| 摘要 |
PROBLEM TO BE SOLVED: To provide a brushless motor drive circuit having improved rotary efficiency where noise generated when switching the excitation phase of an excitation coil has been reduced. SOLUTION: When transistors Q1-Q3 are subjected to rectangular wave ON control based on a rotor position signal generated by an induced voltage that is generated across the excitation coils 3, 4, and 5 and transistors Q4-Q6 are subjected to pulse width rectangular PWM control, the half period (π radian) of the rotor position signal is counted, the count value is set to T, T/2 is calculated from T, the lapse point of T/2 from an edge immediately after counting the rotor position signal in a phase being counted is set to the switching point of a bi-phase timing that differs from the counted phase, and the pulse width sinusoidal wave PWM control of T/8 width is made immediately before and after each control by a pulse width sinusoidal wave PWM signal where an 8-step step voltage with T/64 step width that is generated by dividing a voltage for pulse width modulation into eight with a division ratio based on a sinusoidal function is subjected to pulse width modulation by a triangular wave voltage. |
