Abstract : In this study, nonlinear large-signal model and linear small-signal model of the DC-DC buck- boost converter, which is operating in continuous current mode, has been built using the switching flow- graph (SFG) method. The obtained models can be used either in nonlinear or linear closed loop controller designs for this converter. Switching converters are variable structured systems with linear subsystems and each subsystem can be represented by a flow graph. SFG is built by combining flow graphs of subsystems using switching branches. With the SFG method, nonlinear large-signal model and linear small-signal and steady-state models of a switching circuit can be obtained and the modeling of high-order power electronics circuits can also be done with this method. In order to verify the DC- DC buck-boost converter model made in this study, both the switching circuit and obtained models were simulated using the PSIM software. The simulation results from PSIM has shown that the step responses obtained from the main switching circuit and from the large-signal model of the buck-boost converter overlap. Similarly, the frequency responses of the small-signal model of the buck-boost converter completely match the frequency responses of the switching circuit. These findings confirms that the small-signal model obtained from SFG is verified. Keywords : Switching Flow-Graph, Large-Signal Model, Buck-Boost Converter
