Tsinghua research and development of a new type of urban road lighting LED light source breakthrough

State Key Laboratory of in the Department of electronic engineering Tsinghua University Professor Luo Yi Integrated Optoelectronics Research Group of new power type LED lighting source city based research and development through the serious technical bottlenecks, making the actual illuminance distribution of LED lamp is approximately rectangular, and the illuminance distribution is very uniform, and than the current road using high-pressure sodium lamp comprehensive energy saving more than 60%. The day before, the project passed the project expert group of Guangdong province science and Technology Department of the appraisal committee believes that the main technical indicators of the results reached the leading domestic level.

The street is an important part of city lighting, the lighting power consumption occupies the most of the electricity used. High pressure sodium lamp is often used in traditional street lamps. The high luminous efficiency of high pressure sodium lamp has the disadvantages of uneven illumination distribution, color distortion of the object under illumination, severe glare, short life and high maintenance rate, and the overall glazing efficiency is low. Therefore, it is of great significance to develop a new type of street lamp for urban lighting energy conservation.

The luminous efficiency of white LED GaN based blue LED and yellow phosphor synthesis has reached 130 LM / W, and the device has low production cost, stable performance, easy to accept the market, high efficiency and energy saving, long life, good color index, cold light source, environment friendly, so great may be the first choice for the next generation of new street. LED is a light emitting diode (Light Emitting Diode) the English abbreviated form, it is a light emitting device of semiconductor pn junction formation based on the forward bias voltage and the injected current, injected into the P region of the hole and injected into the N region electron in diffusion into the active region after radiation and emit photons, the direct transformation of electrical energy for the light.

However, the production of high power LED street lamp is facing serious technical bottleneck. The intrinsic characteristics of the single power LED, such as the smaller luminous flux and the distribution of the far field distribution of the chip, cause the semiconductor lighting technology to face higher optical and thermal technical barriers.

According to the special problems of power type LED used in city road lighting, Tsinghua University State Key Laboratory of Integrated Optoelectronics Research Group of Professor Luo Yi established science and technology research team, made a great breakthrough in the optical system of LED lamp and heat dissipation structure.

The research group first proposed the new design idea. The originality of the research group, the output of each power type LED light distribution is designed to be consistent with the provisions of the road lighting standard uniform rectangular illuminance distribution. The research group led by Professor Luo Yi in the development of the non imaging optical system design theory, put forward a method of separation of variables defining optical mapping model mapping method, using numerical method to solve the three-dimensional light distribution of this street. At the same time, the 3D surface modeling, the modeling method of discontinuous surface, more accurately control the shape of the lens surface, which is very simple and effective to obtain the ideal rectangular illuminance distribution. On the basis of the above work, a power LED optical system with independent intellectual property rights of high light extraction efficiency and rectangular uniform illuminance distribution is obtained

Guangdong Dongguan KingSun group jointly with Tsinghua University, successfully packaging and application technology Tsinghua University has with independent intellectual property rights for city lighting power LED implementation industrialization. At the same time, the two sides have made great progress in the high efficiency, high reliability, intelligent cluster LED drive technology, unique industrial LED street lamp assembly technology.

A new type of power type LED lamp light interception Tsinghua University Qinshang group developed the actual lighting effects as shown in figure 1. After testing, the rectangular illuminance uniformity can reach 0.64, the optical system of light extraction efficiency reached above 84%, a single power white LED luminous efficiency can reach 90 LM / W, than the current road using high-pressure sodium lamp comprehensive energy saving more than 60%.

At present, the project has been successfully applied to the road lighting in Changping City, Guangdong Province Science Center and the Olympic Gymnasium of Tsinghua University (see Figure 2), and has achieved good energy-saving and lighting effects.

According to estimates, if the country's road lighting are efficient, new LED street lamp, it can save 42 billion kwh per year, equivalent to saving the standard coal of 15 million 800 thousand tons, close to the production of several large coal mines a year. At the same time, not only to reduce the waste of water resources, but also reduce the life of the people in the vicinity of the power plant and plant growth caused by pollution of coal dust emissions 4 million 700 thousand tons, reducing acid rain SO2 emissions 440 thousand tons, therefore, it is of great economic, social and environmental benefits.