| Abstract |
Switch-mode power converters (SMPCs) are known as one of the greatest sources of electromagnetic
interference (EMI) in electronic equipments. In order to comply with the strict electromagnetic
compatibility (EMC) requirements, an EMI filter is needed at the input of a SMPC. The design of EMI
filters aims at achieving required insertion loss (IL), i.e. attenuation of the power of the unwanted
electromagnetic emissions (EME) from a switch-mode dc-dc converter. However, the EMI filter affects
converter’s dynamics.
This paper discusses how chain parameters can be used to calculate the IL provided by converter’s input
filter and also in the input system stability analysis.
The stability analysis shows that relatively small resistances in series with the capacitor and inductor,
which are closest to SMPC’s input, can compensate the effect of converter’s negative input impedance.
Chain parameters are very useful in IL calculations as well. Comparison between LC- and p-filter shows
that if dc power line’s impedance is know to be very low, LC-filter will perform as p-filter. With
unknown or high dc source impedance p-configuration should be used. |
