| 摘要 |
PROBLEM TO BE SOLVED: To provide a brushless-motor driving circuit, by which a brushless motor can be operated at variable speed in a sensor-less type without being affected by chopper control. SOLUTION: The change of an armature current due to the revolution of the brushless motor 51 is detected by a current detractor 4 and output to a higher-harmonic removing circuit 13. Only a voltage during a time when a lower arm transistor is on by synchronization with chopper control is stored in the circuit 13, and the voltage is amplified by quintuple or septuple and output to a commutation command circuit 9 and a sampling circuit 5. The output voltage is stored in the sampling circuit 5 at timing immediately before the off of a commutation command, and the stored voltage is amplified by 1.4 times as large as the voltage by an amplifier circuit 6, and output to the commutation command circuit 9. When an output from the higher-harmonic filter circuit 13 reaches an output from the amplifier circuit 6, a commutation command from the commutation command circuit 9 is output to a counter circuit 11, and the commutation operation of the brushless motor 51 is conducted through a distributing circuit 12. |
