Analytical Model of DC-DC Converters Based on Switching Impedances and EMI Sources
Résumé
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.