Control apparatus for brushless motor

A control apparatus for a brushless motor which has a stator provided with an armature winding having armature coils connected in three-phase star-connection, and a rotor comprising a permanent magnet having at least two poles, which rotor is driven by switching over an exciting current supplied to said armature coils, comprising:

• a resistance circuit having a plurality of resistors connected in star-connection so that each of the resistors is in parallel with a corresponding one of the armature coils of said armature winding;
• signal generating means for generating an excitation switchover signal to switch over and control the exciting current supplied to the armature coils of said armature winding in accordance with variations in a potential difference between a neutral point of said armature winding and a neutral point of said resistance circuit;
• an inverter circuit for switching over and controlling the exciting current supplied to the armature coils of said armature winding in accordance with the excitation switchover signal from said signal generating means;
• first detecting means for detecting a polarity of a counter electromotive force generated in the armature coil for one phase due to revolution and oscillation of said rotor when the exciting current is supplied to the armature coils for the other two phases at the start of said brushless motor;
• and
• second detecting means for detecting a stable position where said rotor stops and a direction of revolution and oscillation of said rotor and generating a detection signal indicative thereof when the exciting current is caused to flow through the armature coils for two phases at the start of said brushless motor, in accordance with the particular polarity of the counter electromotive force detected by said first detecting means and the excitation switchover signal from said signal generating means, and for supplying a starting signal to said inverter circuit in accordance with the detection signal.

A control apparatus for a brushless motor which has a stator provided with an armature winding having armature coils connected in three-phase star-connection and a rotor having a permanent magnet having at least two poles, which rotor is driven by switching over an exciting current supplied to said armature coils, comprising:

• a resistance circuit having a plurality of resistors connected in star-connection so that each of the resistors is in parallel with a corresponding one of the armature coils of said armature winding;
• signal generating means for generating an excitation switchover signal to switch over and control the exciting current supplied to the armature coils of said armature winding in accordance with variations in a potential difference between a neutral point of said armature winding and a neutral point of said resistance circuit;
• an inverter circuit for switching over and controlling the exciting current supplied to the armature coils of said armature winding in accordance with the excitation switchover signal from said signal generating means;
• and
• peak value detecting means for detecting a substantially peak value of a counter electromotive force generated in the armature coil for one phase due to revolution and oscillation of said rotor and generating a detection signal indicative thereof when the exciting current is supplied to the armature coils for the other two phases at the start of said brushless motor, and for supplying a starting signal to said inverter circuit in accordance with the detection signal.