Patent ID: 8294397

Claim:
A sensorless starting control method for a brushless direct current (BLDC) motor, comprising: a first rotor-positioning step configured to position a rotor in a first position by operating a coil unit in a first excitation state; a second rotor-positioning step configured to operate the coil unit in a second excitation state such that the rotor rotates from the first position to a second position; an open-looped starting step configured to excite a plurality of coils of the coil unit in sequence so as to drive the rotor to rotate in a predetermined direction, wherein the coil unit generates a back electromotive force (EMF) when the rotor rotates in the predetermined direction; and a close-looped operation step configured to control the BLDC motor to attain a predetermined rotational seed via a feedback of the back EMF, wherein the rotor comprises a plurality of rotor magnetic poles, the angle of the rotor rotating from the first position to the second position is not larger than an included angle of a single one of the rotor magnetic poles, and the included angle of the single one of the rotor magnetic poles is obtained by dividing 360 degrees by the number of the rotor magnetic poles, wherein adjacent two of the plurality of rotor magnetic poles with different magnetic poles are magnetically attracted by an N-pole magnetic field generated by one coil U 1 of the plurality of coils and an S-pole magnetic field generated by one coil V 1 of the plurality of coils during the first rotor-positioning step, so as to drive the rotor to rotate by a small angle until a rotor magnetic pole border where the adjacent two of the plurality of rotor magnetic poles border each other is aligned with the first position, and the first position is located between two stator magnetic poles respectively wound with the coils U 1 and V 1 .