CN104318894B - Pixel circuit driving method - Google Patents

Pixel circuit driving method Download PDF

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Publication number
CN104318894B
CN104318894B CN201410522250.1A CN201410522250A CN104318894B CN 104318894 B CN104318894 B CN 104318894B CN 201410522250 A CN201410522250 A CN 201410522250A CN 104318894 B CN104318894 B CN 104318894B
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transistor
voltage
input
pole
grid
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CN201410522250.1A
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Chinese (zh)
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CN104318894A (en
Inventor
龙春平
田宏伟
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京东方科技集团股份有限公司
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    • GPHYSICS
    • G09EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09GARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/20Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
    • G09G3/22Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources
    • G09G3/30Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels
    • G09G3/32Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED]
    • GPHYSICS
    • G09EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09GARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/20Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
    • G09G3/22Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources
    • G09G3/30Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels
    • G09G3/32Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED]
    • G09G3/3208Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED] organic, e.g. using organic light-emitting diodes [OLED]
    • G09G3/3225Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED] organic, e.g. using organic light-emitting diodes [OLED] using an active matrix
    • G09G3/3233Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED] organic, e.g. using organic light-emitting diodes [OLED] using an active matrix with pixel circuitry controlling the current through the light-emitting element

Abstract

The embodiments of the invention provide a pixel circuit driving method, and relates to the field of a display technology, for solving the problem of affected driving current flowing through a luminescent device when ohm voltage drop of a first voltage end and the grid source voltage driving a transistor generate nonlinear change. The pixel circuit comprises a first transistor, a second transistor, a third transistor, a fourth transistor, a fifth transistor, a sixth transistor, a storage capacitor and the luminescent device.

Description

A kind of driving method of image element circuit

Technical field

The present invention relates to display technology field, more particularly, to a kind of driving method of image element circuit.

Background technology

Rapidly improving with Display Technique, the semiconductor component technology as display device core is also flown therewith The progress of jump property.For existing display device, Organic Light Emitting Diode (Organic Light Emitting Diode, OLED) as a kind of current mode luminescent device, the self-luminous having because of it, quick response, wide viewing angle and can make On flexible substrates the features such as and be applied to more and more in the middle of high-performance display field.

OLED display be may be constructed using above-mentioned OLED, the array base palte of this display is provided with multiple TFT (Thin Film Transistor, thin film transistor (TFT)).In order to improve the carrier mobility of TFT, and reduce resistivity so that During by same current, power consumption is less.Polysilicon is typically adopted to constitute above-mentioned TFT.Yet with production technology and polysilicon Characteristic, when leading to the TFT switch circuit making in large-area glass substrate, usually in threshold voltage vt h, mobility etc. Fluctuation is occurred on electrical parameter, so that the electric current flowing through OLED not only can be produced with the long-time conducting of TFT The change of conducting voltage stress and change, and its also can with TFT threshold voltage vt h drift about and different.Such one Come, it will have influence on brightness uniformity and the brightness constancy of display.Thus reducing picture quality and the quality of display.

Content of the invention

Embodiments of the invention provide a kind of driving method of image element circuit, can improve display display brightness uneven Bad phenomenon.

For reaching above-mentioned purpose, embodiments of the invention adopt the following technical scheme that:

The one side of the embodiment of the present invention, provides a kind of image element circuit, including:The first transistor, transistor seconds, the 3rd Transistor, the 4th transistor, the 5th transistor, the 6th transistor, storage capacitance and luminescent device;

The grid of described the first transistor connects LED control signal input, and the first pole connects the one of described storage capacitance End, the second pole is connected with reference voltage end;

The grid of described transistor seconds connects reset signal input, and the first pole connects the another of described storage capacitance End, the second pole is connected with described reference voltage end;

The grid of described third transistor connects grid line, and the first pole connects data wire, the second pole and described storage capacitance One end is connected;

The grid described grid line of connection of described 4th transistor, the other end of the first described storage capacitance of pole connection, second Pole is connected with the second pole of described 5th transistor;

The grid of described 5th transistor connects the other end of described storage capacitance, and the first pole connects first voltage end, the Two poles are connected with the second pole of described 4th transistor;

The grid of described 6th transistor connects described LED control signal input, and the first pole connects described 5th crystal Second pole of pipe, the second pole connects the anode of described luminescent device;

The negative electrode of described luminescent device connects second voltage end.

The another aspect of the embodiment of the present invention, provides a kind of display device to include any one pixel electricity as above Road.

The another aspect of the embodiment of the present invention, provides a kind of pixel circuit drive method, appoints as above including driving Anticipate a kind of method of image element circuit, methods described also includes:

Conducting transistor seconds, the voltage signal that reference voltage end is inputted transmits to the grid of the 5th transistor, and deposits Enter in storage capacitance;

Conducting third transistor, the data voltage that data wire is inputted is transmitted to the described 3rd by described third transistor Second pole of transistor, and preserve to described storage capacitance;Turn on the 4th transistor, by the grid of described 5th transistor and Second pole is turned on, and carries out voltage write to the grid of described 5th transistor;

Conducting the first transistor, described 5th transistor and the 6th transistor, by described 5th transistor and described the The electric current driven for emitting lights device of six transistors lights.

The embodiment of the present invention provides a kind of driving method of image element circuit, and wherein said image element circuit passes through multiple transistors And a storage capacitance is switched to circuit and charge and discharge control.Specifically, as the 5th transistor of driving transistor One end be directly connected with first voltage end, and in image element circuit introduce reference voltage so that flowing through the driving of luminescent device Electric current is only relevant in the data voltage of above-mentioned reference voltage data line input.So.Luminous organ can not only avoided Part is affected by threshold voltage, can also avoid the ohmic voltage drop at first voltage end that the driving current flowing through luminescent device is produced Raw impact, additionally due to the 5th transistor is directly connected with first voltage end, it is to avoid the gate source voltage of the 5th transistor goes out Existing nonlinear change, thus produce impact to the driving current flowing through luminescent device.In sum, the pixel electricity that the present invention provides The uniformity of display device display brightness can be improved in road.

Brief description

In order to be illustrated more clearly that the embodiment of the present invention or technical scheme of the prior art, below will be to embodiment or existing Have technology description in required use accompanying drawing be briefly described it should be apparent that, drawings in the following description be only this Some embodiments of invention, for those of ordinary skill in the art, on the premise of not paying creative work, acceptable Other accompanying drawings are obtained according to these accompanying drawings.

Fig. 1 is a kind of structural representation of image element circuit provided in an embodiment of the present invention;

Fig. 2 is a kind of control signal sequential chart of image element circuit provided in an embodiment of the present invention;

Fig. 3-Fig. 5 is a kind of connection diagram in each stage for the image element circuit provided in an embodiment of the present invention;

Fig. 6 is a kind of driving method flow chart of image element circuit provided in an embodiment of the present invention.

Specific embodiment

Below in conjunction with the accompanying drawing in the embodiment of the present invention, the technical scheme in the embodiment of the present invention is carried out clear, complete Site preparation description is it is clear that described embodiment is only a part of embodiment of the present invention, rather than whole embodiments.It is based on Embodiment in the present invention, it is every other that those of ordinary skill in the art are obtained under the premise of not making creative work Embodiment, broadly falls into the scope of protection of the invention.

The embodiment of the present invention provides a kind of image element circuit, as shown in figure 1, the first transistor T1, the second crystal can be included Pipe T2, the 3rd crystal T3 pipe, the 4th transistor T4, the 5th transistor T5, the 6th transistor T6, storage capacitance Cst and luminous Device D.

Wherein, the grid of the first transistor T1 connects LED control signal input Em, and the first pole connects storage capacitance Cst (node a), the second pole is connected with reference voltage end Vref for one end.

The grid of transistor seconds T2 connects reset signal input Reset, and the first pole connects the another of storage capacitance Cst (node b), the second pole is connected with described reference voltage end Vref at end.

The grid of third transistor T3 connects grid line Gate, and the first pole connects data wire Data, the second pole and described storage (node a) is connected for one end of electric capacity Cst.

The grid of the 4th transistor T4 connects grid line Gate, the first pole connect storage capacitance Cst the other end (node b), Second pole is connected with second pole of described 5th transistor T5.

The grid of the 5th transistor T5 connects the other end of storage capacitance Cst, and (node b), (node c) connects for the first pole One voltage end Vdd, (node d) is connected with second pole of the 4th transistor T4 for the second pole.

The grid of the 6th transistor T6 connects described LED control signal input Em, and the first pole connects the 5th transistor T5 The second pole, second pole connect luminescent device D anode.

The negative electrode of luminescent device D connects second voltage end Vss.

It should be noted that the luminescent device D in the embodiment of the present invention can be prior art includes LED (Light Emitting Diode, light emitting diode) or OLED (Organic Light Emitting Diode, Organic Light Emitting Diode) In interior multiple electric current driven for emitting lights devices.In embodiments of the present invention, it is the explanation carrying out taking OLED as a example.

The embodiment of the present invention provides a kind of image element circuit, by multiple transistors and a storage capacitance, circuit is carried out Switch and charge and discharge control.Specifically, the 5th transistor one end as driving transistor is directly connected with first voltage end, and Introduce reference voltage so that the driving current flowing through luminescent device is only defeated in above-mentioned reference voltage data line in image element circuit The data voltage entering is relevant.So.Luminescent device can not only avoided to be affected by threshold voltage, can also avoided The ohmic voltage drop of one voltage end produces impact to the driving current flowing through luminescent device, additionally due to the 5th transistor directly with First voltage end is connected, it is to avoid nonlinear change in the gate source voltage of the 5th transistor, thus to flowing through luminescent device Driving current produce impact.In sum, the image element circuit that the present invention provides can improve the equal of display device display brightness Even property.

It should be noted that first, in embodiments of the present invention, the voltage of first voltage end Vdd input can be high electricity Pressure, the voltage of second voltage end Vss input can be low-voltage or earth terminal.

Second, according to the difference of transistor channel type, transistor can be divided into p channel transistor (referred to as P-type crystal Pipe) and N-channel transistor (referred to as N-type transistor).Therefore for the transistor in above-mentioned image element circuit, the first transistor T1, transistor seconds T2, third transistor T3, the 4th transistor T4, the 5th transistor T5 and the 6th transistor T6 can be P Transistor npn npn.

Or,

The first transistor T1, transistor seconds T2, third transistor she, the 4th transistor T4, the 5th transistor T5 and Six transistor T5 can be N-type transistor.

Additionally, according to the difference of transistor conductivity mode, the transistor in above-mentioned image element circuit can be divided into enhancement mode Transistor and depletion mode transistor and, for enhancement mode TFT, threshold voltage vt h is on the occasion of and for depletion type TFT, threshold value Voltage Vth is negative value.

The embodiment of the present invention be with the first transistor T1, transistor seconds T2, third transistor T3, the 4th transistor T4, The explanation that 5th transistor T5 and the 6th transistor T6 is carried out as a example being p-type depletion mode transistor.Wherein, the first transistor T1, transistor seconds T2, third transistor T3, the 4th transistor T4, first pole of the 5th transistor T5 and the 6th transistor T6 It is source class, the second pole is drain.In the case, the voltage signal of above-mentioned reference voltage end Vref input is low-voltage, And threshold voltage vt h is negative value.

When using different types of transistor, the external control signal of image element circuit is also different.And control letter Number sequential be also not quite similar.For example when the first transistor T1, transistor seconds T2, third transistor T3, the 4th transistor T4, When 5th transistor T5 and the 6th transistor T6 is N-type transistor.Above-mentioned reference voltage end Vref needs the voltage letter of input Number be high level.And, the sequential of its each control signal and the corresponding signal sequence shown in Fig. 2 contrary (i.e. the two Phase contrast is 180 degree).

Below in conjunction with sequential Fig. 2, the work process of image element circuit provided in an embodiment of the present invention is described in detail.

When image element circuit shown in Fig. 1 works, its work process specifically can be divided into three phases, is specifically as follows:

Reset phase P1, as shown in figure 3, wherein, actual conductive track and device are using real for the equivalent circuit diagram in this stage Line represents, the part being not powered on is adopted and is represented by dashed line, and following equivalent circuit diagram is with to the figure shows mode identical.In reset phase P1, reset signal end Reset input low level, transistor seconds T2 is turned on, the grid voltage Vg setting of the 5th transistor T5 The voltage inputting for reference voltage end Vref, and this voltage is stored in storage capacitance Cst.Because reference voltage Vref is low The grid voltage Vg of the 5th transistor T5 as driving transistor therefore can be resetted by level.In the case, Five transistor T5 are in cut-off state.

Because the voltage signal of grid line Gate input and the voltage signal of LED control signal input Em input are height Level.Therefore third transistor T3, the 4th transistor T4, the first transistor T1 and the 6th transistor T6 are in ending shape State.

In this stage, the grid voltage Vg due to the 5th transistor T5 is reset, so that the node b of image element circuit The previous frame voltage signal of upper residual is released, it is to avoid the residual voltage signal of previous frame is to next frame voltage signal not Good impact is it is ensured that the stability of node b current potential.

Write phase P2, the equivalent circuit diagram in this stage as shown in figure 4, in this stage, grid line Gate input low level, By third transistor T3 and the 4th transistor T4 conducting, the data voltage Vdata of data wire input is passed by third transistor T3 Transport to node a, and be stored in storage capacitance Cst.In the case of the 4th transistor T4 conducting, the drain electrode of the 5th transistor T5 (node d) and gate turn-on are so as to be in diode-connected state.The voltage of first voltage end Vdd input is through the 5th crystal After pipe T5, the level of fiveth transistor T5 itself a threshold voltage vt h lower than the voltage that first voltage end Vdd inputs is write Enter the grid of the 5th transistor T5, now, as driving transistor the 5th transistor T5 grid voltage Vg be Vdd- (- Vth).Wherein, because the 5th transistor T5 is p-type depletion mode transistor, therefore above-mentioned threshold voltage vt h is negative value.

Due to the voltage signal of reset signal end Reset input and the voltage letter of LED control signal input Em input Number be high level.Therefore, transistor seconds T2, the first transistor T1 and the 6th transistor T6 are in cut-off state.

Glow phase P3, as shown in figure 5, in this stage, LED control signal Em inputs the equivalent circuit diagram in this stage End input low level, by the first transistor T1 and the 6th transistor T6 conducting, the voltage of reference voltage end Vref input passes through section Point a is stored in storage capacitance Cst, because the boot strap of this storage capacitance Cst is so that node b produces a voltage increment, greatly Little for Vref-Vdata.In the case, the size of the grid voltage Vg of the 5th transistor T5 increased Vref-Vdata again, tool Body:

Vg (T5)=Vref-Vdata+Vdd- (- Vth);

Therefore, gate source voltage Vgs (the i.e. pressure between the voltage of gate node b and source node c of the 5th transistor T5 Difference) be:

Vgs (T5)=Vg-Vs=Vref-Vdata+Vdd- (- Vth)-Vdd=Vref-Vdata+Vth;

In the case, driving current I flowing through the 5th transistor T5 is:

I=K/2 (Vgs-Vth)2=K/2 (Vref-Vdata)2.

This driving current I driven for emitting lights device D is lighted.

As can be seen here, on the one hand, flow through driving current I of the 5th transistor T5 and the threshold voltage of the 5th transistor T5 Vth is unrelated, and therefore, above-mentioned image element circuit, it can be avoided that luminescent device D is affected by threshold voltage.

On the other hand, above-mentioned driving current I is also unrelated with the voltage of first voltage end Vdd input.If in above-mentioned compensation During, the signal that driving current I of OLED is inputted with first voltage end Vdd is relevant.So sending out in OLED In photoreduction process, have electric current always and flow through first voltage end Vdd, thus causing ohmic voltage drop (IR Drop) so that adjacent picture Element has a part of signal of first voltage end Vdd input, therefore leads to driving current I flowing through OLED to decline and occur GTG distortion.So, above-mentioned image element circuit can avoid due to first voltage end Vdd produce ohmic voltage drop luminous to flowing through The impact that device D produces.

Another aspect, the source electrode of the 5th transistor T5 is directly connected with first voltage end Vdd.If the 5th transistor T5 Extra transistor (not shown) is set and the Vdd of first voltage end between, then flow through the electric current of this extra transistor Produce voltage drop Vds ' at its source and drain end, so, the gate source voltage Vgs of the 5th transistor T5 should be Vdata+Vth- Vdd-Vds’.The size of Vds ' is determined by the electric current (i.e. driving current I of OLED) flowing through above-mentioned extra transistor, so And driving current I of OLED is also controlled by data voltage Vdata, so gate source voltage of the 5th transistor T5 Vgs will appear from nonlinear change, leads to pixel to show and GTG distortion.Thus the quality to display device and display effect Have adverse effect on.Therefore, above-mentioned image element circuit can eliminate between the 5th transistor T5 and first voltage end Vdd Transistor leads to the 5th transistor T5 as driving transistor, its gate source voltage Vgs nonlinear change, and sends out to flowing through Driving current I of optical device D produces impact.

To sum up residing, using image element circuit provided in an embodiment of the present invention, display device display brightness can be improved Uniformity.

Additionally, in this stage, the voltage signal of the voltage signal of grid line Gate input and reset signal end Reset input For high level.Therefore, third transistor T3, the 4th transistor T4 are in cut-off state with transistor seconds T2.

The embodiment of the present invention also provides a kind of display device, including any one image element circuit as above.Described aobvious Showing device can include multiple pixel unit array, and each pixel cell includes any one image element circuit as above. There is the image element circuit identical beneficial effect providing with present invention, due to image element circuit in the aforementioned embodiment Have been carried out describing in detail, here is omitted.

Specifically, the display device that the embodiment of the present invention is provided can be existed including light-emitting diode display or OLED display The interior display device with electric current driven for emitting lights device.

The embodiment of the present invention provides a kind of pixel circuit drive method, can include driving image element circuit as shown in Figure 1 Method, as shown in fig. 6, methods described can also include:

S101, as shown in figure 3, conducting transistor seconds T2, the voltage signal of reference voltage end Vef input is transmitted to the The grid of five transistor T5, and be stored in storage capacitance Cst.

S102, as shown in figure 4, conducting third transistor T3, the data voltage Vdata of data wire Data input is passed through the Three transistor T3 transmit to second pole (drain electrode) of third transistor T3, and preserve to storage capacitance Cst;Turn on the 4th crystal Pipe T4, the grid of the 5th transistor T5 and the second pole (drain electrode) is turned on, and is carried out electricity to the grid of the 5th transistor T5 Pressure write.

S103, conducting the first transistor T1, the 5th transistor T5 and the 6th transistor T6, by the 5th transistor T5 and the The electric current driven for emitting lights device D of six transistor T6 lights.

The embodiment of the present invention provides a kind of pixel circuit drive method, by the multiple transistors in image element circuit and One storage capacitance is switched to circuit and charge and discharge control.Specific inclusion:First, turn on transistor seconds, by reference The voltage signal of voltage end input transmits to the grid of the 5th transistor, and is stored in storage capacitance with the grid to the 5th transistor Pole is resetted, it is to avoid previous frame signal impacts to this frame signal;Then, turn on third transistor, data wire is inputted Data voltage transmitted by third transistor to the second pole of third transistor, and preserve to storage capacitance;Turn on the 4th Transistor, the grid of the 5th transistor and the second pole are turned on, so, the voltage of write the 5th transistor gate The voltage that size inputs for first voltage end deducts the threshold voltage of the 5th transistor;Finally, conducting the first transistor, the 5th crystalline substance Body pipe and the 6th transistor, are lighted by the electric current driven for emitting lights device of the 5th transistor and the 6th transistor.So, flow The driving current crossing luminescent device is only relevant in the data voltage of above-mentioned reference voltage data line input, thus can not only keep away Exempting from luminescent device is affected by threshold voltage, and the ohmic voltage drop that can also avoid first voltage end is to the drive flowing through luminescent device Streaming current produces impact.Additionally, the voltage of first voltage end input directly inputs value the 5th transistor, thus it is brilliant to avoid the 5th When nonlinear change in the gate source voltage of body pipe, and impact is produced on the driving current flowing through luminescent device.In sum, originally The control method of the image element circuit that inventive embodiments provide can improve the uniformity of display device display brightness.

It should be noted that the transistor in above-mentioned image element circuit:The first transistor T1, transistor seconds T2, trimorphism Body pipe T3, the 4th transistor T4, the 5th transistor T5 and the 6th transistor T6 can be P-type transistor.

Or,

The first transistor T1, transistor seconds T2, third transistor she, the 4th transistor T4, the 5th transistor T5 and Six transistor T5 can be N-type transistor.

Additionally, according to the difference of transistor conductivity mode, the transistor in above-mentioned image element circuit can be enhancement mode crystal Pipe or depletion mode transistor.

Wherein, the image element circuit in following examples is with the first transistor T1, transistor seconds T2, third transistor What T3, the 4th transistor T4, the 5th transistor T5 and the 6th transistor T6 were carried out as a example being p-type depletion mode transistor says Bright.The sequential of the control signal in the driving method of above-mentioned image element circuit can include:

Reset phase P1:The voltage signal of reset signal end Reset input is low level, the voltage letter of grid line Gate input Number, the voltage signal of the data voltage Vdata and LED control signal input Em input of data wire Data input be high electricity Flat.

Specifically, in reset phase P1, reset signal end Reset input low level, transistor seconds T2 is turned on, the 5th The grid voltage Vg of transistor T5 is set to the voltage of reference voltage end Vref input, and this voltage is stored in storage capacitance In Cst.Because reference voltage Vref is low level, therefore can be using the grid electricity of the 5th transistor T5 as driving transistor Pressure Vg is resetted.In the case, the 5th transistor T5 is in cut-off state.

Because the voltage signal of grid line Gate input and the voltage signal of LED control signal input Em input are height Level.Therefore third transistor T3, the 4th transistor T4, the first transistor T1 and the 6th transistor T6 are in ending shape State.

In this stage, the grid voltage Vg due to the 5th transistor T5 is reset, so that the node b of image element circuit The previous frame voltage signal of upper residual is released, it is to avoid the residual voltage signal of previous frame is to next frame voltage signal not Good impact is it is ensured that the stability of node b current potential.

Write phase P2:The voltage signal of grid line Gate input is low level, the data voltage of data wire Data input The voltage signal of the voltage signal of Vdata, reset signal end Reset input and LED control signal input Em input is height Level.

Specifically, in this stage, grid line Gate input low level, third transistor T3 and the 4th transistor T4 are led Logical, the data voltage Vdata of data wire input is transmitted to node a by third transistor T3, and is stored in storage capacitance Cst In.In the case of the 4th transistor T4 conducting, (node d) and gate turn-on are so as to be in two for the drain electrode of the 5th transistor T5 Pole pipe connection status.The voltage of first voltage end Vdd input, after the 5th transistor T5, will input than first voltage end Vdd The low 5th transistor T5 threshold voltage vt h of itself of voltage level write the 5th transistor T5 grid, now, make Grid voltage Vg for the 5th transistor T5 of driving transistor is Vdd- (- Vth).Wherein, because the 5th transistor T5 is p-type Depletion mode transistor, therefore above-mentioned threshold voltage vt h is negative value.

Due to the voltage signal of reset signal end Reset input and the voltage letter of LED control signal input Em input Number be high level.Therefore, transistor seconds T2, the first transistor T1 and the 6th transistor T6 are in cut-off state.

Glow phase P3:The electricity of data voltage Vdata, the LED control signal input Em input of data wire Data input Pressure signal is low level, and the voltage signal of grid line Gate input, the voltage signal of reset signal end Reset input are high level.

Specifically, as shown in figure 5, in this stage, LED control signal Em input is defeated for the equivalent circuit diagram in this stage Enter low level, by the first transistor T1 and the 6th transistor T6 conducting, the voltage of reference voltage end Vref input is deposited by node a Enter in storage capacitance Cst, because the boot strap of this storage capacitance Cst is so that node b produces a voltage increment, size is Vref-Vdata.In the case, the size of the grid voltage Vg of the 5th transistor T5 increased Vref-Vdata again, specifically 's:

Vg (T5)=Vref-Vdata+Vdd- (- Vth);

Therefore, gate source voltage Vgs (the i.e. pressure between the voltage of gate node b and source node c of the 5th transistor T5 Difference) be:

Vgs (T5)=Vg-Vs=Vref-Vdata+Vdd- (- Vth)-Vdd=Vref-Vdata+Vth;

In the case, driving current I flowing through the 5th transistor T5 is:

I=K/2 (Vgs-Vth)2=K/2 (Vref-Vdata)2.

This driving current I driven for emitting lights device D is lighted.

As can be seen here, on the one hand, flow through driving current I of the 5th transistor T5 and the threshold voltage vt h of the 5th transistor Unrelated, therefore, above-mentioned image element circuit, it can be avoided that luminescent device D is affected by threshold voltage.

On the other hand, above-mentioned driving current I is also unrelated with the voltage of first voltage end Vdd input.If in above-mentioned compensation During, the signal that driving current I of OLED is inputted with first voltage end Vdd is relevant.So sending out in OLED In photoreduction process, have electric current always and flow through first voltage end Vdd, thus causing ohmic voltage drop (IR Drop) so that adjacent picture Element has a part of signal of first voltage end Vdd input, therefore leads to driving current I flowing through OLED to decline and occur GTG distortion.So, above-mentioned image element circuit can avoid due to first voltage end Vdd produce ohmic voltage drop luminous to flowing through The impact that device D produces.

Another aspect, the source electrode of the 5th transistor T5 is directly connected with first voltage end Vdd.If the 5th transistor T5 Extra transistor (not shown) is set and the Vdd of first voltage end between, then flow through the electric current of this extra transistor Produce voltage drop Vds ' at its source and drain end, so, the gate source voltage Vgs of the 5th transistor T5 should be Vdata+Vth- Vdd-Vds’.The size of Vds ' is determined by the electric current (i.e. driving current I of OLED) flowing through above-mentioned extra transistor, so And driving current I of OLED is also controlled by data voltage Vdata, so gate source voltage of the 5th transistor T5 Vgs will appear from nonlinear change, leads to pixel to show and GTG distortion.Thus the quality to display device and display effect Have adverse effect on.Therefore image element circuit can eliminate and be located at the 5th transistor T5 and first voltage end in prior art Transistor between Vdd leads to the 5th transistor T5 as driving transistor, its gate source voltage Vgs nonlinear change, And impact is produced on driving current I flowing through luminescent device D.

To sum up residing, using image element circuit provided in an embodiment of the present invention, display device display brightness can be improved Uniformity.

Additionally, in this stage, the voltage signal of the voltage signal of grid line Gate input and reset signal end Reset input For high level.Therefore, third transistor T3, the 4th transistor T4 are in cut-off state with transistor seconds T2.

One of ordinary skill in the art will appreciate that:The all or part of step realizing said method embodiment can be passed through Completing, aforesaid program can be stored in a computer read/write memory medium the related hardware of programmed instruction, this program Upon execution, execute the step including said method embodiment;And aforesaid storage medium includes:ROM, RAM, magnetic disc or light Disk etc. is various can be with the medium of store program codes.

The above, the only specific embodiment of the present invention, but protection scope of the present invention is not limited thereto, and any Those familiar with the art the invention discloses technical scope in, change or replacement can be readily occurred in, all should contain Cover within protection scope of the present invention.Therefore, protection scope of the present invention should be defined by described scope of the claims.

Claims (4)

1. a kind of pixel circuit drive method is it is characterised in that described image element circuit includes:The first transistor, transistor seconds, Third transistor, the 4th transistor, the 5th transistor, the 6th transistor, storage capacitance and luminescent device;
The grid of described the first transistor connects LED control signal input, and the first pole connects one end of described storage capacitance, Second pole is connected with reference voltage end;
The grid of described transistor seconds connects reset signal input, and the first pole connects the other end of described storage capacitance, the Two poles are connected with described reference voltage end;
The grid of described third transistor connects grid line, and the first pole connects data wire, one end of the second pole and described storage capacitance It is connected;
The grid of described 4th transistor connects described grid line, and the first pole connects the other end of described storage capacitance, the second pole with Second pole of described 5th transistor is connected;
The grid of described 5th transistor connects the other end of described storage capacitance, and the first pole connects first voltage end, the second pole It is connected with the second pole of described 4th transistor;
The grid of described 6th transistor connects described LED control signal input, and the first pole connects described 5th transistor Second pole, the second pole connects the anode of described luminescent device;
The negative electrode of described luminescent device connects second voltage end;
The method driving described image element circuit includes:
Only turn on transistor seconds, the voltage signal that reference voltage end is inputted transmits to the grid of the 5th transistor, and is stored in In storage capacitance;
Conducting third transistor, the data voltage that data wire is inputted is transmitted to described 3rd crystal by described third transistor Second pole of pipe, and preserve to described storage capacitance;Turn on the 4th transistor, by the grid and second of described 5th transistor Pole is turned on, and carries out voltage write to the grid of described 5th transistor;
Conducting the first transistor, described 5th transistor and the 6th transistor, by described 5th transistor and described 6th crystalline substance The electric current driven for emitting lights device of body pipe lights.
2. pixel circuit drive method according to claim 1 it is characterised in that described the first transistor, described second It is brilliant that transistor, described third transistor, described 4th transistor, described 5th transistor and described 6th transistor are p-type Body pipe;Or,
Described the first transistor, described transistor seconds, described third transistor, described 4th transistor, described 5th crystal Pipe and described 6th transistor are N-type transistor.
3. pixel circuit drive method according to claim 1 and 2 is it is characterised in that described transistor includes depletion type Transistor or enhancement transistor.
4. pixel circuit drive method according to claim 2 it is characterised in that when described the first transistor, described the Two-transistor, described third transistor, described 4th transistor, described 5th transistor and described 6th transistor are p-type During depletion mode transistor, the sequential of control signal includes:
Reset phase:The voltage signal of reset signal end input is low level, and the voltage signal of grid line input, data wire input The voltage signal of data voltage and the input of LED control signal input is high level;
Write phase:The voltage signal of described grid line input is low level, the data voltage of described data wire input, described reset The voltage signal of the voltage signal of signal end input and the input of described LED control signal input is high level;
Glow phase:The data voltage of described data wire input, the voltage signal of described LED control signal input input are Low level, the voltage signal of described grid line input, the voltage signal of described reset signal end input are high level.
CN201410522250.1A 2014-09-30 2014-09-30 Pixel circuit driving method CN104318894B (en)

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