CN213988254U

CN213988254U - Pixel compensation circuit

Info

Publication number: CN213988254U
Application number: CN202022606389.8U
Authority: CN
Inventors: 胡中艺; 吴锦坤; 王士锋; 胡君文
Original assignee: Truly Huizhou Smart Display Ltd
Current assignee: Truly Huizhou Smart Display Ltd
Priority date: 2020-11-11
Filing date: 2020-11-11
Publication date: 2021-08-17
Anticipated expiration: 2030-11-11

Abstract

The utility model discloses a pixel compensation circuit, through setting up first to sixth TFT pipe, light emitting device, electric capacity, the reference voltage end, first scanning signal end, the second scanning signal end, the data end, first luminous control end, the luminous control end of second, first power supply voltage end and second power supply voltage end, let sixth TFT pipe work in the saturation region, only the drive current Id size of going to control sixth TFT pipe by the voltage that data end VDATA provided, can compensate the threshold voltage Vth of each TFT pipe of pixel circuit, the size of drive current Id does not receive threshold voltage Vth's influence, just can let OLED display device's luminous luminance more even well.

Description

Pixel compensation circuit

Technical Field

The utility model relates to a pixel circuit technical field especially relates to a pixel compensation circuit.

Background

In recent years, with the development of Organic Light Emitting Device (OLED) technology, the Organic Light Emitting Device (OLED) has advantages of self-luminescence, no need of backlight, high contrast, short response time, thin thickness, wide viewing angle, and applicability to flexible and transparent Display, and the like.

The display device manufactured by the Organic Light Emitting Device (OLED) is called an OLED display device, in order to enable the OLED display device to display, a plurality of pixel circuits must be arranged in the OLED display device, each pixel circuit is composed of a plurality of TFT tubes (TFT tubes are thin film transistors), and due to the individual difference of the TFT tubes, even if the TFT tubes are of the same type, the threshold voltage of the TFT tubes is different due to the individual difference, if the same data voltage VDATA is used to supply power to each pixel circuit, different currents are generated in each pixel circuit, so that the overall luminance of the OLED display device is not uniform, and the display quality of the OLED display device is finally affected.

SUMMERY OF THE UTILITY MODEL

The utility model aims at overcoming the weak point among the prior art, providing a pixel compensation circuit, can compensate the threshold voltage of TFT pipe, improve OLED display device's display quality.

The purpose of the utility model is realized through the following technical scheme:

a pixel compensation circuit, comprising: the pixel circuit comprises first to sixth TFT tubes, light-emitting devices, a capacitor, a reference voltage end, a first scanning signal end, a second scanning signal end, a data end, a first light-emitting control end, a second light-emitting control end, a first power supply voltage end and a second power supply voltage end;

the grid electrode of the first TFT is respectively connected with the first scanning signal end and the grid electrode of the second TFT, the drain electrode of the first TFT is connected with the reference voltage end, and the source electrode of the first TFT is respectively connected with one end of the light-emitting device and the drain electrode of the fourth TFT;

the source electrode of the second TFT is respectively connected with the grid electrode of the sixth TFT and one end of the capacitor, and the drain electrode of the second TFT is respectively connected with the source electrode of the fourth TFT and the drain electrode of the sixth TFT;

the grid electrode of the third TFT is connected with the second scanning signal end, the source electrode of the third TFT is connected with the data end, and the drain electrode of the third TFT is respectively connected with the drain electrode of the fifth TFT and the source electrode of the sixth TFT;

the grid electrode of the fourth TFT is connected with the second light-emitting control end;

the grid electrode of the fifth TFT is connected with the first light-emitting control end, and the source electrode of the fifth TFT is respectively connected with the other end of the capacitor and the second power supply voltage end;

the other end of the light emitting device is connected to the first power supply voltage terminal.

In one embodiment, the light emitting device is a light emitting diode, an anode of the light emitting diode is connected to the first power voltage terminal, and a cathode of the light emitting diode is connected to the source of the first TFT and the drain of the fourth TFT, respectively.

In one embodiment, the second TFT is an oxide thin film transistor.

Compared with the prior art, the utility model discloses advantage and beneficial effect below having at least:

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings that are required to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present invention, and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained according to the drawings without inventive efforts.

Fig. 1 is a schematic circuit diagram of a pixel compensation circuit according to an embodiment of the present invention;

fig. 2 is a schematic diagram of a driving timing sequence of a pixel compensation circuit according to an embodiment of the present invention.

Detailed Description

In order to facilitate understanding of the present invention, the present invention will be described more fully hereinafter with reference to the accompanying drawings. The preferred embodiments of the present invention are shown in the drawings. The invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

It will be understood that when an element is referred to as being "secured to" another element, it can be directly on the other element or intervening elements may also be present. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may also be present. The terms "vertical," "horizontal," "left," "right," and the like as used herein are for illustrative purposes only and do not represent the only embodiments.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

Referring to fig. 1, a pixel compensation circuit 10 includes: first to sixth TFT tubes (i.e., T1, T2, T3, T4, T5 and T6 shown in fig. 1), a light emitting device EL, a capacitor Cst, a reference voltage terminal VINIT, a first SCAN signal terminal SCAN1, a second SCAN signal terminal SCAN2, a data terminal VDATA, a first light emission control terminal EM1, a second light emission control terminal EM2, a first power supply voltage terminal ELVDD and a second power supply voltage terminal ELVSS;

the grid electrode of the first TFT tube T1 is respectively connected to the grid electrodes of the first SCAN signal terminal SCAN1 and the second TFT tube T1, the drain electrode of the first TFT tube T1 is connected to the reference voltage terminal VINIT, and the source electrode of the first TFT tube T1 is respectively connected to one end of the light emitting device EL and the drain electrode of the fourth TFT tube T4;

the source electrode of the second TFT T2 is respectively connected to the gate electrode of the sixth TFT T6 and one end of the capacitor Cst, and the drain electrode of the second TFT T2 is respectively connected to the source electrode of the fourth TFT T4 and the drain electrode of the sixth TFT T6;

the grid electrode of the third TFT T3 is connected to the second SCAN signal terminal SCAN1, the source electrode of the third TFT T3 is connected to the data terminal VDATA, and the drain electrode of the third TFT T3 is connected to the drain electrode of the fifth TFT T5 and the source electrode of the sixth TFT T6, respectively;

the gate of the fourth TFT transistor T4 is connected to the second emission control terminal EM 2;

a gate electrode of the fifth TFT T5 is connected to the first emission control terminal EM1, and a source electrode of the fifth TFT T5 is connected to the other end of the capacitor Cst and the second power voltage terminal, respectively;

the other end of the light emitting device EL is connected to the first power voltage terminal ELVDD.

To better explain the circuit principle of the pixel compensation circuit 10, please refer to fig. 1 and fig. 2 together, fig. 2 shows a schematic diagram of the driving timing sequence of the pixel compensation circuit 10, fig. 2 shows a total of three stages, which are t1 stage, t2 stage and t3 stage respectively, and fig. 2 shows the level change of the first SCAN signal terminal SCAN1, the second SCAN signal terminal SCAN2, the first light-emitting control terminal EM1 and the second light-emitting control terminal EM2 in the three stages.

Firstly, at a stage T1, a first SCAN signal terminal SCAN1 is input at a high level, a second SCAN signal terminal SCAN2 is input at a low level, a first light-emitting control terminal EM1 is input at a low level, a second light-emitting control terminal EM2 is input at a high level, a first TFT tube T1, a second TFT tube T2 and a fourth TFT tube T4 are all turned on, and the rest of the TFT tubes are all turned off, wherein Vc is VINIT (Vc is a voltage at a point C shown in fig. 1, VINIT is a voltage at a reference voltage terminal VINIT shown in fig. 1), and the voltages at two ends of the light-emitting device EL are reset; vg ═ Vd ═ VINIT (Vg is the voltage at point g shown in fig. 1, and Vd is the voltage at point d shown in fig. 1);

next, at a stage T2, the first SCAN signal terminal SCAN1 is input at a high level, the second SCAN signal terminal SCAN2 is input at a high level, the first emission control terminal EM1 is input at a low level, and the second emission control terminal EM2 is input at a low level, at this time, the first TFT tube T1, the second TFT tube T2, and the third TFT tube T3 are all turned on, the remaining TFT tubes are turned off, Vg ═ Vd starts to discharge until Vg ═ Vd ═ VDATA + Vth (VDATA is a voltage of the data terminal VDATA shown in fig. 1, Vth is a threshold voltage of the sixth TFT tube T6 shown in fig. 1), and at this time, the voltage across the capacitor Cst is Vg-ELVSS ═ VDATA + Vth-ELVSS (ELVSS is a voltage of the second power supply voltage terminal ELVSS shown in fig. 1);

finally, during the period T3, i.e. the light emitting period, the fourth transistor T4 and the fifth transistor T5 are both turned on, and the rest of the TFT transistors are all turned off, and at this time, the voltage across the capacitor Cst remains unchanged and is just equal to the voltage of Vgs (Vgs is the voltage difference between g and s in fig. 1), which is VDATA + Vth-ELVSS, and the driving current Id of the sixth TFT transistor T6 can be calculated according to the following formula:

where μ is the electron mobility of the channel, Cox is the channel capacitance per unit area of the sixth TFT transistor T6, W is the channel width of the sixth TFT transistor T6, and L is the channel length of the sixth TFT transistor T6. The sixth TFT tube works in a saturation region, the driving current Id of the sixth TFT tube is controlled only by the voltage provided by the data end VDATA, the threshold voltage Vth of each TFT tube of the pixel circuit can be compensated, and the luminance of the OLED display device can be better uniform without the influence of the threshold voltage Vth on the magnitude of the driving current Id.

It should be noted that the circuit of the present embodiment uses N-type TFT transistors, and it is conceivable that the P-type TFT transistors can be easily conceived by those skilled in the art without creative efforts, and therefore, the present invention also falls within the protection scope of the present patent.

Further, referring to fig. 1 again, in one embodiment, the light emitting device EL is a light emitting diode, an anode of the light emitting diode is connected to the first power voltage terminal ELVDD, and a cathode of the light emitting diode is connected to the source electrode of the first TFT transistor T1 and the drain electrode of the fourth TFT transistor T4, respectively.

As described above, the light-emitting device EL is a light-emitting diode, but it is needless to say that another light-emitting device EL may be used instead of the light-emitting diode.

Further, referring to fig. 1 again, in one embodiment, the second TFT T2 is an oxide thin film transistor.

It should be noted that, at the stage T3, the second TFT T2 is in the off state, but there is still a leakage current, which will cause the Vg voltage to be unstable and cause the luminance to change, so that the second TFT T2 can be replaced by a TFT with smaller leakage current, such as an oxide thin film transistor, to make the leakage current of the second TFT T2 smaller.

The above-mentioned embodiments only represent some embodiments of the present invention, and the description thereof is specific and detailed, but not to be construed as limiting the scope of the present invention. It should be noted that, for those skilled in the art, without departing from the spirit of the present invention, several variations and modifications can be made, which are within the scope of the present invention. Therefore, the protection scope of the present invention should be subject to the appended claims.

Claims

1. A pixel compensation circuit, comprising: the pixel circuit comprises first to sixth TFT tubes, light-emitting devices, a capacitor, a reference voltage end, a first scanning signal end, a second scanning signal end, a data end, a first light-emitting control end, a second light-emitting control end, a first power supply voltage end and a second power supply voltage end;

2. The pixel compensation circuit of claim 1, wherein the light emitting device is a light emitting diode, an anode of the light emitting diode is connected to the first power voltage terminal, and a cathode of the light emitting diode is connected to the source of the first TFT and the drain of the fourth TFT, respectively.

3. The pixel compensation circuit of claim 1, wherein the second TFT transistor is an oxide thin film transistor.