Patent ID: 6018222
Filing Date: 2000-01-25
Classification: H04N

Abstract:
A dynamic focusing circuit comprising:an output (1) for supplying a dynamic focusing voltage (Vf) to a focus electrode of a cathode ray tube (CRT),a first transistor (T1) having a main current path (c1, e1) coupled between a supply voltage (V+) and said output (1), and a control input (b1),a current supplying means (2) coupled to said control input (b1) for supplying a bias current (Ib), anda second transistor (T2) with a control electrode (b2) coupled to receive an input voltage (Vi) related to a parabolically shaped input waveform (Vin), and a main 10 terminal (c2) coupled to said control input (b1) for withdrawing current (Id) from said control input (b1),characterized in that the current supplying means (2) comprise:an arrangement of a secondary winding (Ls) of a transformer (T) and a current determining means (12), said arrangement (Ls, 12) being coupled between said control input (b1) and said output (1).