Bürstenloser Gleichstrommotor

摘要

Disclosed is a brushless DC motor which does not have a position sensor for detecting a rotation al position of the rotor, in which conducting phases of the stator windings to be detected are subsequently selected by multi-phase selection signals in response to a conducting state of the stator windings, then a pulse signal train is generated by detecting the counter electromotive forces induced in the conducting phases subsequently selected and a trapezoidal waveform signal is formed by a slant waveform signal generated in response to the pulse signal train thus obtained. Furthermore, with the trapezoidal waveforms signal thus formed as position signal of the rotor, an electric current signal having a trapezoidal waveform is supplied to the stator windings, resulting in smooth commutation of the conducting phase of the stator windings. When to be started, phase commutation of the stator windings is carried out forcibly by means of a pseudo output pulse, thus being capable of providing a starting characteristic compatible with that obtained in conventional motors having a rotor position sensor.