Research On A Testing Device For Photoelectric Parameters Of RGB-LED

RGB-LED(Red-Green-Blue-LED) is the basic unit of Full Color display,whose research on testing photoelectric parameters has a great influence onimproving the quality of Full Color display. At present, the technology of domestictesting device about RGB-LEDs is not so mature, the accuracy and speed ofdetections can not meet the actual needs of the enterprises, and in recent years thedomestic LED testing devices are in the design of single crystal. There are rarelytesting devices for photoelectric parameters of RGB-LEDs. A testing device wouldbe designed according to the photoelectric parameters of RGB-LEDs, and a testingresearch was carried out on the testing device.The main photoelectric parameters of RGB-LEDs are introduced, and testingmethods of each parameter of RGB-LED are analyzed. According to the features ofhigh-power RGB-LEDs, it focuses on driver power for RGB-LEDs, proposing thatusing three-channel constant current source to drive the RGB-LEDs, discussing howto improve the accuracy of the constant current source and taking Kang copper wireswhose choice of drift coefficient is very low as the sample resistance, such as othermeasures to improve the accuracy of the constant current source, which ensures thestability and accuracy of the drive current source.On the base of understanding the main characteristic parameters of LED, testingdevice for photoelectric parameters of RGB-LEDs is introduced, mainly includesthe design of controlling part，testing part and software. The controlling system isrealized by the technology of combination of MCU and PC. Hardware test system iscontrolled by the MCU, including the program-controlled constant current sourcedriver, the program-controlled voltage source driver, the sampling A/D, the D/Aoutput design, and so on, PC machine is used to control the light, electrical and colortest of RGB-LEDs. Testing part is composed by the spectral instrument and PCmachine connecting with a USB port. Besides, the integrating sphere opticalsampling technology and spectral correction integral photometry testing technologyare introduced. The software system is composed of MCU program and PC program. Finally, the calibrating methods of the device are studied and discussed, theforward voltage of RGB-LEDs is determined, the luminous flux and light intensityare as machine calibrating parameters, and an experiment of the RGB-LED testingdevice was carried out. The results of the experiment show that the detection speedof the testing device is rapid. The test time of a single RGB-LED is60ms; In addition,the repeatability error of photoelectric parameters of RGB-LEDs is small. Forexample, the repeatability error of the luminous flux is±5％. Therefore, the testingdevice meets the requirements of the design and has a good practical performance.The testing device is one of the key equipments of semiconductor lightingindustrialization, which can not be ignored. Its successful development will push theprocess of the Full Color emiconductor industrialization.