Input filter interactions in current-mode controlled converters-a unified analysis approach

A unified analysis approach in assessing the effect of an input filter on the performance of a current-mode controlled converter is presented. The analysis method is based on the use of two-port unterminated modeling technique. The describing formulas to assess the input-filter effect are presented based on the transfer functions of direct-duty-ratio control with modifications caused by the effect of inductor-current feedback in peak-current control. The analysis shows that the behavior of input impedance explains the phenomena noticed earlier.