Heat Dissipation Analysis And Optimization Of LED Headlamp

With the development progress of LED semiconductor lighting technology and the automobile industry, LED headlamps have been more and more widely used as a new green car lighting. The highlight advantage of low power consumption is very coincide with the national strategy of saving energy and developing low-carbon economy. Furthermore, compared to the conventional halogen and xenon lamps, LED headlamps also have long life, quick start, small size, and flexible structure design, etc. So it is believed that in the future field of car headlights, LED headlamps will replace the traditional halogen and xenon lamps, with the LED headlamp technology mature and gradually reducing product costs.Despite the obvious advantages of LED headlamps, however, they have three main problems: the optical design, power supply design and heat dissipation design. These problems become the difficult design points and lead to the consistent high cost of the LED headlamps. Especially the heat dissipation design is always the most difficult problem of LED headlamps design. To solve this problem, the following studies are made:Firstly, through the depth study of the principles of LED heat created, and setting the thermal resistance and junction temperature as control indicators, the paper reveals the major cooling mechanism of LED headlamps- the heat is conducted from the chip to the radiator, and then diffused to the surrounding air through the convection heat transfer between the radiator and air.Secondly, the paper establishes the thermal model of LED headlamps based on thermal resistance network, and then takes a kind of LED headlamp from the market as a sample, to get its temperature distribution by making a thermal steady-state simulation on its cooling system based on ANSYS Workbench. The results verify that the active-fan cooling system design adopted by this headlamp can meet the cooling requirement well.Thirdly, according to the analysis on heat conduction path of LED headlamp, the paper describes the influence generated by each design aspect to the entire cooling system, from the chip package, metal substrates, thermal interface materials to the radiator design and so on.Fourthly, the paper has made a structure optimization design for the fin-radiator which is most commonly adopted by LED headlamps based on the optimization tools of ANSYS Design Xplorer. It reveals the impact on the cooling performance of the fin-radiator generated by the six design parameters: fin length, fin width and so on, base plate thickness and so on. The results show that fin height is the most important factor to affect the cooling performance. After the optimization design, the maximum temperature of the fin-radiator is decreased from 79.6 ℃ to 70.8 ℃,which meets the design requirements(the maximum design temperature is 73 ℃).