Ultrafast Self-Powered Circuit for Gate Driving of Normally On Wide-Bandgap Transistors

Normally
on
wide-bandgap (WBG) devices switch faster and have lower power loss compared to similarly rated normally
off
devices. However, their application in voltage-fed power electronic converters is limited due to the risk of the dc-link short-circuit condition. Several techniques are proposed in the literature to address this problem. However, some drawbacks exist, first, the use of several additional components; second, slow response to the short-circuit condition; and third, increased power losses. To overcome these challenges, this article presents an ultrafast self-powered circuit for gate driving of normally
on
WBG transistors. The proposed circuit provides a sufficient negative voltage to the gate-to-source of the normally
on
device immediately after the converter power-up. Moreover, the proposed circuit does not change the operation of the converter under normal operating conditions. The operating principle and design considerations of the proposed circuit are discussed in detail. Furthermore, SPICE simulations are used to validate the proposed circuit. Finally, an experimental prototype of a normally
on
silicon carbide (SiC) junction field effect transistor (JFET)-based forward converter with the proposed circuit is built to verify the analysis. It is shown experimentally that the response time of the proposed circuit is 2
$\mu$
s during converter power-up.