Patent ID: 7053584

Claim:
A motor driving device, comprising: exciting current detectors for detecting exciting currents of motor windings of a motor; an exciting current amplitude computation means for computing the square of an exciting current amplitude value from exciting current detection values detected by said exciting current detectors; and a voltage impression unit for impressing voltages at values corresponding to the square of said exciting current amplitude value to the motor windings; a current amplitude deviation detection means for computing a current amplitude square deviation value representing a difference between a square of a current amplitude command given from outside and a square of said exciting current amplitude value; current command computation means for computing current commands in the form of at least one of sine wave signal and cosine wave signal on the basis of an angle command given from outside; and multiplication means for multiplying values corresponding to said current amplitude square deviation value by said current commands, wherein said voltage impression unit impresses voltages, corresponding to outputs of said multiplication means, to said motor windings; and wherein said motor is a stepping motor, and said voltage impression unit feeds motor winding currents varying in the form of a sine wave every time an external command pulse is impressed.