To provide a stepping-motor driving device reducing a waveform distortion in a winding current near a zero-cross point.
The stepping-motor driving device includes a reference signal generating section 14a generating a reference signal indicating the desired value of a current supplied to a winding 3, a switching section 5 supplying a winding 3 with electricity under a feed state and stopping a feed to the winding 3 under a non-feed state and a feed-current measuring section 20 measuring the current supplied to the winding 3. The stepping-motor driving device further includes a zero-cross neighborhood decision section 23 specifying a point in the vicinity of the zero cross point where the absolute value of a current desired value is made smaller than a predetermined threshold and a variable-frequency reference pulse generating section 18a to output the reference pulse of a frequency varying in response to the specification of the zero-cross neighborhood decision section 23. The stepping-motor driving device further includes a PWM control section 15a bringing the switching section 5 to the non-feed state at the point when the reference pulse is output and bringing the switching section 5 to the non-feed state at the point when the current measured by the feed-current measuring section 20 exceeds the desired current value.
YAMAO SAKI
FUJINAKA HIROSHI
