| 摘要 |
PURPOSE:To control a reproduced synchronizing clock and the number of revolution of a disk by counting minimum and maximum edge lengths Nmin and Nmax by the reproduced synchronizing clock, and detecting an edge interval longer than an Nmax clock when a following edge comes before an Nmin clock. CONSTITUTION:When the number of revolution increases (decreases), a VCO6 outputs a clock synchronizing with a pulse train from an edge detector 3 within the locking range of a phase-locked loop 14. This clock leads (lags) the clock of a reference clock oscillator 9 in phase and decreases (increases) the number of revolution through a phase-voltage converter 10. When the loop 14 enters a step- out state to increase (decrease) the number of revolution, a minimum (maximum) pulse length detector 7(8) increases the oscillation frequency of the VCO6 so that the minimum (maximum) pulse interval of the pulse train from the detector 3 is larger than the Nmin clock (Nmax clock) by the clock of the VCO6. This frequency becomes larger (smaller) of the clock of an oscillator 9 and the number of revolution is increased (decreased) by converters 10 and 11 and a driving circuit 12 to a number of revolution that the loop 14 synchronizes with. |
