| 摘要 |
PURPOSE: To prevent the failure in commutation and step out by forcibly outputting the commutation pulse and chopping signals at the time of start where the detection of position is not obtained, and checking the position of a rotor at the time of finish of forced commutation. CONSTITUTION: A commutation circuit 7 makes out a commutation pulses to commutate the semiconductor switches 3a-3f of an inverter circuit 3 from the output of a position detecting circuit 6. A chopping signal generating circuit 11 makes out waveforms different in on/off ratio with constant frequency, according to the duty value for varying the revolution of a DC motor 4. A forced commutation control means 13 outputs commutation pulses and chopping signals if the output of the a position detecting circuit 6 can not be obtained at the time of start of the DC motor 4. A composition circuit 17 composes commutation pulse and chopping signals. A rotor position checking means 19 checks the position of the rotor at the point of time when the forced commutation by starting sequence is finished. |
