基于分数阶混沌的反激变换器辐射EMI主动抑制

Active Suppression of Radiated EMI in Flyback Converter Based on Fractional-order Chaos

快速通断的开关信号是造成开关电源电磁干扰EMI(electromagnetic interference)的主要原因。目前,关于混沌抑制EMI技术的研究主要集中在利用整数阶混沌抑制传导EMI。在此基础上,本文对分数阶混沌在辐射EMI上的抑制以及最优阶次的选取问题展开研究。首先,通过分数阶Lorenz的频谱特性及Lyapunov指数谱分析,优选出1.8阶Lorenz信号为最佳扩频序列;其次,基于变开关频率抑制EMI技术的基本原理,在STM32单片机中分别实现了定频、整数阶、2.7阶、1.8阶Lorenz混沌扩频PWM信号,在一台5 W反激变换器中进行近场辐射实验,证明了1.8阶Lorenz信号对近场磁场辐射抑制作用最强;最后,测得分数阶Lorenz混沌与定频PWM控制下,样机的整机效率相差2%左右,验证了分数阶混沌PWM在辐射EMI抑制性能上的优越性。

The fast on-off switching signal is the main cause of electromagnetic interference(EMI).At present,the research on EMI suppression by chaos mainly focuses on the suppression of conducted EMI by integer-order chaos.On this basis,the suppression by fractional-order chaos on radiated EMI and the selection of optimal order are studied in this paper.First,through the analysis of spectrum characteristics of fractional-order Lorenz and Lyapunov exponent spectrum,1.8-order Lorenz signal is selected as the best spread spectrum series.Second,based on the principle of EMI suppression technology with variable switching frequency,Lorenz chaotic spread spectrum PWM signals with fixed frequency,integer-order,2.7-order and 1.8-order are implemented in an STM32 single chip microcomputer.A near-field radiation experiment was carried out on a 5 W flyback converter,which proved that the 1.8-order Lorenz signal had the strongest suppression effect on the near-field magnetic field radiation.Finally,experimental results showed that the prototype’s overall efficiency was about 2%different when it was under the fractional-order Lorenz Chaos PWM control and constant-frequency PWM control,respectively,which verified the superiority of the fractional-order chaotic PWM in radiated EMI suppression performance.