Control apparatus for a recording medium drive motor in a digital information reproducing apparatus
AssigneeHitachi, Ltd.
InventorsHiroyuki Kimura, Shin-ichi Ohashi, Keizo Nishimura
Life of this patent
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Abstract
A digital audio disc (DAD) reproducing apparatus comprises pulse width detection and pulse width-to-voltage conversion means for detecting a signal having a predetermined pulse width such as a maximum or minimum pulse width of code modulated digital data signals reproduced by a pickup and converting the detected signal to a voltage proportional to the pulse width, and pulse width error detection means for detecting an error between the converted voltage and a reference voltage corresponding to a reference pulse width. Since the pulse width of the digital data signal changes with a clock rate, the error from the reference voltage represents an error in the clock rate.
Claims12
A control apparatus for a recording medium drive motor in a digital information reproducing apparatus comprising:
- (a) pickup means for reproducing a digital signal from said recording medium having a digital information recorded thereon in the form of a signal sequence modulated with a predetermined plural number of pulse widths;
- (b) transition point detection means for detecting rising edges and falling edges of the reproduced digital signal to detect signal transition points;
- (c) counter means responsive to the output from said transition point detection means for counting a length of an input pulse width;
- (d) first latch means for reading in the content of said counter means and holdng a count corresponding to a maximum pulse width of the input pulse widths;
- (e) compare means for comparing input value and output value of said first latch means and loading the content of said counter means to said first latch means when the input value from said counter means is larger than the output value of said first latch means;
- (f) second latch means adapted to receive the content of said first latch means and holding a maximum count of the counts in said counter means in a predetermined period;
- (g) clock rate error signal generating means for comparing the output of said second latch means with a reference value corresponding to a predetermined maximum pulse width to produce an error signal for the clock rate;
- and
- (h) drive means responsive to the output of said clock rate error signal generating means for producing a drive output to drive said recording medium drive motor.
A control apparatus for a drive motor of a recording medium in a digital information reproducing apparatus comprising:
- pulse width detection means for detecting in a given period one of a maximum and minimum pulse width in a digital data signal derived from said recording medium and providing an output indicative thereof, the digital data being in the form of a signal sequence modulated with a predetermined plural number of predetermined pulse widths;
- reference signal source means for producing a reference signal corresponding to one of a predetermined maximum and minimum pulse width;
- error signal generating means for receiving the outputs of said pulse width detection means and said reference signal source means and for comparing said detected pulse width with said reference signal and for producing an error signal in accordance with the comparison;
- and
- drive means responsive to the output of said error signal generating means for producing a drive output for driving said recording medium drive motor and for controlling the rotation speed of the motor.
Dependencies are inferred from the claim text.