| 摘要 |
PURPOSE:To reduce disturbance on a picture and to shorten a time required for pull-in by switching the response speed of a phase difference detecting means to fast optimum response speed at the time of switching an input signal. CONSTITUTION:A follow-up type horizontal oscillation circuit 6 generates a horizontal pulse signal with the same frequency corresponding to the horizontal synchronizing signal of the input signal. A difference between the phase of the output horizontal pulse signal of the horizontal oscillation circuit 6 and that of the horizontal synchronizing signal of the input signal is detected at a phase detection circuit 3, and the oscillation phase of the horizontal oscillation circuit 6 is controlled so as to set the above phase difference at 0. The response speed of the phase detection circuit 3 is set so as to be accelerated by a follow-up speed switching circuit 9 at the time of switching the input signal, and in an ordinary operation, it is switched so as to be set at the optimum response speed. |
