Patent ID: 7259531

Claim:
An apparatus for controlling the speed of a brushless DC motor, the apparatus comprising: a Hall sensor arranged to output a high logic level when the Hall sensor detects a proximity of a magnetic north rotor section of the brushless DC motor, and output a low logic level when the Hall sensor detects a proximity of a magnetic south rotor section of the brushless DC motor; a first switch arranged to apply voltage on a first winding to produce magnetic north on vertical stator poles of the brushless DC motor and magnetic south on horizontal stator poles of the brushless DC motor; a second switch arranged to apply voltage on a second winding to produce magnetic south on the vertical stator poles and magnetic north on the horizontal stator poles; a turn-on control circuit arranged to generate a conduction time reduction after each output transition of the Hall sensor; wherein when the output transition of the Hall sensor is from the low logic level to the high logic level, the first switch is turned on to apply voltage on the first phase winding with a turn-on delay of the conduction time, a turn-off advance of the conduction time or a combination of turn-on delay and turn-off advance of the conduction time; and when the output transition of the Hall sensor is from the high logic level to the low logic level, the second switch is turned on to apply voltage on the second phase winding with the turn-on delay of the conduction time, the turn-off advance of the conduction time, or the combination of turn-on delay and turn-off advance of the conduction time.