Study on Lighting System Integration Technology of High Power Multi-Chip LED Based on Heat Pipe Structure

Light emitting diode (LED) is a new light source which has the advantages of energy saving, environmental protection, long lifetime compared with traditional fluorescent and incandescent lights. But when LED are working, there is only 10%～20% power translate into light, and 80%～90% power translate into heat. So develop a new package structure which has high reliability and excellent optical performance is essential for application of LED. In addition, the popularization of LED will strongly promote the construction of economical society.According to two key issues of heat dissipation and optical design which restrict the LED technology development, this paper studies the heat dissipation problem of high power LED based on heat pipe structure, then investigates the illuminance and evenness of light emitter and improve the optical structure of LED.Firstly, the manufacturing process, materials, thermal management and optical design of high power LED are introduced based on investigated LED market and product application at home and abroad. And then the general research way of this paper is put forward.Secondly, aiming at a high power LED based on multi-chip packaging, the thermal design of heat pipe and fins is proposed. The material, working fluid and structure parameters of heat pipe are designed and selected. Then the capillary limitation of heat pipe is accounted. So the heat dissipating capability can be determined. Thermal resistance and thermal conductivity of heat pipe are estimated based on network of thermal resistance. According to design requirements of junction temperature and effective dissipation area of fins, junction temperature of LED chip is 62℃based on one-dimensional network of thermal resistance.Thirdly, the thermal simulation analysis of high power LED which based on heat pipe structure is took by ICEPAK software. The differential equations of thermal analysis and fluid analysis are study. The basic solution thought of finite volume method and ICEPAK software are introduced. The simulation model of high power LED based on heat pipe structure is developed, and boundary conditions are accurately set based on actual work condition of LED. When solving process finish, the results showed that the junction temperature of LED chips is 65℃. Compared with the result of chapter 2, the result of simulation by ICEPAK software is basically in accordance with the calculated data based on network of thermal resistance in chapter 2, which the change range is 4.8%. At the same time, the result also verifies the feasibility and effectiveness of heat pipe and fins. Aiming at the fin structure of LED dissipation system, the thickness, highness, spacing and effective dissipation area of fins which have influence on junction temperature of LED are comparatively analyzed. By comprehensive consideration, when the fin thickness of 1mm, a height of 25mm, fin spacing of 4mm, the dissipation effect is best.At last, the illuminance and evenness of high power multi-chip LED optical devices is systematically analyzed. According to optical properties of selected LED chips, intensity distribution of chips is imposed on surface of LED chips based on TracPro software, and optical properties of high power multi-chip LED is made a preliminary analysis. On this basis, different optical devices (lens and reflector) are selected to simulate ray tracing of LED. And the graphs of illuminance are obtained. Comparing with different simulation results, and finally a reasonable plan of optical design is presented.