High Efficiency DC/AC/DC Converter Based on Synchronous Rectifier for Proton Exchange Membrane Fuel Cells

This paper deals with the efficiency improvement of a DC/AC/DC converter used for proton exchange membrane fuel cell (PEMFC) coupling to an electrical vehicle DC bus. The power converter is based on a MOSFET inverter stage, a high frequency planar technology transformer stage and a full bridge diode rectifier output stage. The diode rectifier is a source of losses due to the diode forward voltage, which may be reduced by implementation of synchronous rectifier technology, especially for high output current. Mosfets with low drain-to-source on-resistance are coupled to the diodes to reduce the losses. Control principle of this converter is presented with losses modeling and efficiency study in order to highlight the advantages of the synchronous rectification. Efficiency improvement is quantified from a comparison study with technological choices including silicon carbide (SiC) MOSFET and Schottky diodes. This study points out that the synchronous rectification becomes really relevant for an actual scale-1 application and not for our reduced scale laboratory power converter. Finally, experimental validation of the control is presented with our laboratory test bench. The realization of a scale-1 converter is under study to experimentally validate the advantages of the proposed synchronous rectification.