CN114267288A

CN114267288A - Driving circuit

Info

Publication number: CN114267288A
Application number: CN202111633760.2A
Authority: CN
Inventors: 洪嘉泽; 杨文玮; 徐圣淯; 冯玟菲; 蔡正晔; 陈勇志
Original assignee: AU Optronics Corp
Current assignee: AU Optronics Corp
Priority date: 2021-07-29
Filing date: 2021-12-29
Publication date: 2022-04-01
Anticipated expiration: 2041-12-29
Also published as: TWI780844B; TW202306434A; CN114267288B

Abstract

A driving circuit comprises a driving transistor, a first driver, a second driver and a light emitting diode. The driving transistor is used for outputting a driving signal according to the voltage stored in the first node. The first driver is used for storing a data signal to the first node according to the first scanning signal and determining whether to output a driving signal according to the first scanning signal, the second scanning signal and the emission signal. The second driver is used for providing a first compensation voltage to the first node according to the driving signal and the transmitting signal output by the first driver. The light emitting diode includes an anode terminal and a cathode terminal, and the anode terminal is coupled to the first driver or the driving transistor and is configured to receive a driving signal to emit light.

Description

Driving circuit

Technical Field

The present disclosure relates to display devices, and more particularly, to a driving circuit for a micro light emitting diode display.

Background

An Active Micro-LED (AMLED) display has the advantages of high contrast, high color saturation, high brightness, etc., which makes it one of the next generation hot display technologies. When the conventional AMLED display is operated, the temperature of the panel increases, so that the thermal effect of the light emitting diode, that is, the luminous efficiency and the voltage (Vled) thereof become small, and the brightness of the AMLED display is attenuated. Accordingly, there is a need in the art to solve the thermal effect of the light emitting diode and provide an AMLED display with high display quality.

Disclosure of Invention

This summary is intended to provide a simplified summary of the disclosure in order to provide a basic understanding to the reader. This summary is not an extensive overview of the disclosure and is intended to neither identify key/critical elements of the embodiments nor delineate the scope of the embodiments.

One aspect of the present disclosure relates to a driving circuit. The driving circuit comprises a driving transistor, a first driver, a second driver and a light emitting diode. The driving transistor is used for outputting a driving signal according to the voltage stored in the first node. The first driver is used for storing a data signal to the first node according to the first scanning signal and determining whether to output a driving signal according to the first scanning signal, the second scanning signal and the emission signal. The second driver is used for providing a first compensation voltage to the first node according to the driving signal and the transmitting signal output by the first driver. The light emitting diode includes an anode terminal and a cathode terminal, and the anode terminal is coupled to the first driver or the driving transistor and is configured to receive a driving signal to emit light.

Therefore, according to the technical content of the present application, the driving circuit according to the embodiment of the present application can prevent the brightness of the AMLED from being attenuated with the increase of the temperature during the operation. In addition, the driving circuit can improve the problem of the brightness attenuation of the display picture by compensating the voltage, so that the AMLED can display a high-quality picture.

The basic spirit and other objects of the present invention, as well as the technical means and embodiments adopted by the present invention, will be readily understood by those skilled in the art after considering the following embodiments.

Drawings

In order to make the aforementioned and other objects, features, advantages and embodiments of the present invention comprehensible, the following description is made with reference to the accompanying drawings:

fig. 1 is a block diagram illustrating a driving circuit according to an embodiment of the present disclosure.

Fig. 2 is a detailed circuit diagram of a driving circuit according to an embodiment of the present disclosure.

FIG. 3 is a waveform diagram illustrating various control signal levels according to an embodiment of the present disclosure.

Fig. 4 to 6 are schematic diagrams illustrating the operation of the driving circuit shown in fig. 1 according to another embodiment of the present disclosure.

FIG. 7 is a detailed circuit diagram of a driving circuit according to yet another embodiment of the present disclosure.

FIG. 8 is a block diagram of a driving circuit according to another embodiment of the present disclosure.

Fig. 9 is a detailed circuit diagram of a driving circuit according to yet another embodiment of the disclosure.

FIG. 10 is a waveform diagram illustrating various control signal levels according to another embodiment of the present disclosure.

Fig. 11 to 13 are schematic diagrams illustrating the operation of the driving circuit shown in fig. 9 according to still another embodiment of the present disclosure.

FIG. 14 is a detailed circuit diagram of a driving circuit according to another embodiment of the present disclosure.

In accordance with conventional practice, the various features and elements of the drawings are not drawn to scale in order to best illustrate the specific features and elements associated with the present disclosure. Moreover, the same or similar reference numbers are used throughout the different drawings to refer to similar elements/components.

Wherein the reference numerals are as follows:

100. 100A, 800 and 800A: driving circuit

110. 110A, 810 and 810A: first driver

120. 820: second driver

T1: driving transistor

D1: light emitting diode

S1: first scanning signal

S2: second scanning signal

EM: transmitting signal

Data: data signal

Vdata: data signal

VDD: power supply voltage

VSS: second pull-down signal

T2-T6: transistor with a metal gate electrode

N: first node

Q: endpoint

Q1: second node

Detailed Description

In order to make the disclosure more thorough and complete, illustrative descriptions are provided below for embodiments and specific examples of the disclosure; it is not intended to be exhaustive or to limit the invention to the precise form disclosed. The embodiments are intended to cover the features of the various embodiments as well as the method steps and sequences for constructing and operating the embodiments. However, other embodiments may be utilized to achieve the same or equivalent functions and step sequences.

Unless defined otherwise herein, 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. Furthermore, as used herein, the singular tense of a noun, unless otherwise conflicting with context, encompasses the plural form of that noun; the use of plural nouns also covers the singular form of such nouns.

Further, as used herein, coupled or connected may mean that two or more elements are in direct physical or electrical contact with each other, or in indirect physical or electrical contact with each other, or that two or more elements are in operation or act with each other.

In this context, the term "circuit" broadly refers to an object that is connected in some manner by one or more transistors and/or one or more active and passive components to process a signal.

Certain terms are used throughout the description and following claims to refer to particular components. However, those of ordinary skill in the art will appreciate that the various elements may be referred to by different names. The description and the claims do not intend to distinguish between components that differ in name but not function. In the description and claims, the terms "include" and "comprise" are used in an open-ended fashion, and thus should be interpreted to mean "include, but not limited to.

Fig. 1 is a block diagram illustrating a driving circuit according to an embodiment of the present disclosure. As shown, the driving circuit 100 includes a driving transistor T1, a first driver 110, a second driver 120, and a light emitting diode D1, and the light emitting diode D1 includes an anode terminal and a cathode terminal. In terms of connection, the driving transistor T1 is coupled to the first driver 110, the first driver 110 is coupled to the second driver 120, and the anode terminal of the light emitting diode D1 is coupled to the first driver 110 or the driving transistor T1.

In order to provide a micro led driving circuit with high display quality, the driving circuit 100 shown in fig. 2 and waveforms of various control signal levels shown in fig. 3 are provided to control the driving circuit 100, and the operation of the driving circuit 100 is described in detail as follows.

As shown in fig. 2 and 3, the driving transistor T1 is used for outputting a driving signal according to the voltage stored at the first node N. For example, the driving signal may be a desired current Iled of the light emitting diode D1.

Subsequently, the first driver 110 is used for storing the data signal Vdata to the first node N according to the first scan signal S1, and determining whether to output the driving signal according to the first scan signal S1, the second scan signal S2 and the emission signal EM.

Then, the second driver 120 is used for providing a first compensation voltage to the first node N according to the driving signal and the emission signal EM outputted by the first driver 110. The led D1 is used for receiving a driving signal to emit light. For example, the second driver 120 may be a transistor T4.

FIG. 3 is a waveform diagram illustrating various control signal levels according to an embodiment of the present disclosure. Fig. 4 to 6 are schematic diagrams illustrating the operation of the driving circuit shown in fig. 1 according to another embodiment of the present disclosure. Referring to fig. 3 and 4 together, in one embodiment, the first driver T1 includes a storage capacitor C1. In the first phase P1, the storage capacitor C1 stores the data signal Vdata and the first pull-down signal Vref at the first terminal and the second terminal of the storage capacitor C1 respectively according to the first scan signal S1 and the second scan signal S2.

Referring to fig. 3 and 5, in another embodiment, in the second phase P2, the storage capacitor C1 stores the data signal Vdata and the second compensation voltage at the first end and the second end of the storage capacitor C1 respectively according to the first scan signal S1. For example, the threshold voltage of the transistor T1 is Vth _ T1, so the second compensation voltage is VDD-Vth _ T1.

Referring to fig. 3 and 6, in yet another embodiment, in the third stage P3, the storage capacitor stores the first compensation voltage and the coupling voltage at the first terminal and the second terminal of the storage capacitor C1 according to the emission signal EM, and the light emitting diode receives the driving signal to emit light. For example, the voltage value at the node Q is VSS + Vled and is transmitted to the first end of the storage capacitor through the transistor T4, so the first compensation voltage is VSS + Vled, however, the storage voltage at the first end of the storage capacitor C1 is adjusted to VSS + Vled by the data signal Vdata, so the voltage adjustment value (VSS + Vled-Vdata) at the first end of the storage capacitor C1 is coupled to the second end of the storage capacitor C1, plus the second compensation voltage (VDD-Vth _ T1) originally stored at the second end of the storage capacitor C1, and finally the coupling voltage stored at the second end of the storage capacitor C1 is (VDD-Vth _ T1+ Vled + VSS-Vdata).

In another embodiment, the calculation of the driving signal is as follows. Referring to fig. 6, the driving signal is calculated as follows:

iled is the driving signal, k is the process parameter of the transistor T1, Vsg _ T1 is the source-gate voltage of the transistor T1, and Vth _ T1 is the threshold voltage of the transistor T1. Further, Vsg _ T1 is Vs _ T1-Vg _ T1. For example, Vg _ T1 is the gate voltage of the transistor T1, and Vg _ T1 is VDD- | Vth _ T1| + Vled + VSS-Vdata. In addition, Vs _ T1 is the source voltage of the transistor T1, and in this case, the source voltage of the transistor T1 is the power supply voltage VDD, so Vsg _ T1 is VDD- (VDD- | Vth _ T1| + Vled + VSS-Vdata) | Vth _ T1| -Vled-VSS + Vdata because the source voltage Vs _ T1 is VDD.

Then, the calculation formula of the driving signal obtained by substituting the Vsg _ T1 into formula 1 is as follows:

since the luminance of the led is equal to the product of the light emitting efficiency and the driving signal Iled, when the light emitting efficiency and the voltage drop (Vled) of the led become small due to the thermal effect, as shown in formula 2, when the process parameter k of the transistor T1, the data signal Vdata and the second pull-down signal Vss are constant values, the driving signal Iled becomes large while the voltage drop Vled of the led becomes small, thereby compensating the luminance decay phenomenon of the led due to the decrease of the light emitting efficiency.

FIG. 7 is a detailed circuit diagram of a driving circuit according to yet another embodiment of the present disclosure. Compared to the driving circuit 100 shown in fig. 1, the driving circuit 100A of fig. 7 has a different connection manner of the driving transistor T4. In one embodiment, one end of the transistor T4 of the driving circuit 100A is also coupled to the first node N, but the other end of the transistor T4 of the driving circuit 100A is coupled to the second node Q1 between the transistor T6 and the driving transistor T1. It should be noted that, in the embodiment of fig. 7, the element numbers are similar to those in fig. 1, and have similar structural and electrical operation features, and are not described herein again for brevity of the description.

FIG. 8 is a block diagram of a driving circuit according to another embodiment of the present disclosure. Fig. 9 is a detailed circuit diagram of a driving circuit according to yet another embodiment of the disclosure. Referring to fig. 8 and 9 together, in an embodiment, the driving circuit 800 includes a light emitting diode D1, a first driving circuit 810, a second driving circuit 820, and a driving transistor T1. The led D1 includes an anode terminal and a cathode terminal. In terms of connection, the cathode terminal of the led D1 is coupled to the first driver 810 or the driving transistor T1, the first driver 810 is coupled to the second driver 820, and the driving transistor T1 is coupled to the first driver 810.

In operation, the led D1 is used for receiving a driving signal to emit light. The first driver 810 is used for storing the data signal Vdata to the first node N according to the first scan signal S1, and determining whether to provide the driving signal according to the first scan signal S1, the second scan signal S2 and the emission signal EM. For example, the driving signal may be a desired current Iled of the light emitting diode.

Then, the second driver 820 is used to provide the first compensation voltage to the first node N according to the emission signal EM. The driving transistor T1 is used for providing a driving signal to the light emitting diode according to the data signal stored at the first node N and the first compensation voltage. For example, the second driver 820 may be a transistor T4.

FIG. 10 is a waveform diagram illustrating various control signal levels according to another embodiment of the present disclosure. Fig. 11 to 13 are schematic diagrams illustrating the operation of the driving circuit shown in fig. 9 according to still another embodiment of the present disclosure. Referring to fig. 10 and 11 together, in one embodiment, the first driver 810 includes a storage capacitor C1. In the first phase P1, the storage capacitor C1 stores the data signal Vdata and the first pull-down signal Vref at the first terminal and the second terminal of the storage capacitor C1 respectively according to the first scan signal S1 and the second scan signal S2.

Referring to fig. 10 and 12, in another embodiment, in the second phase P2, the storage capacitor C1 stores the data signal Vdata and the second pull-down signal VSS at the first end and the second end of the storage capacitor C1 respectively according to the first scan signal S1. For example, the threshold voltage of the transistor T1 is Vth _ T1, so the second compensation voltage is VSS + Vth _ T1.

Referring to fig. 10 and 13, in yet another embodiment, in the third stage P3, the storage capacitor C1 stores the first compensation voltage and the coupling voltage at the first terminal and the second terminal of the storage capacitor C1, respectively, according to the emission signal EM. Then, the light emitting diode D1 emits light in response to the drive signal. For example, the voltage value of the node Q is (VDD-Vled), however, the voltage stored at the first terminal of the storage capacitor C1 is adjusted to (VDD-Vled) by the data signal Vdata, so that the voltage adjustment value (VDD-Vled-Vdata) at the first terminal of the storage capacitor C1 is coupled to the second terminal of the storage capacitor C1, and the second compensation voltage (VSS + Vth _ T1) originally stored at the second terminal of the storage capacitor C1 is added, and finally the coupling voltage stored at the second terminal of the storage capacitor C1 is (VSS + Vth _ T1-Vled + VDD-Vdata).

In another embodiment, the calculation of the driving signal is as follows. Referring to fig. 10, the driving signal is calculated as follows:

iled is the driving signal, k is the process parameter of the transistor T1, Vgs _ T1 is the gate-source voltage of the transistor T1, and Vth _ T1 is the threshold voltage of the transistor T1. In addition, Vgs _ T1 is Vg _ T1 Vs _ T1. For example, Vg _ T1 is the gate voltage of the transistor T1, and Vg _ T1 is VSS + Vth _ T1-VLED + VDD-Vdata. In addition, the source voltage Vs _ T1 is the source voltage of the transistor T1, and in this case, the source voltage of the transistor T1 is the second pull-down signal VSS, so that the source voltage Vs _ T1 is VSS, and therefore Vgs _ T1 is (VSS + Vth _ T1-VLED + VDD-Vdata) -VSS is Vth _ T1-VLED + VDD-Vdata.

Then, substituting the above-mentioned Vgs _ T1 into equation 3 can obtain the following calculation equation of the driving signal:

since the luminance of the led is equal to the product of the light emitting efficiency and the driving signal Iled, when the light emitting efficiency and the voltage drop (Vled) of the led become small due to the thermal effect, as shown in formula 4, when the process parameter k of the transistor T1, the power supply voltage VDD and the data signal Vdata are constant values, the driving signal Iled becomes large while the voltage drop Vled of the led becomes small, thereby compensating the luminance degradation phenomenon of the led due to the decrease of the light emitting efficiency.

FIG. 14 is a detailed circuit diagram of a driving circuit according to another embodiment of the present disclosure. Compared to the driving circuit 800 shown in fig. 8, the driving circuit 800A in fig. 14 has a different connection manner of the driving transistor T4. In one embodiment, one end of the transistor T4 of the driving circuit 800A is also coupled to the first node N, but the other end of the transistor T4 of the driving circuit 800A is coupled to the second node Q1 between the transistor T6 and the driving transistor T1. It should be noted that, in the embodiment of fig. 7, the element numbers are similar to those in fig. 1, and have similar structural and electrical operation features, and are not described herein again for brevity of the description.

According to the embodiments of the present invention, the following advantages can be obtained. The driving

circuits

100, 100A, 800A according to the embodiments of the present disclosure can prevent the brightness of the AMLED from being attenuated with the temperature increase during the operation of the AMLED. In addition, the driving

circuits

100, 100A, 800A of the present disclosure can compensate the voltage to improve the problem of the brightness attenuation of the display screen, so that the AMLED can display a high quality screen.

Although the embodiments of the present invention have been disclosed in the above description, it should be understood that the present invention is not limited thereto. It should be noted that the shapes, sizes and proportions of the elements in the drawings are illustrative only and are not intended to be limiting, since the disclosure will be understood by those skilled in the art. Various modifications and alterations may be made without departing from the principles and spirit of the present disclosure by those skilled in the art, and the scope of protection is therefore intended to be defined by the appended claims.

Claims

1. A driving circuit, comprising:

a driving transistor for outputting a driving signal according to a voltage stored at a first node;

a first driver for storing a data signal to the first node according to a first scan signal and determining whether to output the driving signal according to the first scan signal, a second scan signal and an emission signal;

a second driver for providing a first compensation voltage to the first node according to the driving signal and the transmitting signal output by the first driver; and

and a light emitting diode including an anode terminal and a cathode terminal, wherein the anode terminal is coupled to the first driver or the driving transistor and is configured to receive the driving signal to emit light.

2. The driving circuit of claim 1, wherein the first driver comprises a storage capacitor, wherein the storage capacitor stores the data signal and a first pull-down signal at a first end and a second end of the storage capacitor according to the first scan signal and the second scan signal during a first phase.

3. The driving circuit as claimed in claim 2, wherein the storage capacitor stores the data signal and a second compensation voltage at the first terminal and the second terminal of the storage capacitor according to the first scan signal during a second phase.

4. The driving circuit as claimed in claim 3, wherein in a third phase, the storage capacitor stores the first compensation voltage and a coupling voltage at the first terminal and the second terminal of the storage capacitor according to the emission signal, wherein the light emitting diode receives the driving signal to emit light.

5. The driving circuit as claimed in claim 1, wherein the second driver, the first driver and the driving transistor are coupled to a second node.

6. A driving circuit, comprising:

a light emitting diode including an anode terminal and a cathode terminal for receiving a driving signal to emit light;

a first driver for storing a data signal to a first node according to a first scan signal and determining whether to provide the driving signal according to the first scan signal, a second scan signal and an emission signal;

a second driver for providing a first compensation voltage to the first node according to the transmission signal; and

and a driving transistor for providing the driving signal to the light emitting diode according to the data signal stored in the first node and the first compensation voltage, wherein the cathode terminal is coupled to the first driver or the driving transistor.

7. The driving circuit as claimed in claim 6, wherein the first driver comprises a storage capacitor, wherein the storage capacitor stores the data signal and a first pull-down signal at a first end and a second end of the storage capacitor according to the first scan signal and the second scan signal during a first phase.

8. The driving circuit as claimed in claim 7, wherein the storage capacitor stores the data signal and a second pull-down signal at the first terminal and the second terminal of the storage capacitor according to the first scan signal during a second phase.

9. The driving circuit as claimed in claim 8, wherein in a third phase, the storage capacitor stores the first compensation voltage and a coupling voltage at the first terminal and the second terminal of the storage capacitor according to the emission signal, wherein the light emitting diode receives the driving signal to emit light.

10. The driving circuit as claimed in claim 6, wherein the first driver, the second driver and the driving transistor are coupled to a second node.