Patent ID: 6437833
Filing Date: 2002-08-20
Classification: H04N

Abstract:
An automatic white balance adjusting circuit for automatically adjusting a white balance of a color image display tube having at least one cathode electrode, comprising:a selector circuit for receiving a color video signal having a vertical blanking period and at least one reference signal, selecting the color video signal, and selecting and outputting the at least one reference signal during a partial period of the vertical blanking period; an adjusting circuit for receiving a signal outputted from the selector circuit, adjusting at least one of a DC level and an AC amplitude of the signal in accordance with a control signal, and outputting the signal thus adjusted; a drive circuit for receiving the output signal of the adjusting circuit and outputting a driving signal to be supplied to the at least one cathode electrode of the color image display tube according to the output signal; a first detector circuit connected to the color image display tube and detecting a voltage according to a current flowing through the cathode electrode of the color image display tube; a first comparator circuit for receiving a voltage detected by the first detector circuit during a period in which the at least one reference signal is selected by the selector circuit, and comparing the voltage with a first reference voltage; a memory circuit for storing data for controlling an operation of the adjusting circuit; an update circuit for receiving the comparison result of the first comparator circuit and data stored in the memory circuit, updating the data based o the comparison result of the first comparator circuit, and supplying the updated data to the memory circuit, the updated data being stored again in the memory circuit; a D/A converter for receiving data stored in the memory circuit, converting the data into an analog signal, and output the converted signal to the adjusting circuit as the control signal; and a second detector circuit for receiving a voltage detected by the first detector circuit, and detecting a voltage fluctuation of a high voltage supplied to the color image display tube based on the detected voltage, wherein the update circuit receives an output of the second detector circuit and is controlled to update, when the second detector circuit detects the voltage fluctuation of the high voltage, the data stored in the memory circuit and corresponding to the DC level, prior to any other data.