CRT Spot suppression circuit
Blanking circuit for use in a display apparatus which has a cathode-ray tube
Video display apparatus with kinescope spot burn protection circuit
Spot killer circuit having blanking function
Spot elimination circuit for a cathode ray tube Patent #: 5677730
ApplicationNo. 000866 filed on 12/30/1997
US Classes:315/380, Control only at turn-on or turnoff of circuit315/381, Circuits control grid-cathode circuit of tube315/384, Ray blanking348/173CATHODE-RAY TUBE BURN-IN PREVENTION
ExaminersPrimary: Westin, Edward P.
Assistant: Wells, Nikita
Attorney, Agent or Firm
Foreign Patent References
International ClassesH01J 029/52
Foreign Application Priority Data1996-12-30 KR
AbstractA spot is prevented from occurring on the center portion of a cathode ray tube when electric power is turned off by using a voltage charged in a capacitor which are used for outputting a vertical blanking signal in a vertical blanking signal generating circuit of an image display device for displaying an image in use of the cathode ray tube. The present invention is provided with a discharge cut-off element between a negative electric power source and the capacitor for outputting a vertical blanking signal and a discharging element for discharging a charged voltage of the capacitor to the ground. The present invention prevents a charged voltage ofthe capacitor from being discharged until thermoelectrons are not emitted from the cathode so as to supply a negative charged voltage to the first grid of the cathode ray tube continuously, so that a spot is prevented from occurring. All the negative voltage charged in the capacitor is discharged when a time period has elapsed during which occurrence of a spot is blocked.