| 摘要 |
PROBLEM TO BE SOLVED: To reduce the waveform distortion which arises in a stepping motor driver because the current value detected in the vicinity of zero cross deviates from the target current value. SOLUTION: When a zero cross vicinity determination means 11 determines it to be in the vicinity of zero cross, it switches on a switch element high in ON resistance and switches off the switch element low in ON resistance in a switching means 20. In a PWM-ON period, the voltage applied to both ends of winding 2 becomes small, whereby it lessens the supply current increase in a compulsive conduction period thereby being able to restrain a detected current value from getting over the target current value even after finish of the compulsive conduction zone. In a PWM-OFF period, the voltage applied to both ends of winding 2 goes higher, whereby it increases the quantity of current attenuation, and it lessens the current after transition in the PWM-ON period thereby being able to restrain the detected current value from getting over the target current value. COPYRIGHT: (C)2008,JPO&INPIT |
