LED Downlight Thermal Simulation and Light Source Layout Optimization Study

LEDs are used in lighting for a common application problem - heat dissipation. Currently, LEDs have only 20% to 30% photoelectric conversion efficiency, and the rest of the energy is converted into heat. If the heat in the LED chip of the lamp cannot be effectively dissipated, the PN junction temperature of the LED chip is too high, resulting in a decrease in luminous efficiency, a red shift of the emission spectrum of the chip, a decrease in color temperature quality, and a decrease in conversion efficiency of the phosphor [1], and a decrease in working life. It can even cause problems such as permanent failure of the LED [2]. Current LED lighting solutions are divided into passive cooling and active cooling, passive cooling solutions such as natural cooling, heat pipe technology, temperature equalizing plate technology, loop heat pipe technology [3]; active cooling such as air cooling, microchannel heat sink cooling, semiconductor cooling Cooling [4] and so on. These heat-dissipation schemes are relatively large in structure and can be used as an effective method in road lighting such as LED street lights and LED tunnel lights. However, LED downlights are affected by their size, appearance requirements, and working environment constraints. It still uses natural heat dissipation.

The LED downlight uses LED as the light source, and its structure is improved on the basis of the traditional downlight structure. LED downlights have the characteristics of traditional downlights, and at the same time have all the advantages of LED: energy saving, low carbon, longevity, good color rendering, fast response, etc. [5]. The design of the LED downlight is more beautiful and light, and the overall uniformity and perfection of the architectural decoration can be achieved during installation. The installation of the light fixture is not damaged, and the light source hides the interior of the architectural decoration, and the light source is not exposed. LED downlights usually use COB, array high-power LEDs (1W or more), arrays of low-power LEDs (0.5W and below), etc., in which the array of small-power LED light source has the best optical effect, and the human visual effect is soft. Uniform, most LED downlights are currently in this form of light source.

The finite element CFD simulation software can comprehensively analyze the heat conduction, thermal convection and heat radiation of LED lamps, analyze and solve the temperature field and flow field inside and outside the LED lamps, and is suitable for the current cooling simulation of LED lighting fixtures. Bai Kun et al [6] performed a finite element heat dissipation simulation on a 3-core white LED downlight, and analyzed the lateral thermal resistance and longitudinal thermal resistance of the thermal channel materials such as substrate, solder paste, copper foil and aluminum substrate, and proposed a Optimized design of rapid hot aisle using copper column to connect external radiator; Ma Xiangjun et al [7] used finite element method to analyze and calculate the temperature field of 15W LED downlight, further analyzed PCB thermal conductivity, thermal conductivity and chip position (relative to The effect of finned heat sinks on the heat dissipation of LED lamps. This paper will analyze the influence of LED light source on the heat dissipation of LED downlight from the main heat source of the downlight, and use the method of thermal simulation and experimental measurement to study and apply the research results to LED downlight product improvement. designing.

LED downlight cooling modeling and simulation

In this study, an 8-inch 25W LED downlight was selected as the main research object. The actual object is shown in Figure 1. The three-dimensional modeling model is shown in Figure 2.

Figure 1 LED downlight physical map

Figure 2 LED downlight 3D model

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