Patent ID: 6424379
Filing Date: 2002-07-23
Classification: H04N

Abstract:
A vertical synchronization separation circuit comprising:a first comparator of an input complex synchronization signal with a first reference voltage and producing a comparison result, the first comparator including an input side transistor and an output side transistor connected as a differential air; a first current source connected to a collector of said output side transistor of the differential pair; a second current source commonly connected to an emitter of said input side transistor and an emitter of said output side transistor, said second current source supplying a larger current than the current supplied by said first current source; a capacitor charged or discharged depending upon a flow of the current from said first current source in accordance with the comparison result produced by said first comparator; a second comparator for comparing an integrated output produced by said capacitor with a second reference voltage; a pulse generator generating and outputting a vertical output pulse when the integrated output of said capacitor exceeds the second reference voltage; a third current source supplying a current smaller than the current produced by said first current source; a first switch switching between said first current source and said third current source and outputting a current to the collector of said output side transistor; and a switch control unit controlling said first switch to connect said third current source during a period from resetting of a vertical synchronization signal until completion of a vertical blanking period.