The color temperature and CRI of white-ray LED lights are close related to production process of LEDs. It was Nichia that created white-ray LEDs for the first time by using InGaN blue-ray LED chips (yttrium aluminum gamet) with phosphor powders. After that, people also created white-ray LEDs through light mixing of RGB chips.
Blue-ray LEDs plus YAG phosphor is relatively simple than other methods, and cost less. It is the most commonly used method to make white-ray LED lights. But relatively, LEDs produced through this way have very low CRI. Adding some red phosphor powder and green phosphor powder can increase the CRI level, but the lighting efficiency will be declined. Theoretically, ultraviolet LED chips combined with RGB tri-chromatic phosphor powder can generate multiple color temperatures and white-rays with higher CRI. But the problem is the current ultraviolet LED technology is still in an immature stage. Indeed, multi-chips can obtain arbitrary color temperature and white-ray LEDs with high level of CRI theoretically. However, the input voltage and output light of multi-LED chips are different. Besides, the temperature characteristic and the light-keeping characteristic are different, either. Thus, it requires very sophisticated circuit designs. The current immature technologies will lead to the huge variations in color temperatures.
In order to satisfy a certain level of illuminance, LEDs should provide sufficient luminous flux. Take a small reading room for instance, assumed that the area of this reading room is 6m x 8m. Normally, lamp with a luminous flux around 20000lm – 30000lm is fit for reading needs. If taking no consideration of other factors, even using single LED chip with a luminous efficiency of 200lm/W, 100-150 pieces are necessary. However, currently, the common luminous efficiency of single white-ray LED chip is only about 30lm/W-40lm/W, far less than the assumed 200lm/W. It is cleared that no both in power consumption and in production costs, compared with energy-saving lamps, white-ray LED lights is in no match. In addition, the immature design of optical technologies reduced the stability of the lighting distribution of LED lamps. Obtaining a much more even lighting distribution, manufacturers have to increase production costs. In terms of spot lighting applications, LEDs with a small amount of energy consumption can meet the needs of visual, as well as evenness. In CRI aspect, the current white-ray LEDs can meet the needs of the general indoor activities.