A scheme for improving the color rendering index of LED lighting

Abstract: with the continuous development of LED technology, the LED light source as possible, because the light source in lighting on the color index CRI has strict requirements, and the current white LED technology in color of the not mature, make it become the main obstacle of restricting LED as lighting source.

White light for the composite light, through the three prism is very easy to break out of the white light contained in a variety of colors. The LED is a kind of comprehensive light source, which is the theoretical basis for the high color rendering of LED lighting products.

Light is a kind of particle size material, which contains the wave characteristics including particle characteristics, which has the characteristics of strong composite, so from the characteristics of the nature of light and LED speaking, to become a high-quality LED lighting source is possible.

The current white LED technology, production process mainly uses the blue chip coated with fluorescent powder, this technique developed by Nichia Corporation, the luminescence principle of fluorescent lamp to follow from a certain sense, this technique due to the lack of red and green components, so there are congenital defects of the color index is insufficient, at present to compensate for this defect, the phosphor technology has become the main direction in the industry.

The blue chip is coated with fluorescent powder to produce white light technology, this technology is in principle can produce better effect of white light, but in use because of the ability to adapt to the environment is weak, caused by differences in theoretical and practical products, this difference is largely due to heat generated LED effect on the temperature of phosphor.

We all have this experience, high power white LED with working time, heat generation and heat loss gradually reached the equilibrium state, the equilibrium temperature is higher, the effect of white LED using a single type of fluorescent powder is bigger, the effect of temperature on the luminescence properties of phosphors;

From here you can see that, with the increasing temperature of LED, the activity of fluorescent powder will be significantly reduced (F / Celsius conversion formula is: =5/9* degrees Celsius (-32 degrees Fahrenheit), at 100 degrees when the phosphor activity is better, but at 250 degrees Fahrenheit (120 degrees Celsius) or fluorescent powder lost as basic activity.

The influence of temperature on the activity of phosphor is also affected by the wavelength of light wave excited by phosphor.

From here you can see that with the increase of LED temperature, fluorescent powder in the gradual inactivation of activity at the same time, the phosphor light emitted by the wavelength with the offset, the offset is red shift, namely the luminescence wavelength toward the red wavelength shift; this phenomenon seems to suggest that with the rise of temperature, the color of white LED should be good, but actually reduced, seemingly contradictory problems? The essence of this phenomenon is to offset the red fluorescent powder, fluorescent powder less than inactivation, which is inspired by the fluorescent powder in the condition of high red light is not enough to compensate for the loss of hybrid red, so the color index LED temperature increased or decreased, and the white LED with temperature increase the color index decline is consistent.

From the above analysis, it can be concluded that the primary means to improve the color rendering index of phosphor white LED is to reduce the temperature of LED, and the second is to improve the adaptability of phosphor to high temperature. Third is the use of color compensation technology, the use of red or amber LED color rendering index compensation.

In reducing the LED thermostat, is the most effective means of LED package design high heat dissipation performance, which is one of the direction of China's LED industry in the near future to make significant progress in intellectual property rights on the LED, because the LED is a low voltage in electronic products, electrical safety requirements more relaxed, the heat conduction substrate so many materials can be used, and we present this industry study less, cause often violated foreign intellectual property disputes.