CN102411893B

CN102411893B - Pixel driving circuit

Info

Publication number: CN102411893B
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: 2013-11-13
Anticipated expiration: 2031-11-15
Also published as: CN102411893A

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

Traditional voltage-programming type AMOLED pixel-driving circuit comprises two thin film transistor (TFT)s and a memory capacitance, one of them switching TFT, a drive TFT.When sweep trace was opened, external circuit was sent into voltage signal and is stored in memory capacitance via switching TFT, and this voltage signal is controlled drive TFT On current size, had also just determined the GTG of OLED; When sweep trace was closed, the voltage that is stored in memory capacitance still can keep drive TFT in conducting state, therefore can keep the fixed current of OLED in an image time.Here, the brightness of OLED with flow through its proportional relation of electric current I, I=K (Vgs-Vth) ², wherein, Vgs is gate source voltage, and Vth is threshold voltage, and K is 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 circuit, and the variation of the voltage Voled at OLED two ends just causes the variation of driving tube Vgs, and by following formula as can be known, the variation of Vgs also can cause the variation of electric current I, finally also are presented as the variation of OLED brightness.

But due to technique 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 the AMOLED screen display to show the decline of quality.The compensation of existing most of pixel-driving circuits is all the compensation for 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, a kind of AMOLED pixel-driving circuit has been proposed, same, this pixel-driving circuit also can only compensate the Vth drift.

Summary of the invention

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

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, memory capacitance and luminescent device, wherein, the source electrode of the first transistor, the 3rd transistorized source electrode and the 6th transistorized drain electrode link together, and by luminescent device, with power lead, are connected; The grid of the first transistor is connected with an end of memory capacitance, and the other end of memory capacitance is connected with the 5th transistorized drain electrode, and the 5th transistorized source electrode connects data line, and the 5th transistorized grid connects the first gated sweep line; The 4th transistorized drain electrode is connected with the grid of the first transistor, and the 4th transistorized source electrode is connected 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 transistorized drain electrode is connected with the 5th transistorized drain electrode; 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 by memory capacitance, 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 schematic diagram of pixel-driving circuit of the present invention.

Embodiment

The invention will be further elaborated below in conjunction with accompanying drawing and concrete embodiment.

Pixel-driving circuit of the present invention 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, memory capacitance 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 by luminescent device, with power lead Vdd, is connected; The grid of the first transistor TD is connected with the end A of memory capacitance CC, and the other end B of memory capacitance is connected 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 is connected with the grid of the first transistor TD, and the source electrode of the 4th transistor T 4 is connected 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 is connected 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 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 quadravalence section circuit operation and realizes compensation to Vth and Voled, concrete waveform schematic diagram 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, to A point input voltage, makes V _AC=Vth, B point voltage are Vdata.

3 stages: closeall switching tube.

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 obtain, eliminated the variation of Vth and Voled in quadravalence section process.Be described as follows:

In 2 stages, the T4 conducting, the A point is charged to V by T4 _C+ Vth, the A end of memory capacitance CC has recorded 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, namely eliminated the variation of Vth.In use Voled can climbed, thereby causes the variation of the Vgs of TD, by T3, in 4 stages, records V _C, the B end record Vc at this moment of memory capacitance CC, the voltage jump of the B end of the memory capacitance CC of this moment is V _C-Vdata, according to the characteristic of electric capacity, corresponding saltus step V can occur in the A of memory capacitance CC end simultaneously _C-Vdata, realize that namely the A that the Vc of this moment is transferred to memory capacitance CC holds, and the A end is connected to the grid of TD, Vgs=Vg-Vs=V _A-V _CThereby, cancellation V _C, i.e. cancellation the variation of Voled.

In summary it can be seen, 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 be understood to 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 technology enlightenments 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, memory capacitance and luminescent device, wherein, the source electrode of the first transistor, the 3rd transistorized source electrode and the 6th transistorized drain electrode link together, and by luminescent device, with power lead, are connected; The grid of the first transistor is connected with an end of memory capacitance, and the other end of memory capacitance is connected with the 5th transistorized drain electrode, and the 5th transistorized source electrode connects data line, and the 5th transistorized grid connects the first gated sweep line; The 4th transistorized drain electrode is connected with the grid of the first transistor, and the 4th transistorized source electrode is connected 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 transistorized drain electrode is connected with the 5th transistorized drain electrode; The 6th transistorized source electrode connects power lead, and the 6th transistorized grid connects outside control signal;

The control signal of described outside, used in the charging stage, avoids the luminescent device flicker;

Described pixel-driving circuit is divided into quadravalence section circuit operation and realizes that detailed process is as follows to the compensation of the voltage Voled at the threshold voltage vt h of the first transistor and luminescent device two ends:

1 stage: the A point voltage is negative supply voltage Vss, and it is worth less than Vth, and the B point voltage is Vdata, and described A point is the grid of the first transistor, and described B point is the 5th transistorized drain electrode;

2 stages: power lead Vdd, to A point input voltage, makes V _AC=Vth, B point voltage are Vdata, and the C point is the source electrode of the first transistor;

3 stages: closeall switching tube;

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.

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 polycrystalline SiTFT.