Modelling and measurement of high-frequency conducted electromagnetic interference in DC-DC converters

Abstract

Conducted electromagnetic compatibility (EMC) noise qualification tests are normally carried out after a prototype has been designed, built and tested and the process is repeated in the event of non-compliance. The ability to determine compliance with electromagnetic interference (EMI) standards at the design stage is therefore desirable. This study will present conducted EMC noise modelling and measurement techniques, yielding simulated and measurement noise results accurate enough to serve as a prequalification test at the design and prototyping stages, respectively. Accurate models of the power feed line connecting the line impedance stabilisation network to the device under test (converter), including the load are developed. Predictive conducted EMC modelling is accomplished using detailed active level 3 SPICE-based models, creating a real-time circuit model consisting of a complete converter in its operational state, without the need to separate into equivalent models. Effects of the power feed-line length on EMI noise measurements are investigated as currently available literature has not dealt adequately with this issue. The modelling and measurements are performed using software and instruments available in a development laboratory.