Stepping motor driving apparatus and stepping motor driving method

Abstract

A stepping motor driving apparatus includes a detector that detects a current supplied to a winding included in the stepping motor, a first offset adding section that adds an offset to the output of the detector, an amplifier that amplifies the output of the first offset adding section, a reference signal generator that generates a reference signal indicating a current limit, a second offset adding section that adds an offset to the output of the reference signal generator, a switching section that supplies a power to the winding when the switching section is turned on and cuts off a power to the winding when the switching section is turned off, and a PWM controller that turns on the switching section every predetermined period, and turns off the switching section when the output of the amplifier exceeds the output of the second offset adding section.

1 . 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;    an offset subtracting section operable to subtract an offset from the output of the amplifier;    a reference signal generator operable to generate a reference signal which indicates a current limit;    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 offset subtracting section exceeds the current limit indicated by the reference signal.    
   
   
       2 . The stepping motor driving apparatus according to  claim 1 , wherein the offset subtracted by the offset subtracting 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.  
   
   
       3 . A stepping motor driving method comprising: 
 detecting a current supplied to a winding included in a stepping motor;    adding a first offset to the detected current;    amplifying the detected current with the added offset;    subtracting a second offset from the amplified current;    generating a reference signal which indicates a current limit; and    controlling turn-on and turn-off of a switching section, the switching section being 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,    wherein the controlling turns on the switching section every predetermined period, and turn off the switching section when the current subtracted with the second offset exceeds the current limit indicated by the reference signal.