Boost变换器共模噪声反相补偿法的高频特性分析与改善

High-frequency Behaviors Analysis and Improvement of Anti-phase Compensation Method for CM EMI Noise Suppression in Boost Converters

反相绕组法是Boost变换器传导共模噪声抑制的一个有效技术,但绕组的寄生参数在高频段对噪声抑制能力有重要影响。通过对计及反相绕组寄生参数的Boost变换器共模等效模型的深入分析,明确寄生参数中的漏感、副边分布电容与补偿电容的串联谐振频率是影响噪声抑制能力的关键因素。优化寄生参数,提高谐振频率是扩大有效频率带宽,改善噪声抑制效果的有效措施。在此基础上,提出以反相1 1变压器代替反相绕组的新方法,该方法可以极大地减小漏感和副边分布电容,提高谐振频率。实验结果表明,反相变压器法较反相绕组法的有效频率带宽及高频段的共模噪声抑制能力得到明显提高。

Anti：phase winding is an effective method to suppress the CM EMI conducted noise in Boost converter. However the parasitic parameter of the anti-phase winding has critical effect on high frequency ranges. By the detail analysis of the CM EMI equivalent model of Boost converter considering the parasitic parameter of the anti-phase winding, the key factor is confirmed which is due to the serial resonant between the leakage inductance and stray capacitance of secondary winding plus the compensated balance capacitance, Optimizing the parasitic parameters will bring the benefit to increase the resonant frequency and expend the effective bandwidth in CM noise suppression. Based on the theoretical analysis, a novel method is also proposed which use an anti-phase 1：1 transformer, instead of anti-phase winding. With the new method the leakage inductance and the stray capacitance can be controlled to decrease greatly, resulting in great increase of effective bandwidth. The result of experiment shows that a much higher effective bandwidth and then the much great CM noise suppression in higher frequency ranges can be obtained using the anti-phase transformer than that using the anti-phase winding.