Concept of Enabling Over-Current Capability of Silicon-Carbide-Based Power Converters with Gate Voltage Augmentation

Various methods have been discussed in the literature regarding enabling the over-current (OC) capability of silicon carbide (SiC) MOSFETs. SiC MOSFETs can operate at up to 250 °C without failure. One of their features is to permit transient operation at elevated temperatures. This is possible if the stress on the gate oxide and packaging can be kept to a level that can be handled. This paper, instead, investigates the potential of enabling the OC capability of SiC MOSFETs by modifying the gate-source voltage. Since the on-state resistance ( R D S ( o n ) ) of SiC MOSFETs decreases with an increase in the gate voltage ( V G S ), the conduction losses can be decreased by increasing the V G S . Experiments and simulations have been performed to predict the R D S ( o n ) with the increase in V G S . It is found that the simulation models provided by manufacturers can be used to predict R D S ( o n ) accurately even outside the specifications, hence facilitating the precise estimation of conduction losses. It is also concluded that V G S can be increased during OCs in order to keep the conduction losses within the safety limits. A simple concept for implementing this function on a gate driver is also proposed with the additional functionality of increasing the V G S during OC by measuring the on-state voltage of the MOSFET.