VERTICAL PIN-CUSHION DISTORTION CORRECTION CIRCUIT

摘要

PURPOSE:To automatically control a vertical pin-cushion distortion correction quantity even when a horizontal frequency is changed by providing a vertical pin-cushion distortion correction control circuit between a vertical pin-cushion distortion correction waveform generating circuit and a vertical pin-cushion distortion correction output circuit and detecting a vertical deflection current so as to keep the vertical pin-cushion distortion correction current constant. CONSTITUTION:A vertical pin-cushion distortion correction control circuit 7 is provided between a vertical pin-cushion distortion correction waveform generating circuit 6 and a vertical pincushion distortion correction output circuit 8. A vertical deflection current detection resistor 5 converts a vertical deflection current with a vertical pin-cushion distortion correction current superimposed thereon into a voltage and it is given to the vertical pin-cushion distortion correction control circuit 7. The vertical pin-cushion distortion correction control circuit 7 uses a comparator to compare a peak voltage Va from the detection resistor 5 with a reference voltage and controls a gain control circuit so as to increase a gain of a vertical pin-cushion distortion correction waveform received from the vertical pincushion distortion correction waveform generating circuit 6 when the voltage Va is less than the reference voltage and so as to decrease the gain when the voltage Va is more than the reference voltage to keep the amplitude of a parabolic waveform of the vertical pin-cushion distortion correction current constant.