Investigation of a Kelvin-Source Connected SMD Silicon MOSFET and its Application in a High Current Full Bridge Synchronous Rectifier

Abstract

Auxiliary loads in an electric vehicle (EV) are in the order of 12–48 V since voltages above 50 V pose risks to the passengers. Power demand on auxiliary loads continues to expand due to increased computation requirements and load profiles. This requires development of power conversion systems that can manage high-currents efficiently. Construction of high current power conversion systems require multiple power switches (MOSFETs) in parallel, which reduce conduction losses. Efficiency can be further improved by incorporating Kelvin-source connections due to improved decoupling of the gate-source (G-S) and drain-source (D-S) loops in a MOSFET. This paper proposes a method to create a Kelvin-source connection in SMD silicon (Si) MOSFET packages with multiple source terminals. A comparison of switching energies between the conventional and proposed methods to highlight the improvements is performed. A 10–14 V/2.8 kW capable full bridge (FB) synchronous rectifier is constructed for application in a DC-DC converter. Parallel connected HDSOP-16 Si MOSFET packages are used to construct this rectifier with the proposed Kelvin-source and imbalances of the root-mean-square (RMS) current ($I_{RMS}$), turn-on ($I_{on}$) and turn-off ($I_{off}$) currents, resultant power loss profile and effect on the design's thermal gradient are studied.