Research And Realization Of Constant Current Control For LED Based On Robust Gain-scheduling

Energy saving is imperative and green, low-carbon economy will be the future trend of development with the global energy crisis and worsening environment. LED has been applied and researched widely in lighting, display and street lamps for its advantages of high efficiency, energy saving and environmental protection. It is well known that constant-current driving is commonly used in LED driver, where the switch-mode is the most widely used. Since the switches and the load are nonlinear in LED driver circuit, and the input voltage and load resistance are variable because of the impact of external factors, to ensure the precision and stability of the LED current when the system parameters change, and to make a minimal disturbance on the output current when there is an external disturbance, are important subjects to improve the performance of the LED driver.Microcontroller-based digital control technology has been widely applied in LED constant current driver with the development of computer technology and power electronics, which making many of the complex, advanced control algorithms being applied in the LED driver. Since then, a number of papers have used the classic control algorithms, such as PI, PID, or complex control algorithms, such as synovial control, fuzzy control. However, the controllers based on PI or PID algorithms are difficult to obtain a satisfactory dynamic performance and anti-jamming capability due to the uncertainties and nonlinearities in the system. You require extensive expertise when to design a controller based on synovial control or fuzzy control algorithms, and there are some difficulties to carry out the complex algorithms on microcontroller.A constant current control scheme that based on Robust Gain-Scheduling for LED by using Stm32 microprocessor is proposed in this paper. Firstly, to construct the LPV model of system that contains four vertices by making input voltage and equivalent resistance of LED to be the scheduled parameters. Then, a Robust Gain-Scheduling controller in H∞ norm for LED is designed by using the LMI related technologies. The controller designed is linear parameter dependent and the parameters of the controller will change to adapt to different working conditions when the system variable parameter change. The controller can not only configure the closed-loop poles in a designated area, but also minimize the disturbance on the output when there is an external disturbance. The control algorithm in this paper is simple and has a small amount of calculation because there is only a small number of parameters associated with the variable parameters need to be calculated online. Finally, to make a simulation and experimental analysis for the controler designed by this paper. The simulation and experimental data illustrate the effectiveness of Robust Gain-Scheduling control applied to LED constant current driver.