US5714842A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Automatic cutoff control for a DC coupled CRT video drive
Assignee: Apple Inc
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Filing: 1995-07-21
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Granted: 1998-02-03
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Expires: 2015-07-21
Abstract
Abstract The present invention, generally speaking, provides for automatic cutoff control in a DC coupled CRT video drive using a low DC supply voltage and circuitry that is lower in power consumption than conventional circuitry for the comparable video performance. A simple, easy to implement solution is achieved with an extremely low component count. Cutoff control response is fast, allowing discontinuous operation of auto cutoff control. In one embodiment of the invention, a cutoff control signal is applied to individual CRT G1 terminals. Fast response cutoff control drive is realized using an IC current source and a single transistor current-to-voltage (CTV) converter. Supply voltage variations on the video driver are clamped via a clamping device to the negative supply voltage of the G1 CTV converter.
Inventors
- 👤 Peter Krause
- 👤 Aik Keong Ong
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 19:25
CPC Classifications
H; H04; H04N; H04N3/00; H04N3/10; H04N3/16; H04N3/24
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
109 words
Apparatus comprising: a video amplifier connected to a first voltage source for producing a video out-put signal; DC coupling means for, during operation, applying said video output signal to a cathode of a CRT; bias means connected to a second voltage source for producing a negative voltage; means for, during operation, applying said negative voltage to a cutoff-control grid of a CRT; and regulating means, including a zener diode, connected between said bias means and said first voltage source for causing variations in said first voltage source to be reflected in a level of said negative voltage so as to reduce beam current variations during operation of said CRT.
Claim 2
Dependent Claim
109 words
Apparatus comprising: a video amplifier connected to a first voltage source for producing a video out-put signal; DC coupling means for, during operation, applying said video output signal to a cathode of a CRT; bias means connected to a second voltage source for producing a negative voltage; means for, during operation, applying said negative voltage to a cutoff-control grid of a CRT; and regulating means, including a zener diode, connected between said bias means and said first voltage source for causing variations in said first voltage source to be reflected in a level of said negative voltage so as to reduce beam current variations during operation of said CRT.
Claim 3
Dependent Claim
20 words
The apparatus of claim 1, further comprising: control means connected to said bias means for automatically varying said negative voltage.
Claim 4
Dependent Claim
51 words
The apparatus of claim 2, further comprising: sense means connected to said cathode for sensing an electron beam current emitted by said cathode and for producing a sense signal proportional to said electron beam current; wherein said control means is responsive to said sense signal for automatically varying said negative voltage.
Claim 5
Dependent Claim
15 words
The apparatus of claim 3, wherein said bias means comprises a current to voltage converter.
Claim 6
Dependent Claim
40 words
The apparatus of claim 4, wherein said control means comprises a control logic circuit and a first adjustable current source, said control logic circuit adjusting a current produced by said first adjustable current source in accordance with said sense signal.
Claim 7
Dependent Claim
45 words
The apparatus of claim 5, wherein said control means is connected to a user adjustable signal and further comprises a second adjustable current source, said control logic circuit adjusting a current produced by said second adjustable current source in accordance with said user adjustable signal.
Claim 8
Dependent Claim
41 words
The apparatus of claim 6, wherein a current produced by said first adjustable current source and a current produced by said second adjustable current source are summed to form a resultant current, which is input to said current to voltage converter.
References Cited (Backward Citations)
US4217525A
Cited
US4218720A
Cited
US4438366A
Cited
US4651064A
Cited
US4894725A
Cited
US5189347A
Cited
US5504538A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 2001-02-02 | 2001-08-04 | 2002-02-03 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2005-02-02 | 2005-08-04 | 2006-02-03 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2009-02-02 | 2009-08-04 | 2010-02-03 | $7700.00 | Window Closed / Lapsed |