JP2004126507A - Method and apparatus for dimming display by alternative lamp inverter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light source for a flat panel display in which an intensity range of light is wide and brightness is efficiently controlled. <P>SOLUTION: The invention relates to a method and an apparatus for dimming the display having a plurality of illumination sources. The display is preferably constituted in such a manner that a plurality of illumination sources are intensified to a first intensity level, then the illumination sources are dimmed to a preliminarily determined intensity level, a selected number of illumination sources are turned off, and the intensity level of the rest illumination sources is raised to a preliminarily determined intensity level. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present disclosure relates generally to manipulating the brightness intensity of a display, such as a flat panel display.
[0002]
[Prior art]
Background Liquid crystal displays (LCDs) are essentially transmissive devices that require a backlight assembly to generate light by passing or blocking light on a pixel-by-pixel basis. This is typically done by configuring a light distribution system behind the LCD pixels, spanning the entire length and width of the pixel array. Occasionally, a backlight may simply be a reflector that collects and returns light coming from the front of the display (commonly referred to as a reflective or transflective display). However, in high quality AM-TFT-LCDs, the backlight source is typically one or more fluorescent lamps of various sizes or shapes, also referred to as CCFT (cold cathode fluorescent tube). This is a fluorescent lamp of the cold cathode fluorescent lamp type.
[0003]
As LCDs become larger and / or require higher brightness (brightness) in output, increasing the number of CCFTs added has become the standard way to generate more light. This helps to make the display brighter, but increases power consumption, new difficulties in dimming the lamp to a low enough level to compensate for low levels of ambient lighting conditions, etc. Some results occur.
[0004]
CCFTs are high voltage AC devices that require special circuitry to generate the necessary voltages and frequencies to properly drive the device. For CCFTs commonly found for industrial, home / business lighting needs, etc., it is common to use large ballast arrangements to drive the lamp at 50 or 60 Hz. However, for LCD displays, additional demands include having a low voltage DC source, the small size required to implement, higher frequencies to ensure that there is no optical interference with the display, preferably Requires advanced solutions to problems such as a wide dimming range.
[0005]
It is often preferable that the dimming range is wide. This is because LCD displays may be used in dimly lit environments and may be very bright at the default output for some users. Currently, LCD displays cannot be dimmed to the extent comparable to standard CRTs, but brightness can be several times that of CRTs. The most common CCFT dimming method for most high quality LCD assemblies is the inverter. This is the reverse of general power conversion, which takes DC as input and then converts it to AC output. Common inverters are used to convert automotive battery voltage to 115 volts AC, for example, for use with ordinary household appliances in vehicles. In such a case, it is rarely necessary to control the output level, and if necessary, only in a limited voltage range.
[0006]
Inverters used in CCFTs for LCDs are typically much more specialized, taking DC levels and converting them to AC high voltages, typically well above 1 kV. This AC high voltage waveform is optimized for the type of fluorescent lamp or other illumination source for which it was designed. Unlike those for vehicles, these inverters are generally required to have a wide dimming range. This is a very difficult task, and the dimming range is usually much smaller than required and can have many negative effects. This will be described in more detail later.
[0007]
Typically, there are two types of inverter dimming methods. The first is to directly attenuate the AC-supplied voltage amplitude, and the second is to require temporal signal processing such as chopping of a ramp waveform, such as PWM (pulse width modulation). is there.
[0008]
[Problems to be solved by the invention]
However, both of these methods have the disadvantage that limitations arise when dimming the lamp to lower levels. At present, at low levels, undesired side effects, such as uneven output brightness, degraded lamp life, and visual artifacts, such as temporal instability in content displayed on LCD displays, or Optical interference often occurs. In these cases, the control of these side effects is compromised and the dimming range of the lamp is often narrower than desired.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
As those skilled in the art will appreciate, the following description is merely illustrative and does not imply any limitation. Other modifications and improvements will readily occur to those skilled in the art having the benefit of this disclosure. In the description that follows, like reference numerals designate like elements throughout.
[0010]
The present disclosure relates to data communication or processing. The various aspects disclosed may be implemented in various computer and machine readable data structures. Also, data structures embodying the teachings of the disclosure may be transmitted over computer and machine readable media, and will not be subject to standard protocols (such as those used to enable the Internet and other computer networking systems). The transmission may be performed through the communication system by using a standard or the like.
[0011]
The present disclosure relates to a machine-readable medium having various aspects of the disclosure stored thereon. Any suitable medium for retrieving instructions is within the scope of the present disclosure. By way of example, such a medium may take the form of a magnetic, optical or semiconductor medium and may be configured to be accessible by a machine as known in the art.
[0012]
Various aspects of the present disclosure may be described using a flowchart. In many cases, one example of one aspect of the present disclosure is provided. However, as one of ordinary skill in the art will appreciate, the protocols, processes and procedures described herein may be repeated continuously or as often as necessary to meet the needs described herein. May be repeated. Therefore, the description of various aspects of the present disclosure using flowcharts should not be used to limit the scope of the present disclosure.
[0013]
Exemplary embodiments of the disclosed apparatus and method are disclosed herein. The term "exemplary" is used exclusively herein to mean "serving as an example, illustration, or illustration." None of the embodiments described as "exemplary embodiments" should necessarily be construed as necessarily preferred or advantageous over other embodiments described herein.
[0014]
FIG. 1 is a front view of a display 100 suitable for use in the present disclosure. The display 100 includes a screen 105 disposed inside a housing 110. Housing 110 may rest on base 115 or many other devices. The screen 105 comprises a screen that requires a backlight for proper display, for example, an LCD or TFT-LCD screen or any other type of transmissive device known or developed in the art. Type display technology.
[0015]
Display 100 includes circuitry 125 incorporating a processor, memory, and associated circuitry as known in the art, for operating display 100 in accordance with the teachings of the present disclosure. The display 100 also includes connectors and circuits (not shown) known in the art for interfacing with a video source such as a computer. The disclosed dimming methods shall be accomplished by discrete circuits known in the art. Alternatively, the dimming method may be implemented as a microprocessor-based solution, where embodiments are stored in circuit 125 as machine-readable instructions. Further, this process may be realized as a combination of a discrete circuit and software as needed.
[0016]
The display 100 also includes a ballast 130 for driving the CCFT 120. With the advent of larger, higher quality LCDs, such as those used in monitors, wall mounted displays, home entertainment, and the like, higher illuminance may be required. In order to generate such high brightness, the number of CCFTs is often increased to 2, 4, 6, 8, or more. Typically, but not always, the lamps are distributed in pairs, such as pair 120a, and one of the pair elements is located near the top or side of the display, a light distribution system known as a backlight ( (Not shown), and the other of the paired elements is located on the opposite side of the display. Such an arrangement allows for more uniform distribution of light throughout the light distribution system.
[0017]
Although three pairs of CCFTs are shown in FIG. 1, any number of pairs may be used in the present disclosure. Also, the lamps may be distributed in an asymmetric manner (rather than top, bottom or side lighting) on the back of the LCD, for example on various sides, for example in a meandering or random configuration, flat lamps, LEDs , EL, or other types of light emitting sources. It is even possible to make up different illumination sources of different types or technologies.
[0018]
Also, there are many other light emitting methods in the backlight assembly. For example, AC light emitting devices such as LEDs, EL, incandescent arrays of various types, pixelated emission sources as in other display types, and the like. It should also be noted that not all fluorescent lamps are straight, and may not be of a length approximately comparable to the horizontal or vertical width dimension of a side-lighting or back-lighting LCD. It is. The present disclosure applies to any variation or format for LCD illumination where the illumination format includes or is divided into multiple illumination sources (eg, multiple cathode / anode devices, pixelated devices, etc.). can do.
[0019]
The present disclosure makes use of the number of lamp pairs, which can be performed by an inverter or other type of lamp control device, utilizing lamp pairs by selectively turning off some and leaving others lit. Although a method and apparatus for minimizing the amount of dimming work is described, as described above, it can be applied to any configuration using a plurality of light sources to constitute an entire system such as backlighting, side lighting, and the like. It is valid.
[0020]
Typically, inverters are used to drive the lamp to its lower limit using the methods described above, resulting in reduced performance and limited dimming range in many areas. Typically, lamps and other illumination sources perform best when driven at an optimum operating level, often at or near maximum power. Thus, prior art methods degrade the lamp performance by dimming the lamp to a lower operating level, thereby reducing the quality of the display from its optimal (non-dimmed) state.
[0021]
The present disclosure provides for reducing the brightness of the display with little degradation of the lamp or its visual quality. It should be understood that the benefits of the present disclosure can be used in conjunction with other commonly used prior art dimming methods to complement and greatly extend the prior art dimming methods.
[0022]
The present disclosure describes dimming a display by selectively turning off some lamps (often symmetrical pairs, e.g., pairs) to help balance the luminance distribution more easily. provide. The disclosed method can reduce the brightness by a factor of n / m, depending on many light distribution or light transmission properties, configuration dependencies and electronics variables. Here, m is the total number of lamps or light sources, and n is the number turned off. As an example, if the backlight assembly has two sets of six lamps in a balanced set of three, and one lamp is turned off in each set, the resulting luminance output will have full light transmission and Assuming that the electrical efficiency as well as other variables are accurate, it is considered to be 4/6 of the original brightness or 66.7%.
[0023]
Although the present disclosure uses a conventional inverter dimmer circuit in one aspect disclosed, non-inverter dimmer methods can be used if appropriate for the type of illumination source used.
[0024]
FIG. 2 illustrates one aspect of a dimming process in accordance with the teachings of the present disclosure. This aspect is illustrated in connection with the display 100 of FIG. Display 100 comprises six CCFTs 120, a backlight assembly in which three pairs of elements are located near the top and bottom of display 105, respectively, and the output of the display to its initial brightness level. And an inverter 130 configured to diminish to 50% of the above.
[0025]
FIG. 2 is a graphical representation illustrating one aspect of the dimming process, where the x-axis represents the total output intensity of the display. The intensity decreases from the brightest state on the left to the darkest state on the right. The y-axis represents the number of lamps operating at the dimming level provided by the illustrated dimming circuit.
[0026]
At the start of the process of FIG. 2, at sign 200, the display is illuminated to a first intensity state. Typically, the lamps are all on, inverter dimming is off, and the highest output intensity is provided for the display.
[0027]
To initiate dimming of the display intensity level, the inverter drives the lamp down to a predetermined level at the sign 210. This level is preferably selected so that sufficient power is obtained but the lamp is not driven near the performance degradation level. In one embodiment, this level occurs at sign 210 and represents about 2/6 or 33% of the lamp's original intensity. In this example, using a dimmer circuit that can diminish by 50% in total by illuminating at 33% brightness, lamps and displays are not driven near degraded levels, thus providing excellent results for lamps and displays. You.
[0028]
If the display is to be further dimmed, the process continues to sign 220.
At this location, the pair of lamps (preferably one at the top and one at the bottom) are turned off and the inverter is returned to full illumination. Preferably, the total intensity level at sign 220 is close to the total intensity level at sign 210. Thus, the dimming level at the sign 210 is selected to correspond to the intensity level obtained when the first set of lamps at the sign 220 are turned off and the remaining lamps are driven at their maximum power level. Is also good.
[0029]
At sign 220, the inverter is now driving only four of the six lamps, reducing the total output brightness by about 33%.
[0030]
To further dim the display, at sign 240, the remaining four lamps are driven at about 40-50% of that level using conventional dimming methods.
[0031]
To further dim the display, at sign 260, the next set of lamps (in this example, the other two pairs) are turned off, and then the dimming circuit is reset to full power, The remaining two lamps are driven at the maximum brightness.
[0032]
Thus, at sign 260, only two lamps are activated, yielding about 33% of the initial brightness. As described above, the dimming level at sign 240 may be selected to correspond to the intensity level obtained when the next set of lamps is turned off at sign 260.
[0033]
To diminish the display to the lowest output level, at sign 280, the remaining two lamps may be dimmed to about 50% of that level using conventional dimming methods. Potentially, an overall brightness level of 0.33 × 0.5 of the original output, or 0.165 (about 16.5%) is realized.
[0034]
This reduction in brightness using the teachings of the present disclosure reduces the brightness reduction in the 50% range that only the dimmer can provide by dimming all six lamps together by more than three times. Indicates an increase.
[0035]
As will be appreciated by those skilled in the art, the specific power levels and levels that extend the dimming range will depend on the type of lamp used, the dimmer circuit used or the total number of lamps in the illumination source used in the display. Or it changes with the form.
[0036]
As those skilled in the art will appreciate, the disclosed alternating dimming process provides a wide range of brightness, while preserving power and lamp life, and minimizing optical degradation or interference. To keep. This is because the display components are not driven near their individual degradation points.
[0037]
When performing the method normally, the following considerations can guarantee the best performance. For example, in order to minimize any discernible step in brightness when turning off the lamp, the brightness balance must be predicted and compensated for at a reduced level of brightness before turning off the lamp. . Such a balance can be achieved by electro-optical prediction of the voltage-luminance transfer function, or, using experimental characterization of the electro-optical system, the luminance at which the dimming level corresponds to the cut-off level of the lamp. You may ask for a level.
[0038]
In addition, it is known in the art to properly control conventional dimming methods while avoiding unwanted effects such as bleeding, crosstalk, leakage or arcing when the CCFT lamp load is unbalanced. Such feedback or load control may be performed to enable balanced driving of the lit lamp when the other lamp is off.
[0039]
Although the aspect disclosed in FIG. 2 shows a gradual dimming, the disclosed process may be used to raise or lower the intensity level of the display, depending on the needs of the user. Also, the disclosed process may be configured to store the current strength state of the display and to recreate it at startup.
[0040]
FIG. 3 is another graphical representation illustrating a dimming method according to the present disclosure. In FIG. 3, the number of illumination sources turned on is shown on the x-axis and the overall brightness is shown on the y-axis. FIG. 3 also provides an example of using six lamps as the illumination source, although any illumination source and corresponding dimming circuit may be used in the present disclosure.
[0041]
In FIG. 3, a typical range of prior art dimming methods is from a sign 300 that turns on all lamps with 100% illumination to a sign 304 that dims all lamps to 50% using a dimming circuit. Are shown as ranges. This results in a total illumination range of about 50%.
[0042]
Using an alternating dimming method as disclosed herein, the dimming range can be from a sign 300 that turns on all lamps at 100% to a sign that dims two lamps to 50%. 308, so that the display can be dimmed to about 16.7% of the total brightness.
[0043]
As can be seen from FIG. 3, the alternating dimming method first diminishes the display by 33% to approximately 66% of the total power using the conventional dimming method (label 302). . This level corresponds to the total brightness provided by the display when the first set of two lamps is turned off. As mentioned consistently, this level may be chosen depending on the type and / or number of illumination sources used.
[0044]
When the first set of lamps is turned off, the dimming circuit provides a dimming range from sign 302 to sign 306, which extends from about 66% to about 33% of the total output brightness.
[0045]
If it is desired to dimm the display below 33%, the next set of lamps can be turned off and the dimming range extends from sign 306 to sign 308, ie from about 33% to about 16.7%. .
[0046]
While embodiments and applications of the present disclosure have been illustrated and described, it will be apparent to those skilled in the art that many more changes and modifications may be made than described above without departing from the inventive concept herein. Improvements are possible. Accordingly, the disclosure should not be limited except in the spirit of the appended claims.
[Brief description of the drawings]
FIG. 1 is a front view illustrating an LCD display suitable for use with the present disclosure.
FIG. 2 is a graphical representation illustrating a dimming method according to the present disclosure.
FIG. 3 is another graphical representation illustrating a dimming method according to the present disclosure.

Claims (22)

A method for dimming a display having a plurality of illumination sources, comprising:
Brightening the plurality of illumination sources to a first intensity level;
Dimming the plurality of illumination sources to a predetermined intensity level;
Turning off a selected number of said plurality of illumination sources;
Raising the intensity level of the remaining illumination source to approximately the predetermined intensity level;
A method that includes The method of claim 1, wherein the first intensity level corresponds to a maximum intensity capability of the display. The method of claim 1, wherein the predetermined intensity level is a level at which performance degradation of display components is avoided. The method of claim 3, wherein the predetermined intensity level is about 66% of the output of the plurality of lamps. The method of claim 3, wherein the predetermined intensity level is about 50% of the output of the plurality of lamps. An apparatus for dimming a display having a plurality of illumination sources, comprising:
Means for brightening the plurality of illumination sources to a first intensity level;
Means for dimming the plurality of illumination sources to a predetermined intensity level;
Means for turning off a selected number of said plurality of illumination sources;
Means for raising the intensity level of the remaining illumination source to approximately the predetermined intensity level;
An apparatus comprising: The apparatus of claim 6, wherein the first intensity level corresponds to a maximum intensity capability of the display. The apparatus of claim 6, wherein the predetermined intensity level is a level at which performance degradation of display components is avoided. The apparatus of claim 8, wherein the predetermined intensity level is about 66% of the output of the plurality of lamps. The apparatus of claim 8, wherein the predetermined intensity level is about 50% of an output of the plurality of lamps. A machine-readable program storage device that substantially implements a machine-executable instruction program to perform a method of dimming a display having a plurality of illumination sources, the method comprising:
The method comprises:
Brightening the plurality of illumination sources to a first intensity level;
Dimming the plurality of illumination sources to a predetermined intensity level;
Turning off a selected number of said plurality of illumination sources;
Raising the intensity level of the remaining illumination source to approximately the predetermined intensity level;
Including devices. The device of claim 11, wherein the first intensity level corresponds to a maximum intensity capability of the display. The device of claim 11, wherein the predetermined intensity level is a level at which performance degradation of display components is avoided. 14. The device of claim 13, wherein the predetermined intensity level is about 66% of an output of the plurality of lamps. 14. The device of claim 13, wherein the predetermined intensity level is about 50% of an output of the plurality of lamps. A display,
A transmissive pixel array operably disposed on the housing;
A backlight system optically coupled to the array, the backlight system including a plurality of illumination sources arranged in pairs located near the array;
A dimmer circuit operably coupled to the plurality of illumination sources;
With
The dimmer circuit brightens an illumination source to a first intensity level, dims the plurality of illumination sources to a predetermined intensity level, turns off a selected set of the plurality of illumination sources, and A display device configured to raise the intensity level of the illumination source to approximately the predetermined intensity level. 17. The display of claim 16, wherein the plurality of illumination sources include a plurality of CCFTs (cold cathode fluorescent tubes). 17. The display of claim 16, wherein the display is configured to reduce total brightness by a factor n / m, where m is the total number of illumination sources and n is the number of illumination sources turned off. 19. The display according to claim 18, wherein the predetermined intensity level is a level at which performance degradation of display components is avoided. 20. The display of claim 19, wherein the predetermined intensity level is about 66% of an output of the plurality of lamps. 20. The display of claim 19, wherein the predetermined intensity level is about 50% of an output of the plurality of lamps. 19. The display of claim 18, wherein the brightness of the display can be reduced to about 16.7% of the total brightness of the display.

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