Experimental Study on Gate Drive Influence to the 650 V GaN E-HEMT

The high voltage 650 V GaN E-HEMT shows potential to achieve higher efficiencies and higher switching frequencies than possible with silicon MOSFETs. This paper will study and comprise three different gate drives - isolated negative voltage gate drive (INGD), isolated zero voltage gate drive (IZGD), bootstrap gate drive (BSGD) for 650 V GaN E-HEMT (GS66508P from GanSystems). The following conclusions can be obtained: 1) INGD has fastest switching speed and lowest switching loss. Meanwhile, INGD has the best performance for the gs-resonation suppression. 2) IZGD works mediocre but is simpler than INGD. 3) When the gate resistor is small, BSGD has the similar switching performance as IZGD. However, when the gate resistor increases over 20 Omega, a serious false turnoff will occur during the turn-on process caused by cross-talk. 4) The voltage rise time will increase to about 100 ns while the load current is small for the non-linear junction capacitance at turn-off. Hence, an extra short-through losses will occur if the dead time is not enough at this condition. Furthermore, the critical dead time is found when there is no short through and the dead time is smallest. These results can instruct the 650V GaN E-HEMT gate drive design.