峰值I^2C控制Buck型LED驱动电源稳定性分析

Stability Analysis of Peak I^2C Controlled LED Power Driver Based on Buck Converter

研究用于恒流驱动发光二极管(LED)的峰值I^2C控制技术。为了分析峰值I^2C控制的稳定性,以Buck型LED驱动电源为例,建立基于傅里叶级数的控制方程,推导驱动电源的稳定边界。采用一阶泰勒近似,给出稳定边界的简化方程。根据其简化方程,分析峰值I^2C控制Buck型LED驱动电源的LED等效串联电阻、内环权重因子的分配、外环补偿器比例系数的设计以及斜坡补偿的引入对驱动电源稳定工作范围的影响。研究结果表明:随着输出电流权重因子和补偿器比例系数的增大或是LED等效串联电阻的减小,驱动电源稳定工作范围将不断缩小;引入斜坡补偿后,可以消除驱动电源的不稳定工作现象,拓宽驱动电源的稳定工作范围。最后,通过仿真与实验对所提的理论分析进行验证。

Peak I2C control for lighting emitting diode(LED)driver to output constant current is investigated.In order to analyze the stability of peak I2C control,taking buck-based LED driver as an example,its control equation was established by Fourier series.The stable boundary equation was derived as well,which was simplified by the first-order Taylor series.With the increasing of the weight factor of output current in inner loop,the proportional term of compensator in outer loop increases,and the equivalent series resistance of LED varies.Their effects on the stability of LED driver were analyzed with the simplified boundary equation.It is found out that,when the equivalent series resistance of LED decreases,or the weight factor of output current and the proportional term of compensator increase,the stable region of the LED driver will be narrowed;slope compensation can extend the stable region by lessening the unstable phenomenon.Finally,the stability analysis is verified by computer simulation and hardware experiment.