Investigation on Tunable Color Temperature and Color Rendering Index of High Brightness White LEDs

The color temperature(Tc) and color rendering index(Ra) were analyzed by experiments and theories after mixing high-brightness white LEDs with different color temperatures.Two white LED samples with low color temperature(2 800~3 000 K and 2 800~3 000 K) and one with high color temperature(7 000~8 000 K) were mixed in series and parallel.The dimming effect and color rendering index were analyzed by changing the forward current.The results show that the tunable range of color temperature of mixed white LEDs is 3 000 K~7 000 K,and when white LEDs with Ra 66 are mixed with LEDs with Ra 87,white light with Ra75 can be obtained in the tunable range of color temperature.