| 摘要 |
PURPOSE:To always obtain a stable rotation signal by a method wherein a reduction means is installed in such a way that a counter electromotive voltage induced at stator windings of the commutator-less motor is short-circuited to the stator windings through diodes. CONSTITUTION:When the rotation frequency of the commutatorless motor is higher than the control target value, the period of a rotation signal from a rotation signal generation circuit 2 is smaller than the period of a reference signal from a reference signal generation circuit 3, as a result, the deviation output signal of a comparison circuit 4 becomes zero, thus, a driving circuit 5 does not operate and power is not supplied to a stator winding group 1. However, a switching circuit 7 is closed by means of the reduction command output signal of the comparison circuit 4 and when the counter electromotive voltage wave form (A) becomes a voltage VA+VD or more, then, a braking current runs to the stator windings via a rectifier circuit 6 and the switching circuit 7. At this time, if the period detection voltage level VT of the rotation signal generation circuit 2 is set between VA and (VA+VD), a stable rotation signal wave form (B) is obtained. |
