Prediction of the resonance effect of the common mode noise of SMPS

The prediction of the common mode (CM) noise resonances of a switching mode power supply (SMPS) is important before prototyping. It requires an appropriate model of the SMPS which considers various frequency-dependent effects. This paper explains the influence of resonances on the conducted CM noise of SMPS by using two models in the frequency domain. The impact of changing parasitic inductance and capacitance values on the resonance operation can be described by these models. The simulation models have been verified using experimental results. The influence of additional grounding on the resonances is described, whereby the simulation and experimental results are in good agreement.