Transformer Structure of Bifilar Primary Winding with Advanced Common Mode Noise Attenuation Performance for Isolated DC-DC Converters

The transformer is one of the main common mode (CM) noise propagation paths in isolated DC-DC converters. The impedances of the CM path of a transformer will transfer from capacitance to inductance with frequency increasing. Firstly, this paper investigates the source of the CM inductance and the feature of the magnetic field contributing to the CM inductance. Then, a transformer structure of bifilar primary winding with advanced CM noise attenuation performance is proposed. Finally, the effectiveness and advantages of the proposed transformer on CM noise attenuation are verified by experiments.