Power supplying apparatus for electron gun in CDT

A method for recovering a normal focus voltage of an electron gun in a color display tube, the method comprising:

• detecting a focus voltage applied to a focus grid of said electron gun;
• comparing said focus voltage with a predetermined reference voltage;
• and
• boosting said focus voltage applied to said focus grid when said focus voltage is lower than said reference voltage.

A power supply apparatus, the apparatus comprising:

• a transformer having a focus voltage output terminal and an acceleration voltage output terminal, said transformer being a fly back transformer;
• a power supplying part supplying a predetermined reference voltage;
• a focus voltage detection part detecting a focus voltage of said focus voltage output terminal, said focus voltage detection part including at least one resistor unit connected in series to said focus voltage output terminal;
• and
• a focus voltage boost part boosting said focus voltage of said focus voltage output terminal when said focus voltage detected by said focus voltage detection part is lower than said reference voltage of said power supplying part.