Analytical loss model of power MOSFET

TLDR

Ringing is routinely observed in switching power supplies but is ignored by traditional loss models. This study proposes an accurate analytical model to calculate MOSFET power loss and to analyze ringing loss with clear physical meaning. The model incorporates capacitor nonlinearity and parasitic inductances, and its predictions are validated by experimental measurements. The model accurately predicts circuit power loss, with simulation results matching experiments even at 2‑MHz switching frequency.

Abstract

An accurate analytical model is proposed in this paper to calculate the power loss of a metal-oxide semiconductor field-effect transistor. The nonlinearity of the capacitors of the devices and the parasitic inductance in the circuit, such as the source inductor shared by the power stage and driver loop, the drain inductor, etc., are considered in the model. In addition, the ringing is always observed in the switching power supply, which is ignored in the traditional loss model. In this paper, the ringing loss is analyzed in a simple way with a clear physical meaning. Based on this model, the circuit power loss could be accurately predicted. Experimental results are provided to verify the model. The simulation results match the experimental results very well, even at 2-MHz switching frequency.