計及寄生參數效應的鐵氧體共模扼流圈二端口網絡的建立:共模扼流圈的寄生參數在高頻時對濾波器的性能有重要影響，準確建立其對應的差模和共模二端口模型
對設計電磁兼容濾波器以及改善其性能具有重要意義。對差模電路，通過建立靜電場模型并計算匝間部分電容可得到等效寄生電容，進而獲得二端口內各支路的電容參數；測量其諧振頻率，可得到差模漏電感。對共模電路，通過建立時諧磁場模型，采用類比有限元法可求解磁芯等效電感和電阻；測量其諧振頻率，可得到考慮環境因素后的寄生電容。測量扼流圈二端口在輸入、輸出匹配狀態下的散射參數，間接得到濾波器差、共模電路對應的二端口網絡各支路的阻抗或導納。散射參數法的測試與“諧振頻率＋有限元法”建立的阻抗取得較好地一致，說明模型的準確性和測試方法的合理性。
Abstract: Because of the effects of parasitic couplings of choke playing important roles in the high frequency
performance of EMI filters, it is necessary to construct the 2-port network models corresponding to the CM and DM circuits
for designing EMI filters and improving their performances. For the equivalent DM circuit, the partial capacitances of turn to turn and more the equivalent parasitic capacitance can be calculated by setting up the electrostatic model. Further, capacitive parameters in each branches of 2-port for CM are obtained. The DM leakage inductance can be achieved if the resonant frequency is measured. For the equivalent CM circuit, equivalent magnetic core resistance and inductance can be solved using analogical finite element method (FEM) by setting up the model of harmonic magnetic field. The parasitic capacitance considering the environmental factor can be achieved if the resonant frequency is measured. To measure the scattering parameters under the input and output matching state for choke, the branch impedances or admittances of DM and CM models are achieved indirectly. The impedances of branches using scattering parameters measurement are in good agreement with the ones using ‘resonant frequency adding FEM’. It was demonstrated that the veracity of setting models and the rationality of measuring method.
關鍵詞﹕扼流圈 差模電路 共模電路 有限元法 散射參數 諧振頻率
Keywords: Choke, differential model circuit; common model circuit; finite element method (FEM); scattering
parameters; resonant frequency