Control circuit of brush-less motor, control circuit of sensor-less brush-less motor, brush-less motor apparatus, sensor-less brush-less motor apparatus and vacuum pump apparatus

Abstract

To provide a control circuit or the like of a brush-less motor capable of properly controlling current of motor windings by detecting positions of magnetic poles of a rotor at a rotational frequency of the rotor from low rotation which cannot lock a PLL circuit to steady-state rotation for rotating at high speed. Positions of magnetic poles are detected by a change in a magnetic flux (magnetic flux signal) of motor windings caused by rotating a rotor having the magnetic poles, thereby, a synchronizing signal (ROT signal) in synchronism with rotation of the rotor is generated. When the rotor is rotated at a low rotational frequency which cannot lock a PLL circuit, the rotor is driven by using predetermined two driving voltage vectors among outputable driving voltage vectors and when a rotational frequency capable of locking the PLL circuit is reached, the rotor is driven by successively outputting the outputable driving voltage vectors in synchronism with the positions of the magnetic poles detecting the outputable driving voltage vectors. Further, the magnetic flux signal is provided by using voltage between two phases at which phases and magnitudes of voltage drop caused by inductances of motor windings are equal to each other.