Nippondenso Co., Ltd.

Masami Nagata

Kanji Takeuchi

Yousuke Setaka

Sumio Yanase

A control apparatus for a brushless dc motor comprises: a parallel connection circuit including a plurality of series circuits connected in parallel; each series circuit having one armature coil and one field-effect transistor, one end of the parallel connection circuit being connected to one end of a dc power source; a free-wheeling diode connected across the parallel connection circuit; first semiconductor switch means connected between the other end of the parallel connection circuit and the other end of the dc power source; a plurality of second semiconductor switch means connected between respective gates of the field-effect transistors; and the one end of the dc power source; a plurality of reverse current blocking elements for preventing reverse currents from flowing into the second semiconductor switch means from the gates of the field-effect transistors; a plurality of comparators for detecting induced voltages developed across the armature coils; a drive circuit responsive to detection output signals from the comparators for sequentially driving the second semiconductor switch means so that the field-effect transistors are turned on and off to sequentially control the energization of the armature coils; and a rotor comprising a permanent magnet having a plurality of magnetic poles which is driven by magnetic fields produced by the sequential energization of the armature coils.

Control apparatus for brushless dc motors

A control apparatus detects a suitable starting point during rotational oscillation of a rotor at the start of a brushless motor by combining the polarity of a counter electromotive force generated in an armature coil of an armature winding of the brushless motor for a nonexcited phase due to the rotational oscillation of the rotor (when armature coils for particular phases are excited at the start of the brushless motor) with the pulse edge of an excitation switchover signal obtained from the potential of a neutral point of the armature winding having the armature coils connected in star-connection and that of a neutral point of a detecting resistance circuit having resistors connected in star-connection. Each of the resistors of the resistance circuit is arranged in parallel with a corresponding one of the armature coils the armature winding. By driving the brushless motor from the detected suitable starting point, it is possible to effect smooth and quick control of the starting operation of the brushless motor.

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Okazaki, Japan

Masami Nagata