This dissertation presents a new class of power converter topologies that realize galvanicisolation by utilizing active transistor devices instead of conventional transformers. The power converters employ standard switch-mode topologies but isolate the ground connections with the addition of active switches on the ground side of the power path. Compared to transformer isolation, the Active Isolated (AI) converters have reduced size and cost with increased efficiency. A generalized approach is given that is used to create thirty-six new active isolated topologies based on the following basic converters: buck, boost, buck-boost, Cuk, SEPIC, and Zeta. Of these, the buckboost and boost-buck are determined optimum topologies since they achieve pulsating and non-pulsating galvanic isolated conversion with the fewest component count, respectively. The two optimum converters are modeled mathematically and various prototypes are developed that confirms proper galvanic isolation. The concept of unipolar and bipolar isolation is explored and it is found that in many applications, including the application chosen for this work, that unipolar isolation is adequate to provide proper operation and safety for the user. Common-mode transient and steady-state models of the converters are developed and correlated to experimental results. The two optimum converters are used in two applications: PV microinverter and offline AC-DC power supply with fault protection.