CN109872693B - Pixel, driving method, display panel with pixel and display device - Google Patents
Pixel, driving method, display panel with pixel and display device Download PDFInfo
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- CN109872693B CN109872693B CN201910244464.XA CN201910244464A CN109872693B CN 109872693 B CN109872693 B CN 109872693B CN 201910244464 A CN201910244464 A CN 201910244464A CN 109872693 B CN109872693 B CN 109872693B
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Abstract
The invention discloses a pixel, a driving method, a display panel with the pixel and a display device, wherein the pixel comprises an organic light emitting diode, a driving unit and a compensation unit, and the driving unit is combined with the organic light emitting diode; the compensation unit is combined to the data line and the organic light emitting diode; when the pixel is in the compensation time period, the compensation unit is used for acquiring a difference value between a data voltage provided by the data line and an anode voltage of the organic light emitting diode, and the driving unit adjusts a driving current according to the difference value, wherein the driving current is used for driving the organic light emitting diode to emit light. The invention can adjust the driving current according to the difference value between the data voltage provided by the data line and the anode voltage of the organic light-emitting diode, so that the driving current is increased to compensate the deterioration of the organic light-emitting diode, and the reduction of the brightness of the organic light-emitting diode can be reduced.
Description
Technical Field
The invention relates to the technical field of display, in particular to a pixel, a driving method, a display panel with the pixel and a display device with the pixel.
Background
Nowadays, with the development of multimedia technology and the advent of information society, the demand for electronic devices, such as display devices, communication devices, and the like, is increasing.
Taking a display device as an example, in recent years, three new display technologies have emerged: plasma displays, field emission displays and organic electroluminescent displays, all make up for the deficiencies of cathode ray tubes and liquid crystal displays to a certain extent.
The Organic Light Emitting Devices (OLEDs for short) have a series of advantages such as self-luminescence, low voltage dc driving, full curing, wide viewing angle, and rich color, and compared with the liquid crystal display, the Organic Light Emitting device does not need a backlight source, has a large viewing angle, low power, a response speed 1000 times that of the liquid crystal display, and a manufacturing cost lower than that of the liquid crystal display with the same resolution. Therefore, the organic electroluminescent display has a wide application prospect, and is considered as one of the future flat panel display technologies with great competitiveness.
The organic electroluminescent display realizes light emission through the organic light emitting diode, however, in actual operation, as time passes, the organic light emitting diode is deteriorated to cause efficiency variation, resulting in failure of the corresponding pixel to display an image of desired luminance, and as such deterioration continues, the life span of the organic light emitting diode is also greatly shortened.
Disclosure of Invention
The invention aims to provide a pixel capable of compensating the deterioration of an organic light emitting diode, a driving method, a display panel with the pixel and a display device.
To achieve one of the above objects, an embodiment of the present invention provides a pixel, including:
an organic light emitting diode;
a driving unit coupled to the organic light emitting diode;
a compensation unit coupled to the data line and the organic light emitting diode;
when the pixel is in a compensation time period, the compensation unit is used for acquiring a difference value between a data voltage provided by the data line and an anode voltage of the organic light emitting diode, and the driving unit adjusts a driving current according to the difference value, wherein the driving current is used for driving the organic light emitting diode to emit light;
the driving unit comprises a first transistor, wherein the grid electrode of the first transistor is connected with a first node, the source electrode of the first transistor is connected with a first power supply, the drain electrode of the first transistor is connected with the anode of the organic light emitting diode, the cathode of the organic light emitting diode is connected with a second power supply, driving current flows from the first power supply to the second power supply through the first transistor and the organic light emitting diode, and the driving current drives the organic light emitting diode to emit light in a display time period; when the pixel is in a compensation time period, the compensation unit adjusts a first voltage of a first node according to a difference between a data voltage provided by the data line and an anode voltage of the organic light emitting diode, and the first transistor adjusts the driving current according to the first voltage;
the compensation unit comprises a second transistor, a third transistor, a fourth transistor and a feedback capacitor connected between a first node and a second node, wherein a grid electrode of the second transistor and a grid electrode of the third transistor are both connected with an ith scanning line so that the second transistor and the third transistor are started in a first compensation time period, the other two electrodes of the second transistor are respectively connected with the first node and a drain electrode of the first transistor, the other two electrodes of the third transistor are respectively connected with the second node and an anode of the organic light emitting diode, a grid electrode of the fourth transistor is connected with an (i + 1) th scanning line so that the fourth transistor is started in a second compensation time period, and the other two electrodes of the fourth transistor are respectively connected with a data line and the second node;
the pixel further comprises a reset unit, the reset unit is used for initializing the first node and the second node, the reset unit comprises a sixth transistor and a seventh transistor, the grid electrode of the sixth transistor and the grid electrode of the seventh transistor are both connected with the i-1 th scanning line, so that the sixth transistor and the seventh transistor are turned on in an initialization time period, the other two electrodes of the sixth transistor are respectively connected with a reference voltage and the first node, and the other two electrodes of the seventh transistor are respectively connected with the reference voltage and the second node;
the pixel further comprises an energy storage unit and a control unit, the energy storage unit is connected with the second node and the first power supply, the control unit is used for controlling the driving current, the energy storage unit comprises a storage capacitor, two ends of the storage capacitor are respectively connected with the second node and the first power supply, the control unit comprises a fifth transistor, a grid electrode of the fifth transistor is connected with a control line, so that the fifth transistor is started in a display time period, and the other two electrodes of the fifth transistor are respectively connected with a drain electrode of the first transistor and an anode of the organic light emitting diode.
In order to achieve one of the above objects, an embodiment of the present invention provides a display panel including the pixel according to any one of the above aspects.
In order to achieve one of the above objects, an embodiment of the present invention provides a display device including the display panel as described above.
In order to achieve one of the above objects, an embodiment of the present invention provides a method for driving a pixel, including:
acquiring a difference value between a data voltage provided by a data line and an anode voltage of the organic light emitting diode in a compensation time period;
adjusting a driving current according to the difference value, and driving the organic light emitting diode to emit light by using the driving current;
the driving method specifically comprises the following steps:
in an initialization time period, initializing the first node and the second node, driving an i-1 th scanning line to be started to enable a sixth transistor and a seventh transistor to be conducted, wherein the sixth transistor is connected with a reference voltage and the first node to initialize the first node, and the seventh transistor is connected with the reference voltage and the second node to initialize the second node;
in the first compensation time period, the ith scanning line is driven to be started to enable the second transistor and the third transistor to be conducted, the second transistor turns on the first node and the drain of the first transistor so that the first voltage V1 of the first node is VDD-Vth, the third transistor turns on the second node and the anode of the organic light emitting diode so that the second voltage V2 of the second node is V _ oled, wherein the first node and the second node are located at two sides of the feedback capacitor, VDD is a first power voltage of the first power, Vth is a threshold voltage of the first transistor, V _ oled is an anode voltage of the organic light emitting diode, the first node is connected with the grid electrode of the first transistor, the source electrode of the first transistor is connected with the first power supply, the drain electrode of the first transistor is combined to the anode of the organic light emitting diode, and the cathode of the organic light emitting diode is connected with a second power supply;
driving an i +1 th scan line to be turned on such that a fourth transistor is turned on, the fourth transistor turning on a data line and a second node such that a second voltage V2 is Vdata, and adjusting the first voltage to a first voltage V1 which is VDD-Vth + (Vdata-V _ oled) according to a difference between a data voltage supplied from the data line and an anode voltage of the organic light emitting diode, in a second compensation period, wherein the Vdata is the data voltage supplied from the data line and adjusts a driving current according to the first voltage;
controlling a driving current to flow from a first power supply to a second power supply through the first transistor and the organic light emitting diode to drive the organic light emitting diode to emit light in a display time period;
the step of controlling a driving current to flow from a first power source to a second power source through the first transistor and the organic light emitting diode to drive the organic light emitting diode to emit light in a display period specifically includes:
in a display time period, a driving control line is turned on to enable a fifth transistor to be conducted, the fifth transistor conducts a drain electrode of a first transistor and an anode electrode of an organic light emitting diode to control a driving current to flow from a first power supply to a second power supply through the first transistor and the organic light emitting diode so as to drive the organic light emitting diode to emit light.
Compared with the prior art, the invention has the beneficial effects that: according to the embodiment of the invention, the driving current can be adjusted according to the difference value between the data voltage provided by the data line and the anode voltage of the organic light emitting diode, so that the driving current is increased to compensate the deterioration of the organic light emitting diode, and the reduction of the brightness of the organic light emitting diode can be reduced.
Drawings
FIG. 1 is a schematic diagram of a display panel according to an embodiment of the invention;
FIG. 2 is another schematic diagram of a display panel according to an embodiment of the invention;
FIG. 3 is a simplified schematic diagram of a pixel according to an embodiment of the invention;
FIG. 4 is a simplified schematic diagram of a pixel in accordance with an embodiment of the present invention;
FIG. 5 is a diagram illustrating the driving current variation of an OLED in the normal state and the degraded state in the prior art;
FIG. 6 is a diagram illustrating the relationship between the driving current and the degradation time of an OLED in the prior art;
FIG. 7 is a schematic diagram of the driving current variation of the OLED in the normal state and the degraded state according to one embodiment of the present invention;
FIG. 8 is a diagram illustrating the relationship between the driving current and the degradation time of the OLED according to one embodiment of the present invention;
FIG. 9 is a block diagram of a pixel structure according to an embodiment of the invention;
FIG. 10 is a detailed schematic diagram of a pixel in accordance with an embodiment of the invention;
fig. 11 is a pixel driving timing diagram of a specific example of the present invention;
fig. 12 is a step diagram of a pixel driving method according to an embodiment of the invention.
Detailed Description
The present invention will be described in detail below with reference to specific embodiments shown in the drawings. These embodiments are not intended to limit the present invention, and structural, methodological, or functional changes made by those skilled in the art according to these embodiments are included in the scope of the present invention.
In the various drawings of the present invention, some dimensions of structures or portions are exaggerated relative to other structures or portions for convenience of illustration, and thus, are used only to illustrate the basic structure of the subject matter of the present invention.
Also, terms used herein such as "upper," "above," "lower," "below," and the like, denote relative spatial positions of one element or feature with respect to another element or feature as illustrated in the figures for ease of description.
Spatially relative positional terms may be intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures, e.g., if the device in the figures is turned over, elements described as "below" or "beneath" other elements or features would then be "above" the other elements or features, and thus the exemplary term "below" may encompass both an orientation of above and below, and a device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.
Referring to fig. 1, an embodiment of the invention provides a display device, which includes a display panel 100.
Here, the display device is exemplified by an organic electroluminescent display panel, for example, an active organic electroluminescent display device, but not limited thereto.
The display panel 100 includes an array substrate 10 and a plurality of pixels 20 disposed above the array substrate 10 and arranged in an array.
The pixels 20 may include a red pixel emitting red light, a green pixel emitting green light, and a blue pixel emitting blue light, but not limited thereto, and may also include pixels emitting other colors of light, so that light emitting in various colors can be realized.
Referring to fig. 2, the array substrate 10 has horizontal control lines extending in a row direction X and vertical control lines extending in a column direction Y.
The horizontal control line may be a control line for emitting a control signal EM, a Scan line for emitting a Scan signal, and the like, and the Scan line includes an i-1 th Scan line for emitting a Scan signal Scan i-1, an i-th Scan line for emitting a Scan signal Scan i, an i +1 th Scan line for emitting a Scan signal Scan i +1, and the like.
In addition, i is an integer of 2 or more.
The vertical control line may be a data line or the like that outputs a data voltage Vdata for providing image data to the corresponding pixel 20 of the column, including, for example, a red data line for carrying a red data signal to a red pixel, a green data line for carrying a green data signal to a green pixel, and a blue data line for carrying a blue data signal to a blue pixel.
Here, each control line may be controlled by an integrated circuit, for example, a horizontal control line may be controlled by a Gate In Panel (GIP) circuit, or a horizontal control line may be controlled by a Gate Driver on array (goa) circuit, and a vertical data line may be controlled by a data control circuit, which may be determined according to actual situations.
Referring to fig. 3, the pixel 20 includes an organic light emitting diode 30, a driving unit 50, and a compensation unit 40.
Of course, the pixel 20 may also include other structures, which are not shown in fig. 3 for simplicity.
The driving unit 50 is coupled to the organic light emitting diode 30.
The compensation unit 40 is coupled to the data line and the organic light emitting diode 30.
Wherein, when the pixel 20 is in the compensation time period, the compensation unit 40 is used for obtaining a difference value between the data voltage Vdata provided by the data line and the anode voltage V _ oled of the organic light emitting diode 30, and the driving unit 50 adjusts the driving current I according to the difference valuedsDriving current IdsFor driving the organic light emitting diode 30 to emit light.
The present embodiment may adjust the driving current I according to a difference between the data voltage Vdata provided from the data line and the anode voltage V _ oled of the organic light emitting diode 30dsSo that the current I is drivendsRising to compensate for the deterioration of the organic light emitting diode 30, the decrease in the luminance of the organic light emitting diode 30 can be reduced.
In a specific example, and with reference to fig. 4, the driving unit 50 includes a first transistor M1, but not limited thereto.
The organic light emitting diode 30 includes an anode 301 and a cathode 302, and the cathode 302 of the organic light emitting diode 30 is connected to the second power ELVSS.
The first transistor M1 is a driving transistor, the gate G of the first transistor M1 is connected to the first node N1, the source S of the first transistor M1 is coupled to the first power source ELVDD, and the drain D of the first transistor M1 is coupled to the organic light emitting diode 30Anode 301, drive current IdsThe driving current I flows from the first power source ELVDD to the second power source ELVSS through the first transistor M1 and the OLED 30dsThe organic light emitting diode 30 is driven to emit light for the display period T4.
Here, the first power source ELVDD is a high-level voltage source, the second power source ELVSS is a low-level voltage source, the first power source ELVDD and the second power source ELVSS serve as driving power sources for the pixels 20, the first power source ELVDD supplies the first power source voltage VDD to the pixels 20, the second power source ELVSS supplies the second power source voltage VSS to the pixels 20, and the first power source ELVDD and the second power source ELVSS may be supplied with power by an external power source.
When the pixel 20 is in the first and second compensation periods T2 and T3, the compensation unit 40 adjusts the first voltage V1 of the first node N1 according to a difference between the data voltage Vdata provided by the data line and the anode voltage V _ oled of the organic light emitting diode 30, and the first transistor M1 adjusts the driving current I according to the first voltage V1ds。
It should be noted that, in other embodiments, the driving unit 50 may have other structures, and the driving current IdsNor is it limited to regulation according to the first voltage V1.
In addition, when the first component is described as being coupled to the second component, the first component may be directly connected to the second component, or the first component may be indirectly connected to the second component through one or more other components, for example, the "the drain D of the first transistor M1 is coupled to the anode 301 of the organic light emitting diode 30" may mean that the drain D of the first transistor M1 is directly connected to the anode 301 of the organic light emitting diode 30, or there may be other structures between the drain D of the first transistor M1 and the anode 301 of the organic light emitting diode 30, such as a switching transistor, and when the switching transistor is turned on, the drain D of the first transistor M1 is indirectly communicated with the anode 301 of the organic light emitting diode 30, and the descriptions of other parts may refer to the description herein.
In contrast, when the first component is described as being connected to the second component, i.e., the first component is directly connected to the second component, and no other component is located between the first component and the second component, for example, the "gate G of the first transistor M1 is connected to the first node N1" means that the first node N1 is directly connected to the gate G of the first transistor M1, and the description of other parts can refer to the description herein.
In the prior art, referring to fig. 5, a solid line S1 is a graph of a gate-source voltage of a driving transistor versus a driving current, a solid line S2 is a graph of a voltage of an organic light emitting diode versus a driving current in a normal state, a broken line S3 is a graph of a voltage of an organic light emitting diode versus a driving current in a degraded state, and a driving current I corresponding to a junction a of the solid line S2 and the solid line S1 (i.e., an operating point of the driving transistor) is shown1I.e. the driving current flowing through the OLED in the normal state, the driving current I corresponding to the junction b of the dotted line S3 and the solid line S1 (i.e. the operating point of the driving transistor)2I.e. the driving current flowing through the organic light emitting diode in the degraded state, i.e. the driving current flowing through the organic light emitting diode in the degraded state is reduced (the driving current is I)1Down to I2)。
Here, as time passes, the organic light emitting diode may be deteriorated, and as the organic light emitting diode is deteriorated, the resistance of the organic light emitting diode increases, resulting in an increase in the anode voltage of the organic light emitting diode, and when the gate-source voltage of the driving transistor is not changed, the driving current actually flowing through the organic light emitting diode may gradually decrease (in conjunction with fig. 6), resulting in a corresponding pixel not displaying an image of desired luminance.
In this embodiment, referring to fig. 7, a solid line L1 is a graph of a gate-source voltage and a driving current of the first transistor M1, a dashed line L2 is a graph of a gate-source voltage and a driving current of the first transistor M1 under the action of the compensation unit 40, a solid line L3 is a graph of a voltage and a driving current of the organic light emitting diode 30 in a normal state, a dashed line L4 is a graph of a voltage and a driving current of the organic light emitting diode 30 in a degraded state, and a driving current I corresponding to an intersection c of a solid line L3 and a solid line L1 (i.e., an operating point of the first transistor M1) is shownds1I.e. the junction d of the dotted line L4 and the dotted line L2 (i.e. the first point) of the driving current flowing through the OLED 30 in the normal stateAn operating point of a transistor M1) corresponding to the driving current Ids2I.e. the driving current through the organic light emitting diode 30 in a degraded state, i.e. the driving current through the organic light emitting diode 30 in a degraded state remains substantially unchanged.
The compensation unit 40 of the present embodiment may adjust the first voltage V1 according to a difference between the data voltage Vdata provided by the data line and the anode voltage V _ oled of the organic light emitting diode 30, so that the gate-source voltage versus the driving current is changed to drive the driving current IdsRise (i.e., rise of drive current to I in degraded state)ds2At this time, the drive current Ids2Substantially equal to the drive current I in the normal stateds1) The driving current I is dependent on the deterioration of the OLED 30dsGradually increasing (see FIG. 8), driving the current IdsThe rise may compensate for the degradation of the organic light emitting diode 30 to reduce the decrease in the luminance of the organic light emitting diode 30.
In addition, the adjustment amount of the first voltage V1 according to the present embodiment is related to the data voltage Vdata and the anode voltage V _ oled, and the data voltage Vdata is constant, that is, the adjustment amount of the first voltage V1 can accurately reflect the variation amount of the anode voltage V _ oled, so that the compensation result is more reliable.
Specifically, referring to fig. 9, the pixel 20 further includes a reset unit 60, an energy storage unit 70, and a control unit 80.
The reset unit 60 is used for initializing the first node N1 and the second node N2.
The energy storage unit 70 is connected to the second node N2 and the first power source ELVDD.
The control unit 80 is used for controlling the driving current IdsThat is, the control unit 80 is used to control the driving current IdsWhether or not to flow into the organic light emitting diode 30.
In one embodiment, referring to fig. 10 and 11, the compensation unit 40 includes a second transistor M2, a third transistor M3, a fourth transistor M4, and a feedback capacitor C2 connected between a first node N1 and a second node N2.
The reset unit 60 includes a sixth transistor M6 and a seventh transistor M7.
The energy storage unit 70 includes a storage capacitor C1.
The control unit 50 includes a fifth transistor M5.
That is, the organic light emitting diode 30 is driven to emit light at this time in the form of 7T2C, and the pixel 20 of the present embodiment is configured to receive the i-1 th Scan signal Scan i-1, the i-th Scan signal Scan i, the i +1 th Scan signal Scan i +1, the data voltage Vdata, the control signal EM, the first power voltage VDD, the second power voltage VSS, and the reference voltage Vref.
It should be noted that all the transistors in this embodiment are PMOS transistors, the first transistor M1 is a driving transistor, the second to seventh transistors are switching transistors, and when the driving signals (including the i-1 th Scan signal Scan i-1, the i-th Scan signal Scan i, the i +1 th Scan signal Scan i +1, and the control signal EM) are low, the corresponding transistors are turned on.
The 7T2C circuit will be described in detail below.
The gate G of the first transistor M1 is connected to the first node N1, the source S of the first transistor M1 is connected to the first power source ELVDD, and the drain D of the first transistor M1 is coupled to the anode 301 of the organic light emitting diode 30 through the fifth transistor M5.
The gate G of the second transistor M2 is connected to the ith scan line such that the second transistor M2 is turned on during the first compensation period T2, and the other two electrodes of the second transistor M2 are respectively connected to the first node N1 and the drain D of the first transistor M1.
The gate G of the third transistor M3 is connected to the ith scan line such that the third transistor M3 is turned on during the first compensation period T2, and the other two electrodes of the third transistor M3 are respectively connected to the second node N2 and the anode 301 of the organic light emitting diode 30.
The gate G of the fourth transistor M4 is connected to the (i + 1) th scan line so that the fourth transistor M4 is turned on during the second compensation period T3, and the other two electrodes of the fourth transistor M4 are respectively connected to the data line and the second node N2.
The gate G of the fifth transistor M5 is connected to the control line such that the fifth transistor M5 is turned on during the display period T4, and the other two electrodes of the fifth transistor M5 are respectively connected to the drain D of the first transistor M1 and the anode 301 of the organic light emitting diode 30.
The gate G of the sixth transistor M6 is connected to the i-1 th scan line such that the sixth transistor M6 is turned on during the initialization period T1, and the other two electrodes of the sixth transistor M6 are respectively connected to the reference voltage Vref and the first node N1.
The gate G of the seventh transistor M7 is connected to the i-1 th scan line such that the seventh transistor M7 is turned on during the initialization period T1, and the other two electrodes of the seventh transistor M7 are respectively connected to the reference voltage Vref and the second node N2.
Two ends of the storage capacitor C1 are connected to the second node N2 and the first power source ELVDD, respectively.
The feedback capacitor C2 is located between the first node N1 and the second node N2.
Specifically, when the pixel 20 is in the initialization period T1, the i-1 th scan line drives the sixth transistor M6 and the seventh transistor M7 to be turned on, the first voltage V1 of the first node N1 is equal to Vref, and the second voltage V2 of the second node N2 is equal to Vref, so that the initialization of the first node N1 and the second node N2 is realized.
When the pixel 20 is in the first compensation period T2, the ith scan line drives the second transistor M2 and the third transistor M3 to be turned on, the first voltage V1 of the first node N1 is VDD-Vth, the second voltage V2 of the second node N2 is V _ oled, where VDD is the first power voltage output by the first power ELVDD, Vth is the threshold voltage of the first transistor Vth, V _ oled is the anode voltage of the organic light emitting diode 30, and the storage capacitor C1 is charged by the anode voltage V _ oled.
When the pixel 20 is in the second compensation period T3, the i +1 th scan line drives the fourth transistor M4 to turn on, and since the voltage difference across the feedback capacitor C2 remains unchanged, the first voltage V1 of the first node N1 is VDD-Vth + (Vdata-V _ oled), and the second voltage V2 of the second node N2 is Vdata, where Vdata is the data voltage provided by the data line, and the storage capacitor C1 is charged by the data voltage Vdata.
When the pixel 20 is in the display period T4, the control line drives the fifth transistor M5 to turn on so that the driving current IdsDriving the organic light emitting diode 30 to emit lightLight, at this time, drive current Ids＝K*(V_anode-Vdata)2K is constant, so that the current I is drivendsIs not influenced by the first power voltage VDD, and the anode voltage V _ anode is also constant in a certain period of time, so that the driving current IdsThe display effect can be improved by stabilizing the display device.
It can be seen that when the degradation of the organic light emitting diode 30 causes the anode voltage V _ anode to increase, the driving current I is compensated by the compensation unit 40dsIt is raised to compensate for the deterioration of the organic light emitting diode 30, and thus the decrease of the luminance of the organic light emitting diode 30 can be reduced.
That is, as the organic light emitting diode 30 is deteriorated, the anode voltage V _ oled of the organic light emitting diode 30 supplied to the second node N2 is increased, and thus, when the same data voltage Vdata is supplied to the data line, the voltage of the second node N2 is increased in a lower magnitude than the voltage of the organic light emitting diode 30 when it is not deteriorated, and the voltage of the first node N1 is increased in a lower magnitude correspondingly, i.e., the gate voltage of the first transistor M1 is increased in a lower magnitude, at which the amount of the driving current supplied from the first transistor M1 is increased to compensate for the deterioration of the organic light emitting diode 30, the decrease in the luminance of the organic light emitting diode 30 can be greatly reduced.
An embodiment of the present invention further provides a method for driving the pixel 20, and with reference to the description of the pixel 20 and fig. 10 to 12, the method for driving the pixel 20 includes the steps of:
acquiring a difference value between the data voltage Vdata provided by the data line and the anode voltage V _ oled of the organic light emitting diode 30 in the compensation time period;
adjusting the drive current I according to the differencedsAnd using the drive current IdsThe organic light emitting diode 30 is driven to emit light.
The present embodiment may adjust the driving current I according to a difference between the data voltage Vdata provided from the data line and the anode voltage V _ oled of the organic light emitting diode 30dsSo that the current I is drivendsIs raised to compensate for the deterioration of the organic light emitting diode 30, can be reducedThe brightness of the small organic light emitting diode 30 is reduced.
In a specific example, the driving method of the pixel 20 includes the steps of:
driving the first node N1 to obtain a first voltage V1 during the first compensation period T2, the first node N1 being connected to the gate G of the first transistor M1, the gate G of the first transistor M1 being coupled to the data line, the source S of the first transistor M1 being connected to the first power source ELVDD, the drain D of the first transistor M1 being coupled to the anode 301 of the organic light emitting diode 30, the cathode 302 of the organic light emitting diode 30 being connected to the second power source ELVSS;
adjusting the first voltage V1 of the first node N1 according to a difference between the data voltage Vdata supplied from the data line and the anode voltage V _ oled of the organic light emitting diode 30 and adjusting the driving current I according to the first voltage V1 during the second compensation period T3ds；
During the display period T4, the drive current I is controlleddsThe first power ELVDD flows to the second power ELVSS via the first transistor M1 and the organic light emitting diode 30 to drive the organic light emitting diode 30 to emit light.
The driving method of the pixel 20 of the present embodiment may adjust the first voltage V1 according to a difference between the data voltage Vdata provided by the data line and the anode voltage V _ oled of the organic light emitting diode 30 such that the driving current IdsRises to compensate for the deterioration of the organic light emitting diode 30, and thus the decrease in the luminance of the organic light emitting diode 30 can be reduced.
Specifically, the driving method of the pixel 20 includes the steps of:
s1: in the initialization period T1, the i-1 th Scan line is driven to turn on so that the sixth transistor M6 and the seventh transistor M7 are turned on, that is, the Scan signal Scan i-1 is at a low level, and the other drive signals are at a high level, the sixth transistor M6 connects the reference voltage Vref to the first node N1 to initialize the first node N1, the first voltage V1 of the first node N1 is equal to Vref, the seventh transistor M7 connects the reference voltage Vref to the second node N2 to initialize the second node N2, and the second voltage V2 of the second node N2 is equal to Vref;
s2: in the first compensation time period T2, the ith Scan line is driven to be turned on to turn on the second transistor M2 and the third transistor M3, that is, the Scan signal Scan i is at a low level, and the other driving signals are at a high level, the second transistor M2 turns on the first node N1 and the drain D of the first transistor M1 to make the first voltage V1 of the first node N1 equal to VDD-Vth, the third transistor M3 turns on the second node N2 and the anode 301 of the organic light emitting diode 30 to make the second voltage V2 of the second node N2 equal to V _ oled, wherein the first node N1 and the second node N2 are located on both sides of the feedback capacitor C2, VDD is the first power voltage of the first power source ELVDD, Vth is the threshold voltage of the first transistor M1, and V _ oled is the anode voltage of the organic light emitting diode 30;
s3: in the second compensation period T3, the i +1 th Scan line is driven to turn on the fourth transistor M4, that is, the Scan signal Scan i +1 is at a low level, and the other driving signals are at a high level, the fourth transistor M4 turns on the data line and the second node N2 to turn on the second voltage V2 — Vdata, and the first voltage V1 is adjusted to the first voltage V1 — VDD-Vth + (Vdata-V _ oled) according to a difference between the data voltage Vdata provided by the data line and the anode voltage V _ oled of the organic light emitting diode 30, wherein Vdata is the data voltage provided by the data line;
here, the voltage difference between the first node N1 and the second node N2 remains unchanged due to the capacitance characteristic of the feedback capacitor C2, and when the second voltage V2 of the second node N2 is changed from the anode voltage V _ oled to the data voltage Vdata, the first voltage V1 of the first node N1 is changed from VDD-Vth to VDD-Vth + (Vdata-V _ oled).
S4: during the display period T4, the driving control line is turned on to turn on the fifth transistor M5, i.e. the control signal EM is at a low level, the other driving signals are at a high level, and the fifth transistor M5 turns on the drain D of the first transistor M1 and the anode 301 of the oled 30 to control the driving current IdsThe first power ELVDD flows to the second power ELVSS via the first transistor M1 and the organic light emitting diode 30 to drive the organic light emitting diode 30 to emit light.
Here, the drive current Ids＝K(V_anode-Vdata)2K is constant, so that the current I is drivendsIs not influenced by the first power voltage VDD, and the anode voltage V _ anode is also constant in a certain period of time, so that the driving current IdsThe display effect can be improved by stabilizing the display device.
It can be seen that when the degradation of the organic light emitting diode 30 causes the anode voltage V _ anode to increase, the driving current I is compensated by the compensation unit 40dsIt is raised to compensate for the deterioration of the organic light emitting diode 30, and thus the decrease of the luminance of the organic light emitting diode 30 can be reduced.
That is, as the organic light emitting diode 30 is deteriorated, the anode voltage V _ oled of the organic light emitting diode 30 supplied to the second node N2 is increased, and thus, when the same data voltage Vdata is supplied to the data line, the voltage of the second node N2 is increased in a lower magnitude than the voltage of the organic light emitting diode 30 when it is not deteriorated, and the voltage of the first node N1 is increased in a lower magnitude correspondingly, i.e., the gate voltage of the first transistor M1 is increased in a lower magnitude, at which the amount of the driving current supplied from the first transistor M1 is increased to compensate for the deterioration of the organic light emitting diode 30, the decrease in the luminance of the organic light emitting diode 30 can be greatly reduced.
In summary, the compensation unit 40 of the present embodiment can adjust the first voltage V1 according to the difference between the data voltage Vdata provided by the data line and the anode voltage V _ oled of the organic light emitting diode 30, so that the driving current I is drivendsRising to compensate for the deterioration of the organic light emitting diode 30, the decrease in the luminance of the organic light emitting diode 30 can be reduced.
In addition, the adjustment amount of the first voltage V1 according to the present embodiment is related to the data voltage Vdata and the anode voltage V _ oled, and the data voltage Vdata is constant, that is, the adjustment amount of the first voltage V1 can accurately reflect the variation amount of the anode voltage V _ oled, so that the compensation result is more reliable.
In addition, the driving current I finally obtained in the present embodimentdsIs not influenced by the first power voltage VDD, and the anode voltage V _ anode is also constant in a certain period of time, so that the driving current IdsThe display effect can be improved by stabilizing the display device.
It should be understood that although the present description refers to embodiments, not every embodiment contains only a single technical solution, and such description is for clarity only, and those skilled in the art should make the description as a whole, and the technical solutions in the embodiments can also be combined appropriately to form other embodiments understood by those skilled in the art.
The above-listed detailed description is only a specific description of a possible embodiment of the present invention, and they are not intended to limit the scope of the present invention, and equivalent embodiments or modifications made without departing from the technical spirit of the present invention should be included in the scope of the present invention.
Claims (4)
1. A pixel, comprising:
an organic light emitting diode;
a driving unit coupled to the organic light emitting diode;
a compensation unit coupled to the data line and the organic light emitting diode;
when the pixel is in a compensation time period, the compensation unit is used for acquiring a difference value between a data voltage provided by the data line and an anode voltage of the organic light emitting diode, and the driving unit adjusts a driving current according to the difference value, wherein the driving current is used for driving the organic light emitting diode to emit light;
the driving unit comprises a first transistor, wherein the grid electrode of the first transistor is connected with a first node, the source electrode of the first transistor is connected with a first power supply, the drain electrode of the first transistor is connected with the anode of the organic light emitting diode, the cathode of the organic light emitting diode is connected with a second power supply, driving current flows from the first power supply to the second power supply through the first transistor and the organic light emitting diode, and the driving current drives the organic light emitting diode to emit light in a display time period; when the pixel is in a compensation time period, the compensation unit adjusts a first voltage of a first node according to a difference between a data voltage provided by the data line and an anode voltage of the organic light emitting diode, and the first transistor adjusts the driving current according to the first voltage;
the compensation unit comprises a second transistor, a third transistor, a fourth transistor and a feedback capacitor connected between a first node and a second node, wherein a grid electrode of the second transistor and a grid electrode of the third transistor are both connected with an ith scanning line so that the second transistor and the third transistor are started in a first compensation time period, the other two electrodes of the second transistor are respectively connected with the first node and a drain electrode of the first transistor, the other two electrodes of the third transistor are respectively connected with the second node and an anode of the organic light emitting diode, a grid electrode of the fourth transistor is connected with an (i + 1) th scanning line so that the fourth transistor is started in a second compensation time period, and the other two electrodes of the fourth transistor are respectively connected with a data line and the second node;
the pixel further comprises a reset unit, the reset unit is used for initializing the first node and the second node, the reset unit comprises a sixth transistor and a seventh transistor, the grid electrode of the sixth transistor and the grid electrode of the seventh transistor are both connected with the i-1 th scanning line, so that the sixth transistor and the seventh transistor are turned on in an initialization time period, the other two electrodes of the sixth transistor are respectively connected with a reference voltage and the first node, and the other two electrodes of the seventh transistor are respectively connected with the reference voltage and the second node;
the pixel further comprises an energy storage unit and a control unit, the energy storage unit is connected with the second node and the first power supply, the control unit is used for controlling the driving current, the energy storage unit comprises a storage capacitor, two ends of the storage capacitor are respectively connected with the second node and the first power supply, the control unit comprises a fifth transistor, a grid electrode of the fifth transistor is connected with a control line, so that the fifth transistor is started in a display time period, and the other two electrodes of the fifth transistor are respectively connected with a drain electrode of the first transistor and an anode of the organic light emitting diode.
2. A display panel comprising the pixel according to claim 1.
3. A display device characterized by comprising the display panel according to claim 2.
4. A method of driving a pixel as claimed in claim 1, comprising the steps of:
acquiring a difference value between a data voltage provided by a data line and an anode voltage of the organic light emitting diode in a compensation time period;
adjusting a driving current according to the difference value, and driving the organic light emitting diode to emit light by using the driving current;
the driving method specifically comprises the following steps:
in an initialization time period, initializing the first node and the second node, driving an i-1 th scanning line to be started to enable a sixth transistor and a seventh transistor to be conducted, wherein the sixth transistor is connected with a reference voltage and the first node to initialize the first node, and the seventh transistor is connected with the reference voltage and the second node to initialize the second node;
in the first compensation time period, the ith scanning line is driven to be started to enable the second transistor and the third transistor to be conducted, the second transistor turns on the first node and the drain of the first transistor so that the first voltage V1 of the first node is VDD-Vth, the third transistor turns on the second node and the anode of the organic light emitting diode so that the second voltage V2 of the second node is V _ oled, wherein the first node and the second node are located at two sides of the feedback capacitor, VDD is a first power voltage of the first power, Vth is a threshold voltage of the first transistor, V _ oled is an anode voltage of the organic light emitting diode, the first node is connected with the grid electrode of the first transistor, the source electrode of the first transistor is connected with the first power supply, the drain electrode of the first transistor is combined to the anode of the organic light emitting diode, and the cathode of the organic light emitting diode is connected with a second power supply;
driving an i +1 th scan line to be turned on such that a fourth transistor is turned on, the fourth transistor turning on a data line and a second node such that a second voltage V2 is Vdata, and adjusting the first voltage to a first voltage V1 which is VDD-Vth + (Vdata-V _ oled) according to a difference between a data voltage supplied from the data line and an anode voltage of the organic light emitting diode, in a second compensation period, wherein the Vdata is the data voltage supplied from the data line and adjusts a driving current according to the first voltage;
controlling a driving current to flow from a first power supply to a second power supply through the first transistor and the organic light emitting diode to drive the organic light emitting diode to emit light in a display time period;
the step of controlling a driving current to flow from a first power source to a second power source through the first transistor and the organic light emitting diode to drive the organic light emitting diode to emit light in a display period specifically includes:
in a display time period, a driving control line is turned on to enable a fifth transistor to be conducted, the fifth transistor conducts a drain electrode of a first transistor and an anode electrode of an organic light emitting diode to control a driving current to flow from a first power supply to a second power supply through the first transistor and the organic light emitting diode so as to drive the organic light emitting diode to emit light.
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| CN104851392A (en) * | 2015-06-03 | 2015-08-19 | 京东方科技集团股份有限公司 | Pixel driving circuit, pixel driving method, array substrate and display device |
| CN105609048A (en) * | 2016-01-04 | 2016-05-25 | 京东方科技集团股份有限公司 | Pixel compensating circuit and driving method thereof, and display apparatus |
| CN105679242A (en) * | 2015-12-07 | 2016-06-15 | 友达光电股份有限公司 | Pixel circuit and driving method thereof |
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| CN1909038A (en) * | 2005-08-01 | 2007-02-07 | 三星Sdi株式会社 | Organic light emitting display |
| CN104851392A (en) * | 2015-06-03 | 2015-08-19 | 京东方科技集团股份有限公司 | Pixel driving circuit, pixel driving method, array substrate and display device |
| CN105679242A (en) * | 2015-12-07 | 2016-06-15 | 友达光电股份有限公司 | Pixel circuit and driving method thereof |
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