Research On Spectral And Chromatic And Junction Temperature Prediction Of High Voltage White LED

LEDs are used in a wide range of applications in lighting,display and communication.In practical LED lighting,accurate prediction of LED junction temperature has been the subject of much research.At the same driving power,the driving current of high-voltage LEDs is lower than that of low-voltage LEDs,which significantly reduces the self-heating effect of the current and helps to extend the life of the device.This paper focuses on the temperature and current characteristics of the spectral and chromatic parameters of 12 V high-voltage and 6V low-voltage LEDs,using the relative chromatic parameters,and the joint prediction of the junction temperature of high-voltage LEDs by the dual parameters.The main research content is as follows with the results:1.Spectral analysis studies of white LEDs with blue chips and white LEDs with the same chip excitation phosphor at constant current/constant current variable temperature.With the junction temperature rising at constant current,the peak of the high-voltage white LED undergoes a linear red shift,the half-peak width is linearly broadened,and the colour coordinates are linearly decayed,etc.;with the driving current rising at constant junction temperature,the peak and central wavelength of the high-voltage white LED undergoes a linear blue shift,the half-peak width is still linearly broadened,the colour temperature is linearly increased,and the colour coordinates are linearly decayed,etc.Under the same driving power,12 V high voltage is more stable due to higher working voltage and less self-heating effect of current,so its light colour characteristics are less affected by junction temperature.2.A method is proposed for predicting LED junction temperature based on relative chromaticity parameters.Colour fidelity index and colour gamut index proposed by the Illuminating Engineering Society of North America are used to predict the junction temperature of 12 V high voltage and 6V low voltage LEDs.The maximum error in the prediction of colour fidelity index for junction temperature is3.33% and the maximum error in the prediction of colour gamut index for junction temperature is 4.24%.3.Two joint methods of half-peak width combined color fidelity and color saturation combined color fidelity are proposed to predict the junction temperature of high-voltage LED.Compared with the results measured by T3 ster,the maximum error is 2.77%,which is 1.47% lower than the maximum error of the relative chromaticity parameter to predict the junction temperature at high pressure.The average difference between the two combined methods and the results measured by T3 ster is less than 2℃,and both meet the requirements of the non-contact spectral method to predict the junction temperature.