Electric lamp and discharge devices: systems – Cathode ray tube circuits – Cathode-ray deflections circuits
Reexamination Certificate
1999-02-08
2001-08-14
Wong, Don (Department: 2821)
Electric lamp and discharge devices: systems
Cathode ray tube circuits
Cathode-ray deflections circuits
C315S369000, C315S408000, C315S411000
Reexamination Certificate
active
06274989
ABSTRACT:
The invention relates to a dynamic clamping arrangement of a deflection circuit.
A television receiver, computer or monitor may have the capability of selectively displaying picture information in the same color cathode ray tube (CRT) using a deflection current at different horizontal scan frequencies. Typically, an S-capacitor is coupled to a horizontal deflection winding of a horizontal deflection circuit output stage to correct a deflection related beam landing error referred to as S correction.
A horizontal rate synchronizing signal that controls the horizontal deflection circuit may be subject to an abrupt phase change in a horizontal period that occurs, during the vertical blanking interval. Such abrupt phase change may be, for example, deliberately introduced to thwart unauthorized video recording of the video signal. Consequently, the stored energy in an inductance coupled to the supply voltage of the horizontal deflection circuit output stage may temporarily increase.
The increased stored energy is subsequently dissipated. However, disadvantageously, the return to steady state operation may be accompanied with ringing in currents and voltages produced in the horizontal deflection circuit output stage. A resistor-capacitor-diode (RCD) clamp coupled across the S-capacitance has been used to reduce such ringing by forcing the horizontal deflection circuit output stage to operate near critical damping.
Another type of distortion that is corrected is referred to as East-West or pincushion distortion. A known way of providing East-West distortion correction is to vary the magnitude of the supply voltage of the horizontal deflection circuit output stage at a vertical rate parabolic manner for modulating the horizontal deflection current. The magnitude of the supply voltage is controlled in a conventional way, in accordance with a vertical rate parabola signal. In such an arrangement, the extent of damping provided by the aforementioned RCD clamp coupled across the S-capacitance may, undesirable, vary as the supply voltage varies, during vertical scanning. It may be desirable to reduce the sensitivity of the damping to the supply voltage vertical rate variations.
In carrying out an inventive feature, the pair of terminals of the clamp capacitor of the RCD clamp is coupled between the supply voltage and the S-capacitance. Each terminal of the clamp capacitor develops equal magnitude of vertical rate parabola component. Consequently, the voltage difference developed between the terminals of the clamp capacitor does not include any vertical rate parabola component. Therefore, the sensitivity of the damping to the supply voltage vertical rate variations is, advantageously, eliminated or reduced.
A video display deflection apparatus, embodying an aspect of the invention includes a source of an input signal at a frequency related to a horizontal deflection frequency. A horizontal deflection winding is coupled to a retrace capacitance and to a switch, responsive to the first input signal, for generating a horizontal deflection current in the horizontal deflection winding. An S-shaping capacitor is coupled to the horizontal deflection winding for developing a voltage in the S-shaping capacitor that varies in a manner to provide horizontal linearity distortion correction. A source of a second signal that varies at a frequency related to a vertical deflection frequency is coupled to the S-shaping capacitor for varying the S-shaping capacitor voltage in accordance therewith for providing East-West distortion correction. A third capacitor is coupled to a rectifier to form a clamp circuit for clamping the S-shaping capacitor voltage, during a portion of a horizontal period. The third capacitor has a first terminal coupled to the S-shaping capacitor and a second terminal coupled to the second signal source for developing, from the second signal, voltage variations at each of the first and second terminals of the third capacitor that compensate each other.
REFERENCES:
patent: 3349279 (1967-10-01), Schafft
patent: 3895305 (1975-07-01), Longman, Jr.
patent: 4019093 (1977-04-01), Klein
patent: 4130783 (1978-12-01), de Hollander
patent: 4533855 (1985-08-01), Willis et al.
patent: 4612481 (1986-09-01), Storberg
patent: 4695774 (1987-09-01), Gent et al.
patent: 4707640 (1987-11-01), Onozawa et al.
patent: 4761586 (1988-08-01), Wharton
patent: 5010281 (1991-04-01), Rodriguez-Cavazos
patent: 5182504 (1993-01-01), Haferl
patent: 5402044 (1995-03-01), Haferl
patent: 6111371 (2000-08-01), Aaron et al.
patent: 6114817 (2000-09-01), Fernsler
Chen Shih-Chao
Fried Harvey D.
Henig Sammy S.
Tripoli Joseph S.
Wong Don
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