Investigation on the Switching Waveforms of GaN Power Devices to Gate Current Profiles

The extended use of Gallium Nitride (GaN) transistors in power applications, such as automotive, industrial and power distribution, leads practitioners and researchers to a review of the classical driving techniques, to meet the different characteristics of such devices compared to traditional ones, such as MOS and IGBT. In particular, the smaller intrinsic capacitances of GaN transistors allow faster switching transitions, thus decreasing the power dissipation during commutations. On the other hand, the higher slope of the switching waveforms drives high frequency resonant circuit that, using slower devices, would not be excited. This paper proposes a technique to obtain an optimal pair of non-oscillating switching waveforms, which exploits time-varying resistances in the power loop. A gate charge driving technique, based on the modulation of the gate current, is exploited for shaping the optimal waveforms by means of the power transistor itself. A simulation analysis was carried out considering two different driving waveforms and studying the sensitivity of ringing as a function of their significant parameters. Such analysis highlights that the optimal switching waveforms can be obtained by means of several driving shapes. Finally, a comparison with the RC snubbered circuit, in terms of efficiency and ringing, is reported to highlight the advantages of the proposed technique.