The "Ten Cities and Ten Thousand Miles" LED streetlight demonstration project promoted by the Chinese government was finally proved to be a policy propaganda behavior. LED street lights are still far from commercialized, because it takes less time for LED street lights to gradually decay or not at all. Bright. The reason is not that the life of the high-power LED is not enough, but the heat-dissipation technology of the LED driver power supply is still not closed, so the brightness of the LED is not accelerated by the heat, or the LED driver power source is burnt due to the inconspicuous peripheral small device. electricity failure.
"High-power LED driver power supply has low efficiency, limited working space and poor thermal design. The LED driver power supply has a high working temperature. Many devices can't stand the high temperature and are burned. I also help us. Customers have seen burnt out devices, many of them are small transistors and diodes, but they collapse when they burn out the entire power supply." Liu Xuechao, business development manager of TI's high-performance analog products, explained, "This seems like a small problem, but The temperature generated by the LED is very high, 70% of the heat is dissipated through the heat sink, and the heat sink is behind the drive power. The temperature is very high and difficult to control."
Therefore, the industry's current efforts are to improve efficiency, reduce temperature, increase integration, reduce component count, and use reliable components as much as possible. "For example, inductance is a very reliable thing, and inductance is something that everyone has used for thousands of years, not active devices," he added.
In response to this goal, TI officially launched a revolutionary innovative high-power LED (>100W) drive architecture this year: two-stage multi-string LLC topology architecture, compared to the traditional LLC half-bridge drive architecture, the innovation architecture province Multiple series of constant current DC/DC step-down circuits are eliminated (so that each string can save expensive high-voltage MOSFETs, inductors, and electrolytic capacitors), and two-stage LLC resonant circuits connected in series with multiple transformers can directly achieve constant current. The efficiency has been greatly improved to 92%, which is 4-5% higher than the traditional architecture, the number of components is also greatly reduced, the reliability is improved, and the EMI design is simpler. (As shown below)
"In short, it is to synthesize the constant voltage level and the constant current level that are originally needed into one level, which is equivalent to saving one constant current level." Liu Xuechao said.
TI's original dual-stage multi-string LLC topology for high-power LED lighting (Source: TI)
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