A motor driving circuit of a brushless motor

摘要

A motor driving system according to the present invention comprises a power converter for supplying a brushless motor having a permanent magnetic rotor with pulse-width modulation controlled driving power; a magnetic-pole position detector for detecting a magnetic-pole position of the motor rotor; a speed detecting means for detecting a rotational speed of the motor according to an output signal of the magnetic-pole position detector; a speed control operation means for outputting a deviation of an output signal of the speed detecting means from a speed instruction; a means for generating a plurality of instruction signals in response to an output signal of the speed control operation means; a means for generating modulated waves by selecting one of the plurality of instruction signals according to the output signal of the speed control operation means; and a means for controlling the power converter by means of pulse width modulation according to the modulated waves.