CN102411893A

CN102411893A - Pixel driving circuit

Info

Publication number: CN102411893A
Application number: CN2011103609107A
Authority: CN
Inventors: 何小祥
Original assignee: Sichuan CCO Display Technology Co Ltd
Current assignee: Sichuan CCO Display Technology Co Ltd
Priority date: 2011-11-15
Filing date: 2011-11-15
Publication date: 2012-04-11
Anticipated expiration: 2031-11-15
Also published as: CN102411893B

Abstract

The invention discloses a pixel driving circuit, which comprises six transistors and a storage capacitor, wherein the source of a first transistor, the source of a third transistor and the drain of a sixth transistor are connected together, and are connected with a power wire through a luminescent device; the grid of the first transistor is connected with one end of the storage capacitor; the other end of the storage capacitor is connected with the drain of a fifth transistor; the source of the fifth transistor is connected with a data wire; the grids of the fifth transistor and a fourth transistor are connected with a first control scanning line; the drain of the fourth transistor is connected with the grid of the first transistor; the source of the fourth transistor is connected with the drain of the first transistor and the source of the second transistor; the grids of the second transistor and the third transistor are connected with a second control scanning line; and the drain of the third transistor is connected with the drain of the fifth transistor. In the driving circuit disclosed by the invention, threshold voltage drift and rising of two sections of voltages of the luminescent device can be compensated under the storage actions of the six transistors and the storage capacitor.

Description

A kind of pixel-driving circuit

Technical field

The invention belongs to display technique field, plane, be specifically related to a kind of design of pixel-driving circuit.

Background technology

(Active Matrix/Organic Light Emitting Diode AMOLED) is the active matrix organic light-emitting diode (AMOLED) panel to the active matrix organic light-emitting diode (AMOLED) panel.Compare traditional liquid crystal panel, AMOLED has characteristics such as reaction velocity is very fast, contrast is higher, the visual angle is wider.

Traditional voltage programming type AMOLED pixel-driving circuit comprises two thin film transistor (TFT)s and a MM CAP, one of them switching TFT, a drive TFT.When sweep trace was opened, external circuit was sent into voltage signal and is stored in the MM CAP via switching TFT, and this voltage signal controlling and driving TFT conducting size of current has also just determined the GTG of OLED; When sweep trace was closed, the voltage that is stored in the MM CAP still can keep drive TFT in conducting state, so can in an image time, keep the fixed current of OLED.Here, the brightness of OLED with flow through its proportional relation of electric current I, I=K (Vgs-Vth) ², wherein, Vgs is a gate source voltage, and Vth is a threshold voltage, and K is a coefficient entry, can find out, and the variation of Vth can cause the variation of electric current I, finally is presented as the variation of OLED brightness.

In addition, when luminous, OLED and driving tube are connected in the same loop, and the variation of the voltage Voled at OLED two ends just causes the variation of driving tube Vgs, can be known by following formula, and the variation of Vgs also can cause the variation of electric current I, finally also are presented as the variation of OLED brightness.

But because technology and aging, the variation of Vth and Voled is inevitably, is specially the drift of threshold voltage vt h, the rising of the voltage Voled at OLED two ends, thus cause AMOLED to shield the decline of display quality.The compensation of existing most of pixel-driving circuits all is the compensation to threshold voltage vt h drift, seldom relates to simultaneously the compensation to the rising of Voled.At document: Joon-Chul Goh; Jin Jang; Kyu-Sik Cho; Choong-Ki Kim.ANew a-Si:H Thin-Film Transistor Pixel Circuit for Active-Matrix Organic Light-Emitting Diodes; IEEE Electron Device Letters; 2003,24 (9): 583-585 has proposed a kind of AMOLED pixel-driving circuit; Same, this pixel-driving circuit also can only compensate the Vth drift.

Summary of the invention

The objective of the invention is to have proposed a kind of pixel-driving circuit in order to solve the defective that above-mentioned prior art exists.

Technical scheme of the present invention is: a kind of pixel-driving circuit; Comprise the first transistor, transistor seconds, the 3rd transistor, the 4th transistor, the 5th transistor, the 6th transistor, MM CAP and luminescent device; Wherein, The source electrode of the first transistor, the 3rd transistorized source electrode and the 6th transistor drain link together, and link to each other with power lead through luminescent device; The grid of the first transistor links to each other with an end of MM CAP, and the other end of MM CAP links to each other with the 5th transistor drain, and the 5th transistorized source electrode connects data line, and the 5th transistorized grid connects the first gated sweep line; The 4th transistor drain links to each other with the grid of the first transistor, and the 4th transistorized source electrode links to each other with the drain electrode of the first transistor, the source electrode of transistor seconds, and the 4th transistorized grid connects the first gated sweep line; The grid of transistor seconds connects the second gated sweep line, and the drain electrode of transistor seconds connects negative supply; The 3rd transistorized grid connects the second gated sweep line, and the 3rd transistor drain links to each other with the 5th transistor drain; The 6th transistorized source electrode connects power lead, and the 6th transistorized grid connects outside control signal.

Beneficial effect of the present invention: pixel-driving circuit of the present invention is by six transistors and the memory action through MM CAP; Can be simultaneously the rising of the voltage Voled at threshold voltage vt h drift and luminescent device two ends be compensated, and then can improve the display quality of luminescent device.

Figure of description

Fig. 1 is the circuit diagram of pixel-driving circuit of the present invention.

Fig. 2 is the waveform synoptic diagram of pixel-driving circuit of the present invention.

Embodiment

Below in conjunction with accompanying drawing and concrete embodiment the present invention is done further elaboration.

Pixel-driving circuit of the present invention is as shown in Figure 1; Comprise the first transistor TD, transistor seconds T2, the 3rd transistor T 3, the 4th transistor T 4, the 5th transistor T 5, the 6th transistor T 6, MM CAP CC and luminescent device; Wherein, The drain electrode of the source electrode of the source electrode of the first transistor TD, the 3rd transistor T 3 and the 6th transistor T 6 links together, and links to each other with power lead Vdd through luminescent device; The grid of the first transistor TD links to each other with the end A of MM CAP CC, and the other end B of MM CAP links to each other with the drain electrode of the 5th transistor T 5, and the source electrode of the 5th transistor T 5 meets data line Vdata, and the grid of the 5th transistor T 5 meets the first gated sweep line S1; The drain electrode of the 4th transistor T 4 links to each other with the grid of the first transistor TD, and the source electrode of the 4th transistor T 4 links to each other with the drain electrode of the first transistor T1, the source electrode of transistor seconds T2, and the grid of the 4th transistor T 4 meets the first gated sweep line S1; The grid of transistor seconds T2 meets the second gated sweep line S2, and the drain electrode of transistor seconds T2 meets negative supply Vss; The grid of the 3rd transistor T 3 meets the second gated sweep line S2, and the drain electrode of the 3rd transistor T 3 links to each other with the drain electrode of the 5th transistor T 5; The source electrode of the 6th transistor T 6 connects power lead, and the 6th transistorized grid T6 meets outside control signal C1.

Concrete, the luminescent device Organic Light Emitting Diode here; Transistor is a polycrystalline SiTFT.Outside control signal C1 used in the charging stage, can avoid the luminescent device flicker.

Pixel-driving circuit of the present invention is divided into the stage circuit operation and realizes the compensation to Vth and Voled, and concrete waveform synoptic diagram is as shown in Figure 2:

1 stage: the A point voltage is negative pressure Vss, and it is worth less than Vth, and the B point voltage is Vdata.

2 stages: Vdd is to A point input voltage, makes V _AC=Vth, B point voltage are Vdata.

3 stages: closeall switching tube, Vdata saltus step in this process.

The voltage jump amount that 4 stages: B is ordered is V _CThe voltage jump amount that-Vdata, A are ordered is similarly V _C-Vdata.This moment, the A point voltage was Vdd+Vth+V _C-Vdata.

Because of I=K (Vgs-Vth) ², Vgs-Vth=Vdd-Vdata.In the process of Vgs-Vth cancellation Vth and V _C, and Vdd-V _C=Voled.By on can get, in the stage process, eliminated the variation of Vth and Voled.Specify as follows:

In 2 stages, the T4 conducting, the A point is charged to V through T4 _C+ Vth, the A end of MM CAP CC has write down the threshold voltage vt h of TD, i.e. V _A-V _C=Vth, Vth phase cancellation in 4 stages all can repeat this action at every two field picture, has promptly eliminated the variation of Vth.In use Voled can slowly rise, thereby causes the variation of the Vgs of TD, writes down V through T3 in 4 stages _C, the B end record Vc at this moment of MM CAP CC, the voltage jump of the B end of the MM CAP CC of this moment is V _C-Vdata, according to the characteristic of electric capacity, corresponding saltus step V can take place in the A of MM CAP CC end simultaneously _C-Vdata realize that promptly the A that transfers to the Vc of this moment MM CAP CC holds, and the A end is connected the grid of TD, Vgs=Vg-Vs=V _A-V _CThereby, cancellation V _C, i.e. cancellation the variation of Voled.

Can find out that to sum up pixel-driving circuit of the present invention can be simultaneously compensates the rising of the voltage Voled at threshold voltage vt h drift and luminescent device two ends, and then can improve the display quality of luminescent device.

Those of ordinary skill in the art will appreciate that embodiment described here is in order to help reader understanding's principle of the present invention, should to be understood that protection scope of the present invention is not limited to such special statement and embodiment.Those of ordinary skill in the art can make various other various concrete distortion and combinations that do not break away from essence of the present invention according to these teachings disclosed by the invention, and these distortion and combination are still in protection scope of the present invention.

Claims

1. pixel-driving circuit; It is characterized in that; Comprise the first transistor, transistor seconds, the 3rd transistor, the 4th transistor, the 5th transistor, the 6th transistor, MM CAP and luminescent device; Wherein, the source electrode of the first transistor, the 3rd transistorized source electrode and the 6th transistor drain link together, and link to each other with power lead through luminescent device; The grid of the first transistor links to each other with an end of MM CAP, and the other end of MM CAP links to each other with the 5th transistor drain, and the 5th transistorized source electrode connects data line, and the 5th transistorized grid connects the first gated sweep line; The 4th transistor drain links to each other with the grid of the first transistor, and the 4th transistorized source electrode links to each other with the drain electrode of the first transistor, the source electrode of transistor seconds, and the 4th transistorized grid connects the first gated sweep line; The grid of transistor seconds connects the second gated sweep line, and the drain electrode of transistor seconds connects negative supply; The 3rd transistorized grid connects the second gated sweep line, and the 3rd transistor drain links to each other with the 5th transistor drain; The 6th transistorized source electrode connects power lead, and the 6th transistorized grid connects outside control signal.

2. pixel-driving circuit according to claim 1 is characterized in that described luminescent device is specially Organic Light Emitting Diode.

3. pixel-driving circuit according to claim 1 and 2 is characterized in that, described transistor is a polycrystalline SiTFT.