Average current controlled switching regulators with cascade boost converters

A controller design methodology for an n-stage cascade boost converter is given using average current-mode control. This class of converters has n-LC filters; thus, it will exhibit 2n-order characteristic dynamics. The proposed scheme employs the inductor current of the input stage and the capacitor voltage of the output stage; thus, there are (n−1) capacitor voltages and (n−1) inductor currents that are not used for feedback purposes. The sensed current can also be used for one-cycle overload protection; therefore the full benefits of current-mode control are maintained. Owing to the fact that this scheme uses only a reduced set of variables for feedback, it is important to study the internal stability. The results given in this study allow the designer to easily pinpoint the control circuit parameters that optimise the converter's performance. Experimental results are given for a 100 W switching regulator where the robustness of the proposed controller is tested under changes in the input voltage and output load.