EP1353317A2 - Procédé et appareil servant a réduire l'intensité lumineuse d'une lampe dans un éclairage d'arrière-plan d'un affichage a cristaux liquides - Google Patents

Procédé et appareil servant a réduire l'intensité lumineuse d'une lampe dans un éclairage d'arrière-plan d'un affichage a cristaux liquides Download PDF

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Publication number
EP1353317A2
EP1353317A2 EP20030252088 EP03252088A EP1353317A2 EP 1353317 A2 EP1353317 A2 EP 1353317A2 EP 20030252088 EP20030252088 EP 20030252088 EP 03252088 A EP03252088 A EP 03252088A EP 1353317 A2 EP1353317 A2 EP 1353317A2
Authority
EP
European Patent Office
Prior art keywords
illumination sources
intensity level
display
dimming
predetermined intensity
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP20030252088
Other languages
German (de)
English (en)
Inventor
Joe Miseli
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Sun Microsystems Inc
Original Assignee
Sun Microsystems Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Sun Microsystems Inc filed Critical Sun Microsystems Inc
Publication of EP1353317A2 publication Critical patent/EP1353317A2/fr
Withdrawn legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B41/00—Circuit arrangements or apparatus for igniting or operating discharge lamps
    • H05B41/14—Circuit arrangements
    • H05B41/36—Controlling
    • H05B41/38—Controlling the intensity of light
    • H05B41/40—Controlling the intensity of light discontinuously
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B41/00—Circuit arrangements or apparatus for igniting or operating discharge lamps
    • H05B41/14—Circuit arrangements
    • H05B41/36—Controlling
    • H05B41/38—Controlling the intensity of light
    • H05B41/39—Controlling the intensity of light continuously
    • H05B41/392—Controlling the intensity of light continuously using semiconductor devices, e.g. thyristor
    • H05B41/3921—Controlling the intensity of light continuously using semiconductor devices, e.g. thyristor with possibility of light intensity variations
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2320/00—Control of display operating conditions
    • G09G2320/06—Adjustment of display parameters
    • G09G2320/0606—Manual adjustment
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2320/00—Control of display operating conditions
    • G09G2320/06—Adjustment of display parameters
    • G09G2320/0626—Adjustment of display parameters for control of overall brightness
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2330/00—Aspects of power supply; Aspects of display protection and defect management
    • G09G2330/02—Details of power systems and of start or stop of display operation
    • G09G2330/021—Power management, e.g. power saving
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2330/00—Aspects of power supply; Aspects of display protection and defect management
    • G09G2330/02—Details of power systems and of start or stop of display operation
    • G09G2330/026—Arrangements or methods related to booting a display
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
    • G09G3/34—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source
    • G09G3/3406—Control of illumination source

Definitions

  • the present invention relates generally to managing the brightness of displays such as flat-panel displays.
  • LCDs are fundamentally transmissive devices, requiring a backlight assembly to produce light that is then either transmitted or blocked on a pixel-by-pixel basis. This is typically done by forming a light distribution system behind the LCD pixels that extends the full length and width of the pixel array.
  • the backlight can simply be a reflector for collecting light that comes from the front of the display and redirecting it back out (typically called reflective or transflective displays), but for high-quality AM-TFT-LCDs the source of the light in the backlight is usually one or more fluorescent lamps of various sizes or shapes, usually of the type CCFL (Cold Cathode Fluorescent Lamp), also called CCFT (Cold Cathode Fluorescent Tube).
  • CCFL Cold Cathode Fluorescent Lamp
  • CCFT Cold Cathode Fluorescent Tube
  • CCFTs are high voltage AC devices that need special circuits to produce the required voltages and frequencies to drive them properly.
  • CCFTs are high voltage AC devices that need special circuits to produce the required voltages and frequencies to drive them properly.
  • large ballast devices are commonly used for driving the lamps at 50 or 60Hz.
  • additional demands require sophisticated solutions to problems such as having a low voltage DC source, small size requirements for implementation, higher frequencies to ensure no optical interference with the display, and preferably a wide range of dimming.
  • LCD displays may be used in dim environments, and the default output can be quite bright for some users.
  • LCD displays cannot be dimmed over a range comparable to standard CRT displays, yet their brightness can be several times that of CRTs.
  • the most common method of dimming the CCFTs for most high-quality LCD assemblies is an inverter, an inverse method of common power conversion, in that it takes DC as its input and converts it to AC output.
  • Common inverters are used to convert automobile battery voltages to AC 115 voltages, such as for using normal home appliances in vehicles. In these cases, output level control is rarely needed, and if so, then only over a limited voltage range.
  • the inverter used for CCFTs for LCDs is typically much more specialized, taking DC levels and converting them to high AC voltages, usually well over 1kVolt, with a waveform optimized for the types of fluorescent lamps or other illumination sources for which they were designed. Unlike their vehicle counterparts, these inverters are generally required to provide a wide range of dimming. This is quite a challenging task, and the dimming limits are usually much less than would be desired. This can have a number of negative effects, as will be explained in more detail below.
  • inverter dimming methods there are two types. The first is direct AC supplied voltage amplitude attenuation, and the second involves temporal signal processing, such as by chopping the lamp waveform, like PWM (pulse-width modulation).
  • PWM pulse-width modulation
  • FIG. 1 is a front view of a display 100 in accordance with one embodiment of the invention.
  • Display 100 includes a screen 105 disposed within a housing 110, which may be mounted on a base 115 or a multitude of other arrangements.
  • the screen 105 may comprise a screen requiring a backlight for proper display, such as an LCD or TFT-LCD screen or any other type of transmissive display technology as is known in the art or may be developed.
  • the display 100 includes circuitry 125 containing a processor, memory, and associated circuitry as is known in the art for operating the display 100 as described herein.
  • the display 100 also includes connectors and circuitry (not shown) known in the art for interfacing with sources of video, such as computers.
  • the dimming method described herein may be implemented by way of discrete circuitry as is known in the art. Alternatively, the dimming method may be implemented as a microprocessor-based solution, typically with machine-readable instructions stored in the circuitry 125. The process may also be implemented as a combination of both discrete circuitry and software as desired.
  • the display 100 also includes a ballast 130 for driving CCFTs 120.
  • CCFTs 120 With the advent of larger high quality LCDs, such as used for monitors, wall-mounted displays, home entertainment, etc., more illuminance may be desired. In order to generate this high brightness, often the number of CCFTs is increased to 2, 4, 6, 8 or even more.
  • the lamps are distributed in pairs, such as pair 120a, such that one pair member is deployed about the top or side of the display at the edge of the light distribution system, known as the backlight (not shown), with the other pair member deployed on the opposite side of the display. Such an arrangement can more evenly distribute the light across the light distribution system.
  • the lamps may also be distributed in a non-symmetrical manner, such as on various sides, in the rear of the LCD (rather than top, bottom, or side lit). Futhermore, the lamps may comprise non-conventional CCFT light sources, including serpentine or random configurations, flat lamps, LEDs, ELs or other types of light-generating sources, including potentially a combination of illumination sources of different types or technologies. Other potential methods of generating light in the backlight assembly include various types of incandescent arrays, and even pixelated emissive sources as in other display types, and so forth.
  • pairs of lamps are utilized by taking advantage of their numbers and selectively turning some off, while leaving others lit, so as to minimize the amount of dimming work done by the inverters or other types of lamp controllers.
  • an analogous approach may be used for any configuration in which multiple light sources are used to comprise an entire backlighting, sidelighting, etc. system.
  • An inverter in existing systems is typically used to drive lamps to their lower extremes using the methods described above, resulting in reduced performance in a number of areas and a limited range of dimming.
  • lamps and other illumination sources typically perform best when driven at some optimum level of operations, often at or near their highest output.
  • the prior art methods generally degrade a lamp's performance by dimming the lamp to low operating levels, thereby reducing the quality of a display compared to having lamps in their optimal (non-dimmed) states.
  • the present approach provides for decreasing the brightness of a display with little degradation of the lamps or their visual quality. It is to be understood that such an approach may used in conjunction with certain known prior art dimming methods, thereby complementing them and extending their range dramatically.
  • one embodiment of the invention uses a conventional inverter dimmer circuit, non-inverter dimmer methods could be used instead where appropriate for the type of illumination source employed.
  • a display may be dimmed by selectively turning off some lamps, often in symmetrical sets, such as pairs, to help balance more easily the luminance distribution.
  • the disclosed methods may potentially decrease the luminance by a factor of n/m, where m is the total number of lamps or light sources, and n is the number turned off. For one example, if a backlight assembly has 6 lamps in 2 balanced sets of 3 and one lamp is turned off in each set, then the resultant luminance output might be 4/6 or 66.7% of the initial brightness, assuming perfect optical transmission and electrical efficiency, and other factors being constant.
  • FIG. 2 illustrates a dimming process in accordance with one embodiment of the invention, typically utilized in conjunction with the display 100 of FIG. 1, which includes a backlight assembly comprising 6 CCFTs 120, with 3 pair members each being disposed about the top and bottom of the display 105, and an inverter 130 configured to dim the output of the display to 50% of its initial luminance level.
  • a backlight assembly comprising 6 CCFTs 120, with 3 pair members each being disposed about the top and bottom of the display 105, and an inverter 130 configured to dim the output of the display to 50% of its initial luminance level.
  • FIG. 2 is a graphical representation of one aspect of the dimming process, with the x-axis representing the overall output intensity of the display. The intensity decreases from the brightest at the left to the dimmest level at the right.
  • the y-axis represents the number of lamps operating, with the level of dimming provided by the dimming circuitry indicated.
  • the display is illuminated to a first intensity state, typically with all lamps on, and the inverter dimming is off, providing the highest output intensity for the display.
  • the inverter drives the lamps down to a predetermined level at marker 210.
  • This level is preferably chosen to provide a satisfactory output while not driving the lamps too close to their degraded performance level. In the example of Figure 2, this level occurs at marker 210, representing about 2/3 or 66% of the lamps' original intensity.
  • a superior result is provided by driving the luminance down only 33%, since the lamps and displays are not being driven close to their degraded performance level.
  • the process continues to marker 220.
  • a pair of lamps preferably one on top and one on the bottom
  • the overall intensity level at marker 220 is preferably close to the overall intensity level at marker 210.
  • the dimming level at marker 210 may also be chosen to correspond to the intensity level provided when a first set of lamps is turned off, and the remaining lamps are being driven at their full output level at marker 220.
  • the inverter is now driving only 4 of the 6 lamps, and the total output luminance is again reduced by about 33%.
  • the conventional dimming method is used again to drive the remaining 4 lamps to approximately 40-50% of their full level. This takes us to the position of marker 240.
  • a next set of lamps is turned off (another pair in this example) at marker 260, and the dimming circuit is reset for maximum output, driving the 2 remaining lamps at full brightness.
  • the dimming level at marker 240 may be chosen to correspond to the intensity level provided when the next set of lamps is turned off (at marker 260).
  • a conventional dimming method may be used to dim the remaining 2 lamps to approximately 50% of their level at marker 280, potentially achieving an overall luminance level of 0.33 x 0.5, or 0.165, i.e. approximately 16.5% of the original output. Note that such a luminance reduction technique provides luminance reduction over a range that is 3 times greater than the 50% range that the dimmer alone is able to provide by dimming all 6 of the lamps together.
  • the specified output levels and level of extending dimming mentioned in respect of the example of Figure 2 will vary with the types of lamps used, the dimmer circuitry employed, or the overall number of lamps or types of illumination sources employed in the display.
  • luminance balancing should be predicted and accounted for in the level of luminance reduction before lamps are turned off. Such balancing may be achieved through an electro-optical prediction of the voltage-luminance transfer function. Alternatively, an empirical characterization of the electro-optical system may be used to determine the luminance levels at which the dimmed level matches the lamp cutoff level.
  • a feedback or loading control as is known in the art may be implemented to allow for balanced drive of illuminated lamps when others are turned off.
  • FIG. 2 shows the lamps being progressively dimmed the same approach may be used to raise or lower the intensity level of the display as the user desires. Additionally, it is contemplated that the system may be configured to store the present intensity state of the display for recall on power up.
  • Figure 3 is another graphical representation of a dimming method in accordance with one embodiment of the present invention.
  • Figure 3 shows the number of illumination sources turned on along the x-axis, and the overall luminance along the y-axis.
  • FIG. 3 again provides an example utilizing 6 lamps as the illumination source, though any illumination source and corresponding dimming circuitry may be employed.
  • the typical range of a prior art dimming method is illustrated in FIG. 3 as the range from marker 300, with all lamps turned on at 100% illumination, to marker 304, where all lamps are dimmed to 50% using the dimming circuitry. This results in a total illumination range of approximately 50%.
  • the range of dimming is increased from marker 300, with all lamps on at 100%, to marker 308, where two lamps are dimmed to 50%, resulting in the ability to dim the display to approximately 16.7% of the total luminance.
  • the staggered dimming method first uses conventional dimming methods to dim the display by 33% to approximately 66% of the total output at marker 302.
  • This level corresponds to the total luminance provided by the display when the first set of two lamps is turned off. As mentioned throughout, this level may be chosen depending on the type and/or number of illumination sources utilized.
  • the dimming circuits When the first set of lamps is turned off, the dimming circuits then provide a range of dimming from marker 302 to marker 306, extending from approximately 66% down to approximately 33% of total output luminance. If it is desired to dim the display down below 33%, the next set of lamps may be turned off, and the range of dimming extended from marker 306 to marker 308, or approximately from 33% to approximately 16.7%.
EP20030252088 2002-04-08 2003-04-02 Procédé et appareil servant a réduire l'intensité lumineuse d'une lampe dans un éclairage d'arrière-plan d'un affichage a cristaux liquides Withdrawn EP1353317A2 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US119929 1987-11-13
US11992902A 2002-04-08 2002-04-08

Publications (1)

Publication Number Publication Date
EP1353317A2 true EP1353317A2 (fr) 2003-10-15

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EP20030252088 Withdrawn EP1353317A2 (fr) 2002-04-08 2003-04-02 Procédé et appareil servant a réduire l'intensité lumineuse d'une lampe dans un éclairage d'arrière-plan d'un affichage a cristaux liquides

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EP (1) EP1353317A2 (fr)
JP (1) JP2004126507A (fr)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE10354238A1 (de) * 2003-11-19 2005-06-30 Loewe Opta Gmbh Energiesparschaltung für Flachdisplaygeräte mit hinterleuchtetem Display
EP1809078A2 (fr) * 2006-01-12 2007-07-18 Patent-Treuhand-Gesellschaft für elektrische Glühlampen mbH Reglage d'intensite des lampes
EP2487535A1 (fr) * 2007-05-20 2012-08-15 3M Innovative Properties Company Paramètres de conception pour des rétroéclairages qui ont une cavité creuse mince et réutilisent la lumière

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP4720376B2 (ja) * 2005-08-26 2011-07-13 パナソニック電工株式会社 照明器具
JP2007294169A (ja) * 2006-04-24 2007-11-08 Toshiba Lighting & Technology Corp Ｌｅｄ照明装置
CN101739958B (zh) * 2008-11-24 2013-08-07 奇美电子股份有限公司 多区域动态背光驱动的装置及其方法

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE10354238A1 (de) * 2003-11-19 2005-06-30 Loewe Opta Gmbh Energiesparschaltung für Flachdisplaygeräte mit hinterleuchtetem Display
EP1809078A2 (fr) * 2006-01-12 2007-07-18 Patent-Treuhand-Gesellschaft für elektrische Glühlampen mbH Reglage d'intensite des lampes
EP1809078A3 (fr) * 2006-01-12 2011-07-13 Patent-Treuhand-Gesellschaft für elektrische Glühlampen mbH Reglage d'intensite des lampes
EP2487535A1 (fr) * 2007-05-20 2012-08-15 3M Innovative Properties Company Paramètres de conception pour des rétroéclairages qui ont une cavité creuse mince et réutilisent la lumière

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Publication number Publication date
JP2004126507A (ja) 2004-04-22

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