Novel techniques to suppress the common mode EMI noise in class II off-line SMPS applications

A novel Y-cap. connection structure for Class II offline SMPS applications is proposed to suppress the common mode (CM) noise. With proposed concept, the size of the CM choke can be greatly reduced while satisfying the EMC standard. Furthermore, the inner shielding layer inside power transformer which is normally a must in product design to comply with the EMC standards can be eliminated for higher conversion efficiency and easier manufacturing. Successful implementation of this concept leads to the smallest 65W adaptor in the world.