Loss Model for SiC MOSFET based Power Modules using Synchronous Rectification

Abstract

This paper presents a loss model for SiC MOSFET based power modules without external freewheeling diode. In current electric high perfomance drives for electric vehicles, a low material input, reduced costs, reduced construction volume with maximum efficiency and thus an increased power density play a crucial role. At the same time, the wide bandgap materials should be fully utilised with maximum switching gradients under the given boundary conditions of the power module, the commutation cell design and overall systemic aspects. Absolute maximum ratings and failure in time rates play a important design role in ensuring reliable power modules for the service life of electric vehicles. It is not only the technological leaps in assembly and connection technology that make a decisive contribution here, but also a wide variety of control methods, alternative converter topologies and of course novel semiconductor materials that have an influence on efficiency, thermal properties, volume and thus the use of materials. The maximum efficiency in the present application can be increased by a suitable gate control that leads to synchronous rectification. Due to the multitude of control concepts and the use of a fully variable switching frequency and the influence on the harmonic spectrum, harmonic losses are also analysed and evaluated using a high-speed numerical model. In addition, an analytical loss model is derived and subsequently validated and discussed on the test bench.