| 摘要 |
PROBLEM TO BE SOLVED: To optimize each blanking period of sets of video information whose horizontal synchronizing signal frequency differs from each other by discriminating a kind of an input video signal from the frequency of the horizontal synchronizing signal and controlling a phase of a horizontal deflection pulse accordingly. SOLUTION: A frequency discrimination circuit 1 detects a frequency of a horizontal synchronizing signal A to provide an output of a discrimination result J depending on a kind of an input video signal. A reference phase generating circuit 2 outputs a reference phase signal B providing a phase of a horizontal deflection pulse optimum to the input video signal based on the horizontal synchronizing signal A and the discrimination result J. A horizontal drive pulse generating circuit 20 gives horizontal drive pulses I1, I2 with a duty factor depending on the discrimination result J to a horizontal deflection circuit 13. A phase difference voltage detection means consisting of a multiplier 6, an LPF 7, and a comparator 8 gives phase control signals H1, H2 to the horizontal drive pulse generating circuit 20 on the basis of a phase difference between horizontal deflection pulses E1, E2 from the horizontal deflection circuit 13 and a reference phase signal B. |
