Hybrid Passive Cancelation Method for Reducing Common-Mode Noise in Isolated Power Converters

The shielding technique is an effective method for reducing the common-mode (CM) electromagnetic interference in an isolated power converter. However, the interwinding capacitance between the shielding layer and its adjacent winding provides the path for CM noise current. This CM noise current can be suppressed by making the averaged electric potential (AEP) of the shielding layer and its adjacent winding be equal. In this article, a balancing winding is introduced to be connected with the shielding layer for adjusting the AEP of the shielding layer to be equal to that of its adjacent winding and, thus, canceling the CM noise current. Furthermore, the hybrid passive cancelation (HPC) method is proposed in which the balancing winding is reused as the compensation winding to generate the compensation voltage for canceling the noise current flowing through the parasitic capacitance between the high dv/dt node in the primary circuit and protective earth. The proposed shielding technique with balancing winding and the HPC method are verified by the experimental results.

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