Design Of Lighting LED Constant Current Source Driver

Lighting technology related with people daily life has developed for more than one hundred years. Lately, as a new kind of electronic light source, LED (light-emitting diode) has advantages of high efficiency, durable and safety, so it would be widely used in the future. At present, low power LED applications have been developed, but the history of high power LED applications is not very long, so it still has a potential market. The thesis is about to find out a way to drive high power LEDs, which could be used in Automotive Lighting.Luminance is mainly controlled by LED driving current, so it is best to drive LEDs with a constant-current source. Compared with other driving mode, switching power technology has high efficiency, so the thesis gives a LED driver in detail with switching power technology. The driver in this paper is a high frequency step-down DC-DC converter designed to operate as a constant-current source. An internal current reference and a sample circuit monitor the output current allowing accurate current regulation, ideal for driving high current LEDs. The high frequency permits the use of small external components,a current mode PWM architecture provides fast transient response and cycle-by-cycle current limiting, unique dimming circuitry allows a wide dimming range.The design process is as follow: firstly, explain the basic operating principles of Buck converter and analyses the disadvantages and advantages of each modulation mode and control mode; secondly, combining the applications of high power LEDs, a current mode PWM architecture is used for controlling the driver,and the operational process is initially analyzed here; thirdly, explain the performance requirements and the design consideration about each sub-circuit; finally,simulate the whole structure to verify functions and concretely give application information about the switching frequency selection, the input voltage range and the dimming control.