CN213988253U

CN213988253U - Organic display module pixel circuit

Info

Publication number: CN213988253U
Application number: CN202022601695.2U
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 an organic display module pixel circuit, through setting up first to seventh TFT pipe, light emitting device, electric capacity, reference voltage end, first scanning signal end, second scanning signal end, third scanning signal end, the data end, the luminous control end, first power voltage end and second power voltage end, let seventh TFT pipe work in the saturation region, only the drive current Id size of going to control seventh 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 is not influenced by threshold voltage Vth, just can let OLED display module's luminous luminance more even; in addition, the driving current Id of the seventh TFT tube is not influenced by the internal resistance of the power line on the OLED display module, and the luminous brightness of the OLED display module is more uniform.

Description

Organic display module pixel circuit

Technical Field

The utility model relates to a pixel circuit technical field especially relates to an organic display module assembly pixel 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 module manufactured by the Organic Light Emitting Device (OLED) is called as an OLED display module, the OLED display module is internally provided with a plurality of pixel circuits, the pixel circuits are one of important circuits for ensuring the normal light emitting and displaying of the OLED display module, each pixel circuit is composed of a plurality of thin film transistors (thin film transistors, namely TFT tubes), and due to the individual difference of the thin film transistors, even if the same P-type thin film transistors or N-type thin film transistors are used, the threshold voltages of the same P-type thin film transistors or N-type thin film transistors are different due to the individual difference, so that even if the same data voltage VDATA is used for supplying power to each pixel circuit, different currents can be generated in each pixel circuit, the overall light emitting brightness of the OLED display module is uneven, and the display quality of the OLED display module is influenced finally; in addition, the internal resistance of the power line on the OLED display module also brings about the influence of the voltage difference, and the luminance of the OLED display module is also uneven.

SUMMERY OF THE UTILITY MODEL

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

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

an organic display module pixel circuit, comprising: the display device comprises first to seventh TFT tubes, a light-emitting device, a capacitor, a reference voltage end, a first scanning signal end, a second scanning signal end, a third scanning signal end, a data end, a 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 second scanning signal end and the grid electrode of the third TFT, the drain electrode of the first TFT is respectively connected with the reference voltage end, the drain electrode of the third TFT and the drain electrode of the fifth TFT, 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 sixth TFT;

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

the grid electrode of the fourth TFT is connected with the first scanning signal end, the drain electrode of the fourth TFT is connected with the data end, and the source electrode of the fourth TFT is respectively connected with the other end of the capacitor and the source electrode of the fifth TFT;

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

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

the source electrode of the seventh TFT is connected with 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 sixth TFT, respectively.

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

In one embodiment, the third 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 an organic display module pixel circuit according to an embodiment of the present invention;

fig. 2 is a schematic diagram of a driving timing sequence of a pixel circuit of an organic display module 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, an organic display module pixel circuit 10 includes: first to seventh TFT tubes (i.e., T1, T2, T3, T4, T5, T6, and T7 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 third SCAN signal terminal SCAN3, a data terminal VDATA, a light emission control terminal EM, 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 second SCAN signal terminal SCAN2 and the third TFT tube T3, the drain electrode of the first TFT tube T1 is respectively connected to the reference voltage terminal VINIT, the drain electrode of the third TFT tube T3 and the drain electrode of the fifth TFT tube T5, 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 sixth TFT tube T6;

the gate of the second TFT T2 is connected to the third SCAN signal terminal SCAN3, the drain of the second TFT T2 is connected to the source of the third TFT T3, one end of the capacitor Cst, and the gate of the seventh TFT T7, and the source of the second TFT T2 is connected to the source of the sixth TFT T6 and the drain of the seventh TFT T7;

the gate of the fourth TFT T4 is connected to the first SCAN signal terminal SCAN1, the drain of the fourth TFT T4 is connected to the data terminal VDATA, and the source of the fourth TFT T4 is connected to the other end of the capacitor Cst and the source of the fifth TFT T5 respectively;

the grid electrode of the fifth TFT tube T5 is connected with the light-emitting control end EM;

the grid electrode of the sixth TFT tube T6 is connected with the light-emitting control end EM;

a source electrode of the seventh TFT T7 is connected to the second power voltage terminal ELVSS;

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

In order to better understand the pixel circuit 10 of the organic display module of the present application, please refer to fig. 1 and fig. 2 together, fig. 2 is a schematic diagram of a driving timing sequence of the pixel circuit 10 of the organic display module, wherein fig. 2 shows a total of three stages, i.e., a t1 stage, a t2 stage, and a t3 stage, respectively, and fig. 2 shows a level change condition of the emission control terminal EM, the first SCAN signal terminal SCAN1, the second SCAN signal terminal SCAN2, and the third SCAN signal terminal SCAN3 in the three stages.

Firstly, at a stage T1, the light emission control terminal EM is input at a low level, the first SCAN signal terminal SCAN1 is input at a high level, the second SCAN signal terminal SCAN2 is input at a high level, and the third SCAN signal terminal SCAN3 is input at a low level, at this time, the first TFT transistor T1, the third TFT transistor T3, and the fourth TFT transistor T4 are all turned on, the remaining TFT transistors are all turned off, and the voltage across the light emitting device EL is reset, where Vg is VINIT (Vg, i.e., the voltage at the g point shown in fig. 1, VINIT is the voltage at the reference voltage terminal VINIT shown in fig. 1), Vb is VDATA (Vb, i.e., the voltage at the b point shown in fig. 1, and VDATA, i.e., the voltage at the data terminal VDATA shown in fig. 1);

next, at stage T2, the light emission control terminal EM is input at a low level, the first SCAN signal terminal SCAN1 is input at a high level, the second SCAN signal terminal SCAN2 is input at a low level, the third SCAN signal terminal SCAN3 is input at a high level, at this time, the second TFT tube T2 and the fourth TFT tube T4 are turned on, the rest of the TFT tubes are turned off, Vg is Vd and starts to discharge (Vd is a voltage at point d shown in fig. 1), until Vg is Vs is ELVSS + Vth (Vs is a voltage at point s shown in fig. 1, vss is an ELVSS voltage at the second power supply voltage terminal ELVSS shown in fig. 1, Vth is a threshold voltage of the seventh TFT tube T7 shown in fig. 1), and at this time, the voltage across the capacitor Cst is vdvg-ELVSS + Vth-VDATA;

finally, in the period T3, the period T3 is the light emitting period, the fifth transistor T5 and the sixth transistor T6 are turned on, the rest of the TFT transistors are turned off, Vb is VINIT, the voltage across the capacitor Cst is not changed, Vg is VINIT + ELVSS + Vth-VDATA, Vgs is VINIT + Vth-VDATA (Vgs is the voltage difference between the g point and the s point shown in fig. 1), and the driving current Id of the seventh TFT transistor T7 can be calculated by the following formula:

where μ is the electron mobility of the channel, Cox is the channel capacitance per unit area of the seventh TFT transistor T7, W is the channel width of the seventh TFT transistor T7, and L is the channel length of the seventh TFT transistor T7. It can be seen that Id is independent of Vth, and the circuit can compensate for Vth.

It should be noted that, when the seventh TFT T7 operates in the saturation region, the driving current Id of the seventh TFT T7 is controlled only by the voltage provided by the data terminal VDATA, so as to compensate the threshold voltage Vth of each TFT of the pixel circuit, and the driving current Id is not affected by the threshold voltage Vth, so that the light emitting brightness of the OLED display module is more uniform; in addition, the driving current Id is irrelevant to the first power voltage end ELVDD and the second power voltage end ELVSS, the driving current Id of the seventh TFT tube is not influenced by the internal resistance of the power line on the OLED display module, and the light-emitting brightness of the OLED display module is more uniform. 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 sixth TFT transistor T6, respectively.

As described above, the light emitting device EL is a light emitting diode, but other light emitting devices 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, during the light emitting period, 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 light emitting 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.

Further, referring to fig. 1 again, in one embodiment, the third TFT T3 is an oxide thin film transistor.

It should be noted that, during the light emitting period, the third TFT T3 is in the off state, but there is still a leakage current, which will cause the Vg voltage to be unstable and cause the light emitting luminance to change, so that the third TFT T3 can be replaced by a TFT with smaller leakage current, such as an oxide thin film transistor, to make the leakage current of the third TFT T3 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. An organic display module pixel circuit, comprising: the display device comprises first to seventh TFT tubes, a light-emitting device, a capacitor, a reference voltage end, a first scanning signal end, a second scanning signal end, a third scanning signal end, a data end, a light-emitting control end, a first power supply voltage end and a second power supply voltage end;

2. The pixel 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 sixth TFT, respectively.

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

4. The pixel circuit of claim 1, wherein the third TFT is an oxide thin film transistor.