| 摘要 |
PURPOSE: To correct distortion on a screen caused by the beam current load of an alta-terminal by performing envelope detection for the amplitude change of a 2nd voltage pulse, while coupling an envelope detector to a resupply terminal, and coupling it to a scan current modulator, so as to apply control in a raster size. CONSTITUTION: A voltage Vrs generated at a resupply terminal 51 is supplied to an envelope detector 10 for generating a raster size control signal to be supplied to a terminal 32 of a diode modulator for controlling the raster size as the function of the beam current load. The amplitude of a horizontal frequency pulse 54 in negative direction changes as a function of load of a beam current with respect to an alta-terminal 52. When the beam current pulled out by the anode of a picture tube is increased by the increase in video drive to a cathode, the voltage pulse 54 becomes further negative, and the negative peak of the pulse follows up the beam current load. Thus, the tendency in the fluctuation of raster width at the time of beam current load is suppressed. |
