AN898

Electronic motor control for various types of motors represents one of the main applications for MOSFET drivers today. This application note discusses some of the fundamental concepts needed to obtain the proper MOSFET driver for your application.

The bridging element between the motor and MOSFET driver is normally in the form of a power transistor. This can be a bipolar transistor, MOSFET or an Insulated Gate Bipolar Transistor (IGBT). In some small Brushless DC motor or stepper motor applications, the MOSFET driver can be used to directly drive the motor. For this application note, though, we are going to assume that a little more voltage and power capability is needed than what the MOSFET drivers can handle.

The purpose of motor speed control is to control the speed, direction of rotation or position of the motor shaft. This requires that the voltage applied to the motor is modulated in some manner. This is where the power-switching element (bipolar transistor, MOSFET, IGBT) is used. By turning the power-switching elements on and off in a controlled manner, the voltage applied to the motor can be varied in order to vary the speed or position of the motor shaft. Figures 1 through 5 show diagrams of some typical drive configurations for DC Brush, DC Brushless, Stepper, Switch Reluctance and AC Induction motors.