WO2015192586A1

WO2015192586A1 - Pixel circuit and display device

Info

Publication number: WO2015192586A1
Application number: PCT/CN2014/090613
Authority: WO
Inventors: 杨盛际
Original assignee: 京东方科技集团股份有限公司; 北京京东方光电科技有限公司
Priority date: 2014-06-18
Filing date: 2014-11-07
Publication date: 2015-12-23
Also published as: CN104078003A; CN104078003B

Abstract

A pixel circuit and a display device, the pixel circuit comprising two sub-pixel circuits (P1, P2), each sub-pixel circuit (P1, P2) comprising five switch units (T1, T2, T3, T4, T5, T1', T2', T3', T4', T5'), a drive transistor (DT, DT'), an energy storage unit (C, C'), and an electroluminescent unit (L, L'). The two sub-pixel circuits (P1, P2) share a same data voltage line (Vdata), and share a plurality of scanning signal lines (Em, Scan[1]). In the pixel circuit, an operating current flowing through the electroluminescent units (L, L') is not affected by the threshold voltage of the corresponding drive transistors (DT, DT'), solving the problem of uneven display brightness caused by drifting of the threshold voltage of the drive transistors (DT, DT'). In addition, a compensation circuit is used to complete driving of the two sub-pixel circuits (P1, P2), and the two adjacent sub-pixel circuits (P1, P2) share a plurality of signal lines, reducing the number of signal lines used for pixel circuits in a display device, reducing integrated circuit costs, reducing pixel pitch, and increasing pixel density.

Description

Pixel circuit and display device

Technical field

The present disclosure relates to a pixel circuit and a display device.

Background technique

Organic light-emitting display (OLED) is one of the hotspots in the research field of flat panel displays. Compared with liquid crystal displays, OLEDs have the advantages of low energy consumption, low production cost, self-illumination, wide viewing angle and fast response. At present, OLEDs have begun to replace traditional liquid crystal (LCD) displays in display fields such as mobile phones, PDAs, and digital cameras. Pixel driver circuit design is the core technology content of OLED display, which has important research significance.

Unlike TFT (Thin Film Field Effect Transistor)-LCD, which uses a stable voltage to control brightness, OLEDs are current-driven and require a constant current to control illumination.

Due to process process and device aging, etc., in the original 2T1C driver circuit (including two thin film field effect transistors and one capacitor), the threshold voltage of the driving TFT of each pixel has unevenness, which leads to the flow of each The current of the pixel OLED changes to make the display brightness uneven, thereby affecting the display effect of the entire image.

And in the known technology, a pixel circuit generally corresponds to one pixel, and each pixel circuit includes at least one data voltage line, one working voltage line and a plurality of scanning signal lines, which leads to a complicated manufacturing process and does not Conducive to reducing the pixel pitch.

Summary of the invention

The present disclosure can solve the problem of display brightness unevenness of the display device, and reduce the number of signal lines for the pixel circuit in the display device, reduce the cost of the integrated circuit, and increase the pixel density of the display device.

According to an aspect of the present disclosure, there is provided a pixel circuit including two sub-pixel circuits; each of the sub-pixel circuits includes: a first switching unit, a second switching unit, a third switching unit, a fourth switching unit, and a fifth switching unit a driving unit, an energy storage unit, and an electroluminescent unit; and, the first end of the first switching unit is connected to the working voltage line, and the second end of the first switching unit is connected to the input end of the driving unit for the first switching unit The operating voltage is supplied to the driving unit under the control of the scanning signal line connected to the control terminal; the second end of the first switching unit is further connected to the first end of the energy storage unit, The working voltage line is charged to the first end of the energy storage unit under the control of the scanning signal line connected to the control terminal; the first end of the second switching unit is connected to the second end of the energy storage unit, and the second switch The second end of the unit is grounded for zeroing the voltage of the second end of the energy storage unit under the control of the scanning signal line connected to the control end of the second switching unit; the first end of the third switching unit is connected Between the output end of the driving unit and the electroluminescent unit, the second end of the third switching unit is grounded for outputting the output of the driving unit under the control of the scanning signal line connected to the control end of the third switching unit Grounding; the first end of the fourth switching unit is connected to the data voltage line, and the second end of the fourth switching unit is connected to the control end of the driving unit for scanning signal lines connected at the control end of the fourth switching unit Controlling the control end of the driving unit to the data voltage line; the first end of the fifth switching unit is connected to the control end of the driving unit, and the second end is connected to the second end of the energy storage unit for the fifth switching unit Control terminal The voltage of the control terminal of the driving unit is set to the voltage of the second end of the energy storage unit under the control of the input scanning signal line; and in the two sub-pixel circuits, the first end of the fourth switching unit is connected to the same data voltage line, first The control ends of the switch unit are connected to the first scan signal line, the control ends of the second switch unit and the third switch unit are connected to the second scan signal line, and the control ends of the fifth switch unit are connected to the third scan signal line; The control terminal of the fourth switching unit of the sub-pixel circuit is connected to the second scanning signal line, and the control terminal of the fourth switching unit of the second sub-pixel circuit is connected to the fourth scanning signal line.

In some embodiments, the fourth scan signal line and the third scan signal line are the same scan signal line, and the fourth switch unit of the second sub-pixel circuit is different from the channel type of the fifth switch unit.

In some embodiments, the fourth scan signal line and the third scan signal line are different scan signal lines, and the channel types of the respective switch units and the drive unit are the same.

In some embodiments, each of the switching units and each of the driving units are thin film field effect transistors, and the control terminals of the respective switching units are gates of the thin film field effect transistors, and the first ends of the respective switching units are the sources of the thin film field effect transistors. The second end of each switching unit is a drain of a thin film field effect transistor, and the control end of each driving unit is a gate of a thin film field effect transistor, and the input end of each driving unit is a source of a thin film field effect transistor, and each driving unit is The output is the drain of the thin film field effect transistor.

In some embodiments, the energy storage unit is a capacitor.

In some embodiments, the electroluminescent unit is an organic light emitting diode.

The present disclosure also provides a display device comprising the pixel circuit of any of the above.

In some embodiments, the two sub-pixel circuits of the pixel circuit are respectively located in two adjacent images. Suin.

In some embodiments, the two adjacent pixels are respectively located on opposite sides of the data voltage line.

In some embodiments, the two adjacent pixels are on the same side of the data voltage line.

In the pixel circuit provided by the present disclosure, the operating current flowing through the electroluminescent unit can be unaffected by the threshold voltage of the corresponding driving transistor, and the problem of uneven display brightness due to the threshold voltage drift of the driving transistor is completely solved. At the same time, in the present disclosure, a compensation circuit is used to complete the driving of two pixels, and two adjacent pixels share a plurality of signal lines, which can reduce the number of signal lines for the pixel circuit in the display device, reduce the cost of the integrated circuit, and reduce Pixel spacing to increase pixel density.

DRAWINGS

1 is a schematic structural diagram of a pixel circuit according to Embodiment 1 of the present disclosure;

2 is a timing diagram of key signals in a pixel circuit according to Embodiment 1 of the present disclosure;

3(a)-3(d) are schematic diagrams showing current flow directions and voltage values of pixel circuits in different timings according to Embodiment 1 of the present disclosure;

4 is a schematic structural diagram of a pixel circuit according to Embodiment 2 of the present disclosure;

5 is a timing diagram of key signals in a pixel circuit according to Embodiment 2 of the present disclosure;

6 is a schematic diagram of a positional relationship between a pixel circuit and a pixel in a display device according to an embodiment of the present disclosure;

FIG. 7 is a schematic diagram of another positional relationship between a pixel circuit and a pixel in a display device according to an embodiment of the present disclosure.

detailed description

Exemplary embodiments of the present disclosure are further described below in conjunction with the drawings and embodiments. The following embodiments are only used to more clearly illustrate the technical solutions of the present disclosure, and are not intended to limit the scope of the disclosure.

Embodiment 1

Embodiment 1 of the present disclosure provides a pixel circuit, as shown in FIG. 1 or FIGS. 3(a) to 3(d), including: two sub-pixel circuits P1 and P2, where each sub-pixel circuit corresponds to one pixel. Each pixel sub-circuit, for example P1, comprises: five switching units T1, T2, T3, T4, T5, a driving unit DT, an energy storage unit C, and an electroluminescent unit L (for ease of distinction, in Figure 1 or image 3 (a) - In Fig. 3(d), the five switching units in P2 are denoted as T1', T2', T3', T4', T5', the drive unit is denoted as DT', and the energy storage unit is C', The electroluminescent unit is L', the same below).

The two sub-pixel circuits are identical in that they are described in conjunction with P1:

The control end of T1 is connected to the first scan signal line Em, the first end of T1 is connected to the working voltage line V _dd , and the second end of T1 is connected to the input end of DT for scanning accessed at the control end of T1 The operating voltage is supplied to the driving unit DT under the control of the signal line, and the second end of the T1 is further connected to the first end a1 of the energy storage unit C for working under the control of the scanning signal line connected to the control end of the T1. The voltage line V _dd charges the first end a1 of the energy storage unit C; the control end of T2, T3 is connected to the second scan signal line Scan[1]; the first end of T2 is connected to the second end b1 end of C (for C', the first end is the a2 end shown in the figure, the second end is the b2 end shown in the figure), the second end of T2 is grounded, and the scanning signal line is connected at the control end of T2 Under the control, the voltage of the second end of the energy storage unit C is set to zero; the first end of T3 is connected to the output end of the DT, and the second end of the T3 is grounded, and the scanning signal line is connected to the control end of the T3. under the control of the driving unit DT, the output end; a first terminal T4 is connected to the data line voltage V _data, the second terminal T4 is connected to the control terminal D1 terminal DT (for DT ', which D2 as shown in FIG end system), under control of control for the access terminal T4 of the scanning signal line connected to the control terminal D1 to the data driving unit voltage line V _data; a control terminal T5 is connected to the The three scanning signal line Scan[2], the first end is connected to the control terminal D1 of the DT (for the DT', the control end is the D2 end shown in the figure), and the second end is connected to the b1 end of the C, for The voltage of the control terminal D1 of the driving unit DT is set to the voltage of the second terminal b1 of the energy storage unit C under the control of the scanning signal line connected to the control terminal of T5; the input end of the DT is also connected with the first end a1 of C The terminals are connected and the output is also connected to L.

The difference between the two sub-pixel circuits is:

The control terminal of T4 in P1 is connected to Scan[1], and the control terminal of T4' in P2 is connected to Scan[2]; and the channel type of T4 of P1 is different from T5, and the channel type of T4' of P2 is T5' different.

It can be understood that, except for the channel types of T4 and T5, T4' and T5' which are particularly emphasized above, for other switching units, the control terminals are connected to a plurality of switching units of the same scanning signal line (for example, connected to Em) Two switching units T1 and T1' are connected to two switching units T2, T3, T2', T3' and T4 of Scan[1], and two switching units T5 and T5' connected to Scan[2] shall be The switches of the same channel type, that is, the high level conduction or the low level conduction, ensure that the two switching units connected to the same scanning signal line are turned on or off in the same state.

In the pixel circuit provided by the present disclosure, the operating current flowing through the electroluminescent unit can be unaffected by the threshold voltage of the corresponding driving transistor, completely solving the threshold voltage drift of the driving transistor. The shift causes a problem of uneven brightness. At the same time, in the present disclosure, a compensation circuit is used to complete the driving of two pixels, the number of compensated TFT devices is reduced, and one data voltage line is reduced, thereby reducing the number of signal lines, thereby greatly reducing the pixel pitch size. And reduce IC costs, resulting in higher pixel density.

In some embodiments, each of the switching units and each of the driving units are thin film field effect transistors (TFTs), and the control terminals of the respective switching units are gates, and the first ends of the respective switching units are the sources of the thin film field effect transistors, and the respective switching units are The second end is the drain of the field effect transistor, the input end of each driving unit is the source of the field effect transistor, the control end of each driving unit is the gate of the field effect transistor, and the output end of each driving unit is the field effect transistor Drain. Of course, the switching unit and the driving unit can also be other suitable devices or device combinations.

It is not difficult to understand that the transistors corresponding to the driving unit and the switching unit herein may be transistors in which the source and the drain are interchangeable, or the first end of each of the switching units and the driving unit may be the drain of the transistor according to the type of conduction. The second end is the source of the transistor, and those skilled in the art can obtain the reverse connection of the source and the drain of each transistor in the pixel circuit provided by the present disclosure without any creative labor, and can obtain the information provided by the present disclosure. The circuit structures of the same or similar technical effects that can be achieved by the technical solutions should also fall within the protection scope of the present disclosure.

In some embodiments, the energy storage unit C is a capacitor. Of course, in practical applications, other components with energy storage functions can be used according to design requirements.

In some embodiments, the electroluminescent unit L can be an organic light emitting diode (OLED). Of course, in practical applications, other components having electroluminescence function can also be used according to design requirements.

The working principle of the pixel circuit provided by the exemplary embodiment of the present disclosure is described in detail below with reference to FIG. 2 and FIG. 3(a) to FIG. 3(d). As shown in FIG. 2, the pixel circuit provided by the present disclosure is input to each working. The timing chart of the scan signal in the scan signal line can be divided into four stages, which are respectively shown in FIG. 2 as the reset stage W1, the first discharge stage W2, the second discharge stage W3, and the illumination stage W4, in each stage, The current flow direction and voltage values of the pixel circuit are as shown in Fig. 3 (a), Fig. 3 (b), Fig. 3 (c), and Fig. 3 (d), respectively. For convenience of explanation, T5 and T5' are N-channel TFTs, and other TFTs are P-channel TFTs.

In the reset phase W1, as shown in FIG. 2, each of the scanning signal lines is at a low level, and the data voltage of the data voltage line is V _data = V ₁ , and V ₁ is a voltage corresponding to the organic light emitting diode L. At this time, only T5 Disconnected from T5', the other TFTs are turned on, and the current flows as shown by La in Fig. 3(a). At this stage, the a1 end of the capacitor C and the a2 end of the capacitor C' are connected to the working voltage line V _dd , the potential Both are V _dd , the working voltage line V _dd continues to charge C and C'. After the charging is completed, the b1 end of the capacitor C and the b2 end of the C' are both grounded, the potential is 0, the D1 end of the DT and the D2 end of the DT' They are all connected to V _data and the potential is V1.

In the first discharge phase W2, as shown in FIG. 2, in the scanning signal line, Em is at a high level, and Scan[1] and Scan[2] are at a low level, at which time T1, T1', T5, T5' are off. The other TFTs are turned on, and the current flows as shown by Lb1 and Lb2 in Fig. 3(b), C is discharged along Lb1, and C' is discharged along Lb2. After the end of discharge, the potential at the a1 terminal is lowered to V ₁ + V _{th1 .} The potential at the a2 terminal falls to V ₁ +V _th2 , where V _th1 and V _th2 are the threshold voltages of DT and DT', respectively.

In the second discharge phase W3, as shown in FIG. 2, in the scan signal line, only Scan[1] is high level, other scan signal lines are low level, data voltage V _data = V ₂ , and V ₂ is organic light emission. The voltage corresponding to the diode L', at this time, only T3', T4' and DT' are turned on, the other TFTs are turned off, the D2 terminal is connected to V _data , the potential is V2, and C' is along the Lc in Fig. 3(c) Discharge, after the end of discharge, the potential at the a1 end remains unchanged, and the potential at the a2 terminal drops to V ₂ + V _th2 .

In the light-emitting phase W4, as shown in FIG. 2, in the scan signal line, Em is at a high level, and other scan signal lines are at a low level, at which time T1, T1', T5, T5', DT, DT' are turned on, The other TFTs are turned off. The a1 and a2 terminals are connected to V _dd , and the b1 and b2 terminals are floating. At this time, an isobaric jump occurs. The D1 point potential is V _dd -V ₁ -V _th1 , and the D2 point potential is V _{dd .} -V ₂ -V _th2 , V _dd supplies current to L and L' along Ld1 and Ld2 in Fig. 3(d), causing L and L' to emit light.

According to the saturation current formula, the current flowing through L is I _L =K(V _GS -V _th1 ) ² =[V _dd -([V _dd -V ₁ -V _th1 )–V _th1 ] ² =K*V ₁ ² .

Similarly, I _L' = K * V ₂ ² .

It can be seen from the above equation that the operating current flowing through the two electroluminescent units at this time can be unaffected by the threshold voltage of the driving transistor, and is only related to the data voltage V _data at this time. The problem that the threshold voltage (V _th ) of the driving TFT drifts due to the process process and long-time operation is completely solved, the influence of the current flowing through the electroluminescent unit is eliminated, and the normal operation of the electroluminescent unit is ensured. In the embodiment of the present disclosure, two pixels share the same data voltage line, the working voltage line, and only three scanning signal lines, which greatly reduces the number of corresponding signal lines, reduces the cost of the integrated circuit, and reduces the pixel pitch. Increase pixel density.

Embodiment 2

The pixel circuit provided in the second embodiment of the present disclosure is different from the pixel circuit provided in the first embodiment in that the control terminal of T4' in P2 is connected to the fourth scan signal Scan[3] (see FIG. 4), where Scan[3] Different from Scan[2] above, the channel type of T4' of P2 and the channel type of T5 and T5' can be The same, can also be different. The technical solution provided by the present disclosure can be realized by making the conduction state of T4' opposite to the conduction state of T5 and T5' on the basis of the embodiment of the first embodiment, and the principle thereof will not be described in detail herein.

In some embodiments, the channel types of the various switching units and DTs are the same. This can ensure that the process of each switch unit and DT is consistent, reducing the difficulty of production.

In some embodiments, as shown in FIG. 4, each of the switching units and DT are P-channel type TFTs. At this time, the timing chart of each signal input by the pixel circuit during operation can be as shown in FIG. 5. Compared with the timing diagram of the first embodiment shown in FIG. 2, since T5 and T5' become P-type transistors, the signals of Scan[2] are reversed, and at the same time, in order to make the conduction state of T4' and T5 and T5' The conduction state is reversed, so that the fourth scan signal Scan[3] which is inverted from the signal of Scan[2] in this embodiment is added, and the working principle is similar to that of the first embodiment, and details are not described herein again.

Based on the same concept, the present disclosure also provides a display device including the pixel circuit shown in any of the above.

In some embodiments, in the display device, two sub-pixel circuits of the pixel circuit are respectively located in two adjacent pixels. This enables the distribution of components on the corresponding substrate to be more uniform.

In some embodiments, the two adjacent pixels are located on the same side of their data voltage lines, and FIG. 6 shows that two adjacent pixels corresponding to one pixel circuit PU are on the side of their corresponding data voltage lines V _data . Case; or, the two adjacent pixels are respectively located on both sides of the data voltage line thereof, and FIG. 7 shows two adjacent pixels corresponding to one of the pixel circuits PU on both sides of the corresponding data voltage line V _data Case.

The display device can be any product or component having display function such as electronic paper, mobile phone, tablet computer, television, display, notebook computer, digital photo frame, navigator, and the like.

The above description is only a preferred embodiment of the present disclosure, and it should be noted that those skilled in the art can also make several improvements and retouchings without departing from the principles of the disclosed technology. It should also be considered as the scope of protection of the present disclosure.

The present application claims the priority of the Chinese Patent Application No. 201410274108.X filed on Jun. 18, 2014, the entire disclosure of which is hereby incorporated by reference.

Claims

A pixel circuit comprising two sub-pixel circuits;

Each of the sub-pixel circuits includes: a first switching unit, a second switching unit, a third switching unit, a fourth switching unit, a fifth switching unit, a driving unit, an energy storage unit, and an electroluminescence unit;

The first end of the first switching unit is connected to the working voltage line, and the second end of the first switching unit is connected to the input end of the driving unit for controlling the scanning signal line connected to the control end of the first switching unit The driving unit provides an operating voltage; the second end of the first switching unit is further connected to the first end of the energy storage unit, and is configured to make the working voltage line under the control of the scanning signal line connected to the control end of the first switching unit Charging the first end of the energy storage unit;

a first end of the second switching unit is connected to the second end of the energy storage unit, and a second end of the second switching unit is grounded for controlling under the control of the scanning signal line connected to the control end of the second switching unit The voltage at the second end of the energy storage unit is set to zero;

The first end of the third switching unit is connected between the output end of the driving unit and the electroluminescent unit, and the second end of the third switching unit is grounded for scanning signal lines connected at the control end of the third switching unit Grounding the output of the drive unit under control;

The first end of the fourth switching unit is connected to the data voltage line, and the second end of the fourth switching unit is connected to the control end of the driving unit for controlling under the scanning signal line connected to the control end of the fourth switching unit Connecting the control terminal of the drive unit to the data voltage line;

a first end of the fifth switching unit is connected to the control end of the driving unit, and a second end is connected to the second end of the energy storage unit for controlling under the control of the scanning signal line connected to the control end of the fifth switching unit The voltage of the control terminal of the driving unit is set to the voltage of the second end of the energy storage unit;

And in the two sub-pixel circuits, the first end of the fourth switching unit is connected to the same data voltage line, the control ends of the first switching unit are connected to the first scanning signal line, and the control ends of the second switching unit and the third switching unit are both Connecting the second scan signal line, the control end of the fifth switch unit is connected to the third scan signal line; the control end of the fourth switch unit of the first sub-pixel circuit is connected to the second scan signal line, and the second sub-pixel circuit The control terminal of the four switching unit is connected to the fourth scanning signal line.
The pixel circuit according to claim 1, wherein the fourth scan signal line and the third scan signal line are the same scan signal line, and the fourth switch unit and the fifth switch unit of the second sub-pixel circuit The channel type is different.
The pixel circuit according to claim 1, wherein said fourth scanning signal line and said third scanning signal line are different scanning signal lines.
The pixel circuit according to claim 3, wherein the channel types of the respective switching units and the driving units are the same.
The pixel circuit according to any one of claims 1 to 4, wherein each of the switching units and each of the driving units is a thin film field effect transistor, and the control terminals of the respective switching units are gates of the thin film field effect transistors, and the respective switching units are The first end is the source of the thin film field effect transistor, the second end of each switching unit is the drain of the thin film field effect transistor, and the control end of each driving unit is the gate of the thin film field effect transistor, and the input end of each driving unit is The source of the thin film field effect transistor, the output of each driving unit is the drain of the thin film field effect transistor.
The pixel circuit according to any one of claims 1 to 5, wherein the energy storage unit is a capacitor.
The pixel circuit according to any one of claims 1 to 6, wherein the electroluminescent unit is an organic light emitting diode.
A display device comprising the pixel circuit according to any one of claims 1-7.
The display device of claim 8, wherein the two sub-pixel circuits of the pixel circuit are respectively located in two adjacent pixels.
The display device of claim 9, wherein the two adjacent pixels are respectively located on both sides of the data voltage line.
The display device of claim 9, wherein the two adjacent pixels are located on the same side of the data voltage line.