GB1058270A - Convergence circuit for colour tv receivers - Google Patents

Abstract

1,058,270. Cathode-ray tube circuits. MOTOROLA Inc. June 30, 1964 [Aug. 1, 1963], No. 27023/64. Heading H4T. Relates to a vertical dynamic convergence arrangement for a colour picture cathode-ray tube, a convergence coil being energized from a source of vertical beam deflection sawtooth signals so as to develop signals of parabolic waveform in the coil by integration. According to the present invention the sawtooth signals are clipped and thereafter introduced into the convergence coil. It is stated that inherent resistance in a convergence coil inhibits complete integration, and hence correct dynamic convergence, with known arrangements. The embodiment is for a " shadow mask " three-gun colour television receiver picture tube, the corresponding vertical convergence coil sets (12a, 14a, 16a, Fig. 1) influencing respective ones of the three beams at the field rate, the horizontal convergence coils (12b, 14b, 16b) receiving approximately parabolic signals from a low-impedance resonant circuit in known manner. The vertical convergence coils are fed from auxiliary windings (24, 26) on the vertical deflection output transformer (22) and a series resistance path provided by two potentiometers (40, 42) in conjunction with the inductance of the coils affords integration of the sawtooth wave across a resistor (21) in the cathode circuit of the vertical deflection output valve (20) into a parabolic wave. To neutralize the effect of resistance in the convergence coils a diode-resistor path (50, 52) in parallel with the two potentiometers clips adjustable negative portions off that sawtooth wave (Fig. 3, not shown). Another embodiment utilizes two diode-resistor clipping circuits one of which is in parallel with theseries combination of the " red " and " green " vertical convergence coils and the other of which is in parallel with the " blue " convergence coils (Fig. 2, not shown).