Patent US4891564A successfully refreshed from Google Patents.
US4891564A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Dynamic focus circuit
Assignee: US Philips Corp
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Filing: 1989-01-23
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Granted: 1990-01-02
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Expires: 2009-01-23
Abstract
Abstract A dynamic beam current focussing circuit for providing improved focussing across the screen of a cathode ray video display tube utilizes a tuned voltage step-up transformer to achieve sufficient amplitude of horizontal sweep waveform components of the dynamic focussing voltage. The circuit is useful for high definition television and video display units.
Inventors
- 👤 Gregory T. B. Crowley
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 20:56
CPC Classifications
H; H04; H04N; H04N3/00; H04N3/10; H04N3/16; H04N3/26
Claims Analysis
Total Claims: 4
Claim 1
Independent Claim
207 words
A circuit for producing a dynamic focussing voltage varying at vertical and horizontal sweep frequencies for a cathode ray tube video display, comprising: a collector voltage modulator having an input to which is applied a pulse waveform voltage at said horizontal sweep frequency, said modulator including a transistor amplifier in which a collector voltage of the transistor amplifier is modulated at said vertical sweep frequency, and a supply circuit for said transistor amplifier, said supply circuit including a series voltage regulator which is dynamically controlled by a parabolic waveform voltage at said vertical sweep frequency; a resonant voltage step-up transformer to which an output current of the modulator is applied, said resonant voltage step-up transformer producing a sinusoidal waveform voltage, a further parabolic waveform voltage at said vertical sweep frequency also being supplied to said resonant voltage step-up transformer in summing relation with a sinusoidal voltage resulting from the output current of the modulator thereby producing a dynamic focus voltage including both sinusoidal horizontal and parabolic vertical frequency waveform components, said components being individually adjustable with respect to each other; and a clamping circuit for superimposing and clamping said dynamic focus voltage onto a direct current focussing voltage to provide said dynamic focussing voltage for overall-screen focus.
Claim 2
Dependent Claim
207 words
A circuit for producing a dynamic focussing voltage varying at vertical and horizontal sweep frequencies for a cathode ray tube video display, comprising: a collector voltage modulator having an input to which is applied a pulse waveform voltage at said horizontal sweep frequency, said modulator including a transistor amplifier in which a collector voltage of the transistor amplifier is modulated at said vertical sweep frequency, and a supply circuit for said transistor amplifier, said supply circuit including a series voltage regulator which is dynamically controlled by a parabolic waveform voltage at said vertical sweep frequency; a resonant voltage step-up transformer to which an output current of the modulator is applied, said resonant voltage step-up transformer producing a sinusoidal waveform voltage, a further parabolic waveform voltage at said vertical sweep frequency also being supplied to said resonant voltage step-up transformer in summing relation with a sinusoidal voltage resulting from the output current of the modulator thereby producing a dynamic focus voltage including both sinusoidal horizontal and parabolic vertical frequency waveform components, said components being individually adjustable with respect to each other; and a clamping circuit for superimposing and clamping said dynamic focus voltage onto a direct current focussing voltage to provide said dynamic focussing voltage for overall-screen focus.
Claim 3
Independent Claim
109 words
A method for producing a dynamic focussing voltage for the beam current of a cathode ray video display tube comprising the steps: amplitude modulating a pulse waveform voltage, of horizontal sweep frequency periodicity, by a parabolic waveform voltage of vertical sweep frequency; stepping-up the amplitude of said modulated waveform voltage; adding said stepped-up modulated waveform voltage to a parabolic waveform voltage at the vertical sweep frequency thereby forming a dynamic force voltage; and clamping said dynamic force voltage to a static focussing voltage thereby forming a dynamic focussing voltage for facilitating improved focussing of the cathode ray tube beam current at all points on the screen of the tube.
Claim 4
Independent Claim
109 words
A method for producing a dynamic focussing voltage for the beam current of a cathode ray video display tube comprising the steps: amplitude modulating a pulse waveform voltage, of horizontal sweep frequency periodicity, by a parabolic waveform voltage of vertical sweep frequency; stepping-up the amplitude of said modulated waveform voltage; adding said stepped-up modulated waveform voltage to a parabolic waveform voltage at the vertical sweep frequency thereby forming a dynamic force voltage; and clamping said dynamic force voltage to a static focussing voltage thereby forming a dynamic focussing voltage for facilitating improved focussing of the cathode ray tube beam current at all points on the screen of the tube.
References Cited (Backward Citations)
US4611151A
Cited
US4683405A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1993-01-01 | 1993-07-03 | 1994-01-02 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1997-01-01 | 1997-07-03 | 1998-01-02 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2001-01-01 | 2001-07-03 | 2002-01-02 | $7700.00 | Window Closed / Lapsed |