Ripple base signal flow graph modelling of DC-DC switching converters

A new ripple base signal flow graph (R-SFG) modelling method was proposed to accurately model and analyse a family of switching DC-DC converter. The performance of some DC-DC converters such as single-inductor multi-output converters is dependent on inductor current ripples. This makes the conventional modelling methods cannot fully predict the overall behaviour of converter. From this family and in this study, a single-inductor dual-output (SIDO) boost/boost converter has been modelled based on proposed R-SFG method. The simplicity and systematic procedure presented in this work showed that the R-SFG could be a good alternative for modelling switching converter with complicated structures and with high inductor current ripple. In the new R-SFG method, the effects of inductor current ripple have been considered to develop the conventional signal flow graph modelling method. In this work, a comparative study between two modelling methods has been carried out in a SIDO converter. A step-by-step direct mathematical manipulation was used to calculate the DC-DC transfer function of SIDO converter. The experimental results were included to show the validity of the obtained models. The experimental results showed that the maximum R-SFG modelling error was about 5% over the wide range of inductor current ripple.