Quasi-steady-state large-signal modelling of DC–DC switching converter: justification and application for varying operating conditions

Quasi-steady-state (QSS) large-signal models are often taken for granted in the analysis and design of DC-DC switching converters, particularly for varying operating conditions. In this study, the premise for the QSS is justified quantitatively for the first time. Based on the QSS, the DC-DC switching converter under varying operating conditions is reduced to the linear time varying systems model. Thereafter, the QSS concept is applied to analysis of frequency-domain properties of the DC-DC switching converters by using three-dimensional Bode plots, which is then utilised to the optimisation of the controller parameters for wide variations of input voltage and load resistance. An experimental prototype of an average-current-mode-controlled boost DC-DC converter is built to verify the analysis and design by both frequency-domain and time-domain measurements.