Modeling of the Power Losses due to Coss in SJ MOSFETs Submitted to ZVS: Identification of the Passive Parameters by a Genetic Algorithm

Super junction (SJ) MOSFET is a well-established device in high-density and high frequency power conversion. Soft-switching techniques are usually adopted at high frequency to reduce the power losses into the power devices. However, new challenging issues appear always when the paradigm changes. In fact, unexpected heating and efficiency reduction due to $\boldsymbol{C}_{\mathbf{oss}}$ related phenomena are key issues to be faced when SJ MOSFETs are adopted in high-frequency soft-switching applications. The phenomenon appears when large voltage transients are applied to the drain-source terminals as in the case of soft-switching applications. This paper provides analysis of the electrical hysteresis, and proposes an equivalent circuit that may model such a behavior in case of SJ MOSFETs. The loss model of $\boldsymbol{C}_{\mathbf{oss}}$ has been validated by comparing the measurements with the simulation runs performed by means of the Simulink package.