Patent ID: 8106612

Claim:
A brushless motor control device that drives a brushless motor including a stator having coils of three phases U, V, and W and a neutral line, and a sub coil provided in any one phase of the phases U, V, and W, for detecting a voltage induced in the coil of the one phase, the brushless motor control device carrying out a conduction control function, for the respective phase coils of the brushless motor, that performs a 120° conduction when a rotation speed of the brushless motor is lower than or equal to a predetermined rotation speed, and that performs a 180° conduction when the rotation speed is higher than or equal to the predetermined rotation speed, the brushless motor control device comprising: a current rise detecting circuit that, when the brushless motor is in a stop state, sequentially selects coils of two phases among the coils of the respective phases U, V, and W, applies positive and negative predetermined direct current voltages between the selected coils of the two phases, and detect a value of the electric current flowing to the selected coils of the two phases; a rotor stop position detecting unit that determines a rotor stop position of the brushless motor based on information of the value of the electric current flowing to the respective coils which is detected by the current rise detecting circuit; a zero-cross detecting circuit that, when the brushless motor is in a 120° conduction, detects zero-cross points of the coils of the respective phases U, V, and W and generates zero-cross signals; a rotor position detecting unit based on a zero-cross signal that determines a rotor position of the brushless motor based on the zero-cross signals of the coils of the respective phases U, V, and W generated by the zero-cross detecting circuit, and that outputs the same as first rotor position information; a triangular wave generating circuit that, when the brushless motor is in a 180° conduction, detects an output voltage of the sub coil, and generates a triangular wave signal synchronized with the output voltage; a rotor position detecting unit based on a triangular wave signal that determines a rotor position of the brushless motor based on the triangular wave signal generated by the triangular wave generating circuit, and outputs the same as second rotor position information; and a motor control unit that controls the brushless motor based on information of the rotor stop position when activating the brushless motor, controls the brushless motor based on the first rotor position information when in the 120° conduction, and controls the brushless motor based on the second rotor position information when in the 180° conduction.