Design principles and case LED Driver

This article describes the application of special lighting, and then in the DC / DC switching regulator design using constant current and voltage to achieve the basic principles and practical examples described and explained the high power LED driver design and thermal design should pay attention to some of the problems concluded that the application of new high power LED driver design of the new requirements, National Semiconductor is to present a complete solution guide that helps in the LED lighting industry, electronic design engineers the latest design technology LED drive system complete control.
Although no large-scale high-power LED to replace traditional incandescent, but they are indoor and outdoor decoration, special lighting, with more and more applications, so master the development of high-power LED constant current driver design new applications of high power LED is essential. LED's brightness and ability to work can be divided into high-power LED, high brightness LED and general LED. In general, high power LED, at least in the more common power 1W 1W, 3W's, 5W's, 8W and 10W of.
LED constant current driver, LED applications increase the optical efficiency of the design are two key issues, the paper describes the application of high power LED constant current driver program selection guide, and then to National Semiconductor (NS) products, for example, the focus on the constant current LED driver circuit clever use of high power LED to improve the efficiency of the sampling resistor, and gives the 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 overall system performance reliability. Currently, National Semiconductor's LED driver, mainly in the high-end LED lighting and lighting in the market. Divided into two kinds of indoor and outdoor lighting, LED indoor lamp power applications, because the environment in two ways AC / DC and DC / DC converter, so the choice of driver chips, to be considered from two aspects.
1. AC / DC converter
AC / DC to 220V AC input and 12V AC input. 12V AC, widely used in power halogen hotel, in the design of the existing LED 12V AC to keep the existing conditions. Design for the replacement of halogen, National Semiconductor LM2734's main advantage is small size, high reliability, output current up to 1A, only a small diameter of the characteristics of halogen lamps.
Replacement halogen lamps, LED general 1W or 3W to light. Compared with halogen lamps, LED lamps have two advantages: (1) light source are concentrated, 1W lighting to obtain the equivalent of more than ten watts of halogen light, so more power; (2) LED light than halogen lamps long life.
LED lighting is a major weakness of the angle is too narrow, the cost is relatively high. But in the long run, LED lamp life longer, they still have a very large cost advantage. 220V AC / DC converter (eg LM5021) the stage lights and lock the main street market.
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