| 摘要 |
<p> A dynamic focus circuit for a television display picture tube provides a focus voltage having scan rate modulation. The parabolically shaped voltage which is produced across the S-shaping capacitor (116) in a deflection system is coupled by a transformer (130) having a primary winding (132) coupled between the junction (118) of the S-shaping capacitor (116) and the deflection winding (114), and a power supply point (120) having substantially the same average DC potential. Therefore, substantially no DC current flows through the transformer primary winding (132), which permits a relatively small transformer to be used without saturation of the magnetic core and without the need for a coupling capacitor for DC isolation.</p> |
