The general overview of used control technique is
shown in Fig.2 and consist of the following blocks: threephase
BLDC motor, BLDC power stage (driver-bridge),
PWM and switch converter, position detection, speed
measurement, PC I/O card, DCM controller.
The BLDC motors are a type of synchronous motor.
This means the magnetic field generated by the stator and
the magnetic field generated by the rotor rotate at the
same frequency. BLDC motors do not experience the
“slip” that is normally seen in induction motors. Unlike a
brushed DC motor, the commutation of a BLDC motor is
controlled electronically. To rotate the BLDC motor, the
stator windings should be energized in a sequence. It is
important to know the rotor position in order to
understand which winding will be energized following the
energizing sequence. In our case, the rotor position is
sensed using Hall sensors embedded into the stator. Based
on the combination of these three Hall sensor signals, the
exact sequence of commutation can be determined
(Fig.1).