LED显示屏驱动电流的潜在电磁干扰分析

为了控制对发光二极管(LED)显示屏亮度调制时电 源电流产生的电磁干扰(EMI),对3种脉冲宽度调制(PWM)调光方法下显示 屏的电源电流频谱进行了研究。首先比较了线性、离散和选通3种PWM的调光原理和潜在 EMI,设计了基于电流频谱分析的EMI评估法,并通过对单亮度和亮度均匀渐变图像 的仿真,验证了评 估法的有效性；最后通过对LED显示屏真实图像显示时的电流频谱分析,比较了3种调光方 法的潜在EMI。实验结果表明:线性PWM方式下,同时点亮LED会产生较大的EMI；离 散PWM对消耗电流的 延展和码制对消作用,可以有效地减小EMI；选通PWM随着选通等级的提高,最小点 亮脉冲变窄不利 于减小EMI。本文的分析结果可用于在LED显示屏产品设计时,合理进行EMI分析 与分配,预估产品的电磁兼容性。

Potential EMI analysis of the LED display panel driving current

To control the electromagnetic interference (EMI) generated by the power sup ply of dimmed light emitting diode (LED) display panels,researches have been finished on the power supply current spectrum of th e panel with three pulse width modulation (PWM) dimming approaches.Firstly,we compare the dimming principles of the linear PWM,the discr ete PWM,the gated PWM,and their potential electromagnetic interference.And then an assessme nt method of electromagnetic interference based on current spectrum analysis is designed,and the validity o f the method is verified by the simulation of the single brightness and the gradually-changed brightness images .Finally,by the current spectrum analysis of an LED panel displayed with real images,we compare the potential interferenc e of the three dimming approaches.Experiment results demonstrate that large interference will be gener ated when LEDs are lighted simultaneously with the linear PWM,and it could be effectively reduced by the e xtension of consumed current and the code compensation effect with the discrete PWM,and the narrower minimu m lighting pulse duration is not in favor of interference reduction with the increment of gating levels used in the gated PWM.The achieved analysis results could be applied to reasonably carry out electromagnetic interf erence analysis and distribution when designing new LED panels,and to forecast the electromagnetic compatibility of the products.