Thermal Design And Simulation Of LED Lamps

In recent years, light emitting diode (LED) develop rapidly because of its high luminousefficiency and low energy consumption, and gradually penetrating into the modern lighting, becomea new type of cold light source which has the most promising in 21stcentury . The light-emittingprinciple is that the electrons and holes in the PN junction composited and happendelectroradiescence effect under the applied electric field, transform part of the energy into lightenergy, and the rest of the energy is converted into heat. At present, LED used in lighting area, heatdissipation become one of the key problems that need to be solved. Without good heat dissipationchannel, can make the LED substrate temperature rise which leads to wavelength red shift,luminous efficiency decreased, even affect the working life. According to report, the working life ofthe LED lamp work at 30℃is 20 times as much as work at 70℃，so the thermal failure become oneof the main failure mode. Thermal design is one of the key technologies for high-power LED lamps.In this paper, using finite element analysis software ANSYS to thermal simulation of LED, direct atthe package structure and heat dissipation structure of the high-power LED, establish heat transfermodel in Pro/E, and optimize the LED structure to improve the heat dissipation.At the first of the article, introduced the generation of heat in LED, thermal characteristic,thermal management, the importance of the heat dissipation design and research status. Combiningpowerful modeling capability of Pro/E and perfect analysis capability of ANSYS simulate thetemperature distribution of different package structure; analyze the heat dissipation capability ofdifferent package structure in the same condition. Then simulate to a 7W LED lamp at roomtemperature 20℃, get the steady-state temperature distribution. And compared with the actualtemperature, the results show that the simulation results and actual data are basically same, whichhas verified the method of using ANSYS to thermal simulation for the heat dissipation of LED lampis feasible.Through the thermal analysis of the LED lamp, found the lamp structure is defective and thetemperature distribution is nonuniform, so based on this heat sink structure for optimization design.Considering the heat dissipation process include heat conduction and heat dissipation, the heatthrough the line layer, isolation layer, substrate and heat conducting silicon to the heat sink, sodesign a reasonable structure of heat sink is very significant for LED thermal design. In this paper,simulate the influence of the multi-chip distribution structure, heat sink materials, the thickness andnumber of the fins to heat dissipation. Then optimize the heat sink structure, until get the best heatdissipation structure, make the maximum junction temperature reduced 2.678℃. Finally, after preliminary exploration of LED lamp thermal design, research the biggest bearpower number of the optimization structure, simulate the temperature dissipation of the 5~20Wlamps respectively. Combined with the temperature variation of the working environment, analyzethe influence of the environment temperature to junction temperature. In conclusion, this heat sinkstructure can support the maximum power of 17W at the maximum environment temperature 40℃.