To control the speed of a BLDC motor, the voltage level applied to the motor’s phases needs to be adjusted. This can be easily done in the same manner as in DC brushed motors, and that is to modulate the voltage with the help of Pulse-Width Modulation (PWM). Thus, the motor speed is directly proportional to the duty cycle of the PWM signal.
The following sections present two switching methods along with their advantages and disadvantages.