Yamaha Corporation

Shinzi Aoshima

Sadayuki Narusawa

A synchronizing signal reproducing circuit in a disc playback device for playing back discs such as a video disc and Compact Disc comprises an assumed synchronizing signal detection circuit for taking out an assumed synchronizing signal having possibility of being a true synchronizing signal from a signal reproduced from a disc, a window establishing circuit for establishing a window which, on the basis of a preceding true synchronizing signal, includes a timing at which a true synchronizing signal is expected to occur, and a synchronizing signal picking up circuit for picking up the assumed synchronizing signal as a true synchronizing signal if it occurs in the window. The window is so established that a future side range becomes wider than a past side range with respect to the timing at which the true synchronizing signal is expected to occur. The window establishing circuit may comprise a counter counting the number of times the synchronizing signal has not consecutively been detected in the window and operate in such a manner that, when count of the counter has reached a predetermined value, the window is enlarged to pick up the synchronizing signal in the enlarged window and, when the synchronizing signal has not been found even in this enlarged window, the window is removed for further detection of the synchronizing signal.

Synchronizing signal reproducing circuit in a disc playback device

In one aspect of the invention, a disc motor control circuit in a disc playback device comprises a rotation detection circuit for detecting the rotation speed of a disc motor and producing a rotation detection signal, a first control circuit for controlling the rotation speed of the disc motor by comparing the rotation detection signal with a reference clock, a second control circuit for controlling the rotation speed of the disc motor by comparing a synchronizing signal taken out of a reproduced signal from the disc with a reference clock, a window circuit for establishing a window for an expected timing of a next synchronizing signal on the basis of the synchronizing signal taken out of the reproducing signal, a state detection circuit for detecting a state of rotation of the disc motor by counting the number of the synchronizing signal entering the window and a mode switching circuit for selectively operating one of these control circuits in accordance with the result of counting in the state detection circuit.

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Hamamatsu, Japan

Shinzi Aoshima