TIDUF28 November 2023
Figure 4-5 outlines the turn-on and turn-off propagation delay from the MCU complementary PWM signal with 150-ns dead time to the phase U switch node. The turn-off time instant of the bottom GaN-FET can be identified, when the phase voltage U changes from 0 V to around –4 V. Then the bottom FET is conducting in the 3rd quadrant mode with a drain-to-source voltage VDS of around –4 V, as indicated with the dashed line. The effective turn-off delay is 165 ns. The effective turn-on delay of the top FET (hard switching) is around 135 ns. The effective dead time is 120 ns due to the difference in the turn-on and turn-off delay, as shown below.