Modulating horizontal deflection power supply for pincushion correction

摘要

A horizontal deflection apparatus is provided with a circuit 2 to convert a vertical deflection voltage VD into a crosswise pincushion correction voltage V3in a parabola form, a vertical frequency detecting circuit 4, 5 which detects the frequency of a vertical synchronizing signal and outputs a control signal V4 corresponding to the frequency. An automatic gain control circuit 3 amplifies with the gain controlled by V4, corresponding to the vertical frequency, and outputs a voltage signal V5 in a parabola form with a fixed amplitude for correcting crosswise pincushion distortion. A pulse width modulating circuit 6 modulates a pulse signal synchronized with a horizontal synchronizing signal in response to V5 from the automatic gain control circuit, and a chopper-type power circuit 8 chops a power voltage with the pulse width modulating output and supplies the chopped power voltage to a horizontal output circuit, thereby correcting the crosswise pincushion distortion in response to the voltage signal with the fixed amplitude irrespective of changes of the vertical frequency, and enabling adequate correction of the crosswise pincushion distortion even if the vertical frequency changes. IMAGE