CN117012152B - Pixel driving circuit and display device - Google Patents
Pixel driving circuit and display device Download PDFInfo
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- CN117012152B CN117012152B CN202311129734.5A CN202311129734A CN117012152B CN 117012152 B CN117012152 B CN 117012152B CN 202311129734 A CN202311129734 A CN 202311129734A CN 117012152 B CN117012152 B CN 117012152B
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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
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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
- G09G3/3258—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 voltage across the light-emitting element
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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
- G09G2310/00—Command of the display device
- G09G2310/02—Addressing, scanning or driving the display screen or processing steps related thereto
- G09G2310/0264—Details of driving circuits
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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
- G09G2320/00—Control of display operating conditions
- G09G2320/02—Improving the quality of display appearance
- G09G2320/0257—Reduction of after-image effects
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Abstract
The application relates to a pixel driving circuit and a display device. The circuit comprises: the driving transistor, the first switching transistor, the second switching transistor, the third switching transistor, the fourth switching transistor, the fifth switching transistor, the sixth switching transistor, the first storage capacitor, the second storage capacitor and the alternating current light emitting device. The pixel driving circuit utilizes specific sequential logic, the alternating current control signal line provides voltage for the pixel driving circuit, has good improvement effect on reducing the voltage drop of the power supply voltage, improves the ageing and the direct current bias voltage of the device through the alternating current light emitting device, can effectively improve the problem of afterimage, and solves the technical problem of afterimage of pictures caused by unstable driving devices.
Description
Technical Field
The present application relates to the field of OLED display technologies, and in particular, to a pixel driving circuit and a display device.
Background
AMOLED (Active-matrix organic light-emitting diode) is one of the most potential display technologies because of its self-luminescence, low power consumption, wide viewing angle, high color gamut, high contrast, fast response, etc. To achieve precise AMOLED control, TFT (Thin Film Transistor ) technology is required to perform pixel driving, and currently, the main TFT technologies mainly include α -si TFT technology, LTPS TFT technology, oxide TFT technology, and α -si technology is not suitable for AMOLED driving due to the defects of poor stability and low carrier mobility, and LTPS is considered to be the TFT technology most suitable for AMOLED driving due to the best stable row and highest carrier mobility among the three. However, LTPS technology has limited its use in mass production because of relatively complex processes and poor uniformity for large-scale applications. In general, the brightness of an OLED light emitting device is mainly determined by the magnitude of the driving current, and the greater the current, the greater the brightness, so the OLED device has a high requirement on the stability of the driving device. However, most of the current OLED driving circuits are driven by a dc power supply, and a separate power line provides a dc voltage for each pixel, so that the OLED light emitting device is driven by a dc bias voltage, and the driving device is very unstable along with the extension of the product service time and the overlong display time of a fixed picture, which may cause the problem of afterimage.
Aiming at the problem of image sticking caused by unstable driving devices, no effective solution is proposed at present.
Disclosure of Invention
The application provides a pixel driving circuit and a display device, which are used for solving the technical problem that an image is left after a picture due to unstable driving devices.
According to an aspect of an embodiment of the present application, there is provided a pixel driving circuit including a driving transistor, a first switching transistor, a second switching transistor, a third switching transistor, a fourth switching transistor, a fifth switching transistor, a sixth switching transistor, a first storage capacitor, a second storage capacitor, and an ac light emitting device; wherein: the first end of the driving transistor is connected with a first power supply control line, and the second end of the driving transistor is connected with the first end of the first switch transistor; the control end of the first switch transistor is connected with a setting control line, and the second end of the first switch transistor is connected with one end of the alternating current light emitting device; the other end of the alternating current light-emitting device is connected with a second power supply control line; the control end of the second switching transistor is connected with the first power supply control line, the first end of the second switching transistor is connected with one end of the first storage capacitor, and the second end of the second switching transistor is connected with the first end of the first switching transistor; the control end of the third switching transistor is connected with the second power supply control line, the first end of the third switching transistor is connected with the first power supply control line, and the second end of the third switching transistor is connected with one end of the first storage capacitor; the other end of the first storage capacitor is connected with the second end of the fourth switching transistor; the control end of the fourth switching transistor is connected with the setting control line, and the first end of the fourth switching transistor is connected with the control end of the driving transistor; the second storage capacitor is connected with the fourth switching transistor in parallel; the control end of the fifth switching transistor is connected with the scanning control line, the first end of the fifth switching transistor is connected with the data line, and the second end of the fifth switching transistor is connected with the control end of the driving transistor; the second end of the sixth switching transistor is connected with the reference power supply line, the control end of the sixth switching transistor is connected with the reference power supply control line, and the first end of the sixth switching transistor is connected with the second end of the fourth switching transistor.
Optionally, the first power control line and the second power control line are connected to an ac power source.
Optionally, the ac light emitting device includes a first light emitting diode and a second light emitting diode, where an anode of the first light emitting diode is connected to the second end of the first switching transistor, a cathode of the first light emitting diode is connected to the second power control line, an anode of the second light emitting diode is connected to the second power control line, and a cathode of the second light emitting diode is connected to the second end of the first switching transistor.
Optionally, the pixel driving circuit has a first operation mode, where the first operation mode is used to make the first light emitting diode and the second light emitting diode emit light alternately in the same display frame, and each operation period of the pixel driving circuit includes a scanning phase, a compensation phase, a first light emitting phase, and a second light emitting phase in the first operation mode.
Optionally, the pixel driving circuit has a second operation mode, where the second operation mode is used to make the first light emitting diode and the second light emitting diode emit light alternately between adjacent display frames, and in the second operation mode, a first operation period of the pixel driving circuit includes the scanning phase, the compensation phase and the first light emitting phase, and a second operation period of the pixel driving circuit includes the scanning phase, the compensation phase and the second light emitting phase, where the first operation period and the second operation period are two adjacent operation periods.
Optionally, in the scanning stage, the first power control line and the setting control line are used for outputting a high level, so that the first switching transistor, the second switching transistor and the fourth switching transistor are turned off, the second power control line and the reference power control line are used for outputting a low level, so that the third switching transistor and the sixth switching transistor are turned on, and the scanning control line is used for scanning the pixel unit line by line to control the switching state of the fifth switching transistor.
Optionally, in the compensation phase, the first power supply control line is used for outputting a low level, the second power supply control line is used for outputting a high level, the scan control line is used for outputting a high level, the first switch transistor, the third switch transistor, the fourth switch transistor and the fifth switch transistor are turned off, and the second switch transistor and the sixth switch transistor are turned on.
Optionally, in the first light emitting stage, the first power control line is used for outputting a low level, the second power control line is used for outputting a high level, the reference power control line is used for pulling up the control terminal voltage of the sixth switching transistor to enable the sixth switching transistor to be turned off, the setting control line is used for pulling down the control terminal voltages of the first switching transistor and the fourth switching transistor to enable the first switching transistor and the fourth switching transistor to be turned on, the first light emitting diode is turned off, and the second light emitting diode is turned on.
Optionally, in the second light emitting stage, the first power control line is used for outputting a high level, the second power control line is used for outputting a low level, so that the first light emitting diode is turned on, and the second light emitting diode is turned off.
According to another aspect of the embodiments of the present application, there is provided a display device including a substrate having the pixel driving circuit as set forth in any one of the above.
Compared with the related art, the technical scheme provided by the embodiment of the application has the following advantages:
The application provides a pixel driving circuit which comprises a driving transistor, a first switching transistor, a second switching transistor, a third switching transistor, a fourth switching transistor, a fifth switching transistor, a sixth switching transistor, a first storage capacitor, a second storage capacitor and an alternating current light emitting device. The pixel driving circuit utilizes specific sequential logic, the alternating current control signal line provides voltage for the pixel driving circuit, has good improvement effect on reducing the voltage drop of the power supply voltage, improves the ageing and the direct current bias voltage of the device through the alternating current light emitting device, can effectively improve the problem of afterimage, and solves the technical problem of afterimage of pictures caused by unstable driving devices.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the application and together with the description, serve to explain the principles of the application.
In order to more clearly illustrate the embodiments of the present application or the technical solutions in the related art, the drawings that are required to be used in the embodiments or the related technical descriptions will be briefly described, and it will be apparent to those skilled in the art that other drawings can be obtained according to these drawings without inventive effort.
Fig. 1 is a schematic diagram of an alternative pixel driving circuit according to an embodiment of the application;
FIG. 2 is a schematic diagram of an alternative duty cycle provided in accordance with an embodiment of the present application;
FIG. 3 is a timing diagram illustrating operation of an alternative pixel driving circuit according to an embodiment of the present application;
FIG. 4 is a schematic diagram of another alternative duty cycle provided in accordance with an embodiment of the present application;
FIG. 5 is a timing diagram illustrating operation of an alternative pixel driving circuit according to an embodiment of the application;
Fig. 6 is a schematic structural diagram of an alternative display device according to an embodiment of the present application.
Reference numerals: m1, a driving transistor; m2, a first switching transistor; m3, a second switching transistor; m4, a third switching transistor; m5, fourth switching transistor; m6, a fifth switching transistor; m7, sixth switching transistors; c1, a first storage capacitor; c2, a second storage capacitor; VP1, a first power supply control line; VP2, a second power supply control line; SEL, setting a control line; SCAN, SCAN control line; VREF, reference power line; SREF, reference power supply control line; vdata, data line; d1, a first light emitting diode; d2, a second light emitting diode; 100. a substrate; 200. and a pixel driving circuit.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present application more apparent, the technical solutions of the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application, and it is apparent that the described embodiments are some embodiments of the present application, but not all embodiments of the present application. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.
In the following description, suffixes such as "module", "component", or "unit" for representing elements are used only for facilitating the description of the present application, and are not of specific significance per se. Thus, "module" and "component" may be used in combination.
In the related art, a general OLED pixel driving circuit is composed of two transistors, one of which controls the switching of a scan line, and one of which is a driving TFT of a light emitting device, and a storage capacitor for maintaining the driving TFT on. Wherein the OLED drive current IOLED can be expressed as:
Where μ is carrier mobility, W is channel width, L is channel length, CGI is control terminal capacitance, vth is threshold voltage, vgs=vdata-VDD, vdata is data voltage input to the driving TFT, VDD is power supply voltage, W, L is fixed at design time, CGI depends on control terminal insulating layer thickness and material. As can be seen from the above, the factors affecting the driving current and the light emitting brightness of the OLED device include carrier mobility μ, threshold voltage Vth, VDD and Vdata, wherein the carrier mobility μ and the threshold voltage Vth are key parameters for measuring the performance of the TFT device. In practical applications, the threshold voltage has non-uniformity problem and drift with the increase of working time, resulting in Mura with uneven brightness of the display panel. In addition, the power line has a certain degree of internal resistance R, the VDD voltage actually transmitted to the OLED device is Vdd-IOLED x R, the voltage drop of the power supply voltage is also a cause of uneven brightness of the OLED display device, and the light-emitting device of the driving circuit is always in a forward bias state, so that the aging of the device is accelerated.
In order to solve the problems mentioned in the background art, according to an aspect of the embodiments of the present application, there is provided an embodiment of a pixel driving circuit. As shown in fig. 1, the pixel driving circuit includes a driving transistor M1, a first switching transistor M2, a second switching transistor M3, a third switching transistor M4, a fourth switching transistor M5, a fifth switching transistor M6, a sixth switching transistor M7, a first storage capacitor C1, a second storage capacitor C2, and an ac light emitting device; wherein:
a first end of the driving transistor M1 is connected to the first power control line VP1, and a second end of the driving transistor M1 is connected to a first end of the first switching transistor M2;
The control end of the first switching transistor M2 is connected with a setting control line SEL, and the second end of the first switching transistor M2 is connected with one end of the alternating current light emitting device;
the other end of the alternating current light-emitting device is connected with a second power supply control line VP 2;
The control end of the second switching transistor M3 is connected with the first power supply control line VP1, the first end of the second switching transistor M3 is connected with one end of the first storage capacitor C1, and the second end of the second switching transistor M3 is connected with the first end of the first switching transistor M2;
The control end of the third switching transistor M4 is connected with the second power supply control line VP2, the first end of the third switching transistor M4 is connected with the first power supply control line VP1, and the second end of the third switching transistor M4 is connected with one end of the first storage capacitor C1;
The other end of the first storage capacitor C1 is connected with the second end of the fourth switching transistor M5;
the control end of the fourth switching transistor M5 is connected with the setting control line SEL, and the first end of the fourth switching transistor M5 is connected with the control end of the driving transistor M1;
The second storage capacitor C2 is connected with the fourth switching transistor M5 in parallel;
the control end of the fifth switching transistor M6 is connected with the scanning control line SCAN, the first end of the fifth switching transistor M6 is connected with the data line Vdata, and the second end of the fifth switching transistor M6 is connected with the control end of the driving transistor M1;
The second terminal of the sixth switching transistor M7 is connected to the reference power supply line VREF, the control terminal of the sixth switching transistor M7 is connected to the reference power supply control line SREF, and the first terminal of the sixth switching transistor M7 is connected to the second terminal of the fourth switching transistor M5.
In the embodiment of the application, the pixel driving circuit is composed of 6 switching TFT tubes, 1 driving TFT tube, 2 storage capacitors and an alternating current OLED (formed by reverse connection of two OLED polarities), wherein M2-M7 are P-type switching TFT tubes, and M1 is a driving TFT tube for driving the light emitting device. The signal network is composed of a Source Data Line (Vdata), two power supply control lines VP1 and VP2, a reference power supply Line VREF, a SCAN control Line SCAN, a reference power supply control Line SREF and a setting control Line SEL.
In an alternative embodiment, the first power control line VP1 and the second power control line VP2 are connected to an ac power source.
The application improves the scheme of using the direct current power supply to drive in the prior art to provide voltage for the pixel driving circuit by using the alternating current control signal, can effectively reduce the voltage drop of the power supply voltage, and further avoids uneven brightness of the display device.
In an alternative embodiment, the ac light emitting device includes a first light emitting diode D1 and a second light emitting diode D2, the anode of the first light emitting diode D1 is connected to the second terminal of the first switching transistor M2, the cathode of the first light emitting diode D1 is connected to the second power control line VP2, the anode of the second light emitting diode D2 is connected to the second power control line VP2, and the cathode of the second light emitting diode D2 is connected to the second terminal of the first switching transistor M2.
In the embodiment of the application, the front and back light emitting diodes are used for alternately working in one sub-pixel, so that the ageing and direct current bias voltage of the device are improved, and the problem of afterimage can be effectively solved.
In the prior art, an OLED driving circuit is driven by a direct current power supply, a single power line is used for providing direct current voltage for each pixel, and under the drive of direct current bias voltage, the OLED light-emitting device can cause the problem of afterimage along with the extension of the service time of a product and the overlong display time of a fixed picture. In addition, the power line has a certain degree of internal resistance R, the VDD voltage actually transmitted to the OLED device is Vdd-IOLED x R, the voltage drop of the power supply voltage is also a cause of uneven brightness of the OLED display device, and the light-emitting device of the driving circuit is always in a forward bias state, so that the aging of the device is accelerated.
The application provides a pixel driving circuit, which utilizes specific sequential logic, an alternating current control signal line provides voltage for the pixel driving circuit, has good improvement effect on reducing the voltage drop of a power supply voltage, improves the aging and direct current bias voltage of a device through an alternating current light emitting device, can effectively improve the problem of afterimage, solves the technical problem of afterimage of a picture caused by unstable driving device, and has compensation function on threshold voltage Vth drift, reduces the influence of threshold voltage on driving current and enhances OLED display uniformity.
The specific sequential logic of the pixel driving circuit is described below.
In an alternative embodiment, the pixel driving circuit has a first operation mode for alternately emitting light of the first light emitting diode D1 and the second light emitting diode D2 within the same display frame, as shown in fig. 2, and in the first operation mode, each operation cycle of the pixel driving circuit includes a scan phase T1, a compensation phase T2, a first light emitting phase T3, and a second light emitting phase T4. Fig. 3 shows an operation timing of the pixel driving circuit corresponding to the first operation mode, and the first operation mode is described below based on fig. 1 and 3.
When entering the current display Frame (N Frame):
In the SCAN stage T1, the first power control line VP1 and the setting control line SEL are used for outputting a high level, so that the first switching transistor M2, the second switching transistor M3 and the fourth switching transistor M5 are turned off, the second power control line VP2 and the reference power control line SREF are used for outputting a low level, the third switching transistor M4 and the sixth switching transistor M7 are turned on, and the SCAN control line SCAN is used for scanning the pixel unit row by row to control the switching state of the fifth switching transistor M6, i.e., the fifth switching transistor M6 of the corresponding row is turned on when scanning the fifth switching transistor M6 of the corresponding row, and the fifth switching transistor M6 of the row is turned off during the rest of the SCAN stage.
In the embodiment of the application, in the scanning stage, the driving scheme adopts the scheme of synchronous driving and synchronous compensation, so that the duty ratio of program control time in display time can be reduced, the power line VP1 and the control line SEL are high level, M2, M3 and M5 are closed, VP2 and SREF are low level, M4 and M7 are opened, the scanning line SCAN is controlled to SCAN line by line, the low level is kept for a period of time, M6 is opened, the point A voltage VA=Vdata, the point C voltage is charged to VDD through M4, the point D voltage is charged to VREF through M7, the point B voltage can be initialized to the high level of VP1 due to the low level of Vdata, the voltage of the capacitor C2 is set to VDD, the voltage of the capacitor C1 is VC 1=VD-VC=VREF-VDD, and no current passes through the OLED due to the fact that the point M2 is closed in the stage.
In the compensation phase T2, the first power control line VP1 is used for outputting a low level, the second power control line VP2 is used for outputting a high level, the control line SEL is used for outputting a high level, the SCAN control line SCAN is used for outputting a high level, and the first, third, fourth and fifth switching transistors M2, M4, M5 and M6 are turned off, and the second and sixth switching transistors M3 and M7 are turned on.
In the embodiment of the present application, in the compensation phase, VP1 is switched to low level, VP2 is switched to high level, SCAN is completed, and the high level is maintained, then M2, M4, M5, M6 are turned off, M3 and M7 are turned on, vd=vref, VA is maintained at Vdata, point B discharges through the first storage capacitor C1 until reaching the equilibrium state vb=vdata+|vth 1| (VTH 1 is the threshold voltage of M1), vb=vc, vc1=vref-Vdata- |vth1|, and since M2 is turned off in this phase, OLED has no current passing.
In the first light emitting stage T3, the first power control line VP1 is used for outputting a low level, the second power control line VP2 is used for outputting a high level, the reference power control line SREF is used for pulling up the control terminal voltage of the sixth switching transistor M7, so that the sixth switching transistor M7 is turned off, the control line SEL is set for pulling down the control terminal voltages of the first switching transistor M2 and the fourth switching transistor M5, so that the first light emitting diode D1 is turned off, and the second light emitting diode D2 is turned on.
In the embodiment of the application, in the first light-emitting stage, SREF is pulled high, M7 is turned off, SEL is pulled low, M2 and M5 are turned on, and since VP2 is high level and VP1 is low level, D1 is in a cut-off state, D2 is turned on, driving current flows through the OLED device to make the OLED device emit light, and the driving current can be expressed as:
From the expression it follows: IOLED is related to only the data voltage Vdata and the reference voltage VREF, and is not affected by the threshold voltage.
In the second light emitting stage T4, the first power control line VP1 is configured to output a high level, the second power control line VP2 is configured to output a low level, so that the first light emitting diode D1 is turned on, and the second light emitting diode D2 is turned off.
In the embodiment of the application, in the second light emitting stage, VP1 becomes high level, VP2 becomes low level, D2 is in the off state, D1 is turned on, and at this time, the current flowing through the light emitting device is still:
the OLED light-emitting brightness is not affected, and D1 and D2 alternately emit light in the same display frame, so that the problem of afterimage caused by direct current bias can be improved.
In an alternative embodiment, the pixel driving circuit has a second operation mode, the second operation mode is used for making the first light emitting diode D1 and the second light emitting diode D2 emit light alternately between adjacent display frames, as shown in fig. 4, in the second operation mode, the first operation period of the pixel driving circuit includes a scanning period T1, a compensation period T2 and a first light emitting period T3, and the second operation period of the pixel driving circuit includes a scanning period T1, a compensation period T2 and a second light emitting period T4, where the first operation period and the second operation period are two adjacent operation periods. Fig. 5 shows an operation timing of the pixel driving circuit corresponding to the second operation mode, and the second operation mode is described below based on fig. 1 and 5.
When entering the current display Frame (N Frame):
In the SCAN stage T1, the first power control line VP1 and the setting control line SEL are used for outputting a high level, so that the first switching transistor M2, the second switching transistor M3 and the fourth switching transistor M5 are turned off, the second power control line VP2 and the reference power control line SREF are used for outputting a low level, the third switching transistor M4 and the sixth switching transistor M7 are turned on, and the SCAN control line SCAN is used for scanning the pixel unit row by row to control the switching state of the fifth switching transistor M6, i.e., the fifth switching transistor M6 of the corresponding row is turned on when scanning the fifth switching transistor M6 of the corresponding row, and the fifth switching transistor M6 of the row is turned off during the rest of the SCAN stage.
In the embodiment of the application, in the scanning stage, the driving scheme adopts the scheme of synchronous driving and synchronous compensation, so that the duty ratio of program control time in display time can be reduced, the power line VP1 and the control line SEL are high level, M2, M3 and M5 are closed, VP2 and SREF are low level, M4 and M7 are opened, the scanning line SCAN is controlled to SCAN line by line, the low level is kept for a period of time, M6 is opened, the point A voltage VA=Vdata, the point C voltage is charged to VDD through M4, the point D voltage is charged to VREF through M7, the point B voltage can be initialized to the high level of VP1 due to the low level of Vdata, the voltage of the capacitor C2 is set to VDD, the voltage of the capacitor C1 is VC 1=VD-VC=VREF-VDD, and no current passes through the OLED due to the fact that the point M2 is closed in the stage.
In the compensation phase T2, the first power control line VP1 is used for outputting a low level, the second power control line VP2 is used for outputting a high level, the control line SEL is used for outputting a high level, the SCAN control line SCAN is used for outputting a high level, and the first, third, fourth and fifth switching transistors M2, M4, M5 and M6 are turned off, and the second and sixth switching transistors M3 and M7 are turned on.
In the embodiment of the present application, in the compensation phase, VP1 is switched to low level, VP2 is switched to high level, SCAN is completed, and the high level is maintained, then M2, M4, M5, M6 are turned off, M3 and M7 are turned on, vd=vref, VA is maintained at Vdata, point B discharges through the first storage capacitor C1 until reaching the equilibrium state vb=vdata+|vth 1| (VTH 1 is the threshold voltage of M1), vb=vc, vc1=vref-Vdata- |vth1|, and since M2 is turned off in this phase, OLED has no current passing.
In the first light emitting stage T3, the first power control line VP1 is used for outputting a low level, the second power control line VP2 is used for outputting a high level, the reference power control line SREF is used for pulling up the control terminal voltage of the sixth switching transistor M7, so that the sixth switching transistor M7 is turned off, the control line SEL is set for pulling down the control terminal voltages of the first switching transistor M2 and the fourth switching transistor M5, so that the first light emitting diode D1 is turned off, and the second light emitting diode D2 is turned on.
In the embodiment of the application, in the first light-emitting stage, SREF is pulled high, M7 is turned off, SEL is pulled low, M2 and M5 are turned on, and since VP2 is high level and VP1 is low level, D1 is in a cut-off state, D2 is turned on, driving current flows through the OLED device to make the OLED device emit light, and the driving current can be expressed as:
From the expression it follows: IOLED is related to only the data voltage Vdata and the reference voltage VREF, and is not affected by the threshold voltage.
The pixel driving circuit ends the first duty cycle, enters the second duty cycle, and enters the next display Frame (n+1frame):
In the SCAN stage T1, the first power control line VP1 and the setting control line SEL are used for outputting a high level, so that the first switching transistor M2, the second switching transistor M3 and the fourth switching transistor M5 are turned off, the second power control line VP2 and the reference power control line SREF are used for outputting a low level, the third switching transistor M4 and the sixth switching transistor M7 are turned on, and the SCAN control line SCAN is used for scanning the pixel unit row by row to control the switching state of the fifth switching transistor M6, i.e., the fifth switching transistor M6 of the corresponding row is turned on when scanning the fifth switching transistor M6 of the corresponding row, and the fifth switching transistor M6 of the row is turned off during the rest of the SCAN stage.
In the embodiment of the application, in the scanning stage, the driving scheme adopts the scheme of synchronous driving and synchronous compensation, so that the duty ratio of program control time in display time can be reduced, the power line VP1 and the control line SEL are high level, M2, M3 and M5 are closed, VP2 and SREF are low level, M4 and M7 are opened, the scanning line SCAN is controlled to SCAN line by line, the low level is kept for a period of time, M6 is opened, the point A voltage VA=Vdata, the point C voltage is charged to VDD through M4, the point D voltage is charged to VREF through M7, the point B voltage can be initialized to the high level of VP1 due to the low level of Vdata, the voltage of the capacitor C2 is set to VDD, the voltage of the capacitor C1 is VC 1=VD-VC=VREF-VDD, and no current passes through the OLED due to the fact that the point M2 is closed in the stage.
In the compensation phase T2, the first power control line VP1 is used for outputting a low level, the second power control line VP2 is used for outputting a high level, the control line SEL is used for outputting a high level, the SCAN control line SCAN is used for outputting a high level, and the first, third, fourth and fifth switching transistors M2, M4, M5 and M6 are turned off, and the second and sixth switching transistors M3 and M7 are turned on.
In the embodiment of the present application, in the compensation phase, VP1 is switched to low level, VP2 is switched to high level, SCAN is completed, and the high level is maintained, then M2, M4, M5, M6 are turned off, M3 and M7 are turned on, vd=vref, VA is maintained at Vdata, point B discharges through the first storage capacitor C1 until reaching the equilibrium state vb=vdata+|vth 1| (VTH 1 is the threshold voltage of M1), vb=vc, vc1=vref-Vdata- |vth1|, and since M2 is turned off in this phase, OLED has no current passing.
In the second light emitting stage T4, the first power control line VP1 is configured to output a high level, the second power control line VP2 is configured to output a low level, so that the first light emitting diode D1 is turned on, and the second light emitting diode D2 is turned off.
In the embodiment of the application, in the second light emitting stage, VP1 becomes high level, VP2 becomes low level, D2 is in the off state, D1 is turned on, and at this time, the current flowing through the light emitting device is still:
The OLED light-emitting brightness is not affected, and the pixel driving circuit controls the D1 and the D2 to alternately emit light between adjacent display frames through the first working period and the second working period, so that the problem of afterimage caused by direct current bias can be improved.
The pixel driving circuit provided by the application utilizes specific sequential logic, the alternating current control signal line provides voltage for the pixel driving circuit, the voltage drop of the power supply voltage is reduced, the aging and direct current bias voltage of the device are improved through the alternating current light emitting device, the afterimage problem can be effectively improved, the technical problem that the afterimage appears in a picture due to unstable driving device is solved, in addition, the circuit has a compensation function on threshold voltage Vth drift, the influence of the threshold voltage on the driving current is reduced, and the OLED display uniformity is enhanced.
According to an aspect of an embodiment of the present application, there is provided an embodiment of a display device, as shown in fig. 6, the display device including a substrate 100, the substrate 100 having a pixel driving circuit 200 as described in any one of the above.
The foregoing is only a specific embodiment of the application to enable those skilled in the art to understand or practice the application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the application. Thus, the present application is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (9)
1. The pixel driving circuit is characterized by comprising a driving transistor, a first switching transistor, a second switching transistor, a third switching transistor, a fourth switching transistor, a fifth switching transistor, a sixth switching transistor, a first storage capacitor, a second storage capacitor and an alternating current light emitting device; wherein:
the first end of the driving transistor is connected with a first power supply control line, and the second end of the driving transistor is connected with the first end of the first switch transistor;
the control end of the first switch transistor is connected with a setting control line, and the second end of the first switch transistor is connected with one end of the alternating current light emitting device;
The other end of the alternating current light-emitting device is connected with a second power supply control line;
The control end of the second switching transistor is connected with the first power supply control line, the first end of the second switching transistor is connected with one end of the first storage capacitor, and the second end of the second switching transistor is connected with the first end of the first switching transistor;
The control end of the third switching transistor is connected with the second power supply control line, the first end of the third switching transistor is connected with the first power supply control line, and the second end of the third switching transistor is connected with one end of the first storage capacitor;
the other end of the first storage capacitor is connected with the second end of the fourth switching transistor;
The control end of the fourth switching transistor is connected with the setting control line, and the first end of the fourth switching transistor is connected with the control end of the driving transistor;
the second storage capacitor is connected with the fourth switching transistor in parallel;
The control end of the fifth switching transistor is connected with the scanning control line, the first end of the fifth switching transistor is connected with the data line, and the second end of the fifth switching transistor is connected with the control end of the driving transistor;
the second end of the sixth switching transistor is connected with a reference power supply line, the control end of the sixth switching transistor is connected with the reference power supply control line, and the first end of the sixth switching transistor is connected with the second end of the fourth switching transistor;
the first power supply control line and the second power supply control line are connected with an alternating current power supply.
2. The circuit of claim 1, wherein the ac light emitting device comprises a first light emitting diode and a second light emitting diode, wherein a positive electrode of the first light emitting diode is connected to the second terminal of the first switching transistor, a negative electrode of the first light emitting diode is connected to the second power control line, a positive electrode of the second light emitting diode is connected to the second power control line, and a negative electrode of the second light emitting diode is connected to the second terminal of the first switching transistor.
3. The circuit of claim 2, wherein the pixel drive circuit has a first mode of operation for alternately illuminating the first light emitting diode and the second light emitting diode within the same display frame, and wherein each duty cycle of the pixel drive circuit includes a scan phase, a compensation phase, a first illumination phase, and a second illumination phase.
4. A circuit according to claim 3, wherein the pixel driving circuit has a second mode of operation for alternately illuminating the first and second light emitting diodes between adjacent display frames, in which second mode of operation the first duty cycle of the pixel driving circuit comprises the scanning phase, the compensation phase and the first illumination phase, and the second duty cycle of the pixel driving circuit comprises the scanning phase, the compensation phase and the second illumination phase, the first and second duty cycles being adjacent two duty cycles.
5. The circuit according to any one of claims 3 or 4, wherein in the scanning stage, the first power supply control line and the set control line are used for outputting a high level, the first switching transistor, the second switching transistor, and the fourth switching transistor are turned off, the second power supply control line and the reference power supply control line are used for outputting a low level, the third switching transistor and the sixth switching transistor are turned on, and the scanning control line is used for scanning pixel cells line by line to control a switching state of the fifth switching transistor.
6. The circuit of any one of claims 3 or 4, wherein during the compensation phase, the first power control line is configured to output a low level, the second power control line is configured to output a high level, the control line is configured to output a high level, and the scan control line is configured to output a high level, such that the first switching transistor, the third switching transistor, the fourth switching transistor, and the fifth switching transistor are turned off, and the second switching transistor and the sixth switching transistor are turned on.
7. The circuit of any one of claims 3 or 4, wherein during the first light-emitting phase, the first power supply control line is configured to output a low level, the second power supply control line is configured to output a high level, the reference power supply control line is configured to pull up a control terminal voltage of the sixth switching transistor to turn off the sixth switching transistor, the set control line is configured to pull down control terminal voltages of the first switching transistor and the fourth switching transistor to turn on the first switching transistor and the fourth switching transistor to turn off the first light-emitting diode, and the second light-emitting diode is configured to turn on.
8. The circuit of any one of claims 3 or 4, wherein in the second lighting phase, the first power control line is configured to output a high level, the second power control line is configured to output a low level, the first light emitting diode is turned on, and the second light emitting diode is turned off.
9. A display device comprising a substrate, wherein the substrate has the pixel driving circuit according to any one of claims 1 to 8.
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