A temperature-dependent electrothermal MOSFET model for calculating its current loadability

A developed temperature-dependent electrothermal model consists of a temperature dependent MOSFET model and a temperature independent model of the MOSFET thermal system. The temperature dependent MOSFET parameters are the channel charge carriers mobility, drift area resistance and threshold voltage. Calculated at each moment are voltage, current, losses (including conduction losses, built-in diode losses and switching losses) and the virtual junction temperature. During the simulation, the MOSFET temperature dependent parameters depended on instantaneous virtual junction temperature. The electrothermal model is based on catalog data about MOSFET. It gives the designer highly precise information necessary for electrical and thermal design of electronic circuits, especially of electronic power converters in transient and stationary states. The temperature dependent electrothermal model was developed using an IsSpice4 software program. The existing model of the signal MOSFET was expanded with the temperature dependence of parameters and supplemented with an electrical model of its thermal system. First, the model was checked by simulating catalog characteristics and next by comparing a simulated time course for losses and for virtual junction temperature with a measured time course of losses and virtual junction temperature of the MOSFET in one chopper measuring the time course of virtual junction temperature required designing a special measuring equipment.