Driving method of organic light emitting diode display panel

Abstract

A driving method of an organic light emitting diode (OLED) display panel includes: receiving a plurality of input gray scales corresponding to a plurality of red, green and blue sub-pixels on the OLED display panel; enabling the input gray scale to correspond to a plurality of current indexes; calculating a representative current index according to the current index; comparing the representative current index with the critical current index; and in response to the representative current index being lower than the critical current index, generating a voltage compensation value according to the representative current index so as to move an initial voltage level used in an initial stage of the OLED display panel, and generating a plurality of gray scale compensation values according to the current index, and adjusting the input gray scale to a plurality of adjusted gray scale values corresponding to the red, green and blue sub-pixels. According to the driving method, the problem of color cast of the OLED display panel at a relatively low gray-scale value can be avoided.

Description

Technical Field

[0001] The present disclosure relates to a driving method, and more particularly to a driving method for driving an organic light emitting diode display panel. Background Art

[0002] In modern display devices, organic light-emitting diodes (OLED) are widely used in display screens. Unlike traditional LCD screen displays, each pixel of OLED emits light individually to achieve high contrast and bright colors. This self-luminous nature eliminates the need for a backlight, resulting in thinner, brighter and more responsive displays. OLED panels provide a wider viewing angle, better energy efficiency, and the possibility of manufacturing flexible, curved, and even transparent designs. OLED panels can be used in TVs, smartphones, wearable devices, etc., and have completely changed the visual experience of various devices through their high image quality and high design flexibility. Summary of the invention

[0003] An embodiment of the present disclosure provides a driving method for driving an organic light emitting diode (OLED) display panel, comprising: receiving a plurality of input grayscales corresponding to a plurality of red, green and blue sub-pixels on the OLED display panel; corresponding the input grayscales to a plurality of current indexes; calculating a representative current index based on the current index; comparing the representative current index with a critical current index; and in response to the representative current index being lower than the critical current index, generating a voltage compensation value based on the representative current index to move an initial voltage level used in an initial stage of the OLED display panel, and generating a plurality of grayscale compensation values ​​based on the current index to adjust the input grayscale to a plurality of adjusted grayscale values ​​corresponding to the red, green and blue sub-pixels.

[0004] In some embodiments of the driving method, the driving method further includes: in response to the representative current index being higher than the critical current index, generating a plurality of grayscale compensation values ​​to adjust a plurality of input grayscales without moving the initial voltage level.

[0005] In some embodiments of the driving method, the driving method further includes: in response to the representative current index being lower than the critical current index, a plurality of grayscale compensation values ​​are generated according to a plurality of current indexes, and further according to a frame refresh rate of the OLED display panel.

[0006] In some embodiments of the driving method, in response to the representative current index being lower than the critical current index, the generated plurality of grayscale compensation values ​​are positively correlated with the frame refresh rate.

[0007] In some embodiments of the driving method, the generated voltage compensation value is negatively correlated with the representative current index.

[0008] In some embodiments of the driving method, in response to the representative current index being lower than the critical current index, the voltage compensation value is generated according to the representative current index and further according to a frame refresh rate of the OLED display panel.

[0009] In some embodiments of the driving method, the generated voltage compensation value is positively correlated with the frame refresh rate.

[0010] In some embodiments of the driving method, the driving method is performed by a timing controller, which receives multiple input grayscales corresponding to multiple red, green and blue sub-pixels from an application processor (AP) or a system-on-chip (SoC).

[0011] In some embodiments of the driving method, the adjusted grayscale value is transmitted to a data driver to provide data voltages to a plurality of red, green, and blue sub-pixels.

[0012] In some embodiments of the driving method, the current index indicates the amplitudes of the plurality of light emitting currents flowing through the plurality of red, green and blue sub-pixels corresponding to the input grayscale.

[0013] In some embodiments of the driving method, the critical current index is determined by: receiving a plurality of historical grayscales of previous frames; mapping the plurality of historical grayscales to a plurality of historical current indexes; and selecting the critical current index according to a range of the plurality of historical current indexes in a statistical analysis.

[0014] In some embodiments of the driving method, the initial voltage level is used to reset anode voltages of a plurality of OLEDs before the light emitting phase.

[0015] In some embodiments of the driving method, the initial voltage level is used to reset gate voltages on driving transistors in the OLED driving circuits during the initial stage. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 FIG. 4 is a schematic diagram of sub-pixels on an organic light emitting diode display panel according to some embodiments of the present disclosure.

[0017] Figure 2 is a functional block diagram of an internal circuit of an organic light emitting diode display panel according to some embodiments of the present disclosure.

[0018] Figure 3 FIG. 1 is a schematic diagram showing the relationship between the brightness of one of red, green or blue and the brightness of white at different gray levels.

[0019] Figure 4is a flow chart of a driving method according to some embodiments of the present disclosure.

[0020] Figure 5 FIG. 4 is a schematic diagram of the structure of one of the red, green or blue sub-pixels according to some embodiments of the present disclosure.

[0021] Figure 6 for Figure 5 A signal waveform diagram showing the change of the anode voltage potential of an organic light emitting diode at different stages.

[0022] Figure 7 The figure is a schematic diagram showing the relationship between the brightness of one of red, green or blue after compensation at different gray levels.

[0023] Figure 8 for Figure 4 Flowchart of further steps for determining the current index in the driving method in .

[0024]

Explanation of symbols

[0025] 100:OLED display panel

[0026] P R ,P G ,P B :Red, green and blue sub-pixels

[0027] 120: Image data source

[0028] 140: Controller

[0029] 160: Data driver

[0030] GL R ,GL G ,GL B : Input grayscale value

[0031] AGL R ,AGL G ,AGL B : Adjusted grayscale value

[0032] V DATA :Data voltage

[0033] V ini : Initial voltage level

[0034] RL: Lower grayscale value area

[0035] RH: Higher grayscale value area

[0036] VDD, VSS: operating voltage

[0037] T1~T7: The first to seventh transistors

[0038] SCN n-1 ,SCN n :Scan signal

[0039] EM n : Luminescent signal

[0040] Cs: Capacitance

[0041] OL: Organic Light Emitting Diode

[0042] C OL : Parasitic capacitance

[0043] N AN : Anode of organic light emitting diode OL

[0044] P em : Luminous Stage

[0045] P ini : Initial stage

[0046] P sam : Sampling stage

[0047] ΔV C :Charging potential difference

[0048] V sat :Saturation voltage level

[0049] TE: Lighting stage P em Length of time

[0050] 200: Driving method

[0051] S210~S270: Steps DETAILED DESCRIPTION

[0052] The following will illustrate the embodiments of the present disclosure with reference to the accompanying drawings. In the accompanying drawings, the same reference numerals represent the same or similar elements or method flows.

[0053] refer to Figure 1 ,in Figure 1 Schematic diagram of sub-pixels on an organic light-emitting diode (OLED) display panel according to some embodiments of the present disclosure. Figure 1 As shown, the OLED display panel 100 includes a red sub-pixel P R , green sub-pixel P G and blue sub-pixel P B These red / green / blue (RGB) sub-pixels are arranged as pixels to display different colors. Figure 1In practical applications, the OLED display panel 100 is not limited to four pixels. Figure 2 ,in Figure 2 FIG. 1 is a functional block diagram of an internal circuit of an OLED display panel 100 according to some embodiments of the present disclosure. Figure 2 As shown, the OLED display panel 100 includes an image data source 120 , a controller 140 and a data driver 160 . The controller 140 is coupled between the image data source 120 and the data driver 160 .

[0054] In some embodiments, the image data source 120 provides a red sub-pixel P to be displayed on the OLED display panel 100. R , green sub-pixel P G and blue sub-pixel P B In some embodiments, the image data source 120 may be an application processor (AP) or a system-on-chip (SoC).

[0055] In some cases, the grayscale value GL may be converted into a data voltage V by a digital-to-analog converter (DAC) of the data driver 160. DATA , to control the red sub-pixel P R , green sub-pixel P G and blue sub-pixel P B brightness.

[0056] Due to the differences in process, the data voltage V DATA When the IR voltage drop is different, the sub-pixels at different positions may have different wiring resistance values ​​(that is, different IR voltage drops). In some cases, different IR voltage drops of different sub-pixels may cause color shift problems of the OLED display panel 100. In some embodiments, the controller 140 is used to receive the input grayscale value GL from the image data source 120, and adjust the input grayscale value GL to the adjusted grayscale value AGL, thereby compensating for the IR voltage drop to avoid the color shift problem of the OLED display panel 100. In some embodiments, the controller 140 can be implemented using a timing controller (TCON) of the OLED display panel 100.

[0057] It should be noted that the red sub-pixel P R , green sub-pixel P G and blue sub-pixel P B Can have different luminous efficiencies. Figure 3 ,in Figure 3The figure is a schematic diagram showing the relationship between the brightness of one of red, green or blue and the brightness of white at different gray levels. Figure 3 As shown, there are three brightness ratio curves L RED , L GREEN and L BLUE , corresponding to red, green and blue respectively.

[0058] According to the green brightness ratio curve L GREEN In the higher grayscale value region RH (brighter), for example, grayscale 30 to grayscale 255, the brightness of a pixel displaying green (for example, when the green sub-pixel PG emits light and other sub-pixels are turned off) can reach about 70% of the brightness of a pixel displaying white (for example, when the red, green and blue sub-pixels all emit light). RED In the higher grayscale value region RH, the brightness of the pixel displaying red is about 23% of the brightness of the pixel displaying white. BLUE In the higher grayscale value region RH, the brightness of the pixel displaying blue is approximately 7% of the brightness of the pixel displaying white.

[0059] In the higher grayscale value region RH, the green sub-pixel has the highest luminous efficiency; the red sub-pixel has a medium luminous efficiency; and the blue sub-pixel has the lowest luminous efficiency. Figure 3 As shown, in the higher grayscale value area RH, the brightness ratio curve L RED , L GREEN and L BLUE In some embodiments, when the grayscale value GL is located in the higher grayscale value region RH, the controller 140 can compensate for the IR drop based on the efficiency ratio of 23:70:7 and avoid the color shift problem.

[0060] On the other hand, in the lower grayscale value region RL (darker), the brightness ratio curve L RED , L GREEN and L BLUE Show different relationships. Figure 3 As shown, in the lower grayscale value area RL, the brightness ratio curve L RED , L GREEN and L BLUEThe grayscale values ​​of the lower grayscale value region RL and the grayscale values ​​of the lower grayscale value region RL are different, and no longer have a relatively stable efficiency ratio (about 23:70:7). For example, near the 10th grayscale in the lower grayscale value region RL, the efficiency of the green sub-pixel is improved, while the efficiency of the red sub-pixel is reduced to below the efficiency of the blue sub-pixel. In this case, if the input grayscale value GL in the lower grayscale value region RL is compensated in the same manner as the input grayscale value GL in the higher grayscale value region RH, a color shift problem of the OLED display panel 100 may be caused.

[0061] In some embodiments, the controller 140 compensates the input grayscale values ​​GL in the lower grayscale value region RL and the input grayscale values ​​GL in the higher grayscale value region RH using different methods.

[0062] Refer to Figure 4 ,in Figure 4 FIG. 2 is a flow chart of a driving method 200 according to some embodiments of the present disclosure. In some embodiments, the driving method 200 may be Figure 2 The controller 140 executes.

[0063] like Figure 2 and Figure 4 As shown, in step S210, the controller 140 receives the red, green and blue sub-pixels P corresponding to the display panel 100 from the image data source 120. R , P G and P B The input grayscale value GL.

[0064] In step S220, the controller 140 maps the input grayscale value GL to a current index. The current index indicates the current flowing through the red, green, and blue sub-pixels P corresponding to the input grayscale value GL. R , P G and P B The luminous current amplitude of the red, green and blue sub-pixels P R , P G and P B With different luminous efficiencies, different luminous current amplitudes may be required to emit different colors of light at the same grayscale value. In some embodiments, the mapping relationship between the input grayscale value GL and the current index is shown in Table 1:

[0065] Input Grayscale <![CDATA[P R Current Index]]> <![CDATA[P G Current Index]]> <![CDATA[P B Current Index]]> 0 0 0 0 … … … … 127 60 55 100 … … … … 255 200 150 500

[0066] Table 1

[0067] As shown in Table 1, when the red sub-pixel P to be displayed R The input grayscale value GL is 127, and its corresponding red sub-pixel P R The current index is 60; when the blue sub-pixel P to be displayedB The input grayscale value GL is 127, and its corresponding blue sub-pixel P B The current index is 100. This means that in order to achieve the brightness of the 127th grayscale, the blue sub-pixel P B In contrast, in order to achieve the brightness of the 127th grayscale, the red sub-pixel P R A smaller light-emitting current can be used.

[0068] In step S230, the controller 140 calculates a representative current index based on all current indexes corresponding to all sub-pixels. In some embodiments, the representative current index may be calculated based on the average of all current indexes. In some other embodiments, the representative current index may be calculated by summing up all current indexes. The representative current index is used to represent the total light emitting current used to drive the pixels in the entire OLED display panel 100 in one data frame.

[0069] In step S240, the controller 140 compares the representative current index with the critical current index. If the comparison result of step S240 shows that the representative current index is lower than the critical current index, it means that the OLED display panel 100 is currently displaying a frame with lower brightness, and the controller 140 executes step S250 to generate a voltage compensation value according to the representative current index. The voltage compensation value generated in step S250 is used to shift the initial voltage level V used in the initial stage of the OLED display panel 100. ini .

[0070] Refer to Figure 5 and Figure 6 . Figure 5 is a red, green or blue sub-pixel P according to some embodiments of the present disclosure. R , P G and P B A schematic diagram of the structure of one of them. Figure 6 for Figure 5 The signal waveform diagram of the change of the anode voltage level of the organic light emitting diode OL at different stages. Figure 5 As shown, the red, green and blue sub-pixels P R , P G and P B Each of the above can be realized by using seven transistors T1-T7 and a capacitor Cs (7T1C) to drive the organic light emitting diode OL. The organic light emitting diode OL has a parasitic capacitor C OL .like Figure 5 and Figure 6 As shown, in the light-emitting stage P em Initial stage before P ini In the process, transistors T4 and T7 are scanned by the scan signal SCN. n-1is turned on, and the initial voltage level is V ini will flow through transistors T4 and T7 to reset the gate terminal potential of transistor T1 and reset the anode N of the organic light emitting diode OL. AN Level. Figure 5 and Figure 6 As shown, in the initial stage P ini After the sampling stage P sam In the data voltage V DATA will flow through transistors T2, T1, and T3 to set the gate terminal potential of transistor T1 (for example, set to V DATA -V TH ).

[0071] It should be noted that Figure 5 The sub-pixel structure is only red, green and blue sub-pixels P R , P G and P B In some other embodiments, the initial voltage level V ini Other equivalent sub-pixel structures may also be used in the present disclosure.

[0072] like Figure 5 and Figure 6 As shown, in the sampling stage P sam After the light-emitting stage P em , the anode N of the organic light emitting diode OL AN The level will be changed by the light emitting current IL from the initial voltage level V ini The organic light emitting diode OL is charged to a saturation voltage level Vsat.

[0073] In the initial stage P ini After until the light is emitted, the anode N AN Maintain the initial voltage level V ini In order to ensure that the organic light emitting diode OL can emit light stably, the anode N of the organic light emitting diode OL must be AN From the initial voltage level V ini Charge to saturation voltage level V sat , so as to drive the organic light emitting diode OL into a saturation state. In other words, Figure 6 As shown, the charging potential difference ΔV C Should be:

[0074] ΔV C＝ V sat -V ini

[0075] Since the anode NAN is charged by the light-emitting current IL to a charging potential difference ΔV C , the actual charging potential difference ΔVC It can be expressed by the following formula:

[0076]

[0077] In the above formula, the actual charging potential difference ΔV C With the light-emitting current IL, light-emitting phase P em The length of time TE and the parasitic capacitance C of the organic light emitting diode OL OL Related.

[0078] When the input grayscale value GL is in the lower grayscale value region RL, the light emitting current IL will be relatively small. The smaller light emitting current IL will make the anode N AN It is more difficult to charge to the charging potential difference ΔV C In some embodiments, in step S250, the controller 140 generates a voltage level V for moving the initial voltage level according to the representative current index. ini In this case, the voltage compensation value is used to increase the initial voltage level V ini In some embodiments, the generated voltage compensation value is negatively correlated with the representative current index, as shown in Table 2:

[0079] Represents the current index Voltage compensation value <![CDATA[Initial voltage level V after movement ini <!-- 5 -->]]> 0 3.3 0V 20 2.8 -0.5V 40 2.3 -1V … … … 100 0 -3.3V

[0080] Table 2

[0081] In the example of Table 2, the voltage compensation value generated by the controller 140 is added to the initial voltage level (eg, -3.3V) to shift / increase the initial voltage level V ini In this case, due to the initial voltage level V ini Moved to the raised position, the anode N AN Charge to the expected charge potential difference ΔV C It will be simpler / faster and can ensure that the organic light emitting diode OL emits light in a saturated state.

[0082] In some other embodiments, in step S250, the voltage compensation value is generated according to the representative current index, and is further generated according to the frame refresh rate of the OLED display panel 100, as shown in Table 3:

[0083]

[0084] Table 3

[0085] It is worth noting that when the picture update rate is high, the light-emitting stage P em The shorter the time TE is, the more likely it is to be charged to the expected charging potential difference ΔV. CIn this case, the voltage compensation value generated by the controller 140 will be positively correlated with the frame refresh rate. When the frame refresh rate is high, the initial voltage level V ini will be raised to a higher level to compensate for the lighting stage P em A shorter time length TE.

[0086] In some embodiments, in step S260, the controller 140 generates a grayscale compensation value according to the current index to adjust the input grayscale value GL to the values ​​corresponding to the red, green, and blue sub-pixels P R , P G and P B In some embodiments, step S260 is to adjust the grayscale value AGL of the red, green and blue sub-pixels P R , P G and P B Generate grayscale compensation value. For the red sub-pixel P R The grayscale compensation value does not apply to the green sub-pixel P G Or blue sub-pixel P B Therefore, grayscale values ​​for different colors can be generated based on different compensation values. The adjusted grayscale value AGL is transmitted from the controller 140 to the data driver 160. According to the adjusted grayscale value AGL, the data driver 160 is used to provide a data voltage V DATA To the red, green and blue sub-pixels P R , P G and P B For example, the red sub-pixel P R The grayscale compensation value can be generated according to Table 4:

[0087] Current Index <![CDATA[P R Grayscale compensation value]]> 0 3 20 1 40 0 … … 100 -5

[0088] Table 4

[0089] For example, the green sub-pixel P G The grayscale compensation value can be generated from Table 5:

[0090] Current Index <![CDATA[P G Grayscale compensation value]]> 0 1 20 0 40 -1 … … 100 -8

[0091] Table 5

[0092] In some embodiments, in step S260, the grayscale compensation value is generated according to the current index, and further according to the refresh rate of the refreshed frame of the OLED display panel 100. For example, the red sub-pixel P R The grayscale compensation value can be generated according to Table 6:

[0093]

[0094] Table 6

[0095] It should be noted that when the picture update rate is high, the light-emitting stage P em The shorter the time TE is, the more likely it is to be charged to the expected charging potential difference ΔV. C In this case, the grayscale compensation value generated by the controller 140 will be positively correlated with the frame refresh rate. When the frame refresh rate is higher, the grayscale compensation value will become larger to compensate for the grayscale compensation value during the light-emitting stage P. em A shorter time length TE.

[0096] If the comparison result shows that the representative current index exceeds or is equal to the critical current index, it means that the OLED display panel 100 is currently displaying a frame with a higher brightness. Then, the controller 140 executes step S270 to generate a grayscale compensation value for adjusting the input grayscale value GL to the adjusted grayscale value AGL without moving the initial voltage potential V ini For example, the grayscale compensation value may be based on the red, green, and blue sub-pixels P R , P G and P B A relatively stable efficiency ratio (approximately 23:70:7) is generated.

[0097] Based on the above embodiment, when the input grayscale value GL is located in the lower grayscale value region RL, the controller 140 moves the initial voltage level and adjusts the grayscale to compensate. Figure 7 ,in Figure 7 The figure is a schematic diagram showing the relationship between the brightness of one of red, green or blue after compensation at different gray levels. Figure 7 As shown, the higher grayscale value area RH and the lower grayscale value area RL, the brightness ratio curve L RED , L GREEN and L BLUE In this case, for input grayscale values ​​in different regions, the red, green, and blue sub-pixels P R , P G and P B It can be driven to emit colored light with a stable efficiency ratio, thereby avoiding the color shift problem in the lower grayscale value area RL.

[0098] In some embodiments, Figure 4 The critical current index in step S240 may be determined based on historical image data of a plurality of previous frames. Figure 8 ,in Figure 8 FIG. 2 is a flow chart of more steps of determining a critical current index in the driving method 200 .

[0099] like Figure 8As shown, the driving method 200 may also include steps S201, S202 and S203. In step S201, the controller 140 receives historical grayscale values ​​of multiple previous frames. The historical grayscale values ​​reflect the brightness of multiple previous frames. In step S202, the controller 140 maps the historical grayscale values ​​to historical current indexes. The historical current index reflects the light-emitting current required for multiple previous frames to emit the expected brightness. In step S203, the controller 140 selects a critical current index based on a range of historical current indexes in the statistical analysis. For example, if the range of the historical current index is between 0 and 1000, the controller 140 may set the critical current index to 200, which is 20% of the range (0 to 1000). For example, if the range of the historical current index is between 50 and 500, the controller 140 may set the critical current index to 140, which is 20% of the range (50 to 500). The present disclosure is not limited to setting the critical current index to 20% of the range. In other cases, the critical current index may be 10%, 15%, 30% or 50% of the range. In some other embodiments, the critical current index may be set using other equivalent methods.

[0100] The above are merely preferred embodiments of the present disclosure. Various modifications and equivalent changes may be made to the present disclosure without departing from the scope or spirit of the present disclosure.

[0101] In summary, all modifications and equivalent changes made to the present disclosure within the scope of the claims are within the scope of the present disclosure.

Claims

1. A driving method for driving an organic light emitting diode (OLED) display panel, characterized in that: The driving method includes: receiving a plurality of input grayscales corresponding to a plurality of red, green, and blue sub-pixels on the OLED display panel; Mapping the input grayscale to a plurality of current indices; Calculating a representative current index according to the plurality of current indexes; comparing the representative current index with a critical current index; as well as In response to the representative current index being lower than the critical current index, a voltage compensation value is generated according to the representative current index to move an initial voltage level used in an initial stage of the OLED display panel, and a plurality of grayscale compensation values ​​are generated according to the current index to adjust the plurality of input grayscales to a plurality of adjusted grayscale values ​​corresponding to the plurality of red, green and blue sub-pixels.

2. The driving method according to claim 1, characterized in that: Also includes: In response to the representative current index being higher than the critical current index, the plurality of grayscale compensation values ​​are generated to adjust the plurality of input grayscales without moving the initial voltage level.

3. The driving method according to claim 1, characterized in that: In response to the representative current index being lower than the critical current index, the plurality of grayscale compensation values ​​are generated according to the plurality of current indexes and further according to a frame refresh rate of the OLED display panel.

4. The driving method according to claim 3, characterized in that: In response to the representative current index being lower than the critical current index, the generated plurality of grayscale compensation values ​​are positively correlated with the frame refresh rate.

5. The driving method according to claim 1, characterized in that: The generated voltage compensation value is negatively correlated with the representative current index.

6. The driving method according to claim 1, characterized in that: In response to the representative current index being lower than the critical current index, the voltage compensation value is generated according to the representative current index and further according to a frame refresh rate of the OLED display panel.

7. The driving method according to claim 6, characterized in that: The generated voltage compensation value is positively correlated with the frame refresh rate.

8. The driving method according to claim 1, characterized in that: The driving method is executed by a timing controller, which receives the plurality of input grayscales corresponding to the plurality of red, green and blue sub-pixels from an application processor (AP) or a system-on-chip (SoC).

9. The driving method according to claim 1, characterized in that: The adjusted grayscale value is transmitted to a data driver to provide data voltages to the plurality of red, green and blue sub-pixels.

10. The driving method according to claim 1, characterized in that: The current index indicates amplitudes of a plurality of light emitting currents flowing through the plurality of red, green and blue sub-pixels corresponding to the input grayscale.

11. The driving method according to claim 1, characterized in that: The critical current index is determined by the following method: Receiving a plurality of historical grayscales of a plurality of previous frames; Mapping the plurality of historical grayscales to a plurality of historical current indexes; and The critical current index is selected according to a range of the plurality of historical current indexes in the statistical analysis.

12. The driving method according to claim 1, characterized in that: The initial voltage level is used to reset anode voltages of a plurality of OLEDs before a light emitting phase.

13. The driving method according to claim 1, characterized in that: The initial voltage level is used to reset gate voltages on driving transistors in OLED driving circuits during the initial stage.

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