JP2008304491A - Display panel driving method, display device, display panel driving device, and electronic device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a peak brightness level control method capable of reducing flickering and moving-image blurring even in the case of widely varying a light emission period. <P>SOLUTION: Regarding the method for variably controlling the peak brightness level of a display panel by controlling the total length of light emission period within a single-field period, in the case N light emission periods are set within the single-field period (N≥2), at least one interval between starting timings of the adjacent light emission periods is controlled so as to become shorter than a period length obtained by dividing the single-field period into N equal lengths. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

The invention described in this specification relates to a technique for controlling the peak luminance level of a display panel.
Note that the invention has aspects as a display panel driving method, a display device, a display panel driving device, and an electronic apparatus.

  In recent years, a self-luminous display device in which organic EL (Electro Luminescence) elements are arranged in a matrix has been developed. A display panel using an organic EL element (hereinafter also referred to as an “organic EL panel”) is easy to be reduced in weight and thinned, and has a high response speed and excellent moving image display characteristics.

  By the way, there are a passive matrix method and an active matrix drive method as a driving method of the organic EL panel. Recently, active matrix drive type display panels in which an active element (thin film transistor) and a capacitor are arranged for each pixel circuit are being actively developed.

  FIG. 1 shows a configuration example of an organic EL panel corresponding to the function of changing the light emission period. The organic EL panel 1 includes a pixel array unit 3, a first scanning line driving unit 5 for writing signal voltage, a second scanning line driving unit 7 for controlling a light emission period, and a data line driving unit 9. In the pixel array unit 3, pixel circuits 11 are arranged in M rows × N columns. M and N are determined according to the display resolution.

  Note that the scanning line VSCAN1 in the drawing is a wiring for giving a signal voltage write timing. A scanning line VSCAN2 in the drawing is a wiring that gives the start timing and end timing of the light emission period. A signal line Vsig in the drawing is a wiring for applying a signal voltage corresponding to pixel data.

FIG. 2 shows a configuration example of the pixel circuit 11 corresponding to the variable function of the light emission period. Various circuit configurations have been proposed for the pixel circuit 11. FIG. 2 shows one of these simplest circuit configurations.
The pixel circuit 11 in FIG. 2 includes a write control element T1, a current drive element T2, a light emission period control element T3, a storage capacitor Cs, and an organic EL element OLED.

In the case of FIG. 2, an N-channel thin film transistor is used for the write control element T1, a P-channel thin film transistor is used for the current driving element T2, and an N-channel thin film transistor is used for the light emission period control element T3.
Here, the operating state of the write control element T1 is controlled by the first scanning line VSCAN1 connected to the gate electrode. When the write control element T1 is in the on state, a signal voltage corresponding to the pixel data is written to the storage capacitor Cs through the signal line Vsig.

The signal voltage after writing is held in the holding capacitor Cs for one field. The signal voltage held in the holding capacitor Cs corresponds to the gate-source voltage Vgs of the current driving element T2.
Accordingly, a drain current Ids having a magnitude corresponding to the magnitude of the signal voltage held in the holding capacitor Cs flows through the current driving element T2. As the drain current Ids increases, the current flowing through the organic EL element OLED increases and the emission luminance increases.

  However, the supply and stop of the drain current Ids to the organic EL element OLED is controlled by the light emission period control element T3. That is, the organic EL element OLED emits light only during the period in which the light emission period control element T3 is in the on state. The operating state of the light emission period control element T3 is controlled by the second scanning line VSCAN2.

  In addition, a pixel circuit having the circuit configuration shown in FIG. 3 is also used for the pixel circuit 11 corresponding to the variable function of the light emission period. The pixel circuit 11 shown in FIG. 3 corresponds to a pixel circuit that controls supply and stop of the drain current Ids to the organic EL element OLED by variably controlling the voltage of the power supply line to which the current driving element T2 is connected. The pixel circuit 11 shown in FIG. 3 includes a write control element T1, a current drive element T2, a storage capacitor Cs, and an organic EL element OLED.

  In the case of FIG. 3, the power supply line to which the source electrode of the current driving element T2 is connected corresponds to the second scanning line VSCAN2. A high potential power supply voltage VDD or a low potential power supply voltage VSS2 (<VSS1) is supplied to the second scanning line VSCAN2. The organic EL element OLED emits light while the high-potential power supply voltage VDD is supplied, and the organic EL element OLED is turned off while the low-potential power supply voltage VSS2 is supplied.

4 and 5 show the relationship between the voltage applied to the first scanning line VSCAN1 and the second scanning line VSCAN2 and the driving state of the corresponding pixel. 4 shows the relationship when the light emission period is long, and FIG. 5 shows the relationship when the light emission period is short.
4 and 5 show the relationship between the applied voltage and the driving state corresponding to the pixel circuits 11 from the first row to the third row of the pixel array section 3. FIG. That is, the numbers in parentheses indicate the corresponding line positions.

As shown in FIGS. 4 and 5, the period when both the first scanning line VSCAN1 and the second scanning line VSCAN2 are at the L level corresponds to the extinguishing period.
The period in which the first scanning line VSCAN1 is at the H level and the second scanning line VSCAN2 is at the L level corresponds to the signal voltage writing period.
Further, the period in which the first scanning line VSCAN1 is at the L level and the second scanning line VSCAN2 is at the H level corresponds to the light emission period.

The reason why the pixel circuit 11 is provided with the variable function of the light emission period in this way is because there are several advantages as described below.
One advantage is that the peak luminance level can be adjusted without changing the amplitude of the input signal. FIG. 6 shows the relationship between the light emission period length and the peak luminance level in one field period.

  As a result, when the input signal is a digital signal, the peak luminance level can be adjusted without reducing the number of gradations of the signal. Further, when the input signal is an analog signal, the signal amplitude does not decrease, so that noise resistance can be increased. As described above, the variable control of the light emission period length is effective for realizing a pixel circuit capable of adjusting the peak luminance with high image quality.

In addition, the variable control of the light emission period length has an effect of shortening the writing time by increasing the writing current value in the case of a current writing type pixel circuit.
Further, the variable control of the light emission period length has an effect of improving the quality of the moving image. This effect will be described with reference to FIGS. In addition, each horizontal axis of FIGS. 7-9 shows the position in a screen, and a vertical axis | shaft shows elapsed time. Both represent the movement of the viewpoint when the bright line moves within the screen.

FIG. 7 shows display characteristics of a hold-type display in which the light emission period is given as 100% of one field period. A typical example of this type of display device is a liquid crystal display.
FIG. 8 shows the display characteristics of an impulse-type display whose light emission period is sufficiently shorter than one field period. A typical example of this type of display device is a CRT (Cathode Lay Tube) display.

FIG. 9 shows display characteristics of a hold-type display in which the light emission period is limited to 50% of one field period.
As can be seen by comparing FIGS. 7 to 9, when the light emission period is 100% of one field period (FIG. 7), a phenomenon that the display width appears wide when the bright spot is moved (that is, moving image blur) is easily perceived. Become.

On the other hand, when the light emission period is sufficiently short with respect to one field period (FIG. 8), the display width remains short even when the bright spot moves. That is, moving image blur is not perceived.
When the light emission period is 50% of one field period (FIG. 9), the spread of the display width can be suppressed even when the bright spot is moved, and the motion blur can be reduced accordingly.

  In general, in the case of a moving image in which one field period is given at 60 Hz, it is known that the moving image characteristic is remarkably deteriorated when the light emission period is 75% or more of one field period, and the light emission period is less than 50% of one field period. It is considered preferable to suppress it.

  10 and 11 show examples of driving timing of the second scanning line VSCAN2 when the light emission period within one field period is one time. FIG. 10 is an example of drive timing when the light emission period within one field period is 50%, and FIG. 11 is an example of drive timing when the light emission period within one field period is 20%. FIGS. 10 and 11 show that the phase relationship makes a round with 20 lines.

  The light emission period corresponding to the sth scanning line VSCAN2 (s) can be given by the following equation. However, it is assumed that one field period is given by m horizontal scanning periods, and the sth scanning line VSCAN2 (s) is subjected to a writing operation during the sth horizontal scanning period and starts to emit light simultaneously. And Further, the ratio of the light emission period in one field period T is represented by DUTY.

At this time, the light emission period and the extinguishing period are respectively given by the following equations.
Light emission period: [(s-1) / m] · T <t <{[(s-1) / m] + DUTY} · T
Light-off period: {[(s-1) / m] + DUTY} · T <t <{[(s-1) / m] +1} · T
However, t satisfies the following period.
[(S-1) / m] · T <t <{[(s-1) / m] +1} · T

Special table 2002-514320 gazette Japanese Patent Laid-Open No. 2005-027028 JP 2006-215213 A

  However, when a light emission period and a light extinction period are provided in one field period, suppression of flicker becomes a new technical problem. In general, in the case of a moving image in which one field period is given at 60 Hz, it is known that flicker becomes particularly apparent when the light emission period is less than 25% of one field period, and the light emission period is 50% or more of one field period. It is said that it is preferable.

That is, it is known that there is a trade-off relationship between the moving image quality and flicker in the light emission period restriction, and the setting range is restricted. However, this limitation of the setting range leads to limiting the variable range of the peak luminance level.
Therefore, as a method of reducing flicker when the light emission period is short, a method of dividing the light emission period within one field period into a plurality of times has been proposed.

12 and 13 show the relationship between the voltage applied to the first scanning line VSCAN1 and the second scanning line VSCAN2 and the driving state of the corresponding pixel. 12 shows the relationship when the light emission period is long, and FIG. 13 shows the relationship when the light emission period is short.
12 and 13 show the relationship between the applied voltage and the driving state corresponding to the pixel circuits 11 from the first row to the third row of the pixel array section 3. That is, the numbers in parentheses indicate the corresponding line positions.

  FIG. 14 and FIG. 15 show driving timing examples of the second scanning line VSCAN2 when the light emission period in one field period is twice. In the existing driving method shown in FIGS. 14 and 15, one field is divided into a first half period and a second half period, and the light emission period length is varied for each period. That is, in the first half period, the light emission period length is varied based on 0% of one field period, and in the second half period, the light emission period length is varied based on 50% of one field period.

  14 is an example of drive timing when the total light emission period within one field period is 50%, and FIG. 15 is an example of drive timing when the total light emission period within one field period is 20%. 14 and 15 also show that the phase relationship makes a full circle with 20 lines.

  When the light emission period in one field period is twice, the light emission period corresponding to the sth scanning line VSCAN2 (s) can be given by the following equation. However, it is assumed that one field period is given by m horizontal scanning periods, and the sth scanning line VSCAN2 (s) is subjected to a writing operation during the sth horizontal scanning period and starts to emit light simultaneously. And Further, the ratio of the light emission period in one field period T is represented by DUTY.

At this time, the light emission period and the extinguishing period are respectively given by the following equations.
First half period:
[(S-1) / m] ・ T <t <{[(s-1) / m] + DUTY / 2} ・ T
Light-off period in the first half period:
{[(S-1) / m] + DUTY / 2} · T <t <{[(s-1) / m] +1/2} · T

Light emission period of the second half period:
[(S-1) / m + 1/2] ・ T <t <{[(s-1) / m] + (1 + DUTY) / 2} ・ T
Light-off period in the second half period:
{[(S-1) / m] + (1 + DUTY) / 2} · T <t <{[(s-1) / m] +1} · T
However, t satisfies the following period.
[(S-1) / m] · T <t <{[(s-1) / m] +1} · T

However, in the driving method in which one field period is divided into the first half period and the second half period, when the total light emission period is 50% of one field period, 25% light emission → 25% light emission → 25% light emission → 25% light emission Repeatedly occurs.
As shown in FIG. 16, this light emission mode causes the same line of sight movement as in the case where 75% of one field period is the light emission period.

  That is, in the driving method that simply divides one field period into the first half period and the second half period, there is a technical problem that flicker can be reduced while moving image blur is generated and the image quality of the moving image is lowered.

  Therefore, the inventor simultaneously increases the peak luminance level over a wide range while simultaneously reducing the occurrence of moving image blur due to the increase in the ratio of the total light emission period in one field period and the suppression of flicker due to the decrease in the ratio of the light emission period. We propose a display panel drive technology that can be adjusted.

  That is, as one of driving techniques, when N (N is N ≧ 2) light emission periods are arranged in one field period, at least one of the intervals between the start timings of adjacent light emission periods is 1 A method of controlling the field period so as to be shorter than a period length obtained by dividing the field period into N parts is proposed.

  When the driving technique proposed by the inventor is adopted, even when the total light emission period length is the same, the length from the start timing of the first light emission period to the end timing of the Nth light emission period is shortened compared to the conventional case. Can do. That is, the movement width of the viewpoint when displaying a moving image can be reduced as compared with the conventional method. The effect of suppressing moving image blur can be enhanced by the reduction of the movement width of the viewpoint.

Further, since the light emission period length from the start timing of the first light emission period to the start timing of the Nth light emission period is expanded to an appropriate length, it is effective that flicker becomes apparent even when the total light emission period length is short. Can be suppressed.
Thus, it is possible to realize a driving method with little deterioration in image quality even when the peak luminance level is adjusted over a wide range.

Hereinafter, an active matrix driving type organic EL panel will be described.
In addition, the well-known or well-known technique of the said technical field is applied to the part which is not illustrated or described in particular in this specification.
Moreover, the form example demonstrated below is one form example of invention, Comprising: It is not limited to these.

(A) Structure of Organic EL Panel FIG. 17 shows a main structure example of the organic EL panel. 17 corresponding to those in FIG. 1 are denoted by the same reference numerals.

  The organic EL panel 21 includes a pixel array unit 3, a first scanning line driving unit 5 for writing signal voltage, a second scanning line driving unit 7 for controlling a light emission period, a data line driving unit 9, and a light emission timing determining unit 23. Consists of. Again, in the pixel array section 3, pixel circuits 11 are arranged in M rows × N columns. M and N are determined according to the display resolution.

  A component unique to this embodiment is a light emission timing determination unit 23. A ratio DUTY of the light emission period in one field period T is given to the light emission timing determination unit 23 from the outside. The light emission timing determination unit 23 determines the arrangement of the light emission periods so as to satisfy the given ratio DUTY. Here, the arrangement of the light emission periods is determined for each second scanning line VSCAN2.

  Although a specific method for determining the light emission period will be described later, the light emission timing determination unit 23 is configured to provide at least an interval between the start timings of adjacent light emission periods when a plurality of light emission periods are arranged in one field period. One is to determine the start timing and end timing of each light emission period so as to be shorter than the length obtained by dividing one field period by the number N (≧ 2) of light emission periods. The light emission timing determining unit 23 and the second scanning line driving unit 7 correspond to a “display panel driving unit” in the claims.

  From the viewpoint of reducing flicker and moving image blur and improving image quality, the period length from the start timing of the first light emission period to the end timing of the last light emission period is 25% or more and 75% or less of one field period. Each timing is determined as follows.

  The light emission timing determination unit 23 operates so as to supply a start pulse DSST that gives the start timing of each light emission period and an end pulse DSET that gives the end timing to the second scanning line drive unit 7 together with the clock DSCK.

(B) Driving example (B-1) Display panel driving example 1
Here, in the state in which the interval between the start timings of adjacent light emission periods is specified to be shorter than the length obtained by dividing one field period by the number N of light emission periods (≧ 2), the given total light emission A driving example in which the end timing of each light emission period is variably determined so as to satisfy the period length (ratio DUTY) will be described.

  FIG. 18 and FIG. 19 show driving timing examples of the second scanning line VSCAN2 when the light emission period in one field period is twice. FIGS. 18 and 19 are examples in which the start timing of the first light emission period is fixed to 0% of one field period, while the start timing of the second light emission period is fixed to 30% of one field period. is there. 18 corresponds to the case where the total light emission period length is long, and FIG. 19 corresponds to the case where the total light emission period length is short.

Incidentally, FIGS. 18 and 19 show that the phase relationship makes a round of 20 lines as in the conventional example described above, but in practice, the phase relationship is set to make a round of M lines.
At this time, the light emission timing determination unit 23 determines the light emission period corresponding to the sth scanning line VSCAN2 (s) based on the following equation.

  However, in the following calculation formula, one field period is expressed as m horizontal scanning periods. In addition, the sth scanning line VSCAN2 (s) is represented as a writing operation being performed during the sth horizontal scanning period and light emission being started simultaneously. Further, the ratio of the total light emission period in one field period T is represented by DUTY. When the calculation result does not become an integer value, the corresponding timing is moved back and forth in units of clocks.

At this time, the light emission period and the extinguishing period are respectively given by the following equations.
First light emission period:
[(S-1) / m] ・ T <t <{[(s-1) / m] + DUTY / 2} ・ T
First off period:
{[(S-1) / m] + DUTY / 2} · T <t <{[(s-1) / m] +0.3} · T

Second light emission period:
{[(S-1) / m] +0.3} · T <t <{[(s-1) / m] + (DUTY) / 2} · T
Second turn-off period:
{[(S-1) / m] + (DUTY) / 2} · T <t <{[(s-1) / m] +1} · T
However, t satisfies the following period.
[(S-1) / m] · T <t <{[(s-1) / m] +1} · T

In the case of this driving example, the interval between the start timings of adjacent light emission periods is 30%. Therefore, even if the total light emission period length is close to 0%, a visual effect equivalent to the light emission period of 30% of one field period can be obtained from the viewpoint of flicker and moving image blur.
Further, even when the total light emission period length is gradually increased from 0%, the increase is equally allocated to the two light emission periods.

For this reason, even when the total light emission period length approaches 60%, a visual effect equivalent to the light emission period of 60% of one field period can be obtained from the viewpoint of flicker and moving image blur.
In the conventional method (FIG. 14), even if the total light emission period length is the same 60%, from the viewpoint of flicker and moving image blur, a visual effect equivalent to that in the case where 80% of one field period is the light emission period occurs. It was.

  As described above, in the case of the driving method proposed by the inventor, even if the peak luminance level is adjusted over a wide range (for example, a range of 0% to 60%), the visual adjustment range is 25 in one field period. % Or more and 75% or less. That is, it is possible to realize a driving method with little deterioration in image quality even when the peak luminance level is adjusted over a wide range.

(B-2) Display panel drive example 2
Incidentally, in the case of the driving example 1 described above, as shown in FIG. 20, it is necessary to change the first light emission period and the second light emission period simultaneously by the same adjustment amount. That is, if the end timing of the first light emission period is changed by 1%, the start timing of the second light emission period needs to be simultaneously changed by 1%.

For this reason, compared with the case where the light emission period within one field period is only once, the adjustment amount of the peak luminance level is reduced to ½. In other words, the minimum adjustment width of the peak luminance level is doubled compared to the case where the light emission period within one field period is only once.
Such characteristics are not preferable from the viewpoint of smoothly adjusting the light emission luminance.

  Therefore, in this driving example, when the minimum adjustment width of the peak luminance level (ratio DUTY) changes, only the end timing of the first light emission period and the start timing of the second light emission period are alternately changed by the minimum adjustment width. It is equipped with a function to let you.

  FIG. 21 shows an example of driving timing corresponding to this driving method. By adopting this driving method, the minimum adjustment width can be made smaller than in driving example 1, and at the same time, the luminance change amount per minimum adjustment width can be reduced. Note that there are cases where the first light emission period length and the second light emission period length become asymmetrical, but this is not a problem in practice.

(B-3) Display panel drive example 3
In the case of the driving example 1 described above, the description has been made on the assumption that two light emission periods are arranged in one field period except for the maximum value (60%) of the variable range of the peak luminance level.
However, dividing the light emission period within one field period into two is limited to a partial range within the variable range, and after exceeding the partial range, one light emission period that combines the two light emission periods. Alternatively, a method may be adopted in which only the end timing is gradually extended.

Here, a driving method based on the arrangement of two light emission periods is applied only when the total light emission period length (ratio DUTY) giving the adjustment amount of the peak luminance level is given at 40% or less of one field period, A case will be described in which a driving method based on the arrangement of one light emission period is applied when the light emission period length (ratio DUTY) exceeds 40% of one field period.
Note that the maximum variable range of the total light emission period length (ratio DUTY) is given by 0% to 60%.

22 to 24 show examples of driving timing of the second scanning line VSCAN2 corresponding to this driving method.
FIG. 22 shows a driving example in the case where the total light emission period length (ratio DUTY) designated from the outside is given within a range of 40% or less of one field period. In this case, the start timing of the second light emission period is fixed to 20%.

  FIG. 22 shows an example in which the total light emission period length (ratio DUTY) is 20%. For this reason, a 10% light emission period is assigned to each of the first light emission period and the second light emission period. The light emission state of FIG. 22 provides a visual effect equivalent to a light emission period of 30% of one field period from the viewpoint of flicker and moving image blur.

  However, when the total light emission period length is close to 0%, from the viewpoint of flicker and moving image blur, the visual effect is equivalent to the light emission period of 20% of one field period, and 25% is obtained to obtain good image quality. there is a possibility.

  However, the light emission period for visual effects falls below 25% of one field period only when DUTY is less than 10% of the total light emission period length. Moreover, the light emission period for visual effect can be secured at least 20% of one field period. Therefore, compared with the conventional method, the deterioration of image quality due to flicker can be greatly reduced.

FIG. 23 shows a driving example when the total light emission period length (ratio DUTY) designated from the outside is 40% of one field period. At this point, the two light emission periods are combined, and the light emission period length for visual effect and the light emission period length for the substance coincide.
FIG. 24 shows a driving example when the ratio DUTY of the light emission period designated from the outside is 50% of one field period.

Incidentally, in the case of FIG. 23 and FIG. 24 as well, in the case of the driving example described above, the phase relationship is rounded by 20 lines, but actually, the phase relationship is rounded by M lines. .
At this time, the light emission timing determination unit 23 determines the light emission period corresponding to the sth scanning line VSCAN2 (s) based on the following equation.

  However, also in the following calculation formula, it is assumed that one field period is given by m horizontal scanning periods. Further, it is assumed that the sth scanning line VSCAN2 (s) is subjected to a writing operation during the sth horizontal scanning period and starts to emit light simultaneously.

Further, the ratio of the total light emission period length in one field period T is represented by DUTY. When the calculation result does not become an integer value, the corresponding timing is moved back and forth in units of clocks.
At this time, the light emission period and the extinguishing period are respectively given by the following equations.

(When 0 <DUTY <0.4)
First light emission period:
[(S-1) / m] ・ T <t <{[(s-1) / m] + DUTY / 2} ・ T
First off period:
{[(S-1) / m] + DUTY / 2} · T <t <{[(s-1) / m] +0.2} · T

Second light emission period:
{[(S-1) / m] +0.2} · T <t <{[(s-1) / m] + (0.2 + DUTY / 2)} · T
Second turn-off period:
{[(S-1) / m] + (0.2 + DUTY / 2)} · T <t <{[(s-1) / m] +1} · T

(0.4 <DUTY <1)
Light emission period:
[(S-1) / m] ・ T <t <{[(s-1) / m] + DUTY} ・ T
Off period:
{[(S-1) / m] + DUTY} · T <t <{[(s-1) / m] +1} · T

  In the case of this driving example, when the total light emission period length (ratio DUTY) in one field period T is 40% or less of one field period T, it is apparent that the light emission period is divided into two times and driven. The ratio of the light emission period can be increased from 20% to 40%. As a result, it is possible to minimize deterioration in image quality due to flicker.

  When the total light emission period length (ratio DUTY) in one field period T is 40% or more and 60% or less of one field period T, the ratio of the apparent light emission period is obtained by combining the light emission periods into one. From 40% to 60%. Thereby, it is possible to suppress deterioration in image quality from the viewpoint of both flicker and moving image blur.

As described above, the peak luminance level can be adjusted over a wide range while suppressing the deterioration of the image quality.
Note that the drive method described in Drive Example 2 can also be applied to this drive example. That is, when the total light emission period length (ratio DUTY) in one field period T is 40% or less of one field period T, only one of the end timing of the first light emission period and the end timing of the second light emission period is minimized. You may change only adjustment amount.

(B-4) Display panel drive example 4
In the case of the driving example 1 described above, in the case where the peak luminance level is controlled by controlling the two light emission period lengths, the interval between the start timings of the two light emission periods is a period length obtained by dividing one field period length into two equal parts ( The case of setting shorter than 50%) has been described. Specifically, the case where the interval between the start timings of the two light emission periods is set to 30% has been described.

However, control based on the total light emission period length can also be realized by controlling each light emission period length divided into three or more.
Here, a case where four light emission periods are set within one field period will be described. Of course, the interval between the start timings of adjacent light emission periods is set to be shorter than the period length (25%) obtained by dividing one field period into four equal parts.

  FIG. 25 and FIG. 26 show driving timing examples of the second scanning line VSCAN2 when the light emission period within one field period is defined as four times. 25 and 26 are examples in which the interval between the start timings of adjacent light emission periods is 15%. That is, the start timing of the first light emission period is 0%, the start timing of the second light emission period is 15%, the start timing of the third light emission period is 30%, and the start timing of the fourth light emission period is 45%. An example is shown.

FIG. 25 shows a driving example when the total light emission period length (ratio DUTY) designated from the outside is short. FIG. 26 shows a driving example when the total light emission period length (ratio DUTY) designated from the outside is long.
In the case of FIGS. 25 and 26, as in the case of the drive example described above, the phase relationship is made to wrap around 20 lines, but in practice, the phase relationship is set to wrap around M lines.

At this time, the light emission timing determination unit 23 determines the light emission period corresponding to the sth scanning line VSCAN2 (s) based on the following equation.
However, also in the following calculation formula, it is assumed that one field period is given by m horizontal scanning periods. Further, it is assumed that the sth scanning line VSCAN2 (s) is subjected to a writing operation during the sth horizontal scanning period and starts to emit light simultaneously.

Further, the ratio of the total light emission period length in one field period T is represented by DUTY. When the calculation result does not become an integer value, the corresponding timing is moved back and forth in units of clocks.
At this time, the light emission period and the extinguishing period are respectively given by the following equations.

(When 0 <DUTY <0.6)
First light emission period:
[(S-1) / m] ・ T <t <{[(s-1) / m] + (DUTY / 4)} ・ T
First off period:
{[(S-1) / m] + (DUTY / 4)} · T <t <{[(s-1) / m] +0.15} · T

Second light emission period:
{[(S-1) / m] +0.15} · T <t <{[(s-1) / m] + (0.15 + DUTY / 4)} · T
Second turn-off period:
{[(S-1) / m] + (0.15 + DUTY / 4)} T <t <{[(s-1) / m] +0.3} T

Third emission period:
{[(S-1) / m] +0.3} · T <t <{[(s-1) / m] + (0.3 + DUTY / 4)} · T
Third turn-off period:
{[(S-1) / m] + (0.3 + DUTY / 4)} · T <t <{[(s-1) / m] +0.45} · T

Fourth emission period:
{[(S-1) / m] +0.45} · T <t <{[(s-1) / m] + (0.45 + DUTY / 4)} · T
4th extinction period:
{[(S-1) / m] + (0.45 + DUTY / 4)} · T <t <{[(s-1) / m] +1} · T

  In this driving example, the total light emission period length (ratio DUTY) occupying one field period T can be variably controlled in the range of 0% to 60%, and at the same time, 45% to 60% from the viewpoint of flicker and motion blur. The effect equivalent to the variable control by the light emission period can be realized.

  That is, in the case of this driving example, the end timing of each light emission period is not fixed, but the interval between the start timings of adjacent light emission periods is shorter than the quarterly interval, so the movement width of the line of sight is increased. It can be actively suppressed. Further, by increasing the number of light emission periods to four, even if the ratio DUTY of the light emission period in one field period T is close to 0%, the visual issue width is widened and flicker is hardly perceived.

That is, it is possible to minimize deterioration in image quality due to flicker and moving image blur.
Further, the driving example 4 may be combined with the driving example 3 described above. That is, the use of the four light emission periods is limited to a partial range of the variable range, and when the range is exceeded, the light emission period may be controlled as one light emission period.

(C) Other Embodiments (C-1) Intervals between Start Timings of Adjacent Light-Emitting Periods In Driving Example 4 described above, the intervals between the start timings of adjacent light-emitting periods are the same (in the case of 15%). Explained.

  However, only a part of the intervals may be used to set the interval between the start timings of the adjacent emission periods to be shorter than 1 / one of the emission period of one field period. For example, in driving example 4, the interval between the start timings of the first and second light emission periods is set to 15%, while the interval between the start timings of the second and third light emission periods and the third and fourth times. The interval between the start timings of the light emission periods may be set to 25%.

  Even in such a case, the line-of-sight movement width can be suppressed as compared with the case where all the intervals are equally divided by the number of light emission periods, and the image quality is deteriorated due to the variable control of the peak luminance level. An improvement effect can be expected. However, in order to avoid a significant deterioration in image quality, it is desirable to set the variable range of the total light emission period length to fall within the range of 25% to 75% of one field period.

(C-2) Minimum Variable Unit of Peak Luminance Level In the case of the driving example 2 described above, when the number of light emitting periods arranged in one field period is two, the peak luminance level is varied by the minimum variable unit. The case has been described where only one of the two light emission periods is controlled to increase or decrease the light emission period length by the minimum variable unit.

  This driving method can be similarly applied when the number of light emitting periods arranged in one field period is three or more. Note that when the number of light emission periods arranged in one field period is N, the number of light emission periods whose light emission period length is variable may be N−1 or less. Of course, the smaller the N−1, the smoother the peak luminance level can be adjusted.

  That is, it is most desirable that the change in the light emission period length corresponding to the minimum variable amount of the peak luminance level is only one of the N light emission periods. Note that the position of the light emission period for changing the light emission period length is arbitrary.

(C-3) Product example (a) Drive IC
In the above description, the case where the pixel array unit and the drive circuit are formed on one panel has been described.
However, the pixel array unit 3 and the drive circuit units 5, 7, 9, 23, etc. can be manufactured and distributed separately. For example, the drive circuit units 5, 7, 9, 23 and the like can be manufactured as independent drive ICs (integrated circuits) and can be distributed independently from the panel on which the pixel array unit 3 is formed.

(B) Display Module The organic EL panel 21 in the above-described embodiment can be distributed in the form of the display module 31 having the appearance configuration shown in FIG.

  The display module 31 has a structure in which a facing portion 33 is bonded to the surface of the support substrate 35. The facing portion 33 is made of glass or other transparent member as a base material, and a color filter, a protective film, a light shielding film, and the like are arranged on the surface thereof.

  The display module 31 may be provided with an FPC (flexible printed circuit) 37 and the like for inputting and outputting signals and the like to the support substrate 35 from the outside.

(C) Electronic device The organic EL panel in the embodiment described above is also distributed in a product form mounted on an electronic device.
FIG. 28 shows a conceptual configuration example of the electronic device 41. The electronic device 41 includes the organic EL panel 43 and the system control unit 45 described above. The processing content executed by the system control unit 45 varies depending on the product form of the electronic device 41.

Note that the electronic device 41 is not limited to a device in a specific field as long as it has a function of displaying an image or video generated in the device or input from the outside.
As this type of electronic device 41, for example, a television receiver is assumed. FIG. 29 shows an example of the appearance of the television receiver 51.

  A display screen 57 composed of a front panel 53, a filter glass 55, and the like is arranged on the front surface of the television receiver 51. The portion of the display screen 57 corresponds to the organic EL panel described in the embodiment.

  Further, for example, a digital camera is assumed as this type of electronic device 41. FIG. 30 shows an example of the external appearance of the digital camera 61. FIG. 30A is an example of the appearance on the front side (subject side), and FIG. 30B is an example of the appearance on the back side (photographer side).

  The digital camera 61 includes an imaging lens (in FIG. 30, the protective cover 63 is in a closed state, so that it is disposed on the back side of the protective cover 63), a flash light emitting unit 65, a display screen 67, a control switch 69, and a shutter. It consists of buttons 71. Of these, the display screen 67 corresponds to the organic EL panel described in the embodiment.

For example, a video camera is assumed as this type of electronic device 41. FIG. 31 shows an appearance example of the video camera 81.
The video camera 81 includes an imaging lens 85 that images a subject in front of a main body 83, a shooting start / stop switch 87, and a display screen 89. Of these, the display screen 89 corresponds to the organic EL panel described in the embodiment.

  Further, for example, a portable terminal device is assumed as this type of electronic device 41. FIG. 32 shows an example of the appearance of a mobile phone 91 as a mobile terminal device. A cellular phone 91 illustrated in FIG. 32 is a foldable type, and FIG. 32A illustrates an appearance example in a state where the housing is opened, and FIG. 32B illustrates an appearance example in a state where the housing is folded.

  The mobile phone 91 includes an upper housing 93, a lower housing 95, a connecting portion (in this example, a hinge portion) 97, a display screen 99, an auxiliary display screen 101, a picture light 103, and an imaging lens 105. Among these, the display screen 99 and the auxiliary display screen 101 correspond to the organic EL panel described in the embodiment.

Further, for example, a computer is assumed as this type of electronic device 41. FIG. 33 shows an example of the appearance of the notebook computer 111.
The notebook computer 111 includes a lower casing 113, an upper casing 115, a keyboard 117, and a display screen 119. Among these, the display screen 119 corresponds to the organic EL panel described in the embodiment.

  In addition to these, the electronic device 41 may be an audio playback device, a game machine, an electronic book, an electronic dictionary, or the like.

(C-4) Other Display Device Examples The driving method described above can be applied to other than the organic EL panel. For example, the present invention can be applied to an inorganic EL panel, a display panel in which LEDs are arranged, and a self-luminous display panel in which other light emitting elements having a diode structure are arranged on a screen.
Further, the driving method described above can also be applied to a liquid crystal display panel and other non-self-luminous display panels.

(C-5) Other Pixel Circuit Examples In the above description, active matrix drive type pixel circuit examples (FIGS. 2 and 3) have been described.
However, the configuration of the pixel circuit is not limited to these, and can be applied to pixel circuits having various configurations existing or proposed in the future.

(C-6) Others Various modifications can be considered for the above-described embodiments within the scope of the gist of the invention. Various modifications and applications created or combined based on the description of the present specification are also conceivable.

It is a figure which shows the main structural examples of an organic electroluminescent panel (conventional example). FIG. 3 is a diagram illustrating an example of an active matrix driving pixel circuit. FIG. 3 is a diagram illustrating an example of an active matrix driving pixel circuit. It is a figure explaining the example of a drive operation in case the light emission period is 1 time (conventional example). It is a figure explaining the example of a drive operation in case the light emission period is 1 time (conventional example). It is a figure which shows the relationship between light emission period length and a peak luminance level. It is a figure explaining the relationship between light emission period length and a motion of a viewpoint. It is a figure explaining the relationship between light emission period length and a motion of a viewpoint. It is a figure explaining the relationship between light emission period length and a motion of a viewpoint. It is a figure which shows the example of a drive timing in case the light emission period length of 50% is given in one light emission period (conventional example). It is a figure which shows the example of a drive timing in the case of giving 20% of light emission period length in one light emission period (conventional example). It is a figure explaining the example of a drive operation in case the light emission period is 2 times (conventional example). It is a figure explaining the example of a drive operation in case the light emission period is 1 time (conventional example). It is a figure which shows the example of a drive timing in the case of giving the light emission period length of 50% in two light emission periods (conventional example). It is a figure which shows the example of a drive timing in case the light emission period length of 2 times gives 20% of light emission period length (conventional example). It is a figure explaining the relationship between light emission period length and a motion of a viewpoint (conventional example). It is a figure which shows the main structural examples of an organic electroluminescent panel (form example). It is a figure which shows the example of a drive timing corresponding to the drive example 1 (form example). It is a figure which shows the example of a drive timing corresponding to the drive example 1 (form example). It is a figure explaining the minimum adjustment amount of the light emission period corresponding to the drive example 1. FIG. It is a figure explaining the minimum adjustment amount of the light emission period corresponding to the drive example 2 (form example). It is a figure which shows the example of a drive timing corresponding to the example 3 of a drive (form example). It is a figure which shows the example of a drive timing corresponding to the example 3 of a drive (form example). It is a figure which shows the example of a drive timing corresponding to the example 3 of a drive (form example). It is a figure which shows the example of a drive timing corresponding to the drive example 4 (form example). It is a figure which shows the example of a drive timing corresponding to the drive example 4 (form example). It is a figure which shows the structural example of a display module. It is a figure which shows the function structural example of an electronic device. It is a figure which shows the example of goods of an electronic device. It is a figure which shows the example of goods of an electronic device. It is a figure which shows the example of goods of an electronic device. It is a figure which shows the example of goods of an electronic device. It is a figure which shows the example of goods of an electronic device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Organic EL panel 3 Pixel array part 5 Scan line drive part 7 Scan line drive part 9 Data line drive part 11 Pixel circuit 21 Organic EL panel 23 Light emission timing determination part

Claims (8)

A display panel driving method for controlling a total luminance period length in one field period to variably control a peak luminance level of the display panel,
When N (N is N ≧ 2) light emission periods are arranged in one field period,
A display panel driving method, wherein at least one interval between the start timings of adjacent light emitting periods is controlled to be shorter than a period length obtained by dividing one field period into N equal parts. The display panel driving method according to claim 1,
The maximum light emission period length assigned to each light emission period is the same,
The display panel driving method, wherein the maximum light emission period length is set shorter than a period length obtained by dividing one field period into N equal parts. The display panel driving method according to claim 1,
The period from the start timing of the first light emission period to the start timing of the Nth light emission period is controlled to be shorter than N-1 times the period length obtained by dividing one field period into N equal parts. Display panel driving method. The display panel driving method according to claim 1,
A display panel driving method characterized by limiting the number of light emitting periods to be variable when the peak luminance level is changed by a minimum unit to at most N−1. The display panel driving method according to claim 1,
A display panel driving method characterized in that, when the peak luminance level is changed by a minimum unit, only one of N light emission periods is set as a variable target. A display panel driving unit that variably controls the peak luminance level of the display panel by controlling the total light emission period length in one field period, and N (N is N ≧ 2) light emission periods in one field period. A display panel driver that variably controls so that at least one interval between the start timings of adjacent light emission periods is shorter than a period length obtained by dividing one field period into N equal parts,
And a display panel having a pixel structure corresponding to an active matrix driving method. A display panel driving unit that variably controls the peak luminance level of the display panel by controlling the total light emission period length in one field period, and N (N is N ≧ 2) light emission periods in one field period. When arranged, it has a display panel driving unit that variably controls so that at least one of the intervals between the start timings of adjacent light emitting periods is shorter than a period length obtained by dividing one field period into N equal parts. Display panel drive device. A display panel driving unit that variably controls the peak luminance level of the display panel by controlling the total light emission period length in one field period, and N (N is N ≧ 2) light emission periods in one field period. A display panel driver that variably controls so that at least one interval between the start timings of adjacent light emission periods is shorter than a period length obtained by dividing one field period into N equal parts,
A display panel having a pixel structure corresponding to an active matrix driving method;
A system controller;
An electronic device comprising: an operation input unit for the system control unit.

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