| 摘要 |
PURPOSE:To make it difficult to receive an external magnetic field by detecting the voltage, which is induced in the coil of a motor, thereby to control the drive current of the motor. CONSTITUTION:A drive circuit and an amplifying unit are composed of P- MOSFETs 21 and 22, N-MOSFETs 23 to 26, detecting resistors 28 and 29 and a motor 20. During the non-driven operation of the motor 20, the closed loop of the motor 20 and the FEDs 23 and 24 and the closed loop of the motor 20, the resistor 29 and the FETs 26 and 23 are alternately switched to amplify the signals resulting from an external magnetic field. At this time, the voltage induced in the coil of the motor 20 by the external magnetic field is short-circuited by the closed loop of the FETs 23 and 24 so that it is converted into a relatively high current. Then, at the resistor 29, there is generated instantly a high voltage in the resistor 29, and stability is subsequently attained under a steady condition. As a result, the motor 20 is controlled by the voltage coming from the resistor 29. |
