Experimental study of high step-up quasi-Z-source DC-DC converter with synchronous rectification

Quasi-Z-source DC-DC converters have attracted research interest due to their numerous advantages in emerging applications. However, they suffer from relatively low efficiency. This paper presents semiconductor loss breakdown of the quasi-Z-source DC-DC converter to show that conduction losses in semiconductors contribute most to overall losses. Synchronous rectification realized through replacement of diodes with N-channel MOSFETs was proposed to improve the converter efficiency in prior works. Our detailed experimental study of efficiency improvement with synchronous rectification was based on a 250 W prototype. Results were first obtained for replacement of diodes in the primary side only, then in the secondary side only. Finally, a converter that contains only controlled switches was evaluated. Efficiency curves measured were compared with those for the baseline diode-based topology. The experimental study was performed using operating points typical of photovoltaic module integrated converters.