Determination of driving current of RGB LEDs for white light illumination

The relationship between the driving current of RGB LED chips and the color temperature of the produced white light was investigated. A simple method was proposed to estimate the color temperature output from the electric current input. This procedure started from the derivation of expressions of optical flux and chromaticity coordinates of the white light in terms of those of constituent RGB LED chips. A set of concise equations could be obtained. The next step was to correlate the optical flux and chromaticity coordinates of RGB chips to their corresponding driving current. This was achieved through optical characterization of individual LEDs at various levels of driving current and curve fitting. By cascading these two parts, the optical flux and the color temperature of the white light could be predicted with various combinations of driving current input of individual RGB LED chips. In addition to the derivation and analysis, a validation case and several demonstrations are also presented in this paper. The proposed method cannot only save a large amount of time for experimental trial-and-error for the color temperature tuning of white light illumination from RGB color mixing, but also reduce the cost of sample preparation.