The power stage drive circuit of BLDC usually consists of six N-channel power MOS tubes to form a three-phase full bridge. The six MOS tubes are divided into two groups, with three high-side MOS connected to the positive power supply (VBus) and three low-side MOS connected to the negative power supply. By controlling the MOS tube on and off, the current is distributed in the motor winding and the motor is driven to run.
    When a single NMOS is turned on, it needs to provide an instant current to charge the internal parasitic capacitor. When the gate-source voltage (VGS) reaches the threshold, the MOS tube turns on. After the MOS tube is opened, it is necessary to maintain the VGS to keep the on-state, so that the current provides power to the motor.
    The low side MOS tube source (S) is connected to the negative terminal of the power supply, the gate source voltage is easy to meet, and the drive is simple. The source pole of the high-edge MOS tube is connected to the motor phase line, and its voltage is in dynamic change at all times, and there are many uncertain factors. In order to turn on the high-edge MOS tube, it is necessary to use the bootstrap circuit to provide the appropriate gate voltage, which involves complex circuit design and signal processing, and is difficult to drive.

    Under normal circumstances, the internal resistance of MOS tube decreases with the increase of VGS. When the VGS is at 10-15V, the MOS tube can achieve the minimum on-resistance (RDSON). At this time, the energy loss when the current is transmitted in the circuit is greatly reduced, thus improving the efficiency of the entire drive circuit.
    By controlling the on-off of six MOS tubes, the controller realizes BLDC commutation, adjusts the motor speed and steering, and meets different application requirements, such as acceleration and deceleration of electric vehicles and energy recovery. If the motor is running, the MOS drive circuit can detect and cut off the circuit, protect the controller and the motor, and ensure the operation of the system.