BRUSHLESS MOTOR DRIVING SYSTEM

PURPOSE:To suppress torque ripple by detecting variation of flux of a rotor magnet in the form of a sine wave, synthesizing a signal waveform for correcting torque ripple from thus detected outputs and then superposing the synthesized signal on a current control signal. CONSTITUTION:Torque ripple correcting signals are synthesized in a torque ripple correcting signal synthesizing circuit 18 and then a maximum value MAX and a minimum value MIN of HE are detected. The maximum value MAX is then inverted through an inverting circuit to produce a -MAX. The inverted maximum value -MAX is added to the minimum value MIN in an adding circuit thus producing a torque ripple correcting signal VTO. DC component is then regulated through external resistors R5, R6 to produce a torque ripple correcting signal VTIN to be superposed on a control signal. The torque ripple correcting signal VTIN is then superposed on a current control signal and the total current is increased synchronously with the dropping timing of torque ripple thus suppressing torque ripple.