The Characteristics of Planar EMI Filter with Bi-Ground Layers Considering Impedance Mismatching

摘要

Planar electromagnetic interference (EMI) filter has significant engineering significance to power electronic system integration and miniaturization. However, the value of differential mode capacitance cannot meet the demand of noise suppression because of the size limit of ceramics. In this case, the EMI filter of novel multilayers is recommended to address this issue. A novel integrated structure of EMI filter based on multilayer ceramic is proposed in this study. The inductance and capacitance of the new structure can be designed separately, which is an advantage in manufacturing. Insertion loss is measured more closely to the actual situation in this study, which is different from the condition where source and load impedances are both 50 Omega. In the process of designing a novel EMI filter, noise impedance is considered. Moreover, the prototype is created and applied to a small switching power supply, which verifies the effectiveness of the developed EMI filter.