The grid drive architecture is another advantage of using the NCD83591 three-phase grid driver. The product realizes constant current grid drive instead of traditional constant voltage grid drive. Constant current drive provides the same switching network (motor phase winding) conversion time, but saves the cost of series grid resistance, and the drive circuit is smaller. It also helps to prevent self conduction without having to connect grid resistors in series. See Figure 2 below for more details. However, the most significant advantage of constant current gate drive is that the IC can sense the actual gate source (Vgs) voltage of the FET it drives. The grid detection function makes the NCD83591 stand out in terms of ease of use because it can realize the benefits of dead time optimization and true cross conduction protection.

    The dead time is usually programmed into MCU to turn off the FET of one phase and then turn on the FET of the other phase. Programming usually allows additional time to ensure that cross conduction does not occur, as the timing changes with temperature, power, and aging. NCD83591 can detect the gate source voltage and turn on the opposite FET in the same phase after the FET is turned off. This eliminates the need to program the dead time of MCU, because the IC will process it, so as to minimize the dead time during pulse width modulation (PWM) and not be affected by delay. This product can also detect the external fault that supplies power to FET. When FET should not be enabled, disable the opposite side FET in the same phase to make corresponding response.