应用频率调制技术减小开关电力变换器的电磁干扰

EMI Reduction in Switched Power Converters Using Frequency Modulation Techniques

频率调制技术已应用于减小数百兆赫兹工作频率的数字系统时钟所产生的电磁干扰(EMI)。它的工作原理是:通过对初始固定时钟频率进行调制,将单次谐波的能量驱散至某个频带,从而降低处于谐波频率的EMI幅值。当今,随着电力变换器开关频率的提高,应用相关技术来减少开关电源电路的EMI是值得研究的课题。文章提出了利用相应的调制函数进行频率调制的理论基础,分析了不同调制方案及参数情况下减少EMI发射的效果,并且和其他随机调制法进行了比较。用降压变换器对该方法进行了验证试验。此外还对最佳调制函数和参数进行了简要的讨论。

Frequency-modulation techniques have been used to reduce electromagnetic interference （EMI） produced by the clock of digital systems working in the range of hundreds of megahertz. The working principle consists of modulating the original constant clock frequency in order to spread the energy of each single harmonic into a certain frequency band, thus reducing the peak amplitude of EMI at harmonic frequencies, Nowadays, the switching frequency of power converters has increased up to values that make interesting to the application of such techniques to reduce EMI emissions due to switching of power circuits. This paper presents the theoretical principles of frequency modulation using deterministic profiles for the modulating function. It shows the effectiveness of such methods in terms of EMI reduction for different modulation profiles and other parameters. The method is compared with other methods using random modulation. Tests carried out on a buck converter are presented for experimental validation of the method. A short discussion on optimal modulation profiles and parameters is also included.