JP2011022239A - Display device, method of driving the same, and electronic device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a display device with which motion picture blurrs and flickers are reduced, at the same time, a method of driving the same, and to provide an electronic device. <P>SOLUTION: Motion of an image is detected by comparing a first video signal 20A and a second video signal 20A (S1). Then, a video signal corresponding to a motion picture, and a video signal corresponding to a still picture are detected, by utilizing a detection result (S2). the duty ratio of the video signal corresponding to the motion picture is set to a mode 1, and the duty ratio of the video signal corresponding to the still picture is set to a mode 2 (S3 and S4), and the value of the video signal 20A is converted so as to become a value according to a size of the duty ratio (S5 and S6). Then, an analog video signal 20A of a size corresponding to the mode is output to a signal line drive circuit 23 at a prescribed timing, and an erasing selection signal or an erasing non-selection signal are output to the signal drive circuit 23 at a prescribed timing (S7 and S8). <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a display device that displays an image with a light emitting element arranged for each pixel and a driving method thereof. Moreover, this invention relates to the electronic device provided with the said display apparatus.

  In recent years, in the field of display devices that perform image display, display devices that use current-driven optical elements, such as organic EL (electroluminescence) elements, whose light emission luminance changes according to the value of a flowing current are used as light emitting elements of pixels. Developed and commercialized.

  Unlike a liquid crystal element or the like, the organic EL element is a self-luminous element. Therefore, a display device (organic EL display device) using an organic EL element does not require a light source (backlight), and thus has higher image visibility and lower power consumption than a liquid crystal display device that requires a light source. And the response speed of the element is fast.

  In the organic EL display device, similarly to the liquid crystal display device, there are a simple (passive) matrix method and an active matrix method as its driving method. Although the former has a simple structure, there is a problem that it is difficult to realize a large-sized and high-definition display device. For this reason, active matrix systems are currently being actively developed. In this method, a current flowing through a light emitting element arranged for each pixel is controlled by an active element (generally a TFT (Thin Film Transistor)) provided in a drive circuit provided for each light emitting element.

JP 2008-9391 A

  By the way, in the organic EL display device, when the light emission and extinction of the organic EL element is performed within one field period, what is the duty ratio (light emission period / 1 field period × 100) that is the ratio of the light emission period in one field period? The problem is whether to set the value. This is because the duty ratio at which moving image blur does not occur is different from the duty ratio at which flicker does not occur. For example, in the conventional driving method in which the light emission period in one frame is determined by the period during which a high voltage is applied to the drain line, the duty ratio is constant for all pixels. In this driving method, flicker occurs when the duty ratio is set so that no moving image blur occurs, and moving image blur occurs when the duty ratio is set such that flicker does not occur.

  Many other driving methods have been proposed. For example, Patent Document 1 discloses a method of performing gradation expression by dividing one frame into a plurality of subfields and using a plurality of subfields. This driving method is more effective in reducing motion blur than the previous driving method. However, in this driving method, the light emission period of the subfield is fixed for each gradation. Therefore, for example, since the light emission period is short at low luminance, flicker is likely to occur, and since the light emission period is long at high luminance, there is a problem that moving image blur is likely to occur. In addition, another literature discloses a driving method for detecting a motion in a moving image and adjusting a light emission period according to the amount of motion. However, with this driving method, since the duty ratio is constant for all pixels, there is a problem that flickering occurs in the still image portion when the image includes a still image.

  As described above, the conventional driving method has a problem that it is not easy to reduce moving image blur and flicker at the same time.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a display device capable of reducing moving image blur and flicker at the same time, a driving method thereof, and an electronic apparatus.

  The display device of the present invention is arranged in a matrix corresponding to a plurality of scanning lines arranged in a row, a plurality of signal lines arranged in a column, and an intersection of each scanning line and each signal line. And a pixel circuit array unit including a plurality of light emitting elements and a plurality of pixel circuits. The display device further includes a detection circuit, a duty control circuit, a signal line driving circuit, and a scanning line driving circuit. Here, the detection circuit detects a video signal corresponding to a moving image and a video signal corresponding to a still image included in the video signal for one frame. The duty control circuit sets the duty ratio of the video signal corresponding to the moving image to a small value and changes the size of the video signal corresponding to the moving image according to the size of the duty ratio. The duty control circuit further sets the duty ratio of the video signal corresponding to the still image to a large value and changes the size of the video signal corresponding to the still image according to the size of the duty ratio. . The signal line driving circuit sequentially applies a signal voltage corresponding to a video signal having a magnitude set by the duty control circuit to each signal line, and performs writing to the pixel circuit to be selected. The signal line driving circuit further applies a selection voltage corresponding to the size of the duty ratio set by the duty control circuit to each signal line in order to write to the pixel circuit to be selected. . The scanning line driving circuit sequentially applies selection pulses to a plurality of scanning lines to sequentially select a plurality of light emitting elements and a plurality of pixel circuits.

  An electronic apparatus according to the present invention includes the display device.

The display device driving method of the present invention includes the following four steps.
(A) A step of preparing a display device having the following configuration (B) A video signal corresponding to a moving image included in a video signal for one frame and a video signal corresponding to a still image are detected, and then a moving image is supported. Set the video signal duty ratio to a small value, change the video signal size corresponding to the moving image according to the duty ratio, and set the video signal duty ratio corresponding to the still image to a large value. A step of changing the size of the video signal corresponding to the still image according to the size of the duty ratio. (C) A signal voltage corresponding to the video signal having a size set by the duty control circuit is sequentially applied to each signal line. In addition, writing to the pixel circuit to be selected is performed, and a selection voltage corresponding to the magnitude of the duty ratio set by the duty control circuit is sequentially applied to each signal line. Pressurized to, the selection pulse sequentially applied to the step (D) a plurality of scanning lines for writing into the pixel circuits of the selection target, sequentially selecting a plurality of light emitting elements and a plurality of pixel circuits step

  A display device using the driving method includes a pixel circuit array unit and a driving circuit that drives the pixel circuit array unit. The pixel circuit array section is arranged in a matrix corresponding to a plurality of scanning lines arranged in rows, a plurality of signal lines arranged in columns, and intersections of the scanning lines and signal lines. A plurality of light emitting elements and a plurality of pixel circuits are included.

  In the display device, the driving method thereof, and the electronic device of the present invention, the duty ratio of the video signal corresponding to the moving image is set to a small value, and the size of the video signal corresponding to the moving image is changed according to the size of the duty ratio. Is done. Furthermore, the duty ratio of the video signal corresponding to the still image is set to a large value, and the size of the video signal corresponding to the still image is changed according to the size of the duty ratio. Thus, in a video signal for one frame, a duty ratio suitable for a moving picture can be set for a video signal corresponding to a moving picture, and a duty ratio suitable for a still picture can be set for a video signal corresponding to a still picture. Can do.

  According to the display device, the driving method thereof, and the electronic apparatus of the present invention, a video signal corresponding to a moving image can be set in a video signal corresponding to a moving image, and a video corresponding to a still image can be set. The signal can be set to a duty ratio suitable for still images. Thereby, moving image blur and flicker can be reduced simultaneously.

It is a block diagram showing an example of the display apparatus which concerns on one embodiment of this invention. FIG. 2 is a configuration diagram illustrating an example of an internal configuration of a pixel circuit array unit in FIG. 1. 2 is a flowchart for explaining the operation of the video signal processing circuit of FIG. 1. It is the figure which represented notably the mode that 1 field was divided into three periods. It is a relationship diagram between a duty ratio and a mode. FIG. 6 is a waveform diagram for explaining an example of operation in mode 1 of the display device of FIG. 1. FIG. 8 is a waveform diagram for explaining an example of operation in mode 2 of the display device of FIG. 1. FIG. 2 is a relationship diagram between an image displayed on the display device of FIG. 1 and modes. It is a top view showing schematic structure of the module containing the display apparatus of the said embodiment. It is a perspective view showing the external appearance of the application example 1 of the display apparatus of the said embodiment. (A) is a perspective view showing the external appearance seen from the front side of the application example 2, (B) is a perspective view showing the external appearance seen from the back side. 12 is a perspective view illustrating an appearance of application example 3. FIG. 14 is a perspective view illustrating an appearance of application example 4. FIG. (A) is a front view of the application example 5 in an open state, (B) is a side view thereof, (C) is a front view in a closed state, (D) is a left side view, and (E) is a right side view, (F) is a top view and (G) is a bottom view.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the invention will be described in detail with reference to the drawings. The description will be given in the following order.

1. Embodiment
1.1 Schematic configuration of display device
1.2 Operation of video signal processing circuit
1.3 Operation of display device
1.4 Action and effect Modules and application examples

<1. Embodiment>
(1.1 Schematic configuration of display device)
FIG. 1 shows a schematic configuration of a display device 1 according to an embodiment of the present invention. The display device 1 includes a display panel 10 and a drive circuit 20. The display panel 10 includes, for example, a pixel circuit array unit 13 in which a plurality of organic EL elements 11R, 11G, and 11B (light emitting elements) are arranged in a matrix. In the present embodiment, for example, three organic EL elements 11R, 11G, and 11B adjacent to each other constitute one pixel 12. Hereinafter, the organic EL element 11 is appropriately used as a general term for the organic EL elements 11R, 11G, and 11B. The drive circuit 20 drives the pixel circuit array unit 13, and includes, for example, a video signal processing circuit 21, a timing generation circuit 22, a signal line drive circuit 23, a scanning line drive circuit 24, and a power supply line drive circuit 25. ing.

[Pixel circuit array section]
FIG. 2 illustrates an example of a circuit configuration of the pixel circuit array unit 13. The pixel circuit array unit 13 is formed in the display area of the display panel 10. For example, as illustrated in FIGS. 1 and 2, the pixel circuit array unit 13 includes a plurality of scanning lines WSL arranged in rows, a plurality of signal lines DTL arranged in columns, and scanning lines WSL. And a plurality of power supply lines PSL arranged in rows. A plurality of organic EL elements 11 and pixel circuits 14 are arranged in a matrix (two-dimensional arrangement) corresponding to the intersections of the scanning lines WSL and the signal lines DTL. The pixel circuit 14 is configured by, for example, a drive transistor Tr ₁ , a write transistor Tr _2, and a storage capacitor C _s , and has a circuit configuration of 2Tr1C. The drive transistor Tr ₁ and the write transistor Tr ₂ are formed by, for example, n-channel MOS type thin film transistors (TFTs). Note that the type of TFT is not particularly limited, and may be, for example, an inverted staggered structure (so-called bottom gate type) or a staggered structure (top gate type). Further, the drive transistor Tr ₁ or the write transistor Tr ₂ may be a p-channel MOS type TFT.

In the pixel circuit array section 13, the signal line DTL, the output terminal of the signal line drive circuit 23 (not shown) is connected to the drain electrode of the writing transistor Tr ₂ (not shown). Each scanning line WSL is the output terminal of the scanning line drive circuit 24 (not shown) is connected to the gate electrode of the writing transistor Tr ₂ (not shown). Each power line PSL, the output terminal of the power source line drive circuit 25 (not shown) is connected to the drain electrode of the driving transistor Tr ₁ (not shown). The source electrode (not shown) of the write transistor Tr ₂ is connected to the gate electrode (not shown) of the drive transistor Tr ₁ and one end of the storage capacitor C _s . The source electrode (not shown) of the drive transistor Tr ₁ and the other end of the storage capacitor C _s are connected to the anode electrode (not shown) of the organic EL element 11. A cathode electrode (not shown) of the organic EL element 11 is connected to the ground line GND, for example. The cathode electrode is used as a common electrode for each organic EL element 11, and is formed continuously over the entire display region of the display panel 10, for example, and has a flat plate shape.

[Drive circuit]
Next, each circuit in the drive circuit 20 provided around the pixel circuit array unit 13 will be described with reference to FIG. For example, as shown in FIG. 1, the video signal processing circuit 21 includes a moving image still image detection circuit 21A and a duty control circuit 21B.

  The moving image still image detection circuit 21A detects a moving image region and a still image region included in an image of one frame based on the video signal 20A input from the outside. The moving image still image detection circuit 21A includes, for example, a storage unit (not shown) that stores a video signal 20A for one frame, and a calculation unit (FIG. 5) that detects a moving image region and a still image region included in one frame image. Not shown). The duty control circuit 21B determines a duty ratio (light emission period / 1 field period × 100), which is a ratio of the light emission period in one field period, for each pixel 12 (for each moving image region and still image region). The operations of the moving image still image detection circuit 21A and the duty control circuit 21B will be described later.

  The timing generation circuit 22 controls the signal line driving circuit 23, the scanning line driving circuit 24, and the power supply line driving circuit 25 to operate in conjunction with each other. For example, the timing generation circuit 22 outputs a control signal 22A to these circuits in response to (in synchronization with) a synchronization signal 20B input from the outside.

In response to (in synchronization with) the input of the control signal 22A, the signal line driving circuit 23 applies an analog video signal corresponding to the video signal 20A input from the duty control circuit 21B to each signal line DTL, An analog video signal or a signal corresponding thereto is written to the pixel circuit 14 to be selected. Specifically, the signal line drive circuit 23 applies the signal voltage V _sig corresponding to the video signal 20A having the magnitude set by the duty control circuit 21B to each signal line DTL, and then to the pixel circuit 14 to be selected. Is written. Note that writing refers to applying a predetermined voltage to the gate of the driving transistor Tr ₁ .

The signal line driving circuit 23 sequentially applies a selection voltage corresponding to the magnitude of the duty ratio set by the duty control circuit 21B to each signal line in response to (in synchronization with) the input of the control signal 22A. Writing to the pixel circuit to be selected is performed. Specifically, the signal line drive circuit 23 applies a voltage V _ers as a selection voltage to each signal line DTL in response to the input of the erase selection signal output from the duty control circuit 21B, and the pixel circuit to be selected. 14 is written. Further, the signal line drive circuit 23 applies the voltage V _ofs as the selection voltage to each signal line DTL in response to the input of the erasure non-selection signal output from the duty control circuit 21B, to the pixel circuit 14 to be selected. It is also possible not to write.

The signal line drive circuit 23 can output, for example, the signal voltage V _sig and the voltages V _ofs and V _ers applied to the gate of the drive transistor Tr ₁ when the organic EL element 11 is extinguished. Here, the voltage V _ofs has a voltage value (constant value) lower than the threshold voltage V _el of the organic EL element 11 and a voltage value higher than V _M −V _{th ws} . The voltage V _ofs is also applied to the signal line DTL during an erase selection period described later when non-erasure is selected by the duty control circuit 21B.

The voltage V _M, when the erasing by the duty control circuit 21B is selected, the voltage (constant value) applied to the scanning line WSL erase selection period later. Voltage V _M is higher than the voltage V _L, and has a voltage value lower than the voltage V _H (constant value). The voltage V _L has a voltage value (constant value) lower than the ON voltage of the write transistor Tr ₂ . The voltage V _H has a voltage value (a constant value) that is equal to or higher than the ON voltage of the write transistor Tr ₂ . The voltage V _{th ws} is a threshold voltage of the write transistor Tr ₂ . The voltage V _ers is applied to the signal line DTL during the erase selection period described later when erase is selected by the duty control circuit 21B. The voltage V _ers has a voltage value (constant value) higher than V _L −V _{th ws and} lower than V _M −V _{th ws} .

The scanning line drive circuit 24 sequentially selects the plurality of organic EL elements 11 and the plurality of pixel circuits 14 by sequentially applying selection pulses to the plurality of scanning lines WSL in response to (in synchronization with) the input of the control signal 22A. To do. Further, the scanning line driving circuit 24 is selected to apply during the other period when the selection voltage (voltage V _ers ) is applied to the signal line DTL in response to (in synchronization with) the input of the control signal 22A. A selection pulse having a smaller peak value (voltage V _M ) than the pulse peak value (voltage V _H ) is applied to the scanning line WSL. Scanning line drive circuit 24, for example, the voltage V _H to be applied when turning on the writing transistor Tr _2, the voltage V _M to be applied when selecting whether to turn on or off the write transistor Tr _2, the writing transistor Tr It is possible to output a voltage V _L applied when ₂ is turned off.

The power supply line drive circuit 25 controls the light emission and quenching of the organic EL element 11 by sequentially applying control pulses to the plurality of power supply lines PSL in response to (in synchronization with) the input of the control signal 22A. Power line drive circuit 25, for example, a voltage V _ccH applied when supplying a current to the driving transistor Tr _1, and it is possible to output a voltage V _ccL applied when no current is supplied to the drive transistor Tr ₁ It has become. Here, the voltage V _ccL is a voltage value (constant value) lower than a voltage (V _el + V _ca ) obtained by adding the threshold voltage V _el of the organic EL element 11 and the voltage V _ca of the cathode of the organic EL element 11. It is. V _ccH is a voltage value (constant value) equal to or higher than the voltage (V _el + V _ca ).

(1.2 Operation of video signal processing circuit 21)
FIG. 3 illustrates an example of a processing flow in the moving image still image detection circuit 21A and the duty control circuit 21B included in the video signal processing circuit 21. First, the moving image still image detection circuit 21A, for example, compares the video signal 20A (first video signal 20A) for one frame with the video signal 20A (second video signal 20A) one frame before that frame. Then, the motion of the image included in the first video signal 20A is detected (step S1). For example, the moving image still image detection circuit 21A derives a difference between the first video signal 20A and the second video signal 20A.

  Next, the moving image still image detection circuit 21A uses the detection result to determine whether each video signal included in the first video signal 20A corresponds to a moving image or a still image (step S2). ). Specifically, the moving image still image detection circuit 21A detects a video signal corresponding to a moving image and a video signal corresponding to a still image included in the first video signal 20A. The moving image still image detection circuit 21A determines, for example, a video signal having a difference value exceeding a predetermined threshold among the video signals included in the first video signal 20A as a video signal corresponding to the moving image. The moving image still image detection circuit 21A determines, for example, a video signal whose difference value does not exceed a predetermined threshold among video signals included in the first video signal 20A as a video signal corresponding to a still image. Subsequently, the moving image still image detection circuit 21A has the coordinates (moving image coordinates) of the pixel 12 to which the video signal corresponding to the moving image is applied and the coordinates (still image coordinates) of the pixel 12 to which the video signal corresponding to the still image is applied. ) Is derived.

  Next, the moving image still image detection circuit 21A outputs, for example, information about the moving image region and the still image region (information about moving image coordinates and still image coordinates) included in one frame image to the duty control circuit 21B as a detection signal. To do. Note that the moving image still image detection circuit 21A may output, for example, only information about moving image coordinates to the duty control circuit 21B as a detection signal, or only information about still image coordinates to the duty control circuit 21B as a detection signal. It may be output.

The duty control circuit 21 </ b> B sets the duty ratio as follows when information about moving image coordinates and still image coordinates is input as a detection signal. That is, for example, the duty control circuit 21B sets the duty ratio of the video signal corresponding to the moving image coordinates to a small value in the first video signal 20A input in synchronization with the detection signal, and corresponds to the still image coordinates. Set the video signal duty ratio to a large value. Further, when only information about moving image coordinates is input as a detection signal, the duty control circuit 21B sets the duty ratio as follows. That is, for example, the duty control circuit 21B sets the duty ratio of the video signal corresponding to the moving image coordinates to a small value in the first video signal 20A input in synchronization with the detection signal, and sets the other coordinates to other coordinates. Set the duty ratio of the corresponding video signal to a large value. Further, when only information about still image coordinates is input as a detection signal, the duty control circuit 21B sets the duty ratio as follows. That is, for example, the duty control circuit 21B sets the duty ratio of the video signal corresponding to the still image coordinates in the first video signal 20A input in synchronization with the detection signal to a large value, and coordinates other than that The duty ratio of the video signal corresponding to is set to a small value. In summary, the duty control circuit 21B sets the duty ratio of the video signal corresponding to the moving image (video signal corresponding to the moving image coordinates or coordinates corresponding to the moving image coordinates) of the first video signal 20A to a small value. Furthermore, the duty control circuit 21B sets the duty ratio of the video signal corresponding to the still image (video signal corresponding to the still image coordinates or coordinates corresponding to the still coordinates) to a large value. For example, as shown in FIG. 4, the duty control circuit 21B divides one field period _TF into three parts, an extinction period T _off , a light emission selection period _Ton1 , and a light emission selection period _Ton2 . The extinction period T _off is also a period for performing V _th correction, μ correction, and the like, as will be described later. Next, for example, as shown in FIG. 5, the duty control circuit 21B sets the duty ratio of the video signal corresponding to the moving image coordinates to mode 1 (step S3), and the duty of the video signal corresponding to the still image coordinates. The ratio is set to mode 2 (step S4).

Here, mode 1, select "luminescence" in the light-emitting selection period T _on1, a mode for selecting the "non-light emission" in the light-emitting selection period T _on2. Mode 2, select "luminescence" in the light-emitting selection period T _on1, a mode for selecting the "emission" is also in the light-emitting selection period T _on2.

Next, the duty control circuit 21B converts the value of the video signal 20A so as to have a value corresponding to the magnitude of the duty ratio. When the value of the video signal 20A before conversion is Vi and the value of the video signal 20A after conversion is Vo, the duty control circuit 21B converts the value of the video signal 20A as follows. That is, when mode 1 is selected as the duty ratio, duty control circuit 21B converts the value of video signal 20A using the following equation (1) (step S5). Further, when the mode 2 is selected as the duty ratio, the duty control circuit 21B converts the value of the video signal 20A using the following equation (2) (step S6). Vo = Vi × ( _TF / _Ton1 ) (1)
Vo = Vi × ( _TF / (T _on1 + T _on2 )) (2)

  Next, the duty control circuit 21B performs predetermined correction on the converted video signal 20A and converts the corrected video signal into analog. Examples of the predetermined correction include gamma correction and overdrive correction. Thereafter, the duty control circuit 21B drives the signal line driving circuit 23 in accordance with the set mode. For example, when the mode 1 is selected, the duty control circuit 21B outputs an analog video signal 20A having a magnitude corresponding to the mode 1 to the signal line driving circuit 23 at a predetermined timing and also selects the erasure selection. A signal is output at a predetermined timing (step S7). For example, when the mode 2 is selected, the duty control circuit 21B outputs an analog video signal 20A having a size corresponding to the mode 2 to the signal line driving circuit 23 at a predetermined timing. An erase non-selection signal is output at a predetermined timing (step S8).

When the erase selection signal is applied to the signal line drive circuit 23, the signal line drive circuit 23 applies the voltage V _ers to the signal line DTL during the erase selection period _Ters in FIG. When the erase non-selection signal is applied to the signal line drive circuit 23, the signal line drive circuit 23 applies the voltage V _ofs to the signal line DTL during the erase selection period _Ters in FIG. Note that the video signal processing circuit 21 may execute the above-described steps after performing predetermined correction on the digital video signal 20A input from the outside.

(1.3 Operation of display device)
FIG. 6 shows an example of various waveforms when the display device 1 is driven in the mode 1. FIG. 7 shows an example of various waveforms when the display device 1 is driven in the mode 2. In FIGS. _6A to 6C and FIGS. 7A to 7C, V _ofs , V _sig , and V _ers are periodically applied to the signal line DTL, and V _H and V _L are applied to the scanning line WSL. , V _M is applied at a predetermined timing, V _ccL the power supply line PSL, V _ccH is shown to have been applied at a predetermined timing. 6D, 6E, 7D, and 7E show the gate voltage V _g of the drive transistor Tr ₁ in response to voltage application to the signal line DTL, the scanning line WSL, and the power supply line PSL. In addition, it is shown that the source voltage V _s changes from moment to moment. In the following, first, the operation common to the modes will be described, and then the operation of each mode will be described.

[V _th correction preparation period]
First, preparation for V _th correction is performed. Specifically, the power supply line drive circuit 25 lowers the voltage of the power line PSL from V _ccH the V _ccL (T _1). Then, the source voltage V _s is V _ccL next, together with the organic EL element 11 is quenched, the gate voltage V _g drops to V _ofs. Then, the voltage of the signal line DTL is V _ofs, and while the voltage of the power supply line PSL is V _ccL, the scanning line drive circuit 24 to the V _H the voltage of the scanning line WSL from V _L increase.

[First V _th correction period]
Next, V _th is corrected. Specifically, while the voltage of the signal line DTL is V _ofs, the power supply line drive circuit 25 raises the voltage of the power supply line PSL from V _ccL the V _ccH (T _2). Then, a current I _d flows between the drain and source of the driving transistor Tr ₁ and the source voltage V _s rises. Thereafter, before the signal line driving circuit 23 switches the voltage of the signal line DTL from V _ofs to V _sig , the scanning line driving circuit 24 reduces the voltage of the scanning line WSL from V _H to V _L (T ₃ ). Then, the gate of the drive transistor Tr ₁ becomes floating, and the correction of V _th is temporarily stopped.

[First V _th correction pause period]
During the period in which the V _th correction is paused, the voltage of the signal line DTL is sampled in another row (pixel) different from the row (pixel) on which the previous V _th correction has been performed. In the case V _th correction is insufficient, i.e., the gate of the drive transistor Tr ₁ - when the potential difference V _gs between the source is larger than the threshold voltage V _th of the drive transistor Tr ₁ is as follows. That is, even during the V _th correction pause period, in the row (pixel) in which the previous V _th correction is performed, the current I _ds flows between the drain and source of the drive transistor Tr ₁ , and the source voltage V _s rises and is held. also it increases the gate voltage V _g by the capacitive coupling C _s.

[Second V _th correction period]
After the V _th correction pause period ends, the V _th correction is performed again. Specifically, when the voltage of the signal line DTL is V _ofs and V _th correction is possible, the scanning line driving circuit 24 increases the voltage of the scanning line WSL from V _L to V _H (T ₄ ) The gate of the driving transistor Tr ₁ is connected to the signal line DTL. At this time, when the source voltage V _s is lower than (V _ofs −V _th ) (when V _th correction is not yet completed), the drive transistor Tr ₁ is cut off (the potential difference V _gs is V _th). Until the current I _d flows between the drain and source of the drive transistor Tr ₁ . As a result, the holding capacitor C _s is charged to V _th, the potential difference V _gs becomes V _th. Thereafter, before the signal line driving circuit 23 switches the voltage of the signal line DTL from V _ofs to V _sig , the scanning line driving circuit 24 lowers the voltage of the scanning line WSL from V _H to V _L (T ₅ ). Then, since the gate of the drive transistor Tr ₁ becomes floating, the potential difference V _gs can be maintained at V _th regardless of the voltage level of the signal line DTL. In this way, by setting the potential difference V _gs to V _{th, even} when the threshold voltage V _th of the drive transistor Tr ₁ varies for each pixel circuit 14, the emission luminance of the organic EL element 11 varies. Can be eliminated.

[Second V _th correction pause period]
Thereafter, the signal line drive circuit 23 switches the voltage of the signal line DTL from V _ofs to V _sig during the suspension period of V _th correction.

[Writing / μ correction period]
After the end of the V _th correction pause period, writing and μ correction are performed. Specifically, while the voltage of the signal line DTL is V _sig , the scanning line driving circuit 24 raises the voltage of the scanning line WSL from V _L to V _H (T ₆ ), and the gate of the driving transistor Tr ₁ . Is connected to the signal line DTL. Then, the gate voltage of the drive transistor Tr ₁ becomes V _sig . At this time, the anode voltage of the organic EL element 11 is still smaller than the threshold voltage V _el of the organic EL element 11 at this stage, and the organic EL element 11 is cut off. Therefore, the current I _ds flows into the element capacitance (not shown) of the organic EL element 11 and the element capacitance is charged. Therefore, the source voltage V _s increases by ΔV, and the potential difference V _gs eventually becomes V _sig + V _th −ΔV. It becomes. In this way, μ correction is performed simultaneously with writing. Here, ΔV increases as the mobility μ of the driving transistor Tr ₁ increases. Therefore, by reducing the potential difference V _gs by ΔV before light emission, variation in the mobility μ for each pixel circuit 14 can be removed. .

[Bootstrap period]
Next, the scanning line driving circuit 24 lowers the voltage of the scanning line WSL from V _H to V _L (T ₇ ). Then, the gate of the drive transistor Tr ₁ becomes floating, the gate of the drive transistor Tr ₁ - a voltage V _gs between the source while maintaining constant, the drain of the drive transistor Tr ₁ - current I _d flows between the source. As a result, the source voltage V _s increases, and the gate of the drive transistor Tr ₁ also increases in conjunction with it.

  Next, the operation when the mode 1 is selected by the duty control circuit 21B will be described with reference to FIG.

[Light emission selection period (T _on1 )]
When the bootstrap period elapses and the source voltage V _s rises to a predetermined voltage, the organic EL element 11 emits light with a desired luminance (T ₈ ).

[Light emission selection period (T _on2 )]
Next, when a predetermined period has elapsed since the organic EL element 11 started to emit light, the signal line drive circuit 23 changes the voltage of the signal line DTL to V _ers in response to (in synchronization with) application of the erase selection signal. (T ₉ ). Subsequently, the scanning line drive circuit 24 is raised to V _M voltage of the scanning line WSL from V _L, it connects the the gate of the drive transistor Tr ₁ in the signal line DTL (T _10). Then, the driving transistor Tr ₁ in the gate voltage V _ers, and the gate of the drive transistor Tr ₁ - voltage V _gs between the source since the V _ers -V _el <V _th, light emission of the organic EL element 11 stops. That is, the signal line drive circuit 23 applies the voltage V _ers to the signal line DTL during the erase selection period _Ters in response to (synchronously with) the application of the erase selection signal to the organic EL element 11 to be selected. Stop the flowing steady current. Thereafter, while the voltage of the signal line DTL is V _ers , the scanning line driving circuit 24 decreases the voltage of the scanning line WSL from V _M to V _L. Then, the gate of the drive transistor Tr ₁ becomes floating, and thereafter, the light emission of the organic EL element 11 remains stopped.

  Next, the operation when the mode 2 is selected by the duty control circuit 21B will be described with reference to FIG.

[Light emission selection period (T _on1 )]
When the bootstrap period elapses and the source voltage V _s rises to a predetermined voltage, the organic EL element 11 emits light with a desired luminance (T ₈ ).

[Light emission selection period (T _on2 )]
Next, when a predetermined period has elapsed since the organic EL element 11 started to emit light, the signal line driving circuit 23 changes the voltage of the signal line DTL to V in response to (in synchronization with) application of the erase non-selection signal. Lower to _ofs (T ₉ ). Subsequently, the scanning line drive circuit 24 is raised to V _M voltage of the scanning line WSL from V _L (T _10). At this time, the gate of the writing transistor Tr ₂ - voltage V _gs between the source are V _M -V _ofs, less than the threshold voltage V _{th ws} of the writing transistor Tr _2. Accordingly, the write transistor Tr ₂ remains off, and the gate of the drive transistor Tr ₁ remains in a floating state, so that the organic EL element 11 continues to emit light. Then, while the voltage of the signal line DTL is V _ofs, the scanning line drive circuit 24 is lowered to V _L the voltage of the scanning line WSL from V _M. At this time as well, the write transistor Tr ₂ remains off and the gate of the drive transistor Tr ₁ is kept in a floating state, so that the organic EL element 11 continues to emit light.

8A and 8B schematically show the state of an image displayed on the display device 1 during the light emission selection period (T _on1 ) and the light emission selection period (T _on2 ). FIG. 8A shows an image in the light emission selection period (T _on1 ), and FIG. 8B shows an image in the light emission selection period (T _on2 ). 8A and 8B show a state in which a moving image area α and a still image area β are mixed in the image.

  8A and 8B, in the moving image area α, the mode 1 is selected by the duty control circuit 21B, and in each pixel 12 in the moving image area α, as shown in FIGS. It can be seen that driving is performed in the order of light emission and extinction. 8A and 8B, the mode 2 is selected by the duty control circuit 21B in the still image region β, and each pixel 12 in the still image region β is shown in FIG. 5 and FIG. As can be seen from the figure, driving is performed in the order of light emission and light emission. Thus, in the present embodiment, the duty ratio (light emission period / 1 field period × 100), which is the ratio of the light emission period in one field period, is determined for each pixel 12.

  In the display device 1 of the present embodiment, as described above, the pixel circuit 14 is controlled to be turned on / off in each pixel 12, and a driving current is injected into the organic EL element 11 of each pixel 12. And recombine to emit light. This light is multiple-reflected between the anode and the cathode, passes through the cathode, etc., and is extracted outside. As a result, an image is displayed on the display panel 10.

(1.4 Action / effect)

  By the way, in general, when the organic EL element 11 emits and extinguishes within one field period, flicker becomes apparent when the duty ratio (light emission period / 1 field period × 100), which is the ratio of the light emission period in one field period, is reduced. Turn into. On the other hand, when the duty ratio is increased, moving image blur becomes obvious. This is because the duty ratio at which no flicker occurs is different from the duty ratio at which no moving image blur occurs.

  Therefore, in the present embodiment, as shown in FIGS. 8A and 8B, the duty ratio is reduced in the moving image area α (mode 1 is selected), and the duty ratio is changed in the still image area β. It is enlarged (mode 2 is selected). In this manner, moving image blur and flicker can be suppressed simultaneously by adjusting the duty ratio to an appropriate value for each pixel 12 (for each moving image region α and still image region β) in the same screen. As a result, the image quality is greatly improved. In the present embodiment, as shown in FIG. 3, the value of the video signal 20A is converted according to the duty ratio (mode) so that the luminance of each pixel 12 becomes a desired value. There is no possibility that the change of the duty ratio adversely affects the luminance.

<2. Modules and application examples>
Hereinafter, application examples of the display device described in the above embodiment will be described. The display device of the above embodiment is a television device, a digital camera, a notebook personal computer, a mobile terminal device such as a mobile phone, or a video camera, and the like. Alternatively, the present invention can be applied to display devices for electronic devices in various fields that display images.

(module)
The display device 1 according to the above-described embodiment is incorporated into various electronic devices such as application examples 1 to 5 described later, for example, as a module as illustrated in FIG. In this module, for example, a region 210 exposed from the sealing substrate 32 is provided on one side of the substrate 31, and the wiring of the drive circuit 20 is extended to the exposed region 210 to provide an external connection terminal (not shown). Formed. The external connection terminal may be provided with a flexible printed circuit (FPC) 220 for signal input / output.

(Application example 1)
FIG. 10 illustrates an appearance of a television device to which the display device 1 of the above embodiment is applied. The television apparatus has, for example, a video display screen unit 300 including a front panel 310 and a filter glass 320. The video display screen unit 300 is configured by the display device 1 according to each of the above embodiments. Yes.

(Application example 2)
FIG. 11 shows the appearance of a digital camera to which the display device 1 of the above embodiment is applied. The digital camera includes, for example, a flash light emitting unit 410, a display unit 420, a menu switch 430, and a shutter button 440. The display unit 420 is configured by the display device 1 according to the above embodiment. Yes.

(Application example 3)
FIG. 12 shows the appearance of a notebook personal computer to which the display device 1 of the above embodiment is applied. The notebook personal computer has, for example, a main body 510, a keyboard 520 for inputting characters and the like, and a display unit 530 for displaying an image. The display unit 530 is a display according to each of the above embodiments. The apparatus 1 is configured.

(Application example 4)
FIG. 13 shows the appearance of a video camera to which the display device 1 of the above embodiment is applied. This video camera has, for example, a main body 610, a subject photographing lens 620 provided on the front side surface of the main body 610, a start / stop switch 630 at the time of photographing, and a display 640. Reference numeral 640 denotes the display device 1 according to each of the above embodiments.

(Application example 5)
FIG. 14 shows the appearance of a mobile phone to which the display device 1 of the above embodiment is applied. For example, the mobile phone is obtained by connecting an upper housing 710 and a lower housing 720 with a connecting portion (hinge portion) 730, and includes a display 740, a sub-display 750, a picture light 760, and a camera 770. Yes. The display 740 or the sub-display 750 is configured by the display device 1 according to each of the above embodiments.

  The present invention has been described above with the embodiments and application examples. However, the present invention is not limited to the above-described embodiments and the like, and various modifications can be made.

  For example, in the above-described embodiment, the case where the display device 1 is an active matrix type has been described. However, the configuration of the pixel circuit 13 for driving the active matrix is not limited to that described in the above-described embodiment, and is necessary. Depending on the case, a capacitor or a transistor may be added to the pixel circuit 14. In that case, a necessary drive circuit may be added in addition to the signal line drive circuit 23, the scanning line drive circuit 24, and the power supply line drive circuit 25 described above in accordance with the change of the pixel circuit 14.

  In the above embodiment and the like, the timing control circuit 22 controls the driving of the signal line driving circuit 23, the scanning line driving circuit 24, and the power supply line driving circuit 25, but other circuits control these driving. You may do it. The control of the signal line drive circuit 23, the scanning line drive circuit 24, and the power supply line drive circuit 25 may be performed by hardware (circuit) or software (program).

  In the above-described embodiment and the like, the pixel circuit 14 has a 2Tr1C circuit configuration. However, if the transistor includes a circuit configuration in which the transistor is connected in series to the organic EL element 11, the 2Tr1C circuit configuration is used. A circuit configuration other than the configuration may be employed.

Further, in the above-described embodiment and the like, the case where the drive transistor Tr ₁ and the write transistor Tr ₂ are formed by n-channel MOS thin film transistors (TFTs) is illustrated, but a p-channel transistor is exemplified. (For example, a p-channel MOS type TFT) may be used. However, in this case, the source and drain of the transistor Tr ₂ that are not connected to the power supply line PSL and the other end of the storage capacitor C _s are connected to the cathode of the organic EL element 11 and the anode of the organic EL element 11 is connected. Is preferably connected to GND or the like.

DESCRIPTION OF SYMBOLS 1 ... Display apparatus, 10 ... Display panel, 11, 11R, 11G, 11B ... Organic EL element, 12 ... Pixel, 13 ... Pixel circuit array part, 14 ... Pixel circuit, 20 ... Drive circuit, 20A ... Video signal, 20B ... Sync signal, 21 ... Video signal processing circuit, 21A ... Movie still image detection circuit, 21B ... Duty control circuit, 22 ... Timing generation circuit, 22A ... Control signal, 23 ... Signal line drive circuit, 24 ... Scanning line drive circuit, 25 ... power line drive circuit, C _s ... holding capacitor, DTL ... signal line, GND ... ground line, I _d ... current, PSL ... power line, Tr ₁ ... drive transistor, Tr ₂ ... write transistor, V _g ... gate voltage, V _gs ... gate-source voltage, V _s ... source voltage, V _th ... threshold voltage, WSL ... scanning line.

Claims (5)

A plurality of scanning lines arranged in a row, a plurality of signal lines arranged in a column, a plurality of light emitting elements arranged in a matrix corresponding to the intersection of each scanning line and each signal line, and a plurality of light emitting elements A pixel circuit array unit including a pixel circuit of
A detection circuit for detecting a video signal corresponding to a moving image and a video signal corresponding to a still image included in the video signal for one frame;
The duty ratio of the video signal corresponding to the still image is set to a small value and the size of the video signal corresponding to the video is changed according to the size of the duty ratio. And a duty control circuit that changes the magnitude of the video signal corresponding to the still image according to the magnitude of the duty ratio,
A signal voltage corresponding to a video signal having a size set by the duty control circuit is sequentially applied to each signal line to perform writing to a pixel circuit to be selected, and a duty ratio set by the duty control circuit A signal line driving circuit for sequentially applying a selection voltage corresponding to the size of each signal line to perform writing to a pixel circuit to be selected; and
And a scanning line driving circuit that sequentially applies a selection pulse to the plurality of scanning lines to sequentially select the plurality of light emitting elements and the plurality of pixel circuits. The scanning line driving circuit applies, to the scanning line, a selection pulse having a peak value smaller than a peak value of a selection pulse applied in other periods when the selection voltage is applied to the signal line. The display device according to 1. 2. The detection circuit detects a video signal corresponding to the moving image and a video signal corresponding to the still image by comparing a video signal for one frame with a video signal one frame before the frame. Or the display apparatus of Claim 2. A plurality of scanning lines arranged in a row, a plurality of signal lines arranged in a column, a plurality of light emitting elements arranged in a matrix corresponding to the intersection of each scanning line and each signal line, and a plurality of light emitting elements Preparing a display device comprising: a pixel circuit array unit including the pixel circuit; and a drive circuit for driving the pixel circuit array unit;
After detecting the video signal corresponding to the moving image and the video signal corresponding to the still image included in the video signal for one frame, the duty ratio of the video signal corresponding to the moving image is set to a small value and the duty ratio is large. The video signal corresponding to the moving image is changed in accordance with the video signal, the duty ratio of the video signal corresponding to the still image is set to a large value, and the video corresponding to the still image according to the size of the duty ratio is set. Changing the magnitude of the signal;
A signal voltage corresponding to a video signal having a size set by the duty control circuit is sequentially applied to each signal line to perform writing to a pixel circuit to be selected, and a duty ratio set by the duty control circuit Sequentially applying a selection voltage corresponding to the size of each signal line to write to the pixel circuit to be selected;
A step of sequentially applying a selection pulse to a plurality of scanning lines to sequentially select the plurality of light emitting elements and the plurality of pixel circuits. A display device,
The display device
A plurality of scanning lines arranged in a row, a plurality of signal lines arranged in a column, a plurality of light emitting elements arranged in a matrix corresponding to the intersection of each scanning line and each signal line, and a plurality of light emitting elements A pixel circuit array unit including a pixel circuit of
A detection circuit for detecting a video signal corresponding to a moving image and a video signal corresponding to a still image included in the video signal for one frame;
The duty ratio of the video signal corresponding to the still image is set to a small value and the size of the video signal corresponding to the video is changed according to the size of the duty ratio. And a duty control circuit that changes the magnitude of the video signal corresponding to the still image according to the magnitude of the duty ratio,
A signal voltage corresponding to a video signal having a size set by the duty control circuit is sequentially applied to each signal line to perform writing to a pixel circuit to be selected, and a duty ratio set by the duty control circuit A signal line driving circuit for sequentially applying a selection voltage corresponding to the size of each signal line to perform writing to a pixel circuit to be selected; and
An electronic apparatus comprising: a scanning line driving circuit that sequentially applies a selection pulse to the plurality of scanning lines to sequentially select the plurality of light emitting elements and the plurality of pixel circuits.

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