| 摘要 |
A control circuit is used during slow or stop-motion playback operation of a video tape device to drive video tape intermittently. In order to avoid errors in the stopping position of the tape, a pulse width modulated (PWM) signal is provided to a motor controller circuit associated with the capstan motor of the video tape device. A frequency signal generator coupled to this motor generates a frequency signal that varies with the capstan motor speed, and this frequency signal is provided to a retrigger monostable multivibrator which generates a PWM signal whose duty ratio changes in proportion to the capstan motor speed. A drive pulse generator and a brake pulse generator provide drive start and brake start signals, respectively, when it is desired to commence and stop movement of the tape. A drive circuit, including the retrigger monostable multivibrator, receives the drive start signal, the brake start signal, and the frequency signal to generate the PWM signal which is supplied to the motor controller circuit. The frequency signal is selected to have a pulse rate several tens of times the ripple frequency of the motor's torque ripple characteristic so that inaccuracies in stopping position of the motor are eliminated. |
