Patent ID: 6097440
Filing Date: 2000-08-01
Classification: G09G,H03L,H04N

Abstract:
A synchronous processing device for a multi-scan display device compatible with a plurality of horizontal synchronizing frequencies, said synchronous processing device comprising:a horizontal oscillation circuit;an AFC circuit which receives an input horizontal synchronizing signal and which controls said horizontal oscillation circuit so as to respond to the input horizontal synchronizing signal when said input horizontal synchronizing signal is substantially constant;frequency measuring means for measuring an input horizontal frequency; andcontrol means including:means for determining whether the frequency measured by the frequency measuring means is within a range with which said multiple-scan display device is compatible and processing said measured frequency as noise when the measured frequency is outside the frequency range; andmeans for determining the true value of the horizontal synchronizing frequency on the basis of the frequency measured by said frequency measuring means, said control means controls the oscillation frequency of said horizontal oscillation circuit in accordance with changes in the determined true value when the determining means determines that the measured frequency is within the predetermined range and said control means does not control the oscillation frequency of said horizontal oscillation circuit in accordance with changes in the determined true value when the determining means determines that the measured frequency is outside the predetermined range.