AUTOMATIC WHITE COLOR BALANCE ADJUSTMENT CIRCUIT AND VIDEO DISPLAY DEVICE

摘要

PROBLEM TO BE SOLVED: To fast follow a sudden change of the DC level of a video signal that is caused by the variance of high voltage and to adjust. SOLUTION: A high voltage fluctuation detection circuit 25, a compulsive selection circuit 26 and a convergence detection circuit 27 are added to a conventional constitution. The circuit 25 detects a state where the converted voltage outputted from a current detection circuit 21 changes largely, and the output of the detection circuit 25 is supplied to the circuit 26. The circuit 26 controls a selector 24 to select only the black level updating digital data which are generated by an AKB processing circuit 23 when the change of high voltage is detected. Then the circuit 26 updates the data of a memory circuit 13R. The circuit 27 detects whether the actual black level is converged and sets again the circuit 26 in the state where the selector 24 selects the adjusting operations of both black and white levels.