This paper introduces the special lighting applications, and then elaborated on the use of DC / DC switch to constant current constant voltage regulator designed to achieve the basic principles and practical examples, and explains the high power LED driver design and cooling part of the design should be noted issues, concluded that new applications of high power LED driver design the new requirements, National Semiconductor is given a complete solution guide, it helps in the LED lighting industry, electronic design engineers have complete control of the latest LED driver system design technology.

Although large-scale high-power LED is not yet replace the traditional incandescent, but they are indoor and outdoor decoration, special lighting, has a more and more applications, so master the high-power LED constant current driver design techniques for the development of high-power LED The new application is essential. LED brightness in accordance with power and can be divided into high-power LED, high brightness LED and general LED. In general, high-power LED 1W of power at least over the relatively common are 1W, 3W, 5W, 8W and 10W.

LED constant current driver and improve the optical efficiency of LED application design are two key issues, this paper describes the application of high power LED constant current driver program selection guide, and then to National Semiconductor (NS) products, for example, focus on how skillful use of LED constant current drive circuit to improve the sampling resistance of the efficiency of high-power LED, and gives high-power LED driver design and thermal design considerations.

Driver Selection

LED lighting LED driving only a small fraction of the cost, but it is related to the reliability of the whole system performance. Currently, the U.S. National Semiconductor LED driver program mainly located in the high-end LED lighting and lighting markets. Divided into two kinds of indoor and outdoor lighting, indoor LED lights because the power applied environment AC / DC and DC / DC converters in two ways, so the choice of driver chips have to be considered from two aspects.

1. AC / DC converter

AC / DC into 220V AC input and 12V AC input. 12V AC is widely used halogen hotel power, the existing LED 12V AC in the retention of the existing conditions of the design. The design for the replacement halogen, National Semiconductor LM2734's main advantage is small size, high reliability, output current up to 1A, just for a small halogen lamp Diameter characteristics.

After replacing halogen lamps, LED lamps generally made of 1W or 3W. Compared with halogen lamps, LED lamps have two advantages: (1) light source are concentrated, 1W lighting obtained is equivalent to more than ten-watt halogen light brightness, thus more power; (2) LED lamp life than halogen long.

The main weakness of LED lamp lighting angle is too narrow, the cost is relatively high. But in the long run, the longer life of LED lights, they still have a very large cost advantage. 220V AC / DC converter (eg LM5021) the stage lights and lock the main street market.