CN110164363B - Pixel circuit of organic light-emitting display device and driving method thereof - Google Patents
Pixel circuit of organic light-emitting display device and driving method thereof Download PDFInfo
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- CN110164363B CN110164363B CN201810679993.8A CN201810679993A CN110164363B CN 110164363 B CN110164363 B CN 110164363B CN 201810679993 A CN201810679993 A CN 201810679993A CN 110164363 B CN110164363 B CN 110164363B
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- 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]
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Abstract
The present invention provides a pixel circuit of an organic light emitting display device, including: a first transistor, a second transistor, a feedback capacitor, and an organic light emitting element; the first transistor is used for transmitting a high level to a first pole of the feedback capacitor in a first reset phase, and the second transistor is used for transmitting an initial signal to a second pole of the feedback capacitor in the first reset phase; the first transistor is also used for transmitting a low level to the first pole of the feedback capacitor in the second reset phase, and the second transistor is also used for closing to enable the second pole of the feedback capacitor to float in the second reset phase; the second reset phase is located after the first reset phase; in a second reset stage, the potential variation of the first pole of the feedback capacitor is the difference between the high level and the low level, and the potential of the second pole of the feedback capacitor is the initial signal minus the potential variation.
Description
Technical Field
The present invention relates to an organic light emitting display device, and more particularly, to a pixel circuit of an organic light emitting display with high brightness and high resolution and a driving method thereof.
Background
An Organic Light-emitting display (OLED) device is a display that displays an image by driving each Organic Light-emitting cell with an electric current to excite an Organic component. Fig. 1 is a schematic diagram of a pixel circuit of an organic light emitting display device in the prior art, and fig. 2 is a driving schematic diagram of the pixel circuit shown in fig. 1. Before the next frame signal of the pixel circuit is written, the anode signal of the organic light-emitting element is reset to eliminate the voltage of the previous frame signal and ensure that the preset voltage is loaded without deviation. As shown in the figure, in the reset period reset time, the reset control signal AZ, the scan control voltage WS, and the light emitting control signal DS are all low potential, the transistors M4, M2, M3, and M1 are all turned on, the initial signal Vref is transmitted to the Anode of the organic light emitting element through the transistor M4, and the Anode signal of the organic light emitting element is reset. The pixel circuit shown in fig. 1 can operate normally in a positive voltage range, i.e., when the cathode potential of the organic light emitting device is 0V and the anode potential is greater than 0V.
For the high-brightness pixel circuit, the MVdevice (medium voltage device) is adopted, the working voltage range is limited, the voltage between the anode and the cathode of the organic light-emitting element is 8-10V, namely, the voltage difference between the anode and the cathode low potential ELVSS of the organic light-emitting element is even higher, and at the moment, the cathode low potential ELVSS of the organic light-emitting element is set to be negative voltage in order to meet the display requirement. In addition, the driving transistor M4 loses a voltage Vth when transmitting a potential, the voltage Vth is the threshold voltage of the transistor M4, and therefore the initial signal Vref must be greater than the threshold voltage Vth of the transistor M4, so that when the anode signal of the organic light emitting device is reset, the voltage difference between the initial signal Vref and the cathode low potential ELVSS of the organic light emitting device becomes larger because the cathode low potential ELVSS is a negative voltage, which causes the voltage across the organic light emitting device to be greater than or equal to the lighting voltage of the organic light emitting device, and causes the organic light emitting device to be still bright when the circuit is turned off, so that the contrast of the pixel decreases, and the lower the cathode low potential of the organic light emitting device, the lower the contrast of the pixel decreases.
Fig. 3 is a schematic diagram of a pixel circuit of a high-brightness organic light emitting display in the prior art. The operating voltage of the pixel circuit is between-p and + p, and-p is less than 0V. The cathode low potential-p 1 is a negative voltage, and in order to ensure that data of the next frame is correctly written, it is necessary to reset the anode signal of the organic light emitting element, and the voltage of the anode of the organic light emitting element after reset is identical to or close to the cathode low potential-p 1, so that it is necessary to use negative-p 2 as the initial signal. When the initial signal-p 2 is transmitted to the anode of the organic light emitting element, a large voltage difference is generated between the anode of the organic light emitting element and other points. When the cathode low potential-p 1 is less than-2V or lower, the voltage difference between the gate and the drain of the driving transistor M4, the voltage difference between the gate and the drain of the reset transistor M2, and the voltage difference between the gate and the source of the reset transistor M2 in the pixel circuit are excessive due to transient voltage, so that the transistors break down, and the pixel circuit fails. If the driving transistor M4 is configured as a separate NMOS or a separate PMOS of n-well, the risk of MV device breakdown is reduced to some extent, but the separate n-well or NMOS results in an increased size of the pixel circuit, which leads to a reduced resolution of the pixel.
Disclosure of Invention
The present invention provides a pixel circuit of an organic light emitting display device, including:
the organic light emitting diode comprises a first transistor, a second transistor, a feedback capacitor and an organic light emitting element, wherein a first pole of the feedback capacitor is connected to a drain electrode of the first transistor, a second pole of the feedback capacitor is connected to an anode of the organic light emitting element, and the anode of the organic light emitting element is also connected with a drain electrode of the second transistor;
the pixel circuit further comprises a third transistor, a driving transistor and a storage capacitor; a source of the third transistor is connected to a first pole of the storage capacitor, and a drain of the third transistor is connected to a source of the driving transistor; the drain electrode of the driving transistor is connected with the anode of the organic light-emitting element, and the grid electrode of the driving transistor is connected with the first electrode of the feedback capacitor; the second pole of the storage capacitor is connected with the first pole of the feedback capacitor;
the first transistor is used for transmitting a high level to a first pole of the feedback capacitor in a first reset phase, the second transistor is used for transmitting an initial signal to a second pole of the feedback capacitor in the first reset phase, and the initial signal is a positive voltage larger than 0 volt; the anode potential of the organic light emitting element is reduced from the high potential of the previous frame to the initial signal potential, and the potential difference between the high potential of the previous frame and the initial signal potential of the anode of the organic light emitting element is within the withstand voltage range of the second transistor and the driving transistor;
the first transistor is also used for transmitting a low level to the first pole of the feedback capacitor in a second reset phase, and the second transistor is also used for closing to enable the second pole of the feedback capacitor to float in the second reset phase; the second reset phase is after the first reset phase; in the second reset phase, the potential variation of the first pole of the feedback capacitor is the difference between the high level and the low level, the potential of the second pole of the feedback capacitor is an initial signal minus the potential variation, and the potential difference between the initial signal and (the initial signal minus the potential variation) is within the withstand voltage range of the second transistor and the driving transistor;
the value of the initial signal minus the potential change amount is equal to the cathode low potential of the organic light emitting element.
Optionally, the first transistor, the second transistor, the third transistor, and the driving transistor are transistors of the same kind, and bases of the first transistor, the second transistor, the third transistor, and the driving transistor are connected to the same potential.
Optionally, a source of the third transistor is connected to a power signal, a cathode of the organic light emitting element is connected to a cathode low potential, a voltage value of the power signal is greater than 0v, and a voltage value of the cathode low potential is less than 0 v.
Optionally, a data writing phase and a display phase after the second reset phase are further included;
in the data writing phase, the first transistor is used for transmitting a data control signal to the second pole of the storage capacitor; the third transistor is used for transmitting the power supply signal to the driving transistor;
in the display phase, the first transistor and the second transistor are turned off, the third transistor and the driving transistor are turned on, and the driving transistor generates a driving current and supplies the driving current to the organic light emitting element for driving the light emitting display of the organic light emitting element.
Optionally, the organic light emitting display device is a silicon-based organic light emitting display device.
The pixel circuit of the organic light-emitting display device provided by the invention firstly reduces the anode potential of the organic light-emitting element through the initial signal of positive voltage, and the voltage reduction range is within the voltage withstanding range of the transistor of the pixel circuit; then the voltage drop of one polar plate is fed back to the anode of the organic light-emitting element through the feedback capacitor, the anode potential of the organic light-emitting element is reduced again, and the voltage reduction range is within the voltage-resistant range of the pixel circuit transistor, so that the transistor of the pixel circuit is prevented from being broken down and losing efficacy, and the reliability of the pixel circuit is improved; on the other hand, the anode potential of the organic light emitting element is finally reduced to be consistent with the cathode potential, so that light leakage does not occur between the anode and the cathode, and the contrast of organic light emitting display is improved.
Drawings
FIG. 1 is a diagram illustrating a pixel circuit of an organic light emitting display device according to the prior art;
FIG. 2 is a driving timing diagram of the pixel circuit shown in FIG. 1;
FIG. 3 is a diagram of a pixel circuit of a high brightness organic light emitting display in the prior art;
FIG. 4 is a diagram of a pixel circuit according to an embodiment of the present invention;
FIG. 5 is a timing diagram of the driving of the pixel circuit shown in FIG. 4;
fig. 6 is a schematic diagram of a pixel circuit according to another embodiment.
Detailed Description
Example embodiments will now be described more fully with reference to the accompanying drawings. Example embodiments may, however, be embodied in many different forms and should not be construed as limited to the examples set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of example embodiments to those skilled in the art. Furthermore, the described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided to provide a thorough understanding of embodiments of the invention. One skilled in the relevant art will recognize, however, that the invention may be practiced without one or more of the specific details, or with other methods, components, devices, steps, and so forth. In other instances, well-known methods, devices, implementations or operations have not been shown or described in detail to avoid obscuring aspects of the invention.
The diagrams depicted in the figures are exemplary only, and do not necessarily include all of the contents and operations/steps, nor do they necessarily have to be performed in the order depicted. For example, some operations/steps may be decomposed, and some operations/steps may be combined, partially combined or adjusted to execute the steps, so that the actual execution order may be changed according to the actual situation.
Fig. 4 is a schematic diagram of a pixel circuit provided in an embodiment of the present invention, and as shown in fig. 4, the pixel circuit includes a first transistor M1, a second transistor M2, a feedback capacitor Cf, and an organic light emitting element OLED. Wherein a first pole N1 of the feedback capacitance Cf is connected to the drain of the first transistor M1, a second pole N2 of the feedback capacitance Cf is connected to the anode of the organic light emitting element OLED, and the anode of the organic light emitting element OLED is further connected to the drain of the second transistor M2. The gate of the first transistor M1 is connected to the Scan control signal Scan, the gate of the second transistor M2 is connected to the Reset signal Reset, and the source of the second transistor M2 is connected to the Initial signal Initial.
The pixel circuit provided by the invention has two stages of resetting, namely a first resetting stage T1 and a second resetting stage T2 positioned after the first resetting stage T1. In the first reset period T1, the first transistor M1 is used to transmit a high level DATA _ high to the first pole N1 of the feedback capacitor Cf, and the second transistor M2 is used to transmit an Initial signal Initial to the second pole N2 of the feedback capacitor Cf, where the Initial signal Initial is a positive voltage. In the embodiment shown in fig. 4, the first transistor M1 is turned on under the control of the Scan control signal Scan to transmit a high level signal to the first pole N1 of the feedback capacitor Cf; the second transistor M2 is turned on under the control of a Reset signal Reset, which transmits an Initial signal Initial to the second pole N2 of the feedback capacitor Cf. Alternatively, as shown in fig. 4, the high level signal may be provided for the DATA control signal DATA.
In the first period T1, the anode potential of the organic light emitting element OLED is lowered from the high potential displayed in the previous frame to the lower Initial signal potential, but is still at the positive potential. In the prior art, when the anode of the organic light emitting element OLED is reset to 0V or a negative voltage, an initial signal of 0V or a negative voltage is directly supplied to the anode of the organic light emitting element OLED. When the potential of the anode of the organic light emitting element OLED starts to be the high voltage of the previous frame of the display screen and the potential of 0V or the negative voltage of the initial signal is applied to the anode of the organic light emitting element OLED, the voltage difference to be borne by the second transistor is larger than the voltage withstanding range, and the second transistor may be broken down and fail. Similarly, when 0V or a negative voltage of the Initial signal Initial is directly applied to the anode of the organic light emitting element OLED, the voltage difference between the source and the drain of the driving transistor is too large to exceed the withstand voltage range of the driving transistor M4, and the driving transistor may be broken down. In the pixel circuit provided by the invention, in the first reset stage T1, a positive Initial signal Initial is provided to the anode of the organic light-emitting element OLED, and the source-drain voltage difference of the second transistor M2 and the driving transistor M4 does not exceed the withstand voltage range of the transistors, so that the problem of breakdown failure of the second transistor M2 and the driving transistor M4 is avoided, and the reliability of the organic light-emitting display device is improved.
In the second reset phase T2, the first transistor M1 is also used to transmit a low level DATA _ low to the first pole N1 of the feedback capacitor Cf, and the second transistor M2 is turned off to float the potential of the second pole N2 of the feedback capacitor Cf. In the embodiment shown in fig. 4, the first transistor M1 is turned on under the control of the Scan control signal Scan to transmit a low level to the first pole N1 of the feedback capacitor Cf, which may be provided by the DATA control signal DATA, and the second transistor M2 is turned off under the control of the Reset signal Reset, at which time the potential of the second pole N2 floats because the second pole N2 of the feedback capacitor Cf is no longer connected to the external voltage. In the second reset phase T2, the potential of the first pole N1 of the feedback capacitor Cf changes from high level DATA _ high to low level DATA _ low, and the change DATA _ high-DATA _ low is Δ V, because the potential of the second pole N2 is floating, under the influence of the feedback capacitor Cf, the first pole N1 will feed back the change Δ V to the second pole N2, the voltage of the second pole N2 will become the difference of the Initial signal Initial minus the change Δ V, i.e. the potential at the second pole N2 is decreased, and the difference of the Initial signal Initial minus the change Δ V is set to be equal to the voltage value of the cathode low potential Vss. The anode potential of the organic light emitting element OLED is lowered from the Initial signal Initial potential of the first reset period T1 to the cathode low potential Vss of a lower voltage, and the remaining electric charges are discharged, thereby completing the potential reset operation for the anode of the organic light emitting element OLED.
Alternatively, in another embodiment, the voltage value of the cathode low potential Vss of the cathode of the organic light emitting element OLED is less than 0V, that is, the operating voltage of the pixel circuit is between positive voltage and negative voltage, so that a higher voltage can be applied to the organic light emitting element OLED, and the brightness of the organic light emitting display device is higher. The pixel circuit described above is particularly suitable for such an organic light emitting display device having an operating voltage between a positive voltage and a negative voltage. In the prior art, since the transistor will generate the loss of threshold voltage when transmitting potential, the voltage value of the Initial signal Initial of the source of the second transistor M2 must be a positive voltage greater than the threshold voltage Vth, and in this case, if only the Initial signal Initial is used to reset the anode of the organic light emitting element OLED, the voltage difference between the positive voltage of the Initial signal Initial and the negative voltage of the cathode low potential Vss is large, so that the organic light emitting element OLED is driven to generate brightness in the reset phase, and the contrast is reduced. The pixel circuit provided by the embodiment of the invention can reduce the reset voltage, namely the voltage value of the Initial signal Initial, by delta V, when the cathode low potential Vss is a negative voltage, the difference value of the Initial signal Initial minus the potential variation delta V is equal to the voltage value of the cathode low potential Vss, and the voltage value is also a negative voltage, namely the negative voltage is used for resetting the anode of the organic light-emitting element OLED, so that the voltage difference between the anode and the cathode of the organic light-emitting element OLED is reduced, the organic light-emitting element OLED is prevented from generating brightness in the reset stage, and the contrast of the organic light-emitting display device is improved.
In still another embodiment, as shown in fig. 4, the pixel circuit further includes a third transistor M3, a driving transistor M4, and a storage capacitor Cs. The source of the third transistor M3 is connected to the first electrode O1 of the storage capacitor Cs, the drain of the third transistor M3 is connected to the source of the driving transistor M4, the gate of the third transistor M3 is connected to the emission control signal Emit, and the source of the third transistor M3 is connected to the power supply signal + p. The drain of the driving transistor M4 is connected to the anode of the organic light emitting element OLED, the gate of the driving transistor M4 is connected to the first plate N1 of the feedback capacitor Cf, the second electrode O2 of the storage capacitor Cs is also connected to the first plate N1 of the feedback capacitor Cf, and the cathode of the organic light emitting element OLED is connected to the cathode low potential-p. Fig. 5 is a driving timing diagram of a pixel circuit according to still another embodiment, and with reference to fig. 4 and 5, an operation timing of the pixel circuit according to still another embodiment of the present invention sequentially includes a first reset phase T1, a second reset phase T2, a data write phase T3, and a display phase T4.
In the first reset period T1, the Scan control signal Scan controls the first transistor M1 to be turned on, and the DATA control signal DATA outputs a high level DATA _ high to the first pole N1 of the feedback capacitor Cf; the Reset control signal Reset controls the second transistor M2 to be turned on, and the Initial signal Initial is transmitted to the second pole N2 of the feedback capacitor Cf; the emission control signal Emit controls the third transistor M3 to be turned off, while the driving transistor M4 is also in an off state. The anode potential of the organic light emitting element OLED is lowered from the high potential displayed in the previous frame to the lower Initial signal Initial potential, which is a positive potential, because the potential difference between the high potential of the organic light emitting element OLED in the previous frame and the Initial signal Initial is within the withstand voltage range of the second transistor M2 and the driving transistor M4, and thus the pixel circuit operates normally.
In the second reset period T2, the Scan control signal Scan controls the first transistor M1 to be turned on, and the DATA control signal DATA outputs a low level DATA _ low to the first pole N1 of the feedback capacitor Cf; the Reset control signal Reset controls the second transistor M2 to be turned off, and the second pole N2 of the feedback capacitor Cf does not generate potential suspension due to external potential connection; the emission control signal Emit still controls the third transistor M3 to be turned off, while the driving transistor M4 is also still in an off state. In the second reset phase T2, the potential of the first pole N1 of the feedback capacitor Cf changes from high level DATA _ high to low level DATA _ low, and the change amount DATA _ high-DATA _ low is Δ V, because the potential of the second pole N2 floats, the first pole N1 feeds back the change amount Δ V to the second pole N2 under the influence of the feedback capacitor Cf, and the voltage of the second pole N2 changes to the difference of the Initial signal Initial minus the change amount Δ V, i.e., the potential at the second pole N2 is decreased. The anode potential of the organic light emitting element OLED is lowered from the Initial signal Initial potential of the first reset period T1 to a lower Initial signal Initial-potential change amount Δ V, thereby completing the potential reset operation for the anode of the organic light emitting element OLED. And because the potential difference between the Initial signal Initial and the potential (Initial minus the potential variation Δ V) of the anode of the organic light emitting element OLED is within the withstand voltage range of the second transistor M2 and the driving transistor M4, the pixel circuit still operates normally, and the reliability of the pixel circuit is improved.
In the DATA writing phase T3, the Scan control signal Scan controls the first transistor M1 to be turned on, and the DATA control signal DATA writes the display signal; the Reset control signal Reset controls the second transistor M2 to be turned off, the emission control signal Emit controls the third transistor M3 to be turned on, and at this time, because the third transistor M3 is turned on, a large current flows on the organic light emitting element OLED branch, and the potential of the first pole N1 of the feedback capacitor Cf is not influenced by the feedback of the feedback capacitor Cf, and the voltage of the second Reset stage T2 is still kept at a low voltage.
In the light-emitting period T4, the Scan control signal Scan controls the first transistor M1 to turn off, but the DATA control signal DATA is already stored in the storage capacitor Cs during the DATA writing period T3, so the DATA control signal DATA can still control the gate of the driving transistor M4. The Reset control signal Reset controls the second transistor M2 to be turned off, the emission control signal Emit controls the third transistor M3 to be turned on, and the power voltage + p passes through the driving transistor M4 to generate a driving current, which is transmitted to the organic light emitting element OLED to drive the organic light emitting element OLED to Emit light for display.
It should be understood by those skilled in the art that the structure of the first transistor M1, the second transistor M2, the feedback capacitor Cf, and the organic light emitting device OLED and the feedback reset method in the pixel circuit provided by the present invention can be applied to other pixel circuits, and can reduce the anode potential of the organic light emitting device OLED from the high potential of the previous frame to the low potential lower than the Initial signal Initial, specifically, the difference between the Initial signal Initial and the potential variation Δ V subtracted by the difference between the high potential DATA _ high and the low potential DATA _ low provided by the first transistor M1, so as to discharge the residual charges on the anode of the organic light emitting device OLED and complete the reset.
Alternatively, the first transistor M1, the second transistor M2, the third transistor M3 and the driving transistor M4 are the same kind of transistors, and the base Vb1 of the first transistor M1, the base Vb2 of the second transistor M2, the base Vb3 of the third transistor M3 and the base Vb4 of the driving transistor M4 are connected to the same potential, so that separate wells are not used for isolation, the size of a pixel circuit is reduced, and the display resolution of the organic light-emitting display device can be improved.
Optionally, the voltage value of the power signal + p is greater than 0, and the voltage value of the cathode low potential-p is less than 0. In particular, the pixel circuit is operated between a positive voltage and a negative voltage. Compared with the pixel circuit with the working voltage between the positive voltage and the 0V voltage, the pixel circuit provided by the other embodiment of the invention can provide larger working voltage for the organic light-emitting element OLED, so that higher display brightness is achieved. For example, the voltage difference between the power signal + p and the cathode low potential-p can be set to be 8-10V.
Optionally, in one embodiment, the feedback capacitance Cf is a separate capacitive structure; as shown in fig. 6, in other embodiments, the feedback capacitance Cf may be a parasitic capacitance between the gate and the drain of the driving transistor M4. Because the driving transistor M4 is required to generate a driving current, the product of the communication length and the channel width is larger than that of other transistors, the driving transistor M4 is also larger than that of other transistors, the parasitic capacitance between the gate and the drain is also larger, and the requirement of the first plate N1 and the second plate N2 for feedback can be satisfied. The anode of the light emitting element OLED is reset by the feedback method, regardless of whether the feedback capacitance Cf is a separate capacitance structure or a parasitic capacitance between the gate and the drain of the driving transistor M4, which operates in the same manner.
Alternatively, the organic light emitting display device may be a silicon-based organic light emitting display device. The silicon-based organic light emitting display device is an organic light emitting display device which takes a monocrystalline silicon chip with a CMOS driving circuit as a substrate, can provide high resolution and high refresh frequency, has the characteristic of small size, and can be suitable for micro display. The pixel circuit has the advantage of small size, and is suitable for a silicon-based organic light-emitting display device.
The invention provides a pixel circuit of an organic light-emitting display device and an anode resetting method of an organic light-emitting element, firstly, the anode potential of the organic light-emitting element is reduced through an initial signal of positive voltage, and the voltage reduction range is within the voltage withstanding range of a transistor of the pixel circuit; then the voltage drop of one polar plate is fed back to the anode of the organic light-emitting element through the feedback capacitor, the anode potential of the organic light-emitting element is reduced again, and the voltage reduction range is within the voltage-resistant range of the pixel circuit transistor, so that the transistor of the pixel circuit is prevented from being broken down and losing efficacy, and the reliability of the pixel circuit is improved; on the other hand, the anode potential of the organic light emitting element is finally reduced to be consistent with the cathode potential, so that light leakage does not occur between the anode and the cathode, and the contrast of organic light emitting display is improved.
Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of the invention following, in general, the principles of the invention and including such departures from the present disclosure as come within known or customary practice within the art to which the invention pertains. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims. It will be understood that the invention is not limited to the precise arrangements described above and shown in the drawings and that various modifications and changes may be made without departing from the scope thereof. The scope of the invention is limited only by the appended claims.
Claims (5)
1. A pixel circuit of an organic light emitting display device, comprising:
the organic light emitting diode comprises a first transistor, a second transistor, a feedback capacitor and an organic light emitting element, wherein a first pole of the feedback capacitor is connected to a drain electrode of the first transistor, a second pole of the feedback capacitor is connected to an anode of the organic light emitting element, and the anode of the organic light emitting element is also connected with a drain electrode of the second transistor;
the pixel circuit further comprises a third transistor, a driving transistor and a storage capacitor; a source of the third transistor is connected to a first pole of the storage capacitor, and a drain of the third transistor is connected to a source of the driving transistor; the drain electrode of the driving transistor is connected with the anode of the organic light-emitting element, and the grid electrode of the driving transistor is connected with the first electrode of the feedback capacitor; the second pole of the storage capacitor is connected with the first pole of the feedback capacitor;
the first transistor is used for transmitting a high level to a first pole of the feedback capacitor in a first reset phase, the second transistor is used for transmitting an initial signal to a second pole of the feedback capacitor in the first reset phase, and the initial signal is a positive voltage larger than 0 volt; the anode potential of the organic light emitting element is reduced from the high potential of the previous frame to the initial signal potential, and the potential difference between the high potential of the previous frame and the initial signal potential of the anode of the organic light emitting element is within the withstand voltage range of the second transistor and the driving transistor;
the first transistor is also used for transmitting a low level to the first pole of the feedback capacitor in a second reset phase, and the second transistor is also used for closing to enable the second pole of the feedback capacitor to float in the second reset phase; the second reset phase is after the first reset phase;
in the second reset phase, the potential variation of the first pole of the feedback capacitor is the difference between the high level and the low level, the potential of the second pole of the feedback capacitor is an initial signal minus the potential variation, and the potential difference between the initial signal and (the initial signal minus the potential variation) is within the withstand voltage range of the second transistor and the driving transistor;
the value of the initial signal minus the potential change amount is equal to the cathode low potential of the organic light emitting element.
2. The pixel circuit according to claim 1, wherein the first transistor, the second transistor, the third transistor, and the driving transistor are the same kind of transistor, and bases of the first transistor, the second transistor, the third transistor, and the driving transistor are connected to the same potential.
3. The pixel circuit of the organic light emitting display device according to claim 2, wherein a source of the third transistor is connected to a power signal, a cathode of the organic light emitting element is connected to a cathode low potential, a voltage value of the power signal is greater than 0v, and a voltage value of the cathode low potential is less than 0 v.
4. The pixel circuit of the organic light emitting display device according to claim 3, further comprising a data writing phase and a display phase after the second reset phase;
in the data writing phase, the first transistor is used for transmitting a data control signal to the second pole of the storage capacitor; the third transistor is used for transmitting the power supply signal to the driving transistor;
in the display phase, the first transistor and the second transistor are turned off, the third transistor and the driving transistor are turned on, and the driving transistor generates a driving current and supplies the driving current to the organic light emitting element for driving the light emitting display of the organic light emitting element.
5. The pixel circuit of an organic light emitting display device according to claim 1, wherein the organic light emitting display device is a silicon-based organic light emitting display device.
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| CN111105749B (en) * | 2020-01-15 | 2022-10-25 | 京东方科技集团股份有限公司 | Pixel circuit, pixel driving method and display device |
| CN111477134B (en) * | 2020-04-30 | 2022-10-04 | 合肥鑫晟光电科技有限公司 | Detection method of substrate for display |
| CN114038367A (en) * | 2021-08-26 | 2022-02-11 | 重庆康佳光电技术研究院有限公司 | Pixel driving circuit, method, driving substrate and display panel |
| CN114155814B (en) * | 2021-12-09 | 2022-12-06 | 武汉天马微电子有限公司 | Pixel driving circuit, display panel and display device |
| CN114743505B (en) * | 2022-04-29 | 2023-06-27 | 武汉华星光电半导体显示技术有限公司 | Display device |
| CN116942169B (en) * | 2023-09-21 | 2024-02-02 | 之江实验室 | Miniaturized brain-computer signal amplifier and brain-computer interface chip system |
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