| 摘要 |
PURPOSE:To protect a motor against overheat or burning even upon failure of a switching circuit, common to all phase coils, on the conducting side by providing a protective circuit outputting a motor stop signal for turning all switching elements OFF when actual current value of any one switching element in a phase switching circuit exceeds a set value. CONSTITUTION:A protective circuit 40 continuously compares the actual current Vd flowing through a step motor 10 with a set value Vref and a comparator 41 outputs a motor stop signal STP if Vd >Vref. A control circuit 31 accepts the motor stop signal STP so long as a common switching signal Ssw is turned OFF and turns all switching signals CHGA-D to a phase switching circuit 25 OFF if the motor stop signal STP endures longer than a set time. According to the constitution, the step motor 10 can be protected against overheat or burning upon failure of a common switching circuit 21 on the conducting side regardless of the operation or idle rotation of the step motor. |
