Patent ID: 6529247
Filing Date: 2003-03-04
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 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 voltage hold circuit for receiving a voltage detected by the detector circuit and holding the voltage; an arithmetic circuit for receiving a voltage detected by the detector circuit during a period in which the reference signal is selected by the selector circuit and a voltage held by the first voltage hold circuit during a period in which neither of the color video signal and reference signal are selected, and obtaining a voltage in difference between these voltages; and a comparator circuit for receiving a voltage in difference obtained by the arithmetic circuit, comparing the voltage in difference with a reference voltage, and generating the control signal to control an operation of the adjusting circuit according to the comparison result.