| 摘要 |
PURPOSE:To limit the application of an overvoltage to a motor by non-linearly varying the amount to be negatively fed back to the input side of an operational amplifier from the output side of an output circuit. CONSTITUTION:A servo circuit 16 outputs a control signal 18 on the basis of a rotating speed signal of a motor 10 outputted from a rotating speed detector 12. An operational amplifier circuit 20 has a loop gain R2/R1 which is determined by resistors R2, R1 at the noraml time. Thus, the motor 10 at the normal time is controlled at the applied voltage in response to the control signal 18 from a servo circuit 16. When an overvoltage is to be applied to the motor 10 due to the external disturbance of the motor 10 or the carrier leakage of the servo circuit 16, switching means 28 is turned ON by a command signal 30 from a servo circuit 26, a negative feedback of the amount larger than the normal time is applied to an operational amplifier 22, the loop gain of the circuit 20 decreases, thereby limiting the overvoltage to the motor 10. |
