| 摘要 |
<P>PROBLEM TO BE SOLVED: To reduce noise in an AM band which is generated when a brushless motor is driven and to improve the efficiency of the motor drive. <P>SOLUTION: This controller of a brushless motor has a fan speed change target value calculation circuit 28 which receives a revolution direction signal directing a revolution of a rotor and calculates a duty ratio against a revolution target value which is the target of the revolution of the rotor, a drive voltage variable control circuit 29 which corrects drive voltages supplied to MOS-FETs Q4-Q6, and a PWM output circuit 32 which subjects the drive voltages, corrected by the drive voltage variable control circuit 29, to the duty control with the duty ratio calculated by the fan speed change target value calculation circuit 28. The drive voltage variable control circuit 29 corrects the drive voltage value in a prescribed range within a variable range of the duty ratio calculated by the fan speed change target value calculation circuit 28 to be lower than the drive voltage value in a range other than the prescribed range within the variable range of the duty ratio. <P>COPYRIGHT: (C)2003,JPO |
