An ultra-fast protection scheme for normally-on wide bandgap devices

Here, an ultra-fast protection scheme that is dedicated to depletion-mode (d-mode) devices is proposed. The key to the d-mode device gate drive design is the negative supply and overcurrent protection, due to the safety concern for d-mode devices when a failure happens in power conversion applications. This work evaluates specific requirement of d-mode devices, such as the isolated negative power supply and short-circuit protection. Normally-on d-mode GaN devices have lower on-resistance and minimal dead time in comparison with enhancement-mode (e-mode) GaN devices, which can further reduce the switching loss and conduction loss. Both simulation and experimental verification are conducted in this work to evaluate the performance of the proposed protection scheme. The proposed desaturation scheme can wipe out the overcurrent event within 341 ns. Furthermore, the proposed negative power supply scheme can sustain its output for 60.5 ms, providing sufficient action time for the control unit to isolate the converter.