Patent ID: 7334854
Filing Date: 2008-02-26
Classification: H02P

Abstract:
1. A sensorless start-up method for driving a brushless DC motor, comprising: performing a plurality of detection modes in sequence, such that with respect to each of the detection modes a composite magnetic field generated by a motor current flowing through motor coils points in a different direction, wherein each mode is performed to last for a corresponding detection time such that the motor current gradually increases to a peak value at an end of the corresponding detection time; comparing each of the peak values of the motor currents generated by the detection modes with respect to one another so as to select, from the plurality of detection modes, one detection mode which generates a largest one of the peak values of the motor currents; determining an initial position of a rotor on a basis of a direction of a composite magnetic field generated by the detection mode which generates the largest one of the peak values of the motor currents; and driving the brushless DC motor to start rotating based on the initial position of the rotor, wherein: