Oscillators – Automatic frequency stabilization using a phase or frequency... – With reference oscillator or source
Patent
1996-01-11
1998-02-17
Callahan, Timothy P.
Oscillators
Automatic frequency stabilization using a phase or frequency...
With reference oscillator or source
331 1A, 331 17, 331DIG2, H03L 7095, H03L 700
Patent
active
057195323
ABSTRACT:
A horizontal lock detector circuit monitors charge pump control signals within a horizontal phase-lock loop to determine when the sampling pulses generated by the video system are locked in phase with the synchronization pulses of the input composite video signal. An output signal is generated by the lock detector circuit which is active when the sampling pulses are locked in phase with the input signal and inactive when the sampling pulses are not locked in phase with the input signal. The charge pump control signals are generated by a phase detector circuit within the phase-lock loop in response to a difference in phase between the sampling pulses and the input signal. Once the sampling pulses are locked in phase with the input signal, the charge pump control signals will become inactive. A current source is enabled when either of the charge pump control signals are active. The current source builds up a first level of charge on a first capacitor during the horizontal blanking period. A detecting circuit monitors the first level of charge to determine when it rises above a first threshold value. A second level of charge is built up on a second capacitor when the first level of charge is above the first threshold value. An output circuit is coupled to the second capacitor for generating an output signal which is activated when the second level of charge fell below a second threshold value and deactivated when the second threshold level of charge rises above a third threshold level. When the output signal is active the sampling pulses are locked together in phase with the input signal.
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Nayebi Mehrdad
Ngo Duc
Callahan Timothy P.
Luu An T.
Sony Corporation
Sony Electronics Inc.
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