| 摘要 |
PURPOSE:To control continuously and high accurately the rotational frequency of a record player, by controlling the rotational frequency on the basis of the sum of frequencies of two oscillators, and varying continuously the frequency of one of the two oscillators. CONSTITUTION:A turntable driver is provided with a driving circuit 1, frequency generator 3, frequency-voltage converter 4 and a phase comparator 6. The rotational frequency of the turntable is controlled to obtain the same frequency and same phase between a signal fG and the output signal fs of a frequency divider 29. The rotational frequency is varied in proportion to the frequency fs. While a frequency controller is provided with oscillators 21 and 25, frequency dividers 22 and 24, a frequency subtractor 23, phase comparator 26, LPF27 and a voltage controlled oscillator 28. An output signal fR=fM-fN is obtained from the subtractor 23. The oscillator 28 produces a frequency signal f0 in proportion to the output voltage of the comparator 26 which is proportional to the phase difference between signals fR and fV. The dividing ratios of dividers 22 and 24 are selected properly together with the frequencies of oscillators 21 and 25. As a result, the signal f0 can be varied continuously on the basis of a signal fI by changing the signal fV. |
