Patent ID: 7683560

Claim:
A brushless DC motor system comprising a motor and a drive circuit, the motor having a stator and a rotor, the rotor being supported for rotation about an axis, the stator having a plurality of field poles including coils distributed about the rotor axis, the rotor having a permanent magnet arranged to interact with the field poles, the drive circuit including a microcontroller, conductors for communicating the back EMF in the field coils to the microcontroller, an electronic switch associated with each field coil for controlling DC current through the associated coil, the drive circuit including elements enabling the microcontroller to selectively operate the switches, the microcontroller being programmed to monitor the back EMF of the coils, determine the approximate angular position of the rotor from the back EMF data, and operate the electronic switches at appropriate times in successive revolutions of the rotor on the basis of its determination of the approximate rotor position.