CN211264912U

CN211264912U - Pixel circuit and display device

Info

Publication number: CN211264912U
Application number: CN202020193738.5U
Authority: CN
Inventors: 郑士嵩
Original assignee: Chongqing Kangjia Photoelectric Technology Research Institute Co Ltd
Current assignee: Chongqing Kangjia Photoelectric Technology Research Institute Co Ltd
Priority date: 2020-02-21
Filing date: 2020-02-21
Publication date: 2020-08-14
Anticipated expiration: 2030-02-21

Abstract

The utility model discloses a pixel circuit and display device, wherein, pixel circuit includes: the light-emitting unit is connected with the fixed current source; the switch circuit is connected with the first control end, the second control end, the light-emitting unit and the fixed voltage source, and is used for controlling the connection or disconnection of a loop where the light-emitting unit is located under the control of the first control end and the second control end; and the initialization circuit is connected with the third control end and the light-emitting unit, forms a first node and a second node with the light-emitting unit, is connected with the fixed current source, is connected with the switch circuit, and is used for initializing the light-emitting unit under the control of the third control end. The pixel circuit can improve power consumption, realize energy-saving effect and realize accurate control on the gray scale brightness of the light-emitting unit.

Description

Pixel circuit and display device

Technical Field

The utility model relates to a show technical field, especially relate to a pixel circuit and display device.

Background

A TFT (thin film Transistor) display has the advantages of fine and vivid images, light weight, low power consumption and good environmental protection performance, and is widely applied to devices such as televisions, notebook computers, mobile phones and monitors; EL (electroluminescent) devices are also widely used in the manufacture of display products due to their excellent optical properties, power consumption performance, and product form plasticity.

In the prior art, as shown in fig. 1(a), when a TFT device is used to drive an EL device to emit light, two power supply electrodes (including a VDD high voltage electrode and a VSS low voltage electrode) are used to supply the current required for light emission to the EL device, and a pixel circuit adopts a 2T1C architecture, and outputs a constant current I by adjusting VGS (gate-source voltage) and operating in a saturation region (shown in fig. 1 (b)) of an IDS-VDS (drain-source current-drain-source voltage) characteristic diagram_TFT. Referring to fig. 1(a), in this technique, the minimum requirement of the voltage across the power supply electrode is V_TFT+V_ELTherefore, the fixed power consumption under the framework is as follows: p = I_TFT×(V_TFT+V_EL)。

In other words, when the DATA signal terminal DATA controls to output a constant voltage Dm (as shown in fig. 1 (c)), the pixel circuit in fig. 1(a) outputs a constant current, but since the driving transistor TFT plays a role of current limiting, the driving transistor TFT also divides the voltage when the circuit of the EL device is connected, resulting in power consumption. EL devices have not been able to exhibit their most advantageous characteristics in TFT displays.

Disclosure of Invention

The utility model discloses aim at solving one of the technical problem among the prior art to a certain extent at least. Therefore, an object of the present invention is to provide a pixel circuit to improve power consumption, achieve energy saving effect, and achieve precise control of the gray scale brightness of the light emitting unit.

Another object of the present invention is to provide a display device.

To achieve the above object, the present invention provides a pixel circuit, which includes: the light-emitting unit is connected with a fixed current source; the switch circuit is connected with the first control end, the second control end, the light-emitting unit and the fixed voltage source, and is used for controlling the connection or disconnection of a loop where the light-emitting unit is located under the control of the first control end and the second control end; the initialization circuit is connected with a third control end and the light-emitting unit, a first node and a second node are formed between the initialization circuit and the light-emitting unit, the first node is connected with the fixed current source, the second node is connected with the switch circuit, and the initialization circuit is used for initializing the light-emitting unit under the control of the third control end.

The utility model discloses a pixel circuit, under the control of first control end and second control end through switch circuit, the connection or the disconnection of control luminescence unit place return circuit to and through the initialization circuit under the control of third control end, initialize luminescence unit, can improve the consumption, realize energy-conserving effect, and can realize the accurate control to luminescence unit gray scale luminance.

Specifically, the switching circuit includes: a first transistor, wherein a first pole of the first transistor is connected to the second node, and a gate of the first transistor is connected to the first control terminal; and a first pole of the second transistor is connected with a second pole of the first transistor, a second pole of the second transistor is connected with the fixed voltage source, and a grid electrode of the second transistor is connected with the second control end.

Specifically, the initialization circuit includes: a third transistor, a first pole of the third transistor being connected to the first node, a second pole of the third transistor being connected to the second node, and a gate of the third transistor being connected to the third control terminal.

As an example, the fixed voltage source is a low voltage source, and the first transistor, the second transistor and the third transistor are all N-type TFT transistors, wherein a second pole of the second transistor is connected to the low voltage source.

As an example, the fixed voltage source is a high voltage source, and the first transistor, the second transistor and the third transistor are P-type TFT transistors, wherein a second pole of the second transistor is connected to the high voltage source.

Specifically, the light emitting unit adopts a light emitting diode, and the light emitting diode is a micro light emitting diode.

In order to achieve the above object, the present invention further provides a display device, which includes: the display device includes a display area and a pixel array provided in the display area, wherein the pixel array includes a plurality of the above-described pixel circuits arranged in a matrix state.

The utility model discloses a display device, through foretell pixel circuit, can realize energy-conservingly, and can realize the accurate control to luminescent device grey scale luminance.

Optionally, the display device further comprises: and a plurality of current source wirings which are provided in the display region, are distributed in a column shape, and share one current source wiring for pixel circuits in the same column.

Optionally, the display device further comprises: voltage source wirings provided in the display area and having a mesh shape.

Furthermore, a plurality of pins are arranged corresponding to the voltage source wiring, and the pins share a fixed voltage.

The utility model discloses a pixel circuit and display device adopts common electrode (common negative pole/common positive pole) framework, and the EL device of collocation adds the TFT initiative device, can make whole circuit's step-voltage low to can improve the consumption, realize energy-conserving effect, and can realize digital switch current path, thereby can realize the grey scale luminance of accurate control EL device, thereby make the EL device can be applied to in the TFT display well.

Drawings

FIG. 1(a) is a schematic diagram of a pixel circuit in the prior art;

FIG. 1(b) is a schematic diagram of the control principle of the pixel circuit in FIG. 1 (a);

FIG. 1(c) is a schematic diagram of the control timing of the pixel circuit in FIG. 1 (a);

fig. 2 is a block diagram of a pixel circuit according to embodiment 1 of the present invention;

fig. 3 is a schematic structural diagram of a pixel circuit according to embodiment 2 of the present invention;

fig. 4 is a schematic structural diagram of a pixel circuit according to embodiment 3 of the present invention;

FIG. 5 is a schematic diagram of the control timing for one example of the pixel circuit of FIG. 3;

FIG. 6 is a schematic diagram of control timing for another example of the pixel circuit of FIG. 3;

FIG. 7 is a schematic diagram of the control timing for one example of the pixel circuit of FIG. 4;

FIG. 8 is a schematic diagram of control timing for another example of the pixel circuit of FIG. 4;

fig. 9 is a schematic structural view of a display device according to embodiment 4 of the present invention;

fig. 10 is a schematic structural view of a display device according to embodiment 5 of the present invention;

fig. 11 is a schematic structural view of a display device according to embodiment 6 of the present invention.

Detailed Description

Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the drawings are exemplary and intended to be used for explaining the present invention, and should not be construed as limiting the present invention.

The pixel circuit and the display device according to the embodiments of the present invention are described below with reference to the drawings.

Example 1

Fig. 2 is a block diagram of a pixel circuit according to embodiment 1 of the present invention.

As shown in fig. 2, the pixel circuit includes: a light emitting unit 10, a switching circuit 20, and an initialization circuit 30.

Referring to fig. 2, the light emitting unit 10 IS connected to a fixed current source IS; the switch circuit 20 is connected with the first control end SN, the second control end SEL, the light-emitting unit 10 and the fixed voltage source VS, and the switch circuit 20 is used for controlling the connection or disconnection of a loop where the light-emitting unit 10 is located under the control of the first control end SN and the second control end SEL; the initialization circuit 30 IS connected to the third control terminal RET and the light emitting unit 10, and forms a first node a and a second node b with the light emitting unit 10, the first node a IS connected to the fixed current source IS, the second node b IS connected to the switch circuit 20, and the initialization circuit 30 IS configured to initialize the light emitting unit 10 under the control of the third control terminal RET.

Alternatively, the first control terminal SN and the third control terminal RET may both provide corresponding control signals by using drivers in the row direction, the second control terminal SEL may provide corresponding control signals by using drivers in the column direction, and the fixed current source IS may also provide corresponding fixed current by using drivers in the column direction. Of course, the driver axial direction may not be limited, and the relative axial configuration is merely one example.

Specifically, the control signal provided by the first control terminal SN can be used for scanning in the row direction, for example, SN [ n ] can be used as the selection control signal for the nth row. The control signal provided by the third control terminal RET can initialize the light emitting unit 10 before or after the operation of the first control terminal SN to avoid residual charges and to make the light emitting unit 10 leak light to deteriorate the contrast. The control signal provided by the second control terminal SEL can operate the PWM function, and the accurate gray scale brightness value is determined by the switching time of the selected pixel point by matching with the control signal provided by the first control terminal SN. The fixed current source IS for ensuring that the current flowing through the light emitting unit 10 IS a fixed value when the light emitting unit IS turned on.

Therefore, the utility model discloses pixel circuit can improve the consumption, realizes energy-conserving effect, and can realize the accurate control to the luminescence unit grey scale luminance.

In some embodiments of the present invention, as shown in fig. 3 and 4, the switch circuit 20 includes: a first transistor T1 and a second transistor T2.

Referring to fig. 3 and 4, the first pole of the first transistor T1 is connected to the second node b, and the gate of the first transistor T1 is connected to the first control terminal SN; the first pole of the second transistor T2 is connected to the second pole of the first transistor T1, the second pole of the second transistor T2 is connected to the fixed voltage source VS, and the gate of the second transistor T2 is connected to the second control terminal SEL.

Further, referring to fig. 3 and 4, the initialization circuit 30 includes: a third transistor T3. A first pole of the third transistor T3 is connected to the first node a, a second pole of the third transistor T3 is connected to the second node b, and a gate of the third transistor T3 is connected to the third control terminal RET.

Alternatively, referring to fig. 3 and 4, the Light Emitting unit 20 employs a Light Emitting Diode EL, and the Light Emitting Diode EL may be a micro Light Emitting Diode, such as an OLED (Organic Light-Emitting Diode), an LED (Light-Emitting Diode), and the like. Compared with the conventional Display (such as CRT (Cathode Ray Tube), LCD (Liquid Crystal Display), etc.), the Display device manufactured by using OLED, LED, etc. has better optical characteristics, lower power consumption, and better product form plasticity.

In this embodiment, the devices and waveform settings, operation purposes and implementations of fig. 3 and 4 are shown in table 1 below:

TABLE 1

Example 2

Fig. 3 is a block diagram of a pixel circuit according to embodiment 2 of the present invention.

As shown in fig. 3, the pixel circuit includes: the light emitting diode comprises a first transistor T1, a second transistor T2, a third transistor T3 and a light emitting diode, and the first transistor T1, the second transistor T2 and the third transistor T3 are all N-type TFT tubes.

Referring to fig. 3, a first pole of the first transistor T1 is connected to the second node b, and a gate of the first transistor T1 is connected to the first control terminal SN; a first pole of the second transistor T2 is connected to a second pole of the first transistor T1, a second pole of the second transistor T2 is connected to the low voltage source VSS, and a gate of the second transistor T2 is connected to the second control terminal SEL; a first pole of the third transistor T3 is connected to the first node a, a second pole of the third transistor T3 is connected to the second node b, and a gate of the third transistor T3 is connected to the third control terminal RET; the anode of the light emitting diode EL IS connected to the first node a, the first node a IS connected to the fixed current source IS, and the cathode of the light emitting diode EL IS connected to the second node b. Thus, under the control of the first control terminal SN and the second control terminal SEL, the connection or disconnection of the loop in which the light emitting diode EL is located is controlled by controlling the on or off of the first transistor T1 and the second transistor T2; the light emitting diode EL is initialized by controlling the third transistor T3 to be turned on or off under the control of the third control terminal RET.

In this embodiment, the pixel circuits of each column are connected to a fixed current source IS, and all the light emitting diodes EL can share the low voltage provided by the low voltage source VSS. The control flow of the pixel circuit is as follows:

the first stage is as follows: luminescence

As shown in fig. 3 and 5, at time T1, the first transistor T1 is turned on under the control of the first control terminal SN to implement row selection; at this time, the second transistor T2 is turned on under the control of the second control terminal SEL, and the loop of the light emitting diode EL is connected, so that the current I is enabled_TFTFlows through the light emitting diode EL, the light emitting diode EL emits light, and the current I_TFTThe gray level of light emission can be determined.

At this stage, the first transistor T1 and the second transistor T2 only have pure switch power supply, no voltage cross voltage is consumed, and the overall cross voltage is V_ELCompared with the voltage V of the pixel circuit shown in FIG. 1_TFT+V_ELLow, thereby achieving the purpose of energy saving. Meanwhile, the second control terminal SEL may enable the on-time of the second transistor T2 to be proportional to the light emitting time of the light emitting diode EL by providing a PWM (Pulse Width Modulation) signal to the second transistor T2. Further, by controlling the light emission time period, the luminance of the light emitting diode EL can be adjusted.

And a second stage: initialization

The conduction of the third transistor T3 can make the anode and cathode of the light emitting diode EL directly short-circuit, thereby eliminating the charges left by the previous timing sequence and preventing the write operation of the next timing sequence from being affected by the previous timing sequence. Specifically, as shown in fig. 4 and 6, at time T2, the third transistor T3 IS turned on under the control of the third control terminal RET, the first transistor T1 IS turned off under the control of the first control terminal SN, the current provided by the fixed current source IS flows through the cathode of the light emitting diode EL through the third transistor T3, the cathode of the light emitting diode EL IS at a high level, and since the anode of the light emitting diode EL IS also at a high level, the voltage difference between the two ends of the light emitting diode EL IS zero, so that the initialization of the light emitting diode EL IS completed to avoid the influence on the next control timing.

Example 3

Fig. 4 is a block diagram of a pixel circuit according to embodiment 3 of the present invention.

As shown in fig. 4, the pixel circuit includes: the light emitting diode comprises a first transistor T1, a second transistor T2, a third transistor T3 and a light emitting diode, and the first transistor T1, the second transistor T2 and the third transistor T3 are all P-type TFT transistors.

Referring to fig. 3, a first pole of the first transistor T1 is connected to the second node b, and a gate of the first transistor T1 is connected to the first control terminal SN; a first pole of the second transistor T2 is connected to a second pole of the first transistor T1, a second pole of the second transistor T2 is connected to the high voltage source VDD, and a gate of the second transistor T2 is connected to the second control terminal SEL; a first pole of the third transistor T3 is connected to the first node a, a second pole of the third transistor T3 is connected to the second node b, and a gate of the third transistor T3 is connected to the third control terminal RET; the cathode of the light emitting diode EL IS connected to the first node a, the first node a IS connected to the fixed current source IS, and the anode of the light emitting diode EL IS connected to the second node b. Thus, under the control of the first control terminal SN and the second control terminal SEL, the connection or disconnection of the loop in which the light emitting diode EL is located is controlled by controlling the on or off of the first transistor T1 and the second transistor T2; the light emitting diode EL is initialized by controlling the third transistor T3 to be turned on or off under the control of the third control terminal RET.

In this embodiment, the pixel circuits of each column are connected to a fixed current source IS, and all the light emitting diodes EL can share the high voltage provided by the high voltage source VDD. The control flow of the pixel circuit is as follows:

the first stage is as follows: luminescence

As shown in fig. 4 and 7, time t3The first transistor T1 is turned on under the control of the first control terminal SN to implement row selection; at this time, the second transistor T2 is turned on under the control of the second control terminal SEL, and the loop of the light emitting diode EL is connected, so that the current I is enabled_TFTFlows through the light emitting diode EL, the light emitting diode EL emits light, and the current I_TFTThe gray level of light emission can be determined.

And a second stage: initialization

The conduction of the third transistor T3 can make the anode and cathode of the light emitting diode EL directly short-circuit, thereby eliminating the charges left by the previous timing sequence and preventing the write operation of the next timing sequence from being affected by the previous timing sequence. Specifically, as shown in fig. 4 and 8, at time T2, the third transistor T3 IS turned on under the control of the third control terminal RET, the first transistor T1 IS turned off under the control of the first control terminal SN, the current provided by the fixed current source IS flows through the cathode of the light emitting diode EL through the third transistor T3, the cathode of the light emitting diode EL IS at a high level, and since the anode of the light emitting diode EL IS also at a high level, the voltage difference between the two ends of the light emitting diode EL IS zero, so that the initialization of the light emitting diode EL IS completed to avoid the influence on the next control timing.

To sum up, the utility model discloses pixel circuit adopts common electrode (negative pole/positive pole altogether) framework, and collocation EL device adds the TFT active device, can make the step voltage of whole circuit low to can improve the consumption, realize energy-conserving effect, and can realize digital switch current path, thereby can realize the grey scale luminance of accurate control EL device.

Example 4

Fig. 9 is a schematic structural view of a display device according to embodiment 4 of the present invention.

As shown in fig. 9, the display device includes: a display area 100 and a pixel array provided in the display area, wherein the pixel array includes a plurality of pixel circuits 201 arranged in a matrix state. The pixel circuit 201 is the pixel circuit of the above embodiments. Referring to fig. 9, the pixel array includes M × N pixel circuits 201 arranged in a matrix state, M being the total number of rows of the matrix and N being the total number of columns of the matrix.

Therefore, the display device can save energy and realize accurate control of the gray scale brightness of the light-emitting device through the pixel circuit.

Example 5

Fig. 10 is a schematic structural view of a display device according to embodiment 5 of the present invention.

As shown in fig. 10, the display device includes not only the display area 100 and the pixel array described above, but also: and a plurality of current source wirings 300, wherein the plurality of current source wirings 300 are disposed in the display region 100 and distributed in a column, and the pixel circuits 201 in the same column share one current source wiring 300 for use.

Alternatively, different current source wirings 300 may connect different fixed current sources IS to supply different currents, so that different light emitting luminances of the light emitting cells 10 can be realized.

Example 6

As shown in fig. 11, the display device includes not only the display area 100 and the pixel array described above, but also: voltage source wirings 400 (hatched portions in fig. 11), the voltage source wirings 400 being disposed in the display area 100 and having a grid shape for use.

Alternatively, referring to fig. 11, a plurality of PINs PIN may be disposed corresponding to the voltage source wiring 400, and the plurality of PINs PIN may share a fixed voltage, which may be a low voltage provided by the low voltage source VSS or a high voltage provided by the high voltage source VDD, so as to adapt to different types of TFT transistors.

In an embodiment of the present invention, referring to fig. 9, 10, and 11, the display device may further include a peripheral area 500, and the peripheral area 500 is disposed around the display area 100.

In addition, the TFT backplane substrate of the pixel circuit can be fabricated by using an active device such as LTPS (Low Temperature polysilicon) or Metal Oxide (Metal Oxide) that can be formed on RG (Rigid Glass) or PI (Flexible Polyimide), so that the display device formed by the pixel circuit has a simple structure and high stability.

Although embodiments of the present invention have been shown and described, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made to the above embodiments by those of ordinary skill in the art without departing from the scope of the present invention.

Claims

1. A pixel circuit, comprising:

the light-emitting unit is connected with a fixed current source;

the switch circuit is connected with the first control end, the second control end, the light-emitting unit and the fixed voltage source, and is used for controlling the connection or disconnection of a loop where the light-emitting unit is located under the control of the first control end and the second control end;

the initialization circuit is connected with a third control end and the light-emitting unit, a first node and a second node are formed between the initialization circuit and the light-emitting unit, the first node is connected with the fixed current source, the second node is connected with the switch circuit, and the initialization circuit is used for initializing the light-emitting unit under the control of the third control end.

2. The pixel circuit according to claim 1, wherein the switching circuit comprises:

a first transistor, wherein a first pole of the first transistor is connected to the second node, and a gate of the first transistor is connected to the first control terminal;

and a first pole of the second transistor is connected with a second pole of the first transistor, a second pole of the second transistor is connected with the fixed voltage source, and a grid electrode of the second transistor is connected with the second control end.

3. The pixel circuit according to claim 2, wherein the initialization circuit comprises:

a third transistor, a first pole of the third transistor being connected to the first node, a second pole of the third transistor being connected to the second node, and a gate of the third transistor being connected to the third control terminal.

4. The pixel circuit according to claim 3, wherein the fixed voltage source is a low voltage source, and the first transistor, the second transistor, and the third transistor are all N-type TFT transistors, wherein a second pole of the second transistor is connected to the low voltage source.

5. The pixel circuit according to claim 3, wherein the fixed voltage source is a high voltage source, and the first transistor, the second transistor, and the third transistor are P-type TFT transistors, wherein a second pole of the second transistor is connected to the high voltage source.

6. The pixel circuit according to claim 1, wherein the light emitting unit is a light emitting diode, and the light emitting diode is a micro light emitting diode.

7. A display device, comprising: a display area and a pixel array provided in the display area, wherein the pixel array includes a plurality of pixel circuits according to any one of claims 1 to 6 arranged in a matrix state.

8. The display device according to claim 7, further comprising:

and a plurality of current source wirings which are provided in the display region, are distributed in a column shape, and share one current source wiring for pixel circuits in the same column.

9. The display device according to claim 7, further comprising:

voltage source wirings provided in the display area and having a mesh shape.

10. The display device according to claim 9, wherein a plurality of pins are disposed corresponding to the voltage source wiring, and the plurality of pins share a fixed voltage.