US4834504A
Expired / Lapsed
US
⏱️ 0.0 years remaining
LCD compensation for non-optimum voltage conditions
Assignee: HP Inc
•
Filing: 1987-10-09
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Granted: 1989-05-30
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Expires: 2007-10-09
Abstract
Abstract A liquid crystal display (LCD) compensation circuit, operating within a peak voltage limitation, serves to maximize the on/off voltage ratio applied to the LCD while at the same time meeting the LCD threshold voltage specification to thereby optimize the appearance of the liquid crystal display at all times.
Inventors
- 👤 Grant K. Garner
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 08:08
CPC Classifications
G; G02; G02F; G02F1/00; G02F1/01; G02F1/13; G02F1/133; G09; G09G; G09G3/00; G09G3/04; G09G3/16; G09G3/18; G05; G05F; G05F1/00; G05F1/10; G05F1/625; G09G3/20; G09G3/34; G09G3/36
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
136 words
A passive matrix liquid crystal display compensation circuit, the circuit comprising: reference voltage source means for supplying a desired reference voltage to be applied to the passive matrix liquid crystal display; summer means having a first summing input for receiving the reference voltage, having a second summing input, and having an output providing a step voltage; peak voltage function generator means having an input for receiving the step voltage and having an output that provides a source of peak voltage; and feedback function generator means having an input for receiving the peak voltage and having an output connected to the second summing input of the summer means, the summer means being thereby operative for subtracting the output of the feedback function generator means from the reference voltage to produce a continuously updated value of step voltage.
Claim 2
Dependent Claim
136 words
A passive matrix liquid crystal display compensation circuit, the circuit comprising: reference voltage source means for supplying a desired reference voltage to be applied to the passive matrix liquid crystal display; summer means having a first summing input for receiving the reference voltage, having a second summing input, and having an output providing a step voltage; peak voltage function generator means having an input for receiving the step voltage and having an output that provides a source of peak voltage; and feedback function generator means having an input for receiving the peak voltage and having an output connected to the second summing input of the summer means, the summer means being thereby operative for subtracting the output of the feedback function generator means from the reference voltage to produce a continuously updated value of step voltage.
Claim 3
Dependent Claim
22 words
A liquid crystal display compensation circuit as in claim 1 wherein the peak voltage function generator means comprises a constant voltage source.
Claim 4
Dependent Claim
21 words
A liquid crystal display compensation circuit as in claim 1 wherein the peak voltage function generator means comprises a voltage multiplier.
Claim 5
Dependent Claim
27 words
A liquid crystal display compensation circuit as in claim 1 wherein the output of the feedback function generator means is a defined fractional function of its input.
Claim 6
Dependent Claim
19 words
A liquid crystal display compensation circuit as in claim 4 wherein the defined fractional function is equal to 0.28.
Claim 7
Dependent Claim
28 words
A liquid crystal display compensation circuit as in claim 1 wherein the output of the feedback function generator means is a defined square root function of its input.
Claim 8
Dependent Claim
29 words
A liquid crystal display compensation circuit as in claim 1 wherein the output of the feedback function generator means is related to its input by a multiple of 0.28.
Claim 9
Dependent Claim
25 words
A liquid crystal display compensation circuit as in claim 1 wherein the summer means and the feedback function generator means comprise a resistor summing amplifier.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1992-05-29 | 1992-11-28 | 1993-05-30 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1996-05-29 | 1996-11-28 | 1997-05-30 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2000-05-29 | 2000-11-28 | 2001-05-30 | $7700.00 | Window Closed / Lapsed |