Method of detecting state of synchronization loss in stepping motor

摘要

In a method of detecting synchronization loss in a stepping motor, a means for applying either control current or control voltage to a coil (4) of each phase to thereby drive a stepping motor (1) and a means for individually measuring a back EMF voltage (V) induced at the coil (4) of each phase are employed, wherein application of either the control current or the control voltage at the coil (4) of each phase is halted by turns phase by phase for such a short time period (t) as not to affect rotation of a rotor (3) of the stepping motor (1) at a predetermined timing within one step period (stp) of the rotor (3), the back EMF voltage (V) at the coil (4) is measured during the short time period (t), and the stepping motor (1) is judged to lose synchronization when the measurement result of the back EMF voltage (V) at the coil (4) of at least one phase satisfies a predetermined detection criterion.