A Critical Assessment of Open-Loop Active Gate Drivers Under Variable Operating Conditions

Active gate drivers have been investigated in power circuits to reduce unwanted over-voltages and over-currents, whilst keeping the transients fast. Indeed, the use of such a kind of driver avoids the triggering of oscillations related to high frequency parasitic resonant circuits, which affect adversely the electro-magnetic interference delivered by power modules. However, in the case of fast power switches, the driver is working in an open-loop manner, and the modulation pattern is fixed. This paper assesses the effects of different operating conditions on the switching waveforms of an AGD-driven power transistor. More precisely, load current, input voltage and temperature variations were investigated on an open-loop active gate driver comprised in a Buck converter. Experimental results suggest that the AGD is no longer effective in damping the unwanted oscillations under a significant change of the operating conditions