DYNAMIC FOCUSING CIRCUIT, PICTURE DISPLAY DEVICE AND METHOD OF GENERATING A DYNAMIC FOCUSING VOLTAGE

摘要

The invention relates to a dynamic focusing circuit (100) for generating a line-frequency dynamic focusing voltage (Vl1) which can be used to control a DAF section (220) of a cathode ray tube (CRT). The dynamic focusing circuit (100) receives a line deflection current (Idl) and transforms and integrates said current so as to obtain the line-frequency focusing voltage (Vl1). The dynamic focusing circuit also generates a further line-frequency focusing voltage (Vl2) and adds this voltage to the line-frequency focusing voltage (Vl1). By applying the invention, the line-frequency focusing voltage (Vl1) is suitable for dynamically focusing the electron beam (201) in a cathode ray tube (CRT) with a relatively large deflection angle of, for example, 120 DEG . It has both a sufficient amplitude and a suitable shape, for example, a bathtub shape.