminous efficiency but ignore the light attenuation and total lifetime of their products, leading to the low service life of LED lighting products and the high failure rate.