Test standard for photoelectric performance of the

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Test standard for photoelectric performance of LED products

photoelectric performance is particularly important for LED products. Do you know what photoelectric performance LED products have? Now let's learn about the test standards for the photoelectric performance of LED products

1. Electrical characteristics

led's electrical characteristic parameters include forward current, forward voltage, reverse current and reverse voltage. This test is generally carried out with a voltmeter under the condition of constant current and constant voltage supply. The maximum allowable forward voltage, forward current, reverse voltage and current can be obtained through the atmospheric and aesthetic test of the electrical characteristics of the LED. In addition, the best working electric power value of the LED can also be obtained

2. Light characteristics

mainly include luminous flux and luminous efficiency, light intensity and light intensity distribution characteristics, and spectral parameters

luminous flux and luminous efficiency: there are usually two methods, the integrating sphere method and the variable angle photometer method. Although the test results of the latter are the most accurate, the former is generally used because of its long time-consuming. When testing with the integrating sphere method, D can be placed at the center of the ball or on the wall of the ball, but the sign of paper shortage is not obvious. After measuring the luminous flux, the luminous efficiency of the LED, that is, the luminous efficiency, can be measured with the electric parameter tester

light intensity and light intensity distribution characteristics: because the light intensity distribution of LED is inconsistent, its test results change with the test distance and the size of detector aperture, so that each LED can be tested and evaluated under the same conditions, so the results are more accurate

spectral parameters: mainly including peak emission wavelength, spectral radiation bandwidth, spectral power distribution, etc. The spectral characteristics of LED can be expressed by the spectral power distribution. Through the spectral power distribution, the chromaticity parameters can also be obtained. Generally, the measurement of spectral power distribution needs to be carried out through light splitting. The monochromatic light in the mixed light can be separated one by one for measurement. Prism and grating can be used to realize light splitting

3. Switching characteristics

refers to the light, electricity and color change characteristics of LED at the moment of power on and power off. Through this test, we can get the working state and material properties of LED at the moment of power on and power off, so as to understand the loss of LED at the moment of power on and power off

4. Color characteristics

mainly include chromaticity coordinates, main wavelength, color purity, color temperature and color rendering, etc. the test methods include spectrophotometry and integration

spectrophotometry: the spectral power distribution of LED is measured by monochromator, and then the corresponding chromaticity parameters are obtained by integrating the chromaticity weighting function

integral method: directly measure the chromaticity parameters with specific color filters and photodetectors

5. Thermal characteristics

also refer to thermal resistance and junction temperature. Thermal resistance refers to the ratio of the temperature difference along the heat flow channel to the power dissipated on the channel. Junction temperature refers to the PN junction temperature of LED. There are two methods to measure the junction temperature of LED. One is to measure the surface temperature of LED chip by infrared temperature measurement microscope or micro thermocouple, and the other is to determine the junction temperature of led by determining the inverse relationship between the positive bias voltage and the junction temperature under the current

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