A Constant Current Type DC-DC High-power LED Driver Circuit Design

Nowadays the problems of energy sources and environment become more and more serious, semiconductor lighting has won people's attention for its unique attributes of low energy consumption, low pollution, long life and high efficiency. As the quality of power LED improves and the cost of power LED reduce, semiconductor lighting will replace incandescent and fluorescent lighting gradually. With the development of High Power LED, the research of its constant current driving circuit has also been greatly accelerated.The subject of the dissertation originates from a cooperative project funded by a power source company. The dissertation aims to design a High Power LEDs constant current driving converter which is highly demanded by the market. The input voltage and load voltage of LEDs strings (i.e. numbers of LEDs) changes within a certain range, It is required still having a high-precision constant current. And the circuit structure is simple, the cost is low, and the efficiency is high.The research can be summarized as follows:First, the features and the development of high power LED lighting and the classification of white LED driver circuits were introduced. Then the thesis analyzed the principle and control strategy of the DC-DC converter circuits, including the principles analysis of the three circuit topologies, two kinds of feedback control modes and three kinds of control mode. Then, the control principle, circuit algorithm and circuit structure, been presented in this paper, of constant-current output of the Buck-type, Boost-type, and Buck-Boost type high-power LED converter is analyzed. Finally, the analysis and design of various cell circuit is finished. A Buck-type and a Flyback-type LEDs constant current DC-DC driving converter are set up for driving several 350mA, 1W LuxeonTM Star. Experiments were carried out and the impacts of variables on constant current accuracy were analyzed. The experimental results have a good agreement with theoretic analysis and circuit structure design.