A Novel Color Control Method for Multicolor LED Systems to Achieve High Color Rendering Indexes

A novel color control method for multicolor light-emitting-diode (LED) systems is proposed. The proposed control method can achieve high color rendering indexes by approximating the spectral power distributions (SPDs) of black bodies. The SPD control of the LED system is accomplished by combining a sensory module and a control module. The sensory module implements a linear function that merges readouts from multiple color sensors and maps the data into the optical powers of the LED channels, while the control module utilizes such data in a feedback loop to control the optical power of each channel. Compared with conventional control methods, the proposed method has the merits of 1) not requiring an accurate electrical-optical system model, 2) requiring only a few spectra data for offline calibration, 3) requiring only red-green-blue (RGB) color sensors for online operations of tetracolor and pentacolor LED systems, 4) providing consistent color with high color rendering index, and 5) being applicable to all multicolor LED systems. The proposed control method is evaluated by applying it to an example of an RGB-amber LED system driven by a buck-type single-inductor-multiple-output LED driver with the LED channels connected in series. Experimental results have verified the effectiveness and robustness with ambient temperature of the proposed control method.