CN114842804B - Pixel driving circuit, display panel and electronic equipment - Google Patents

Pixel driving circuit, display panel and electronic equipment Download PDF

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Publication number
CN114842804B
CN114842804B CN202210501669.3A CN202210501669A CN114842804B CN 114842804 B CN114842804 B CN 114842804B CN 202210501669 A CN202210501669 A CN 202210501669A CN 114842804 B CN114842804 B CN 114842804B
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voltage
output
organic light
compensation
input end
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CN114842804A (en
Inventor
胡巍浩
倪恩伟
南帐镇
赵楠
陈伟雄
李阳恒
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Beijing Eswin Computing Technology Co Ltd
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Beijing Eswin Computing Technology Co Ltd
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    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
    • G09G3/22—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources
    • G09G3/30—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels
    • G09G3/32—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED]
    • G09G3/3208—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED] organic, e.g. using organic light-emitting diodes [OLED]
    • G09G3/3225—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED] organic, e.g. using organic light-emitting diodes [OLED] using an active matrix
    • G09G3/3233—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED] organic, e.g. using organic light-emitting diodes [OLED] using an active matrix with pixel circuitry controlling the current through the light-emitting element
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2320/00—Control of display operating conditions
    • G09G2320/02—Improving the quality of display appearance
    • G09G2320/0233—Improving the luminance or brightness uniformity across the screen

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Computer Hardware Design (AREA)
  • General Physics & Mathematics (AREA)
  • Theoretical Computer Science (AREA)
  • Control Of Indicators Other Than Cathode Ray Tubes (AREA)
  • Electroluminescent Light Sources (AREA)

Abstract

The application discloses a pixel driving circuit, a display panel and electronic equipment, and belongs to the technical field of display. The pixel driving circuit includes: the organic light-emitting element, the driving module, the conduction control module and the compensation module can acquire the output voltage of the organic light-emitting element when the organic light-emitting element is turned on and emits light through the conduction control module, and provide the compensation voltage to the input end of the organic light-emitting element under the condition that the voltage degradation of the organic light-emitting element is determined based on the output voltage. When judging that the voltage of the organic light-emitting element is declined, the compensation module provides compensation voltage for the input end of the organic light-emitting element, and can improve the on current of the organic light-emitting element when the brightness of the organic light-emitting element is reduced, so that the brightness of the organic light-emitting element can be improved, the brightness uniformity of a plurality of organic light-emitting elements in the display panel is maintained, and the problem of uneven brightness of the display panel can be avoided.

Description

Pixel driving circuit, display panel and electronic equipment
Technical Field
The application belongs to the technical field of display, and particularly relates to a pixel driving circuit, a display panel and electronic equipment.
Background
The organic light-emitting element panel is a technology for displaying by utilizing the self-luminous principle of organic light-emitting materials, and has the advantages of low driving voltage, rich colors, short response time, high definition and contrast, and the like.
As the service time increases, the organic luminescent material may decline, and when the production process and/or the process of the organic luminescent material are different, the decline speed is also different. The organic light emitting element is, for example, an organic light emitting diode (Organic Light Emitting Diode, OLED), and after each turn-on of the OLED, the resistance increases with an increase in the turn-on time due to degradation of the organic light emitting material, and in the case where the pixel voltage is stable, the current flowing into the OLED becomes small, which results in voltage degradation of the cathode of the OLED and thus a decrease in the brightness of the OLED. In the whole display panel, the attenuation degree of the organic luminescent materials in different OLEDs is different, so that the voltage decay amplitude of the different OLEDs is different, the brightness of the different OLEDs is different, and further the display panel has the problem of Mura, namely uneven brightness.
Content of the application
The embodiment of the application aims to provide a pixel driving circuit, a display panel and electronic equipment, which can solve the problem of uneven brightness of the display panel in the prior art.
In order to solve the technical problems, the application is realized as follows:
in a first aspect, an embodiment of the present application provides a pixel driving circuit, including: the organic light-emitting device comprises an organic light-emitting element, a driving module, a conduction control module and a compensation module;
the driving module is connected with a first input end of the organic light-emitting element, and a first output end of the organic light-emitting element is connected with a common electrode end of the pixel driving circuit; the driving module is used for providing pixel voltage for the first input end under the condition of receiving a conduction signal so as to conduct and emit light of the organic light-emitting element;
one end of the conduction control module is connected with the first output end, and the other end of the conduction control module is connected with the second input end of the compensation module and is used for conducting the second input end of the compensation module with the first output end under the condition of receiving a detection signal; and when the detection signal is received, no voltage is input to the common electrode terminal; the detection signal is after the conduction signal;
the second output end of the compensation module is connected with the first input end and is used for acquiring the output voltage of the organic light-emitting element and providing compensation voltage for the first input end under the condition that the voltage degradation of the organic light-emitting element is determined based on the output voltage.
In a second aspect, an embodiment of the present application provides a display panel, including the pixel driving circuit described in the first aspect.
In a third aspect, an embodiment of the present application provides an electronic device, including the display panel in the second aspect.
In the embodiment of the application, the pixel driving circuit comprises an organic light emitting element, a driving module, a conduction control module and a compensation module, wherein the driving module is connected with a first input end of the organic light emitting element, and a first output end of the organic light emitting element is connected with a common electrode end of the pixel driving circuit; the driving module is used for providing pixel voltage for the first input end under the condition of receiving the conduction signal so as to conduct and emit light of the organic light-emitting element; one end of the conduction control module is connected with the first output end, and the other end of the conduction control module is connected with the second input end of the compensation module and is used for conducting the second input end of the compensation module with the first output end under the condition of receiving the detection signal; and when the detection signal is received, no voltage is input to the common electrode terminal; the detection signal is after the turn-on signal; the second output end of the compensation module is connected with the first input end and is used for acquiring the output voltage of the organic light-emitting element and providing the compensation voltage to the first input end under the condition that the voltage degradation of the organic light-emitting element is determined based on the output voltage. When judging that the voltage of the organic light-emitting element is declined, the compensation module provides compensation voltage for the input end of the organic light-emitting element, and can improve the on current of the organic light-emitting element when the brightness of the organic light-emitting element is reduced, so that the brightness of the organic light-emitting element can be improved, the brightness uniformity of a plurality of organic light-emitting elements in the display panel is maintained, and the problem of uneven brightness of the display panel can be avoided.
Drawings
Fig. 1 shows a circuit schematic of a pixel driving circuit in the prior art;
fig. 2 shows a schematic structural diagram of a pixel driving circuit according to an embodiment of the present application;
fig. 3 is a schematic circuit diagram of a pixel driving circuit according to an embodiment of the present application;
fig. 4 shows a timing control diagram of a pixel driving circuit according to an embodiment of the present application;
fig. 5 is a schematic circuit diagram of another pixel driving circuit according to an embodiment of the present application;
fig. 6 is a schematic circuit diagram of a pixel driving circuit according to another embodiment of the present application;
fig. 7 is a schematic circuit diagram of a pixel driving circuit according to another embodiment of the present application;
FIG. 8 is a flow chart showing steps of a voltage compensation method according to an embodiment of the present application;
fig. 9 is a schematic flow chart of a voltage compensation method according to an embodiment of the present application;
fig. 10 shows a schematic structural diagram of an electronic device according to an embodiment of the present application.
Detailed Description
To describe the technical solution in the embodiments of the present application in more detail, first, a brief description of a pixel driving circuit in the prior art will be given.
As shown in fig. 1, fig. 1 shows a schematic circuit diagram of a pixel driving circuit in the prior art, where the pixel driving circuit is disposed in a display panel, and includes an organic light emitting diode 101 and a driving module 102, where the organic light emitting diode 101 is a pixel in the display panel, and the driving module 102 is used to control on and off of the organic light emitting diode. The pixel driving circuit is a 7T1C pixel driving circuit, the driving module 102 is composed of 7P-type Thin Film Transistors (TFTs) and a capacitor, M1, M2, M3, M4, M5, M6 and M7 respectively represent 7 Thin Film transistors in the driving module 102, C1 represents the capacitor, ELVDD represents the positive voltage of the power supply, ELVSS represents the negative voltage of the power supply, data represents the Data signal, scan1 represents the reset signal, scan2 represents the Scan signal, EM represents the enable signal, and Vref represents the reference voltage. The thin film transistor in the driving module 102 may also be an N-type thin film transistor, so that the circuit is clearly illustrated, in this embodiment, the gate electrode of the P-type thin film transistor is referred to as a control terminal, the source electrode is referred to as an input terminal, the drain electrode is referred to as an output terminal, the gate electrode of the N-type thin film transistor is referred to as a control terminal, the drain electrode is referred to as an input terminal, and the source electrode is referred to as an output terminal.
The output end of the thin film transistor M5 forms the output end of the driving module 102, and the output end of the thin film transistor M5 is connected to a pixel electrode in the display panel, and the voltage of the pixel electrode may be referred to as a pixel voltage. The pixel electrode is connected to the anode of the organic light emitting diode 101, and the cathode of the organic light emitting diode 101 is connected to the common electrode terminal 103 in the pixel driving circuit. The input end of the thin film transistor M2 is connected with the positive voltage output end of a power management chip (Power Management Integrated Circuits, PMIC) in the display panel to obtain a power positive voltage ELVDD; the common electrode terminal 103 is connected with a common electrode line in the display panel, and the common electrode line is connected with a negative voltage output terminal in the PMIC so as to acquire a power supply negative voltage ELVSS; the input ends of the thin film transistor M6 and the thin film transistor M7 are connected with the reference voltage output end in the PMIC to obtain a reference voltage Vref; the PMIC may be integrated in a display driving chip in the display panel or may be provided separately from the display driving chip. The input end of the thin film transistor M1 is connected with the output end of the Data driver in the display driving chip to acquire the Data signal Data output by the Data driver, and the control ends of the thin film transistor M1 and the thin film transistor M4 are connected with the output end of the scanning driver in the display driving chip to acquire the scanning signal Scan2 output by the scanning driver. The control ends of the thin film transistor M6 and the thin film transistor M7 are connected with the display driving chip to acquire a reset signal Scan1 output by the display driving chip, and the control ends of the thin film transistor M5 and the thin film transistor M2 are connected with the display driving chip to acquire an enable signal EM output by the display driving chip. The operation process of the pixel driving circuit may be divided into an initialization phase, a precharge phase and a light emitting phase, and the driving module 102 may input a pixel voltage to the anode of the organic light emitting diode 101 in the light emitting phase, so that the organic light emitting diode 101 is turned on to emit light.
In the initialization stage, the reset signal Scan1 is low level, the Scan signal Scan2 and the enable signal EM are high level, the input terminals of the thin film transistor M6 and the thin film transistor M7 input the reference voltage Vref, the control terminal inputs the reset signal Scan1 of low level, the thin film transistor M6 and the thin film transistor M7 are turned on, the other thin film transistors in the driving module 102 are turned off, and the reference voltage Vref is used for carrying out one-time reverse initialization on the electric potential of the capacitor C1 and the pixel electrode.
In the precharge phase, the Scan signal Scan2 is low, and the reset signal Scan1 and the enable signal EM are high. The input terminal of the thin film transistor M1 inputs the Data signal Data, and the control terminal inputs the Scan signal Scan2 of low level, so that the thin film transistor M1 is turned on. The voltage of the control terminal of the thin film transistor M3 is initialized to the reference voltage Vref in the initialization stage, and the turn-on of the thin film transistor M1 causes the input terminal of the thin film transistor M3 to input the Data signal Data, thereby turning on the thin film transistor M3. The thin film transistor M3 is turned on, so that the Data signal Data is inputted to the input terminal of the thin film transistor M4, and the thin film transistor M4 is turned on under the action of the Scan signal Scan2 of low level. At this time, the Data signal Data charges the capacitor C1 through the thin film transistors M1, M3 and M4.
In the light emitting stage, the enable signal EM is low, and the reset signal Scan1 and the Scan signal Scan2 are high. The input terminal of the thin film transistor M2 inputs the power supply positive voltage ELVDD, and the low-level enable signal EM is input to the control terminal of the thin film transistor M2, so that the thin film transistor M2 is turned on. The thin film transistor M2 is turned on, so that the source electrode of the thin film transistor M3 inputs the power supply positive voltage ELVDD, and the thin film transistor M3 is turned on. The thin film transistor M3 is turned on, so that the power supply positive voltage ELVDD is input to the input terminal of the thin film transistor M5, and the thin film transistor M5 is turned on under the effect of the enable signal EM input to the control terminal, and the pixel voltage is input to the pixel electrode, that is, the anode of the organic light emitting diode OLED. The organic light emitting diode 201 is turned on to emit light by the pixel voltage and the power supply negative electrode voltage ELVSS.
During the use of the display panel, the OLED increases in resistance with increasing on-time after each turn-on due to degradation of the organic light emitting material. Accordingly, under the condition that the pixel voltage is stable, the on-current of the OLED becomes smaller along with the increase of the impedance, so that the cathode of the OLED is degraded in voltage, and the brightness of the OLED is reduced. In the whole display panel, the attenuation degree of the organic luminescent materials in different OLEDs is different, so that the brightness of different OLEDs is reduced differently, which causes the problem that Mura, namely uneven brightness, occurs in the display panel.
In order to solve the above technical problems, a first aspect of the embodiments of the present application provides a pixel driving circuit, and the detailed description of the pixel driving circuit provided by the embodiments of the present application is given below with reference to the accompanying drawings.
Referring to fig. 2, fig. 2 shows a schematic structural diagram of a pixel driving circuit according to an embodiment of the present application, where the pixel driving circuit includes an organic light emitting element 201, a driving module 202, a conduction control module 203, and a compensation module 204.
Wherein the driving module 202 is connected to a first input terminal of the organic light emitting element 201, and a first output terminal of the organic light emitting element is connected to a common electrode terminal 205 of the pixel driving circuit; the driving module 202 is configured to provide a pixel voltage to the first input terminal to make the organic light emitting element 201 emit light when receiving the on signal; one end of the conduction control module 203 is connected with the first output end, and the other end is connected with the second input end of the compensation module 204, so that the second input end of the compensation module 204 is conducted with the first output end under the condition that a detection signal is received; and when the detection signal is received, the common electrode terminal 205 has no voltage input; the detection signal is after the turn-on signal; the second output terminal of the compensation module 204 is connected to the first input terminal, and is configured to obtain an output voltage of the organic light emitting element 201, and provide a compensation voltage Vem to the first input terminal when it is determined that the organic light emitting element 201 experiences voltage degradation based on the output voltage.
In this embodiment, the organic light emitting element is an organic light emitting diode, the first input terminal is an anode of the organic light emitting diode, and the first output terminal is a cathode of the organic light emitting diode. The turn-on control module 203 is configured to control the second input terminal of the compensation module 204 to be turned on with the cathode of the organic light emitting diode 201 after the organic light emitting diode 201 is turned on, and the compensation module 204 can obtain an output voltage of the organic light emitting diode 201, where the output voltage is a cathode voltage of the organic light emitting diode, and then determine whether a voltage decay occurs in the cathode of the organic light emitting diode 201 according to the output voltage. The occurrence of voltage decay at the cathode of the organic light emitting diode 201 marks a decrease in the on-current of the organic light emitting diode 201, and when the on-current decreases, the brightness of the organic light emitting diode decreases. The compensation module 204 may output the compensation voltage Vem to the anode of the organic light emitting diode 201 to increase the on current of the organic light emitting diode 201 and further increase the brightness of the organic light emitting diode 201 when determining that the organic light emitting diode 201 has voltage degradation. The organic light emitting element may be any other type of organic light emitting element, and the embodiment is not limited thereto.
Illustratively, the driving module 202 may use the driving module shown in fig. 1 or use a driving module in other types of pixel driving circuits, where the anode of the organic light emitting diode 201 is connected to the pixel electrode in the pixel driving circuit and the cathode is connected to the common electrode terminal 205 in the pixel driving circuit. The on signal may be an enable signal EM output by the display driving chip, and when the driving module 202 receives the on signal, the pixel voltage is input to the anode of the organic light emitting diode 201, so that the organic light emitting diode 201 is turned on to emit light under the action of the pixel voltage and the power supply negative voltage ELVSS. The turn-on control module 203 is connected to the display driving chip, and the detection signal may be a control signal sent to the turn-on control module 203 after the display driving chip outputs the enable signal to turn on the organic light emitting diode 201, after a preset period of time, and before outputting the detection signal, the display driving chip may output an indication signal to the PMIC to instruct the PMIC to stop outputting the power supply negative voltage to the common electrode terminal 205, so that the common electrode terminal has no voltage input. The turn-on control module 203 may control the input terminal of the compensation module 204 and the cathode of the organic light emitting diode 201 to be turned on after receiving the detection signal. At this time, the compensation module 203 may obtain the output voltage of the organic light emitting diode 201, and output the compensation voltage Vem to the anode of the organic light emitting diode 201 when judging that the voltage of the organic light emitting diode 201 is degraded according to the output voltage.
The display driving chip can output an indication signal after outputting a conduction signal and before outputting a detection signal, so that the common electrode terminal has no voltage input and is in a suspended state. Or the display driving chip can output the detection signal and the indication signal simultaneously, and the input end of the compensation module is controlled by the conduction control module to be conducted with the first output end of the organic light-emitting element while the common electrode end is controlled to have no voltage input, so that the influence of the power supply negative voltage of the common electrode end on the output voltage obtained by the compensation module is avoided.
Optionally, the compensation module comprises a voltage acquisition unit and a control output unit; the input end of the voltage acquisition unit is connected with the conduction control module, and the voltage acquisition unit is connected with the control output unit in a communication way; the voltage acquisition unit is used for acquiring output voltage under the condition of being conducted with the first output end and sending the output voltage to the control output unit; the output terminal of the control output unit is connected with the first input terminal for providing the compensation voltage to the first input terminal in case it is determined that the organic light emitting element has voltage decay based on the output voltage.
In one embodiment, the compensation module may include a voltage acquisition unit and a control output unit, wherein an input end of the voltage acquisition unit is a second input end of the compensation module, and an output end of the control output unit is a second output end of the compensation module. The input end of the voltage acquisition unit is connected with the conduction control module, and when the input end of the voltage acquisition unit is conducted with the first output end of the organic light-emitting element, the voltage acquisition unit can acquire the output voltage of the organic light-emitting element through the input end. The voltage acquisition unit is in communication connection with the control output unit, and after the output voltage of the analog quantity is acquired, the voltage acquisition unit can convert the acquired output voltage of the analog quantity into the output voltage of the digital quantity and send the output voltage of the digital quantity to the control output unit. As shown in fig. 3, fig. 3 shows a schematic circuit diagram of a pixel driving circuit according to an embodiment of the present application, where the pixel driving circuit includes an organic light emitting diode 201, a driving module 202, a conduction control module and a compensation module 204, the conduction control module includes a connection switch tube 203, and the compensation module 204 includes a voltage acquisition unit 2041 and a control output unit 2042. The type of the connection switching tube 203 may be consistent with the type of the thin film transistor included in the driving module 202 so as to provide a control voltage matched with the control terminal of the connection switching tube 203, that is, a detection signal received by the connection switching tube 203. The input end of the connection switch tube 203 is connected with the cathode of the organic light emitting diode 201, the output end is connected with the input end of the voltage acquisition unit 2041, and the control end of the connection switch tube 203 is connected with the display driving chip, so as to receive the detection signal Gate output by the display driving chip. Alternatively, the voltage acquisition unit 2041 may be implemented using an analog-to-digital converter, the input terminal of the voltage acquisition unit 2041 is connected to the output terminal of the connection switching tube 203, and the voltage acquisition unit 2041 may be communicatively connected to the control output unit 2042 through a communication interface. Alternatively, the control output unit 2042 may be a PMIC in the display panel, which may be a PMIC included in the display driving chip or may be a PMIC independent of the display driving chip.
In connection with the above example, when the driving module 202 receives the on signal (enable signal EM) sent by the display driving chip, the pixel voltage may be input to the pixel electrode to control the organic light emitting diode 201 to emit light. After the organic light emitting diode 201 is turned on, the display driving chip may send a low-level detection signal to the control terminal of the connection switching tube 203, so that the connection switching tube 203 is turned on, and thus the input terminal of the voltage acquisition unit 2041 may be turned on with the cathode of the organic light emitting diode 201. At this time, the voltage acquisition unit 2041 may acquire the voltage of the cathode of the organic light emitting diode 201, obtain an output voltage, convert the acquired output voltage of the analog quantity into the output voltage of the digital quantity, and transmit the output voltage of the digital quantity to the control output unit 2042. The output terminal of the control output unit 2042 is connected to the anode of the organic light emitting diode 201, and the control output unit 2042 may output the compensation voltage Vem to the anode of the organic light emitting diode 201 when it is determined that the cathode of the organic light emitting diode 201 is degraded according to the output voltage, or may not output the compensation voltage Vem when it is determined that the cathode of the organic light emitting diode 201 is not degraded.
Optionally, the conduction control module is configured to conduct the input end of the voltage acquisition unit with the first output end for the first time when the first detection signal is received, and conduct the input end of the voltage acquisition unit with the first output end for the second time when the second detection signal is received; the first detection signal and the conduction signal are separated by a preset conduction time length, and the second detection signal and the conduction signal are separated by a preset decay time length; the preset decay time length is longer than the preset conduction time length; the voltage acquisition unit is used for acquiring the conduction output voltage of the organic light-emitting element under the condition of being conducted with the first output end for the first time and acquiring the declining output voltage of the organic light-emitting element under the condition of being conducted with the first output end for the second time; the voltage acquisition unit is also used for sending a conduction output voltage and a declining output voltage to the control output unit or sending a voltage difference value between the conduction output voltage and the declining output voltage to the control output unit; the output end of the control output unit is connected with the first input end and is used for providing compensation voltage for the first input end under the condition that the voltage difference value is larger than the voltage difference threshold value.
In one embodiment, the control output unit may determine whether the voltage decay of the organic light emitting element occurs according to a voltage difference between the on output voltage and the decay output voltage of the organic light emitting element. The conduction output voltage is close to the output voltage of the organic light-emitting element at the conduction moment, and the declining output voltage is the output voltage of the organic light-emitting element when the voltage of the organic light-emitting element declines after the organic light-emitting element is conducted for a preset declining duration. As shown in fig. 4, fig. 4 shows a timing control diagram of a pixel driving circuit according to an embodiment of the present application, and in combination with fig. 3, a turn-on control module includes a connection switch tube 203, after the display driving chip sequentially outputs a reset signal Scan1, a Scan signal Scan2 and an enable signal EM to turn on the organic light emitting diode, timing may be started at a turn-on time point (a turn-on time point, i.e., a time point when the enable signal is output) of the organic light emitting diode, when the timing time length reaches a preset turn-on time length, it is determined that the timing time length reaches a first time point, a low-level first detection signal Gate1 is input to a control end of the connection switch tube 203 at the first time point, and the connection switch tube 203 is controlled to be turned on for the first time, so that an input end of the voltage acquisition unit 2041 is turned on with a cathode of the organic light emitting diode 201 for the first time, a preset turn-on time length is preset between the first time point and the turn-on time point, and when the input end of the voltage acquisition unit 2041 is detected with the cathode of the organic light emitting diode 201 is turned on for the preset output voltage. The first output voltage obtained at the first time point is a conduction output voltage, and the conduction output voltage can be close to the output voltage of the organic light emitting diode at the conduction moment by controlling the preset conduction time. The preset detection duration is, for example, 5 seconds, and the first detection signal Gate1 ends after the duration is 5 seconds, that is, the first detection signal Gate1 changes from low level to high level, the connection switch tube 203 is turned off, the display driving chip can continue to time, when the time duration reaches the preset decay duration, it is determined that the second time point is reached, the display driving chip can input the second detection signal Gate2 to the control end of the connection switch tube 203 at the second time point, and the connection switch tube 203 is controlled to be turned on for the second time, so that the input end of the voltage acquisition unit 2041 is turned on with the cathode of the organic light emitting diode 201 for the second time. The second time point and the on time point are spaced by a preset decay time period, and the second detection signal lasts for 5 seconds, so that the voltage acquisition unit 2041 can acquire a second output voltage, namely a decay output voltage. After the voltage acquisition unit 2041 acquires the on output voltage and the decay output voltage, the acquired on output voltage and decay output voltage are sent to the control output unit 2042, the control output unit 2042 may calculate a voltage difference between the on output voltage and the decay output voltage, compare the voltage difference with a voltage difference threshold, determine that voltage decay occurs at the cathode of the organic light emitting diode 201 when the comparison determines that the voltage difference is greater than the voltage difference threshold, and may start outputting the compensation voltage Vem to the anode of the organic light emitting diode 201. In contrast, in the case where the comparison determines that the voltage difference is less than or equal to the voltage difference threshold, the compensation voltage Vem is not outputted to the anode of the organic light emitting diode 201. Alternatively, the voltage acquisition unit 2041 may calculate the voltage difference between the on output voltage and the off output voltage after acquiring the on output voltage and the off output voltage, and send the voltage difference between the on output voltage and the off output voltage to the control output unit.
The voltage difference threshold may be set according to requirements, for example, the voltage difference threshold may be a preset percentage of the on output voltage. In practical applications, the output voltage of the organic light emitting element at the first time point and the output voltage of the organic light emitting element at the second time point may be obtained in advance before the organic light emitting element has no larger voltage decay, and the voltage difference between the two output voltages may be stored as a voltage difference threshold in the control output unit. After the control output unit obtains the voltage difference between the on output voltage and the decay output voltage, the voltage difference threshold value stored in advance and the obtained voltage difference value can be compared to determine whether the voltage decay occurs in the organic light emitting element.
Optionally, the conduction control module is configured to conduct the input end of the voltage acquisition unit with the first output end under the condition that the second detection signal is received; the second detection signal and the conduction signal are separated by a preset decay time length; the voltage acquisition unit acquires the declining output voltage of the organic light-emitting element under the condition of being conducted with the first output end, and sends the declining output voltage to the control output unit; the output end of the control output unit is connected with the first input end and is used for providing compensation voltage for the first input end under the condition that the declining output voltage is smaller than the declining voltage threshold value.
In another embodiment, the voltage acquisition unit may only acquire the degradation output voltage and send the degradation output voltage to the control output unit, and the control output unit may determine whether the voltage degradation occurs in the organic light emitting element according to the degradation output voltage. In combination with the above example, after the display driver chip outputs the enable signal EM, the second detection signal may be input to the control terminal of the connection switch 203 only at the second time point, and at this time, the voltage acquisition unit 2041 may acquire the output voltage, obtain the recession output voltage, and send the recession output voltage to the control output unit 2042. After receiving the decay output voltage, the control output unit 2042 may compare the decay voltage threshold stored in advance with the decay output voltage, and if the decay output voltage is smaller than the preset decay voltage threshold, determine that the cathode of the organic light emitting diode has voltage decay, and may input the compensation voltage to the anode of the organic light emitting diode 201.
Wherein the output voltage of the organic light emitting element at the second time point may be obtained in advance before the occurrence of the large decay, and stored in the control output unit as the decay voltage threshold. After receiving the decay output voltage sent by the voltage acquisition unit, the control output unit can compare a pre-stored decay voltage threshold value with the decay output voltage to determine whether voltage decay occurs in the organic light emitting element.
In practical applications, the display panel includes a large number of pixel driving circuits, and separately setting a compensation module for each pixel driving circuit can significantly increase the manufacturing cost of the display panel, and when an original control device (for example, PMIC) in the display panel is used as the compensation module, if the obtained analog output voltage is directly input into the control device, the control device needs to have a large number of pins, which can increase the design difficulty of the control device. When the compensation module consists of a voltage acquisition unit and a control output unit, and the voltage acquisition unit is in communication connection with the control output unit, all pixel driving circuits in the display panel can share one control output unit, so that the circuit design can be simplified, and the cost of the display panel can be prevented from being increased. Meanwhile, in the process of judging whether the organic light-emitting element has voltage decay according to the output voltage, judging whether the organic light-emitting element has voltage decay according to the decay output voltage and the conduction output voltage or judging whether the organic light-emitting element has voltage decay according to the decay output voltage, the acquisition of a large number of output voltages can be avoided, and whether the compensation voltage needs to be provided for the organic light-emitting element can be rapidly and accurately determined.
Optionally, the conduction control module is configured to receive a plurality of detection signals, and conduct the input end of the voltage acquisition unit with the first output end once when each detection signal is received; the interval between two adjacent detection signals is preset period duration; the voltage acquisition unit is used for acquiring one output voltage under the condition of being conducted with the first output end each time so as to acquire a plurality of output voltages and sending the acquired plurality of output voltages to the control output unit; the output terminal of the control output unit is connected with the first input terminal for providing the compensation voltage to the first input terminal in case it is determined that the organic light emitting element has voltage decay based on the plurality of output voltages.
In another embodiment, the on control module may control the input terminal of the voltage acquisition unit to be on with the first output terminal of the organic light emitting element at a plurality of continuous time points, the voltage acquisition unit may acquire output voltages at a plurality of time points, and send the acquired plurality of output voltages to the control output unit, and the control output unit may determine whether the organic light emitting diode has voltage degradation according to the plurality of output voltages. Referring to fig. 3, if the time taken for the voltage acquisition unit to acquire an output voltage is 5 seconds, the display driving chip may send a low-level signal to the control end of the connection switch tube 203 every 20 seconds after outputting the on signal to make the channel of the organic light emitting diode 201, where 20 seconds is a preset period duration, the preset period duration is longer than a preset detection duration, and the duration of the detection signal is, for example, 5 seconds of the preset detection duration, and may control the connection switch tube 203 to be turned on for 5 seconds, so that the input end of the voltage acquisition unit 2041 is controlled to be turned on with the cathode of the organic light emitting diode 201 for 5 seconds, and after continuously sending 10 low-level signals, the control output unit 2042 may obtain continuous 10 output voltages acquired by the voltage acquisition unit 2041. The control output unit 2042 may calculate and determine a falling rate of the output voltage according to 10 continuous output voltages, and determine that voltage degradation occurs at the cathode of the organic light emitting diode 201 when the falling rate is greater than a preset rate threshold.
The method for controlling the output unit to determine whether the voltage degradation occurs in the organic light emitting element according to the plurality of output voltages may include, but is not limited to, the above examples. Whether the voltage of the organic light-emitting element is reduced or not is judged according to the output voltages, so that whether the voltage of the organic light-emitting element is reduced or not can be accurately determined. Parameters such as a specific form of the detection signal, a preset detection duration, a preset period duration, and the number of output voltages can be specifically set according to requirements, which is not limited in this embodiment.
It should be noted that, the method for determining whether the voltage degradation occurs in the organic light emitting element based on the output voltage of the organic light emitting element may include, but is not limited to, the above examples. In practical application, the circuit structure of the conduction control module may be set according to a specific judging method, so that the compensation module may obtain one or more output voltages, and judge whether the voltage degradation occurs to the organic light emitting element according to the obtained output voltages.
Optionally, the voltage acquisition unit includes a third input terminal and a fourth input terminal; the conduction control module is used for conducting the third input end and the first output end under the condition that the first detection signal is received, and conducting the fourth input end and the first output end under the condition that the second detection signal is received; the first detection signal and the conduction signal are separated by a preset conduction time length, and the second detection signal and the conduction signal are separated by a preset decay time length; the preset decay time length is longer than the preset conduction time length; the voltage acquisition unit acquires the conduction output voltage of the organic light-emitting element under the condition that the third input end is conducted with the first output end, and acquires the declining output voltage of the organic light-emitting element under the condition that the second input end is conducted with the first output end; the voltage acquisition unit is also used for sending a conduction output voltage and a declining output voltage to the control output unit or sending a voltage difference value between the conduction output voltage and the declining output voltage to the control output unit; the output end of the control output unit is connected with the first input end and is used for providing compensation voltage for the first input end under the condition that the voltage difference value is larger than the voltage difference threshold value.
In one embodiment, the voltage acquisition unit may include a third input terminal and a fourth input terminal, and the conduction control module may control the third input terminal to be conducted with the first output terminal of the organic light emitting element at a first time point, so that the voltage acquisition unit acquires the conduction output voltage, and control the fourth input terminal to be conducted with the first output terminal of the organic light emitting element at a second time point, so that the voltage acquisition unit acquires the degradation output voltage. As shown in fig. 5, fig. 5 shows a schematic circuit diagram of another pixel driving circuit according to an embodiment of the present application, the on control module includes a first connection switch 2031 and a second connection switch 2032, the compensation module includes a voltage acquisition unit 2041 and a control output unit, and the control output unit includes a microcontroller 20421 and a voltage output module 20422. An input end of the first connection switch tube 2031 is connected with a cathode of the organic light emitting diode 201, and an output end of the first connection switch tube 2031 is connected with a third input end of the voltage acquisition unit 2041; the control end of the first connection switching tube 2031 controls the first connection switching tube 2031 to be turned on when receiving the first detection signal Gate1, so that the cathode of the organic light emitting diode 201 is turned on with the third input end of the voltage acquisition unit 2041; an input end of the second connection switch tube 2032 is connected with a cathode of the organic light emitting diode 201, and an output end of the second connection switch tube is connected with a fourth input end of the voltage acquisition unit 2041; the control terminal of the second connection switch 2032 controls the second connection switch 2032 to be turned on when receiving the second detection signal Gate2, so that the cathode of the organic light emitting diode 201 is turned on with the fourth input terminal of the voltage acquisition unit 2041. For an understanding of the first detection signal and the second detection signal, reference may be made to the above examples, and the description of this embodiment is omitted here.
The voltage collecting unit 2041 may include a subtractor, an analog-to-digital converter, and an energy storage element, where a first input end of the subtractor (i.e., a third input end of the voltage collecting unit) is connected to an output end of the first connection switching tube 2031, so that a conduction output voltage may be obtained, and the energy storage element may be disposed at the first input end of the subtractor, and after the conduction output voltage is obtained at the first time point, the conduction output voltage may be stored by the energy storage element. The second input terminal of the subtracter (i.e., the fourth input terminal of the voltage acquisition unit) is connected to the output terminal of the second connection switching tube 2032, so as to obtain a degraded output voltage. The output end of the subtracter is connected with the input end of the analog-to-digital converter, and after the subtracter acquires the declining output voltage, the subtracter can calculate the voltage difference between the declining output voltage and the conducting output voltage and output the voltage difference to the analog-to-digital converter. The analog-to-digital converter is in communication connection with the control output unit and can send the calculated voltage difference to the control output unit. Further, after receiving the voltage difference, the control output unit inputs the compensation voltage to the anode of the organic light emitting diode if the voltage difference is greater than the voltage difference threshold, otherwise, does not input the compensation voltage to the anode of the organic light emitting diode if the voltage difference is less than or equal to the voltage difference threshold.
Alternatively, the voltage acquisition unit may include only an analog-to-digital converter, where a first input end of the analog-to-digital converter (i.e., a third input end of the voltage acquisition unit) is connected to the output end of the first connection switching tube 2031, and a second input end of the analog-to-digital converter (i.e., a fourth input end of the voltage acquisition unit) is connected to the output end of the second connection switching tube 2032, and the analog-to-digital converter is connected to the control output unit in communication. After the first connection switching tube 2031 is turned on at a first time point, the analog-to-digital converter may obtain the on output voltage, and convert the on output voltage into a digital on output voltage and send the digital on output voltage to the control output unit. After the second connection switching tube 2032 is turned on at the second time point, the analog-to-digital converter may acquire the degraded output voltage, and transmit the degraded output voltage to the control output unit after converting the degraded output voltage into the degraded output voltage of digital quantity. The control output unit may calculate a voltage difference between the on output voltage and the off output voltage after receiving the on output voltage and the off output voltage, and input a compensation voltage to the anode of the organic light emitting diode when the comparison determination voltage difference is greater than the voltage difference threshold, or not input the compensation voltage to the anode of the organic light emitting diode when the calculation determination voltage difference is less than or equal to the voltage difference threshold.
In the embodiment of the invention, the voltage acquisition unit comprises two input ends which are respectively conducted with the output end of the organic light-emitting element at a first time point and a second time point so as to respectively acquire the conducted output voltage and the declined output voltage, thereby being capable of more accurately acquiring the conducted output voltage and the declined output voltage and avoiding inaccurate acquired conducted output voltage and declined output voltage from influencing the judgment result of the control output unit.
Optionally, the control output unit comprises a microcontroller and a voltage output module; the microcontroller is in communication connection with the voltage acquisition unit, and the output end of the microcontroller is connected with the voltage output module; the microcontroller is used for sending a compensation signal to the voltage output module under the condition that the voltage decay of the organic light-emitting element is determined based on the output voltage; the voltage output end of the voltage output module is connected with the first input end and is used for providing compensation voltage for the first input end under the condition of receiving the compensation signal.
In one embodiment, the control output unit may include a microcontroller (MicroGatentroller Unit, MCU) and a voltage output module, and when the voltage acquisition unit transmits a voltage difference between the decay output voltage and the on output voltage to the microcontroller or transmits the decay output voltage and the on output voltage to the microcontroller, the microcontroller may determine whether voltage decay occurs in the organic light emitting element according to the voltage difference, and transmit a compensation signal to the voltage output module if it is determined that the voltage decay occurs in the organic light emitting element. Or when the voltage acquisition unit only sends the declining output voltage to the microcontroller, the microcontroller can judge whether the voltage declining occurs to the organic light-emitting element according to the declining output voltage, and sends a compensation signal to the voltage output module under the condition that the voltage declining occurs to the organic light-emitting element is determined. As shown in fig. 5, the control output unit includes a microcontroller 20421 and a voltage output module 20422, and the microcontroller 20421 may be an MCU included in the display driving chip or may be an MCU independently provided. After receiving the voltage difference sent by the voltage acquisition unit 2041, if the voltage difference is greater than the voltage difference threshold, the microcontroller 20421 determines that the cathode of the organic light emitting diode has voltage degradation, and may send a compensation signal to the voltage output module 20422. Alternatively, the microcontroller 20421 may calculate a voltage difference between the on output voltage and the off output voltage after receiving the on output voltage and the off output voltage sent by the voltage acquisition unit 2041, and send a compensation signal to the voltage output module 20422 if the comparison determines that the voltage difference is greater than the voltage difference threshold. Referring to fig. 3, when the on control module includes the connection switch 203 shown in fig. 3, the voltage acquisition unit may only send a degradation output voltage to the microcontroller 20421, and after receiving the degradation output voltage, the microcontroller 20421 determines that the voltage degradation of the organic light emitting diode occurs if the comparison determines that the degradation output voltage is less than the degradation voltage threshold, and sends a compensation signal to the voltage output module 20422. As shown in fig. 3 and 5, the specific circuit structure of the on control module may be specifically set according to the circuit structure of the voltage acquisition unit and the number of output voltages to be acquired, and is not limited to the circuit structure shown in fig. 3 and 5.
In the embodiment of the invention, the control output unit can comprise a microcontroller and a voltage output module, and the voltage difference value and the voltage difference threshold value are compared by the microcontroller, so that the circuit design of the PMIC can be simplified.
Optionally, the voltage output module comprises a power management chip and a compensation switch tube; the compensation output end of the power management chip is connected with the input end of the compensation switch tube so as to provide compensation voltage for the input end of the compensation switch tube; the control output end of the power management chip is connected with the control end of the compensation switch tube and is used for sending a control signal to the compensation switch tube under the condition of receiving the compensation signal; the output end of the compensation switch tube is connected with the first input end and is used for conducting under the condition of receiving a control signal so as to transmit compensation voltage to the first input end.
Referring to fig. 4 and 5, the voltage output module 20422 may include a power management chip 204222 and a compensation switch 204221, where the compensation switch 204221 and the thin film transistor in the driving module 202 are the same type of thin film transistor. The input end of the compensation switch tube 204221 is connected with the compensation output end of the power management chip 204222, the output end of the compensation switch tube 204221 is an output end of the compensation module, the output end of the compensation switch tube is connected with the anode of the organic light emitting diode 201, and the control end of the compensation switch tube 204221 is connected with the control output end of the power management chip 204222. The microcontroller 20421 sends a compensation signal Gate3 to the power management chip 204222 in the event that it is determined from the voltage difference between the on output voltage and the degraded output voltage that the organic light emitting diode 201 is degraded. When receiving the compensation signal Gate3, the power management chip 204222 can output a low-level signal, i.e., a control signal, to the control terminal of the compensation switch tube 204221, so as to control the compensation switch tube 204221 to be turned on. At this time, the compensation output terminal of the power management chip 204222 is connected to the anode of the organic light emitting diode 201, and the compensation voltage Vem output from the power management chip 204222 can be input to the anode of the organic light emitting diode 201 through the compensation switching tube 204221.
In practice, the compensation switching tube 204221 can be disposed inside the power management chip 204222. Alternatively, the output terminal of the micro-controller 20421 is connected to the control terminal of the compensation switching tube 204221, the power management chip 204222 continuously outputs the compensation voltage, and when the micro-controller 20421 determines that the voltage of the organic light emitting diode 201 is degraded, the compensation signal Gate3 can be output to the control terminal of the compensation switching tube 204221, so as to control the compensation switching tube 204221 to be turned on, and the compensation voltage Vem is transferred to the anode of the organic light emitting diode 201. Specific circuit configurations of the voltage output module may include, but are not limited to, the examples described above.
In the embodiment of the invention, the voltage output module can be composed of the PMIC and the compensation switch tube, the PMIC can adopt the original PMIC in the display panel, the circuit design can be simplified, and other circuit structures are prevented from being added in the display panel.
Optionally, the compensation module comprises a subtracter, a comparator and a voltage output module; the conduction control module is used for conducting the fifth input end of the subtracter with the first output end under the condition that the first detection signal is received, and conducting the sixth input end of the subtracter with the first output end under the condition that the second detection signal is received; the first detection signal and the conduction signal are separated by a preset conduction time length, and the second detection signal and the conduction signal are separated by a preset decay time length; the preset decay time length is longer than the preset conduction time length; the output end of the subtracter is connected with the input end of the comparator, and is used for acquiring and storing the conduction output voltage of the organic light-emitting element under the condition that the fifth input end is conducted with the first output end, acquiring the declining output voltage of the organic light-emitting element under the condition that the sixth input end is conducted with the first output end, and outputting a voltage difference value between the conduction output voltage and the declining output voltage to the comparator; the output end of the comparator is connected with the voltage output module and is used for sending a compensation signal to the voltage output module when the voltage difference value is larger than the voltage difference threshold value; the voltage output end of the voltage output module is connected with the first input end and is used for providing compensation voltage for the first input end under the condition of receiving the compensation signal.
In one embodiment, the compensation module may include a subtractor, a comparator, and a voltage output module, where the subtractor is configured to obtain a conduction output voltage and a degradation output voltage of the organic light emitting element, calculate a voltage difference between the conduction output voltage and the degradation output voltage, and output the voltage difference to the comparator. The comparator is used for comparing the received voltage difference value with a voltage difference threshold value, and when the voltage difference value is larger than the voltage difference threshold value, the comparator determines that the voltage of the organic light-emitting element is declined, and sends a compensation signal to the voltage output module. As shown in fig. 6, fig. 6 shows a schematic circuit diagram of a pixel driving circuit according to another embodiment of the present application, wherein a compensation module includes a subtractor 2041, a comparator 2042, and a voltage output module 2043, and the voltage output module 2043 is the same as the voltage output module 20422 in fig. 5, and includes a power management chip 20431 and a compensation switch tube 20432; the conduction control module is the same as that in fig. 5, and includes a first connection switching tube 2031 and a second connection switching tube 2032. A fifth input terminal of the subtractor 2041 is connected to an output terminal of the first connection switching tube 2031, a sixth input terminal of the subtractor 2041 is connected to an output terminal of the second connection switching tube 2032, the first connection switching tube 2031 is turned on after receiving the first detection signal Gate1, and the fifth input terminal of the subtractor 2041 can obtain the on output voltage and store the on output voltage; the second connection switch 2032 is turned on after receiving the second detection signal Gate2, and the sixth input terminal of the subtractor 2041 may obtain a degraded output voltage. After the degraded output voltage is obtained, the subtractor 2041 may calculate a voltage difference between the on output voltage and the degraded output voltage. An output terminal of the subtractor 2041 is connected to a seventh input terminal of the comparator 2042, and a voltage difference threshold value Vc may be constantly input to an eighth input terminal of the comparator 2042, and the comparator 2042 compares the voltage difference value with the voltage difference threshold value Vc after receiving the voltage difference value output from the subtractor 2041. The output terminal of the comparator 2042 is connected to the input terminal of the power management chip 20431, and the comparator 2042 can send a compensation signal to the power management chip 20431 when the comparison determines that the voltage difference is greater than the voltage difference threshold Vc. A storage element may be provided at the fifth input of the subtractor 2041 to store the on output voltage obtained at the first time point at the fifth input. The energy storage element setting method may be set according to the requirement, which is not limited in this embodiment.
In the embodiment of the invention, when the compensation module consists of the subtracter, the comparator and the voltage output module, the circuit structure of the compensation module is relatively simple, the subtracter can respectively acquire the conduction output voltage and the decline output voltage, and whether the voltage decline of the organic light-emitting element occurs can be accurately determined according to the voltage difference value between the conduction output voltage and the decline output voltage.
Optionally, the compensation module comprises a comparator and a voltage output module; the conduction control module is connected with the input end of the comparator and used for conducting the input end of the comparator with the first output end under the condition that the second detection signal is received; the second detection signal and the conduction signal are separated by a preset decay time length; the output end of the comparator is connected with the input end of the voltage output module, and is used for acquiring the declining output voltage of the organic light-emitting element under the condition of being conducted with the first output end, and sending a compensation signal to the voltage output module under the condition that the declining output voltage is smaller than a declining voltage threshold value; the voltage output end of the voltage output module is connected with the first input end and is used for providing compensation voltage for the first input end under the condition of receiving the compensation signal.
In one embodiment, the compensation module may include a comparator and a voltage output module, where the comparator may obtain the degraded output voltage of the organic light emitting element at a second time point after the organic light emitting element is turned on, and send a compensation signal to the voltage output module if the comparison determines that the degraded output voltage is less than the degraded voltage threshold. As shown in fig. 7, fig. 7 shows a schematic circuit diagram of a pixel driving circuit according to another embodiment of the present application, the compensation module includes a comparator 2041 and a voltage output module 2042, the voltage output module 2042 is the same as the voltage output module 20422 in fig. 5, and includes a power management chip 20421 and a compensation switch tube 20422, a seventh input end of the comparator 2041 is connected to an output end of the connection switch tube 203, and an input end of the connection switch tube 203 is connected to a cathode of the organic light emitting diode 201. The display driving chip may send a second detection signal to the control terminal of the connection switching tube 203 at a second time point after the organic light emitting diode is turned on, so as to control the connection switching tube 203 to be turned on. At this time, the seventh input terminal of the comparator 2041 is connected to the cathode of the organic light emitting diode 201, so that the degraded output voltage of the organic light emitting diode 201 can be obtained. The eighth input terminal of the comparator 2041 may constantly input the degradation voltage threshold Vt, and the comparator 2041 determines that the cathode of the organic light emitting diode 201 experiences voltage degradation when comparing and determining that the obtained degradation output voltage is smaller than the degradation voltage threshold Vt, and sends a compensation signal to the power management chip 20421.
In the embodiment of the invention, the compensation module consists of the comparator and the voltage output module, and the circuit structure of the comparator is simple, the occupied area is small, the circuit design can be obviously simplified, and the area of the display panel is prevented from being increased.
In this embodiment, the display driving chip in the display panel may send a turn-on signal and a detection signal to the pixel driving circuit in the detection stage, and control the turn-on control module and the compensation module to act, so that the compensation module determines whether the voltage degradation occurs in the organic light emitting element in the pixel driving circuit, and starts to provide the compensation voltage to the organic light emitting element when it is determined that the voltage degradation occurs in the organic light emitting element. In the normal use stage of the display panel, the conduction control module does not act, and the compensation module continuously provides compensation voltage for the organic light-emitting element. In combination with the above example, when the compensation module includes a PMIC, the PMIC may record the received compensation signal or the comparison result after comparing and determining that the compensation voltage needs to be provided to the organic light emitting diode or after receiving the compensation signal, and the MCU may start inputting the compensation voltage to the anode of the organic light emitting diode according to the recorded compensation signal or the comparison result after each power-up during a normal use period of the display panel. Or when the compensation module comprises the MCU, the MCU can record the comparison result when the MCU determines that the compensation voltage needs to be provided for the organic light emitting diode, and can send a compensation signal to the PMIC after each power-on, so that the PMIC provides the compensation voltage for the anode of the organic light emitting diode. The magnitude of the compensation voltage can be specifically set according to the requirement, and the embodiment is not limited thereto.
In summary, in the embodiment of the present invention, the pixel driving circuit includes an organic light emitting element, a driving module, a conduction control module and a compensation module, the driving module is connected to a first input terminal of the organic light emitting element, and a first output terminal of the organic light emitting element is connected to a common electrode terminal of the pixel driving circuit; the driving module is used for providing pixel voltage for the first input end under the condition of receiving the conduction signal so as to conduct and emit light of the organic light-emitting element; one end of the conduction control module is connected with the first output end, and the other end of the conduction control module is connected with the second input end of the compensation module and is used for conducting the second input end of the compensation module with the first output end under the condition of receiving the detection signal; and when the detection signal is received, no voltage is input to the common electrode terminal; the detection signal is after the turn-on signal; the second output end of the compensation module is connected with the first input end and is used for acquiring the output voltage of the organic light-emitting element and providing the compensation voltage to the first input end under the condition that the voltage degradation of the organic light-emitting element is determined based on the output voltage. When judging that the voltage of the organic light-emitting element is declined, the compensation module provides compensation voltage for the input end of the organic light-emitting element, and can improve the on current of the organic light-emitting element when the brightness of the organic light-emitting element is reduced, so that the brightness of the organic light-emitting element can be improved, the brightness uniformity of a plurality of organic light-emitting elements in the display panel is maintained, and the problem of uneven brightness of the display panel can be avoided.
Referring to fig. 8, fig. 8 shows a step flowchart of a voltage compensation method according to an embodiment of the present application, where the method includes:
step 801, controlling the organic light emitting element to conduct and emit light.
Step 802, after the organic light emitting element is turned on to emit light, controlling the common electrode terminal connected to the first output terminal of the organic light emitting element to have no voltage input, and obtaining the output voltage of the organic light emitting element.
Step 803, providing a compensation voltage to a first input terminal of the organic light emitting element in case it is determined that the organic light emitting element has a voltage decay based on the output voltage.
In this embodiment, the voltage compensation method may be implemented by a display driving chip in a display panel, and fig. 9 shows a flow chart of the voltage compensation method according to an embodiment of the present application, and in combination with fig. 5, the display driving chip may first send a conducting signal to the driving module in the detection stage, so as to control the driving module to input a pixel voltage to the anode of the organic light emitting diode, so that the organic light emitting diode is conducted and emits light. After the organic light emitting diode is turned on to emit light, the display driving chip may transmit an indication signal to the PMIC, instructing the PMIC to stop outputting the power supply negative voltage to the common electrode terminal, so that the common electrode terminal has no voltage input. Further, at the first time point, the display driving chip can input a first detection signal to the control end of the first connection switching tube to enable the first connection switching tube to be conducted, so that the voltage acquisition unit can acquire the conducted output voltage. At a second time point, the display driving chip can input a second detection signal to the control end of the second connection switching tube to enable the second connection switching tube to be conducted, and therefore the voltage acquisition unit can acquire declining output voltage. The voltage acquisition unit sends a conduction output voltage and a decay output voltage or sends a voltage difference value between the conduction output voltage and the decay output voltage to an MCU in the display driving chip. When the MCU determines that the voltage difference is greater than the voltage difference threshold, the MCU sends a compensation signal to the PMIC in the display driving chip, so that the PMIC starts to provide compensation voltage for the anode of the organic light emitting diode, otherwise, the MCU does not send the compensation signal to the PMIC, and the PMIC does not provide compensation voltage for the anode of the organic light emitting diode.
Optionally, step 802 may include: acquiring a conduction output voltage of the organic light emitting element at a first time point, and acquiring a decay output voltage of the organic light emitting element at a second time point; the first time point is spaced from the on time point of the organic light emitting element by a preset on time period, and the second time point is spaced from the on time point of the organic light emitting element by a preset decay time period. Accordingly, step 803 may include: and providing a compensation voltage to the first input terminal of the organic light emitting element in case that a voltage difference between the on output voltage and the decay output voltage is greater than a voltage difference threshold.
Optionally, step 802 may include: and obtaining the declining output voltage of the organic light-emitting element at a second time point. Accordingly, step 803 may include: providing a compensation voltage to a first input terminal of the organic light emitting element under the condition that the decay output voltage is smaller than a decay voltage threshold; the second time point is spaced from the on time point of the organic light emitting element by a preset decay time period.
For an understanding of the voltage compensation method, reference may be made to the pixel driving circuit in the above example, and this embodiment is not described herein.
The embodiment of the application also provides a display panel which comprises the pixel driving circuit in the example.
Referring to fig. 10, fig. 10 shows a schematic structural diagram of an electronic device according to an embodiment of the present application, where the electronic device 1000 may include a display panel 1001, and the electronic device may be an electronic device having a display panel, such as a mobile phone, a notebook computer, and a television. Among other things, the electronic device 1000 may include, but is not limited to: the system comprises a radio frequency unit, a network module, an audio output unit, an input unit, a sensor, a display unit, a user input unit, an interface unit, a memory, a processor and the like.
It should be noted that the terms "first," "second," and the like in the description and in the claims are used for distinguishing between similar objects and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used may be interchanged where appropriate such that embodiments of the application may be practiced otherwise than as specifically illustrated or described herein. Furthermore, in the description and claims, "and/or" means at least one of the connected objects, and the character "/", generally means that the associated object is an "or" relationship.
The embodiments of the present application have been described above with reference to the accompanying drawings, but the present application is not limited to the above-described embodiments, which are merely illustrative and not restrictive, and many forms may be made by those having ordinary skill in the art without departing from the spirit of the present application and the scope of the claims, which are to be protected by the present application.

Claims (10)

1. A pixel driving circuit, comprising: the organic light-emitting device comprises an organic light-emitting element, a driving module, a conduction control module and a compensation module;
the driving module is connected with a first input end of the organic light-emitting element, and a first output end of the organic light-emitting element is connected with a common electrode end of the pixel driving circuit; the driving module is used for providing pixel voltage for the first input end under the condition of receiving a conduction signal so as to conduct and emit light of the organic light-emitting element;
one end of the conduction control module is connected with the first output end, and the other end of the conduction control module is connected with the second input end of the compensation module and is used for conducting the second input end of the compensation module with the first output end under the condition of receiving a detection signal; and when the detection signal is received, no voltage is input to the common electrode terminal; the detection signal is after the conduction signal;
the second output end of the compensation module is connected with the first input end and is used for acquiring the output voltage of the organic light-emitting element and providing compensation voltage for the first input end under the condition that the voltage degradation of the organic light-emitting element is determined based on the output voltage;
The compensation module comprises a voltage acquisition unit and a control output unit;
the input end of the voltage acquisition unit is connected with the conduction control module, and the voltage acquisition unit is connected with the control output unit in a communication way; the voltage acquisition unit is used for acquiring the output voltage and sending the output voltage to the control output unit under the condition of being conducted with the first output end;
the output end of the control output unit is connected with the first input end and is used for providing the compensation voltage for the first input end under the condition that the voltage degradation of the organic light-emitting element is determined based on the output voltage;
the voltage acquisition unit comprises a third input end and a fourth input end;
the conduction control module is used for conducting the third input end and the first output end under the condition that a first detection signal is received, and conducting the fourth input end and the first output end under the condition that a second detection signal is received; the first detection signal and the conduction signal are separated by a preset conduction time length, and the second detection signal and the conduction signal are separated by a preset decay time length; the preset decay time length is longer than the preset conduction time length;
The voltage acquisition unit acquires a conduction output voltage of the organic light emitting element under the condition that the third input end is conducted with the first output end, and acquires a declining output voltage of the organic light emitting element under the condition that the fourth input end is conducted with the first output end; the voltage acquisition unit is further used for sending the conduction output voltage and the decline output voltage to the control output unit or sending a voltage difference value between the conduction output voltage and the decline output voltage to the control output unit;
the output end of the control output unit is connected with the first input end and is used for providing the compensation voltage for the first input end under the condition that the voltage difference value is larger than a voltage difference threshold value.
2. The pixel driving circuit according to claim 1, wherein,
the conduction control module is used for conducting the input end of the voltage acquisition unit and the first output end for the first time under the condition of receiving a first detection signal, and conducting the input end of the voltage acquisition unit and the first output end for the second time under the condition of receiving a second detection signal; the first detection signal and the conduction signal are separated by a preset conduction time length, and the second detection signal and the conduction signal are separated by a preset decay time length; the preset decay time length is longer than the preset conduction time length;
The voltage acquisition unit is used for acquiring the conduction output voltage of the organic light-emitting element under the condition of being conducted with the first output end for the first time and acquiring the declining output voltage of the organic light-emitting element under the condition of being conducted with the first output end for the second time; the voltage acquisition unit is further used for sending the conduction output voltage and the decline output voltage to the control output unit or sending a voltage difference value between the conduction output voltage and the decline output voltage to the control output unit;
the output end of the control output unit is connected with the first input end and is used for providing the compensation voltage for the first input end under the condition that the voltage difference value is larger than a voltage difference threshold value.
3. The pixel driving circuit according to claim 1, wherein,
the conduction control module is used for receiving a plurality of detection signals and conducting the input end of the voltage acquisition unit and the first output end once under the condition that each detection signal is received; a preset period duration is arranged between two adjacent detection signals;
the voltage acquisition unit is used for acquiring one output voltage under the condition of being conducted with the first output end each time so as to acquire a plurality of output voltages, and sending the acquired plurality of output voltages to the control output unit;
The output terminal of the control output unit is connected with the first input terminal, and is used for providing the compensation voltage to the first input terminal when the voltage degradation of the organic light emitting element is determined based on a plurality of output voltages.
4. The pixel driving circuit according to claim 1, wherein,
the conduction control module is used for conducting the input end of the voltage acquisition unit with the first output end under the condition that a second detection signal is received; the second detection signal and the conduction signal are separated by a preset decay time length;
the voltage acquisition unit acquires the declining output voltage of the organic light-emitting element under the condition of being conducted with the first output end, and sends the declining output voltage to the control output unit;
the output end of the control output unit is connected with the first input end and is used for providing the compensation voltage for the first input end under the condition that the declining output voltage is smaller than a declining voltage threshold value.
5. The pixel driving circuit according to claim 1, wherein the control output unit comprises a microcontroller and a voltage output module;
The microcontroller is in communication connection with the voltage acquisition unit, and the output end of the microcontroller is connected with the voltage output module; the microcontroller is used for sending a compensation signal to the voltage output module under the condition that the voltage decay of the organic light-emitting element is determined based on the output voltage;
the voltage output end of the voltage output module is connected with the first input end and is used for providing the compensation voltage for the first input end under the condition that the compensation signal is received.
6. The pixel driving circuit according to claim 1, wherein the compensation module comprises a subtractor, a comparator, and a voltage output module;
the conduction control module is used for conducting the fifth input end of the subtracter with the first output end under the condition that a first detection signal is received, and conducting the sixth input end of the subtracter with the first output end under the condition that a second detection signal is received; the first detection signal and the conduction signal are separated by a preset conduction time length, and the second detection signal and the conduction signal are separated by a preset decay time length; the preset decay time length is longer than the preset conduction time length;
The output end of the subtracter is connected with the input end of the comparator, and is used for acquiring and storing the conduction output voltage of the organic light-emitting element under the condition that the fifth input end is conducted with the first output end, acquiring the declining output voltage of the organic light-emitting element under the condition that the sixth input end is conducted with the first output end, and outputting a voltage difference value between the conduction output voltage and the declining output voltage to the comparator;
the output end of the comparator is connected with the voltage output module and is used for sending a compensation signal to the voltage output module when the voltage difference value is larger than a voltage difference threshold value;
the voltage output end of the voltage output module is connected with the first input end and is used for providing the compensation voltage for the first input end under the condition that the compensation signal is received.
7. The pixel driving circuit according to claim 1, wherein the compensation module comprises a comparator and a voltage output module;
the conduction control module is connected with the input end of the comparator and is used for conducting the input end of the comparator with the first output end under the condition that a second detection signal is received; the second detection signal and the conduction signal are separated by a preset decay time length;
The output end of the comparator is connected with the input end of the voltage output module, and is used for acquiring the declining output voltage of the organic light-emitting element under the condition that the comparator is conducted with the first output end, and sending a compensation signal to the voltage output module under the condition that the declining output voltage is smaller than a declining voltage threshold value;
the voltage output end of the voltage output module is connected with the first input end and is used for providing the compensation voltage for the first input end under the condition that the compensation signal is received.
8. The pixel driving circuit according to any one of claims 5 to 7, wherein the voltage output module comprises a power management chip and a compensation switching tube;
the compensation output end of the power management chip is connected with the input end of the compensation switch tube so as to provide compensation voltage for the input end of the compensation switch tube; the control output end of the power management chip is connected with the control end of the compensation switch tube and is used for sending a control signal to the compensation switch tube under the condition of receiving the compensation signal;
the output end of the compensation switch tube is connected with the first input end and is used for being conducted under the condition that the control signal is received, so that the compensation voltage is transmitted to the first input end.
9. A display panel comprising a pixel driving circuit according to any one of claims 1-8.
10. An electronic device comprising the display panel of claim 9.
CN202210501669.3A 2022-05-09 2022-05-09 Pixel driving circuit, display panel and electronic equipment Active CN114842804B (en)

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