PFC+半桥LLC电路传导共模EMI特性分析与抑制

Analysis and suppression of conducted common mode EMI characteristics of PFC+half-bridge LLC circuit

为了研究开关电源的传导共模电磁干扰(EMI)特性,在分析交错并联PFC+半桥LLC电路传导共模噪声传输机理基础上,提出磁元件可视为共模滤波器的新观点.首先,理论分析磁元件的共模滤波特性,优化设计变压器绕组结构,改善变压器容性分布特性,提高变压器的共模噪声滤波能力.其次,构造反相噪声源补偿抵消原始噪声,提高功率电感共模噪声滤波能力.最后,通过一台音频功放电源样机进行实验验证.实验结果表明,优化磁元件共模EMI滤波特性可有效抑制电路的共模噪声.

In order to study the characteristics of conducted common mode(CM)electromagnetic interference(EMI)of switched mode power supply,based on the analysis of CM noise transmission mechanism of interleaved parallel power factor correction(PFC)and half-bridge LLC circuit,a new viewpoint that magnetic elements can be regarded as CM filter is proposed.This paper analyzes the characteristics of CM filtering of magnetic elements theoretically.Firstly,optimized the winding structure of the transformer and improved the capacitive distribution characteristics of the transformer,the CM noise filtering ability of the transformer can be improved.Secondly,constructed inverse noise sources to compensate and cancelled original noise,the CM noise filtering ability of the power inductor can be improved.Finally,experimental verification is conducted with an audio amplifier power supply prototype.The results show that optimizing the CM electromagnetic interference filtering characteristics of magnetic elements can effectively suppress the CM noise of the circuit.