The signal flow graph (SFG) nonlinear modeling approach is well known for modeling dc-dc converters and it is a powerful analysis tool for higher order converter systems. Modeling, of several specific fourth-order dc-dc converter circuits have been reported using conventional state-space averaging. Particular emphasis has been given, so far, only to arrive at any of the large, small-signal (SS) and steady-state models but not a generalized one. This paper gives the generalized SFG model of the fourth-order dc-dc converter topology that is useful for generating different types of fourth-order dc-dc converter circuits unified models. Further, it is shown that the deduction of large, SS and steady-state models from these unified SFGs is easy and straightforward. All possible fourth-order dc-dc converter circuits from its generalized topology have been identified and an analysis of a few converter circuits is given here for illustration of the proposed modeling method. Large-signal (LS) models are developed for different topology configurations and are programmed in SIMULINK simulator. LS responses against supply and load disturbances are obtained. Experimental observations are provided to validate the proposed modeling method.