CONTROL METHOD FOR BRUSHLESS DC MOTOR

PROBLEM TO BE SOLVED: To sufficiently carry out field weakening control by increasing the leading phase angle by an estimated phase scheme in which the rotor phase of a brushless direct-current motor is estimated. SOLUTION: When controlling a brushless direct-current motor 6, a control circuit 12 outputs a driving signal with the timing of energization of the brushless direct-current motor 6 to an inverter circuit 4 to control the motor 6 in a region where the rotor position cannot be detected by inducted voltage produced in non-energized phases by an estimated phase scheme. This scheme is uses the previously obtained relation between motor current and number of motor revolutions, The rotor phase is estimated so that a motor current detected through a shunt resistor 10 and a current detector circuit 11 will take a value corresponding to a predetermined number of motor revolutions. the leading phase angle is increased by this estimated phase scheme, and thereby field weakening control can be carried out and the range of number of revolutions is expanded. COPYRIGHT: (C)2005,JPO&NCIPI