Patent ID: 6366035
Filing Date: 2002-04-02
Classification: H04N

Abstract:
A CRT display apparatus comprising:a CRT having an electron gun; said electron gun including: a cathode; a G1 electrode, a G2 electrode, and a G3 electrode disposed in that order for drawing electrons from said cathode; and a modulating Gm electrode disposed between said G2 electrode and said G3 electrode, a transformer producing a high tension to be applied to an anode of said CRT at a secondary coil thereof; a voltage-dividing resistor dividing said high-tension to produce a voltage to be applied to said G3 electrode; a voltage generator generating a voltage having a value depending on a current flowing into said dividing resistor as a feedback voltage; a high-tension control circuit for controlling, on the basis of said feedback voltage, a voltage at a primary coil of said transformer so as to keep said high-tension at a predetermined value; a G2 electrode voltage source for outputting a predetermined voltage to be applied to said G2 electrode; a Gm electrode voltage source for outputting a predetermined voltage to be applied to said Gm electrode; and a comparator for comparing said feedback voltage with one of an output voltage of said Gm electrode voltage source and an output voltage of said G2 electrode voltage source, said comparator supplying a detection signal to said high-tension control circuit upon detecting that only said feedback voltage has fallen from a normal value, said high-tension control circuit controlling said voltage at said primary coil of said transformer so as to lower said high-tension in response to said detection signal.