Pixel driving circuit, method, pixel structure and display panel

Abstract

The present invention proposes a pixel driving circuit, method, pixel structure and display panel, wherein the pixel driving circuit is connected to a plurality of organic light emitting diodes contained in a pixel; the pixel driving circuit includes a plurality of driving modules, and the driving modules are connected to the organic light emitting diodes in a one-to-one correspondence; the driving modules include an anode driving unit and a cathode driving unit; the anode driving unit is connected to the anode of the organic light emitting diode, and the cathode driving unit is connected to the cathode of the organic light emitting diode. By unifying the anode voltage when the organic light emitting diode is turned on, there will be no voltage difference between the anodes of adjacent organic light emitting diodes when there is a common layer, thereby preventing the current from being transmitted to the anodes of adjacent organic light emitting diodes through the common layer, avoiding lateral leakage, and ensuring the display effect.

Description

Technical Field

[0001] The present invention relates to the field of display, and in particular to a pixel driving circuit, method, pixel structure and display panel. Background Art

[0002] See also Figure 2 In the existing OLED (Organic Light-Emitting Diode) pixel structure, there is a common layer between OLEDs of different colors in a single pixel, such as a hole injection layer HIL and a hole transport layer HTL arranged between the light-emitting layer EML and the anode layer Anode; and due to the existence of the common layer, when the pixel emits light, the anodes of different OLEDs can be connected through the common layer, causing lateral leakage of current, thereby affecting the display effect of adjacent OLEDs. Summary of the invention

[0003] The main purpose of the present invention is to provide a pixel driving circuit, method, pixel structure and display panel, aiming to solve the problem of lateral leakage in the prior art.

[0004] To achieve the above object, the present invention provides a pixel driving circuit, wherein the pixel driving circuit is connected to a plurality of organic light emitting diodes included in a pixel; the pixel driving circuit comprises a plurality of driving modules, wherein the driving modules are connected to the organic light emitting diodes in a one-to-one correspondence; the driving modules comprise an anode driving unit and a cathode driving unit; the anode driving unit is connected to the anode of the organic light emitting diode, and the cathode driving unit is connected to the cathode of the organic light emitting diode; wherein:

[0005] The anode driving unit and the cathode driving unit are used to drive the organic light emitting diode to conduct;

[0006] In the pixel, the anode voltage of each organic light emitting diode is the same when it is turned on.

[0007] Optionally, the cathode driving unit includes a common voltage line, wherein:

[0008] The common voltage lines of the plurality of cathode driving units are connected to the cathodes of the plurality of organic light emitting diodes in a one-to-one correspondence; wherein:

[0009] In the pixel, the threshold voltage of each organic light emitting diode is equal to the sum of the cathode voltages on the corresponding common voltage line.

[0010] Optionally, the pixel comprises a red organic light emitting diode, a green organic light emitting diode and a blue organic light emitting diode; wherein:

[0011] The common voltage line connected to the cathode of the red organic light emitting diode is a first common voltage line, the common voltage line connected to the cathode of the green organic light emitting diode is a second common voltage line, and the common voltage line connected to the cathode of the blue organic light emitting diode is a third common voltage line.

[0012] Optionally, a first cathode voltage on the first common voltage line is greater than a second cathode voltage on the second common voltage line; and a second cathode voltage on the second common voltage line is greater than a third cathode voltage on the third common voltage line.

[0013] In addition, to achieve the above object, the present invention further provides a pixel driving method, which is applied to the pixel driving circuit as described above, and comprises:

[0014] Outputting cathode voltage to each cathode driving unit;

[0015] A data signal is output to the anode driving unit to drive the organic light emitting diode to be turned on, wherein in the pixel, the anode voltage of each organic light emitting diode is the same when it is turned on.

[0016] Optionally, the outputting cathode voltage to each cathode driving unit comprises:

[0017] Determining a cathode voltage corresponding to each common voltage line, wherein in the pixel, a threshold voltage of each organic light emitting diode is equal to a sum of cathode voltages on the corresponding common voltage line;

[0018] The cathode voltage is output to the corresponding common voltage line.

[0019] Optionally, determining the cathode voltage corresponding to each common voltage line includes:

[0020] Outputting the same data signal to each of the anode drive units, and outputting the same cathode voltage to each of the common voltage lines, so that each of the pixels does not emit light;

[0021] Synchronously reducing the cathode voltage output to each of the common voltage lines, and monitoring the display state of the pixel in real time;

[0022] When a red component appears in the display state of the pixel, the real-time cathode voltage is used as the first cathode voltage;

[0023] When a green component appears in the display state of the pixel, the real-time cathode voltage is used as the second cathode voltage;

[0024] When a blue component appears in the display state of the pixel, the real-time cathode voltage is used as the third cathode voltage.

[0025] In addition, to achieve the above-mentioned purpose, the present invention further provides a pixel structure, which is applied to the pixel driving circuit as described above, and comprises a cathode layer, an organic light-emitting layer arranged on the cathode layer, and an anode layer arranged on the organic light-emitting layer; wherein:

[0026] The anode layer includes a plurality of anode units, the cathode layer includes a plurality of cathode units, the organic light-emitting layer includes a plurality of light-emitting units of different colors, and the anode units, the cathode units and the light-emitting units are connected one by one;

[0027] The anode units are connected to the anode driving units in a one-to-one correspondence, and the cathode units are connected to the cathode driving units in a one-to-one correspondence.

[0028] In addition, to achieve the above objective, the present invention further provides a display panel, which includes a plurality of pixels and the pixel driving circuit as described above.

[0029] Optionally, the display panel further includes a plurality of common voltage lines; wherein:

[0030] The cathodes of the organic light emitting diodes with the same color in each of the pixels are connected to the same common voltage line.

[0031] The present invention proposes a pixel driving circuit, method, pixel structure and display panel, wherein the pixel driving circuit is connected to a plurality of organic light emitting diodes contained in a pixel; the pixel driving circuit includes a plurality of driving modules, and the driving modules are connected to the organic light emitting diodes one by one; the driving module includes an anode driving unit and a cathode driving unit; the anode driving unit is connected to the anode of the organic light emitting diode, and the cathode driving unit is connected to the cathode of the organic light emitting diode; wherein: the anode driving unit and the cathode driving unit are used to drive the organic light emitting diode to conduct; in the pixel, the anode voltage of each organic light emitting diode is the same when it is conducted. By unifying the anode voltage when the organic light emitting diode is conducted, there will be no voltage difference between the anodes of adjacent organic light emitting diodes when there is a common layer, thereby preventing the current from being transmitted to the anodes of adjacent organic light emitting diodes through the common layer, avoiding lateral leakage, and ensuring the display effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0033] Figure 1 A functional module diagram of an embodiment of a pixel driving circuit of the present invention;

[0034] Figure 2 It is a pixel structure diagram in the prior art;

[0035] Figure 3 The pixel driving circuit of the present invention is applied in Figure 1 Circuit structure diagram in the embodiment;

[0036] Figure 4 A schematic diagram of the voltage on the data line in the pixel driving circuit of the present invention;

[0037] Figure 5 A schematic diagram of a process flow of an embodiment of a pixel driving method of the present invention;

[0038] Figure 6 Schematic diagram of the pixel structure of the present invention.

[0039] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings.

[0040] Description of Figure Numbers:

[0041] DETAILED DESCRIPTION

[0042] It should be understood that the specific embodiments described herein are only used to explain the present invention, and are not used to limit the present invention.

[0043] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0044] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0045] In addition, the descriptions of "first", "second", etc. in the present invention are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in the field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0046] The present invention provides a pixel driving circuit, see Figure 1 , Figure 1 This is a functional module diagram of an embodiment of a pixel driving circuit of the present invention. In this embodiment, the pixel driving circuit is connected to multiple organic light-emitting diodes contained in a pixel; the pixel driving circuit includes multiple driving modules, and the driving modules are connected to the organic light-emitting diodes one by one; the driving modules include an anode driving unit and a cathode driving unit; the anode driving unit is connected to the anode of the organic light-emitting diode, and the cathode driving unit is connected to the cathode of the organic light-emitting diode; wherein:

[0047] The anode driving unit and the cathode driving unit are used to drive the organic light emitting diode to conduct;

[0048] In the pixel, the anode voltage of each organic light emitting diode is the same when it is turned on.

[0049] See also Figure 2 Due to the existence of the common layer, there is an electrically connected channel between the anodes of different organic light-emitting diodes in a single pixel through the common layer. It is understandable that due to material and process reasons, the threshold voltages of organic light-emitting diodes of different colors are different, and the cathodes of existing organic light-emitting diodes are all connected to a common line at the same time, that is, the cathode layer is shared. Therefore, the positive electrode voltages of organic light-emitting diodes of different colors are different when they are turned on again; and since there is an electrically connected channel between the positive electrodes of the organic light-emitting diodes through the common layer, that is, there is a voltage difference between the positive electrodes of the organic light-emitting diodes in the pixel, in this case, the current on the organic light-emitting diode with a higher positive electrode voltage will leak to the adjacent organic light-emitting diodes through the common layer, thereby causing the brightness of the organic light-emitting diode from which the current leakage is sourced to decrease, while the brightness of the organic light-emitting diode to which the current leakage flows increases or changes from non-luminous to luminous; resulting in a display color cast problem.

[0050] In this embodiment, by respectively setting an anode driving unit and a cathode driving unit for different OLEDs in the pixel, the OLEDs can be controlled independently; on this basis, the OLEDs are driven by the anode driving unit and the cathode driving unit so that the anode voltages of each OLED are the same when turned on. At this time, although the anodes of the OLEDs are still connected through a common layer, since the anode voltages of each OLED are consistent, there is no voltage difference between the anodes of the OLEDs, and therefore, the current will not be transmitted to the anodes of adjacent OLEDs through the common layer, thereby avoiding the occurrence of lateral leakage. It can be understood that since the light emission of the OLED is a current-type device, setting the anode voltages of each OLED to be the same will not affect the normal display of the OLED.

[0051] It should be noted that the anode driving unit is used to turn on based on the scanning signal, write the data signal when it is turned on, and output the driving current to the positive electrode of the OLED based on the data signal, so as to control the OLED to emit light; the specific structure of the anode driving unit can be set based on actual needs, such as 2T1C (2 TFTs + 1 capacitor), 6T1C (6 TFTs + 1 capacitor), 7T1C (7 TFTs + 1 capacitor) or other structures.

[0052] This embodiment unifies the anode voltage when the organic light emitting diodes are turned on, so that when a common layer exists, there will be no voltage difference between the anodes of adjacent organic light emitting diodes, thereby preventing current from being transmitted to the anodes of adjacent organic light emitting diodes through the common layer, avoiding lateral leakage, and ensuring the display effect.

[0053] Furthermore, the cathode driving unit includes a common voltage line, wherein:

[0054] The common voltage lines of the plurality of cathode driving units are connected to the cathodes of the plurality of organic light emitting diodes in a one-to-one correspondence; wherein:

[0055] In the pixel, the threshold voltage of each organic light emitting diode is equal to the sum of the cathode voltages on the corresponding common voltage line.

[0056] It can be understood that after the OLED is produced, its threshold voltage is determined; the cathode of the OLED is connected to the common voltage line, and the voltage on the common voltage line is the voltage of the cathode of the OLED; when the anode voltage and the cathode voltage of the OLED meet the threshold voltage, the OLED is turned on, and the voltage drop across the OLED is the threshold voltage of the OLED; therefore, the anode voltage of the OLED is the cathode voltage + the threshold voltage.

[0057] In this embodiment, different common voltage lines are set for different organic light emitting diodes, so that different cathode voltages can be set for different organic light emitting diodes; when the threshold voltage of the OLED is determined, by setting the cathode voltages of different OLEDs, the anode voltages of different OLEDs can be kept consistent when they are turned on.

[0058] Further, see Figure 3 , the pixel comprises a red organic light emitting diode OLED-R, a green organic light emitting diode OLED-G and a blue organic light emitting diode OLED-B; wherein:

[0059] The common voltage line connected to the cathode of the red organic light emitting diode OLED-R is the first common voltage line ELVSS-R, the common voltage line connected to the cathode of the green organic light emitting diode OLED-G is the second common voltage line ELVSS-G, and the common voltage line connected to the cathode of the blue organic light emitting diode OLED-B is the third common voltage line ELVSS-B.

[0060] Among them, DATA-R is the data line corresponding to the red organic light emitting diode OLED-R, DATA-G is the data line corresponding to the green organic light emitting diode OLED-G, and DATA-B is the data line corresponding to the blue organic light emitting diode OLED-B; SCAN (n) is the current row scan signal, SCAN (n-1) is the previous row scan signal, EM (n) out is the current row emission signal, ELVDD is the anode voltage signal, VINT1 is the first reset signal, and VINT2 is the second reset signal.

[0061] It is understandable that the materials and processes used for OLEDs of different colors are different, so the threshold voltages of OLEDs of different colors are often different; therefore, in this embodiment, the luminous color of the OLED is used as the classification condition for setting the cathode voltage, and the cathode voltages of OLEDs of different colors are set differently, thereby achieving the same positive voltage of OLEDs of different colors.

[0062] It can be understood that the display panel includes multiple pixels, and each pixel includes a red organic light emitting diode OLED-R, a green organic light emitting diode OLED-G and a blue organic light emitting diode OLED-B; therefore, when designing the circuit in the display panel, the cathode of the red organic light emitting diode OLED-R in each pixel can be connected to a first common voltage line ELVSS-R, the cathode of the green organic light emitting diode OLED-G in each pixel can be connected to a second common voltage line ELVSS-G, and the cathode of the blue organic light emitting diode OLED-B in each pixel can be connected to a third common voltage line ELVSS-B.

[0063] Further, the first cathode voltage on the first common voltage line ELVSS-R is greater than the second cathode voltage on the second common voltage line ELVSS-G; the second cathode voltage on the third common voltage line ELVSS-B is greater than the third cathode voltage on the third common voltage line.

[0064] In practical applications, the threshold voltage of the red organic light emitting diode OLED-R is generally smaller, the threshold voltage of the green organic light emitting diode OLED-G is larger, and the threshold voltage of the blue organic light emitting diode OLED-B is the largest; therefore, during the display process, if the red organic light emitting diode OLED-R is lit and at least one of the green organic light emitting diode OLED-G or the blue organic light emitting diode OLED-B is not lit, the current at the positive electrode of the red organic light emitting diode OLED-R will flow to the green organic light emitting diode OLED-G and the blue organic light emitting diode OLED-B. Since the threshold voltage of the green organic light emitting diode OLED-G or the blue organic light emitting diode OLED-B is higher, the leakage current is not enough to cause the green organic light emitting diode OLED-G or the blue organic light emitting diode OLED-B to light up. However, due to current leakage, the current at the positive electrode of the red organic light emitting diode OLED-R decreases, which will cause the brightness of the red organic light emitting diode OLED-R to decrease, resulting in color shift.

[0065] When the blue organic light emitting diode OLED-B is lit but the red organic light emitting diode OLED-R is not lit, the current at the positive electrode of the blue OELD will flow to the positive electrode of the red organic light emitting diode OLED-R. Since the threshold voltage of the red organic light emitting diode OLED-R is relatively small, the leaked current may cause the red organic light emitting diode OLED-R to light up, resulting in a reddish color. However, since the threshold voltages of the green organic light emitting diode OLED-G and the blue organic light emitting diode OLED-B are relatively close, the current leaked from the blue organic light emitting diode OLED-B to the green organic light emitting diode OLED-G is relatively small, and the green color cast is lighter.

[0066] When the green organic light-emitting diode OLED-G is on but the red organic light-emitting diode OLED-R is not lit, the current at the positive electrode of the green OELD will flow to the positive electrode of the red organic light-emitting diode OLED-R. Since the threshold voltage of the red organic light-emitting diode OLED-R is relatively small, the leaked current may cause the red organic light-emitting diode OLED-R to light up, resulting in a reddish color. However, since the threshold voltages of the green organic light-emitting diode OLED-G and the blue organic light-emitting diode OLED-B are relatively close, the current leaked from the green organic light-emitting diode OLED-G to the blue organic light-emitting diode OLED-B is less, and the blue color cast is lighter.

[0067] Therefore, the cathode voltage on the first common voltage line connected to the cathode of the red organic light emitting diode OLED-R, that is, the first cathode voltage, which is set in the present embodiment, has the largest value; the cathode voltage on the second common voltage line connected to the cathode of the green organic light emitting diode OLED-G, that is, the second cathode voltage, has a larger value; the cathode voltage on the third common voltage line connected to the cathode of the blue organic light emitting diode OLED-B, that is, the third cathode voltage, has the smallest value; thereby enabling the actual cathode voltage requirements of OLEDs of different colors to be matched.

[0068] Further, in the black state, that is, when the display screen is completely black, see Figure 4 Since the cathode voltages of the OLEDs in the prior art are consistent, the anode voltages will inevitably be inconsistent. Therefore, in order to make different OLEDs not emit light, the data line needs to output different voltage signals for OLEDs of different colors. At the same time, the red organic light emitting diodes OLED-R and the blue organic light emitting diodes OLED-B in different rows of the existing OLED display panel share the same data line. Therefore, the data signal transmitted by the shared data line needs to be the voltage V R The voltage V of the blue organic light emitting diode OLED-B B Make changes such as Figure 4 In the upper curve in the figure; in the present application, the anode voltages of the OLEDs are unified. Therefore, in the black state, the data lines can output the same data signal. In the case where the red organic light emitting diode OLED-R and the blue organic light emitting diode OLED-B share the data line, there is no need to adjust the voltage V for the red organic light emitting diode OLED-R. R The voltage V of the blue organic light emitting diode OLED-B B Make changes such as Figure 4 The lower curve in the figure; that is, the voltage on the shared data line can remain unchanged, and according to the electric work formula:

[0069]

[0070] Among them, W is electrical work, f is frequency, C is capacitance, and ΔV is voltage change; from the above formula, it can be seen that when the voltage on the data line does not need to change, the corresponding power consumption is 0, thus, unlike the existing technology, power consumption is reduced.

[0071] The present invention also protects a pixel driving method, which is applied to the pixel driving circuit as described above, see Figure 5 , the pixel driving method comprises:

[0072] Step S10, outputting cathode voltage to each cathode driving unit;

[0073] Step S20 , outputting a data signal to the anode driving unit to drive the organic light emitting diode to be turned on, wherein in the pixel, the anode voltage of each organic light emitting diode when turned on is the same.

[0074] In this embodiment, an anode driving unit and a cathode driving unit are respectively provided for different OLEDs in a pixel, so that the OLEDs can be controlled independently; on this basis, the OLEDs are driven by the anode driving unit and the cathode driving unit so that the anode voltages of the OLEDs are the same when they are turned on. At this time, although the anodes of the OLEDs are still connected through a common layer, Figure 3 Re1 and Re2 are equivalent resistances of the common layer; however, since the anode voltages of each OLED are the same, there is no voltage difference between the anodes of the OLEDs, so the current will not be transmitted to the anodes of adjacent OLEDs through the common layer, thereby avoiding the occurrence of lateral leakage. It is understandable that since the light emission of OLED is a current-type device, setting the anode voltages of each OLED to be the same will not affect the normal display of the OLED.

[0075] It is understandable that the cathode voltage is fixed, so after starting operation, the cathode voltage can be continuously output to the cathode driving unit; and the data signal needs to be determined based on the display data of the screen that actually needs to be displayed, and the data signal is sent to the anode driving unit after it is determined.

[0076] This embodiment unifies the anode voltage when the organic light emitting diodes are turned on, so that when a common layer exists, there will be no voltage difference between the anodes of adjacent organic light emitting diodes, thereby preventing current from being transmitted to the anodes of adjacent organic light emitting diodes through the common layer, avoiding lateral leakage, and ensuring the display effect.

[0077] Further, the outputting cathode voltage to each cathode driving unit comprises:

[0078] Determining a cathode voltage corresponding to each common voltage line, wherein in the pixel, a threshold voltage of each organic light emitting diode is equal to a sum of cathode voltages on the corresponding common voltage line;

[0079] The cathode voltage is output to the corresponding common voltage line.

[0080] It can be understood that after the OLED is produced, its threshold voltage is determined; the cathode of the OLED is connected to the common voltage line, and the voltage on the common voltage line is the voltage of the cathode of the OLED; when the anode voltage and the cathode voltage of the OLED meet the threshold voltage, the OLED is turned on, and the voltage drop across the OLED is the threshold voltage of the OLED; therefore, the anode voltage of the OLED is the cathode voltage + the threshold voltage.

[0081] In this embodiment, different common voltage lines are set for different organic light emitting diodes, so that different cathode voltages can be set for different organic light emitting diodes; when the threshold voltage of the OLED is determined, by setting the cathode voltages of different OLEDs, the anode voltages of different OLEDs can be kept consistent when they are turned on.

[0082] Further, determining the cathode voltage corresponding to each common voltage line includes:

[0083] Outputting the same data signal to each of the anode drive units, and outputting the same cathode voltage to each of the common voltage lines, so that each of the pixels does not emit light;

[0084] Synchronously reducing the cathode voltage output to each of the common voltage lines, and monitoring the display state of the pixel in real time;

[0085] When a red component appears in the display state of the pixel, the real-time cathode voltage is used as the first cathode voltage;

[0086] When a green component appears in the display state of the pixel, the real-time cathode voltage is used as the second cathode voltage;

[0087] When a blue component appears in the display state of the pixel, the real-time cathode voltage is used as the third cathode voltage.

[0088] It is understandable that the materials and processes used in OLEDs of different colors are different, so the threshold voltages of OLEDs of different colors are often different; in practical applications, the threshold voltage of red OLED is generally smaller, the threshold voltage of green OLED is larger, and the threshold voltage of blue OLED is the largest.

[0089] Therefore, in this embodiment, the same data signal is firstly output to each anode driving unit to make the anode conditions of each OLED consistent and avoid interfering with the determination of the cathode voltage. It can be understood that the data signal here can drive the OLED to emit light, and can be specifically set based on actual needs, such as using the data signal corresponding to the full white screen; at the same time, the same cathode voltage is output to each common voltage line to make the cathode voltage of each OLED the same; and in the initial state, the cathode voltage cannot turn on the OLED; then, the cathode voltage on each common voltage line is gradually reduced at the same time. As the cathode voltage is reduced, the voltage at both ends of the OLED gradually increases, and due to the red OLED, green OLED, and blue OLED The threshold voltage increases sequentially. Therefore, in the process of decreasing the cathode voltage, the red OLED, green OLED, and blue OLED will be turned on sequentially; when the cathode voltage drops to the point where the red component just appears, the red OLED is considered to be turned on, and the cathode voltage at this time is determined to be the first cathode voltage, that is, the voltage that needs to be output to the cathode of the red OLED; when the cathode voltage drops to the point where the green component just appears, the green OLED is considered to be turned on, and the cathode voltage at this time is determined to be the first cathode voltage, that is, the voltage that needs to be output to the cathode of the green OLED; when the cathode voltage drops to the point where the blue component just appears, the blue OLED is considered to be turned on, and the cathode voltage at this time is determined to be the first cathode voltage, that is, the voltage that needs to be output to the cathode of the blue OLED.

[0090] From the above content, it can be seen that the red OLED has the smallest threshold voltage and the largest cathode voltage is set for it; the green OLED has a larger threshold voltage and the larger cathode voltage is set for it, and the blue OLED has the largest threshold voltage and the smallest cathode voltage is set for it; the cathode voltages of OLEDs of different colors can just make the OLED turn on, and the sum of the cathode voltages and threshold voltages of OLEDs of different colors is the same, and is exactly the voltage of the positive electrode when the OLED is turned on.

[0091] It should be noted that the threshold voltage of the OLED is determined after production, therefore, the cathode voltage corresponding to the OLED can be determined after the threshold voltage of the OLED is determined; therefore, before the display panel is produced, the corresponding cathode voltage is first determined using the method of this embodiment, and the determined cathode voltage is set as the voltage output to the corresponding common voltage line; when it is used at the factory, the corresponding cathode voltage can be directly output.

[0092] In this embodiment, the first cathode voltage, the second cathode voltage, and the third cathode voltage can be accurately determined.

[0093] The present invention also protects a pixel structure, see Figure 6, the pixel structure is applied to the pixel driving circuit as described above, the pixel structure includes a cathode layer Cathode, an organic light emitting layer EML arranged on the cathode layer Cathode, and an anode layer Anode arranged on the organic light emitting layer EML; wherein:

[0094] The anode layer Anode includes a plurality of anode units, specifically, a blue anode unit Anode-B, a green anode unit Anode-G, and a red anode unit Anode-R; the cathode layer Cathode includes a plurality of cathode units, specifically, a blue cathode unit Cathode-B, a green cathode unit Cathode-G, and a red cathode unit Cathode-R; the organic light-emitting layer EML includes a plurality of light-emitting units of different colors, specifically, a blue light-emitting unit EML-B, a green light-emitting unit EML-G, and a red light-emitting unit EML-R, and the anode unit, the cathode unit, and the light-emitting unit are connected one-to-one based on color;

[0095] The anode units are connected to the anode driving units in a one-to-one correspondence, and the cathode units are connected to the cathode driving units in a one-to-one correspondence.

[0096] It is understandable that in the prior art, the cathode of the OLED in a single pixel is shared. Therefore, even if different common voltage lines are set for different OLEDs, the cathode voltages of different OLEDs will still be the same due to the shared cathode.

[0097] In order to solve this problem, in the present embodiment, the cathodes of the OLEDs within a single pixel are separately set. Specifically, a plurality of cathode units are set in the cathode layer. Different cathode units are connected to different light-emitting units. The light-emitting units are connected to corresponding common voltage lines based on the connected cathode units. This allows the cathode voltages of different OLEDs to be set independently, thereby achieving consistency in the anode voltage of the OLEDs.

[0098] It should be noted that, in this embodiment, the cathode layer is an independent cathode unit, and other structures of the pixel structure can be set based on actual needs. For example, in a feasible embodiment, the pixel may include a cathode layer Cathode, an electron injection layer EIL, an electron transport layer ETL, an organic light-emitting layer EML, a hole transport layer HTL, a hole injection layer HIL, and an anode layer Anode from bottom to top; wherein the electron injection layer EIL, the electron transport layer ETL, the organic light-emitting layer EML, the hole transport layer HTL, and the hole injection layer HIL are common layers, and the cathode layer Cathode, the organic light-emitting layer EML and the anode layer Anode are as described above and will not be repeated.

[0099] The present invention also protects a display panel, which includes a plurality of pixels and a pixel driving circuit. The structure of the pixel driving circuit can refer to the above embodiment and will not be described in detail here. As a matter of course, since the display panel of this embodiment adopts the technical solution of the above pixel driving circuit, the display panel has all the beneficial effects of the above pixel driving circuit.

[0100] Furthermore, the display panel further includes a plurality of common voltage lines; wherein:

[0101] The cathodes of the organic light emitting diodes with the same color in each of the pixels are connected to the same common voltage line.

[0102] It should be noted that, in this article, the terms "include", "comprises" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or system including a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or system. In the absence of further restrictions, an element defined by the sentence "includes a..." does not exclude the presence of other identical elements in the process, method, article or system including the element. The serial numbers of the above-mentioned embodiments of the present invention are for description only and do not represent the advantages and disadvantages of the embodiments.

[0103] The above are only preferred embodiments of the present invention, and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A pixel driving circuit, characterized in that: The pixel driving circuit is connected to a plurality of organic light emitting diodes included in one pixel; the pixel driving circuit includes a plurality of driving modules, and the driving modules are connected to the organic light emitting diodes one by one; the driving modules include an anode driving unit and a cathode driving unit; the anode driving unit is connected to the anode of the organic light emitting diode, and the cathode driving unit is connected to the cathode of the organic light emitting diode; wherein: The anode driving unit and the cathode driving unit are used to drive the organic light emitting diode to conduct; In the pixel, the anode voltages of the organic light emitting diodes are the same when they are turned on; The cathode driving unit comprises a common voltage line, wherein: The common voltage lines of the plurality of cathode driving units are connected to the cathodes of the plurality of organic light emitting diodes in a one-to-one correspondence; wherein: In the pixel, the threshold voltage of each organic light emitting diode is equal to the sum of the cathode voltages on the corresponding common voltage line.

2. The pixel driving circuit according to claim 1, characterized in that: The pixel comprises a red organic light emitting diode, a green organic light emitting diode and a blue organic light emitting diode; wherein: The common voltage line connected to the cathode of the red organic light emitting diode is a first common voltage line, the common voltage line connected to the cathode of the green organic light emitting diode is a second common voltage line, and the common voltage line connected to the cathode of the blue organic light emitting diode is a third common voltage line.

3. The pixel driving circuit according to claim 2, characterized in that: The first cathode voltage on the first common voltage line is greater than the second cathode voltage on the second common voltage line; the second cathode voltage on the second common voltage line is greater than the third cathode voltage on the third common voltage line.

4. A pixel driving method, characterized in that: The pixel driving method is applied to the pixel driving circuit according to any one of claims 1 to 3, and the pixel driving method comprises: Outputting cathode voltage to each cathode driving unit; A data signal is output to the anode driving unit to drive the organic light emitting diode to be turned on, wherein in the pixel, the anode voltage of each organic light emitting diode is the same when it is turned on.

5. The pixel driving method according to claim 4, characterized in that: The outputting cathode voltage to each cathode driving unit comprises: Determining a cathode voltage corresponding to each common voltage line, wherein in the pixel, a threshold voltage of each organic light emitting diode is equal to a sum of cathode voltages on the corresponding common voltage line; The cathode voltage is output to the corresponding common voltage line.

6. The pixel driving method according to claim 5, characterized in that: Determining the cathode voltage corresponding to each common voltage line includes: Outputting the same data signal to each of the anode drive units, and outputting the same cathode voltage to each of the common voltage lines, so that each of the pixels does not emit light; Synchronously reducing the cathode voltage output to each of the common voltage lines, and monitoring the display state of the pixel in real time; When a red component appears in the display state of the pixel, the real-time cathode voltage is used as the first cathode voltage; When a green component appears in the display state of the pixel, the real-time cathode voltage is used as the second cathode voltage; When a blue component appears in the display state of the pixel, the real-time cathode voltage is used as the third cathode voltage.

7. A pixel structure, characterized in that: The pixel structure is applied to the pixel driving circuit according to any one of claims 1 to 3, and the pixel structure comprises a cathode layer, an organic light-emitting layer arranged on the cathode layer, and an anode layer arranged on the organic light-emitting layer; wherein: The anode layer includes a plurality of anode units, the cathode layer includes a plurality of cathode units, the organic light-emitting layer includes a plurality of light-emitting units of different colors, and the anode units, the cathode units and the light-emitting units are connected one by one; The anode units are connected to the anode driving units in a one-to-one correspondence, and the cathode units are connected to the cathode driving units in a one-to-one correspondence.

8. A display panel, characterized in that: The display panel includes a plurality of pixels and a pixel driving circuit as claimed in any one of claims 1 to 3.

9. The display panel according to claim 8, wherein: The display panel further includes a plurality of common voltage lines; wherein: The cathodes of the organic light emitting diodes with the same color in each of the pixels are connected to the same common voltage line.

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