Fast SiC Switching Limits for Pulsed Power Applications

Abstract

Solid-state semiconductor switches are emerging as an attractive choice for the fast switching of compact, repetitive, and pulsed power systems. In particular, the high voltage and fast switching capabilities of SiC MOSFETs are well suited for many applications when appropriately gated. For instance, the turn-on and turn-off characteristics of such devices are strongly dependent on the gate driving circuitry. Traditional commercial gate drivers, typically utilizing push–pull or totem-pole driving topologies, are often not well suited for fast, high current switching with rise times on the order of 10–20 ns, as the driving performance is highly dependent on the combined RLC characteristics of the driving circuitry and the switching device. The proposed gate drive topology utilizes a current-carrying inductor to rapidly charge theMOSFET gate–source capacitance. A high-voltage inductive kick generates the necessary potential to drive the inductor current into the gate through the parasitic gate impedance. As the energy stored in the drive inductor is continuously variable, it can be adjusted such that the gate voltage settles to a lower value, typically 20 V, after the initial kick to prevent excessive gate–source overvoltage. With an inductive drive current of ~23 A, a peak $\text{d}I/\text{d}t$ of 25 kA $\mu \text{s}^{-1}$ was achieved for the tested bare SiC MOSFET die. Additionally, a peak $\text{d}I/\text{d}t$ of 13 kA $\mu \text{s}^{-1}$ was achieved with the TO-247 packaged device.