Determining The Junction Temperature Of Two Phosphors-Converted Led Based On Spectral Feature Parameters Of The Chip

The junction temperatures of LED with different ambient temperatures and drive currents were measured with the Forward Voltage method, at the same time, the normalized spectral distributions were measured with spectrometer.The specific spectral distribution of blue chip was selected to calculate its centroid wavelength and full width at half maximum, and then the relationships among these two parameters, drive current and junction temperature were obtained. At last, the junction temperature of the LED at the lighting condition was obtained with the relationships and the measured spectral feature parameters of the chip. It was found that for the junction temperature changed with ambient temperature, the measured error of this method and (B+Y+R)/B method were both about 2 degrees C., and no statistical significance. For the junction temperature changed with drive current, the measured error of this method was always 2 degrees C. However, the error of the (B+Y+R)/B method was positively correlated with the current, with the change rate of 0.048 degrees C/mA. Therefore, the established method was suitable for determining the junction temperature with the change of not only ambient temperature, but drive current, and it was also accurate when LED lighting for a long time without re-calibration, which showed significant technical advantages.