Patent ID: 6940934

Claim:
A synchronizing signal processing circuit for producing, from a first synchronizing signal entering thereto, a second synchronizing signal to be output therefrom, the synchronizing signal processing circuit comprising: a first counter counting a clock of a predetermined frequency and being reset each time an entry of the first synchronizing signal is detected; a first gate signal producing circuit for producing a first gate signal which changes to an open state when a count value of the first counter reaches a first value, and changes to a closed state when the first counter is reset and when the count value of the first counter reaches a second value larger than the first value; a second counter counting the clock and being reset upon each reception of a reset signal; a self-running synchronizing pulse producing circuit for producing a self-running synchronizing pulse when a count value of the second counter reaches the second value; a second gate signal producing circuit for producing a second gate signal which changes to the open state when the count value of the second counter reaches the first value, and changes to the closed state when the second counter is reset; a first gate circuit allowing the first synchronizing signal to pass when at least one of the first and the second gate signals indicates the open state, and blocking the first synchronizing signal at other times; a synchronizing pulse producing circuit for producing a synchronizing pulse to be output as the second synchronizing signal upon reception of the first synchronizing signal from the first gate circuit and upon reception of the self-running synchronizing pulse from the self-running synchronizing pulse producing circuit; and a reset signal producing circuit outputting the reset signal to the second counter upon reception of the first synchronizing signal from the first gate circuit and upon reception of the self-running synchronizing pulse from the self-running synchronizing pulse producing circuit.