| 摘要 |
PURPOSE:To remarkably reduce the vibration and noise of a brushless DC motor by setting the pulse-width of a drive pulse with the center of the side of the drive coil and the center of the poles of a rotor as reference to + or -80 deg. or less of an electric angle. CONSTITUTION:The frequency signal phi1 which depends upon the number of poles of a rotary permanent magnet obtained through a detector 108 and an amplifier 109 becomes phi8, phi9 by the phase shifter in a drive pulse circuit 110. When phi6=1 at the starting time, the signals phi8, phi9 are inverted, and the pulse width is set to become approx. 160 deg. of an electric angle and + or -80 deg. or less with the center of the side of the drive coil and the center of the poles of permanent magnets as reference. The signal phi1 is set to the signal phi2 of delay phase of 90 deg. of electric angle in the phase shifter in a control circuit 113, multiplied to phi3 in a gate circuit 29, and converted to the signal phi4 of pulse width in the waveform shaper. The signal phi4 is converted by a triangular converter to a signal phi5, compared by a voltage comparator with the reference voltage Vst, thereby becoming the pulse width waveform phi6 inversely proportional to the frequency of the signal phi. The signals phi6, phi8, phi9 are combined by gate circuits 18, 19 to produce drive pulses phi10, phi11. |
