The photoelectric performance is particularly important for LED display wall products. Do you know what photoelectric performance LED display screen products have? Let's learn about the testing standards for the photoelectric performance of LED products together with the editor.
 

1. Electrical characteristics

The electrical characteristic parameters of LED for led screen video wall include forward current, forward voltage, reverse current, and reverse voltage. This test is generally conducted using a voltmeter and ammeter under constant current and constant voltage source power supply. By testing the electrical characteristics of LED, the maximum allowable forward voltage, forward current, and reverse voltage and current can be obtained. In addition, the optimal operating power value of LED can also be obtained.

 

2. Light characteristics

Mainly including luminous flux and luminous efficiency, intensity and intensity distribution characteristics, as well as spectral parameters.

Luminous flux and luminous efficiency: There are usually two methods, namely the integrating sphere method and the variable angle spectrophotometer method. Although the latter produces the most accurate test results, the former is generally used due to its longer duration. When using the integration ball method for testing, the tested LED can be placed at the center of the ball or on the wall of the ball. After measuring the luminous flux, combined with an electrical parameter tester, the luminous efficiency of the LED can be measured, that is, the luminous efficiency.

Light intensity and light intensity distribution characteristics: LED display screens have inconsistent light intensity distribution, so their test results vary with the testing distance and detector aperture size. This allows various LEDs to undergo light intensity testing and evaluation under the same conditions, resulting in more accurate results.

Spectral parameters: mainly including peak emission wavelength, spectral radiation bandwidth, and spectral power distribution. The spectral characteristics of LEDs can be represented by spectral power distribution, and chromaticity parameters can also be obtained through spectral power distribution. The testing of general spectral power distribution needs to be carried out through spectroscopy, which distinguishes the monochromatic light in the mixed light one by one for measurement. Prisms and gratings can be used to achieve spectroscopy.
 

3. Switching characteristics

It refers to the light, electricity, and color change characteristics of LED at the moment of power on and off. Through this test, the working state, material properties, and other changes of LED at the moment of power on and off can be obtained, thereby understanding the loss of LED caused by power on and off.

4. Color characteristics

The main testing methods include chromaticity coordinates, main wavelength, color purity, color temperature, and color rendering. The testing methods include spectrophotometry and integration.

Spectrophotometry: The LED spectral power distribution is measured using a monochromator spectrophotometer, and then the corresponding chromaticity parameters are obtained by integrating the chromaticity weighting function.

Integration method: Using specific color filters combined with photodetectors to directly measure chromaticity parameters.
 

5. Thermal properties

Also referring 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, and junction temperature refers to the PN junction temperature of the LED. There are two methods for testing the junction temperature of LED chips. One is to use an infrared temperature measuring microscope or a micro thermocouple to measure the surface temperature of the LED chip. The other is to use the inverse relationship between the forward bias voltage under a certain current and the junction temperature to determine the junction temperature of the LED.