Background technology
(Liquid Crystal Display LCD) is widely used LCD recently, and (Cathode Ray Tube CRT) becomes one of the main flow of display of future generation to replace cathode-ray tube display.Along with the improvement of semiconductor technology, large-sized LCD is born successively, but derives another technical bottleneck also, and that is exactly along with the size of display panel is bigger, and then the problem of film flicker also heals and becomes serious.
The structural area of pixel cell is divided into two kinds in the conventional display panels, and one is the structural representation of the pixel cell 100 that Fig. 1 illustrated, and second it be the structural representation of the pixel cell 200 that Fig. 2 illustrated.Merging is with reference to Fig. 1 and Fig. 2, and pixel cell 100 and 200 all comprises thin film transistor (TFT) 101, liquid crystal capacitance C separately
LC, memory capacitance C
S, and stray capacitance C
GdAnd maximum difference be in, pixel cell 100 is memory capacitance C
S(pixel cell 200 then is memory capacitance C for common voltage, the Vcom) design on (CS on common) at common voltage
SAt sweep trace G
M-1On design (Cs on gate).
No matter adopt above-mentioned any pixel cell, the signal SG that is exported when gate drivers (gate driver does not illustrate) is by high level V
HPromptly reduce to low level V
L, and when causing thin film transistor (TFT) 101 to be closed, because of stray capacitance C
GdThe coupling effect that is caused (coupling effect) will cause the drain terminal voltage V of thin film transistor (TFT) 101
DA voltage difference delta V descends
FT, as shown in Equation (1):
(1)
Δ V wherein
GP=V
H-V
L, and the voltage difference delta V of this change
FTBe referred to as feed-trough voltage (feed-through voltage).Can learn by formula (1), because the feed-trough voltage Δ V of conventional display panels interior pixel unit
FTValue is not quite similar, and therefore will cause the flicker noise (flicker noise) of display panel, and then increase the weight of the film flicker that LCD presents.
In order to alleviate the film flicker that above-mentioned feedthrough effect is derived, existing also corresponding development goes out the correlation technique of solution, and it comprises:
1. according to feed-trough voltage Δ V
FTValue is provided by the common voltage that provides to display panel.
2. use the Driving technique of the signal on 3 rank or 4 rank.
Fig. 3 illustrates the analog waveform figure into above-mentioned correlation technique 1.It is applicable to the above-mentioned pixel cell that discloses 100, please merge with reference to Fig. 1 and Fig. 3.When signal SG is high level V
HThe time, thin film transistor (TFT) 101 conductings.At this moment, the source voltage V that is transmitted by data line SL
STo be stored in liquid crystal capacitance C
LCOn, cause drain terminal voltage V
DLevel change to source voltage V
SLevel.Yet, when signal SG by high level V
HPromptly reduce to low level V
LThe time, drain terminal voltage V
DThe level feed-trough voltage Δ V that will descend
FTValue.In order to eliminate feed-trough voltage Δ V
FTThe film flicker that is caused, correlation technique 1 is adjusted to best common voltage V ' com with the common voltage Vcom of display panel.
Yet correlation technique 1 must be carried out complicated manual measurement earlier, so that the best common voltage V ' com that provides to display panel to be provided when adjusting common voltage Vcom.In addition, the characteristic of each sheet display panel is not quite similar, so the above-mentioned best common voltage V ' com that determines might not meet each sheet display panel fully.
Fig. 4 illustrates the analog waveform figure into above-mentioned correlation technique 2.It is applicable to the above-mentioned pixel cell that discloses 200, please merge with reference to Fig. 2 and Fig. 4.As drain terminal voltage V
DThe level feed-trough voltage Δ V that descends
FTDuring value, correlation technique 2 is by signal SG
M-1With SG
mThe bucking voltage V that between low period, is provided
P, cause drain terminal voltage V
DThe level step charge to source voltage V
SLevel.
Yet, the bucking voltage V that correlation technique 2 is provided
PThough, can calculate generation according to theoretical formula.But on practical application face, signal SG is produced by the gate drivers in the LCD (gate driver).Therefore, improving bucking voltage V
PAccuracy the time, must exchange for by the design complexities that improves gate drivers.Thus, correlation technique 2 has increased the design complexities of gate drivers also, and then has caused LCD to spend more layout area and power consumption when eliminating the film flicker that LCD presented.
Summary of the invention
The purpose of this invention is to provide a kind of display panel, it utilizes switch unit to control the time point that the pixel column unit receives the common voltage of display panel.By this, with prior art in comparison, display panel of the present invention need just can not reach the influence of elimination feedthrough effect to display panel by increasing the circuit complexity of gate drivers yet under the situation that does not change common voltage for panel of display.
Another object of the present invention just provides a kind of LCD, spirit according to the invention described above display panel, can be used in the LCD of the present invention, not only can reach by this outside the advantage of display panel of the invention described above, and more can reduce the flicker noise of display panel, promote the picture quality that LCD was presented to reach.
For reaching above-mentioned or other purposes, the present invention proposes a kind of display panel, and it is applicable to LCD.This display panel comprises a plurality of pixel columns unit and a plurality of switch unit.Wherein each pixel column unit strings is connected between an one scan line and the level switch line, and first end of each switch unit is in order to receive the common voltage of display panel, and second end of each switch unit then is electrically connected to the level switch line.By this, each switch unit is its first end of conducting and second end before the high transition of its pairing signal, receives common voltage from display panel to cause its pairing pixel column unit.In addition, each switch unit disconnected its first end and second end before the low transition of its pairing signal, switch to floating to cause its pairing pixel column unit.
In an embodiment of the present invention, above-mentioned each pixel column unit comprises N pixel cell, and N pixel cell is corresponding one to one with N bar data line, and N is the integer greater than 0.Wherein each pixel cell comprises first switch and memory circuit.First switch is in order to determine whether its corresponding data lines electrically connects with memory circuit.Memory circuit is then in order to determine the demonstration GTG of display panel.
It should be noted that above-mentioned memory circuit comprises a liquid crystal capacitance at least, and first switch is a thin film transistor (TFT).In addition, above-mentioned data line is electrically connected at the source electrode driver of LCD.
In an embodiment of the present invention, above-mentioned each switch unit comprises a switch at least.And the gate drivers of LCD produces above-mentioned those signals and a plurality of level switching signal, and each switch unit is according to its pairing level switching signal, and determines the conducting state of its first end and second end.
From another viewpoint, the invention provides a kind of LCD, comprise display panel, a plurality of switch unit and driver element.Wherein display panel comprises a plurality of pixel columns unit at least, each pixel column unit strings is connected between an one scan line and the level switch line, and first end of each switch unit is in order to receive the common voltage of display panel, and second end of each switch unit is electrically connected at the level switch line.By this, each switch unit is its first end of conducting and second end before the high transition of its pairing signal, receives common voltage from display panel to cause its pairing pixel column unit.In addition, each switch unit disconnected its first end and second end before the low transition of its pairing signal, so that its pairing pixel column unit switches to floating.Driver element is then in order to drive display panel.
In an embodiment of the present invention, above-mentioned driver element comprises gate drivers and source electrode driver.Wherein gate drivers is in order to produce above-mentioned those signals, and source electrode driver then drives the required source voltage in pixel column unit in order to produce.
LCD provided by the present invention and display panel thereof are controlled the time point that the pixel column unit receives the common voltage of display panel by switch unit.By this, the present invention has not only reduced the flicker noise of display panel, has also promoted the picture quality that LCD presented.
For above-mentioned and other purposes, feature and advantage of the present invention can be become apparent, preferred embodiment cited below particularly, and conjunction with figs. is described in detail below.
Embodiment
Major technique of the present invention is characterized as the pixel column unit under the conducting state that cooperates the switch unit two ends, optionally receives the common voltage from display panel, eliminates the flicker noise that the feedthrough effect is caused by this.Below will enumerate explanation display panel of the present invention and LCD, but it is not in order to limit the present invention, to have the knack of this skill person and can modify slightly following embodiment according to spirit of the present invention, precisely because still belong to the present invention's scope.
Fig. 5 illustrates the structural representation into the display panel of foundation one embodiment of the invention.For convenience of description, Fig. 5 more shows source electrode driver 502 and gate drivers 503.With reference to Fig. 5, display panel 501 comprises a plurality of pixel columns unit and a plurality of switch unit.For clear each member of expression, Fig. 5 shows pixel column unit 510 and 520 and switch unit 530 and 540 at this.Wherein pixel column unit 510 is serially connected in sweep trace GL
1With level switch line CL
1Between.Pixel column unit 520 is serially connected in sweep trace GL
2With level switch line CL
2Between.First end of switch unit 530 is in order to receive the common voltage Vcom of display panel 501, and second end of switch unit 530 then is electrically connected to level switch line CL
1In addition, first end of switch unit 540 is in order to receive the common voltage Vcom of display panel 501, and second end of switch unit 540 then is electrically connected to level switch line CL
2
Illustrate further, above-mentioned pixel column unit 510 comprises N pixel cell PI
1~PI
NN pixel cell PI wherein
1~PI
NWith N bar data line SL
1~SL
NCorresponding one to one, N is the integer greater than 0.In addition, each pixel cell PI
1~PI
NComprise a switch, a memory circuit and a stray capacitance.It should be noted that each pixel cell PI
1~PI
NSwitch comprise a thin film transistor (TFT), and above-mentioned memory circuit comprises a liquid crystal capacitance at least.
For instance, pixel cell PI
1Comprise switch SW
51, memory circuit (liquid crystal capacitance C
51) and stray capacitance C
Gd1Switch SW wherein
51First end be electrically connected at corresponding data lines SL
1, switch SW
51Control end be electrically connected at sweep trace GL
1Memory circuit (liquid crystal capacitance C
51) be serially connected in switch SW
51Second end and level switch line CL
1Between.Stray capacitance C
Gd1Be electrically connected to sweep trace GL
1With switch SW
51Second end.
Similarly, pixel cell PI
2Comprise switch SW
52, memory circuit (liquid crystal capacitance C
52) and stray capacitance C
Gd2Switch SW wherein
52First end be electrically connected at corresponding data lines SL
2, switch SW
52Control end be electrically connected at sweep trace GL
1Memory circuit (liquid crystal capacitance C
52) be serially connected in switch SW
52Second end and level switch line CL
1Between.Stray capacitance C
Gd2Be electrically connected to sweep trace GL
1With switch SW
52Second end.Pixel cell PI by that analogy
3~PI
NDetailed architecture, do not repeat them here.
On the other hand, the detailed architecture of above-mentioned pixel column unit 520 is similar to pixel column unit 510.Pixel column unit 520 comprises N pixel cell PII
1~PII
NN pixel cell PII wherein
1~PII
NAlso with N bar data line SL
1~SL
NCorresponding one to one.In addition, each pixel cell PII
1~PII
NComprise a switch, a memory circuit and a stray capacitance.Similarly, each pixel cell PII
1~PII
NSwitch comprise a thin film transistor (TFT), and above-mentioned memory circuit comprises a liquid crystal capacitance at least.
For instance, pixel cell PII
1Comprise switch SW
53, memory circuit (liquid crystal capacitance C
53) and stray capacitance C
Gd3Switch SW wherein
53First end be electrically connected at corresponding data lines SL
1, switch SW
53Control end be electrically connected at sweep trace GL
2Memory circuit (liquid crystal capacitance C
53) be serially connected in switch SW
53Second end and level switch line CL
2Between.Stray capacitance C
Gd3Be electrically connected to sweep trace GL
2With switch SW
53Second end.
Similarly, pixel cell PII
2Comprise switch SW
54, memory circuit (liquid crystal capacitance C
54) and stray capacitance C
Gd4Switch SW wherein
54First end be electrically connected at corresponding data lines SL
2, switch SW
54Control end be electrically connected at sweep trace GL
2Memory circuit (liquid crystal capacitance C
54) be serially connected in switch SW
54Second end and level switch line CL
2Between.Stray capacitance C
Gd4Be electrically connected to sweep trace GL
2With switch SW
54Second end.Pixel cell PII by that analogy
3~PII
NDetailed architecture, do not repeat them here.
Enter again before the mutual operation mechanism of pixel column unit 510~520 and switch unit 530~540, must understand that earlier display panel 501 is applicable to a LCD (not showing at this), and source electrode driver 502 is exactly the member that LCD contains with gate drivers 503.Wherein source electrode driver 502 is electrically connected to data line SL
1~SL
N, gate drivers 503 is electrically connected to sweep trace GL
1With GL
2At this, source electrode driver 502 is in order to produce to drive the required source voltage VS in pixel column unit 510 and 520
1~VS
N503 of gate drivers are in order to produce the required signal SG in switch pixel column unit 510 and 520
1With SG
N
Fig. 6 illustrates and is the analog waveform figure in order to key diagram 5 embodiment.For convenience of description, be example with pixel column unit 510 with switch unit 530, and be depicted as shown in Fig. 7 A, and Fig. 7 A more indicates node voltage VD
1With VC
1Please refer to Fig. 6 and Fig. 7 A, pixel cell PI
1By sweep trace GL
1Receive signal SG
1, and by data line SL
1Reception sources pole tension VS
1530 of switch units are according to a level switching signal SC
1And determine the conducting state of its first end and second end, and level switching signal SC
1Can provide by gate drivers 503, or provide by other members according to design.It should be noted that switch unit 530 comprises a switch SW at least
55
At signal SG
1By low level V
LSwitch to high level V
HBefore, just at signal SG
1Before the high transition, switch unit 530 can be according to level switching signal SC
1(such as logical one) and its first end of conducting and second end.Therefore, as signal SG
1Be high level V
HThe time, memory circuit (liquid crystal capacitance C
51) second end be electrically connected to common voltage Vcom, and node voltage VC
1Level also change to the level of common voltage Vcom thereupon.At the same time, because switch SW
51Conducting, so source voltage VS
1To memory circuit (liquid crystal capacitance C
51) charging, cause node voltage VD
1Level change to source voltage VS
1Level.
At signal SG
1By high level V
HSwitch to low level V
LBefore, just at signal SG
1Before the low transition, switch unit 530 can be according to level switching signal SC
1(such as logical zero) and disconnect its first end and second end.At this moment, the pixel cell PI that is illustrated with reference to Fig. 7 B
1Fundamental diagram, if memory circuit (liquid crystal capacitance C
51) second end be electrically connected to common voltage Vcom (VC forever
1=Vcom), then as signal SG
1By high level V
HSwitch to low level V
LThe time, signal SG
1Formed pressure differential deltap V
GPTo be stored in liquid crystal capacitance C respectively according to the dividing potential drop theorem
51With stray capacitance C
Gd1In.In other words, this moment node voltage VD
1Level can change, relatively, be stored in memory circuit (liquid crystal capacitance C
51) in the quantity of electric charge also will change node voltage VD wherein thereupon
1Variation be Δ VD
1=Δ V
GP* C
Gd1/ (C
Gd1+ C
51).
Review the embodiment of present embodiment, as signal SG
1By high level V
HSwitch to low level V
LThe time, because memory circuit (liquid crystal capacitance C
51) second end under the state of suspension joint (floating), therefore based on principle of charge conservation, the node voltage VD of this moment
1With VC
1The level pressure differential deltap V that all can descend
GP(as shown in Figure 6).Thus, at signal SG
1The front and back of low transition are stored in memory circuit (liquid crystal capacitance C
51) in the quantity of electric charge there is no change.In other words, pixel cell 510 will be not can be along with the generation of feedthrough effect, and change the demonstration GTG of display panel 501.
Other pixel cell PI in the pixel column unit 510
2~PI
N, also be the control that cooperates switch unit 530, at signal SG
1Receive common voltage Vcom before the high transition, and at signal SG
1Switch to the state of suspension joint before the low transition.By this, reach as pixel cell PI
1Operation mechanism, and then eliminate the flicker noise of display panel 501.
Continuation is with reference to Fig. 5, and the mutual operation mechanism of pixel column unit 520 and switch unit 540 is as the mutual operation mechanism of above-mentioned pixel column unit 510 with switch unit 530.At this, switch unit 540 also is according to a level switching signal SC
2And determine the conducting state of its first end and second end, and level switching signal SC
2Can provide by gate drivers 503, or be provided by other members according to design.It should be noted that switch unit 540 comprises a switch SW at least
56
Switch unit 540 is at level switching signal SC
2Control under, cause pixel cell PII
2~PII
NAt signal SG
2Receive common voltage Vcom before the high transition, and at signal SG
2Switch to the state of suspension joint before the low transition.Thus, at signal SG
2After before the low transition, by stray capacitance (such as C
Gd3, C
Gd4) the feedthrough effect that caused, can't change and be stored in memory circuit (such as liquid crystal capacitance C
53, C
54) in the quantity of electric charge.By that analogy, the arbitrary pixel column unit in the display panel 501 can be known by inference, under the control of pairing switch unit, the flicker noise that the feedthrough effect is caused can be eliminated.
Fig. 8 illustrates the structural representation into the LCD of foundation one embodiment of the invention.With reference to Fig. 8, LCD 800 comprises display panel 801, driver element 802 and a plurality of switch unit.Wherein display panel 801 comprises a plurality of pixel columns unit.For clear each member of expression, show switch unit 803 and 804 and pixel column unit 810 and 820 at this.Because Fig. 8 embodiment is the extension of Fig. 5 embodiment, so each the pixel column unit in the display panel 801, structurally all identical with pixel column unit among Fig. 5 embodiment, just do not add to give unnecessary details at this.
Yet display panel 801 is with the maximum difference of display panel 501, does not dispose switch unit in the display panel 801.But in order to reach the effect of display panel 501, Fig. 8 embodiment utilization is configured in a plurality of switch units (such as switch unit 803 and 804) outside the display panel 801, carries out the function that a plurality of switch units (such as switch unit 530 and 540) are possessed in the display panel 501.
Therefore, the overall architecture of Fig. 8 embodiment is similar to Fig. 5 embodiment.Pixel column unit 810 is serially connected in sweep trace GL
1With level switch line CL
1Between.Pixel column unit 820 is serially connected in sweep trace GL
2With level switch line CL
2Between.First end of switch unit 803 is in order to receive common voltage Vcom, and second end of switch unit 803 then is electrically connected at level switch line CL
1And first end of switch unit 804 is in order to receive common voltage Vcom, and second end of switch unit 804 then is electrically connected to level switch line CL
2In addition, driver element 802 is electrically connected to display panel 801.
Illustrate further, above-mentioned driver element 802 comprises source electrode driver 830 and gate drivers 840.Source electrode driver 830 is electrically connected to data line SL
1~SL
N, gate drivers 840 then is electrically connected to sweep trace GL
1With GL
2It should be noted that each switch unit in the LCD 800 all comprises a switch at least.Comprise switch SW such as switch unit 803
81, switch unit 804 comprises switch SW
82
Continuation is with reference to Fig. 8, and source electrode driver 830 drives the required source voltage VS in pixel column unit 810 and 820 in order to produce
1~VS
N840 of gate drivers are in order to produce the required signal SG in switch pixel column unit 810 and 820
1With SG
2In addition, switch unit 803 and 804 is respectively according to level switching signal SC
1With SC
2, and determine the conducting state of its first end and second end.Level switching signal SC wherein
1With SC
2Can provide by gate drivers 840, or provide by other members according to design.
As signal SG
1Switch to before the high level by low level, just at signal SG
1Before the high transition, switch unit 803 can be according to level switching signal SC
1And its first end of conducting and second end.In this, pixel column unit 810 is a reference point with common voltage Vcom, receives the source voltage VS from source electrode driver 830
1~VS
N
Yet, as signal SG
1Switch to before the low level by high level, just at signal SG
1Before the low transition, switch unit 803 can be according to level switching signal SC
1And disconnect its first end and second end.In this, because pixel column unit 810 switches to the state of suspension joint, so the flicker noise that the feedthrough effect is caused will be suppressed.By that analogy, the mutual operation mechanism of pixel column unit 820 and switch unit 804.As for other details of present embodiment, described embodiment before being encompassed in does not add narration at this.
In sum, the present invention utilizes switch unit to control the time point that the pixel column unit receives common voltage.Thus, after before the low transition of signal, the demonstration GTG of display panel will not be subjected to the influence of feedthrough effect.In other words, the present invention not only can reduce the flicker noise of display panel, also can promote the picture quality that LCD presents.
Though the present invention discloses as above with preferred embodiment; right its is not in order to limit the present invention; have in the technical field under any and know the knowledgeable usually; without departing from the spirit and scope of the present invention; when can doing a little change and retouching, so protection scope of the present invention is when with being as the criterion that claim was defined.