Assessment of Validity Conditions for Black-Box EMI Modelling of DC/DC Converters

Black-box modelling approaches, based on suitable sets of measurements at the output ports of the device, are often exploited for the modelling of power converters to predict their conducted emissions. However, these techniques can be effectively applied only if the device to be modelled can be approximately treated as a linear and time-invariant (LTI) system. This assumption is not necessarily satisfied by every power converter. In order to investigate suitable conditions assuring effectiveness of black-box modelling for a boost converter, this work investigates the role that the converter input capacitors and the functional inductor play in masking the inherent non-linear and time variant behavior of the switching modules, and their impact on the effectiveness of the proposed black-box model. It will be shown that preliminary measurements of the differential mode impedance of the converter can provide useful information on the feasibility of black-box modelling techniques, even in the absence of detailed information on the internal architecture of the converter.