Focus in this paper is on the galvanically isolated impedance-source dc-dc converter topology. It utilizes both a transformer and a coupled inductor to achieve high step-up of the input voltage without additional components. This approach allows for high step-up of the input voltage while avoiding negative effects from the use of multilayer windings. A steady-state operation principle is described and a mathematical model was derived. An experimental prototype was assembled and tested in the wide input voltage range of I:5 to verify the performance of the converter under study.