A stacked common mode inductor with small external magnetic field susceptibility, low magnetic field emission and high differential mode inductance

This paper proposes a stacked common-mode (CM) inductor for electromagnetic interference (EMI) attenuation. The proposed stacked CM inductor consists of two CM inductors with identical cores and the same number of winding turns but with opposite winding directions. The proposed stacked CM inductor has three advantages. First, it is much less susceptible to external magnetic field interference than conventional CM inductors. This suppresses the EMI due to the near-magnetic-field coupling to the CM inductor. Second, the proposed winding structure effectively increases the leakage inductance of the CM inductor which enhances its ability to suppress differential-mode (DM) noise. Third, the magnetic field generated by the DM current in the stacked CM inductor is partially canceled outside of the inductor. As a result, the stacked CM inductor has lower magnetic field emission than that of a conventional CM inductor. Simulation and experimental results validate the advantages of the proposed CM inductor, which show the proposed technique greatly improves the performance of CM inductors.