JP2008249744A - Display device, driving method of display device, and electronic equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To decrease the number of elements constituting a pixel circuit and the number of wiring lines, and to minimize an influence of characteristic variance of transistors regarding driving timing of an electrooptical element. <P>SOLUTION: A display device is so configured that source potentials (Vccp/Vini) supplied from a power supply scan circuit 50 to a driving transistor 22 can be switched, and while the driving transistor 22 is used in common as a transistor controlling light-emission period/non-light emission period of an organic EL element 21, a signal write preparation period is provided to temporary hold the signal voltage Vsig of a video signal which is written first in a second holding capacitor 27 in the signal write preparation period. Then a voltage (for example, 2Vsig) higher than the signal voltage Vsig of the video signal is written to a first holding capacitor 26, and then the signal voltage Vsig temporarily held in the second holding capacitor 27 is written in the first holding capacitor 26. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a display device, a display device driving method, and an electronic apparatus, and more particularly to a flat (flat panel) display device in which pixels including electro-optical elements are arranged in a matrix (matrix shape), and the display device And an electronic apparatus having the display device.

  In recent years, in the field of display devices that perform image display, flat display devices in which pixels (pixel circuits) including light emitting elements are arranged in a matrix are rapidly spreading. As a flat display device, as a light emitting element of a pixel, a so-called current-driven electro-optical element whose light emission luminance changes according to a current value flowing through the device, for example, a phenomenon that emits light when an electric field is applied to an organic thin film is used. An organic EL display device using an organic EL (Electro Luminescence) element has been developed and commercialized.

  The organic EL display device has the following features. That is, since the organic EL element can be driven with an applied voltage of 10 V or less, it has low power consumption and is a self-luminous element. Therefore, for each pixel including the liquid crystal cell, the liquid crystal cell emits light from the light source (backlight). Compared to a liquid crystal display device that displays an image by controlling the light intensity, the image is highly visible, and the liquid crystal display device does not require an illumination member such as a backlight. Is easy. Furthermore, since the response speed of the organic EL element is as high as about several μsec, an afterimage at the time of displaying a moving image does not occur.

  In the organic EL display device, as in the liquid crystal display device, a simple (passive) matrix method and an active matrix method can be adopted as the driving method. However, although the simple matrix display device has a simple structure, the light-emission period of the electro-optic element decreases with an increase in the number of scanning lines (that is, the number of pixels), thereby realizing a large-sized and high-definition display device. There are problems such as difficult.

  Therefore, in recent years, the current flowing through the electro-optical element is controlled by an active element provided in the same pixel circuit as the electro-optical element, for example, an insulated gate field effect transistor (generally, a TFT (Thin Film Transistor)). Active matrix display devices have been actively developed. An active matrix display device can easily realize a large-sized and high-definition display device because the electro-optic element continues to emit light over a period of one frame.

  By the way, it is generally known that the IV characteristic (current-voltage characteristic) of the organic EL element is deteriorated with time (so-called deterioration with time). In a pixel circuit using an N-channel TFT as a transistor for driving an organic EL element with current (hereinafter referred to as “driving transistor”), the organic EL element is connected to the source side of the driving transistor. When the IV characteristic of the organic EL element deteriorates with time, the gate-source voltage Vgs of the driving transistor changes, and as a result, the emission luminance of the organic EL element also changes.

  This will be described more specifically. The source potential of the drive transistor is determined by the operating point of the drive transistor and the organic EL element. When the IV characteristic of the organic EL element deteriorates, the operating point of the driving transistor and the organic EL element fluctuates. Therefore, even if the same voltage is applied to the gate of the driving transistor, the source potential of the driving transistor changes. To do. As a result, since the source-gate voltage Vgs of the drive transistor changes, the value of the current flowing through the drive transistor changes. As a result, since the value of the current flowing through the organic EL element also changes, the light emission luminance of the organic EL element changes.

  In addition, in a pixel circuit using a polysilicon TFT, in addition to the deterioration over time of the IV characteristics of the organic EL element, the threshold voltage Vth of the driving transistor and the mobility of the semiconductor thin film that constitutes the channel of the driving transistor (hereinafter referred to as the following) Μ described as “driving transistor mobility” changes with time, and the threshold voltage Vth and mobility μ vary from pixel to pixel due to variations in the manufacturing process (individual transistor characteristics vary).

  If the threshold voltage Vth and mobility μ of the driving transistor differ from pixel to pixel, the current value flowing through the driving transistor varies from pixel to pixel. Therefore, even if the same voltage is applied to the gate of the driving transistor between the pixels, The light emission luminance of the EL element varies among the pixels, and as a result, the uniformity of the screen is lost.

  Therefore, even if the IV characteristic of the organic EL element deteriorates with time, or the threshold voltage Vth or mobility μ of the driving transistor changes with time, the light emission luminance of the organic EL element is not affected by those effects. In order to keep constant, the compensation function for the characteristic variation of the organic EL element, the correction for the variation of the threshold voltage Vth of the driving transistor (hereinafter referred to as “threshold correction”), the mobility μ of the driving transistor Each pixel circuit is provided with a correction function for correction of fluctuations (hereinafter referred to as “mobility correction”) (see, for example, Patent Document 1).

  As described above, each of the pixel circuits has the compensation function for the characteristic variation of the organic EL element and the correction function for the threshold voltage Vth and the mobility μ of the driving transistor, so that the IV characteristic of the organic EL element is improved. Even if the deterioration with time or the threshold voltage Vth or mobility μ of the driving transistor changes with time, the light emission luminance of the organic EL element can be kept constant without being affected by them.

JP 2006-133542 A

  However, since the conventional technique described in Patent Document 1 employs a configuration in which a switching transistor is added to realize a correction function for fluctuations in threshold voltage Vth and mobility μ, the number of elements constituting the pixel circuit is large. This hinders miniaturization of the pixel size and hence high definition of the display device.

  Furthermore, the switching transistor is connected in series to the driving transistor for driving the organic EL element, and the light emission period / non-light emission period of the organic EL element is controlled by the conduction / non-conduction of the switching transistor. In addition, the driving timing of the organic EL element is affected by variations in characteristics of the two transistors, the driving transistor and the switching transistor.

  Therefore, the present invention aims to reduce the number of elements and the number of wirings that constitute a pixel circuit, and to minimize the influence of transistor characteristic variations on the drive timing of the electro-optical element, and the display apparatus An object of the present invention is to provide a driving method and an electronic apparatus having the display device.

  To achieve the above object, the first invention includes an electro-optic element, a drive transistor that drives the electro-optic element, a first writing transistor having one electrode connected to a gate electrode of the drive transistor, A second write transistor connected between the other electrode of the write transistor and a signal line; a first storage capacitor connected between a gate electrode and a source electrode of the drive transistor; A pixel in which pixels including a third write transistor having one electrode connected to the common connection node of the write transistor and a second storage capacitor connected to the other electrode of the third write transistor are arranged in a matrix. In the display device having the array portion, each pixel of the pixel array portion is scanned in a row unit, and the first writing transistor A first scanning means for driving conduction / non-conduction, a voltage higher than a signal voltage of the video signal when the first writing transistor is in a non-conduction state, and then the first writing transistor is at least in a conduction state. Supply means for supplying the video signal to the signal line at a certain time, and scanning each pixel of the pixel array unit in a row unit, from the signal voltage of the video signal supplied to the signal line from the supply means A second scanning means for performing writing driving by the second writing transistor to write a higher voltage and the video signal, and each pixel of the pixel array unit is scanned in a row unit and written by the second writing transistor. A voltage higher than the signal voltage of the video signal is written to the second storage capacitor, and non-write by the second write transistor The third write transistor to write a voltage higher than the signal voltage of the video signal held in the second holding capacitor during the conduction period of the first write transistor to the first holding capacitor through the first write transistor. A third scanning means for performing write driving according to the above, scanning each pixel of the pixel array section in units of rows, and writing the video signal written by the second write transistor to the third holding capacitor, Writing by the fourth writing transistor to write the video signal held in the third holding capacitor during the conduction period of the first writing transistor during a non-writing period by the writing transistor to the first holding capacitor through the first writing transistor Fourth scanning means for driving, and the pixel array section And a fifth scanning unit that selectively supplies a first potential and a second potential lower than the first potential to a power supply line that is wired for each pixel row and supplies a current to the driving transistor. The provided structure is adopted.

  In the display device having the above structure and the electronic apparatus having the display device, current is supplied from the power supply line by selectively supplying the first potential and the second potential from the fourth scanning unit to the power supply line. The drive transistor that receives the signal drives the electro-optical element to emit light when the first potential is supplied, and does not emit light when the second potential is supplied. That is, the drive transistor has a function of controlling the light emission period / non-light emission period of the electro-optical element.

  When the electro-optic element is driven to emit light, a video signal is supplied to the signal line during the non-conduction period of the first writing transistor, and then a voltage higher than the signal voltage of the video signal when the first writing transistor is at least conductive. On the other hand, these are sequentially written in the pixel by the second writing transistor, and the video signal is written in the second holding capacitor by the third writing transistor and temporarily held. At this time, a voltage higher than the signal voltage of the video signal is written into the first storage capacitor through the first write transistor because the first write transistor is in a conductive state at the time of writing. Thereafter, the video signal held in the second holding capacitor is written to the first holding capacitor through the first writing transistor by writing by the third writing transistor.

  By this writing drive, a voltage higher than the signal voltage of the video signal is written first, and then the video signal is written. Therefore, the gate potential of the driving transistor is faster than the video signal signal voltage is written directly. Rise up to the signal voltage. That is, the writing of the signal voltage of the video signal can be completed instantaneously without being affected by variations in the driving capabilities of the first and second write transistors and the time constant between the write transistors and the first storage capacitor. Thus, the mobility correction operation can be started in a state where the signal voltage of the video signal is sufficiently written.

  To achieve the above object, the second invention provides an electro-optical element, a driving transistor for driving the electro-optical element, a first writing transistor having one electrode connected to a gate electrode of the driving transistor, A second write transistor connected between the other electrode of the write transistor and a signal line; a first storage capacitor connected between a gate electrode and a source electrode of the drive transistor; A third write transistor having one electrode connected to a common connection node of the write transistor, a second storage capacitor connected to the other electrode of the third write transistor, and a common connection of the first and second write transistors A fourth write transistor having one electrode connected to the node and the other electrode of the fourth write transistor; In a display device having a pixel array unit in which pixels including a third storage capacitor that is connected are arranged in a matrix, each pixel in the pixel array unit is scanned in units of rows, and the first write transistor is turned on. / A first scanning means for driving non-conducting, a voltage higher than the signal voltage of the video signal when the first writing transistor is non-conducting, and then the first writing transistor is at least conducting Sometimes the supply means for supplying the video signal to the signal line, and each pixel of the pixel array unit is scanned in a row unit, and the signal voltage of the video signal supplied from the supply means to the signal line Second scanning means for performing writing driving by the second writing transistor to write a high voltage and the video signal, and each pixel of the pixel array section are arranged in a row. And a voltage higher than the signal voltage of the video signal written by the second writing transistor is written to the second storage capacitor, and the first writing transistor is turned on in a non-writing period by the second writing transistor. Third scanning means for performing write driving by the third write transistor so as to write a voltage higher than the signal voltage of the video signal held in the second hold capacitor during the period to the first hold capacitor through the first write transistor. Each pixel of the pixel array unit is scanned in a row unit, the video signal written by the second write transistor is written to the third storage capacitor, and the first signal is written in the non-write period by the second write transistor. Held in the third holding capacitor during the conduction period of one write transistor. The video signal is wired for each pixel row of the pixel array unit, and the fourth scanning means performs writing driving by the fourth writing transistor to write the video signal to the first storage capacitor through the first writing transistor. The power supply line for supplying current to the transistor is provided with a fifth scanning unit that selectively supplies a first potential and a second potential lower than the first potential.

  In the display device having the above structure and the electronic apparatus having the display device, current is supplied from the power supply line by selectively supplying the first potential and the second potential from the fifth scanning unit to the power supply line. The drive transistor that receives the signal drives the electro-optical element to emit light when the first potential is supplied, and does not emit light when the second potential is supplied. That is, the drive transistor has a function of controlling the light emission period / non-light emission period of the electro-optical element.

  When the electro-optic element is driven to emit light, a voltage higher than the signal voltage of the video signal is supplied during the non-conduction period of the first writing transistor, and then the video signal is supplied to the signal line when the first writing transistor is at least conductive. On the other hand, these are sequentially written in the pixel by the second writing transistor, and a voltage higher than the signal voltage of the video signal is written to the second holding capacitor by the third writing transistor and temporarily held, and the video signal is held by the fourth writing transistor. To write to the third holding capacitor and hold once. In the conduction period of the first writing transistor, first, a voltage higher than the signal voltage of the video signal held in the second holding capacitor is written to the first holding capacitor through the first writing transistor by writing by the third writing transistor. Then, the video signal held in the third holding capacitor is written to the first holding capacitor through the first writing transistor by writing by the fourth writing transistor.

  By this writing drive, a voltage higher than the signal voltage of the video signal is written first, and then the video signal is written. Therefore, the gate potential of the driving transistor is faster than the video signal signal voltage is written directly. Rise up to the signal voltage. That is, the writing of the signal voltage of the video signal can be completed instantaneously without being affected by variations in the driving capabilities of the first and second write transistors and the time constant between the write transistors and the first storage capacitor. Thus, the mobility correction operation can be started in a state where the signal voltage of the video signal is sufficiently written.

  According to the present invention, since the drive transistor has a function of controlling the light emission period / non-light emission period of the electro-optic element, the dedicated transistor for controlling the light emission period / non-light emission period can be omitted. The number of elements and the number of wirings constituting the pixel circuit can be reduced, and the influence on the drive timing of the electro-optical element can be limited by the characteristic variation of one transistor.

  In addition, by entering the mobility correction operation in a state where the video signal signal voltage has been sufficiently written, both the video signal signal voltage writing and mobility correction operations can be performed stably. For this reason, variations in mobility correction among pixels can be eliminated and image quality can be improved.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[First Embodiment]
FIG. 1 is a system configuration diagram showing an outline of the configuration of the active matrix display device according to the first embodiment of the present invention. Here, as an example, an active matrix organic EL display device using, as an example, a current-driven electro-optic element whose emission luminance changes according to the value of current flowing through the device, for example, an organic EL element as a light-emitting element of a pixel (pixel circuit) This case will be described as an example.

  As shown in FIG. 1, the organic EL display device 10 </ b> A according to the present embodiment includes a pixel array unit 30 in which pixels (PXLC) 20 </ b> A are two-dimensionally arranged in a matrix (matrix shape), and the pixel array unit 30. Drive units arranged in the periphery and driving each pixel 20A, for example, first, second, and third write scanning circuits (first, second, and third scanning means) 40A, 40B, and 40C, a power supply scanning circuit (first) 4 scanning means) 50 and a horizontal drive circuit (supply means) 60.

  The pixel array unit 30 includes first, second, and third scanning lines 31A-1 to 31A-m, 31B-1 to 31B-m, and 31C- for each pixel row with respect to a pixel array of m rows and n columns. 1 to 31C-m and power supply lines 32-1 to 32-m are wired, and signal lines 33-1 to 33-n are wired for each pixel column.

  The pixel array unit 30 is usually formed on a transparent insulating substrate such as a glass substrate, and has a flat (flat) panel structure. Each pixel 20A of the pixel array section 30 can be formed using an amorphous silicon TFT (Thin Film Transistor) or a low-temperature polysilicon TFT. When the low-temperature polysilicon TFT is used, the display panel (the pixel array section 30) is formed for the first, second, and third write scanning circuits 40A, 40B, and 40C, the power supply scanning circuit 50, and the horizontal drive circuit 60. Substrate) 70.

  The first, second, and third write scanning circuits 40A, 40B, and 40C are configured by a shift register that sequentially shifts (transfers) the start pulse sp in synchronization with the clock pulse ck, and each pixel 20A of the pixel array unit 30 When video signals are written to the scanning lines, scanning signals WSA1 to WSAm, WSB1 to WSBm, and WSC1 to WSCm are sequentially supplied to the scanning lines 31A-1 to 31A-m, 31B-1 to 31B-m, and 31C-1 to 31C-m. Then, the pixels 20A are sequentially scanned (line sequential scanning) in units of rows.

  The power supply scanning circuit 50 is configured by a shift register or the like that sequentially shifts the start pulse sp in synchronization with the clock pulse ck. The power supply scanning circuit 50 is synchronized with the line sequential scanning by the write scanning circuits 40A, 40B, and 40C. By supplying power supply line potentials DS1 to DSm, which are switched at a second potential Vini lower than the first potential Vccp, to the power supply lines 32-1 to 32-m, conduction of a drive transistor 22 (see FIG. 2) described later is performed. (ON) / non-conduction (OFF) control is performed.

  The horizontal drive circuit 60 appropriately selects any one of a signal voltage Vsig of a video signal corresponding to luminance information supplied from a signal supply source (not shown), a voltage higher than the signal voltage Vsig, and an offset voltage Vofs. Then, data is simultaneously written to each pixel 20A of the pixel array unit 30 through the signal lines 33-1 to 33-n, for example, in units of rows. That is, the horizontal driving circuit 60 adopts a line-sequential writing driving mode in which the signal voltage Vsig of the video signal is written all at once in a row (line) unit.

  Here, the offset voltage Vofs is a reference voltage (e.g., corresponding to a black level) of a signal voltage of a video signal (hereinafter sometimes simply referred to as “signal voltage”) Vsig. The second potential Vini is set to Vofs−Vth> Vini when the potential is sufficiently lower than the offset voltage Vofs, for example, when the threshold voltage of the drive transistor 22 is Vth.

  Further, as the voltage higher than the signal voltage Vsig of the video signal, a voltage corresponding to the signal voltage Vsig of the video signal, for example, a voltage 2Vsig that is twice the signal voltage Vsig is set. However, the voltage is not limited to the voltage corresponding to the signal voltage Vsig of the video signal, and a voltage higher than the signal voltage Vsig of the video signal by a certain value can be set.

(Pixel circuit)
FIG. 2 is a circuit diagram illustrating a specific configuration example of the pixel (pixel circuit) 20A. As shown in FIG. 2, the pixel 20 </ b> A has a current-driven electro-optical element, for example, an organic EL element 21, whose light emission luminance changes according to a current value flowing through the device, as the light-emitting element. In addition, the drive transistor 22, the first, second and third write transistors (sampling transistors) 23, 24, 25 and the first and second storage capacitors 26, 27 are provided.

  Here, N-channel TFTs are used as the drive transistor 22 and the first, second, and third write transistors 23, 24, and 25. However, the combination of the conductivity types of the drive transistor 22 and the write transistors 23, 24, and 25 here is only an example, and is not limited to these combinations.

  The organic EL element 21 has a cathode electrode connected to a common power supply line 34 wired in common to all the pixels 20A. The drive transistor 22 has a source electrode connected to the anode electrode of the organic EL element 21 and a drain electrode connected to the power supply line 32 (32-1 to 32-m).

  The first writing transistor 23 has a gate electrode connected to the first scanning line 31 </ b> A (31 </ b> A- 1 to 31 </ b> A-m) and one electrode (drain electrode / source electrode) connected to the gate electrode of the driving transistor 22. .

  The second write transistor 24 has a gate electrode connected to the second scanning line 31B (31B-1 to 31B-m), and one electrode (source electrode / drain electrode) connected to the signal line 33 (33-1 to 33-n). The other electrode (drain electrode / source electrode) is connected to the other electrode (source electrode / drain electrode) of the first writing transistor 23.

  The third write transistor 25 has a gate electrode connected to the third scanning line 31C (31C-1 to 31C-m), and one electrode (drain electrode / source electrode) connected to the other electrode of the second write transistor 24 and the second electrode. One write transistor 23 is connected to the common connection node N11 with the other electrode.

  One end (one electrode) of the first storage capacitor 26 is connected to a common connection node N12 between the gate electrode of the drive transistor 22 and the other electrode of the first write transistor 23, and the other end (the other electrode) is connected to the drive transistor. The node 22 is connected to a common connection node N13 between the source electrode 22 and the anode electrode of the organic EL element 21.

  The second storage capacitor 27 has one end (one electrode) connected to the other electrode (source electrode / drain electrode) of the third write transistor 25 and the other end (the other electrode) connected to the common power supply line 34. ing.

(Pixel structure)
FIG. 3 shows an example of a cross-sectional structure of the pixel 20A. As shown in FIG. 3, the pixel 20A includes an insulating film 202 and a window insulating film on a glass substrate 201 on which pixel circuits such as a driving transistor 22, first, second, and third writing transistors 23, 24, and 25 are formed. 203 is formed, and the organic EL element 21 is provided in the recess 203A of the window insulating film 203.

  The organic EL element 21 includes an anode electrode 204 made of metal or the like formed on the bottom of the recess 203A of the window insulating film 203, and an organic layer (electron transport layer, light emitting layer, hole transport) formed on the anode electrode 204. Layer / hole injection layer) 205 and a cathode electrode 206 made of a transparent conductive film or the like formed on the organic layer 205 in common for all pixels.

  In the organic EL element 21, the organic layer 208 is formed by sequentially depositing a hole transport layer / hole injection layer 2051, a light emitting layer 2052, an electron transport layer 2053 and an electron injection layer (not shown) on the anode electrode 204. It is formed. Then, current flows from the drive transistor 22 to the organic layer 205 through the anode electrode 204 under current drive by the drive transistor 22 in FIG. 2, whereby electrons and holes are recombined in the light emitting layer 2052 in the organic layer 205. It is designed to emit light.

  As shown in FIG. 3, after the organic EL elements 21 are formed on the glass substrate 201 on which the pixel circuit is formed via the insulating film 202 and the window insulating film 203 in units of pixels, the organic EL element 21 is interposed via the passivation film 207. The sealing substrate 208 is bonded by the adhesive 209, and the organic EL element 21 is sealed by the sealing substrate 208, whereby the display panel 70 is formed.

(Threshold correction function)
Here, in the power supply scanning circuit 50, after the first and second write transistors 23 and 24 are turned on, the horizontal drive circuit 60 supplies the offset voltage Vofs to the signal lines 33 (33-1 to 33-n). During this time, the potential DS of the power supply line 33 is switched from the second potential Vini to the first potential Vccp. By switching the potential DS of the power supply line 32, a voltage corresponding to the threshold voltage Vth of the driving transistor 22 is held in the first holding capacitor 26.

  The voltage corresponding to the threshold voltage Vth of the driving transistor 22 is held in the first holding capacitor 26 for the following reason.

  Due to variations in the manufacturing process of the drive transistor 22 and changes over time, transistor characteristics such as the threshold voltage Vth and mobility μ of the drive transistor 22 vary from pixel to pixel. Due to this variation in transistor characteristics, even if the same gate potential is applied to the drive transistor 22 between pixels, the drain-source current (drive current) Ids varies from pixel to pixel, resulting in variations in light emission luminance. In order to cancel (correct) the influence of the variation of the threshold voltage Vth for each pixel, the voltage corresponding to the threshold voltage Vth is held in the first holding capacitor 26.

  The threshold voltage Vth of the driving transistor 22 is corrected as follows. That is, by holding the threshold voltage Vth in the first holding capacitor 26 in advance, the threshold voltage Vth of the driving transistor 22 is set to the first holding capacitor 26 when the driving transistor 22 is driven by the signal voltage Vsig of the video signal. Is offset with the voltage corresponding to the threshold voltage Vth held in the above, in other words, the threshold voltage Vth is corrected.

  This is the threshold correction function. With this threshold correction function, even if the threshold voltage Vth varies or changes with time for each pixel, the light emission luminance of the organic EL element 21 can be kept constant without being influenced by the threshold voltage Vth. The principle of threshold correction will be described in detail later.

(Mobility correction function)
The pixel 20A illustrated in FIG. 2 has a mobility correction function in addition to the threshold correction function described above. Specifically, a scan output from the first write scanning circuit 40A during a period in which the horizontal drive circuit 60 supplies the signal voltage Vsig of the video signal to the signal lines 33A (33A-1 to 33A-n). In the period in which the first write transistor 23 is turned on in response to the signal WSA (WSA1 to WSAm), that is, in the mobility correction period, the signal voltage Vsig of the video signal is held in the first holding capacitor 26. Mobility correction is performed to cancel the dependence of the drain-source current Ids on the mobility μ. The specific principle and operation of this mobility correction will be described later.

(Bootstrap function)
The pixel 20A shown in FIG. 2 further has a bootstrap function. Specifically, the first writing scanning circuit 40A scans the scanning signal WSA (WSA1 to WSA1) for the scanning lines 31A (31A-1 to 31A-m) when the signal voltage Vsig of the video signal is held in the first holding capacitor 26. WSAm) is released, the first write transistor 23 is turned off, and the gate electrode of the drive transistor 22 is electrically disconnected from the common connection node N11 to be in a floating state.

  When the gate electrode of the driving transistor 22 is in a floating state, the first storage capacitor 26 is connected between the gate and the source of the driving transistor 22, so that when the source potential Vs of the driving transistor 22 fluctuates, Since the gate potential Vg of the drive transistor 22 also fluctuates in conjunction with (follows) the fluctuation, the gate-source voltage Vgs of the drive transistor 22 is kept constant.

  As described above, the operation of the first storage capacitor 26 causes the gate potential Vg of the driving transistor 22 to follow the source potential Vs and the gate-source voltage Vgs is kept constant as the bootstrap operation. By this bootstrap operation, even if the IV characteristic of the organic EL element 21 changes with time, the light emission luminance of the organic EL element 21 can be kept constant.

  That is, even if the IV characteristic of the organic EL element 21 changes with time and the source potential Vs of the driving transistor 22 changes accordingly, the gate-source potential Vgs of the driving transistor 22 is kept constant by the bootstrap operation. In order to be maintained, the current flowing through the organic EL element 21 does not change, and therefore the emission luminance of the organic EL element 21 is also kept constant. As a result, even if the IV characteristic of the organic EL element 21 changes with time, it is possible to realize an image display that does not have a luminance deterioration associated therewith.

(Circuit operation of the organic EL display device according to the first embodiment)
Hereinafter, the circuit operation of the organic EL display device 10A according to the present embodiment will be described with reference to the operation charts of FIGS. 5 and 6 based on the timing chart of FIG. In the operation explanatory diagrams of FIGS. 5 and 6, the first, second, and third write transistors 23, 24, and 25 are illustrated by switch symbols for simplification of the drawings. Further, since the organic EL element 21 has a parasitic capacitance Cel, the parasitic capacitance Cel is also illustrated.

  In the timing chart of FIG. 4, the first, second, and third scanning lines 31A (31A-1 to 31A-m), 31B (31B-1 to 31B-m), and 31C (31C- 1-31C-m), changes in potential WSA, WSB, WSC, changes in potential DS of power supply lines 32 (32-1 to 32-m), and potentials of signal lines 33 (33-1 to 33-n). The change represents the change in the gate potential Vg and the source potential Vs of the driving transistor 22.

<Light emission period>
In the timing chart of FIG. 4, before the time t1, the organic EL element 21 is in a light emission state (light emission period). In this light emission period, the potential DS of the power supply line 32 is at the high potential Vccp (first potential), and the first, second, and third write transistors 23, 24, and 25 are all non-conductive.

  At this time, since the driving transistor 22 is set to operate in the saturation region, the gate-source voltage of the driving transistor 22 is supplied from the power supply line 32 through the driving transistor 22 as shown in FIG. A drive current (drain-source current) Ids corresponding to Vgs is supplied to the organic EL element 21. Therefore, the organic EL element 21 emits light with a luminance corresponding to the current value of the drive current Ids.

<Threshold correction preparation period>
At time t1, a new field of line sequential scanning is entered, and as shown in FIG. 5B, the potential DS of the power supply line 32 is sufficiently lower than the offset voltage Vofs of the signal line 33 from the high potential Vccp. It switches to the potential Vini (second potential). Here, when the threshold voltage of the organic EL element 21 is Vel and the potential of the common power supply line 34 is Vcath, if the low potential Vini is Vini <Vel + Vcath, the source potential Vs of the drive transistor 22 is substantially equal to the low potential Vini. Therefore, the organic EL element 21 is extinguished in a reverse bias state.

  Next, at time t2, the potentials WSA and WSB of the first and second scanning lines 31A and 31B transition from the low potential to the high potential, and as shown in FIG. Transistors 23 and 24 become conductive. At this time, since the offset voltage Vofs is supplied from the horizontal drive circuit 60 to the signal line 33, the gate potential Vg of the drive transistor 22 becomes the offset voltage Vofs. Further, the source potential Vs of the drive transistor 22 is at a potential Vini that is sufficiently lower than the offset voltage Vofs.

  At this time, the gate-source voltage Vgs of the drive transistor 22 is Vofs-Vini. If the gate-source voltage Vgs (= Vofs−Vini) is not larger than the threshold voltage Vth of the drive transistor 22, the above-described threshold value correction operation cannot be performed. Therefore, it is necessary to set Vofs−Vini> Vth. is there. In this way, the operation of fixing and fixing the gate potential Vg of the drive transistor 22 to the offset voltage Vofs and the source potential Vs to the low potential Vini is an operation for preparing for threshold correction.

<Threshold correction period>
Next, at time t3, as shown in FIG. 5D, when the potential DS of the power supply line 32 is switched from the low potential Vini to the high potential Vccp, the source potential Vs of the drive transistor 22 starts to rise. Soon, the gate-source voltage Vgs of the drive transistor 22 becomes the threshold voltage Vth of the drive transistor 22, and a voltage corresponding to the threshold voltage Vth is written into the first storage capacitor 26.

  Here, for convenience, a period during which a voltage corresponding to the threshold voltage Vth is written to the first storage capacitor 26 is referred to as a threshold correction period. In this threshold value correction period, a common power supply is provided so that the organic EL element 21 is cut off in order to prevent current from flowing exclusively to the first storage capacitor 26 side and not to the organic EL element 21 side. It is assumed that the potential Vcath of the line 34 is set.

<Signal writing preparation period>
Next, at time t4, the potentials WSA and WSB of the first and second scanning lines 31A and 31B transition from the high potential to the low potential, and as shown in FIG. Transistors 23 and 24 are turned off. At this time, the gate electrode of the driving transistor 22 is in a floating state, but the driving transistor 22 is in a cut-off state because the gate-source voltage Vgs is equal to the threshold voltage Vth of the driving transistor 22. Therefore, the drain-source current Ids does not flow.

  At time t4, the signal voltage Vsig of the video signal corresponding to the luminance information is supplied from the horizontal drive circuit 60 to the signal line 33. After that, at time t5, the potential WSB of the second scanning line 31B transitions from a low potential to a high potential, and then at time t6 after completion of the rise of the signal voltage Vsig, the potential WSC of the third scanning line 31C changes from the low potential. By transitioning to a high potential, as shown in FIG. 6A, the second and third write transistors 24 and 25 become conductive. As a result, the signal voltage Vsig is sampled by the third write transistor 25 and held in the second holding capacitor 27.

  Next, at time t7, the potential WSC of the third scanning line 31C transitions from a high potential to a low potential, and at the same time, the signal from the horizontal drive circuit 60 to the signal line 33 is replaced with the signal voltage Vsig of the video signal. A voltage higher than the voltage Vsig, for example, a voltage 2Vsig that is twice the signal voltage Vsig is supplied. At this time, as shown in FIG. 6B, since the second writing transistor 24 is in a conductive state, the potential of the node N11 becomes a voltage 2Vsig that is twice the signal voltage Vsig.

<Signal writing period & mobility correction period>
Next, at time t8 when the potential WSB of the second scanning line 31B is at a high potential, the potential WSA of the first scanning line 31A transitions from a low potential to a high potential, as shown in FIG. The first write transistor 23 becomes conductive again, samples the voltage 2Vsig that is twice the signal voltage Vsig, and writes it in the first storage capacitor 26. By the writing of the voltage 2Vsig, the gate potential Vg of the drive transistor 22 starts to increase toward the voltage 2Vsig.

  Next, at time t9, the potential WSB of the second scanning line 31B transitions from a high potential to a low potential, and at the same time, the potential WSC of the third scanning line 31C transitions from a low potential to a high potential. ), The second write transistor 24 is turned off and the third write transistor 25 is turned on. As a result, the signal voltage Vsig once held in the second storage capacitor 27 is written to the first storage capacitor 26 through the third write transistor 25 and the first write transistor 23.

  At this time, since the gate potential Vg of the drive transistor 22 is increasing toward the voltage 2Vsig, the gate potential Vg of the drive transistor 22 instantaneously reaches the signal voltage Vsig by writing the signal voltage Vsig. Then, when the drive transistor 22 is driven by the signal voltage Vsig of the video signal, the threshold voltage Vth of the drive transistor 22 is canceled with a voltage corresponding to the threshold voltage Vth held in the first holding capacitor 26. Correction is performed. The principle of threshold correction will be described later.

  At this time, since the organic EL element 21 is initially in a cut-off state (high impedance state), a current (drain-source current Ids) that flows from the power supply line 32 to the drive transistor 22 according to the signal voltage Vsig of the video signal. Flows into the parasitic capacitance Cel of the organic EL element 21. Therefore, charging of the parasitic capacitance Cel of the organic EL element 21 is started.

  Due to the charging of the parasitic capacitance Cel of the organic EL element 21, the source potential Vs of the drive transistor 22 rises with time. At this time, the variation in the threshold voltage Vth of the drive transistor 22 has already been corrected, and the drain-source current Ids of the drive transistor 22 depends on the mobility μ of the drive transistor 22.

  Eventually, when the source potential Vs of the drive transistor 22 rises to the potential of Vofs−Vth + ΔV, the gate-source voltage Vgs of the drive transistor 22 becomes Vsig−Vofs + Vth−ΔV. That is, the increase ΔV of the source potential Vs is subtracted from the voltage (Vsig−Vofs + Vth) held in the first holding capacitor 26, in other words, the charge of the first holding capacitor 26 is discharged. And negative feedback was applied. Therefore, the increase ΔV of the source potential Vs becomes a feedback amount of negative feedback.

  As described above, the drain-source current Ids flowing through the drive transistor 22 is negatively fed back to the gate input of the drive transistor 22, that is, the gate-source voltage Vgs, so that the drain-source current Ids of the drive transistor 22 is reduced. Mobility correction is performed to cancel the dependence on the mobility μ, that is, to correct the variation of the mobility μ for each pixel.

  More specifically, since the drain-source current Ids increases as the signal voltage Vsig of the video signal increases, the absolute value of the feedback amount (correction amount) ΔV of negative feedback also increases. Therefore, the mobility correction according to the light emission luminance level is performed. Further, when the signal voltage Vsig of the video signal is constant, the absolute value of the feedback amount ΔV of the negative feedback increases as the mobility μ of the driving transistor 22 increases, so that variation in the mobility μ for each pixel is removed. Can do. The principle of mobility correction will be described later.

<Light emission period>
Next, at time t10, the potential WSA of the first scanning line 31A transitions from a high potential to a low potential, so that the first writing transistor 23 becomes non-conductive as shown in FIG. The gate electrode of the transistor 22 is disconnected from the node N11. At the same time, the drain-source current Ids starts to flow through the organic EL element 21, whereby the anode potential of the organic EL element 21 rises according to the drain-source current Ids.

  The increase in the anode potential of the organic EL element 21 is nothing but the increase in the source potential Vs of the drive transistor 22. When the source potential Vs of the drive transistor 22 rises, the gate potential Vg of the drive transistor 22 also rises in conjunction with the bootstrap operation of the first storage capacitor 26.

  At this time, the increase amount of the gate potential Vg is equal to the increase amount of the source potential Vs. Therefore, the gate-source voltage Vgs of the drive transistor 22 is kept constant at Vsig + Vth−ΔV during the light emission period. At time t11, the potential WSC of the third scanning line 31C transitions from a high potential to a low potential, and at the same time, the potential of the signal line 33 is switched from the voltage 2Vsig, which is twice the signal voltage Vsig, to the offset voltage Vofs.

(Principle of threshold correction)
Here, the principle of threshold correction of the drive transistor 22 will be described. The drive transistor 22 operates as a constant current source because it is designed to operate in the saturation region. As a result, a constant drain-source current (drive current) Ids given by the following equation (1) is supplied from the drive transistor 22 to the organic EL element 21.
Ids = (1/2) · μ (W / L) Cox (Vgs−Vth) ² (1)
Here, W is the channel width of the drive transistor 22, L is the channel length, and Cox is the gate capacitance per unit area.

  FIG. 7 shows characteristics of the drain-source current Ids of the drive transistor 22 versus the gate-source voltage Vgs. As shown in this characteristic diagram, when correction for variation in the threshold voltage Vth of the drive transistor 22 is not performed, when the threshold voltage Vth is Vth1, the drain-source current Ids corresponding to the gate-source voltage Vgs becomes Ids1. On the other hand, when the threshold voltage Vth is Vth2 (Vth2> Vth1), the drain-source current Ids corresponding to the same gate-source voltage Vgs is Ids2 (Ids2 <Ids). That is, when the threshold voltage Vth of the driving transistor 22 varies, the drain-source current Ids varies even if the gate-source voltage Vgs is constant.

On the other hand, in the pixel (pixel circuit) 20A having the above configuration, as described above, the gate-source voltage Vgs of the driving transistor 22 at the time of light emission is Vsig−Vofs + Vth−ΔV. ), The drain-source current Ids is
Ids = (1/2) · μ (W / L) Cox (Vsig−Vofs−ΔV) ²
(2)
It is represented by

  That is, the term of the threshold voltage Vth of the drive transistor 22 is canceled, and the drain-source current Ids supplied from the drive transistor 22 to the organic EL element 21 does not depend on the threshold voltage Vth of the drive transistor 22. As a result, the drain-source current Ids does not vary even if the threshold voltage Vth of the drive transistor 22 varies for each pixel due to variations in the manufacturing process of the drive transistor 22 and changes over time. The emission brightness does not change.

(Principle of mobility correction)
Next, the principle of mobility correction of the drive transistor 22 will be described. FIG. 8 shows a characteristic curve in a state where a pixel A having a relatively high mobility μ of the driving transistor 22 and a pixel B having a relatively low mobility μ of the driving transistor 22 are compared. When the driving transistor 22 is composed of a polysilicon thin film transistor or the like, it is inevitable that the mobility μ varies between pixels like the pixel A and the pixel B.

  For example, when the signal voltage Vsig of the video signal of the same level is written in both the pixels A and B in the state where the mobility μ is varied between the pixel A and the pixel B, the movement is not performed. There is a large difference between the drain-source current Ids1 'flowing through the pixel A having a high degree μ and the drain-source current Ids2' flowing through the pixel B having a low mobility μ. Thus, if a large difference occurs between the pixels in the drain-source current Ids due to the variation in the mobility μ, the uniformity of the screen is impaired.

  Here, as is clear from the transistor characteristic equation of Equation (1), the drain-source current Ids increases when the mobility μ is large. Therefore, the feedback amount ΔV in the negative feedback increases as the mobility μ increases. As shown in FIG. 8, the feedback amount ΔV1 of the pixel A having a high mobility μ is larger than the feedback amount ΔV2 of the pixel V having a low mobility. Therefore, by negatively feeding back the drain-source current Ids of the drive transistor 22 to the signal voltage Vsig side of the video signal by the mobility correction operation, the larger the mobility μ, the more negative feedback is applied. Variation in degree μ can be suppressed.

  Specifically, when the feedback amount ΔV1 is corrected in the pixel A having a high mobility μ, the drain-source current Ids greatly decreases from Ids1 ′ to Ids1. On the other hand, since the feedback amount ΔV2 of the pixel B having a low mobility μ is small, the drain-source current Ids decreases from Ids2 ′ to Ids2, and does not decrease that much. As a result, since the drain-source current Ids1 of the pixel A and the drain-source current Ids2 of the pixel B are substantially equal, the variation in the mobility μ is corrected.

  In summary, when there are a pixel A and a pixel B having different mobility μ, the feedback amount ΔV1 of the pixel A having a high mobility μ is larger than the feedback amount ΔV2 of the pixel B having a low mobility μ. That is, the larger the mobility μ, the larger the feedback amount ΔV, and the larger the amount of decrease in the drain-source current Ids. Therefore, by negatively feeding back the drain-source current Ids of the driving transistor 22 to the signal voltage Vsig side, the current value of the drain-source current Ids of the pixels having different mobility μ is made uniform, and as a result, the mobility Variations in μ can be corrected.

  Here, in the pixel (pixel circuit) 20A shown in FIG. 2, the relationship between the signal potential (sampling potential) Vsig of the video signal and the drain-source current Ids of the drive transistor 22 depending on whether or not threshold correction and mobility correction are performed. This will be described with reference to FIG.

  In FIG. 9, (A) does not perform both threshold correction and mobility correction, (B) does not perform mobility correction, and performs only threshold correction, (C) performs threshold correction and mobility correction. Each case is shown. As shown in FIG. 9A, when neither threshold correction nor mobility correction is performed, the drain-source current Ids is caused by variations in the threshold voltage Vth and the mobility μ for each of the pixels A and B. A large difference occurs between the pixels A and B.

  On the other hand, when only the threshold correction is performed, as shown in FIG. 9B, although the variation in the drain-source current Ids can be reduced to some extent by the threshold correction, the pixels A and B having the mobility μ A difference in the drain-source current Ids between the pixels A and B due to the variation of each pixel remains.

  Then, by performing both the threshold correction and the mobility correction, as shown in FIG. 9C, the drain between the pixels A and B caused by the variation of the threshold voltage Vth and the mobility μ for each of the pixels A and B. -Since the difference between the source currents Ids can be almost eliminated, the luminance variation of the organic EL element 21 does not occur at any gradation, and a display image with good image quality can be obtained.

(Operational effects of the first embodiment)
As described above, according to the organic EL display device 10A according to the first embodiment, the power supply potential (Vccp / Vini) supplied from the power supply scanning circuit 50 to the drive transistor 22 of the pixel circuit can be switched. By providing the drive transistor 22 with a function of controlling the light emission period / non-light emission period of the organic EL element 21 by switching the power supply potential, a dedicated transistor for controlling the light emission period / non-light emission period is omitted, and the pixel circuit Since the number of elements and the number of wirings constituting the display can be reduced, it can greatly contribute to the miniaturization of the pixel size and the high definition of the display device.

  Further, since the drive transistor 22 is also used as a transistor for controlling the light emission period / non-light emission period of the organic EL element 21, the influence on the drive timing of the organic EL element 21 is affected by variations in characteristics of one transistor of the drive transistor 22. Therefore, it is possible to realize drive control of the organic EL element 21 that is less affected by variations in the characteristics of the transistors constituting the pixel circuit.

  Here, as in the case of the organic EL display device 10A according to the present embodiment, a problem in the case of adopting a configuration in which the signal voltage Vsig of the video signal is written by the first write transistor 23 and at the same time the operation for mobility correction is performed will be described. To do.

  As is clear from the description of the circuit operation described above, in the pixel circuit 20A having the configuration in which the driving transistor 22 is also used as a transistor for controlling the light emission period / non-light emission period of the organic EL element 21, the signal voltage Vsig of the video signal is written. At the same time, mobility correction starts. In order to reliably correct the variation μ of the mobility μ of the driving transistor 22 for each pixel, it is preferable to execute the mobility correction in a state where the signal voltage Vsig of the video signal is completely written.

  However, when the screen size is increased or the number of pixels is increased with the increase in definition, the wiring length of the signal line 33 for writing the signal voltage Vsig of the video signal is increased, so that the wiring resistance of the signal line 33 is reduced. growing. In addition, since the number of second write transistors 24 connected to the signal line 33 increases as the number of pixels increases, the parasitic capacitance of the signal line 33 increases.

  As described above, when the wiring resistance or parasitic capacitance of the signal line 33 is increased, the signal line 33 of the signal line 33 when the signal voltage Vsig of the video signal is supplied from the horizontal driving circuit 60 to the signal line 33 due to the time constant relationship. The fluctuation speed of the potential becomes slow (the response of the signal line potential is reduced).

  On the other hand, when the signal voltage Vsig of the video signal is simply written from the signal line 33 by the second writing transistor 23, the gate potential of the driving transistor 22 is related to the time constant between the second writing transistor 23 and the first storage capacitor 26. Although the rise of Vg is smoothed, the rise of the gate potential Vg of the drive transistor 22 is further smoothed by the slowing of the fluctuation speed of the potential of the signal line 33.

  Then, since it takes time until the signal voltage Vsig of the video signal is completely written, the unstable driving of entering the mobility correction while the signal voltage Vsig of the video signal is insufficiently written is performed. Become. As a result, the mobility correction correction amount, that is, the feedback amount ΔV of the negative feedback is different between the pixel having the high mobility μ and the pixel having the low mobility μ, and thus the mobility correction varies among the pixels. As a result, streaks occur and the image quality deteriorates.

  Therefore, in the present embodiment, a signal writing preparation period (t4-t8) is provided, and the signal voltage Vsig of the video signal written first in the signal writing preparation period is temporarily held in the second holding capacitor 27, and then the video signal A voltage higher than the signal voltage Vsig (eg, 2Vsig) is written to the node N12, and then the signal voltage Vsig once held in the second holding capacitor 27 is written to the node N12. Accordingly, a voltage higher than the signal voltage Vsig of the video signal is written to the node N12, that is, the gate electrode of the driving transistor 22 prior to the writing of the signal voltage Vsig (so-called precharge).

  In this way, by setting the signal writing preparation period and writing a voltage higher than the signal voltage Vsig as a precharge voltage prior to writing the signal voltage Vsig of the video signal, the wiring resistance and parasitic capacitance of the signal line 33 are set. Is large, the gate potential Vg of the drive transistor 22 rises to the signal voltage Vsig earlier than when the signal voltage Vsig of the video signal is directly written. That is, the signal voltage Vsig of the video signal is instantaneously written without being affected by variations in the driving ability of the first and second write transistors 23 and 24 and the time constant between the write transistors 23 and 24 and the storage capacitor 25. Can be completed.

  Accordingly, since it is possible to reduce the time until the signal voltage Vsig of the video signal is completely written, the mobility correction can be started in the state where the writing of the signal voltage Vsig of the video signal is completed. As a result, even if the screen size becomes larger or the number of pixels increases with higher definition, and the fluctuation speed of the potential of the first signal line 33A becomes slower, the signal line potential becomes rounded. The variation in mobility correction between the pixels due to this can be eliminated and the unevenness can be suppressed, so that the image quality can be improved.

[Second Embodiment]
FIG. 10 is a system configuration diagram showing an outline of the configuration of the active matrix display device according to the second embodiment of the present invention. In FIG. 10, the same parts as those in FIG. Here, as an example, an active matrix organic EL display device using, as an example, a current-driven electro-optic element whose emission luminance changes according to the value of current flowing through the device, for example, an organic EL element as a light-emitting element of a pixel (pixel circuit) This case will be described as an example.

  As shown in FIG. 10, the organic EL display device 10B according to this embodiment includes the components of the organic EL display device 10A according to the first embodiment, that is, the pixel array unit 30, the first, second, and third write scans. In addition to the circuits 40A, 40B, and 40C, the power supply scanning circuit 50, and the horizontal driving circuit 60, a fourth write scanning circuit 40D is provided. Here, the description of the configuration and operation of the same components as those of the organic EL display device 10A according to the first embodiment will be omitted because they overlap.

  In the pixel array section 30, corresponding to the fourth writing scanning circuit 40D, fourth scanning lines 31D-1 to 31D-m are wired for each pixel row. Similar to the first, second and third write scanning circuits 40A, 40B and 40C, the fourth write scanning circuit 40D is configured by a shift register or the like, and is used for writing a video signal to each pixel 20A of the pixel array unit 30. Then, the scanning signals WSD1 to WSDm are sequentially supplied to the scanning lines 31D-1 to 31D-m to scan the pixels 20B sequentially in units of rows.

(Pixel circuit)
FIG. 11 is a circuit diagram showing a specific configuration example of the pixel (pixel circuit) 20B. In FIG. 11, the same parts as those in FIG.

  As shown in FIG. 11, the pixel 20B includes the components of the pixel 20A described above, that is, the organic EL element 21, the drive transistor 22, the first, second, and third write transistors 23, 24, and 25, and the first and second elements. In addition to the storage capacitors 26 and 27, the fourth write transistor 28 and the third storage capacitor 29 are provided.

  Here, N-channel TFTs are used as the drive transistor 22 and the first, second, third and fourth write transistors 23, 24, 25 and 28. However, the combination of the conductivity types of the drive transistor 22 and the write transistors 23, 24, 25, and 28 here is merely an example, and is not limited to these combinations.

  The connection relationship between the organic EL element 21, the drive transistor 22, the first, second, and third write transistors 23, 24, and 25 and the first and second storage capacitors 26 and 27 is the same as that of the pixel 20A.

  The fourth write transistor 38 has a gate electrode connected to the fourth scan line 31D (31D-1 to 31D-m), and one electrode (drain electrode / source electrode) connected to the other electrode of the second write transistor 24 and the second electrode. One write transistor 23 is connected to the common connection node N11 with the other electrode.

  The third storage capacitor 29 has one end (one electrode) connected to the other electrode (source electrode / drain electrode) of the fourth write transistor 28 and the other end (the other electrode) connected to the common power supply line 34. ing.

  The pixel 20B having the above configuration has basically the same pixel structure as that of the pixel 20A shown in FIG. The main pixel 20B also has a threshold value correction function, a mobility correction function, and a bootstrap function, like the pixel 20A.

(Circuit Operation of Organic EL Display Device According to Second Embodiment)
Hereinafter, the circuit operation of the organic EL display device 10B according to the present embodiment will be described with reference to the operation charts of FIGS. 13 and 14 based on the timing chart of FIG. In the operation explanatory diagrams of FIGS. 13 and 14, the first, second, third, and third write transistors 23, 24, 25, and 28 are illustrated by switch symbols for simplification of the drawings. .

  In the timing chart of FIG. 12, the change in the potentials WSA, WSB, WSC, and WSD of the first, second, third, and fourth scanning lines 31A, 31B, 31C, and 31D and the power supply line 32 for a certain correction target pixel row. Represents a change in the potential DS, a change in the potential of the signal line 33, and a change in the gate potential Vg and the source potential Vs of the driving transistor 22.

<Light emission period>
In the timing chart of FIG. 4, before the time t1, the organic EL element 21 is in a light emission state (light emission period). In this light emission period, the potential DS of the power supply line 32 is at the high potential Vccp (first potential), and the first, second, third, and fourth write transistors 23, 24, 25, and 28 are all non-conductive. Is in a state.

  At this time, since the driving transistor 22 is set to operate in the saturation region, the gate-source voltage of the driving transistor 22 from the power supply line 32 through the driving transistor 22 as shown in FIG. A drive current (drain-source current) Ids corresponding to Vgs is supplied to the organic EL element 21. Therefore, the organic EL element 21 emits light with a luminance corresponding to the current value of the drive current Ids.

<Threshold correction preparation period>
At time t1, a new field of line sequential scanning is entered, and as shown in FIG. 13B, the potential DS of the power supply line 32 is sufficiently lower than the offset voltage Vofs of the signal line 33 from the high potential Vccp. It switches to the potential Vini (second potential). Here, if the low potential Vini is Vini <Vel + Vcath, the source potential Vs of the drive transistor 22 is substantially equal to the low potential Vini, and thus the organic EL element 21 is in a reverse bias state and extinguished.

  Next, at time t2, the potentials WSA and WSB of the first and second scanning lines 31A and 31B transition from the low potential to the high potential, and as shown in FIG. Transistors 23 and 24 become conductive. At this time, since the offset voltage Vofs is supplied from the horizontal drive circuit 60 to the signal line 33, the gate potential Vg of the drive transistor 22 becomes the offset voltage Vofs. Further, the source potential Vs of the drive transistor 22 is at a potential Vini that is sufficiently lower than the offset voltage Vofs.

  At this time, the gate-source voltage Vgs of the drive transistor 22 is Vofs-Vini. If the gate-source voltage Vgs (= Vofs−Vini) is not larger than the threshold voltage Vth of the driving transistor 22, the above-described threshold value correction operation cannot be performed. Therefore, it is necessary to set Vofs−Vini> Vth. is there. Thus, the threshold correction preparation operation for fixing the gate potential Vg of the drive transistor 22 to the offset voltage Vofs and the source potential Vs to the low potential Vini is completed.

<Threshold correction period>
Next, at time t3, as shown in FIG. 13D, when the potential DS of the power supply line 32 is switched from the low potential Vini to the high potential Vccp, the source potential Vs of the drive transistor 22 starts to rise. Soon, the gate-source voltage Vgs of the drive transistor 22 becomes the threshold voltage Vth of the drive transistor 22, and a voltage corresponding to the threshold voltage Vth is written into the first storage capacitor 26.

<Signal writing preparation period>
Next, at time t4, the potentials WSA and WSB of the first and second scanning lines 31A and 31B transition from a high potential to a low potential, and as shown in FIG. Transistors 23 and 24 are turned off. At this time, the gate electrode of the driving transistor 22 is in a floating state, but the driving transistor 22 is in a cut-off state because the gate-source voltage Vgs is equal to the threshold voltage Vth of the driving transistor 22. Therefore, the drain-source current Ids does not flow.

  Further, at the timing of time t4, a voltage higher than the signal voltage Vsig of the video signal, for example, a voltage 2Vsig that is twice the signal voltage Vsig is supplied from the horizontal drive circuit 60 to the signal line 33.

  After that, at time t5, the potential WSB of the second scanning line 31B transitions from a low potential to a high potential, and then at time t6 after completion of the rise of the signal voltage Vsig, the potential WSC of the third scanning line 31C changes from the low potential. By transitioning to a high potential, as shown in FIG. 13F, the second and third write transistors 24 and 25 become conductive. As a result, the voltage 2Vsig is sampled by the third write transistor 25 and held in the second storage capacitor 27.

  Next, at time t7, the potential WSC of the third scanning line 31C transitions from a high potential to a low potential, so that the third writing transistor 25 is turned off as illustrated in FIG. At the same time, the signal voltage Vsig of the video signal is supplied from the horizontal driving circuit 60 to the signal line 33 instead of the voltage 2Vsig which is twice the signal voltage Vsig of the video signal.

  Thereafter, at time t8 after the double voltage 2Vsig completely falls and converges to the signal voltage Vsig, the potential WSD of the fourth scanning line 31D transitions from a low potential to a high potential, so that FIG. As shown, the fourth write transistor 28 becomes conductive. As a result, the signal voltage Vsig is sampled by the fourth write transistor 28 and held in the third holding capacitor 29.

  Next, at time t9, the potential WSD of the fourth scanning line 31D changes from a high potential to a low potential, so that the fourth write transistor 28 is turned off as illustrated in FIG.

<Signal writing period & mobility correction period>
Next, at time t10, the potentials WSA and WSC of the first and third scanning lines 31A and 31C transition from a low potential to a high potential, and the potential WSB of the second scanning line 31B transitions from a high potential to a low potential. Thus, as shown in FIG. 14D, the first and third write transistors 23 and 25 are turned on, and the second write transistor 24 is turned off.

  As a result, the voltage 2Vsig once held in the second storage capacitor 27 is written to the first storage capacitor 26 through the third write transistor 25 and the first write transistor 23. By the writing of the voltage 2Vsig, the gate potential Vg of the drive transistor 22 starts to increase toward the voltage 2Vsig.

  Thereafter, at time t11, the potential WSC of the third scanning line 31C transitions from a high potential to a low potential, and then at time t12, the potential WSD of the fourth scanning line 31D transitions from a low potential to a high potential. As shown in FIG. 14E, the third write transistor 25 is turned off and the fourth write transistor 28 is turned off. As a result, the signal voltage Vsig once held in the third storage capacitor 29 is written to the first storage capacitor 26 through the fourth write transistor 28 and the first write transistor 23.

  At this time, since the gate potential Vg of the drive transistor 22 is increasing toward the voltage 2Vsig, the gate potential Vg of the drive transistor 22 instantaneously reaches the signal voltage Vsig by writing the signal voltage Vsig. Then, when the drive transistor 22 is driven by the signal voltage Vsig of the video signal, the threshold voltage Vth of the drive transistor 22 is canceled with a voltage corresponding to the threshold voltage Vth held in the first holding capacitor 26. Correction is performed.

  At this time, since the organic EL element 21 is initially in a cut-off state, the current (drain-source current Ids) flowing from the power supply line 32 to the drive transistor 22 in accordance with the signal voltage Vsig of the video signal is the organic EL element 21. Into the parasitic capacitance Cel. Therefore, charging of the parasitic capacitance Cel of the organic EL element 21 is started, and the source potential Vs of the driving transistor 22 rises with time.

  At this time, the variation in the threshold voltage Vth of the drive transistor 22 has already been corrected, and the drain-source current Ids of the drive transistor 22 depends on the mobility μ of the drive transistor 22. Eventually, when the source potential Vs of the drive transistor 22 rises to the potential of Vofs−Vth + ΔV, the gate-source voltage Vgs of the drive transistor 22 becomes Vsig−Vofs + Vth−ΔV, and mobility correction is performed.

<Light emission period>
Next, at time t <b> 13, the potential WSA of the first scanning line 31 </ b> A transitions from a high potential to a low potential, so that the first writing transistor 23 becomes nonconductive as illustrated in FIG. The gate electrode of the transistor 22 is disconnected from the node N11. At the same time, the drain-source current Ids starts to flow through the organic EL element 21, whereby the anode potential of the organic EL element 21 rises according to the drain-source current Ids.

  When the anode potential of the organic EL element 21, that is, the source potential Vs of the drive transistor 22 increases, the gate potential Vg of the drive transistor 22 also increases in conjunction with the bootstrap operation of the first storage capacitor 26.

  At this time, since the increase amount of the gate potential Vg becomes equal to the increase amount of the source potential Vs, the gate-source voltage Vgs of the driving transistor 22 is kept constant at Vsig + Vth−ΔV during the light emission period. At time t14, the potential WSD of the fourth scanning line 31D transitions from a high potential to a low potential, and at the same time, the potential of the signal line 33 is switched from the signal voltage Vsig to the offset voltage Vofs.

(Operational effect of the second embodiment)
As described above, according to the organic EL display device 10B according to the second embodiment, similarly to the organic EL display device 10A according to the first embodiment, the power supply potential (Vccp / Vini) supplied to the drive transistor 22 of the pixel circuit. ) Can be switched, and the drive transistor 22 has a function of controlling the light emission period / non-light emission period of the organic EL element 21 by switching the power supply potential. Since the influence on the timing is limited to the characteristic variation of one transistor of the drive transistor 22, the drive control of the organic EL element 21 that is less influenced by the characteristic variation of the transistors constituting the pixel circuit can be realized.

  In addition, in the present embodiment, a signal writing preparation period (t4-t10) is provided, and in the signal writing preparation period, a voltage (for example, 2Vsig) higher than the signal voltage Vsig of the video signal written first is held second. Once held in the capacitor 27, the signal voltage Vsig of the written video signal is once held in the third holding capacitor 29, and then a voltage higher than the signal voltage Vsig once held in the second holding capacitor 27 is applied to the node N12. Then, the signal voltage Vsig once held in the third holding capacitor 29 is written to the node N12. Accordingly, a voltage higher than the signal voltage Vsig of the video signal is written to the node N12, that is, the gate electrode of the driving transistor 22 prior to the writing of the signal voltage Vsig (so-called precharge).

  In this way, by setting the signal writing preparation period and writing a voltage higher than the signal voltage Vsig as a precharge voltage prior to writing the signal voltage Vsig of the video signal, the wiring resistance and parasitic capacitance of the signal line 33 are set. Is large, the gate potential Vg of the drive transistor 22 rises to the signal voltage Vsig earlier than when the signal voltage Vsig of the video signal is directly written. That is, the signal voltage Vsig of the video signal is instantaneously written without being affected by variations in the driving ability of the first and second write transistors 23 and 24 and the time constant between the write transistors 23 and 24 and the storage capacitor 25. Can be completed.

  Accordingly, since it is possible to reduce the time until the signal voltage Vsig of the video signal is completely written, the mobility correction can be started in the state where the writing of the signal voltage Vsig of the video signal is completed. As a result, even if the screen size becomes larger or the number of pixels increases with higher definition, and the fluctuation speed of the potential of the first signal line 33A becomes slower, the signal line potential becomes rounded. The variation in mobility correction between the pixels due to this can be eliminated and the unevenness can be suppressed, so that the image quality can be improved.

  In each of the above embodiments, the case where the voltage 2Vsig that is twice the signal voltage Vsig is set as the voltage higher than the signal voltage Vsig of the video signal, that is, the precharge voltage is described as an example. It is not limited to this, and any voltage corresponding to the signal voltage Vsig of the video signal may be used. Further, even if it is not a voltage corresponding to the signal voltage Vsig of the video signal, it is possible to set a voltage higher than the signal voltage Vsig of the video signal by a certain value.

  However, when the voltage corresponding to the signal voltage Vsig of the video signal is set as the precharge voltage rather than a voltage that is higher by a certain value, the driving is performed especially when the signal voltage Vsig of the video signal is large. Since the gate potential Vg of the transistor 22 can be raised more steeply toward the signal voltage Vsig, there is an advantage that the time until the signal voltage Vsig is completely written can be shortened.

  In each of the above-described embodiments, the case where the present invention is applied to an organic EL display device using an organic EL element as the electro-optical element of the pixel circuit 20 (20A, 20B) has been described as an example. The present invention is not limited to this example, and can be applied to all display devices using current-driven electro-optic elements (light-emitting elements) whose light emission luminance changes according to the value of current flowing through the device.

[Application example]
The display device according to the present invention described above is used in various electronic devices shown in FIGS. 15 to 19 as an example, for example, electronic devices such as digital cameras, notebook personal computers, mobile terminal devices such as mobile phones, and video cameras. The input video signal or the video signal generated in the electronic device can be applied to a display device of an electronic device in any field that displays an image or a video.

  As described above, by using the display device according to the present invention as a display device for electronic devices in all fields, the display device according to the present invention is provided between pixels as is apparent from the description of the first and second embodiments. Therefore, there is an advantage that high-quality image display can be performed in various electronic devices.

  Note that the display device according to the present invention includes a module-shaped one having a sealed configuration. For example, a display module formed by being affixed to an opposing portion such as transparent glass on the pixel array portion 30 is applicable. The transparent facing portion may be provided with a color filter, a protective film, and the like, and further, the above-described light shielding film. Note that the display module may be provided with a circuit unit for inputting / outputting a signal and the like from the outside to the pixel array unit, an FPC (flexible printed circuit), and the like.

  Specific examples of electronic devices to which the present invention is applied will be described below.

  FIG. 15 is a perspective view showing a television to which the present invention is applied. The television according to this application example includes a video display screen unit 101 including a front panel 102, a filter glass 103, and the like, and is created by using the display device according to the present invention as the video display screen unit 101.

  16A and 16B are perspective views showing a digital camera to which the present invention is applied. FIG. 16A is a perspective view seen from the front side, and FIG. 16B is a perspective view seen from the back side. The digital camera according to this application example includes a light emitting unit 111 for flash, a display unit 112, a menu switch 113, a shutter button 114, and the like, and is manufactured by using the display device according to the present invention as the display unit 112.

  FIG. 17 is a perspective view showing a notebook personal computer to which the present invention is applied. A notebook personal computer according to this application example includes a main body 121 including a keyboard 122 that is operated when characters and the like are input, a display unit 123 that displays an image, and the like, and the display device according to the present invention is used as the display unit 123. It is produced by this.

  FIG. 18 is a perspective view showing a video camera to which the present invention is applied. The video camera according to this application example includes a main body part 131, a lens 132 for photographing an object on the side facing forward, a start / stop switch 133 at the time of photographing, a display part 134, etc., and the display part 134 according to the present invention. It is manufactured by using a display device.

  FIG. 19 is a perspective view showing a mobile terminal device to which the present invention is applied, for example, a mobile phone, in which (A) is a front view in an open state, (B) is a side view thereof, and (C) is closed. (D) is a left side view, (E) is a right side view, (F) is a top view, and (G) is a bottom view. The mobile phone according to this application example includes an upper housing 141, a lower housing 142, a connecting portion (here, a hinge portion) 143, a display 144, a sub display 145, a picture light 146, a camera 147, and the like. Alternatively, the sub-display 145 is manufactured by using the display device according to the present invention.

1 is a system configuration diagram illustrating an outline of a configuration of an organic EL display device according to a first embodiment of the present invention. FIG. 3 is a circuit diagram illustrating a specific configuration example of a pixel according to the first embodiment. It is sectional drawing which shows an example of the cross-sectional structure of a pixel. It is a timing chart with which it uses for operation | movement description of the organic electroluminescence display which concerns on 1st Embodiment of this invention. It is explanatory drawing (the 1) of the circuit operation | movement of the organic electroluminescence display which concerns on 1st Embodiment of this invention. It is explanatory drawing (the 2) of the circuit operation | movement of the organic electroluminescence display which concerns on 1st Embodiment of this invention. It is a characteristic view with which it uses for description of the subject resulting from the dispersion | variation in the threshold voltage Vth of a drive transistor. It is a characteristic view with which it uses for description of the subject resulting from the dispersion | variation in the mobility (mu) of a drive transistor. FIG. 10 is a characteristic diagram for explaining the relationship between the signal voltage Vsig of the video signal and the drain-source current Ids of the drive transistor depending on whether threshold correction and mobility correction are performed. It is a system block diagram which shows the outline of a structure of the organic electroluminescence display which concerns on 2nd Embodiment of this invention. It is a circuit diagram which shows the specific structural example of the pixel which concerns on 2nd Embodiment. It is a timing chart with which it uses for operation | movement description of the organic electroluminescence display which concerns on 2nd Embodiment of this invention. It is explanatory drawing (the 1) of the circuit operation | movement of the organic electroluminescence display which concerns on 2nd Embodiment of this invention. It is explanatory drawing (the 2) of the circuit operation | movement of the organic electroluminescence display which concerns on 2nd Embodiment of this invention. It is a perspective view which shows the television to which this invention is applied. It is the perspective view which shows the digital camera to which this invention is applied, (A) is the perspective view seen from the front side, (B) is the perspective view seen from the back side. 1 is a perspective view showing a notebook personal computer to which the present invention is applied. It is a perspective view which shows the video camera to which this invention is applied. It is a perspective view showing a cellular phone to which the present invention is applied, (A) is a front view 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, (E) is a right side view, (F) is a top view, and (G) is a bottom view.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10A, 10B ... Organic EL display device, 20A, 20B ... Pixel (pixel circuit), 21 ... Organic EL element, 22 ... Drive transistor, 23 ... First write transistor, 24 ... Second write transistor, 25 ... Third write transistor , 26... First holding capacitor, 27... Second holding capacitor, 30... Pixel array section, 31 A (31 A- 1 to 31 A-m), 31 B (31 B- 1 to 31 B-m). 1-32-m) ... power supply line, 33A (33A-1 to 33A-n), 33B (33B-1 to 33B-n) ... signal line, 34 ... common power supply line, 40A ... first write scanning circuit , 40B ... second writing scanning circuit, 40C ... second writing scanning circuit, 50 ... power supply scanning circuit, 60 ... horizontal drive circuit, 70 ... display panel

Claims (10)

An electro-optical element; a driving transistor for driving the electro-optical element; a first writing transistor having one electrode connected to a gate electrode of the driving transistor; and the other electrode of the writing transistor and a signal line One electrode is connected to the connected second write transistor, the first storage capacitor connected between the gate electrode and the source electrode of the drive transistor, and the common connection node of the first and second write transistors A pixel array unit in which pixels including a third writing transistor and a second storage capacitor connected to the other electrode of the third writing transistor are arranged in a matrix;
First scanning means for scanning each pixel of the pixel array unit in units of rows and driving the first writing transistor to be conductive / non-conductive;
Supply means for supplying the signal line with the video signal in a non-conductive state of the first write transistor, and then supplying a voltage higher than the signal voltage of the video signal when the first write transistor is at least conductive;
Writing by the second writing transistor to scan each pixel of the pixel array unit in a row unit and write the video signal supplied from the supply unit to the signal line and a voltage higher than a signal voltage of the video signal Second scanning means for driving;
Each pixel of the pixel array unit is scanned in a row unit, the video signal written by the second writing transistor is written to the second storage capacitor, and the first writing is performed in a non-writing period by the second writing transistor. Third scanning means for performing write drive by the third write transistor so as to write the video signal held in the second hold capacitor during the conduction period of the transistor to the first hold capacitor through the first write transistor;
A fourth power supply line that is wired for each pixel row of the pixel array portion and that supplies a current to the drive transistor selectively supplies a first potential and a second potential lower than the first potential. A display device characterized by comprising scanning means. The display device according to claim 1, wherein the voltage higher than the signal voltage of the video signal is a voltage corresponding to the signal voltage. Each pixel of the pixel array section performs a mobility correction operation that cancels the dependence of the drive transistor on the mobility of the drain-source current during the writing period of the video signal by the first writing transistor. The display device according to claim 1. An electro-optical element; a driving transistor for driving the electro-optical element; a first writing transistor having one electrode connected to a gate electrode of the driving transistor; and the other electrode of the writing transistor and a signal line One electrode is connected to the connected second write transistor, the first storage capacitor connected between the gate electrode and the source electrode of the drive transistor, and the common connection node of the first and second write transistors A driving method of a display device having a pixel array portion in which pixels including a third writing transistor and a second storage capacitor connected to the other electrode of the third writing transistor are arranged in a matrix,
The first potential and the second potential lower than the first potential are selectively supplied to a power supply line that is wired for each pixel row of the pixel array portion and supplies a current to the driving transistor. Steps,
A second step of scanning each pixel of the pixel array unit in units of rows to drive conduction / non-conduction of the first write transistor;
A third step of supplying the signal line with the video signal during a non-conduction period of the first write transistor, and then supplying a voltage higher than the signal voltage of the video signal when the first write transistor is at least conductive; ,
The second write transistor scans each pixel of the pixel array unit row by row and writes the video signal supplied to the signal line in the third step and a voltage higher than the signal voltage of the video signal. A fourth step of performing write driving;
Each pixel of the pixel array unit is scanned in a row unit, the video signal written by the second writing transistor is written to the second storage capacitor, and the first writing is performed in a non-writing period by the second writing transistor. And a fifth step of performing write drive by the third write transistor so as to write the video signal held in the second hold capacitor during the conduction period of the transistor to the first hold capacitor through the first write transistor. A display device driving method. An electro-optical element; a driving transistor for driving the electro-optical element; a first writing transistor having one electrode connected to a gate electrode of the driving transistor; and the other electrode of the writing transistor and a signal line One electrode is connected to the connected second write transistor, the first storage capacitor connected between the gate electrode and the source electrode of the drive transistor, and the common connection node of the first and second write transistors A pixel array unit in which pixels including a third writing transistor and a second storage capacitor connected to the other electrode of the third writing transistor are arranged in a matrix;
First scanning means for scanning each pixel of the pixel array unit in units of rows and driving the first writing transistor to be conductive / non-conductive;
Supply means for supplying the signal line with the video signal in a non-conductive state of the first write transistor, and then supplying a voltage higher than the signal voltage of the video signal when the first write transistor is at least conductive;
Writing by the second writing transistor to scan each pixel of the pixel array unit in a row unit and write the video signal supplied from the supply unit to the signal line and a voltage higher than a signal voltage of the video signal Second scanning means for driving;
Each pixel of the pixel array unit is scanned in a row unit, the video signal written by the second writing transistor is written to the second storage capacitor, and the first writing is performed in a non-writing period by the second writing transistor. Third scanning means for performing write drive by the third write transistor so as to write the video signal held in the second hold capacitor during the conduction period of the transistor to the first hold capacitor through the first write transistor;
A fourth power supply line that is wired for each pixel row of the pixel array portion and that supplies a current to the drive transistor selectively supplies a first potential and a second potential lower than the first potential. An electronic apparatus comprising: a display device including a scanning unit. An electro-optical element; a driving transistor for driving the electro-optical element; a first writing transistor having one electrode connected to a gate electrode of the driving transistor; and the other electrode of the writing transistor and a signal line One electrode is connected to the connected second write transistor, the first storage capacitor connected between the gate electrode and the source electrode of the drive transistor, and the common connection node of the first and second write transistors A third write transistor; a second storage capacitor connected to the other electrode of the third write transistor; a fourth write transistor having one electrode connected to a common connection node of the first and second write transistors; , A pixel including a third storage capacitor connected to the other electrode of the fourth writing transistor is a matrix. A pixel array portion are arranged in a,
First scanning means for scanning each pixel of the pixel array unit in units of rows and driving the first writing transistor to be conductive / non-conductive;
Supplying a voltage higher than the signal voltage of the video signal when the first write transistor is in a non-conductive state, and then supplying the video signal to the signal line when the first write transistor is at least in a conductive state Means,
Writing by the second writing transistor to scan each pixel of the pixel array unit in units of rows and write a voltage higher than the signal voltage of the video signal supplied from the supply means to the signal line and the video signal Second scanning means for driving;
Each pixel of the pixel array unit is scanned in a row unit, and a voltage higher than the signal voltage of the video signal written by the second writing transistor is written to the second holding capacitor, and the non-writing by the second writing transistor is performed. In the writing period, the third writing is performed so that a voltage higher than the signal voltage of the video signal held in the second holding capacitor during the conduction period of the first writing transistor is written to the first holding capacitor through the first writing transistor. Third scanning means for performing writing drive by a transistor;
Each pixel of the pixel array unit is scanned in a row unit, the video signal written by the second write transistor is written to the third storage capacitor, and the first write is performed in a non-write period by the second write transistor. Fourth scanning means for performing write driving by the fourth write transistor so as to write the video signal held in the third hold capacitor during the conduction period of the transistor to the first hold capacitor through the first write transistor;
A fifth power source that is wired for each pixel row of the pixel array portion and selectively supplies a first potential and a second potential lower than the first potential to a power supply line that supplies a current to the driving transistor. A display device characterized by comprising scanning means. The display device according to claim 6, wherein the voltage higher than the signal voltage of the video signal is a voltage corresponding to the signal voltage. Each pixel of the pixel array section performs a mobility correction operation that cancels the dependence of the drive transistor on the mobility of the drain-source current during the writing period of the video signal by the first writing transistor. The display device according to claim 6. An electro-optical element; a driving transistor for driving the electro-optical element; a first writing transistor having one electrode connected to a gate electrode of the driving transistor; and the other electrode of the writing transistor and a signal line One electrode is connected to the connected second write transistor, the first storage capacitor connected between the gate electrode and the source electrode of the drive transistor, and the common connection node of the first and second write transistors A third write transistor; a second storage capacitor connected to the other electrode of the third write transistor; a fourth write transistor having one electrode connected to a common connection node of the first and second write transistors; , A pixel including a third storage capacitor connected to the other electrode of the fourth writing transistor is a matrix. A method of driving a display device having a pixel array portion are arranged in a,
The first potential and the second potential lower than the first potential are selectively supplied to a power supply line that is wired for each pixel row of the pixel array portion and supplies a current to the driving transistor. Steps,
A second step of scanning each pixel of the pixel array unit in units of rows to drive conduction / non-conduction of the first write transistor;
A third step of supplying a voltage higher than the signal voltage of the video signal during a non-conduction period of the first write transistor, and then supplying the video signal to the signal line when the first write transistor is at least conductive; ,
The second writing transistor scans each pixel of the pixel array unit row by row and writes a voltage higher than the signal voltage of the video signal supplied to the signal line in the third step and the video signal. A fourth step of performing write driving;
Each pixel of the pixel array unit is scanned in a row unit, and a voltage higher than the signal voltage of the video signal written by the second writing transistor is written to the second holding capacitor, and the non-writing by the second writing transistor is performed. In the writing period, the third writing is performed so that a voltage higher than the signal voltage of the video signal held in the second holding capacitor during the conduction period of the first writing transistor is written to the first holding capacitor through the first writing transistor. A fifth step of performing write driving by a transistor;
Each pixel of the pixel array unit is scanned in a row unit, the video signal written by the second write transistor is written to the third storage capacitor, and the first write is performed in a non-write period by the second write transistor. And a sixth step of performing write drive by the fourth write transistor so as to write the video signal held in the third hold capacitor during the transistor conduction period to the first hold capacitor through the first write transistor. A display device driving method. An electro-optical element; a driving transistor for driving the electro-optical element; a first writing transistor having one electrode connected to a gate electrode of the driving transistor; and the other electrode of the writing transistor and a signal line One electrode is connected to the connected second write transistor, the first storage capacitor connected between the gate electrode and the source electrode of the drive transistor, and the common connection node of the first and second write transistors A third write transistor; a second storage capacitor connected to the other electrode of the third write transistor; a fourth write transistor having one electrode connected to a common connection node of the first and second write transistors; , A pixel including a third storage capacitor connected to the other electrode of the fourth writing transistor is a matrix. A pixel array portion are arranged in a,
First scanning means for scanning each pixel of the pixel array unit in units of rows and driving the first writing transistor to be conductive / non-conductive;
Supplying a voltage higher than the signal voltage of the video signal when the first write transistor is in a non-conductive state, and then supplying the video signal to the signal line when the first write transistor is at least in a conductive state Means,
Writing by the second writing transistor to scan each pixel of the pixel array unit in units of rows and write a voltage higher than the signal voltage of the video signal supplied from the supply means to the signal line and the video signal Second scanning means for driving;
Each pixel of the pixel array unit is scanned in a row unit, and a voltage higher than the signal voltage of the video signal written by the second writing transistor is written to the second holding capacitor, and the non-writing by the second writing transistor is performed. In the writing period, the third writing is performed so that a voltage higher than the signal voltage of the video signal held in the second holding capacitor during the conduction period of the first writing transistor is written to the first holding capacitor through the first writing transistor. Third scanning means for performing writing drive by a transistor;
Each pixel of the pixel array unit is scanned in a row unit, the video signal written by the second write transistor is written to the third storage capacitor, and the first write is performed in a non-write period by the second write transistor. Fourth scanning means for performing write driving by the fourth write transistor so as to write the video signal held in the third hold capacitor during the conduction period of the transistor to the first hold capacitor through the first write transistor;
A fifth power source that is wired for each pixel row of the pixel array portion and selectively supplies a first potential and a second potential lower than the first potential to a power supply line that supplies a current to the driving transistor. An electronic apparatus comprising: a display device including a scanning unit.

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