Common-Mode Noise Modeling and Reduction for Multi-output dual-switch flyback converter

Flyback converters are widely used in electronic products. At present, power electronics technology is developing in high frequency and miniaturization, arousing much attention on EMI issues. This paper uses an actual multi-output dual-switch flyback converter as an example to analyze its CM characteristic. Firstly, the displacement current expression of a transformer with both single-layer primary and secondary windings is derived, and the lumped model of a four-capacitance multi-winding transformer with two secondary grounds is further established. A CM noise cancellation capacitor is proposed to generate a reverse decimation current to cancel the CM noise current, which helps derive the cancellation capacitor expression. The experimental results verified the effectiveness of the CM model and CM noise reduction method of the flyback converter.