Modelling and dynamic characterisation of peak-current-mode-controlled superboost converter

The fourth-order converter known as superboost converter is used in the space power systems because of the continuous input and output currents it provides. Peak-current-mode control is applied to reduce its resonant nature as well as to facilitate the overall system design. The small-signal models of such a converter do not exist in the public domain literature and its dynamical features are not known. The modelling based on consistent and easily applicable technique is introduced. The dynamic characterisation shows that the converter may incorporate both resonant right-half-plane zeros and poles, which effectively limits its usage in terms of usable duty ratio and also makes the control design challenging. The theoretical analysis indicates that the usable duty-ratio range can be extended by selecting the values of the inductors properly. Because of the nature of the inductor-current feedback, the open-loop converter has resonant output features but the input is resonant free. The application of the output-voltage feedback recovers, however, the resonant nature at the input boosting the converter sensitivity to input-filter instability. Experimental evidence is provided to validate the theoretical predictions.