As the forth-generation light source, LED has great development prospects because of its unmatchable advantages: energy conservation, environmental protection, and long lifespan. However, though LED products have long lifespan, it could not light for ever. All LED lighting fixtures have lumens depreciation. Here we take the MR16 LED as the example and analyze why lumens depreciation happens.
Generally the lifespan of the MR16 LED is defined when its luminous flux reduces 30%. Its brightness becomes lower and lower over time and finally the light burns out. Following are some factors that may cause the lumens depreciation:
1. The transparent epoxy resin become yellow under high temperature and the light-admitting quality is influenced. The higher the working temperature, the faster this process proceeds. This is the main factor that causes the lumens depreciation of the MR16 LED.
2. If the working temperature of the MR16 LED exceeds the range that its chip can bear, the luminous efficiency will decrease quickly and obvious lumens depreciation happens.
3. The lumens depreciation of fluorescent powders will also cause the lumens depreciation of the MR16 LED, because the attenuation of fluorescent powders is very serious under high temperature.
4. The interior defects of the LED chip will quickly multiply and invade the luminous area, which may cause large quantity of non-radiative recombination centers and reduce greatly the luminous efficiency of the MR16 LED. In addition, the microdefects of the materials and the fast expanding impurities from the interface and plate will also be introduced into the luminous area and form deep energy level, which also will speed up the lumens depreciation of the MR16 LED.
From above analysis, we could see that high temperature is the primary reason that causes the lumens depreciation of the MR16 LED and shortens its lifespan. Thus LED manufacturers should make a break-through on the heat dissipation of LED products to guarantee the long lifespan.
