| 摘要 |
PURPOSE:To prevent reverse rotation of the motor, by providing a braking means to apply reverse voltage to the direct-current motor in response to the integral voltage obtained by integrating the pulse. CONSTITUTION:When a transistor Tr5 is OFF, a capacitor C3 is charged by Vcc through a resistor R8 and a diode D2, until reaching the divided potnetial divided by resistors R9 and R10. At this time, the higher the rotating speed of the turntable, namely, a direct-current motor 3, the more is charged the capacitor C3. Therefore, a high voltge is obtained at the emitter of transistor Tr6, or the output end thereof. In response to the output of this transistor Tr6, a transmission voltage is supplied to the direct-cuurent motor 3 through the Darlington circuits of transistors Tr7 and Tr8, so that the motor may be controlled. Thus, the lower the rotating speed of the turntable, the smaller becomes the braking force. When the rotation stops, no transmission voltage is applied to the direct-current motor 3, so that reverse rotation of the direct-current motor 3 may be prevented. |
