EMI modeling of buck converter using a generalized terminal model

A generalized terminal model was proposed earlier for predicting electromagnetic interference (EMI) at the input of a boost converter. The results of conducted emissions (CE) were found to match well with the measurements up to 100 MHz. The work presented here extends this technique to model a buck converter. The buck converter presents more difficulties in extraction of a linear model due to significant switched-impedance behavior at its input. Hence, a buck converter was chosen to confirm the versatility of the proposed generalized terminal modeling technique. Measured and predicted results of CE matched well within about 6 dB at most frequencies up to 100 MHz. Guidelines are proposed to achieve optimum accuracy when using this approach for modeling buck converters. Finally, causes of inaccuracies in EMI modeling with the measurement based series-and-shunt impedance insertion method are demonstrated.