Active Switching with SiC MOSFETs

The work in this paper presents a methodology to overcome the coupled nature of dv/dt and di/dt to gate drive resistance and stray commutation inductance for a SiC MOSFET. The SiC MOSFET exhibits almost ideal switching behavior, corresponding closely to the simplified device equations. Designing a circuit however to a give specific di/dt and dv/dt, particularly under varying load conditions, becomes difficult and tends to proceed by trial and error. By adding feedback control and using a gate current drive rather than a simple resistor, these relationships can be decoupled and designs maybe improved. This paper presents both Active Voltage Control and Active Current Control using a gate current drive and feedback circuits, and presents new experimental results for a state of the art 900V, 35A SiC MOSFET. On board measurements are used throughout. It is demonstrated that near ideal switching behavior can be achieved, which may be modified at will within the bounds of the gate drive capability and stability constraints.