Developed Common Mode Noise Modeling Approach for DC-DC Flyback Converters

Flyback converters are widely used in low power applications due to the simple topology and isolation. However, severe EMI problem occurs because of the rapid switching. Along with the presence of transformer, which makes it difficult to analyze the propagation routes of the noise current. In this letter, a developed common mode noise modeling approach for flyback converters is proposed. Regarding to the transformer model, this investigation not only analyzes the stray capacitance but also takes leakage inductance into consideration, which had been ignored in the previously published models. Besides, the switching voltage waveform is captured and decomposed at time domain. This hypothesis could simplify the following Fourier analysis calculation in frequency domain. Meanwhile, the proposed method could also improve the model accuracy as high frequency ringing has been taken into considerations. The experimental results demonstrated the effectiveness and feasibility of the proposed modeling method.