Integrated filtering choke for SMPS with enhanced EMI noise suppression performance

With the widespread application of EMI filters, a method to improve power density has become a main concern in switch mode power supplies. Many previous works have been done for improving the EMI filtering performance of chokes. This article investigates an integrated choke structure that can minimize the leakage magnetic flux, enlarge the DM inductance, and improve the DM noise suppression performance. Compared to discrete EMI filter inductors, the proposed stacked choke scheme can integrate CM and DM chokes into toroidal cores by applying a combination of different types of toroidal cores. The proposed inductor can exhibit better DC magnetic saturation characteristic. Finite Element Method (FEM) simulations, impedance measurement, insertion loss and conducted EMI noise spectrums (150 kHz–30 MHz) are used to validate the accuracy of the theoretical analysis and the proposed equivalent magnetic reluctance models.