An Active Gate Driver to Enhance SiC-MOS Performance Utilising a Controlled Parasitic Turn-On Effect

Inhalt:
Parasitic Turn-On (PTO) has been shown to slow the passive diode’s recovery speed, thereby enabling a reduction in gate resistance during turn-on of the complementary active switch. This reduction decreases the combined active turn-on and passive diode turn-off switching losses. This paper quantitatively evaluates this phenomenon and further demonstrates how Active Gate Drivers (AGDs) applied to the passive switch can enhance the performance through a switching-current-dependent control strategy. The proposed approach utilises the conventional negative gate driving voltage at low switching currents until the diode turn-off overvoltage approaches its permissible limit. For higher switching currents, the strategy transitions to a less negative gate driving voltage, intentionally triggering PTO. This mechanism reduces the reverse recovery current gradient, mitigates overvoltage, and enables the use of lower gate resistance during turn-on, thereby minimising total switching losses compared to traditional methods. The achievable switching loss reductions are calculated for various scenarios during an electric vehicle driving cycle. Furthermore, this work explores multiple AGD topologies capable of generating the required negative gate voltages.