High side flyback circuit configuration for CM noise cancellation

Abstract

Flyback topologies have advantages in terms of low cost, fewer electrical components, and simple circuit design. Semiconductor devices in the primary and secondary sides are regarded as major EMI noise sources in EMI propagation paths. However, the same transformers under different circuit configurations can bring different noise cancellation effects due to a change of the electric potential distribution in transformer windings as well as the phases of the EMI noise sources in the primary and secondary sides. In this paper, a CM noise cancellation mechanism is investigated. In addition, a flyback topology with high side gate driving in the primary side is proposed to form a CM noise cancellation mechanism. Based on the proposed flyback topology, the capacitor compensation cancellation technique can be applied to lower the electromagnetic interference (EMI) noise level of the designed converter. Finally, the experimental noise spectrums are used to verify the effectiveness of the proposed flyback circuit configuration scheme.