Applied Study Of Constant Current DC-DC Swtich Converter In LED Driving Circuit

Green lighting is the one of significant issue for human society’s sustainable development. LED is a new green light, and also is the one of the most potential for development, because of its energy saving, environmental protection, high efficiency, long using time and wide application. It’s leading the forth evolution of human’s lighting industry, also, is paid high attention by most of countries in the world. Due to the volt-ampere characters itself, LED needs constant current in outputs. Meanwhile, using switch converter in LED driver has the ablility of constant current output and high efficiency, so it is used widely in LED drivers. This paper studied in DC-DC Boost circuit in LED drivers, besides, in this paper, technologies with Single-Inductor Multiple outputs and Peak Current Mode are used in this converter.This paper introduced the electrical specifications and features of highlight white LED; and it showed LED had better use constant current driver. Secondly, compared some technologies with constant current, and then chose the technology of Single Inductor Multiple output in switch converter because of lower cost and smaller size. Thirdly, this paper took the single inductor double outputs as an example, analyzed DC-DC constant current driver. Due to the circuit needs feedback regulation, Peak current mode was used in the control circuit. At last, PID control was added in the compensating circuit to keep the circuit stable.This paper not only analyzed in theories but also made experiments; for one thing it used state-space average method to analyze the working condition and to derive the small signal average model in DCM mode, then analyzed peak current control mode and the stability after adding the PID module, and obtained the small signal block diagram with driving circuit and open-loop transfer function with the whole system, at last analyzed the stability with the whole open-loop and the closed-loop. For another it simulated the circuit and designed a model circuit to test the circuit. As non-isolated Boost Single inductor double outputs for example, explained the main circuit, control circuit and compensating circuit. Then tested the outputs voltages and currents, the results basically corresponded the hopes.