Patent ID: 6078151
Filing Date: 2000-06-20
Classification: H04N

Abstract:
A dynamic focus circuit for generating a focus control signal for a CRT, comprising:a first saw wave generating circuit for receiving a horizontal synchronization signal and generating a first saw wave signal in response to said horizontal synchronization signal;a first gain generating circuit for generating a first gain;a first amplifier, connected to said first saw wave generating circuit and said first gain generating circuit, for amplifying said first saw wave signal with said first gain to generate an output signal;a first reference voltage signal generating circuit for generating a first reference constant amplitude voltage signal;a first differential amplifier, connected to said first amplifier and said first reference voltage signal generating circuit, for amplifying a difference in voltage between the output signal of said first amplifier and said first reference voltage signal to generate an output signal;a first multiplier, connected to said first differential amplifier, for calculating a square value of the output signal of said first differential amplifier to generate a horizontal parabolic signal;a second saw wave generating circuit for receiving a vertical synchronization signal and generating a second saw wave signal in response to said vertical synchronization signal;a second gain generating circuit for generating a second gain;a second amplifier, connected to said second saw wave generating circuit and said second gain generating circuit, for amplifying said second saw wave signal with said second gain to generate an output signal;a second reference voltage signal generating signal circuit for generating a second reference constant amplitude voltage signal;a second differential amplifier, connected to said second amplifier and said second reference voltage signal generating circuit, for amplifying a difference in voltage between the output signal of said second amplifier and said second reference voltage signal to generate an output signal;a second multiplier, connected to said second differential amplifier, and for calculating a square value of the output signal of said second differential amplifier to generate a vertical parabolic signal; andan adder, connected to said first and second multipliers, for adding said horizontal parabolic signal to said vertical parabolic signal, to generate said focus control signal.