How to Solve the Heat Dissipation Problem of High Power LED Lighting

- Sep 17, 2019-

Two kinds of LED lighting applications with the largest consumption and the highest power are the back lighting of large screen LCDTV display and automobile headlamp. Take a look at the standard LED headlights used by Lexus, Audi and even GM's Cadillac Escalade. The overall lighting structure of all these cars is very similar. Each headlamp consists of five kinds of LED power supply beams optimized for various lighting requirements, including low-light, high-light, turning auxiliary lights, daytime driving lights and turning signal indicators.

Standard LED lighting beams usually require 35W to 50W power supply. This may not seem like a lot of power; however, the brightness of the LED is 10 times that of the HID halogen lamp, so the output of the LED is equivalent to 500 W halogen lamp. The power required for the high-beam is generally the same or slightly higher than the standard illumination beam, while the power required for the turning auxiliary lights, daytime driving lights and steering signal indicators is lower. However, the overall vehicle headlamp will consume more than 200 W of electricity, which may cause significant thermal power dissipation problems. This is really not a good thing, because as the working temperature rises, the light output and working life of the LED will decrease rapidly.

There are many ways to deal with this problem. One is to add a large number of radiators to remove heat from the lighting. However, this can create another set of problems, including increased costs and weights due to the use of heat dissipating materials. The most effective way to solve this problem is to use a highly efficient driver (efficiency > 93%) to minimize the thermal dissipation of the LED driver circuit. This is not as difficult as it sounds, because a 50W high-light usually consists of 14 tandem 1A LEDs. Because the forward voltage drop in the whole temperature range is about 4V per LED, the boost converter LED driver topology can raise the nominal battery voltage of 12V to just over 56V with 93% efficiency. This makes only 3.5W power dissipation required. For this power dissipation value, it is installed in the printed circuit board of the LED automobile headlamp. Low-grade copper radiators can easily meet the requirements.

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