基于PDM的LED背光调亮技术研究

Research of LED Backlighting Dimming Technology with PDM Control Method

为解决PWM(Pulse Width Modulation)背光调亮技术的应用缺陷,提出了一种基于脉冲密度调制(PDM:Pulse Density Modulation)的背光调亮算法。对PWM和PDM调亮波形进行了频域仿真分析,结果表明PDM的谐波被移到频率更高的位置,避开了电源传导发射试验CE101的测试频段(25 Hz^10 kHz)的范围,从而更容易满足电磁兼容要求。对某产品分别采用PWM和PDM调亮技术进行CE101和负载特性对比测试,测试结果表明:与PWM调亮技术相比,PDM调亮技术的电源电流波形比较平缓,不会跟随调制脉冲出现剧烈的振荡,负载特性具有明显的改善。基于PDM的LED背光调亮技术优势明显,更适合应用在电磁环境复杂、负载特性敏感的领域。

A LED backlighting dimming method based on PDM algorithm was proposed in order to solve the defect of PWM dimming method in application.The frequency domain simulation analysis of waveforms showed that the harmonic frequency of PDM method moved to higher region than PWM method,avoiding the test frequency band(25 Hz^10 kHz)of CE101 so that it was easier to pass the EMC CE101 test with PDM method.As a result,compared with PWM method,the current waveforms were relatively gentle and the load characteristics were obviously improved by using PDM method.In summary,PDM method has advantages in electromagnetic environment and load sensitive applications.