Mechanism Analysis, Modeling and Suppression of Common-Mode Interference of Interleaved LLC Resonant Converter With Integrated Magnetics

The interleaved parallel technique and magnetic integration technique can effectively improve power density of high-current LLC resonant converter. However, its common-mode (CM) noise mechanism and suppression are complicated due to the integration of multiple transformers (IMTs) sharing one common core in the interleaved multiplexing. The CM noise mechanism of the IMTs is analyzed, and the structural capacitance model and common-mode noise model of the IMTs are established. The model reveals that there exists electric field coupling between the any two windings through the common core of the IMTs. Then the CM noise propagation mechanism of interleaved LLC resonant converter with IMTs is investigated, and the simplified CM noise model of the IMTs is further developed. Based on the simplified model, the two suppression methods of the optimal balance capacitance, and the grounding both of shielding layer and transformer magnetic core are proposed. The experiments in a 3 kW high power density server power supply shows that the proposed suppression methods mitigate CM noise more effectively, and can reduce the CM inductor volume greatly, while loss improvement can be negligible. The experiments validates the IMTs noise mechanism, CM noise model, the simplified model, and the proposed suppression methods. The research will be beneficial to develop high power density and high current AI server power supply.