JP4720070B2 - Electro-optical device, driving circuit and driving method thereof, and electronic apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electro-optical device including a light-emitting element whose light emission intensity is adjusted according to a supplied current, a driving circuit and a driving method thereof, and an electronic apparatus.
[0002]
[Prior art]
An organic light emitting diode element (hereinafter referred to as an OLED element) includes a light emitting material layer sandwiched between an anode layer and a cathode layer. This element operates electrically like a diode, and optically emits light at the time of forward bias, and the light emission intensity increases as the forward bias current increases.
[0003]
An active matrix type display is known as a display using an OLED element. FIG. 17 shows a main part of a conventional display. In this display, pixels are arranged in a matrix corresponding to a plurality of scanning lines, a plurality of data lines, and intersections of the scanning lines and the data lines. Each pixel includes an OLED element and is selected by a scanning signal supplied from the scanning line driving circuit via the scanning line. When the data line driving circuit supplies a setting current to each data line during the selection period, the setting current flows between the data line and the selected pixel. The pixel has a storage circuit that stores a set current, and the set current flows through the OLED element during the non-selection period. The storage circuit has a storage capacitor, and the set current is stored by the charging voltage of the storage capacitor. Such a driving method is disclosed in Patent Document 1.
[0004]
[Patent Document 1]
Japanese Patent Laid-Open No. 2003-22049
[0005]
[Problems to be solved by the invention]
As described above, the emission intensity of the OLED element is determined by the forward bias current. For example, when displaying 64 gradations, the value of the setting current corresponding to the lowest gradation is on the order of nA to μA. Further, in order to pass a target set current between the data line and the pixel, it is necessary to set the potential of the data line to a target potential corresponding to the target set current. On the other hand, the data line has a stray capacitance corresponding to the area and a resistance component corresponding to the line width, and thus has a predetermined time constant.
[0006]
Therefore, when the gradation to be displayed is low and the set current is extremely small, it takes a long time to charge and discharge the data line stray capacitance and to bring the data line potential to the target potential according to the set current. Cost. For this reason, there is a problem that the potential of the data line does not change to the target potential during the selection period and the set current cannot be stored in the pixel accurately.
[0007]
The present invention has been made in view of the above-described circumstances, and an electro-optical device capable of accurately storing a set current even when a gradation to be displayed on a pixel is low gradation, and a driving circuit thereof It is another object of the present invention to provide a driving method and an electronic device.
[0008]
[Means for Solving the Problems]
In order to solve the above problem, a drive circuit of an electro-optical device according to the present invention includes a plurality of data lines, a plurality of scanning lines, and a plurality of scanning lines provided corresponding to the intersections of the data lines and the scanning lines. A light-emitting element whose emission intensity is adjusted in accordance with a supplied current, and a set current that flows between the data line and the pixel during a selection period of the pixel. A drive circuit for an electro-optical device having a storage means for storing a current to be fed to the first, a first means for supplying a first current from one end of the data line, and a second current from the other end of the data line. And a second means for supplying The first means is a constant current source that supplies the first current as a constant current, and the second means is configured such that the set current obtained by combining the constant current and the second current is supplied to the pixel. The amount of the second current is adjusted based on the image data so that the current corresponds to the gradation to be displayed. It is characterized by that.
[0009]
According to the present invention, the set current is given by combining the first current and the second current on the data line. Here, “synthesis” means that the first current and the second current are combined, and the addition of the first current and the second current, the subtraction of the second current from the first current, and the second current from the second current. One current subtraction is included. Since the first current and the second current flow through the data line, a large current can flow through the data line even if the set current is a small value. Although the data line has an equivalently large stray capacitance, the potential of the data line can be charged in a short time by supplying a large current thereto. This makes it possible to pass a set current between the pixel and the data line so that a desired gradation can be accurately obtained during the selection period. As a result, the reproducibility of gradation is greatly improved, and the display quality can be improved. As the light emitting element, for example, an organic light emitting diode element is applicable, but the present invention is not limited to this, and any element can be used as long as the light emission intensity is adjusted by a supplied current. Also good.
[0010]
Further, the first means is a constant current source that supplies the first current as a constant current, and the second means is configured such that the set current obtained by combining the constant current and the second current is the It is preferable to adjust the amount of the second current based on the image data so that the current corresponds to the gradation to be displayed on the pixel. In this case, since the first current is fixed and only the second current needs to be changed according to the image data, the configuration of the drive circuit can be simplified.
[0011]
Further, it is preferable that the second means executes one of discharge or suction and supplies the second current to the data line from the viewpoint of simplifying the configuration.
[0012]
The second means may execute by selecting whether to discharge or suck the second current into the data line according to the gradation to be displayed on the pixel. In this case, the direction of the second current is selected according to the gradation to be displayed on the pixel. Thereby, current consumption can be reduced.
[0013]
More specifically, the first current is set to have a current amount corresponding to an intermediate gradation displayed on the pixel, and the second means is configured to apply the second current to the data line. It is preferable that a selection means for selecting whether to discharge or suck out the image data and to control the selection means based on the most significant bit of the image data. Note that the intermediate gradation only needs to be between the maximum luminance and the minimum luminance of the light emitting element, and does not necessarily mean 50% of the maximum luminance.
[0014]
Further, the first means and the second means may be configured to use the first current and the second current based on image data so that the set current is a current corresponding to a gradation to be displayed on the pixel. The amount may be adjusted. In this case, the two currents flowing through the data lines are adjusted according to the gradation to be displayed. Here, the first means and the second means may adjust the current amounts of the first current and the second current based on image data so that the set current becomes a gamma-corrected current. preferable. In this case, since the gamma correction function executed in the external circuit can be taken into the drive circuit, the entire apparatus can be reduced in size.
[0015]
In the above-described driving circuit, the data line is formed by folding back in a pixel region where the pixels are arranged in a matrix, and the first means and the second means are opposite to the turning point of the data line. It is preferable to arrange on the side. In this case, since the first means and the second means can be arranged close to each other, the characteristics of elements such as a thin film transistor used for constituting these means can be made uniform. As a result, it is possible to display a high-quality image by reducing an error in the set current.
[0016]
[Means for Solving the Problems]
Next, an electro-optical device according to the present invention includes a drive circuit, a plurality of data lines, a plurality of scanning lines, and a plurality of pixels provided corresponding to intersections of the data lines and the scanning lines. When The And the pixel supplies a light emitting element whose emission intensity is adjusted in accordance with a supplied current and a set current flowing between the data line and the pixel during a selection period of the pixel. Storage means for storing the current as current. According to this electro-optical device, the set current can be written into the pixel in a short time, and therefore the scanning line selection period can be shortened. As a result, it is possible to increase the number of pixels and display a high-definition image.
[0017]
Next, an electronic apparatus according to the present invention includes the above-described electro-optical device. For example, a mobile phone, a PDA, a personal computer, a television, a viewfinder type, a monitor direct-view type video tape recorder, and a car navigation device. , Pagers, electronic notebooks, calculators, POS terminals, devices with touch panels, and the like.
[0018]
Next, the electro-optical device driving method according to the present invention includes a plurality of data lines, a plurality of scanning lines, and a plurality of pixels provided corresponding to intersections of the data lines and the scanning lines. The pixel includes a light emitting element whose emission intensity is adjusted according to a current supplied, and a current that supplies a set current flowing between the data line and the pixel during a selection period of the pixel to the light emitting element. An electro-optical device driving method comprising a storage means for storing, from one end of the data line Constant current Supplying a first current and supplying a second current from the other end of the data line; Based on the image data, the current amount of the second current is set so that the set current obtained as the difference between the first current and the second current becomes a current corresponding to the gradation to be displayed on the pixel. And an adjusting step for adjusting.
[0019]
According to the present invention, since the combined current of the first current and the second current on the data line becomes the set current, a large current can flow through the data line even if the set current is a small value. Can be charged in a short time. This allows a set current to flow between the pixel and the data line so that the desired gradation can be accurately obtained during the selection period, greatly improving the reproducibility of the gradation and improving the display quality. can do.
[0020]
In the driving method described above, the first current is a constant current, and in the adjustment step, the set current obtained as a difference between the constant current and the second current is a gradation to be displayed on the pixel. It is preferable that the current amount of the second current is adjusted based on the image data so as to obtain a current corresponding to the current. Further, the first current is set to have a current amount corresponding to an intermediate gradation displayed on the pixel, and in the adjustment step, the direction of the second current is the most significant bit of the image data. It is preferable to select according to. According to this driving method, current consumption can be reduced.
[0021]
In the adjustment step, the current amounts of the first current and the second current are adjusted based on image data so that the set current becomes a current corresponding to a gradation to be displayed on the pixel. Also good.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
<1. First Embodiment>
First, as an example of an electro-optical device using an electro-optical panel according to the present invention, a device using an OLED element as an electro-optical material will be described. FIG. 1 is a block diagram showing an electrical configuration of the electro-optical device according to the first embodiment of the present invention. The electro-optical device includes an electro-optical panel AA, a control circuit 500, and a power supply circuit 400 as main parts.
[0023]
The electro-optical panel AA includes an element substrate and a counter substrate. An image display region A, a scanning line driving circuit 100, a data line driving circuit 200, and a current source circuit 300 are formed on the element substrate. These circuits are simultaneously formed in the same process as the transistors in the image display area A. This transistor is constituted by a thin film transistor (hereinafter referred to as “TFT”).
[0024]
In the image display area A, as shown in FIG. 1, two sets of a plurality of sets of scanning lines 2 a and 2 b are formed and arranged in parallel along the X direction. On the other hand, a plurality of data lines 3 are formed in parallel along the Y direction. Further, a current supply line 4 for supplying a current to each pixel P is formed. In the vicinity of the intersection of the scanning lines 2a and 2b and the data line 3, the pixels P are arranged in a matrix. Although details of the pixel P will be described later, the pixel P includes an OLED element. In this example, it is assumed that m rows and n columns of pixels P are arranged.
[0025]
The control circuit 500 generates various timing signals and image data D and supplies them to the electro-optical panel AA. The X scanning start pulse SPX is a pulse for instructing the start of horizontal scanning, and is a pulse of one horizontal scanning cycle that becomes active at a high level. The X clock signal CKX is a signal synchronized with the image data D.
[0026]
The Y scanning start pulse SPY is a pulse that instructs the start of vertical scanning and is active at a high level. The Y clock signal CKY is a signal synchronized with the horizontal scanning cycle. The write control signal GWRT is a signal that becomes active when writing of a data signal to the pixel P is permitted.
[0027]
The power supply circuit 400 includes a constant voltage source (not shown) that generates various potentials, and supplies a predetermined potential to each component.
[0028]
The scanning line driving circuit 100 includes a shift register (not shown), and sequentially shifts the Y scanning start pulse SPY based on the Y clock signal CKY during the period in which the write control signal GWRT is active, thereby scanning signals GWRT1 to GWRTm and inversion. Scan signals GEL1 to GELm are generated. The inverted scanning signals GEL1 to GELm are obtained by inverting the scanning signals GWRT1 to GWRTm.
[0029]
The data line driving circuit 200 includes an address circuit 210 configured by a shift register or the like, a first latch circuit group 220, a second latch circuit group 230, and a current D / A conversion circuit 240A. The shift register of the address circuit 210 sequentially shifts the X scanning start pulse SPX in synchronization with the X clock signal CKX, generates a sampling pulse for sampling the image data D, and supplies this to the first data latch circuit group 220. . The first data latch circuit group 220 latches the image data D based on the sampling pulse and generates dot sequential image data. The second data latch circuit group 230 latches the dot sequential data according to the latch pulse LP and generates line sequential image data Ds. When the image data D is 4 bits, the line sequential image data Ds is similarly 4 bits. The current D / A conversion circuit 240A includes a number of current D / A converters 24-1 to 24-n corresponding to the number of data lines 3 (in this example, n), and the gradation indicated by the image data D Is supplied to the data line 3 in accordance with the second current i2.
[0030]
The constant current source circuit 300 includes a number of constant current sources 30-1 to 30-n corresponding to the number of data lines 3 (in this example, n). Each of the constant current sources 30-1 to 30-n is configured by N-channel TFTs having the same transistor size (W / L), and the first reference potential VREF1 is supplied to the gates thereof. The amount of the first current i1 supplied to one end of the data line 3 is adjusted by the first reference potential VREF1. The first current i1 in this example flows from the data line 3 toward the current source circuit 300 (suction), but by using a P-channel TFT instead of the N-channel TFT, the first current i1 is directed from the current source circuit 300 toward the data line 3. It may be washed away (vomiting). In this example, the first reference potential VREF1 is supplied from the power supply circuit 400 so that the value of the first current i1 can be adjusted from the outside of the electro-optical panel AA. The first reference potential VREF1 may be generated from a high potential power source.
[0031]
FIG. 2 shows a detailed circuit diagram of the current D / A converter 24-1. The other current D / A converters 24-2 to 24-n are configured similarly to the current D / A converter 24-1. The current D / A converter 24-1 includes four P-channel TFTs 241 to 244 having the same gate length L. When the gate width W of the P-channel TFT 241 is “x”, the gate width W of the P-channel TFT 242 is “2x”, the gate width W of the P-channel TFT 243 is “4x”, and the gate width W of the P-channel TFT 244 is “16x”. Is set to
[0032]
Switches SWa and SWb are connected to the gates of the P-channel TFTs 241 to 244. The switch SWa is turned on when the control signal is at a high level, and is turned off when the control signal is at a low level. Conversely, the switch SWb is turned off when the control signal is at a high level, and turned on when the control signal is at a low level. The switch SWa can be composed of an N-channel TFT, and the switch SWb can be composed of a P-channel TFT.
[0033]
When each switch SWb is turned on, the high potential VDD is supplied to the gates of the P-channel TFTs 241 to 244, and the P-channel TFTs 241 to 244 are turned off. On the other hand, when each switch SWa is in the ON state, the second reference potential VREF2 is supplied to the gates of the P-channel TFTs 241 to 244, and a current corresponding to the second reference potential VREF2 flows between the source and drain of the P-channel TFTs 241 to 244. Flowing. Therefore, the second current i2 can be adjusted by changing the value of the second reference potential VREF2. In this example, the high potential VDD and the second reference potential VREF2 are supplied from the power supply circuit 400, but the second reference potential VREF2 may be generated from the high potential VDD inside the current D / A conversion circuit 240A.
[0034]
The bit data Ds0 to Ds3 of the line sequential image data Ds are supplied to the current D / A converter 24-1 as control signals. The gate width W of the P-channel TFTs 241 to 244 is 2 ⁰ : 2 ¹ : 2 ² : 2 ³ Therefore, the current that flows when each of the P-channel TFTs 241 to 244 is on is also 2 ⁰ : 2 ¹ : 2 ² : 2 ³ Is weighted. As a result, the second current i2 corresponding to the image data Ds is supplied to the other end of the data line 3.
[0035]
FIG. 3 is a timing chart for explaining operations of the scanning line driving circuit 100 and the data line driving circuit 200. When the Y scanning start pulse SPY is supplied to the scanning line driving circuit 100, the scanning line driving circuit 100 sequentially outputs the scanning signals GWRT1, GWRT2, GWRT3,. To do. The inverted scanning signals GEL1, GEL2, GEL3,..., GELm are obtained by inverting the scanning signals GWRT1, GWRT2, GWRT3,. Here, in the image display area A, focusing on each pixel P in the first row from the top, in one frame period 1F, the selection period of these pixels P is T1, and the non-selection period is T2.
[0036]
In the selection period T1, the image data Ds to be supplied to each pixel P in the first row is output to the current D / A conversion circuit 240A. In the figure, Ds (1), Ds (2),... Ds (m) are codes indicating data corresponding to the pixels P in the first row to the m-th row, respectively. As will be described later, in the selection period T1, writing of the set current ipxl is performed on each pixel P in the first row, while in the non-selection period T2, a level corresponding to the set current ipxl written in the selection period T1 is executed. Key is displayed.
[0037]
FIG. 4 is a circuit diagram showing a configuration of one pixel. The pixel P in this example is arranged in the first row and first column shown in FIG. 1 and is supplied with the scanning signal GWRT1 and the inverted scanning signal GEL1, but the same applies to the other pixels P. The pixel P includes a switching transistor SwTr, a program transistor PrgTr, a driving transistor DrvTr, an EL transistor ElTr, a storage capacitor C, and an organic light emitting diode OLED. The cathode of the organic light emitting diode OLED is connected to the transparent electrode of the counter substrate, and a common potential VCOM is applied thereto. The driving transistor DrvTr is composed of a P-channel TFT, and the other transistors are composed of N-channel TFTs. In this example, the potential VEL supplied through the current supply line 4 is higher than the common potential VCOM. The driving transistor DrvTr may be composed of an N-channel TFT, the other transistor may be composed of a P-channel TFT, and the polarity of the organic light emitting diode OLED may be reversed. In this case, the potential VEL is set lower than the common potential VCOM.
[0038]
The switching transistor SwTr functions as a switching unit that switches a connection state between the data line 3 and the pixel P. The switching transistor SwTr is turned on when the scanning signal GWRT1 supplied via the scanning line 2a is active (high level) and connects the data line 3 and the pixel P, while the scanning signal GWRT1 is inactive (low level). At this time, the data line 3 and the pixel P are separated from each other.
[0039]
The program transistor PrgTr is turned on in the selection period of the pixel P in which the scanning signal GWRT1 is active, and is turned off in the non-selection period of the pixel P in which the scanning signal GWRT1 is inactive. When the program transistor PrgTr and the switching transistor SwTr are turned on, a setting current ipxl flows through the driving transistor DrvTr as shown in FIG. At this time, the storage capacitor C is charged so that the set current ipxl can flow, and the source potential corresponding to the amount of the set current ipxl is supplied to the source of the driving transistor DrvTr. When the scanning signal GWRT1 becomes inactive, the program transistor PrgTr is turned off.
[0040]
Since the gate of the driving transistor DrvTr has high impedance, the charge charged in the storage capacitor C is held and the gate potential is kept constant. That is, in the selection period, the storage capacitor C is programmed with a potential according to the set current ipxl. Therefore, the program transistor PrgTr, the driving transistor DrvTr, and the storage capacitor C function as a storage unit that stores the current amount of the set current ipxl.
[0041]
On the other hand, in the non-selection period, the program transistor PrgTr and the switching transistor SwTr are turned off, and the inverted scanning signal GEL becomes active (high level). Then, the EL transistor ElTr is turned on, and the set current ipxl programmed in the selection period flows through the organic light emitting diode OLED as shown in FIG. This makes it possible to display a predetermined gradation on the pixel P.
[0042]
In the selection period, the set current ipxl is given as a difference between the first current i1 from the current source circuit 300 and the second current i2 from the current D / A conversion circuit 240A, and ipxl = i1-i2. FIG. 6 is a graph showing the relationship between the gradation to be displayed on the pixel P and the set current ipxl given as the write current to the pixel P. In this example, the current amount of the second current i2 corresponding to 75% gradation is i2a, the current amount of the second current i2 corresponding to 50% gradation is i2b, and the current of the second current i2 corresponding to 25% gradation. The amount is represented by i2c, and the set current ipxl corresponding to 0% gradation is represented by imax.
[0043]
As can be seen from this graph, when the gradation to be displayed on the pixel P is in the vicinity of “black”, the first current flowing through the data line 3 is i1 = imax. That is, since the set current ipxl is given as a difference between the first current i1 and the second current i2, a large current can be passed through the data line 3 even if the set current ipxl is a small value. Although the data line 3 has an equivalently large stray capacitance, the potential of the data line 3 can be charged in a short time by supplying a large current thereto. Thus, the set current ipxl can be passed between the pixel P and the data line 3 so that a desired gradation can be accurately obtained during the selection period. In particular, in the high-definition electro-optical panel AA having a large number of pixels, the time for the selection period is shortened. Therefore, it is necessary to write the set current ipxl to the pixel P in a short time. In such a case, the driving method of the present embodiment is extremely effective.
[0044]
In the present embodiment, since the first current i1 is fixed, only the second current i2 needs to be changed according to the image data D. For this reason, the data line driving circuit 200 may be provided on one of the data lines 3, so that the configuration can be simplified and the transfer amount of the image data D does not increase.
[0045]
<2. Second Embodiment>
Next, an electro-optical device according to a second embodiment will be described. The electro-optical device according to the second embodiment uses a current D / A conversion circuit 240B that supplies the second current i2 bidirectionally instead of the current D / A conversion circuit 240A that supplies the second current i2 only in one direction. Except for this point, the configuration is the same as that of the electro-optical device according to the first embodiment shown in FIG.
[0046]
FIG. 8 is a block diagram of the electro-optical device according to the second embodiment. The current D / A conversion circuit 240B includes n current D / A converters 25-1 to 25-n. In addition, switches SW1 and SW2 are provided for each of the current D / A converters 25-1 to 25-n. The on / off of the switches SW1 and SW2 is controlled by the MSB of the image data Ds. In this example, when the MSB of the image data Ds is “1” (high level), the switch SW1 is turned on and the switch SW2 is turned off. In this case, the terminal Q on the side opposite to the data line 3 of the current D / A converter 25 is connected to the high potential power supply VDD, and the second current i2 flows out from the current D / A conversion circuit 240B toward the data line 3. (Vomit).
[0047]
On the other hand, when the MSB of the image data Ds is “0” (low level), the switch SW1 is turned off and the switch SW2 is turned on. In this case, the terminal Q is grounded, and the second current i2 flows from the data line 3 toward the current D / A conversion circuit 240B. As a result, the direction of the second current i2 can be switched. That is, the current D / A conversion circuit 240B selects and executes whether to discharge or suck the second current i2 to the data line 3 in accordance with the gradation to be displayed on the pixel P.
[0048]
FIG. 9 is a graph showing the relationship between the gradation to be displayed on the pixel P and the set current ipxl given as the write current to the pixel P in the second embodiment. In this example, when the setting current ipxl corresponding to 50% gradation is imid, the first current is set so that i1 = imid. Then, the direction of the second current i2 is switched depending on whether the gradation to be displayed on the pixel P is larger or smaller than 50% (intermediate gradation). This is because the weighting of the most significant bit MSB of the image data Ds corresponds to 1/2 of the maximum gradation. When the gradation to be displayed on the pixel P is larger than 50%, the second current i2 is sucked into the data line 3, while when the gradation to be displayed on the pixel P is smaller than 50%. The second current i2 is discharged to the data line 3.
[0049]
By switching the direction of the second current i2 according to the gradation to be displayed in this way, the current amount of the first current i1 can be reduced. In particular, when i1 = imid is set, the current amount of the first current i1 can be halved compared to the case of the first embodiment (see FIG. 6).
[0050]
<3. Third Embodiment>
Next, an electro-optical device according to a third embodiment will be described. The electro-optical device according to the third embodiment is configured similarly to the electro-optical device according to the first embodiment shown in FIG. 1 except for the arrangement of the current source circuit 300 and the routing of the data line 3.
[0051]
FIG. 10 is a block diagram of an electro-optical device according to the third embodiment. As shown in this figure, the current source circuit 300 is provided on the same side as the current D / A conversion circuit 240A with respect to the data line 3. For this reason, the data line 3 is folded and wired inside the image display area A, and one end thereof is connected to the current D / A conversion circuit 240A, and the other end is connected to the current source circuit 300.
[0052]
In this way, by folding the data line 3 and arranging the current D / A conversion circuit 240A and the constant current source circuit 300 close to each other, variations in IV characteristics of the transistors constituting these circuits are reduced. be able to. The variation in the IV characteristic causes an error in the set current ipxl, which causes the gradation reproducibility to deteriorate. According to the present embodiment, since the components that generate the first current i1 and the second current i2 are arranged close to each other, it is possible to improve gradation reproducibility. In this example, the current D / A conversion circuit 240A that supplies the second current i2 in one direction is used, but the current D / A conversion circuit 240B that supplies the second current i2 in both directions may be used.
[0053]
<4. Fourth Embodiment>
Next, an electro-optical device according to a fourth embodiment will be described. The electro-optical device according to the fourth embodiment is configured in the same manner as the electro-optical device according to the first embodiment shown in FIG. 1 except that a data line driving circuit is used instead of the current source circuit 300.
[0054]
FIG. 11 is a block diagram of an electro-optical device according to the third embodiment. In this example, in order to distinguish the circuits provided above and below the data line 3, the upper one is referred to as a second data line driving circuit 200, and the lower one is provided as the first data line driving circuit 200. I'll call it '.
[0055]
The first data line driving circuit 200 ′ uses a current D / A conversion circuit 240C that sucks the first current i1 from the data line 3 instead of the current D / A conversion circuit 240A that discharges the second current i2 to the data line 3. Except for this point, the second data line driving circuit 200 is configured in the same manner. The current D / A conversion circuit 240C includes n current D / A converters. This current D / A converter can be configured, for example, by using N-channel TFTs instead of P-channel TFTs 241 to 244 in the current D / A converter 24-1 shown in FIG.
[0056]
FIG. 12 is a graph showing an example of the relationship between the gradation to be displayed on the pixel P and the set current ipxl given as the write current to the pixel P in the third embodiment. In this example, when the slope of the first current i1 is K, the slope of the second current i2 is −K. The intercepts of the first current i1 and the second current i2 are set to a set current ipxl corresponding to 50% gradation.
[0057]
For example, when the gradation to be displayed on the pixel P is 75%, the current amount of the first current i1 is i1a, and the current amount of the second current i2 is i2a. Since the setting current ipxl is given by ipxl = i1-i2, if the setting current ipxl corresponding to 75% gradation is ipxl (75), ipxl (75) = i1a-i2a.
[0058]
In this example, the first current i1 and the second current i2 are both linear, but gamma correction may be performed with at least one characteristic being nonlinear. For example, the first current i1 may have a linear characteristic and the second current i2 may have a non-linear characteristic. FIG. 13 is a graph showing an example of the relationship between the gradation to be displayed on the pixel P and the set current ipxl when the gamma correction function is added. In this example, the first current i1 has a linear characteristic, and the second current i2 is adjusted to add a gamma correction function. In this case, the D / A current conversion circuit 240 </ b> A needs to drive the second current i <b> 2 bidirectionally with respect to the data line 3. For this reason, the D / A current conversion circuit 240B described in the second embodiment is used.
[0059]
However, the current D / A conversion circuit 240C can be used by setting a large value of the Y intercept of the first current i1. FIG. 14 shows characteristics when the second current i2 is supplied to the data line 3 only in one direction. In this example, when the display gradation is white, the first current i1 and the set current ipxl are set to be equal. Accordingly, since the second current i2 can be set to “0” when the display gradation is white, the second data line driving circuit 200 supplies the second current i2 to the data line 3 only in one direction. That's fine.
[0060]
<5. Application example>
(1) In each of the embodiments described above, the drive circuits such as the scanning line drive 100, the first and second data line drive circuits 200 ′ and 200, and the current source circuit 300 are configured in the electro-optical panel AA. A part or all of them may be integrated into an IC chip, and the driving IC may be mounted on a flexible substrate using TAB (Tape Automated Bonding) technology. Further, the driving IC itself may be electrically and mechanically connected to a predetermined position of the element substrate through an anisotropic conductive film using COG (Chip On Grass) technology. Also, peripheral circuits such as the control circuit 500 may be formed on the element substrate and taken into the electro-optical panel. Of course, this is only one example of a panel configuration that can be realized using the present invention.
[0061]
(2) Next, the case where the above-described electro-optical device is applied to various electronic devices will be described. First, an example in which the electro-optical panel AA is applied to a mobile personal computer will be described. FIG. 15 is a perspective view showing the configuration of this personal computer. In the figure, a computer 1200 includes a main body 1204 having a keyboard 1202 and an electro-optical display unit 1206.
[0062]
Further, an example in which the electro-optical panel AA is applied to a mobile phone will be described. FIG. 16 is a perspective view showing the configuration of this mobile phone. In the figure, a mobile phone 1300 includes a plurality of operation buttons 1302 and an electro-optical panel AA.
[0063]
In addition to the electronic devices described with reference to FIGS. 15 and 16, a TV, a viewfinder type, a monitor direct-view type video tape recorder, a car navigation device, a pager, an electronic notebook, a calculator, a word processor, a workstation , A video phone, a POS terminal, a device equipped with a touch panel, and the like. Needless to say, the present invention can be applied to these various electronic devices.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating an overall configuration of an electro-optical device according to a first embodiment of the invention.
FIG. 2 is a circuit diagram of a current D / A converter used in the apparatus.
FIG. 3 is a timing chart for explaining operations of a scanning line driving circuit 100 and a data line driving circuit 200 used in the apparatus.
FIG. 4 is a circuit diagram of a pixel P constituting the electro-optical panel AA of the apparatus.
FIG. 5 is an explanatory diagram showing a current path in a selection period.
FIG. 6 is an explanatory diagram showing a current path in a non-selection period.
FIG. 7 is a graph showing a relationship between a gradation to be displayed on a pixel P and a set current ipxl in the first embodiment.
FIG. 8 is a block diagram illustrating an overall configuration of an electro-optical device according to a second embodiment of the invention.
FIG. 9 is a graph showing the relationship between the gradation to be displayed on the pixel P and the set current ipxl in the same embodiment.
FIG. 10 is a block diagram illustrating an overall configuration of an electro-optical device according to a third embodiment of the invention.
FIG. 11 is a block diagram illustrating an overall configuration of an electro-optical device according to a fourth embodiment of the invention.
FIG. 12 is a graph showing an example of the relationship between the gradation to be displayed on the pixel P and the set current ipxl in the embodiment.
FIG. 13 is a graph showing an example of a relationship between a gradation to be displayed on a pixel P to which a gamma correction function is added and a set current ipxl.
FIG. 14 is a graph showing another example of the relationship between the gradation to be displayed on the pixel P to which the gamma correction function is added and the set current ipxl.
FIG. 15 is a perspective view illustrating a configuration of a personal computer as an example of an electronic apparatus to which the electro-optical device is applied.
FIG. 16 is a perspective view illustrating a configuration of a mobile phone as an example of an electronic apparatus to which the electro-optical device is applied.
FIG. 17 is a block diagram illustrating a configuration of a conventional electro-optical device.
[Explanation of symbols]
2a, 2b ... scanning line, 3 ... data line, P ... pixel, organic light emitting diode ... OLED, 100 ... scanning line driving circuit, 200 ... data line driving circuit, 300 ... current source circuit, 400 ... power supply circuit, 500 ... Control circuit, i1 ... first current, i2 ... second current, ipxl ... setting current, AA ... electro-optical panel,

Claims (9)

A plurality of data lines, a plurality of scanning lines, and a plurality of pixels provided corresponding to intersections of the data lines and the scanning lines are provided, and the light emission intensity of each of the pixels is adjusted according to a supplied current. A drive circuit for an electro-optical device, comprising: a light emitting element to be stored; and a storage unit that stores a set current flowing between the data line and the pixel during a selection period of the pixel as a current for supplying power to the light emitting element There,
First means for supplying a first current from one end of the data line;
Second means for supplying a second current from the other end of the data line;
The first means is a constant current source that supplies the first current as a constant current.
The second means is configured to adjust the second current based on image data so that the set current obtained by combining the constant current and the second current becomes a current corresponding to a gradation to be displayed on the pixel. A drive circuit for an electro-optical device, characterized by adjusting an amount of current.   2. The drive circuit of the electro-optical device according to claim 1, wherein the second unit supplies one of the discharge and the suction to supply the second current to the data line.   2. The method according to claim 1, wherein the second means selects and executes whether the second current is discharged or sucked into the data line according to a gradation to be displayed on the pixel. A driving circuit of the electro-optical device according to claim. The first current is set to be a current amount corresponding to an intermediate gradation displayed on the pixel,
The second means includes selection means for selecting whether to discharge or suck the second current to the data line, and controls the selection means based on the most significant bit of the image data. The drive circuit for the electro-optical device according to claim 3. The data line is formed by folding back in a pixel region where the pixels are arranged in a matrix,
It said first means and said second means, the driving circuit of the electro-optical device according to any one of claims 1 to 4 and the turning point of the data line, characterized in that it is arranged on the opposite side . A drive circuit for an electro-optical device according to any one of claims 1 to 5 ,
Multiple data lines,
A plurality of scan lines;
A plurality of pixels provided corresponding to the intersection of the data line and the scanning line,
The pixel includes a light emitting element whose emission intensity is adjusted according to a current supplied, and a current that supplies a set current flowing between the data line and the pixel during a selection period of the pixel to the light emitting element. An electro-optical device comprising: storage means for storing. An electronic apparatus comprising the electro-optical device according to claim 6 . A plurality of data lines, a plurality of scanning lines, and a plurality of pixels provided corresponding to intersections of the data lines and the scanning lines are provided, and the light emission intensity of each of the pixels is adjusted according to a supplied current. And a storage unit that stores a set current flowing between the data line and the pixel during a selection period of the pixel as a current for supplying power to the light emitting element. There,
Supplying a first current that is a constant current from one end of the data line, and supplying a second current from the other end of the data line;
Based on the image data, the current amount of the second current is set so that the set current obtained as the difference between the first current and the second current becomes a current corresponding to the gradation to be displayed on the pixel. Adjustment steps to adjust;
A method for driving an electro-optical device. The first current is set to be a current amount corresponding to an intermediate gradation displayed on the pixel,
The method of driving an electro-optical device according to claim 8 , wherein, in the adjustment step, the direction of the second current is selected according to the most significant bit of the image data.

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