In Depth Analysis of Driving Loss and Driving Power Supply Structure for SiC MOSFETs

Abstract

This paper presents an in-depth analysis of the driving loss for SiC MOSFETs in real applications to help designer determined the power rating of proper gate driving power supplies and select proper gate resistors with enough power rating. A detailed loss estimation method is provided based on the datasheet information. Results verifies that the total driving loss power is determined by driving voltage, device total gate charge and switching frequency. The driving loss distribution analysis with the consideration of the nonlinearity of device gate capacitance is presented which indicates that the loss on turn on and turn off resistors is different, and the loss distribution is related with device working conditions. The power supply implementation for negative voltage driving is also discussed. If two separate voltage sources provide the driving power, each of them must provide real power to drive device gate. If only one voltage source provides the total driving power, a voltage divider circuit or voltage regulate circuit is needed only to provide voltage reference, there is no current through the divider or regulator. No real power is needed from the divider or regulator circuit. Experimental test results are provided to verify all the analysis.