Low Common-Mode Noise Structure Based on Half-Bridge LLC Converter for Medium and High Power Applications

A new structure and a winding layout of the transformer are proposed to reduce the common-mode (CM) noise of the converter for medium-to-high power applications. The proposed converter is composed of two half-bridge LLC resonant converters. The primary side of transformers are connected in parallel, and the secondary side of transformers are connected in series. In transformers, two layers having the same dv/dt characteristic are located adjacently to minimize CM current through the parasitic capacitor between two layers. One of the terminals of the transformer is connected to the ground or input voltage whose dv/dt characteristic is zero. Thus, there are secondary layers having the same dv/dt characteristic compared with the primary layers. Thus, the proposed converter can minimize the CM noise in transformer, and it can achieve high power density by reducing the size of EMI filter.