Analysing the Crosstalk Effect of SiC MOSFETs in Half-Bridge Arrangements

The faster switching transitions enabled by silicon carbide (SiC) devices have allowed converters to operate at much higher switching frequencies without sacrificing efficiency. Unfortunately, faster switching has also greatly increased the impact that previously negligible parasitic effects have on the converter. One of these is the crosstalk effect which relates to when switching one device in a half-bridge causes the other device's gate-to-source voltage to vary even when its gate drive signal is fixed. This effect can degrade the converter's efficiency, EMI compliance and the device and converter reliability. This paper examines the influence that the gate resistance and load current has on the crosstalk effect during the turn-off and turn-on transitions. Simulation and experimental results show that when one device is being turned-off, the crosstalk effect on the complementary device is significantly affected by the load current, however it has little to no impact during turn-on. Experiments confirm that an excessive negative voltage spike on the complementary device during the active device's turn-off is more likely to be a detriment to the circuit than a positive spike on the complementary device during turn-on. Also evident from the experiments was that the subsequent ringing during turn-on was larger than the initial overshoot caused by the crosstalk effect for low values of gate resistance.