Patent ID: 7352150

Claim:
A stepping motor driving apparatus comprising: a detector operable to detect a current supplied to a winding included in the stepping motor; a first offset adding section operable to add an offset to the output of the detector; an amplifier operable to amplify the output of the first offset adding section; a reference signal generator operable to generate a reference signal which indicates a current limit; a second offset adding section operable to add an offset to the output of the reference signal generator; a switching section operable to supply a power to the winding when the switching section is turned on, and cut off a power to the winding when the switching section is turned off; and a PWM controller operable to turn on the switching section every predetermined period, and turn off the switching section when the output of the amplifier exceeds the output of the second offset adding section, wherein the offset added by the second offset adding section is set to a value determined by multiplying the offset added by the first offset adding section by an amplification factor of the amplifier.