This paper presents an analysis of operating modes of the step-up DC/DC converter topology aimed for applications with widely changing input voltages. The topology consists of a LC-network coupled with a single phase inverter in the primary side and a full bridge rectifier in the secondary side of a voltage matching transformer. When the input voltage is above the nominal value the converter operates in the buck mode, but when the input voltage level is below the nominal value, the converter operates in the boost mode. The guidelines for LC-network component selection are discussed.