Patent ID: 7514888

Claim:
A method of determining the position of a DC brushless motor's permanent magnet rotor which moves in response to the application of an excitation voltage across the motor's stator coil, comprising: applying an excitation voltage across at least one stator coil for a predetermined ON-time period; deactivating said excitation voltage at the end of said predetermined ON-time period; monitoring the voltage (V EMF ) across said at least one stator coil generated by the electro-motive force (EMF) induced in said at least one stator coil by said rotor when said excitation voltage is deactivated, said at least one stator coil connected in a full-bridge configuration; and detecting when V EMF changes polarity while said excitation voltage is deactivated, such that said change of polarity indicates when said motor rotor has rotated a known distance with respect to its position at the time of its previous change of polarity.