超低纹波PWM编码技术分析

传统PWM(pulse width modulation)技术的不足之处是会产生纹波脉冲,对其他电路产生干扰。这对很多精度要求比较高的应用场合是非常不利的。一种基于脉冲编码的数字PWM方案,可以大幅度降低输出纹波的强度,可表述为:将PWM脉冲序列均匀的分布到整个PWM周期之中,最理想的情况是达到单个脉冲的程度。理论上PWM输出纹波与PWM信号各次谐波幅值具有很强的正相关关系,其中基波与二次谐波的所产生的纹波最为显著。深入的分析表明,这种编码映射方法可以将这2项均降低到数字PWM信号最低极限数量级。初步实验表明,这种技术的效果非常显著。

Analysis of ultra-low ripple PWM coding technique

Traditional pulse width modulation (PWM) produces harmful ripple, which will interfere with other circuits. It is very unfavorable for many applications where high accuracy is required. A digital PWM scheme based on code technique is proposed and it can significantly reduce the ripple. The scheme can be expressed as:the PWM pulse sequences are evenly distributed throughout the PWM cycle. The most ideal situation is up to a single pulse level. Theoretically, there is a strong positive correlation between the output ripple and the amplitude of each harmonic of the signal, in which the ripple generated by fundamental and the second harmonic wave is the most significant. More deep analysis shows that with the scheme based on code technique, the ripple can be reduced to the minimum order of digital PWM. Preliminary experiments show that the technique is useful.