Low Common-Mode Noise LLC Resonant Converter With Static-Point-Connected Transformer

A new structure of the transformer and its winding layout are proposed to reduce the common-mode (CM) noise generated from the planar transformer (PT). In the proposed converter, two half-bridge LLC resonant converters are connected in parallel on the primary side, and the secondary side of them is connected in series. The proposed converter can be utilized for the medium-to-high power applications due to the full-bridge structure of the primary side. For each transformer, one of the terminals is connected to the static point, which has zero dv/dt characteristic. Thus, the primary-side layer can have the same dv/dt characteristics with the secondary-side layer. By adjacently locating the primary and secondary layers, which have the same dv/dt characteristic, the CM current and noise generated from PT can be significantly reduced. Therefore, the proposed converter can achieve a high power density by reducing the size of the electromagnetic interference filter.