CN117935732A

CN117935732A - Dimming method of organic light-emitting display device

Info

Publication number: CN117935732A
Application number: CN202410280688.7A
Authority: CN
Inventors: 李玥; 黄鉴
Original assignee: Weidu Semiconductor Shanghai Co ltd
Current assignee: Weidu Semiconductor Shanghai Co ltd
Priority date: 2024-03-12
Filing date: 2024-03-12
Publication date: 2024-04-26

Abstract

The invention discloses a dimming method of an organic light emitting display device, which comprises the steps of generating an EM signal through modulating an EM_STV signal and a clock signal, wherein the EM_STV signal comprises a plurality of high-level pulses in one frame; the pulse width of one or more high-level pulses in the em_stv signal is changed with the period of the clock signal as a minimum unit when the DBV value is changed. The invention avoids DBV phenomenon in the EM signal modulation process, improves the smooth degree of dimming, and is suitable for different clock signal periods.

Description

Dimming method of organic light-emitting display device

Technical Field

The invention relates to the field of OLED display driving, in particular to a dimming method of an organic light-emitting display device.

Background

At present, in the field of OLED display (consumer product mobile phones, wearing, vehicle-mounted and the like), brightness adjustment mainly comprises three modes: AC dimming, DC dimming, AC/DC hybrid dimming.

DC dimming: the current of the light emission is usually adjusted by adjusting the source voltage, that is, the gate driving voltage in the pixel circuit, so as to adjust the brightness of the light emission of the OLED unit.

AC dimming: the source voltage is usually maintained unchanged, that is, the magnitude of the gate driving voltage and the current flowing through the OLED cells in the pixel circuit are not changed, but the effect of changing the brightness visually is achieved by means of black insertion. In general, the OLED display panel is realized by controlling the high-low level duty ratio of the EM signal. The OLED unit does not emit light when the EM signal is high, which is equivalent to black insertion, and emits light when the EM signal is low. The final brightness seen is the combined effect of both.

Fig. 1 is a schematic diagram of a dimming method, i.e., DC dimming, in which a brightness change is achieved by adjusting a data voltage (Vdata). Typically when the brightness is high; by adjusting the high-low duty cycle of the EM signal (Emit), AC dimming is the process. Typically used in medium to low brightness. Dimming can also be performed simultaneously by the data voltage and the EM signal at low brightness, i.e., AC/DC hybrid dimming. Fig. 2 shows a map of dimming modes when DBV (Display Brightness Value) are in different Gamma bands.

As shown in fig. 3, in the AC dimming phase, the light emitting time Duty (Duty for short) of the EM signal is adjusted according to the change of the DBV, and the light emitting time Duty may be represented by the high-low level Duty of the EM signal, specifically, the low level state of the OLED ON is represented by the percentage of the total time, that is: duty=t _B/(T_A+T_B) ×100%; the value range is 0-100%.

As shown in fig. 4, the Duty value may be changed by changing the pulse width of each EM signal high-level pulse within each frame, as in the shaded area of the figure. Multiple switching of the high level and the low level of the EM signal can be included in one frame, and the OLED cells emit light when the EM signal is low level, and the Pulse number is defined as the number of times the OLED cells emit light in one frame (i.e. the number of times of switching to the low level in one frame is equal to the number of pulses of the high level). At present, in applications such as mobile phones, at least 4 pulses of EM signals can be supported, and the number of pulses is usually 1-32.

In AC dimming, since the EM signal actually output is formed by modulation of the light emission start signal (em_stv signal) and the clock signal (clock signal and xclock signal), the Duty adjustment of the em_stv signal is not necessarily reflected on the EM signal (the case where it cannot be reflected is also called DBV). Taking the cycle of the clock signal as 4 rows (4H) as an example, as shown in fig. 5, since the rising and falling edges of the outputted EM signal are modulated by the clock signal and the xclock signal, respectively, even though the pulse width of the em_stv signal is 4H, the actual output is still 2H (similarly, the actual output is still 6H when the pulse width of the em_stv signal is 8H), so that if each pulse width is increased by 2H by mapping the DBV change to the em_stv signal, the output EM signal maintains the Duty value of the previous DBV, and no brightness adjustment is actually generated. For the case of 4 pulses per frame, if the DBV change is mapped to the em_stv signal and the total Pulse width change is 8H per frame, which is equally divided into 4 pulses, the output actual EM signal is still consistent with the previous one, the brightness is not changed, and the dimming smoothness is reduced.

The clock signals used by different GOAs (shift registers for EM signals) are usually of two cycles, namely 4H or 2H, depending on the circuit configuration and driving scheme. For different periods, the Duty adjustment mode of the same em_stv cannot be adopted, and the corresponding Duty adjustment mode needs to be set according to the period length of the clock signal so as to improve the dimming smoothness.

In addition, attention is paid to the Duty value and Pulse number adjustment method during the conversion between AC dimming and DC dimming. Otherwise, the DBV may be dropped.

Therefore, how to set the Duty adjustment mode of the em_stv signal avoids the occurrence of DBV phenomenon, improves the smooth degree of dimming, and is suitable for modulating different clock signal periods.

Disclosure of Invention

The invention aims to provide a dimming method of an organic light-emitting display device, which avoids DBV phenomenon, improves the dimming smoothness and is suitable for different clock signal periods.

In order to achieve the above object, the present invention provides a dimming method of an organic light emitting display device, including generating an EM signal by modulation of an em_stv signal and a clock signal, the EM signal being used to drive an OLED cell;

The em_stv signal includes a plurality of high-level pulses within one frame;

When the DBV value changes, acquiring the sum of pulse width change quantity of high-level pulses of each frame according to the change quantity of the DBV value, and changing the pulse width of one or more high-level pulses in the EM_STV signal by taking the period of the clock signal as a minimum unit according to the sum of pulse width change quantity.

Preferably, the pulse width of the high-level pulse is in the form of (a+b.n) H, wherein H is the duration corresponding to scanning one row of OLED cells, b is the period value of the clock signal when H is taken as a unit, n is an integer, and a is the basic pulse width value of the high-level pulse when H is taken as a unit; b/2.ltoreq.a.ltoreq.b, and the portion of a exceeding b/2 does not account for the sum of the pulse widths of the high-level pulses per frame.

Preferably, the pulse widths of the high-level pulses within each frame are different from each other by no more than one clock signal period.

Preferably, when the pulse widths of the high-level pulses are not all equal in one frame, the high-level pulses are set to have longer pulse widths in a skip interval manner.

Preferably, when the DBV value is kept unchanged and the pulse widths of the high-level pulses within one frame are not fully equal, the average pulse widths of the high-level pulses in the multiple frames tend to be equal by enabling pulse width dithering.

Another aspect of the present invention provides a dimming method of an organic light emitting display device, including generating an EM signal by modulation of an em_stv signal and a clock signal, the EM signal being used to drive an OLED cell;

The dimming method comprises a Fill-up phase dimming;

The em_stv signal includes at least one first high-level pulse and at least one second high-level pulse at the Fill-up phase dimming; the pulse width and the number of the first high-level pulses are kept unchanged in the Fill-up phase dimming;

The pulse width of the first high-level pulse is (a+b.n ₀) H, wherein H is the time length corresponding to scanning one row of OLED units, b is the period value of a clock signal when H is taken as a unit, n ₀ is a preset positive integer, and a is the basic pulse width value of the high-level pulse when H is taken as a unit; b/2 is less than or equal to a and less than or equal to b, and the part of a exceeding b/2 does not account for the sum of pulse width of high-level pulses of each frame; the pulse width of the second high-level pulse accords with the form of (a+b.k) H, wherein k is an integer and k is less than or equal to n ₀;

When the DBV value is changed during the Fill-up phase dimming, acquiring the pulse width sum variation of each frame of high-level pulse according to the variation of the DBV value; and increasing or decreasing the number of second high-level pulses with the pulse width as a basic pulse width value in the EM_STV signal according to the pulse width sum variation, and/or changing the pulse width of one or more second high-level pulses in the EM_STV signal by taking the period of the clock signal as a minimum unit.

Preferably, the dimming method further comprises Sequential phase dimming;

during the Sequential phase dimming, the em_stv signal includes a plurality of high-level pulses within a frame, and the pulse width of each high-level pulse conforms to the form of (a+b·n) H, n is an integer and n is not less than n ₀;

When the DBV value is changed during the Sequential phase dimming, acquiring the sum variation of pulse width of each frame of high-level pulse according to the variation of the DBV value; and changing the pulse width of one or more high-level pulses in the EM_STV signal by taking the period of the clock signal as a minimum unit according to the pulse width sum variation.

Preferably, during the Fill-up phase dimming, pulse widths of the second high-level pulses within each frame are different from each other by not more than one clock signal period; in the Sequential phase dimming, the pulse widths of the high-level pulses within each frame are different from each other by not more than one clock signal period.

Preferably, when the pulse widths of the second high-level pulses in one frame are not all equal, the second high-level pulses are set to have longer pulse widths in a skip interval manner; in the Sequential phase dimming, when the pulse widths of the high-level pulses are not fully equal in one frame, the high-level pulses are set to have longer pulse widths in a skip interval manner.

Preferably, when the DBV value remains unchanged and the pulse widths of the high-level pulses within one frame are not fully equal, the average pulse widths of the high-level pulses in the multiple frames tend to be equal by enabling pulse width dithering.

Preferably, when the DBV value is kept unchanged and the pulse widths of the second high-level pulses are not fully equal in one frame during the Fill-up phase dimming, the average pulse widths of the second high-level pulses in multiple frames tend to be equal by enabling pulse width dithering for the second high-level pulses.

Preferably, when the DBV value is kept unchanged and the pulse width of each second high-level pulse in one frame is not fully equal during the Fill-up phase dimming, pulse width dithering is started for each second high-level pulse, so that the average pulse width of each second high-level pulse in multiple frames tends to be equal; and when the DBV value is kept unchanged and the pulse widths of the high-level pulses in one frame are not fully equal during the Sequential phase dimming, the average pulse widths of the high-level pulses in multiple frames tend to be equal by starting pulse width dithering.

Preferably, the period of the clock signal is selected from 2H or 4H; the number of the first high-level pulses is 1.

Compared with the prior art, the invention has the following beneficial effects:

1. the invention considers the influence of the period of the clock signal when modulating the EM signal, and independently sets the pulse width of each high-level pulse in a frame in the multi-pulse occasion by setting the increasing and decreasing mode of the pulse width of the high-level pulse by taking the period of the clock signal as the minimum unit, thereby avoiding the occurrence of DBV phenomenon, improving the smooth degree of dimming and being applicable to different clock signal periods;

2. The invention makes the average value of the pulse width of the high level pulse in a plurality of frames uniform through the setting of the pulse width jitter, and makes the display effect more uniform.

Drawings

FIG. 1 is a schematic diagram of a driving method of an OLED unit according to the prior art;

FIG. 2 is a schematic diagram of a dimming mode in the prior art;

FIGS. 3 and 4 are prior art EM signal diagrams;

FIG. 5 is a schematic diagram showing DBV dropping in the prior art;

fig. 6 to 10 are schematic views of a first embodiment;

Fig. 11 to 13 are schematic views of a second embodiment;

In the figure: PVDD/PVEE: a first power supply voltage terminal and a second power supply voltage terminal; emit: an EM signal port; vdata: a data voltage signal terminal; id: a driving current; GB 1-GB 10: the maximum gray scale value of each Gamma Band corresponds to the brightness; nor1/HBM: typical luminance, high luminance mode luminance; A/B/T _A/T_B: high, low, high duration (i.e., pulse width of high pulse), low duration; em_stv: a light emission start signal; clock/Xclock: a clock signal; EM0/EM1: luminescence signal (EM signal); frame_k: a kth frame; high pulse sequence number #1/#2/#3/# 4.

Detailed Description

The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.

Example 1

The embodiment shows the Duty adjustment mode of em_stv when the clock signal period is 4H, where H is a time unit, and represents the duration corresponding to scanning one row of OLED units in the organic light emitting display device, and one frame time is the number of rows H of OLED units in the display device, so that the sum of pulse widths of high-level pulses required by the EM signal or the em_stv signal in one frame can be obtained by multiplying (100% -Duty) the number of rows of OLED units in the display device, and the sum of pulse widths is further distributed to one or more high-level pulses. Taking the gradual adjustment from high DBV to low DBV as an example, the AC dimming shown in this embodiment can be divided into two phases, one is a phase in which the em_stv signal varies from a smaller Pulse number (usually 1) to a larger Pulse number until the Pulse widths are equal, which is called a Fill-up phase, and the other is a phase in which the Pulse numbers are kept unchanged and the Pulse widths are gradually increased while being kept close to each other, which is called a Sequential phase. In other embodiments, one of the two adjustment modes may also be used alone for Duty adjustment of the em_stv signal throughout the AC dimming phase.

As shown in fig. 6, in the Fill-up phase, taking Pulse number of 4 as an example, the Pulse width of the initial (frame_0) 1 high level Pulse is (2+4n) H, and n is an integer. In the step-by-step regulation process, firstly, the high-level pulse with the lowest pulse width is added at the time node corresponding to each new pulse, then, the high-level pulse (frame_0-3) with the basic pulse width of 2H is added at the time node corresponding to the third (# 3), the second (# 2) and the fourth (# 4) high-level pulse in one frame, and then, the corresponding pulses are added with the pulse width of 4H (after frame_3) in sequence of the high-level pulses in sequence of #3, #2 and #4 until the pulse width of each high-level pulse reaches (2+4n) H. In the illustration of fig. 6, the Duty value of the em_stv signal decreases sequentially with each frame, each frame corresponds to the em_stv signal mapped by each DBV value at this stage, during the actual dimming process, the corresponding em_stv signal may be generated according to the target DBV value that is actually adjusted, that is, the pulse width (2+4n) H of the original pulse is maintained unchanged, the pulse width sum of each new pulse is allocated to the required change, the pulse width of each pulse is made to be in the form of (2+4k) H, k is an integer (the remainder of the remaining less than 4H after allocation may be discarded or complemented with 4H for processing), so that the accuracy of the pulse width sum adjustment, that is, the adjustment step length is 4H, and at this time, the Duty value of the stv_em signal is equal to the Duty value of the required EM signal output. In a preferred embodiment, the pulse widths of the new pulses differ by no more than 4H from each other; in other embodiments, multiple times 4H may be used, but the maximum pulse width does not exceed (2+4n) H. Since the pulse width adjustment step size is 2H and smaller during frames_0-3, frames_1-3 can also be combined into one adjustment step size, i.e. frame_0 is followed by the next DBV value directly corresponding to frame_3 and frames_1 and frame_2 are skipped. When the number of the newly added pulses increases more than 1 to 8, for example, the pulses may be added or widened at similar jump intervals, for example, in the order of #5, #3, #7, #2, #6, #4, #8 (# 1 to # 8) indicate the number of pulses in one frame, and the original pulses correspond to # 1).

As shown in fig. 7, in the Sequential phase, taking Pulse number as 4 as an example, the Pulse widths of the first 4 high-level pulses are (2+4n) H, n is an integer, and during the stepwise adjustment, frames_1 to 4 sequentially increase the Pulse widths of the high-level pulses by 4H in a frame at the jump intervals of #1, #3, #2, and # 4. The Duty value of the em_stv signal in the illustration of fig. 7 decreases sequentially with each frame, each frame corresponds to the em_stv signal mapped by each DBV value at this stage, and a corresponding em_stv signal may be generated according to the target DBV value actually adjusted during actual dimming, that is, the sum of pulse widths of the required changes is allocated to each high level pulse in a minimum unit of 4H (the remainder of less than 4H may be discarded or complemented to be processed as a 4H unit, so the adjustment step of the sum of pulse widths is 4H). In a preferred embodiment, the pulse widths of the high-level pulses differ from each other by no more than 4H; in other embodiments, multiple times 4H may also be used. For example, when the sum of pulse widths to be changed in each frame is 8H, the pulse width of 8H can be increased on the same pulse of the EM_STV signal, or two 4H pulse widths can be increased on two different pulses, and DBV phenomenon can not occur; in the prior art, the adjustment mode that the pulse width is equal distributes 4 pulses of 8H to EM_STV signals, and each pulse is increased by 2H, so that the EM signals are not actually changed, DBV is dropped, and the Duty value of the EM signals can be reduced only by increasing the pulse width sum of 16H. Therefore, the present embodiment has a smoother AC dimming effect at the time of the EM signal of multiple pulses, compared to the related art. In other embodiments, the Pulse number is other, for example, 8, and the Pulse width of each high-level Pulse may be increased in a similar jump interval during dimming, for example, the Pulse width of each high-level Pulse is increased by 4H in the sequence of #1, #5, #3, #7, #2, #6, #4, #8, and after the Pulse width sum is increased by 8H, the Pulse width of each high-level Pulse is respectively increased from (2+4n) H to (2+4n+4) H.

In a preferred embodiment, as shown in fig. 8, if the pulse widths of the high-level pulses are not fully equal in the period (DBV keep) where the DBV value is maintained, the display effect can be further homogenized by enabling pulse width dithering (dither on). The corresponding case where pulse width dithering is not enabled is denoted dither off. Specifically, when pulse width dithering is enabled, the pulse width values of the high-level pulses in the frames are exchanged or rotated in different frames, and the average pulse width of the high-level pulses in the frames is made to be equal when the pulse width sum in one frame is kept constant (corresponding to the Duty value). In the Sequential phase, since the pulse widths of the high-level pulses are similar, pulse width dithering can be performed on each high-level pulse, so that the average pulse widths of all the high-level pulses in multiple frames tend to be equal. As in the case of the 4-frame cycle at dither on shown in fig. 8, case1 is pulse width skip switching, and case2 is pulse width sequential switching; while dither off, the pulse width of each high level pulse is maintained unchanged for the lower 4 frames shown in fig. 8. In the Fill-up phase, the original high-level pulse is wider (called the first high-level pulse) and the newly added high-level pulse is narrower (called the second high-level pulse), so that the pulse width of the first high-level pulse can be kept unchanged, and only the second high-level pulse is subjected to pulse width dithering.

In another aspect, the pulse widths of the EM signals actually output when the high-level pulses of the em_stv signal are (2+4n) H, (2+4n+1) H or (2+4n+2) H are equal (i.e., duty is equal) due to the DBV phenomenon described above. As shown in fig. 9, the pulse width of the EM signal output when the high level pulse in the em_stv signal is the pulse width of 2H, 3H or 4H, respectively, is 2H; as shown in fig. 10, the pulse width of the EM signal output when the high level pulse in the em_stv signal is the pulse width of 6H, 7H or 8H, respectively, is 6H. Therefore, the aforementioned basic pulse width value of 2 may be replaced with 3 or 4, i.e., the pulse width requirement is (a+4n) H, a represents the number of basic pulse width lines, a=2, 3 or 4, but the Duty value is calculated or the portion of a exceeding 2 when the pulse width is calculated reversely from the Duty value should be ignored.

Example two

This embodiment shows the Duty adjustment mode of em_stv when the clock signal period is 2H. Also taking the gradual adjustment from a high DBV to a low DBV as an example, the AC dimming demonstrated in this embodiment can be divided into a Fill-up phase and a Sequential phase. In other embodiments, one of the two adjustment modes may also be used alone for Duty adjustment of the em_stv signal throughout the AC dimming phase.

As shown in fig. 11, in the Fill-up phase, taking Pulse number of 4 as an example, the Pulse width of the initial (frame_0) 1 high level Pulse is (1+2n) H, and n is an integer. In the step-by-step regulation process, the high-level pulse with the lowest pulse width is firstly added at the time node corresponding to each new pulse, then the high-level pulse (frame_0-3) with the basic pulse width of 1H is added at the time node corresponding to the third (# 3), the second (# 2) and the fourth (# 4) high-level pulse in one frame, and then the corresponding pulse is sequentially added with the pulse width of 2H (after frame_3) according to the sequence of the high-level pulses of #3, #2 and #4 until the pulse width of each high-level pulse reaches (1+2n) H. In the illustration of fig. 11, the Duty value of the em_stv signal decreases sequentially with each frame, each frame corresponds to the em_stv signal mapped by each DBV value at this stage, during the actual dimming process, the corresponding em_stv signal may be generated according to the target DBV value that is actually adjusted, that is, the pulse width (1+2n) H of the original pulse is maintained unchanged, the pulse width sum of each new pulse is allocated to the required change, the pulse width of each pulse is made to be in the form of (1+2k) H, k is an integer (the remainder of less than 2H remaining after allocation may be discarded or complemented with 2H for processing), so that the accuracy of the pulse width sum adjustment, that is, the adjustment step length is 2H, and at this time, the Duty value of the stv_em signal is equal to the Duty value of the required EM signal output. In a preferred embodiment, the pulse widths of the new pulses differ by no more than 2H from each other; in other embodiments, multiple times 2H may be used, but the maximum pulse width does not exceed (1+2n) H. Since the pulse width adjustment step size is 1H and smaller in the process of frames_0-3, frames_1-3 can also be combined into one adjustment step size, i.e. the next DBV value after frame_0 directly corresponds to frame_3 and frames_1 and frame_2 are skipped.

As shown in fig. 12, in the Sequential phase, taking Pulse number 4 as an example, the Pulse widths of the first 4 high-level pulses are (1+2n) H, n is an integer, and during the stepwise adjustment, frames_1 to 4 sequentially increase the Pulse widths of the high-level pulses by 2H in a frame at the jump intervals of #1, #3, #2, and # 4. The Duty value of the em_stv signal in the illustration of fig. 11 decreases sequentially with each frame, each frame corresponds to the em_stv signal mapped by each DBV value at this stage, and a corresponding em_stv signal may be generated according to the target DBV value actually adjusted during actual dimming, that is, the sum of pulse widths of the required changes is allocated to each high level pulse with 2H as the minimum unit (the remainder of less than 2H may be discarded or complemented to 2H units for processing, so the adjustment step length of the sum of pulse widths is 2H). In a preferred embodiment, the pulse widths of the high-level pulses differ from each other by no more than 2H; in other embodiments, multiple times 2H may also be used. This embodiment has a smoother AC dimming effect at multi-Pulse EM signals compared to the prior art.

In a preferred embodiment, as shown in fig. 13, if the pulse widths of the high-level pulses are not all equal in the period where the DBV value is maintained, the display effect can be further homogenized by enabling pulse width dithering (dither on). In the Sequential phase, because the pulse widths of all high-level pulses are similar, pulse width dithering can be carried out on all the high-level pulses, so that the average pulse widths of all the high-level pulses in multiple frames tend to be equal; in the Fill-up phase, the original high-level pulse is wider (called the first high-level pulse) and the newly added high-level pulse is narrower (called the second high-level pulse), so that the pulse width of the first high-level pulse can be kept unchanged, and only the second high-level pulse is subjected to pulse width dithering.

As can be seen from the first and second embodiments, the dimming method of the present invention is characterized in that, in the AC dimming process, if the em_stv signal involves a plurality of high level pulses in one frame, and the pulse width is changed, or the pulse width is changed from one high level pulse to a plurality of high level pulses in one frame, each pulse width is set to be in the form of (a+b·n) H, where b is the number of lines corresponding to the period of the clock signal used when modulating the EM signal, a is the number of lines corresponding to the basic pulse width, b/2 is less than or equal to a is less than or equal to b, and the portion of a exceeding b/2 does not account for the sum of pulse widths, and n is an integer. The value of a can be kept unchanged during actual dimming, the variation of the pulse width sum is calculated, and b H are used as minimum units to be distributed to each high-level pulse.

It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrative embodiments, and that the present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. Any reference sign in a claim should not be construed as limiting the claim concerned.

Furthermore, it should be understood that although the present disclosure describes embodiments, not every embodiment is provided with a separate embodiment, and that this description is provided for clarity only, and that the disclosure is not limited to the embodiments described in detail below, and that the embodiments described in the examples may be combined as appropriate to form other embodiments that will be apparent to those skilled in the art.

Claims

1. A dimming method of an organic light emitting display device, comprising generating an EM signal for driving an OLED cell by modulation of an em_stv signal and a clock signal, characterized by:

The em_stv signal includes a plurality of high-level pulses within one frame;

2. The dimming method according to claim 1, wherein the pulse width of the high-level pulse is in the form of (a+b·n) H, wherein H is a period corresponding to scanning one row of OLED cells, b is a period value of the clock signal when H is a unit, n is an integer, and a is a basic pulse width value of the high-level pulse when H is a unit; b/2.ltoreq.a.ltoreq.b, and the portion of a exceeding b/2 does not account for the sum of the pulse widths of the high-level pulses per frame.

3. A dimming method as claimed in claim 1, wherein the pulse widths of the high-level pulses within each frame differ from each other by no more than one clock signal period.

4. A dimming method as claimed in claim 3, wherein the high-level pulses are set to have a longer pulse width in a skip interval when the pulse widths of the respective high-level pulses are not fully equal within one frame.

5. A dimming method as claimed in claim 1, wherein when the DBV value is maintained and the pulse widths of the respective high-level pulses are not fully equal in one frame, the average pulse widths of the respective high-level pulses in the plurality of frames are made to be equal by enabling pulse width dithering.

6. A dimming method of an organic light emitting display device, comprising generating an EM signal for driving an OLED cell by modulation of an em_stv signal and a clock signal, characterized by:

Including Fill-up phase dimming;

7. A dimming method as claimed in claim 6, further comprising Sequential phase dimming;

8. The dimming method as claimed in claim 7, wherein the pulse widths of the respective second high-level pulses within each frame are different from each other by not more than one clock signal period at the time of the Fill-up phase dimming; in the Sequential phase dimming, the pulse widths of the high-level pulses within each frame are different from each other by not more than one clock signal period.

9. The dimming method according to claim 8, wherein the second high-level pulses are set to have longer pulse widths in a jump interval manner when pulse widths of the respective second high-level pulses are not fully equal in one frame at the time of the Fill-up phase dimming; in the Sequential phase dimming, when the pulse widths of the high-level pulses are not fully equal in one frame, the high-level pulses are set to have longer pulse widths in a skip interval manner.

10. The dimming method as claimed in claim 6, wherein when the DBV value is maintained and the pulse widths of the respective high-level pulses are not fully equal in one frame, the average pulse widths of the respective high-level pulses in the plurality of frames are made to be equal by enabling pulse width dithering.

11. The dimming method according to claim 6, wherein when the DBV value is maintained and the pulse widths of the respective second high-level pulses are not fully equal in one frame at the time of the Fill-up phase dimming, the average pulse widths of the respective second high-level pulses in the plurality of frames are made to tend to be equal by enabling pulse width dithering for the second high-level pulses.

12. The dimming method according to claim 7, wherein at the time of the Fill-up phase dimming, when the DBV value is kept unchanged and the pulse widths of the respective second high-level pulses are not fully equal in one frame, the average pulse widths of the respective second high-level pulses in the multiple frames are made to tend to be equal by enabling pulse width dithering for the second high-level pulses;

In the Sequential phase dimming, when the DBV value is kept unchanged and the pulse widths of the high-level pulses in one frame are not fully equal, the average pulse widths of the high-level pulses in multiple frames tend to be equal by starting pulse width dithering.

13. The dimming method as claimed in claim 6, wherein the period of the clock signal is selected from 2H or 4H; the number of the first high-level pulses is 1.