基于OS-PWM算法的LED驱动芯片设计与实现

Design and Implementation for LED Driver IC Based on OS-PWM Algorithm

为解决小间距LED (Light Emitting Diode,发光二极管)显示屏中存在的刷新率较低、灰度等级不高、低灰麻点、首行偏暗、开路十字架等问题,提出了优化打散脉冲调制(OptimizeScrambled Pulse Width Modulation,OS_PWM)算法,并基于该算法设计了多通道恒流LED驱动芯片。针对刷新率较低、灰度等级不高的问题,通过OS-PWM算法将显示周期均匀打散,在不影响总体灰度的前提下,提高刷新率;针对低灰麻点增加了等级优化,提升低灰显示效果;针对首行偏暗的问题提出了反向PWM计数方法,预留时间使电容提前放电,有助于改善首行偏暗问题;针对开路十字架问题,通过内建开路检测模块,从根本上屏蔽了这一问题。实验测试结果证明了设计的正确性和合理性。

For the sake of solving the problems of the fine pixel pitch LED display screen,such as the low refresh rate,low gray scale,pitting,the first line of dark,open road cross,following ghost and other phenomena,an OS-PWM algorithm based on traditional PWM algorithm is presented in this paper.Besides,a LED driver IC is designed based on this algorithm.First of all,to solve the problems of low refresh rate and low gray scale,the whole display cycle is evenly scattered by OS-PWM algorithm,and the refresh rate is improved without affecting the total gray scale.Secondly,aiming at pitting phenomenon,the registration optimal design was added to enhance the display effect of low gray scale.And then,the reverse counting method is adopt to solve the first line of dark problems,and the reserved time makes the capacitor discharge ahead of time,which is helpful to improve this problem.Finally,open detection circuit is built-in for the open road cross phenomena,fundamentally shield this problem.The experimental results show that the design is correct and reasonable.