An Integrated EMI Choke for Differential Mode Noise and Common Mode Noise Suppression

This paper presents a novel integration approach for the EMI choke. The low permeability differential mode (DM) choke is placed within the open window of the common mode (CM) choke. Both chokes share the same winding structure. With the proposed approach, the window area of the toroid core is fully utilized and high DM inductance can be achieved. The small signal measurement was first carried out to demonstrate the design concept and the symmetry of the proposed structure. Then the large signal experimental results verified the attenuation characteristics as well as the thermal performance.