BEAM CURRENT LIMITING DEVICE FOR CATHODE RAY TUBE

• Main Authors: MITO YUMIKO, TAMURA TAKAHIKO
• Format: Patent
• Language: English
• Published: 24.01.1995
• Edition: 6
• Subjects: ELECTRIC COMMUNICATION TECHNIQUE; ELECTRICITY; PICTORIAL COMMUNICATION, e.g. TELEVISION

PURPOSE:To prevent the quality of mutually different pictures on common scanning lines from being deteriorated by releasing the limitation of beam current for a picture having short scanning line length as compared with that of a picture having long scanning line lenght. CONSTITUTION:A contrast control circuit 3 and a brightness control circuit 4 are controlled as follows by a control signal outputted from a current limitation correcting circuit 12. Namely when the average value of beam current on a CRT 5 exceeds a reference level, the circuit 3 is controlled so as to reduce luminance. Thereby the CRT 5 is fed back so that the voltage of a node between a resistor 8 and a capacitor 9 is not reduced to reference voltage Vref or less. When the average value of beam current on the CRT 5 exceeds the reference level, the circuits 3, 4 are controlled so that contrast is reduced when a black beam level is on the black side from a reference black level or luminance is reduced when the black beam level is on the white side.