Input filter influence on the control stability of DC/DC converters

Today, almost all converters have an input filter to control EMI/EMC. For most, the sizing of the filter is depending on the required attenuation from the applicable standard. For some standard that leads to very large attenuation, the input filter has more attenuation than the output filter. This study shows the interaction of the input filter and the converter regulation on both aspects of the equations and the physical understanding. We also propose a method to stabilize the whole system (filter, converter and control) without over sizing. Three basic DC/DC converter structures (the buck, the boost and the buck-boost converters) with and without transformer are studied in both modes: discontinuous current mode and continuous current mode.