Patent ID: 8497653
Filing Date: 2013-07-30
Classification: G05B,H02P

Abstract:
1. A driver circuit which supplies a motor drive current to a stepping motor which comprises two coils and which rotates a rotor driven by the two coils by setting different phases for the motor drive currents supplied to the two coils, the driver circuit comprising: a detecting circuit including a comparator to compare a voltage between each terminal of a first of the two coils and to detect, during a high impedance period where a first coil of the two coils is in a high-impedance state, a point in time when an induced voltage generated in the first coil crosses a predetermined value, based on the comparison by the comparator; a controlling circuit which controls the amount of the motor drive current supplied to the first coil such that the point in time when the induced voltage crosses the predetermined value occurs near the center of the high impedance period, based on the detection by the detector; and a generator configured to generate an offset voltage to adjust the predetermined value.