CN1475984A - Grey voltage generating method and circuit, and liquid crystal display device - Google Patents
Grey voltage generating method and circuit, and liquid crystal display device Download PDFInfo
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- CN1475984A CN1475984A CNA021305722A CN02130572A CN1475984A CN 1475984 A CN1475984 A CN 1475984A CN A021305722 A CNA021305722 A CN A021305722A CN 02130572 A CN02130572 A CN 02130572A CN 1475984 A CN1475984 A CN 1475984A
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Abstract
A method for generating grayscale voltage in order to improve the display quality of image by use of small-scale circuits and lower energy consumption features that the D/A converter is used for converting the voltage difference between two adjacent grayscale voltages to multiple analog voltages are the adder or subtracter is used to perform addition or substraction between one or two reference voltages and said multiple analog voltages.
Description
Technical field
The present invention relates to a kind of method that is used to produce grayscale voltage, be used to produce circuit and a kind of liquid crystal display device of grayscale voltage; Be particularly related to a kind of being used for by a brightness level is provided to liquid crystal display device, thereby produce the method for a plurality of grayscale voltage display images, and utilize the gray scale of said method to produce circuit and have the liquid crystal display device that this gray scale produces circuit.
Background technology
Fig. 7 is a schematic block diagrams, and the example of structure of disclosed conventional liquid crystal part among the Japanese patent laid-open NO.11-15442 is shown.Above-mentioned liquid crystal display device comprises that mainly LCD 1, controller 2, grayscale voltage produce circuit 3, data driver 4 and scanner driver 5.
This LCD 1 is that for example, one utilizes the active matrix type colour liquid crystal display device of thin film transistor (TFT) (TFT) as on-off element.In this LCD 1, by a plurality of scan electrodes of arranging at line direction with specific interval (sweep trace) and a plurality of data electrode of on column direction, arranging with specific interval (data line) area surrounded as pixel.In each pixel in colour liquid crystal display device 1, arrange to have the pixel electrode that is equivalent to a capacity load, the TFT that a public electrode and is used to drive the respective pixel electrode.In order to drive colour liquid crystal display device 1, when a common electric voltage Vcom (not shown) is added on the public electrode, provide according to the red data D that is digital of digital video data to data line
R, green data D
G, and blue data D
BThe data danger signal of Chan Shenging, data green and data blue signal respectively, and provide according to horizontal-drive signal S to sweep trace
H, vertical synchronizing signal S
VDeng the sweep signal that produces.This has realized the color character or the image that will show on the display screen of colour liquid crystal display device 1.
Grayscale voltage produces circuit 3 and produces eight kinds of grayscale voltage V1-V8, changes the voltage level of each grayscale voltage V1-V8 according to the grayscale voltage setting data DG of outside input.Grayscale voltage setting data D
GBeing used in reference to the start bit that is shown with the starting position of imitating data, 3 by 1 is used to indicate the address bit of address information and is used to indicate 8 bit data positions of voltage value data to form.Any of eight D-A converters (DAC) 121-128 of the grayscale voltage generation circuit 3 that will illustrate below address information is used for selecting to form.In addition, voltage value data is used to change the voltage level of each grayscale voltage V1-V8.
Data driver 4 according to the video data D of delegation of data clock DCK synchronization gain
00-D
07, D
10-D
17, and D
20-D
27From grayscale voltage produces the grayscale voltage V1-V8 of circuit 3 outputs, select a grayscale voltage, and the grayscale voltage that will select offers a corresponding data line in the colour liquid crystal display device 1 as a data danger signal, data green or data blue signal.Scanner driver 5 produces successively with the synchronous sweep signal of scan clock SCK and with the signal that produces and offers corresponding scanning line in the colour liquid crystal display device 1 successively.
Below, 8 explanation grayscale voltages produce the structure of circuit 3 with reference to the accompanying drawings.
Grayscale voltage produces circuit 3 by comprising interface circuit 11, D-A converter (DAC) 12
1-12
8With buffering amplifier 13
1-13
8A LSI (large scale integrated circuit) chip form.Interface circuit 11 has a DAC, and this DAC selects according to address information that import, that form grayscale voltage setting data DG from the outside locking voltage value data of forming grayscale voltage setting data DG.Each DAC12
1-12
8With each DAC12
1-12
8The voltage value data that latchs is converted to aanalogvoltage, and the voltage of output conversion.Each DAC12
1-12
8Output aanalogvoltage be maintained at same level, when new voltage value data is latched by interface circuit 11 till.In this embodiment, owing to each voltage value data is formed by eight, therefore, each DAC12
1-12
8Exportable one amounts to the aanalogvoltage with 256 grades.But the maximal value of aanalogvoltage is set to and allows incoming level or below it.Each buffer amplifier 13
1-13
8To each corresponding DAC12
1-12
8The aanalogvoltage of conversion is carried out electric current and is amplified and impedance transformation, and exports voltage as a result, as grayscale voltage V1-V8.
According to said structure, by carrying out an OS (operating system) or application program, produce circuit 3 input gray level voltage setting data DG from the outside to grayscale voltage, thereby can be to carrying out gray correction, and/or obtain to be fit to the gray scale display characteristic that maybe can mate the image that will show object of consumer taste by the distortion of the gray scale display characteristic that causes with respect to colour liquid crystal display device 1 specific characteristic.
As mentioned above, produce in the circuit 3 each DAC12 at traditional grayscale voltage
1-12
8Independent output one has 256 grades aanalogvoltage altogether, each buffer amplifier 13
1-13
8To each corresponding DAC12
1-12
8The aanalogvoltage of conversion is carried out electric current and is amplified and impedance transformation, and the voltage that produces is offered data driver 4.Then, data driver 4 is according to the video data D of delegation that obtains
00-D
07, D
10-D
17And D
20-D
27, select among the grayscale voltage V1-V8, and the voltage selected offered in the respective data lines in the colour liquid crystal display device 1 one as data danger signal, data green and data blue signal.In other words, in traditional colour LCD device, grayscale voltage produces circuit 3 and data driver 4 all grayscale voltage execution level is not moved or electric current amplifies, therefore grayscale voltage for the level value that can be provided for each data line in the colour liquid crystal display device 1 (for example, 8.5-13V, herein, the level of the grayscale voltage that can be provided is called as " voltage available level ").Therefore, can produce a voltage that is in the voltage available level, need DAC12 for grayscale voltage produces circuit 3
1-12
8With buffering amplifier 13
1-13
8All has a very wide dynamic range.If comprise and have the very DAC12 of wide dynamic range
1-12
8With buffering amplifier 13
1-13
8Grayscale voltage when producing circuit 3 and must utilize a LSI chip to constitute, it is very big that the scale of circuit will become, and can not realize, even it can realize that its cost also can be very high.In addition, thereby when grayscale voltage being carried out level moves or voltage amplification when making grayscale voltage be the voltage available level, owing to move with level or the appearance of the mistake that voltage amplification is relevant, can not produce and have high-precision grayscale voltage, the high-quality image demonstration of also impossible realization.In addition,, grayscale voltage utilize a LSI chip to make, owing to have the very DAC12 of wide dynamic range even producing circuit 3
1-12
8With buffering amplifier 13
1-13
8It is very big to consume energy, colour LCD device in the above-mentioned example also can not be used in the display that is used for by battery-driven portable electron device, as notebook computer, palm PC and pocket computer, PDA (personal digital assistant), portable cell phone, PHS (individual palm telephone system) etc.
In addition, some data drivers generations can produce a series of grayscale voltages by the grayscale voltage of cutting apart 3 outputs of grayscale voltage generation circuit.Here, in order to distinguish the grayscale voltage that grayscale voltage that grayscale voltage circuit 3 produces and data driver 4 produce, the latter is called " application grayscale voltage ".After having produced a series of application grayscale voltages, under normal conditions, grayscale voltage for example, provides eight grayscale voltage V1-V8 to the corresponding contact point of the resistor ladder that is formed by a plurality of resistance cascades.Therefore, the relation between the grayscale voltage V1-V8 is shown in following expression formula (1).
GND＜V1＜V2＜V3＜V4＜V5＜V6＜V7＜V8＜V
DD... (expression formula 1)
Wherein, V
DDThe expression supply voltage, GND represents ground voltage.Hereinafter, expression formula (1) is called as " initial conditions of data driver ".
But, as mentioned above, because each DAC12
1-12
8Must export an aanalogvoltage with applied voltage level, when grayscale voltage produces circuit 3 by practical application, need satisfy the initial conditions of data driver, and set grayscale voltage setting data D
GThereby, make grayscale voltage be in the voltage available level.Therefore, traditional grayscale voltage produces circuit 3 uses and inconvenient.
And, under normal conditions, the dislocation of DAC be approximately scale-of-two LSB (least significant bit (LSB)) ± 1.On the other hand, as mentioned above, each DAC12
1-12
8Output one has the aanalogvoltage of voltage available level.Thereby, each DAC12
1-12
8Bit-errors become big, this makes that producing high-precision grayscale voltage becomes impossible, and is difficult to obtain high quality graphic.
Here, the potential difference (PD) that produces when hypothesis between the black level voltage (hereinafter being called " minimum luminance voltage ") of the white level voltage (hereinafter being called " maximum grayscale voltage ") of the highest gray scale and generation minimal gray level is 4.5V, when 8 digital of digital video data will be displayed on the colour liquid crystal display device 1, the voltage V1 of gray level was provided by expression (2).
V1=4.5[V]/256=17.6[mV] ... .. expression formula (2)
Therefore, the output error ER of DAC is provided by expression (3).
ER=17.6[mV] * 2=35.2[mV] .... expression formula (3)
On the other hand, in LCD 1, usually, and if the change in voltage that offers on the data line is 20[mV], as seen the then variation in the image will become as the irregular of grayscale voltage.Therefore, the output error ER of DAC must be less than 20[mV].But produce in the circuit 3 at above-mentioned traditional grayscale voltage, as shown in expression formula (3), output error ER is 35.2[mV], thus make irregular becoming as seen in the grayscale voltage.For example, in Fig. 9, when showing that in colour liquid crystal display device 1 display brightness is from the left part image that increases of partial linear when (this image is called as " gray level image ") to the right, if adopted above-mentioned traditional grayscale voltage to produce circuit 3, though then original gray scale should partly progressively increase to the right from the left side, but in fact, the gray scale on right side becomes less than the gray scale in left side, and also shows a vertical bar on the display screen.Because this defective, the liquid crystal display device that utilizes traditional grayscale voltage to produce circuit can not be used to the display device of medical electronic device, and particularly those need in the image demonstration of high definition.
Technical scheme
Consider mentioned above, an object of the present invention is to provide a kind of circuit that is used to produce the method for grayscale voltage and is used to produce grayscale voltage, this Method and circuits can utilize small scale in circuitry to realize that high-quality image shows and can reduce the loss of electric energy, and the liquid crystal display device that utilizes said method and circuit, it can realize convenient satisfied use.
According to a first aspect of the invention, provide a kind of by a brightness level is provided to liquid crystal display device, thereby produce the grayscale voltage production method of a plurality of grayscale voltage display images, this method comprises:
After a plurality of digital data conversion of the voltage difference in a plurality of grayscale voltages with correspondence between any two grayscale voltages are aanalogvoltage, but carry out operational computations to an aanalogvoltage and a reference voltage or to any at least two aanalogvoltages, thereby produce a plurality of grayscale voltages.
In aforementioned, an optimal mode is that reference voltage is the voltage corresponding to the maximal value or the minimum value of each grayscale voltage.
And, be addition or subtraction but an optimal mode is characterized in that operational computations.
And an optimal mode is characterized in that a plurality of grayscale voltages are made up of the grayscale voltage of a plurality of positive polaritys and the grayscale voltage of a plurality of negative polarity.
And, but an optimal mode is characterized in that the operational computations of being undertaken by the reference voltage that utilizes identical value producing the grayscale voltage of a plurality of positive polaritys and the grayscale voltage of a plurality of negative polarity.
According to a second aspect of the invention, provide a kind of by a brightness level is provided to liquid crystal display device, thereby the grayscale voltage that produces a plurality of grayscale voltage display images produces circuit, comprising:
A plurality of D-A converters, the digital data conversion that is used for the voltage difference between two grayscale voltages of each corresponding a plurality of grayscale voltage is an aanalogvoltage; With
But a plurality of operational computations unit, but be used for carrying out operational computations to an aanalogvoltage and reference voltage or at least two any aanalogvoltages.
In aforementioned, an optimal mode is characterized in that: reference voltage is the voltage corresponding to the maximal value or the minimum value of each grayscale voltage.
And an optimal mode is characterized in that: but the operational computations unit is totalizer or subtracter.
And an optimal mode is characterized in that: a plurality of grayscale voltages are made up of a plurality of positive polarity grayscale voltages and a plurality of negative polarity grayscale voltage.
And an optimal mode is characterized in that: but the operational computations of the reference voltage by utilizing identical value produces a plurality of positive polarity grayscale voltages and a plurality of negative polarity grayscale voltage.
And, one optimal mode is characterized in that: comprise a memory storage, in this memory storage, store a plurality of numerical datas in advance, provide circuit with data, be used for when power supply is provided, from memory storage, read a plurality of numerical datas, and the numerical data of reading is input in each D-A converter.
According to a third aspect of the invention we, provide a kind of liquid crystal display device, thereby the grayscale voltage that this device has by a brightness level, a plurality of grayscale voltage display images of generation are provided to liquid crystal display device produces circuit, this grayscale voltage produces circuit and comprises:
A plurality of D-A converters, the digital data conversion that is used for the voltage difference between two grayscale voltages of each corresponding a plurality of grayscale voltage is an aanalogvoltage; With
But a plurality of operational computations unit, but be used for carrying out operational computations to an aanalogvoltage and a reference voltage or at least two any aanalogvoltages.
By said structure, can utilize small scale in circuitry to realize that high-quality image shows, and cut down the consumption of energy, realize satisfied facility use.
Description of drawings
Above and other objects of the present invention, advantage and feature all will become clear from the description below in conjunction with accompanying drawing, wherein:
Fig. 1 is a schematic block diagrams, shows the structure of grayscale voltage generation circuit in the first embodiment of the invention;
Fig. 2 is a schematic block diagrams, shows the structure of having used grayscale voltage to produce the liquid crystal display device of circuit in the first embodiment of the invention;
Fig. 3 is a table, shows the example of the relation between the address bit and DAC in the first embodiment of the invention;
Fig. 4 is a schematic block diagrams, shows the structure of grayscale voltage generation circuit in the second embodiment of the invention;
Fig. 5 is a schematic block diagrams, shows the structure of grayscale voltage generation circuit in the third embodiment of the invention;
Fig. 6 is a curve, shows the example of the relation between the grayscale voltage and brightness in general liquid crystal display;
Fig. 7 is a schematic block diagrams, shows the example of structure of disclosed conventional liquid crystal part among the open flat 11-15442 of NO. of Jap.P.;
Fig. 8 is a schematic block diagrams, shows the example of structure that the grayscale voltage of forming the conventional liquid crystal device produces circuit; With
Fig. 9 is a chart, shows the demonstration example of a gray level image.
Most preferred embodiment
Utilize different embodiment more detailed descriptions to realize optimal mode of the present invention below with reference to accompanying drawings.First embodiment
Fig. 2 is a schematic block diagrams, shows the structure of having used grayscale voltage to produce the liquid crystal display device of circuit 21 in the first embodiment of the invention; In Fig. 2, except grayscale voltage produces circuit 3 and data driver 4, represent to have the corresponding component of identical function, and newly added grayscale voltage generation circuit 21 and data driver 22 with Reference numeral identical among Fig. 7.
Grayscale voltage produces the grayscale voltage V that circuit 21 has produced eight kinds of positive polaritys
P1-V
P8Grayscale voltage V with eight kinds of negative polarity
N1-V
N8, and according to the grayscale voltage setting data D of outside input
G, change each grayscale voltage V
P1-V
P8With each grayscale voltage V
N1-V
N8Voltage level.Grayscale voltage V
P1-V
P8Between relation shown in following expression formula (4), grayscale voltage V
N1-V
N8Between relation shown in following expression formula (5).
V
REF＜V
P1＜V
P2＜V
P3＜V
P4＜V
P5＜V
P6＜V
P7＜V
P8.... expression formula (4)
V
REF＞V
N1＞V
N2＞V
N3＞V
N4＞V
N5＞V
N6＞V
N7＞V
N8.... expression formula (5)
V wherein
REFThe expression reference voltage also equals a for example common potential Vcom.
Thereby grayscale voltage produces circuit 21 structure generation grayscale voltage V like this in the present embodiment
P1-V
P8With grayscale voltage V
N1-V
N8Reason as follows.Here it is, in LCD, usually, when the voltage of identical polar is constantly offered liquid crystal cells, even power supply is closed, so-called " adhesion " phenomenon can take place also, and this phenomenon is that track such as character is persisted on video screen.In order to address the above problem, usually, adopts the method for the method of the method for the method of so-called " some inversion driving method ", so-called " line inversion driving method " and so-called " frame inverting method " as the driving LCD.In an inversion driving method, provide a data-signal that the polarity of the voltage that offers pixel electrode of each point pixel is reversed with respect to the common potential Vcom that offers public electrode to data line.In addition, in the online inversion driving method, provide one to make the polarity of the voltage that offers pixel electrode of each line to data line with respect to the data-signal of the common potential Vcom counter-rotating that offers public electrode, applying of while response data signal, common potential Vcom is reversed to ground voltage level (GND) or mains voltage level.In addition, in the frame inversion driving method, provide a data-signal that the polarity of the voltage that offers pixel electrode of each line is reversed with respect to the common potential Vcom that offers public electrode to data line, simultaneously, relatively with each line and each frame, applying of response data signal, counter-rotating common potential Vcom.When adopting these driving methods, in LCD, under normal conditions, even offering the voltage level of liquid crystal cells is inverted, because liquid crystal has transmissison characteristic much at one, therefore be positive polarity and be under the situation of negative polarity at grayscale voltage, all adopted grayscale voltage with identical voltage.But, in some cases, concerning the same voltage that is added to liquid crystal cells, institute's making alive is that positive polarity and institute's making alive are when being negative polarity, actual light transmission features is different, this is that variation by the voltage that is added to pixel electrode causes, and this variation is because TFT causes as the switch noise of on-off element or the stray capacitance of TFT.Therefore, if adopted the grayscale voltage V that has only a kind of polarity to be inverted and have identical voltage
1-V
8, then colour correction will become very difficult, consequently, can not obtain high-quality image.In order to address the above problem, the gray scale of present embodiment produces circuit 21 and design like this, the characteristic of the voltage by considering to be added to liquid crystal cells, when institute's making alive polarity for being when bearing just with institute making alive polarity, the transmissison characteristic difference, so it can produce the grayscale voltage V with positive polarity
P1-V
P8With grayscale voltage V with negative polarity
N1-V
N8This has realized the demonstration of high quality graphic.
Grayscale voltage setting data DG is made up of the start bit of the starting position of 1 bit representation valid data, the address bit of 4 bit representation address informations and the data bit of 8 bit representation differential voltage Value Datas.Address information is used to select to form 16 DAC32 that following grayscale voltage produces circuit 21
1-32
8And DAC33
1-33
8In any.The differential voltage Value Data is used for changing from each DAC32
1-32
8And DAC33
1-33
8The differential voltage level of middle output, this differential voltage level is corresponding to the voltage difference between adjacent two grayscale voltages.
Data bit is that data bit is that the reason of voltage value data is as follows in differential voltage data rather than the traditional scheme.That is, if as in the conventional situation, data bit is a voltage value data, and each DAC12
1-12
8Voltage data is converted into aanalogvoltage, and it is above-mentioned multiple unfavorable then will inevitably to take place, as each DAC12
1-12
8With each buffer amplifier 13
1-13
8To have very wide dynamic range, the LCD power consumption becomes big, and LCD is used inconvenient, and has a large amount of dislocations.In order to address these problems, in first embodiment, data bit has adopted the differential voltage Value Data.The actual effect that adopts the differential voltage data to produce as data bit will describe in detail below.
By the grayscale voltage V of the positive polarity that provides by grayscale voltage generation circuit 21 is provided
P1-V
P8Grayscale voltage V with negative polarity
N1-V
N8, data driver 22 produces the grayscale voltage of a series of positive polarity grayscale voltages that apply and a series of negative polarity that apply.Then, the video data D of delegation of data driver 22 utilizations and data clock DCK synchronization gain
00-D
07, D
10-D
17, D
20-D
27From a plurality of positive polarity grayscale voltages that apply or a plurality of negative polarity grayscale voltage that applies, select a grayscale voltage that applies, and it is input to respective data lines in the LCD 1 as data danger signal, data green or data blue signal.
Below, 1 explanation grayscale voltage produces the structure of circuit 21 with reference to the accompanying drawings.
As shown in Figure 1, grayscale voltage generation circuit 21 comprises an interface circuit 31, DAC32
1-32
8And DAC33
1-33
8, totalizer 34
1-34
8With subtracter 35
1-35
8, interface circuit 31 has each DAC32
1-32
8And DAC33
1-33
8, select by the address information imported the differential voltage Value Data, form grayscale voltage setting data DG by latching from the outside of forming grayscale voltage setting data DG for each DAC.Each DAC32
1-32
8And DAC33
1-33
8The differential voltage Value Data that latchs is converted to aanalogvoltage, and the voltage of output conversion.
In other words, in the present embodiment, with each DAC32
1-32
8And DAC33
1-33
8All have the aanalogvoltage difference of the grayscale voltage of 256 gray levels, each DAC32 the output correspondence
1-32
8And DAC33
1-33
8Only export a corresponding DAC32
1-32
8And DAC33
1-33
8In the aanalogvoltage of voltage difference between adjacent two grayscale voltages.For example, DAC32
1, the voltage transitions that will be used for voltage value data with DAC is self grayscale voltage V
P1Difference, the voltage transitions that it will be used for voltage value data is a corresponding reference voltage V
REFWith grayscale voltage V
P1Between the aanalogvoltage of difference.Then, each DAC32
2-32
8The voltage transitions of the differential voltage Value Data that correspondence will be imported is the grayscale voltage V of a corresponding positive polarity
P1-V
P8In the aanalogvoltage of difference between adjacent two grayscale voltages.On the other hand, DAC33
1The voltage transitions that will be used for the differential voltage Value Data is corresponding reference voltage V
REFWith grayscale voltage V
N1Between the aanalogvoltage of difference.Therefore, each DAC33
2-33
8The voltage transitions of the differential voltage Value Data that correspondence will be imported is the grayscale voltage V of a corresponding negative polarity
N1-V
N8In the aanalogvoltage of difference between adjacent two grayscale voltages.From each DAC32
1-32
8And DAC33
1-33
8In the aanalogvoltage of output be retained as same voltage level, latch by interface circuit 31 up to the voltage of the new differential voltage Value Data of correspondence.In the present embodiment, distribute to the differential voltage Value Data for 8, each DAC32
1-32
8And DAC33
1-33
8Exportable one adds up to the aanalogvoltage of 256 gray levels.
Each totalizer 34
1-34
8By with reference voltage V
REFOr totalizer 34
1-34
7In the addition results DAC32 corresponding that obtain in adjacent one with each
1-32
8The input the aanalogvoltage addition, obtain a result, and with this as a result voltage as the grayscale voltage V of positive polarity
P1-V
P8Output.Each subtracter 35
1-35
8From reference voltage V
REFOr subtracter 35
1-35
7In adjacent subtracter in the subtraction result that obtains, deduct each corresponding DAC33
1-33
8The input aanalogvoltage, and with this as a result voltage as the grayscale voltage V of negative polarity
N1-V
N8Output.
Below, explanation is had the operation that the grayscale voltage of said structure produces circuit 21.At first, when outside input gray level voltage setting data, interface circuit 31 according to the address information of forming grayscale voltage setting data DG, is selected DAC32
1-32
8And DAC33
1-33
8In any, and make DAC32
1-32
8And DAC33
1-33
8In any latch the differential voltage Value Data of forming grayscale voltage setting data DG.Here, address information and each DAC32 have been shown among Fig. 3
1-32
8And DAC33
1-33
8Between the example of relation.For example, if address information is " 0000 ", then interface circuit 31 is selected DAC32
1And make DAC32
1Differential voltage Value Data after the latch address information, for example " 00000010 ".Similarly, interface circuit 31, the address information according to forming the grayscale voltage setting data DG that is imported in proper order by the outside makes each DAC32
1-32
8And DAC33
1-33
8Latch the differential voltage Value Data of forming grayscale voltage setting data DG.
Each DAC32
1-32
8And DAC33
1-33
8The voltage transitions of the differential voltage Value Data that correspondence is latched is an aanalogvoltage, and exports this voltage.Each DAC32
1-32
8And DAC33
1-33
8The aanalogvoltage of output is retained as same voltage level, has latched up to interface circuit 31 till the voltage of corresponding new voltage value data.Then, totalizer 34
1With DAC32
1The aanalogvoltage and the reference voltage V of output
REFAddition, and with the voltage of addition gained as positive polarity grayscale voltage V
P1Output.In addition, totalizer 34
2Will be from totalizer 34
1The addition results of gained and DAC32
2The aanalogvoltage addition of output, and with the voltage of addition gained as positive polarity grayscale voltage V
P2Output.Similarly, each totalizer 34
3-34
8With totalizer 34
2-34
7In the corresponding DAC32 of addition results of an adjacent gained with each
3-32
8The aanalogvoltage addition of output, and with the voltage of addition gained as positive polarity grayscale voltage V
P3-V
P8Output.On the other hand, subtracter 35
1From reference voltage V
REFIn deduct DAC33
1The aanalogvoltage of output, and the voltage that subtraction is obtained is as the grayscale voltage V of negative polarity
N1Output.Similarly, subtracter 35
2From subtracter 35
1Deduct DAC33 in the subtraction result that obtains
2The aanalogvoltage of output, and the voltage that subtraction is obtained is as the grayscale voltage V of negative polarity
N2Output.Similarly, each subtracter 35
3-35
8From subtracter 35
2-35
7In deduct each corresponding DAC33 in the subtraction result of an adjacent acquisition
3-33
8The aanalogvoltage of output, and the voltage that subtraction is obtained is as the grayscale voltage V of negative polarity
N3-V
N8Output.
Positive polarity grayscale voltage V
P1-V
P8With negative polarity grayscale voltage V
N1-V
N8Be imported in the data driver 22.Data driver 22 is with positive polarity grayscale voltage V
P1-V
P8With negative polarity grayscale voltage V
N1-V
N8Cut apart the negative polarity grayscale voltage that produces a plurality of positive polarity grayscale voltages that apply and apply.Then, data driver 22 is by utilizing the video data D of delegation that obtains synchronously with data clock DCK
00-D
07, D
10-D
17And D
20-D
27From a plurality of positive polarity grayscale voltages that apply and a plurality of negative polarity grayscale voltage that applies, select a grayscale voltage that applies, and it is outputed to respective data lines in the LCD 1 as data danger signal, data green or data blue signal.
Therefore, according to first embodiment, in each totalizer 34
1-34
8In, reference voltage V
REFOr totalizer 34
1-34
7In the addition results that obtains in adjacent one with by each corresponding DAC32
1-32
8The aanalogvoltage addition that obtains from the voltage transitions of corresponding differential voltage Value Data, and with magnitude of voltage as a result as the grayscale voltage V of each positive polarity
P1-V
P8Output.In addition, at subtracter 35
1-35
8In, from reference voltage V
REFOr from subtracter 35
1-35
7In deduct by each corresponding DAC33 in the adjacent subtraction result that obtains
1-33
8The aanalogvoltage that obtains from the voltage transitions of corresponding differential voltage Value Data, and with voltage as a result as the grayscale voltage V of each negative polarity
N1-V
N8Output.
Therefore, as conventional art, may be to because γ be carried out in the distortion of the gray level image display characteristic that causes of LCD 1 specific characteristic proofreaies and correct, and/or realize obtaining to be fit to consumer taste or meet will the objects displayed image the gray scale display characteristic.In addition, by with reference voltage V
REFBe set at a desired value, can produce grayscale voltage V at an easy rate with voltage available level
P1-V
P8And V
N1-V
N8Consequently, each DAC32
1-32
8And DAC33
1-33
8Dynamic range compare with conventional situation and narrow down.This makes grayscale voltage generation circuit 21 to be made of the low cost LSI of the DAC with narrow dynamic range.In addition, because each DAC32
1-32
8And DAC33
1-33
8Dynamic range narrow down, energy loss is compared also with conventional situation and can be reduced greatly.Consequently, the LCD 1 of first embodiment can be used as the display device use by battery-driven portable electron device.
And, according to first embodiment, move or voltage amplification owing to no longer need to carry out the level that the grayscale voltage that makes grayscale voltage or apply is in the voltage available level, therefore, can produce high-precision grayscale voltage, and realize that high-quality image shows.
And, according to first embodiment, output gray level voltage setting data D
GDevice, for example a signal conditioning package as PC etc., can be exported the differential voltage Value Data as data bit.Consequently, signal conditioning package no longer needs the grayscale voltage setting data D that checks that composition is transfused in proper order
GThe differential voltage Value Data whether meet the initial conditions of above-mentioned data driver, need not check whether voltage is the voltage available level yet, therefore can provide easy-to-use.In addition, because DAC32
1-32
8And DAC33
1-33
8With the voltage transitions of corresponding differential voltage Value Data is aanalogvoltage, therefore, and DAC32
1-32
8And DAC33
1-33
8The upper and lower bound of each output voltage between potential difference (PD) can be set as very little.This makes DAC32
1-32
8And DAC33
1-33
8In mistake be reduced.For example, when the figure place of the digital of digital video data of outside input is 8, DAC32
1-32
8And DAC33
1-33
8The upper and lower bound of each output voltage between electric potential difference be 2.0[V], and the dislocation of DAC be approximately ± during 1 scale-of-two LSB position, shown in expression formula (6), output error ER is less than 20[mV], and the scrambling of gray scale becomes and does not observe.For example, even when gray level image shows, vertical bar is also invisible.This can realize the demonstration of high quality graphic.
ER=2.0[V]/256 * 2=15.6[mV] ... expression formula (6) second embodiment
Fig. 4 is a schematic block diagrams, shows the structure that the second embodiment of the invention grayscale voltage produces circuit 41.In Fig. 4, identical Reference numeral represent with first embodiment shown in Figure 1 in have the identical corresponding component of identical function, their associated description will be omitted.Produce in the circuit 41 at the grayscale voltage shown in Fig. 4, subtracter 42 newly is provided
1-42
8With totalizer 43
1-43
8Replace totalizer 34
1-34
8With subtracter 35
1-35
8
DAC32
8Is corresponding grey scale voltage V with correspondence with the voltage transitions of the differential voltage Value Data that is provided
P8With the first reference voltage V
REF1Between the aanalogvoltage of difference.Subsequently, each DAC32
7-32
1Is corresponding positive polarity grayscale voltage V with correspondence with the voltage transitions of the differential voltage Value Data that is provided
P8-V
P2In two grayscale voltages adjacent one another are between the aanalogvoltage of difference.On the other hand, DAC33
8Is corresponding grey scale voltage V with correspondence with the voltage transitions of the differential voltage Value Data that is provided
N1With the second reference voltage V
REF2Between the aanalogvoltage of difference.Subsequently, each DAC33
7-33
1Is corresponding negative polarity grayscale voltage V with correspondence with the voltage transitions of the differential voltage Value Data that is provided
N8-V
N2In two grayscale voltages adjacent one another are between the aanalogvoltage of difference.Each DAC32
1-32
8And DAC33
1-33
8The aanalogvoltage of middle output is retained as same voltage level, till the voltage of the new differential voltage Value Data of correspondence is latched by interface circuit 31.
Each subtracter 42
8-42
1From the first reference voltage V
REF1Or from subtracter 42
8-42
2In in the subtraction value that obtains in adjacent one, deduct from each corresponding DAC32
8-32
1In the aanalogvoltage of input, and with magnitude of voltage as a result as each positive polarity grayscale voltage V
P8-V
P1Output.Each totalizer 43
8-43
1With the second reference voltage V
REF2Or from totalizer 43
8-43
2In the addition results that obtains in adjacent one with from each corresponding DAC33
8-33
1The aanalogvoltage addition of input, and with magnitude of voltage as a result as the grayscale voltage V of negative polarity
N8-V
N1Output.
In addition, have the operation of the grayscale voltage generation circuit 41 of said structure, identical except 3 points described below with first embodiment, omit these explanations here accordingly.That is, the operation of grayscale voltage generation circuit 41 and the difference among first embodiment are: at each DAC32
1-32
8And DAC33
1-33
8In, the voltage of corresponding differential voltage Value Data differs from one another, the grayscale voltage V of positive polarity
P1-V
P8Obtain the grayscale voltage V of negative polarity by subtraction
N1-V
N8Obtain by addition.
Like this, according to second embodiment, can realize the effect identical with first embodiment.The 3rd embodiment
Fig. 5 is a schematic block diagrams, shows the structure of grayscale voltage generation circuit 51 in the third embodiment of the invention.Among Fig. 5, identical Reference numeral represent with first embodiment shown in Figure 1 in have the identical corresponding component of identical function, their associated description will be omitted.Grayscale voltage among Fig. 5 produces in the circuit 51, the DAC33 shown in Fig. 1
1-33
8Deleted, each DAC32
1-32
8Outlet terminal and each subtracter 35
1-35
8Entry terminal connect.
Each DAC32
1-32
8The voltage of the differential voltage Value Data that conversion corresponding interface circuit 31 latchs, and with its output.Each totalizer 34
1-34
8With reference voltage V
REFOr totalizer 34
1-34
7In adjacent one in the corresponding DAC32 of addition results that obtains with each
1-32
8The aanalogvoltage addition of output, and with voltage as a result as positive polarity grayscale voltage V
P1-V
P8Output.Each DAC32
1-32
8The output aanalogvoltage is retained as same voltage level, latchs the voltage of a new differential voltage Value Data of correspondence up to interface circuit 31.Each subtracter 35
1-35
8From reference voltage V
REFOr from subtracter 35
1-35
7In in the subtraction result that obtains in adjacent one, deduct from each corresponding DAC32
1-32
8In the aanalogvoltage of output, and with magnitude of voltage as a result as each negative polarity grayscale voltage V
N1-V
N8Output.At this moment, address information has only 3 compositions, that is, and and between address information shown in Figure 3 and the DAC in the relation table high-order 8.
In addition, it is identical in following 2 and first embodiment to have a operation that the grayscale voltage of said structure produces circuit 51, therefore omits corresponding description.That is different being among the gray scale operation that produces circuit 51 and first embodiment: correspondingly will be imported into each DAC32
1-32
8In the voltage difference of differential voltage Value Data, by each DAC32
1-32
8The aanalogvoltage of middle output can obtain the grayscale voltage V of negative polarity
N1-V
N8
Like this, according to the 3rd embodiment, can realize effect identical among first embodiment.In addition, the scale of circuit is compared also with first and second embodiment and is diminished.
In addition, in above-mentioned first and second embodiment, because when providing voltage to be positive polarity and negative polarity to liquid crystal cells, therefore the transmissison characteristic difference of liquid crystal cells, produces the grayscale voltage V of positive polarity
P1-V
P8Grayscale voltage V with negative polarity
N1-V
N8This has realized the high-quality display of image.But, when LCD do not need to be used to the situation of high quality graphic or when providing voltage to be positive polarity and negative polarity to liquid crystal cells, when the different negligible LCD of its transmissison characteristic is driven, though according to corresponding to the 3rd embodiment in the magnitude of voltage of identical differential voltage Value Data produced positive polarity grayscale voltage V
P1-V
P8With negative polarity grayscale voltage V
N1-V
N8, problem can not take place.In addition, when having adopted some inversion driving method, line inversion driving method or frame inversion driving method, owing to the polarity that produces grayscale voltage in circuit 3 or the data driver 4 at grayscale voltage all needs oppositely, therefore need switch, in the ordinary course of things so that grayscale voltage V
1With grayscale voltage V
8In one be used as maximum grayscale voltage, another is used as minimum luminance voltage.In the 3rd embodiment, the grayscale voltage V of positive polarity
P1-V
P8Grayscale voltage V with negative polarity
N1-V
N8Produced separately respectively, therefore this switching no longer needs.
Clearly the present invention is not limited to the foregoing description, but can change under the situation that does not break away from the scope of the invention and spirit and revise.For example, be that the dynamic range of each DAC of hypothesis equates in the various embodiments described above, still, the dynamic range of each DAC can be different.The dynamic range of each DAC can different reasons be that the relation between the grayscale voltage and brightness is non-linear in the LCD as shown in Figure 6, and the value of grayscale voltage is not to be set at equal intervals.Particularly, be used for and will and approach maximum or the voltage transitions of the differential voltage Value Data of the grayscale voltage of minimum luminance voltage is that the dynamic range of the DAC of aanalogvoltage can be set as broad corresponding to maximum grayscale voltage, minimum luminance voltage, the dynamic range that is used to change corresponding to the DAC of the voltage of the differential voltage Value Data of the grayscale voltage of the voltage level that mediates can be set as very narrow.
In addition, in the various embodiments described above, showing an example, is one to one between the number of the number of the grayscale voltage that will be produced and differential voltage Value Data wherein, and still, the present invention is not limited thereto.For example, the number of differential voltage Value Data can be set as the number less than the grayscale voltage that will be produced, and the required number of grayscale voltage can produce by utilizing totalizer or subtracter to calculate the differential voltage Value Data.In addition, the differential voltage Value Data is not limited to grayscale voltage adjacent one another are.
And, in the various embodiments described above, an example is shown, a grayscale voltage setting data wherein is provided from the outside, still, the present invention is not limited thereto.Promptly, for example, it can be such structure that grayscale voltage produces circuit, be that the grayscale voltage setting data is stored in the memory storage in advance, as be installed on the inside or the outside register of interface circuit, latch, storer etc., and after providing power supply to LCD, the grayscale voltage setting data is read out from above-mentioned memory storage, and is latched by each DAC.
And, in the above-mentioned first and the 3rd embodiment, utilize same reference voltage V
REFProduce the grayscale voltage V of positive polarity
P1-V
P8Grayscale voltage V with negative polarity
N1-V
N8, still, they also can utilize different voltages and produce.
And, in the various embodiments described above, an example is shown, wherein the number of the grayscale voltage of identical polar is eight, still, it also can be greater than or less than 8.
And, in the above-described embodiments, utilize the grayscale voltage of the arithmetic operation unit generation identical polar of same type, still, also can utilize different arithmetic operation units, i.e. totalizer or subtracter.
And in the various embodiments described above, reference voltage is set as and is similar to minimum luminance voltage or maximum grayscale voltage, and still, it also can be set as the grayscale voltage with intermediate voltage level, for example, is similar to grayscale voltage V
P3, V
P4, V
N3And V
N4Voltage.
In addition, in the various embodiments described above, each grayscale voltage produces circuit and data driver provides separately respectively, and still, grayscale voltage produces circuit and can be installed in the data driver.
In addition, the present invention not only can be used for colour liquid crystal display device and also can be used for monochromatic liquid crystal display.
Claims (17)
1. thereby one kind by providing the brightness level, producing the grayscale voltage production method of a plurality of grayscale voltage display images to liquid crystal display device, and this method comprises:
After a plurality of digital data conversion of the voltage difference in a plurality of grayscale voltages with correspondence between any two grayscale voltages are aanalogvoltage, but, thereby produce a plurality of grayscale voltages to an aanalogvoltage and reference voltage or any at least two aanalogvoltages execution operational computations.
2. grayscale voltage production method as claimed in claim 1 is characterized in that described reference voltage is the voltage corresponding to the maximal value or the minimum value of each grayscale voltage.
3. grayscale voltage production method as claimed in claim 1, but it is characterized in that operational computations is addition or subtraction.
4. grayscale voltage production method as claimed in claim 1 is characterized in that a plurality of grayscale voltages are made up of the grayscale voltage of a plurality of positive polaritys and the grayscale voltage of a plurality of negative polarity.
5. grayscale voltage production method as claimed in claim 4, but it is characterized in that having the operational computations that the reference voltage of identical value carries out by utilization, produce the grayscale voltage of a plurality of positive polaritys and the grayscale voltage of a plurality of negative polarity.
6. thereby one kind produces circuit by the grayscale voltage that the brightness level is provided to liquid crystal display device, produces a plurality of grayscale voltage display images, comprising:
A plurality of D-A converters, a plurality of digital data conversion that are used for the voltage difference between two grayscale voltages of each corresponding a plurality of grayscale voltage are aanalogvoltage; With
But a plurality of operational computations unit, but be used for carrying out operational computations to an aanalogvoltage and reference voltage or to any at least two aanalogvoltages.
7. grayscale voltage as claimed in claim 6 produces circuit, it is characterized in that reference voltage is the voltage corresponding to the maximal value or the minimum value of each grayscale voltage.
8. grayscale voltage as claimed in claim 6 produces circuit, but it is characterized in that the operational computations unit is totalizer or subtracter.
9. grayscale voltage as claimed in claim 6 produces circuit, it is characterized in that a plurality of grayscale voltages are made up of the grayscale voltage of a plurality of positive polaritys and the grayscale voltage of a plurality of negative polarity.
10. grayscale voltage as claimed in claim 9 produces circuit, but it is characterized in that having by utilization the operational computations of the reference voltage execution of identical value, produces a plurality of positive polarity grayscale voltages and a plurality of negative polarity grayscale voltage.
11. grayscale voltage as claimed in claim 6 produces circuit, it is characterized in that also comprising memory storage, in this memory storage, store a plurality of numerical datas in advance, provide circuit with data, be used for when adding power supply, from memory storage, read a plurality of numerical datas, and the numerical data of reading is input in each D-A converter.
12. a liquid crystal display device, thus the grayscale voltage that this device has by provide brightness to produce a plurality of grayscale voltage display images to liquid crystal display device produces circuit, and this grayscale voltage produces circuit and comprises:
A plurality of D-A converters, each digital data conversion that is used for the voltage difference between two grayscale voltages of each corresponding a plurality of grayscale voltage is an aanalogvoltage; With
But a plurality of operational computations unit, but be used for carrying out operational computations to an aanalogvoltage and reference voltage or to any at least two aanalogvoltages.
13. liquid crystal display device as claimed in claim 12 is characterized in that reference voltage is the voltage corresponding to the maximal value or the minimum value of each a plurality of grayscale voltage.
14. liquid crystal display device as claimed in claim 12, but it is characterized in that the operational computations unit is totalizer or subtracter.
15. liquid crystal display device as claimed in claim 12 is characterized in that a plurality of grayscale voltages are made up of a plurality of positive polarity grayscale voltages and a plurality of negative polarity grayscale voltage.
16. liquid crystal display device as claimed in claim 15, but it is characterized in that having the operational computations that the reference voltage of identical value is carried out by utilization, produce a plurality of positive polarity grayscale voltages and a plurality of negative polarity grayscale voltage.
17. liquid crystal display device as claimed in claim 12, it is characterized in that also comprising memory storage, in this memory storage, store a plurality of numerical datas in advance, provide circuit with data, be used for when adding power supply, from memory storage, read a plurality of numerical datas, and the numerical data of reading is input in each D-A converter.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNA021305722A CN1475984A (en) | 2002-08-16 | 2002-08-16 | Grey voltage generating method and circuit, and liquid crystal display device |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNA021305722A CN1475984A (en) | 2002-08-16 | 2002-08-16 | Grey voltage generating method and circuit, and liquid crystal display device |
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| Publication Number | Publication Date |
|---|---|
| CN1475984A true CN1475984A (en) | 2004-02-18 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CNA021305722A Pending CN1475984A (en) | 2002-08-16 | 2002-08-16 | Grey voltage generating method and circuit, and liquid crystal display device |
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| CN (1) | CN1475984A (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN100392720C (en) * | 2004-07-02 | 2008-06-04 | 恩益禧电子股份有限公司 | Gradation voltage selecting circuit, driver circuit, liquid crystal drive circuit, and liquid crystal display device |
| CN101390151B (en) * | 2006-02-28 | 2011-07-06 | 夏普株式会社 | Display device and its drive method |
| CN101625825B (en) * | 2008-07-08 | 2012-06-13 | 乐金显示有限公司 | Gamma reference voltage generation circuit and flat panel display using it |
| CN1825174B (en) * | 2005-02-25 | 2012-07-25 | 瑞萨电子株式会社 | Gray scale voltage generating circuit |
-
2002
- 2002-08-16 CN CNA021305722A patent/CN1475984A/en active Pending
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN100392720C (en) * | 2004-07-02 | 2008-06-04 | 恩益禧电子股份有限公司 | Gradation voltage selecting circuit, driver circuit, liquid crystal drive circuit, and liquid crystal display device |
| CN1825174B (en) * | 2005-02-25 | 2012-07-25 | 瑞萨电子株式会社 | Gray scale voltage generating circuit |
| CN101390151B (en) * | 2006-02-28 | 2011-07-06 | 夏普株式会社 | Display device and its drive method |
| CN101625825B (en) * | 2008-07-08 | 2012-06-13 | 乐金显示有限公司 | Gamma reference voltage generation circuit and flat panel display using it |
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