Analytical model of DC-DC converters based on switching impedances and EMI sources

Since studies are intended to be used to predict the compliance with Electromagnetic standards, an accurate computing of a common and differential mode conducted noise is necessary. Nowadays, the modern networks-as the car's network supplying many electrical actuators-include many power converters to manage efficiently the power transfer, but also a long cable (conductors), which creates new issues (interaction between cable and converter's noise sources), and therefore the EMC study becomes more complex. For this reason, in this paper we propose an analytical model to compute a common mode equivalent conducted noise sources, inside the network, at any site of the DC-network (all along the cable). Firstly, noise sources modelling the EMC behaviour of converters connected to the DC-network, are extracted and identified in both frequency and time domains. Therefore, converter's electric equations modelling its behaviour are performed by defining a mathematical switching function. The model is tested with time domain simulations and validated by experimental measurements. Secondly, the extracted converter's model, based on equivalent noise sources, is used to predict the conducted noise inside a defined network, at any location of the cable (network). The process of the network's modelling is built by using the Transmission Line theory (TL) of lossless bifilar lines. This network's model is crucial for EMC analysis, to evaluate the interaction degree between the noise sources and cable parameters. Finally, the network's model is tested by a time domain simulation (LTSpice), and validated by an experimental setup.