Design example of high power LED constant current drive circuit [图]

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In general, the power of high-power LEDs is at least 1W, and currently more common are 1W, 3W, 5W, 8W and 10W. Constant current driving and improving the optical efficiency of LED are two key issues in LED application design. This article first introduces the application of high-power LED and its selection guide for constant current driving scheme, and then takes National Semiconductor (NS) products as an example. Focus on how to skillfully apply the sampling resistor of the LED constant current driving circuit to improve the efficiency of high-power LED, and give attention to the design and heat dissipation design of high-power LED driver .

Although high-power LEDs can't replace traditional incandescent lamps on a large scale, they are more and more widely used in indoor and outdoor decoration and special lighting. Therefore, master the design technology of high-power LED constant current driver, and develop high-power LEDs. The new application is crucial. LEDs can be divided into high-power LEDs, high-brightness LEDs, and ordinary LEDs according to power and luminance. In general, the power of high-power LEDs is at least 1W, and currently more common are 1W, 3W, 5W, 8W and 10W. There are 1W and 3W LEDs that have been used in large quantities, while 5W, 8W and 10W LEDs are relatively rare. It is expected that high-power LED lights will be widely used in the 2008 Olympic Games, so the electronics and lighting industries are not concerned about the development and application of new LED lighting technologies.

Constant current driving and improving the optical efficiency of LED are two key issues in LED application design. This article first introduces the application of high-power LED and its selection guide for constant current driving scheme, and then takes National Semiconductor (NS) products as an example. Focus on how to skillfully apply the sampling resistor of the LED constant current driving circuit to improve the efficiency of high-power LED, and give attention to the design and heat dissipation design of high-power LED driver . The choice of driver chip LED driver only accounts for a small portion of the cost of the LED lighting system, but it is related to the reliability of the overall system performance. At present, National Semiconductor's LED driver solutions are mainly positioned in the market of high-end LED lighting and lighting. Lighting is divided into indoor and outdoor. Since the power environment used for indoor LED lights has AC/DC and DC/DC converters, the choice of driver chips should also be considered from these two aspects.

Conversion from constant voltage drive (left) to constant current drive (right) using the FB feedback terminal of the DC/DC regulator

Figure 1: Conversion from constant voltage drive (left) to constant current drive (right) using the FB feedback terminal of the DC/DC regulator

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