The paper explains the basic ideas of how to model the dynamical properties of switched DC-DC converters by means of the so-called generalized transfer functions (GTFs). Switched DC-DC converters like bust or bust-buck types exhibit some properties of continuous- and discrete-time characters. These systems can be globally modeled by mixed s-z description, utilizing both the Laplace and z-transform operators. Then the resulting line-to-output and control-to-output transfer functions and the corresponding frequency responses can model some system behavior more faithfully than the classical s-domain zeros/poles location, including special effects above Nyquist's frequency