As a kind of green energy, electric energy accounts for a growing proportion of energy applications in various countries. According to a survey conducted by Chen Lianghui, an academician of the Chinese Academy of Engineering, it is estimated that in 2010, the country's electricity consumption will reach 2.7 trillion kWh, of which lighting power will exceed 300 billion kWh. Because LED lighting consumes only 1/3 of traditional incandescent lamps and HID lamps, it would be possible to save 2/3 of energy if LED lamps are used to replace existing conventional lamps. Its energy saving effect is evident.
The application of dimming technology will further reduce energy consumption and save electricity for lighting. At present, public lighting power accounts for one-third of the entire lighting field, up to 100 billion degrees. In China, cities generally start to light from 5:30 or 6:00 in the evening. However, after 9:00 in the small city and after 12:00 in the big and medium-sized cities, there are few passers-by on the road, even in Beijing, Shanghai and Guangzhou. In the city, after 2 or 3 in the morning, pedestrians and vehicles are rare on the road. From this period of time to 6 o'clock in the morning, the street lights are extinguished, and it is obviously not necessary to maintain a high illumination on the road with low traffic flow. If dimming technology can be adopted, the output power of LED street lamps will be reduced to half with the decrease of traffic flow after 12 o'clock in the middle of the night, which will save up to 50 billion kWh of electricity, which is equivalent to saving the annual power generation of the Three Gorges Power Station in 2009. About five-fifths (the Three Gorges Power Station generated 79.85 billion kWh of electricity in 2009), and the energy-saving effect is very significant.
The use of dimming technology to reduce the output power will significantly improve the working environment of LED lamps, extend the life of lamps, and improve the reliability of LED lighting controllers. The key factor affecting the reliability of LED luminaires is temperature. Whether it is an LED driver or an LED chip , the higher the ambient temperature, the sharper the life and reliability. Figure 1 shows the relationship between LED driver power supply life and temperature. When the ambient temperature is 25 °C, the LED power supply life is up to 320,000 hours, and when the temperature rises to 60 °C, the life of the LED power supply will be shortened to only 35,000 hours.
The higher the temperature, the more pronounced the light decay of the LED chip. Figure 2 shows Cree's LED light source light decay curve. It can be seen from the figure that the light decay of the LED is closely related to its junction temperature. The so-called junction temperature is the temperature of the semiconductor PN junction. The higher the junction temperature, the earlier the LED light source has a light decay, that is, the shorter the lifetime. As can be seen from the figure, if the junction temperature is 105 ° C, the LED light source whose brightness is reduced to 70% has a lifetime of only over 10,000 hours; when the junction temperature is 95 ° C, the LED light source has a lifetime of 20,000 hours; and the junction temperature is reduced to 75 ° C. The life expectancy can be as long as 50,000 hours, and the life expectancy can be extended to 90,000 hours at 65 °C. In summary, the key to extending the life of an LED light source is to reduce the junction temperature.
With dimming technology, as the output power is reduced, the loss of the drive power supply will also decrease, and the case temperature will also decrease. As shown in Figure 3, the 200W LED drive power output power and the case temperature curve. When the ambient temperature is 25 ° C full load output, the case temperature is 50 ° C, and when the dimming technology is used to control the output is only 50% power, the case temperature drops to 40 ° C, the life will also double, the reliability can be increased by 25% - 40%.
Traditional incandescent lamps or HIDs were unable to dim, and in the 1970s Japan's energy crisis, they used the interval lighting method to try to save energy. However, due to the uneven illumination of the road surface, the visuals of passers-by have caused problems, and public security and road traffic accidents have risen sharply. Finally, the interval lighting method has to be abandoned. The rapid development of dimming technology will bring LED lighting dimming system into a new field, so that the green environmental protection and energy-saving LED lighting application will be widely popularized and promoted.
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