Patent ID: 6215258
Filing Date: 2001-04-10
Classification: H01J,H04N

Abstract:
A dynamic focus circuit that obtains a dynamic focus signal from a parabolic waveform signal generated at both ends of an S-shaping capacitor, the dynamic focus signal being supplied to an electron gun in a cathode ray tube to focus an electron beam, and the parabolic waveform signal having a horizontal deflection period, the dynamic focus circuit comprising:a transformer, having a primary coil and a secondary coil, the parabolic waveform signal being applied to the primary coil;a first converting means for converting a signal induced in the secondary coil of the transformer to a dynamic focus signal at a gain of less than one during a first part of a horizontal deflection period, the first part of the horizontal deflection period being when the voltage of the signal induced in the secondary coil does not exceed a specified reference value; anda second converting means for converting the signal induced in the secondary coil of the transformer to a dynamic focus signal at a gain greater than the gain of the first converting means during a remainder of the horizontal deflection period, the remainder of the horizontal deflection period being when the voltage of the signal induced in the secondary coil is not less than the specified reference value.