In recent years, with the continuous development of LED technology, high-power semiconductor lighting devices have developed rapidly in recent years, especially the continuous improvement of white light power and light efficiency, LED gradually entered the field of lighting, triggering a new revolution in the field of lighting technology . LEDs are arranged and combined in different ways and optical design to form a variety of LED lighting products, and the research and development of LED lighting products are in full swing in China, and the performance level of LED lighting products is gradually improving. Under the premise of adopting the correct test method, accurately measuring the photoelectric color performance parameters of LED lighting products is the basis for scientific evaluation of product performance, quality status and development trends. In view of the current status of photoelectric color performance detection of LED lighting products, the author combs and accumulates the accumulation of the center in the work of detecting LED products, and combs and summarizes the detection methods of photoelectric color performance of LED lighting products. 1. General evaluation of performance indicators of LED lighting products 1. Classification of LED lighting products At present, LED lighting products can be mainly divided into LED lighting fixtures (for example: LED road fixtures, LED floodlight fixtures, embedded LED fixtures, LED tunnel fixtures, LED decorative fixtures, LED desk lamps) and traditional lighting source replacement LED lamps (for example: Self-ballasted LED lamp, MR16, PAR lamp, straight tube LED fluorescent lamp T8 / T12, etc.). LED lighting fixtures are complete lighting fixtures that include LED-based light-emitting elements and matching drivers, light distribution components, components that secure and protect the light-emitting elements, and connect the appliance to branch circuit components. LED lamps for lighting can be divided into non-integrated LED lamps and integral LED lamps. Non-integral LED lamps include LED arrays (modules) or LED packages (components) and standard lamp caps and other components of photometric, thermal, mechanical and electrical components. The LED lamp needs to be installed in a lamp with a standard lamp base and LED driver. The LED lamp cannot be directly connected to the branch circuit. Monolithic LED lamps consist of an LED array (module) or LED package (component), LED driver, standard lamp head, and other photonic, thermal, mechanical, and electrical components. The LED lamp can be directly installed on a standardized lamp holder, and it can be directly connected to a branch circuit. The biggest difference between LED lamps and LED lighting fixtures is that LED lamps need to be installed in standard lamp holders. 2. The difference between LED lighting fixtures and traditional light source fixtures At present, LED lighting fixtures are different from traditional light source fixtures in many aspects. First of all, the lifespan of traditional light source lamps can be met by replacing damaged light sources and lamp control devices, so the lifespan of traditional light source lamps is generally not evaluated. The LED lighting fixture is an integrated LED light source and lamp housing. At present, the life of LED lighting fixtures is related to many factors such as the life of the LED light source itself, the LED driver, and the environment provided by the lamps to the LED. For different LED lamps, their life can only be determined by evaluating the relevant life characteristics. Secondly, unlike traditional light source lamps, LED lighting fixtures are composed of multiple LED light sources or module illuminants and emit light. There is a color difference between the illuminants in the LED fixtures, and the color space uniformity evaluation needs to be used to evaluate the LED fixtures For the spatial distribution of colors, evaluate the color differences of LED lamps at different viewing angles. Third, the traditional illumination light source can be used for photometric testing alone, and the relative method can be used for photometric measurement. Due to the characteristics of the integration of LED lamps and the extremely sensitive temperature of the LED light source, it is not suitable to separate the LED light source from the lamp and measure separately. The absolute method should be used to photometrically test the entire LED lamp. Fourth, traditional lighting fixtures are evaluated with the efficiency of fixtures, while LED fixtures are evaluated with energy efficiency or light efficiency. 3. General evaluation of performance indicators of LED lighting products The general evaluation contents of the performance indexes of lighting products mainly include: optical characteristics; electrical characteristics, color characteristics, thermal characteristics, life characteristics, reliability, etc. The current evaluation of LED lighting product performance indicators mainly includes the following aspects: (1) Light characteristics mainly include: light intensity distribution, initial output energy efficiency (light efficiency) / luminous flux, light intensity / illuminance; (2) Electrical characteristics mainly include: lamp power, power factor; (3) Color characteristics mainly include: related Color temperature, color rendering index, chromaticity coordinates, chromaticity tolerance, dominant wavelength (monochromatic), color distribution unevenness and color space uniformity; (4) thermal characteristics mainly include thermal resistance and junction temperature; (5) life Features mainly include switching times test, life / accelerated life test, lumen maintenance rate (luminous flux maintenance rate) / light intensity maintenance rate (reflective cup type MR16 or PAR lamp); (6) reliability test. Second, the detection method of photoelectric color performance of LED lighting products Since the current standards on the thermal characteristics, life characteristics and reliability of LED lighting products are under discussion and drafting, this article focuses on the detection methods of photoelectric color performance of LED lighting products. Discussed below are two series of LED lighting fixtures and LED lights. 1. LED lighting product test environment and physical conditions LED lighting products often have optical components, so to store and test in a relatively clean environment, the lens on the product should be clean without fingerprints. The test environment must not have excessive vibration and shock to reduce air convection. Since the performance parameters of LED lighting products are relatively sensitive to temperature, the ambient air temperature and humidity in the test should meet the environmental requirements specified in the corresponding standards. The ambient temperature is 25 ℃ ± 1 ℃ (switch life test is 5 ℃ ± 5 ℃), the maximum relative humidity is 65%, and there is no convection wind. The working posture of the product should be in accordance with the working posture or actual use posture specified by the manufacturer, so as to avoid improper working posture affecting the heat dissipation and thus affecting the photoelectric parameters. LED lighting products need long enough time to reach temperature equilibrium. The general LED lamp needs to be stable for 30 minutes, and the large LED lighting fixture needs more than 2 hours to reach temperature balance. Judgment principle of temperature balance: the change of illuminance within 15 minutes is less than 0.5%, it can be considered that the temperature balance has been reached. 2. Photoelectric color performance test of LED lighting The main parameters of the photoelectric color performance of LED lighting lamps include: total power of the lamp, power factor, light intensity distribution, total output luminous flux of the lamp, output light efficiency, lumen maintenance rate / luminous flux maintenance rate, correlated color temperature, color rendering index, color tolerance Color coordinates, spatial unevenness of chromaticity, etc. (1) Almost all performance parameters can be obtained by one measurement on a distribution photometer equipped with a distribution spectrum radiometer. The distribution spectrum radiometer mainly tests the color characteristics and color space distribution of the lamps, and the distribution photometer mainly tests the parameters such as light distribution and luminous flux. The test principle of the distribution photometer can refer to the standard GB / T 9468-2008 "General requirements for distribution photometric measurement of lamps and lanterns". (2) At present, the light characteristic parameters (light distribution, luminous flux) and color characteristic parameters of many detection agencies are measured data using a distribution photometer and an integrating sphere system, respectively. When using a distribution photometer to test the lamp, the fixture must be installed so that the light center of the LED lamp coincides with the center of the mechanical axis, and at the same time try to keep the lamp in a normal working posture. When testing the color characteristics with an integrating sphere system, the luminaire does not have to be in the center of the integrating sphere. (3) The luminous flux of LED lamps can also be measured with an integrating sphere system. Ideally, the LED lamps are placed on the top of the integrating sphere, and all output light enters the integrating sphere. At the same time, the color parameters of the lamps can be measured. At present, most of the opening positions of the existing integrating spheres are on the side. For this reason, our institute has specially purchased the rotating 2m integrating sphere system of the American Lanfei Company for the light color detection of LED lighting products. The 2p opening of the integrating sphere can be stopped at any position as required, so that the sample to be measured can be measured at any position, which meets the Energy Star LM-79 test requirements. At present, the detection mechanism mainly uses the above two modes (1) and (2) for the photoelectric color performance detection of LED lamps. The biggest disadvantage of measuring with a distributed photometer is that the test time is too long and the test efficiency is too low. 3. Photoelectric color performance test of LED lamp The main parameters of the photoelectric color performance of LED lamps include: lamp power, power factor, luminous flux, output luminous efficiency, luminous flux maintenance rate, correlated color temperature, color rendering index, chromaticity tolerance, color coordinate and beam of reflector cup MR16 or PAR lamp Angle, light intensity and light intensity maintenance rate, etc. (1) The integrating sphere system with auxiliary lights can quickly measure all these photoelectric color performance parameters of LED lights. First place the LED lamp in the center of the integrating sphere, and test once with the lit auxiliary lamp when the LED lamp under test is not lit. Turn off the auxiliary lamp and light the LED lamp under test, and then test again after stabilization to obtain the color characteristic parameters of the lamp under test, and automatically calculate the luminous flux of the LED lamp under test through the software. If there is no auxiliary lamp in the integrating sphere, the LED lamp itself will absorb part of the reflected light, and there will be some errors in the luminous flux value. At the same time, the inner wall of the integrating sphere should also have a high reflectivity: 90% to 98%. At present, most of the integrating sphere systems in detection institutions have no auxiliary lamps, and the reflectivity of the inner wall of the integrating sphere is less than 90%. These integrating sphere systems cannot accurately measure the luminous flux of LED lights. (2) The luminous flux of the LED lamp can also be measured with a distributed photometer. During the test, the γ angle range should be 180 °, and the center of the lamp coincides with the center of the mechanical axis. The disadvantage is that the test time is too long. (3) The beam angle and light intensity of the reflector cup MR16 or PAR lamp can be measured by a small bedroom distribution photometer. When testing, the mechanical axis and the optical axis must be consistent. The disadvantage is that the test posture is abnormal, and the test results need to be corrected. 3. Summary The measurement of the photoelectric color performance parameters of LED lighting products can be measured by a distributed photometer or integrating sphere system, and can also be used together. Which method to choose depends on the amount to be measured (color characteristics, light characteristics), product size and other requirements. In general, the integrating sphere system equipped with auxiliary lights is suitable for measuring the light characteristics and color characteristic parameters of integrated LED lamps and relatively small-sized LED lamps. The advantage of the integrating sphere system test is that the measurement is fast and there is no need for a dark room. The distribution photometer provides light intensity distribution and total luminous flux measurement methods. It can measure relatively large LED lighting products, and of course can also be used to measure small-size LED lighting products. Pay attention to the test environment requirements, air flow may affect the measurement of temperature-sensitive LED lighting products. Use distribution photometer method should pay attention to correct clamping positioning. The high-precision spectral radiometer installed on the distribution photometer can directly measure the spatial distribution of colors without reflecting through the mirror. Compared with an integrating sphere, it takes more time to measure with a distribution photometer. Under the premise of correct test methods, the reasonable selection of detection methods can accurately measure the photoelectric color performance parameters of LED lighting products, and provide data support for scientific evaluation of LED lighting product performance status and development trends.
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