| 摘要 |
PURPOSE:To obtain a commutation signal without using a magnetic sensor for directly detecting the position of a pole of a rotor by starting a brushless motor based on a synchronizing rotation signal from oscillation means, a frequency signal from signal generating means and a phase detection signal, and normally operating it. CONSTITUTION:If an oscillator 18 is oscillated and a brushless motor 1 is started, the magnetized parts 11, 12 of a permanent magnet 10 are integrally rotated together with its rotor 7. When a magnetic sensor 13 is opposed to the part 11 for a frequency signal, an output signal FG is generated, and when it is opposed to the part 12 for a phase detection signal, a PG is generated. They are compared with a reference level by a waveform shaper 14, and positive and negative pulse signals are output. A switching circuit 17 compares a pulse signal PO in frequency with pulse signals PGa, FGa, and applies the signals PGa, FGa to a commutation signal generator 19 if it becomes a predetermined speed or higher. The generator 19 is reset each time the signal PGa is applied. |
