A method and circuit are presented for operating a polyphase dc motor in which substantially sinusoidal drive voltages are applied to the windings of the motor in predetermined phases. Zero crossings of currents flowing in respective windings of the motor are detected, and phases of the drive voltages...http://www.google.ca/patents/US6236174?utm_source=gb-gplus-sharePatent US6236174 - Method and apparatus for driving a polyphase, brushless DC motor
