Ferrite Beads Design to Improve Turn-off Characteristics of Cascode GaN HEMTs: An Optimum Design Method

In this article, an optimum ferrite beads design method is proposed to suppress the self-sustained turn-off oscillation of cascode gallium nitride high-electron-mobility transistors (GaN HEMTs). At first, the impacts of gate loop beads and power loop beads on the turn-off oscillation of cascode GaN HEMTs are analyzed. The analysis reveals the weak damping effect of gate loop beads on the turn-off oscillation. Next, an analytical method is proposed to design the power loop beads that can achieve maximum effective damping on the turn-off oscillation. The power loop beads introduce extra stray inductance in the power loop, which can induce high-voltage overshoot. To tackle the problem, an optimum design method is proposed, so that the power loop beads can suppress the oscillation while mitigating the voltage overshoot. The accuracy of the proposed model is validated by the experimental data in the end.