| 摘要 |
PROBLEM TO BE SOLVED: To prevent an erroneous detection with a simple structure when a stepping motor is not rotating. SOLUTION: A control circuit 311 controls the 'on/off' of a transistor 303 with transistors 304, 305 turned on during a period that the rotation is detected immediately after the end of driving pulses. A comparator 310 compares a detected voltage that occurs at a connection point OUT2 of a detecting resistor 308 and a coil 307 with a threshold value voltage VSS. It judges that the stepping motor has rotated when the detected voltage is equal to or lower than the VSS, and that it hasn't when the detected voltage is higher than the VSS. At this moment, because a current ia flows immediately after the end of the driving pulses, the detected voltage that occurs at the junction point OUT2 becomes a voltage of reversed polarity against the VSS and does not become the VSS or lower so that the comparator 310 discriminates that the stepping motor has not rotated. |
