| 摘要 |
PURPOSE:To form a motor drive circuit having small power consumption by obtaining desired motor speed and necessary voltage responsive to a load form a variable voltage source varying in response to the counterelectromotive force of the motor or the motor drive current. CONSTITUTION:The minimum voltage signal 51 of respective phase coil voltages 23-25 of a 3-phase brushless motor 1 obtained from diodes 40-42, a resistor 46 and a reference voltage source 47, the maximum voltage signal 52 of respective phase coil voltages 23-25 is obtained from diodes 43-45 and a resistor 48, and an output voltage control signal 38 responsive to the difference between the minimum and the maximum values is obtained from an arithmetic amplifier 22. The signal 38 becomes a feedback control signal 36 through an arithmetic amplifier 26, is fed to a comparator 28, and is compared with the output 35 of a triangular wave generator 29. When the signal 38 becomes high, the signal 38 becomes high to increase the ON time of the transistor 31 to raise the motor drive voltage 39. When the signal 38 becomes low, the motor drive voltage 39 is lowered in the reverse operation to the above. |
