White light solid state lamp with luminance and color temperature control

The paper illustrates the design of a white light solid state lamp, presenting a controlled quality of the emitted luminous flux in terms of both luminance and color temperature. Exploiting the same principle of color mixing adopted in RGB light sources, the designed fixture is based on three LED arrays implementing two primary color emitters (red and green) and a cool white light source. The regulation of intensity and color temperature is achieved by independently adjusting, by PWM dimming, the luminance of each LED array. The compensation of temperature effects is implemented by a feed-forward controller, that only requires sensing the voltage drop of each LED array. The proposed design and digital control strategy is cost effective and guarantees color temperature variations lower than 2% and full control of the lamp luminance.