JP2008112191A - Electronic device driving method, electronic device, semiconductor integrated circuit, and electronic apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electronic device driving method and an electronic device which realize accurate gradation control in a minute current region and reduction of current consumption of a display.
A plurality of scanning lines; a plurality of signal lines; and a current driving element disposed corresponding to each intersection of the scanning lines and the signal lines. An electronic device that operates according to an amount of drive current supplied to an element, or a drive method thereof, wherein the drive current amount is a value of the drive current and the drive that is periodically repeated by the current drive element It is defined by the length of the period for supplying current.
[Selection] Figure 3

Description

The present invention relates to an electronic device driving method, an electronic device, a semiconductor integrated circuit, and an electronic apparatus.

  An electroluminescence element that emits light when a driving current flows through a light-emitting thin film such as an organic semiconductor (hereinafter referred to as an organic EL element, regardless of the type of light-emitting material), or a fluorescent display tube element (hereinafter, VFD element). Current controlled thin film light emitting devices such as inorganic electroluminescence devices, light emitting diode (LED devices) surface emitting lasers (VCSEL), field emission devices (FED), etc. -An active matrix image display device that is driven and controlled by a silicon integrated circuit or an organic transistor has been proposed. The drive control by the TFT is suitable when the thin film light emitting element emits light with a current of several μA (microampere) or less.

  Due to the remarkable progress of technological development, the luminous efficiency of organic EL elements has been improved, and as a result, it has become possible to emit light with a small driving current. It has become possible to drive with LT-TFT.

  However, as the luminous efficiency of the organic EL element is rapidly improved, when the screen has the same brightness, there is no problem because the driving current in the high and middle gradation region is relatively large. However, in the low gradation region, the driving current is not a problem. Has become too small and accurate control has become difficult. The minute current value in this region is 10 nA (nanoampere), which is not much different from the leakage current when the driving transistor is off.

  For this reason, when the TFT for driving the light emitting pixel is turned off, a leak current from the adjacent wiring flows into the light emitting pixel in the non-light emitting state, and the non-light emitting element that should not emit light emits light weakly, and the contrast is lowered. And there are cases that cause contour blur. In this case, even if the luminous efficiency of the organic EL element is improved, accurate gradation display cannot be performed in a minute current region. Therefore, the display must be performed in a middle and high current region, and power for causing the organic EL element to emit light dominates. This is an obstacle to reducing the power consumption of a typical organic EL display.

  In addition, in order to perform low luminance display or display in a low gradation region, it is required that the LT-TFT circuit that drives each pixel operates accurately with respect to each gradation current. However, in order to cope with this, even if an attempt is made to write a minute current from the driver to the LT-TFT circuit including the analog memory of each pixel, the response time of the LT-TFT is slow and the leakage current causes a periodic display. There have been cases where writing does not end within a predetermined writing time necessary for the refresh operation, or it is difficult to accurately maintain the written value.

  An object of the present invention is to provide a technology that realizes accurate gradation control in a minute current region and reduction of current consumption of a display.

  In the electronic device driving method according to the present invention, the plurality of scanning lines, the plurality of signal lines, and the intersections of the scanning lines and the signal lines are disposed respectively. A current drive element, which acts according to the amount of drive current supplied to the current drive element, wherein the amount of drive current is periodically repeated on the value of the drive current and the current drive element. It is defined by the length of the period during which the drive current is supplied.

  In the electronic device driving method, the value of the driving current may be arbitrarily changed.

  In the driving method of the electronic device, the current driving element may be a current driving optical element whose optical characteristics are controlled by a current.

  In the electronic device driving method described above, the length of the period during which the driving current is supplied may be arbitrarily changed.

  In the driving method of the electronic device, an off control transistor is connected in series to the current driving optical element, and a period for supplying the driving current is arbitrarily changed by controlling an on / off timing of the off control transistor. You may do it.

  In the driving method of the electronic device, the length of the period for supplying the driving current is arbitrarily changed by the off-control transistor, and the off-control transistor also serves as a part of the circuit for setting the value of the driving current You may make it do.

  In the driving method of the electronic device, an organic electroluminescence element can be adopted as the current driving optical element. In this case, the gradation of the organic electroluminescence element can be set as the amount of the driving current. .

  In the driving method of the electronic device, it is preferable that the period for supplying the driving current to the current driving element includes at least two sub periods.

  In the driving method of the electronic device, it is preferable that the driving current is supplied to the current driving element in any one of the sub-periods when low gradation display or low luminance light emission is performed.

  In the driving method of the electronic device, when expressing at least the lowest gradation among a number of gradations expressed by supplying the driving current to the current driving element, the current driving element On the other hand, it is preferable to provide the sub period in which the driving current is not supplied.

  In the electronic device driving method, the sub period in which the driving current is supplied to the current driving element may be the same as or longer than the sub period in which the driving current is not supplied.

  In the driving method of the electronic device, when the driving current that is periodically repeated is supplied to the current driving element, the frequency is preferably set to 50 Hz or more.

  In the driving method of the electronic apparatus, interlaced scanning can be used for scanning the scanning line. Examples of interlaced scanning include interlace scanning.

  A first electronic device according to the present invention includes a plurality of scanning lines, a plurality of signal lines, and current drive elements respectively disposed corresponding to the intersections of the scanning lines and the signal lines. An electronic device that operates according to an amount of drive current supplied to the current drive element, wherein the amount of drive current is a value of the drive current and the drive that is periodically repeated by the current drive element It is defined by the length of the period for supplying current.

  In the electronic device, the value of the driving current may be arbitrarily changed.

  In the above electronic device, the current driving element may be a current driving optical element whose optical characteristics are controlled by a current.

  In the above electronic device, the length of the period for supplying the driving current may be arbitrarily changed.

  In the above electronic device, an off control transistor is connected in series to the current drive optical element, and the period for supplying the drive current is arbitrarily changed by controlling the on / off timing of the off control transistor. Also good.

  In the above electronic device, the length of the period for supplying the drive current is arbitrarily changed by the off control transistor, and the off control transistor can also be used as a part of the circuit for setting the value of the drive current. good.

  In the electronic device, a plurality of display-off control scanning lines are provided corresponding to the plurality of scanning lines, and the off-control transistors are connected to the display-off scanning lines and are synchronized with the selection operation of the scanning lines. It is preferable to provide a display off scan line driving circuit for outputting a display off scan signal to the off control transistor via the display off scan line corresponding to the selected scan line.

  In the above electronic device, the display-off scanning line driving circuit may be a scanning line driving circuit that selectively controls the plurality of scanning lines and a control circuit that controls a data line driving circuit that supplies a data signal to the plurality of signal lines. And may be controlled.

  In the above electronic device, an organic electroluminescence element can be adopted as the current drive optical element, and in this case, the gradation of the organic electroluminescence element can be set as the amount of the drive current.

  In the above electronic device, it is preferable that the period for supplying the driving current to the current driving element includes at least two sub periods.

  In the above electronic device, it is preferable to supply the driving current to the current driving element in any one of the sub-periods when performing low gradation display or low luminance display.

  In the electronic device, when expressing at least the lowest gradation among a number of gradations expressed by supplying the driving current to the current driving element, the current driving element It is preferable to provide the sub-period in which no drive current is supplied.

  In the above electronic device, it is preferable that the sub period in which the driving current is supplied to the current driving element is the same as or longer than the sub period in which the driving current is not supplied.

  In the above electronic device, when supplying the driving current that is periodically repeated to the current driving element, the frequency is preferably set to 50 Hz or more.

  In the above electronic apparatus, interlaced scanning may be performed when scanning a plurality of scanning lines. Examples of interlaced scanning include interlace scanning.

  The second electronic device of the present invention corresponds to a plurality of first signal lines, a plurality of second signal lines, and intersections of the plurality of signal lines and the plurality of second signal lines. An electronic device that operates according to the amount of drive current supplied to the driven element, wherein the amount of drive current is determined by the value of the drive current and the periodicity. And a length of a sub-period for supplying the drive current to the driven element provided within a predetermined period. Examples of the driven element include various electronic elements such as an electro-optical element and a current driving element.

In the second electronic device of the present invention, it is preferable that the length of the sub period varies depending on the amount of the driving current or the type of the driven element. For example, when the amount of the drive current is small, the sub period may be shortened. Further, when the type or electrical characteristics of the driven element are different, the length of the sub period may be set as appropriate in accordance with them. More specifically, when the electro-optical characteristics of R (red), G (green), and B (blue) are different as in an organic EL element to be described later, the length of the sub-period is appropriately set, and R ( You may make it balance the brightness | luminance of red (red), G (green), and B (blue).
The detailed aspect of the second electronic device of the present invention is the same as that of the first electronic device of the present invention.

  The semiconductor integrated circuit of the present invention is a semiconductor integrated circuit for supplying a drive current to a driven element, and the amount of the drive current to be supplied is provided within a predetermined period that repeats periodically with the value of the drive current. Further, it is possible to set according to the length of the sub-period for supplying the driving current to the driven element.

  In the electronic device and the driving method thereof according to the present invention described above, the following modes can be appropriately selected and employed as appropriate.

  The drive current value is set to a plurality of arbitrary values according to the amount of action. These values have at least three or more values.

The current driving element may be a current driving optical element whose optical characteristics are controlled by current.
The current drive optical element may be an organic electroluminescence element (organic EL element), and the drive current amount may correspond to a gradation.

  The period for supplying the driving current to the current driving element may include a driving period having at least two sub-periods that are periodically repeated.

  When performing display with a low gradation, the drive current may be supplied to the current drive element only in the first sub-period of the sub-periods.

  The sub-period in which the driving current is not supplied to the current driving element when expressing the gradation level 1 among the many gradation levels expressed by supplying the driving current to the current driving element. It is good also as providing.

  The sub period in which the drive current is supplied to the drive current element may be the same as or longer than the sub period in which the drive current is not supplied.

  When the driving current is periodically supplied to the current driving element, the frequency may be set to 50 Hz or more in order to prevent occurrence of flicker or the like.

  Similarly, in order to prevent occurrence of flicker or the like, interlaced scanning such as interlace may be performed when scanning the scanning line.

(First embodiment)
A first embodiment of the present invention will be described. In this embodiment, as an electronic device and a driving method thereof according to the present invention, an organic EL display device and a gray scale display control method will be described as examples.
As shown in FIG. 1, a circuit block diagram of an organic EL display device is directed to a display dot matrix unit 10, a vertical scanning drive circuit 20 attached thereto, a scanning signal generation circuit 30, and a display dot matrix unit 10. And a drive (gradation control) circuit 40 for supplying a display data signal and power (drive current).

  As is well known, the display dot matrix section 10 using organic EL elements as light emitting elements is formed by arranging unit pixels including organic EL elements in a matrix. As the circuit configuration and operation of the unit pixel, as described in, for example, the title “Electronic Display” (written by Shoichi Matsumoto, published by Ohm Co., Ltd., issued on June 20, 1996) (especially page 137). ), By supplying a driving current to each unit pixel, the light emission of the organic EL element is controlled by writing the analog memory including two transistors and a capacitor with a predetermined voltage. In the present invention, LT-TFTs are suitable as these active elements, but high-temperature polysilicon TFTs, amorphous TFTs, single crystal TFTs, silicon-based MOS transistors, thin film diode elements such as MIM (Metal Insulator Metal) elements, etc. It can be used.

  The drive circuit 40 and the scanning signal generation circuit 30 are realized by a driver IC, and functional blocks include a subframe (sub period) control unit 40a, a programmable code conversion unit 40b, a decoder 40c, a current output switch circuit 40d, and a luminance control unit. 40e, a reference current source generation circuit 40f, and a drive current generation circuit 40g. Based on the output signal from the scanning signal generation circuit 30, the subframe control unit 40 a generates a scanning clock for scanning by dividing each frame time into a plurality of subframe times (subperiods) and supplies the scanning clock to the vertical scanning driving circuit 20. And outputs a sub-frame (sub-period) classification signal toward the programmable code converter 40b. The programmable code conversion unit 40b to which the subframe classification signal is input converts a display decoder (not shown) from the control side according to a gradation conversion table (described later) stored in advance and digitally outputs it to the decoder unit 40c. . The decoder unit 40c to which the digital signal is input outputs a combination for outputting a predetermined drive current to the drive current output switch circuit 40d.

On the other hand, the luminance control unit 40e that receives a manual input (not shown) or a contrast control signal from an external light sensor outputs a predetermined luminance control signal to the reference current source generation circuit 40f based on this. The reference current source generation circuit 40f to which the luminance control signal is input generates a predetermined reference current based on the reference current source generation circuit 40f and outputs the reference current to the drive current generation circuit 40g. As will be described later, the drive current generating circuit 40g is composed of a plurality of current sources having different weights so that the drive current increases and decreases logarithmically in a form close to a straight line. The current output switch circuit 40d selects a combination of current sources based on the output of the decoder 40c, and converts digital display data into an analog current value. The current outputs of the plurality of current output switch circuits 40d are simultaneously applied to the data lines of the dot matrix unit 10 in synchronization with the output of the vertical scanning drive circuit 20. The reference current source generation circuit 40f uses, for example, a current mirror circuit, compares and changes the current values of all the plurality of current sources in the drive current generation circuit 40g, and outputs the result. As a result, the luminance range is increased or decreased, and the brightness of the screen (the entire dot matrix) is adjusted. The programmable code conversion unit 40b, the decoder 40c, the drive current generation circuit 40g, and the current output switch circuit 40d constitute a D / A conversion circuit that outputs a grayscale drive current toward the display dot matrix unit 10.
As is well known, the display dot matrix unit 10 controls and displays a predetermined image by causing the organic EL elements of each pixel to emit light in accordance with the input scanning line selection signal and logarithmic drive current. It becomes.

  In the organic EL display device having the configuration and functions as described above, a grayscale display driving method according to this embodiment will be described. As shown in the gradation conversion table of the display data code in FIG. 2, when the display data code is input to the programmable code conversion unit 40b, the first subframe (first subperiod) and the second subframe (second subframe) Time-divided into sub-periods) and converted, and output to the decoder 40c.

In the present embodiment, the time ratio between the first subframe and the second subframe is set to 0.7 to 0.3 as the time ratio between the first subframe and the second subframe, Accordingly, the second subframe is preferably set to 0.3 to 0.7.
This display data code is divided into four blocks from a low gradation area (“0 to 15” in the figure) to a high gradation area (“48 to 63” in the figure) for each gradation area. The display data code of each block other than the low gradation region (“16 to 31”, “32 to 47”, and “48 to 63” in the figure) is not converted and is converted into the first subframe and the second subframe. The same code is output to the decoder 40c for both subframes. In this case, since the same code is used in two subframes, it takes almost no time to write each pixel in the analog memory in the second subframe.

  On the other hand, as a matter related to the feature of the present invention, regarding the conversion of the display data code of each block in the low gradation area (“0 to 15” in the figure), first, the low gradation area is related to the first subframe. The display data code (“0 to 15”) is set to “16 to 39” with a higher gradation (higher write current) and a wider interval between write current values. In addition, in the second subframe, a display off code is automatically assigned so that the organic EL element does not emit light during this period.

  As a result, the human eye perceives the brightness that is integrated and averaged. This is shown by the graph β in the gradation characteristic diagram 3 showing the luminance of the pixel with respect to the drive current supplied from the drive current output switch circuit 40d. First, in the comparatively high luminance other than the low gradation region (in the figure, the range from point A to point B on the vertical axis), the display data code conversion is not performed in both the first subframe and the second subframe (see FIG. 2 is equivalent to each block of “16 to 31”, “32 to 47”, and “48 to 63” of the first and second subframes), and thus has substantially the same gradation characteristics as the conventional one, The gradation characteristic is indicated by the curve (solid line portion) of the graph α. In the curve of the graph α, the point corresponding to A on the vertical axis corresponds to the value “63” in the display data code in FIG. 2, and the point corresponding to the coaxial B in FIG. This corresponds to a value of 16 ″. In this range, the value of the drive current on the horizontal axis is never small and is not affected by the leakage current of the drive transistor pointed out in the section “Problems to be Solved by the Invention”.

  On the other hand, in the comparatively low luminance in the low gradation region shown in the range from point B to point C on the vertical axis in FIG. 3, the graph α is conventionally controlled in gradation on the curve. As shown in the range of the points c1 to b1, the drive current was very small and narrow. For this reason, under the influence of the leakage current of the driving transistor and insufficient writing, the contrast is lowered and the outline is blurred.

  On the other hand, in the present invention, in order to realize relatively low luminance in the same low gradation region (the range of points B to C on the vertical axis) shown in FIG. The gradation control is performed on the curve (solid line portion) of the graph β in which the ratio of the period is about 0.64: 0.36, and in a large and wide range such as the points c2 to b2 on the horizontal axis in FIG. I was able to drive current. That is, as described above, this low gradation region corresponds to the range of the display data codes “16 to 39” (before conversion “0 to 15”) of the first subframe in the gradation conversion table of FIG. That is, since the period of the second sub-frame is not displayed after the code conversion, the curve (solid line portion) of the graph β in FIG. 3 corresponds to the same drive current as a whole from the graph α to the human eye. The luminance appears to have become low, and the curve has a characteristic of lying relatively sideways. As a result, the drive current can be large and wide (points c2 to b2 on the horizontal axis in the figure) with respect to the same luminance range. In the curve of the graph β, the point closest to B on the vertical axis is the value “39” in the display data code of the first subframe in FIG. 2, and the point corresponding to the coaxial C is the same display in FIG. This corresponds to a value of “7” in the data code.

  In scanning the scanning line (vertical line), the time axis is scanned as shown in FIG. 4A. At this time, the frame frequency is set to 50 Hz or more. By doing so, flicker (so-called flickering) resulting from the division driving into subframes can be prevented.

  Another scanning method may be employed. That is, when scanning a scanning line (vertical line), an odd number of scanning lines (2m + 1: m is a natural number in the figure) are scanned first with respect to the time axis as shown in FIG. After scanning over the scanning lines, only the even number of scanning lines are scanned out. Thus, even when the frame frequency is low (for example, 50 Hz or less), the occurrence of flicker can be prevented, the appearance of the pseudo contour can be reduced, and the power can be reduced. In addition, the writing time can be made relatively long and writing with a margin can be performed.

  In the present embodiment, the number of sub-frames (sub-periods) is two. However, the number of sub-frames (sub-periods) is not limited to this, and a plurality of sub-frames can be configured as appropriate. Further, although the organic EL element is used as the light emitting element of the display pixel, any current driving element that is driven by passing a current may be used.

  Next, some examples in which the organic EL display device is used in a specific electronic device as an example of the electronic device described above will be described. First, an example in which the organic EL display according to this embodiment is applied to a mobile personal computer will be described. FIG. 5 is a perspective view showing the configuration of this mobile personal computer. In the figure, a personal computer 1100 includes a main body 1104 having a keyboard 1102 and a display unit 1106. The display unit 1106 includes the above-described organic EL display device.

  FIG. 6 is a perspective view showing a configuration of a mobile phone in which the above-described organic EL display device is applied to the display unit. In this figure, a cellular phone 1200 includes the electro-optical device 100 as well as a plurality of operation buttons 1202 as well as an earpiece 1204 and a mouthpiece 1206.

  FIG. 7 is a perspective view showing the configuration of a digital still camera in which the above-described organic EL display device 100 is applied to the finder. In this figure, the connection with an external device is also shown in a simplified manner. Here, the normal camera 1300 generates an imaging signal by photoelectrically converting a light image of a subject using an imaging device such as a CCD (Charge Coupled Device). The above-described organic EL display device is provided on the back surface of the case 1302 in the digital still camera 1300, and the display is based on the image pickup signal by the CCD. The organic EL display device functions as a finder for displaying a subject. To do. A light receiving unit 1304 including an optical lens, a CCD, and the like is provided on the observation side (the back side in the drawing) of the case 1302.

  When the photographer confirms the subject image displayed on the organic EL display device and presses the shutter button 1306, the CCD image pickup signal at that time is transferred and stored in the memory of the circuit board 1308. In the digital still camera 1300, a video signal output terminal 1312 and an input / output terminal 1314 for data communication are provided on the side surface of the case 1302. As shown in the figure, a television monitor 1430 is connected to the former video signal output terminal 1312 and a personal computer 1440 is connected to the latter input / output terminal 1314 for data communication as required. . Further, the imaging signal stored in the memory of the circuit board 1308 by a predetermined operation is output to the television monitor 1430 or the personal computer 1440.

  Electronic devices to which the organic EL display device of the present invention is applied include televisions, viewfinder types, monitors in addition to the personal computer of FIG. 5, the mobile phone of FIG. 6, and the digital still camera of FIG. Direct-view video tape recorder, car navigation device, pager, electronic notebook, calculator, word processor, workstation, video phone, POS terminal, touch panel equipped device, smart robot, dimmable lighting device, electronic book, lighting device And electronic printing / copying apparatus. And it cannot be overemphasized that the organic EL display apparatus and drive method which were mentioned above are applicable as a display part of these various electronic devices and an electro-optic conversion part.

  The second and third embodiments to be described next show specific examples in the case where the brightness of the screen is time-controlled as the embodiment in the first embodiment. In this embodiment, instead of assigning a display off code and performing off control of the drive current of the current drive element, display off control is performed on the pixel circuit in at least one sub-period, and the drive current can be simplified. Is to turn off.

(Second Embodiment)
Next, a second embodiment of the present invention will be described with reference to the drawings. In the present embodiment, an organic EL display device is used as an electronic device and a driving method thereof according to the present invention, an organic EL display device is used as the driving method, and an effective brightness (luminance) control method of the screen is taken as an example. Explained.

  In FIG. 8, the organic EL display device 50 includes a display panel unit 51, a writing scanning line driving circuit 52, a display off scanning line driving circuit 53, a data line driving circuit 54, and a control circuit 55.

  The display panel unit 51, the write scanning line driving circuit 52, the display off scanning line driving circuit 53, the data line driving circuit 54, and the control circuit 55 of the organic EL display device 50 may be configured by independent electronic components. . For example, the write scanning line driving circuit 52, the display off scanning line driving circuit 53, the data line driving circuit 54, and the control circuit 55 may be configured by a one-chip semiconductor integrated circuit device. Thus, by using a semiconductor integrated circuit, high accuracy, downsizing, and improvement in assembly efficiency can be achieved. Further, the display panel unit 51, the write scanning line driving circuit 52, the display off scanning line driving circuit 53, the data line driving circuit 54, and the control circuit 55 may be configured as an electronic component in which all or a part is integrated. . For example, the writing scanning line driving circuit 52, the display off scanning line driving circuit 53, and the data line driving circuit 54 may be integrally formed on the display panel unit 51. Further, all or a part of the write scanning line driving circuit 52, the display off scanning line driving circuit 53, the data line driving circuit 54, and the control circuit 55 are configured by a programmable IC chip, and the function is written to the IC chip. May be implemented in software.

  As shown in FIG. 8, the display panel unit 51 includes a plurality of pixel circuits 60 arranged in a matrix. That is, each pixel circuit 60 includes a plurality (m) of data lines X1 to Xm (m is a natural number) extending along the column direction and a plurality (n) of write scanning lines Y1 extending along the row direction. To Yn (n is a natural number). The pixel circuits 60 are arranged in a matrix by being connected between the corresponding data lines X1 to Xm and the writing scanning lines Y1 to Yn, respectively.

Each pixel circuit 60 is connected to a plurality of display-off scanning lines YS1 to YSn (n is a natural number) extending in the row direction (the same number as the writing scanning lines Y1 to Yn).
Each pixel circuit 60 has an organic EL element 61 as a current driving element or a driven element whose light emitting layer is made of an organic material. Note that a transistor described later formed in the pixel circuit 60 is usually constituted by a thin film transistor (TFT).

FIG. 9 shows an example of an electric circuit diagram for explaining the internal circuit configuration of the pixel circuit 60. For convenience of explanation, it is arranged at the point of the m-th data line Xm, the n-th write scanning line Yn, and the display-off scanning line YSn, and is connected between the two data lines Xm and the scanning lines Yn, YSn. The pixel circuit 60 will be described. Corresponding control time charts are shown in FIGS. FIG. 10 shows a case where the organic EL element 61 is turned off only during a period (one horizontal scan) in which the standard display data current Idm is programmed. FIG. 11 is a diagram showing a specific example when the time control of the present invention is applied continuously in the current program off period with respect to the case of FIG.
The pixel circuit 60 includes a driving transistor Q20, first and second switching transistors Q21 and Q22, a starting transistor Q23, and a holding capacitor C1 as a capacitive element. The driving transistor Q20 is composed of a P-channel FET. The first and second switching transistors Q21 and Q22 and the start transistor Q23 are configured by N-channel FETs.

  The drive transistor Q20 has a drain connected to the anode of the organic EL element 61 via the start transistor Q23, and a source connected to the power supply line L1. A drive voltage VOEL for driving the organic EL element 61 is supplied to the power supply line L1. A holding capacitor C1 is connected between the gate of the driving transistor Q20 and the power supply line L1.

  The first switching transistor Q21 is connected between the gate and drain of the driving transistor Q20. The gate of the first switching transistor Q21 is connected to the writing scanning line Yn together with the gate of the second switching transistor Q22, and the writing scanning signal SCn is input from the writing scanning line Yn. It has become.

  The drain of the second switching transistor Q22 is connected to the drain of the driving transistor Q20. The source of the second switching transistor Q22 is connected to the data line Xm. The gate of the start transistor Q23 is connected to the display-off scanning line YSn, and the display-off scanning signal DEn is input from the display-off scanning line YSn. The start transistor Q23 connected in series with the drive transistor Q20 is an off control transistor.

  Now, the first and second switching transistors Q21 and Q22 are in the off state. From this state, the write scanning signal SCn at the H level and the L level at the gates of the first and second switching transistors Q21 and Q22 via the scanning line Yn are set for a predetermined time T1 (see FIGS. 10 and 11). The display-off scanning signal DEn is output in synchronization with the scanning clock signal YSL. When the first and second switching transistors Q21, Q22 are turned on in response to the write scanning signal SCn, the gate voltage necessary for the driving transistor Q20 to flow the data current Idm from the data line Xm is applied to the holding capacitor C1. Set.

  The value of the data current Idm is determined by the data driving circuit 54 based on the gradation data. As a result, the voltage applied to the gate of the driving transistor Q20 falls to a voltage based on the data current Idm by compensating for the characteristic variation of the transistor Q20 in a self-aligning manner.

  When the write scan signal SCn becomes L level in synchronization with the next rise of the scan clock signal YSL, the first and second switching transistors Q21 and Q22 are turned off, and the supply of current to the holding capacitor C1 is cut off. At this time, the voltage corresponding to the data current Idm is held in the holding capacitor C1 by turning off the transistors Q21 and Q22.

  Subsequently, when an H-level display-off scanning signal DEn is output from the display-off scanning line YSn in synchronization with the fall of the scanning clock signal YSL, the start transistor Q23 is turned on. Here, it is assumed that the drive-off data signal DIN is input to the display-off scanning line driving circuit after the rising edge of the scanning clock signal YSL. When the start transistor Q23 is turned on, the drive transistor Q20 becomes conductive according to the value of the data current Idm held in the holding capacitor C1, and the drive current corresponding to the data current Idm is supplied to the organic EL element 61. The The organic EL element 61 emits light at a luminance corresponding to the data current Idm until the writing scanning line Yn is next selected.

  At this time, the brightness is controlled by controlling the timing at which the start transistor Q23 is turned on and the display-off scanning signal DEn output from the display-off scanning line YSn. That is, for each pixel circuit 60, the brightness of the screen (the entire dot matrix) is adjusted by controlling the timing at which the start transistor Q23 is turned on while expressing the halftone with the data current Idm. become. More specifically, if the timing at which the start transistor Q23 is turned on for each pixel circuit 60 is delayed, the light emission period is shortened, so that the brightness (luminance) of the entire screen can be reduced. On the contrary, if the timing at which the start transistor Q23 is turned on for each pixel circuit 60 is advanced, the light emission period becomes longer, so that the brightness (luminance) of the entire screen can be increased.

  The write scan line driving circuit 52 selects one of the write scan lines Y1 to Yn, that is, outputs write scan signals SC1 to SCn, and the pixel circuit 60 connected to the selected write scan line. A circuit for driving the group. Based on the scanning clock signal YSL and the frame start signal FS from the control circuit 55, the scanning line drive circuit 52 writes the scanning signal SC1 for writing at a predetermined timing with respect to each scanning line Y1 to Yn as shown in FIG. ~ SCn are output respectively.

  The display-off scanning line driving circuit 53 simultaneously selects one of the display-off scanning lines YS1 to YSn, that is, outputs display-off scanning signals DE1 to DEn, and is connected to the selected writing scanning line. This is a circuit for sequentially driving the pixel circuits 60 group. The display off scanning line driving circuit 53 outputs display off scanning signals DE1 to DEn in synchronization with the writing scanning line driving circuit 52 based on the scanning clock signal YSL and the driving off data signal DIN from the control circuit 55. That is, the display-off scanning line driving circuit 63 sequentially selects the pixel circuits 60 on the selected connected scanning lines in the order in which the writing scanning line driving circuit 52 selects the writing scanning lines, and displays off. A scanning signal is output. Specifically, as shown in FIG. 10, when the write scan signals SC1 to SCn are sequentially output, the display-off scan line drive circuit 63 displays the L level in response to the write scan signals SC1 to SCn. When the off scan signals DE1 to DEn are sequentially output and the time determined by the pulse width T of the drive off data signal DIN has elapsed, the display off scan signals DE1 to DEn sequentially rise from the L level to the H level.

  The data line driving circuit 54 includes a data current output circuit 54a (see FIG. 9) for each of the data lines X1 to Xm. Each data current output circuit 54a receives the gradation data from the control circuit 55, generates data currents Id1 to Idm based on the gradation data, and corresponds to the corresponding data line X1 in synchronization with the write scanning signal. Output to ~ Xm respectively.

  In order to express one frame of display data D on the organic EL display device 50, the control circuit 55 is connected to the scanning lines Y1 to Yn for each of the writing scanning lines Y1 to Yn selected in order. The gradation data for generating the data currents Id1 to Idm for the pixel circuit 60 is converted and generated based on the display data D of one frame. The control circuit 55 outputs the generated gradation data to each data current output circuit 54a of the data line driving circuit 54 at a predetermined timing. The circuit of FIG. 1 is included in the control circuit 55.

  The control circuit 55 outputs a scanning clock signal YSL and a frame start signal FS indicating a start timing for one frame to the writing scanning line driving circuit 52. The write scan line drive circuit 52 selects scan lines in order based on the scan clock signal YSL and the frame start signal FS and controls the write scan signals SC1 to SCn for controlling each pixel circuit 60 on the selected scan line. Is generated.

  Further, the control circuit 55 generates a scanning clock signal YSL and a driving off data signal DIN for the display off scanning line driving circuit 53. The drive-off data signal DIN is a signal that determines a time T from when the display-off scanning signal DE1 to DEn is lowered from the H level to the L level and then raised from the L level to the H level in the display off scanning line driving circuit 53. is there. In other words, the time for which the start transistor Q23 is kept off is determined. The drive-off data signal DIN is a signal whose pulse width T is controlled by a screen brightness control signal PL that indicates the brightness (brightness) of the entire screen input to the control circuit 55 from an external device. The screen brightness control signal PL may be a signal output by manual operation, a signal calculated by an external device according to the brightness of external light, or a control signal related to moving image display.

  For example, when the manual operation or the external light is dark and the screen brightness control signal PL for increasing the brightness (brightness) of the entire screen of the organic EL display device 50 is output from the external device, the control circuit 55 As shown in FIG. 10, a drive off data signal DIN having a short pulse width T (corresponding to one horizontal scanning period (1H)) is output. On the other hand, when the manual operation or the external light is comparatively bright and the screen brightness control signal PL for darkening the screen of the organic EL display device 50 is output, the control circuit 55, as shown in FIG. A drive off data signal DIN having a long pulse width T (corresponding to four times one horizontal scanning period (1H)) is output.

  Accordingly, when the drive off data signal DIN having a short pulse width T (corresponding to one horizontal scanning period) is output from the control circuit 55 as shown in FIG. 10, the organic circuit of each pixel circuit 60 of the selected writing scanning line is output. The light emission corresponding to the data current of the EL element 61 starts when the next writing scanning line is selected.

  When the control circuit 55 outputs a drive off data signal DIN having a long pulse width T (corresponding to four times one horizontal scanning period) as shown in FIG. 11, each pixel circuit of the selected writing scanning line is output. The light emission corresponding to the data current of the 60 organic EL elements 61 starts to emit light when the writing scan line is selected after the OFF period of the pulse width T of the drive off data signal DIN is turned off.

  Therefore, since the light emission period TS based on the drive off data signal DIN shown in FIG. 10 is longer than the light emission period TS based on the drive off data signal DIN shown in FIG. 11, the brightness (luminance) of the entire screen is increased. Can do. That is, the gradation is expressed by the data current, and the brightness (luminance) of the entire screen can be adjusted by the drive-off data signal DIN. By the way, when controlling the brightness (luminance) of the entire screen by controlling the light emission period, the off period is set simultaneously for at least R (red), G (green), and B (blue) dots in the pixel. Although it is preferable to prevent color bleeding, the length of the on period is long depending on the electro-optical characteristics of R (red), G (green), and B (blue), the desired color balance, and the like. The thickness may be set as appropriate.

  In addition, as an electronic apparatus to which the organic EL display device 50 of the present embodiment is applied, in addition to the personal computer of FIG. 5, the mobile phone of FIG. 6, and the digital still camera of FIG. , Monitor direct-view video tape recorder, car navigation device, pager, electronic notebook, calculator, word processor, workstation, video phone, POS terminal, touch panel equipped device, smart robot, dimmable lighting device, electronic book, electronic Examples include decoration devices and electronic printing / copying devices. And it cannot be overemphasized that the organic EL display apparatus and drive method which were mentioned above are applicable as a display part and electro-optical conversion part of these various electronic devices.

(Third embodiment)
Next, a third embodiment of the present invention will be described with reference to the drawings. In the present embodiment, an organic EL display device is used as an electronic device and a driving method thereof according to the present invention, an organic EL display device is used as the driving method, and an effective brightness (luminance) control method of the screen is taken as an example. Explained. The present embodiment is characterized in that the circuit configuration of the pixel circuit and the timing of the light emission period TS are different from those of the second embodiment. Therefore, the characteristic part will be described in detail for convenience of description. The pixel circuit 70 shown in FIG. 12 is arranged at the point of the mth data line Xm, the nth write scanning line Yn, and the display-off scanning line YSn, as in the above embodiment, Another pixel circuit example connected between the lines Yn and YSn is shown.

  The pixel circuit 70 includes a driving transistor Q30, a first switching transistor Q31, a second switching transistor 32, a conversion transistor Q33, and a holding capacitor C1 as a capacitive element. The driving transistor Q30 and the conversion transistor Q33 are composed of P-channel FETs. The first and second switching transistors Q21 and Q22 are composed of N-channel FETs.

  The driving transistor Q30 has a drain connected to the anode of the organic EL element 71 and a source connected to the power supply line L1. A drive voltage VOEL for driving the organic EL element 71 is supplied to the power supply line L1. One end of the holding capacitor C1 is connected to the gate of the driving transistor Q30, and the driving voltage VOEL is applied to the other end of the holding capacitor C1. The gate of the driving transistor Q30 is connected to the gate of the converting transistor Q33, and the driving voltage VOEL is applied to the source of the converting transistor Q33.

  Transistors Q32, Q33, and Q30 constitute a current mirror circuit. Ideally, the current flowing through transistor 33 is proportionally reduced and flows through transistor Q30 at the size ratio of transistors Q33 and Q30.

  The drain of the conversion transistor Q33 is connected to the data line Xm via the first switching transistor Q31. The gate of the first switching transistor Q31 is connected to the write scan line Yn, and the write scan signal SCn is input from the write scan line Yn.

  A second switching transistor Q32 as an off control transistor is connected between the gate and drain of the conversion transistor Q33. The gate of the second switching transistor Q32 is connected to the display-off scanning line YSn, and the display-off scanning signal DEn is input from the display-off scanning line YSn.

Next, the operation of the pixel circuit 70 configured as described above will be described.
Now, the writing scanning signal SCn is at L level and the display-off scanning signal DEn is at H level. At this time, the first switching transistor Q31 is in an off state and the second switching transistor Q32 is in an on state. From this state, the H-level scanning signal SCn is output to the gate of the first switching transistor Q31 via the scanning line Yn for a predetermined time T1 (see FIG. 13). When the first switching transistor Q31 is turned on in response to the write scanning signal SCn, the data current Idm is supplied from the data line Xm via the first switching transistor Q31. At this time, the gate voltage of the conversion transistor Q33 becomes a voltage level relative to the data current Idm, and the voltage level is held in the holding capacitor C1.

  As a result, the voltage applied to the gate of the driving transistor Q30 becomes a voltage level based on the data current Idm, and the driving transistor Q30 supplies a current amount relative to the data current Idm to the organic EL element 71. That is, a drive current proportional to the data current Idm is supplied to the organic EL element 71, and the organic EL element 71 starts to emit light at a gradation corresponding to the data current Idm.

  After a lapse of time T1, the first switching transistor Q31 is turned off when the H-level writing scan signal SCn falls from the H level to the L level. At the same time, when the display-off scanning signal DEn falls from the H level to the L level, the second switching transistor Q32 is also turned off. As a result, the voltage level corresponding to the data current Idm is held in the holding capacitor C1. As a result, the driving transistor Q30 continues to supply a current amount proportional to the data current Idm to the organic EL element 71, and the organic EL element 71 emits light at a gradation corresponding to the data current Idm.

  Thereafter, when the display-off scanning signal DEn rises from the L level to the H level, the second switching transistor Q32 is turned on, and the charge stored in the capacitor C1 is discharged via the conversion transistor Q33, so that the conversion transistor The gate voltage of Q33 and driving transistor Q30 is boosted to turn off transistor Q33 and transistor 30 substantially. As a result, the light emission of the organic EL element 71 is stopped, and the process waits until the writing scanning line Yn is next selected.

  That is, the pixel circuit 70 of the embodiment emits light until the display-off scanning signal DEn rises from the L level to the H level, as opposed to the pixel circuit 60. Therefore, as shown in FIG. Contrary to the above embodiment, it is different in that it is started simultaneously with the writing of the data current Idm. Therefore, even when the pulse width T of the drive-off data signal DIN is set by the screen brightness control signal PL, it is necessary to change it accordingly.

  Then, the brightness (luminance) of the entire screen is controlled by controlling the timing at which the second switching transistor Q32 is turned on, that is, the display-off scanning signal DEn output from the display-off scanning line YSn. That is, also in each pixel circuit 70, the brightness (luminance) of the screen (the entire dot matrix) is controlled by controlling the timing at which the second switching transistor Q32 is turned on while expressing the halftone with the data current Idm. ) Will be adjusted. That is, the second switching transistor Q32 also serves as a part of a circuit that controls the light emission period TS and sets the data current Idm. More specifically, if the timing at which the second switching transistor Q32 is turned on for each pixel circuit 70 is advanced, the light emission period TS is shortened, so that the brightness (luminance) of the entire screen can be reduced. On the contrary, if the timing at which the second switching transistor Q32 is turned on for each pixel circuit 70 is delayed, the light emission period TS becomes longer, so that the brightness (luminance) of the entire screen can be increased. By the way, when controlling the brightness (luminance) of the entire screen by controlling the light emission period, the off period is set simultaneously for at least R (red), G (green), and B (blue) dots in the pixel. Although it is preferable to prevent color bleeding, the length of the on period is long depending on the electro-optical characteristics of R (red), G (green), and B (blue), the desired color balance, and the like. The thickness may be set as appropriate.

  As an electronic apparatus to which the organic EL display device of this embodiment is applied, in addition to the personal computer of FIG. 5, the mobile phone of FIG. 6, and the digital still camera of FIG. 7, a TV, a viewfinder type, Monitor direct-view video tape recorder, car navigation device, pager, electronic notebook, calculator, word processor, workstation, videophone, POS terminal, touch panel equipped device, smart robot, dimmable lighting device, electronic book, illumination And an electronic printing / copying apparatus. And it cannot be overemphasized that the organic EL display apparatus and drive method which were mentioned above are applicable as a display part and electro-optical conversion part of these various electronic devices.

  Further, the pixel circuit 60 shown in the second embodiment may be implemented so that the light emission period TS starts simultaneously with the writing of the data current Idm, as shown in the third embodiment.

  Further, in the second and third embodiments, the display device as the electronic device is a color display device, and current driving of different colors such as R (red), G (green), and B (blue) in the pixel is performed. When setting the current value corresponding to low gradation or the light emission period corresponding to the brightness (luminance) of the entire screen for the light emitting element as the element or the driven element, the electrical characteristics of the light emitting element are different. In this case, the current value or the light emission period for each color light emitting element may be changed in accordance with the characteristics.

  In the second and third embodiments, the scanning is performed sequentially when scanning the scanning lines, but may be performed by interlaced scanning.

  In each of the above embodiments, the display device includes an organic electroluminescence element (organic EL element) as a current-driven optical element, but a fluorescent display tube element (hereinafter referred to as a VFD element), an inorganic electroluminescence element, and light emission. The present invention may be applied to a display device or a printing / electronic copying apparatus provided with a laser element such as a diode (LED element) surface emitting laser (VCSEL) and a current-controlled thin film light emitting element such as a field emission element (FED).

  Further, each of the embodiments described above is embodied in an electro-optical display device that is an electronic device using an electro-optical element. However, other than the electro-optical device, for example, an electronic device such as a memory device using a magnetic RAM as a driven element You may apply to.

Other features of the present invention will become apparent from the accompanying drawings and the following description.
1 is a circuit block diagram of an organic EL display device according to a first embodiment of the present invention. It is a graph which shows the gradation conversion table of the display data code in the gradation control method of the organic electroluminescence display which concerns on 1st Embodiment of this invention. 4 is a graph of gradation characteristics showing the luminance (gradation reproduction range) of a pixel with respect to a drive current in the gradation control method of the organic EL display device according to the first embodiment of the present invention. It is a schematic diagram which shows the scanning method which selects the scanning line (vertical line) in the gradation control method of the organic electroluminescent display apparatus which concerns on 1st Embodiment of this invention, (a) shows the case where line-sequential scanning is performed, ( b) shows a case where odd-numbered vertical lines are scanned first. It is a figure which shows an example at the time of applying the electronic device by 1st Embodiment of this invention to a mobile personal computer. It is a figure which shows an example at the time of applying the electronic device by 1st Embodiment of this invention to the display part of a mobile telephone. It is a figure which shows the perspective view of the digital still camera which applied the electronic device by 1st Embodiment of this invention to the finder. It is a circuit block diagram of the organic electroluminescence display which concerns on 2nd Embodiment of this invention. FIG. 6 is a circuit diagram of a pixel circuit according to a second embodiment of the present invention. It is a time chart for demonstrating the effect | action of the organic electroluminescence display which concerns on 2nd Embodiment of this invention. It is a time chart for demonstrating the effect | action of the organic electroluminescence display which concerns on 2nd Embodiment of this invention. FIG. 6 is a circuit diagram of a pixel circuit according to a third embodiment of the present invention. It is a time chart for demonstrating the effect | action of the organic electroluminescence display which concerns on 3rd Embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Display dot matrix part, 20 ... Vertical scanning drive circuit, 30 ... Scan signal generation circuit, 40 ... Drive circuit, 40a ... Sub-frame control part, 40b ... Programmable code conversion part, 40c ... Decoder, 40d... Drive current output switch circuit.

Claims (32)

A plurality of scanning lines; a plurality of signal lines; and current driving elements respectively disposed corresponding to the intersections of the scanning lines and the signal lines. The current driving elements are supplied to the current driving elements. A method of driving an electronic device that operates according to the amount of drive current,
The method of driving an electronic device according to claim 1, wherein the drive current amount is defined by a value of the drive current and a length of a period in which the drive current is periodically repeated to the current drive element.   2. The electronic device driving method according to claim 1, wherein the value of the driving current can be arbitrarily changed.   3. The method of driving an electronic apparatus according to claim 1, wherein the current driving element is a current driving optical element whose optical characteristics are controlled by a current.   4. The method for driving an electronic device according to claim 1, wherein a length of a period for supplying the driving current can be arbitrarily changed.   5. The method for driving an electronic device according to claim 4, wherein an off control transistor is connected in series to the current drive optical element, and a period for supplying the drive current is controlled by controlling an on / off timing of the off control transistor. A method of driving an electronic device, wherein the electronic device is arbitrarily changed.   5. The method of driving an electronic device according to claim 4, wherein a length of the period for supplying the drive current is arbitrarily changed by an off control transistor, and the off control transistor sets a value of the drive current. A method for driving an electronic device, wherein a part of the electronic device is also used.   7. The method for driving an electronic device according to claim 3, wherein the current driving optical element is an organic electroluminescence element, and the amount of the driving current corresponds to a gradation. Method for driving an electronic device. The method for driving an electronic device according to claim 1,
The method for driving an electronic device, wherein the period for supplying the driving current to the current driving element includes at least two sub-periods.   9. The method of driving an electronic device according to claim 8, wherein the driving current is supplied to the current driving element during any one of the sub-periods when low gradation display or low luminance light emission is performed. An electronic device driving method.   10. The method of driving an electronic device according to claim 8, wherein at least the lowest gradation level is expressed among a plurality of gradation levels expressed by supplying the driving current to the current driving element. A method for driving an electronic device, comprising: providing the sub-period in which the drive current is not supplied to the current drive element.   11. The driving method of an electronic device according to claim 10, wherein the sub period in which the driving current is supplied to the current driving element is equal to or longer than the sub period in which the driving current is not supplied. A method for driving an electronic device.   12. The method of driving an electronic device according to claim 1, wherein when the driving current that is periodically repeated is supplied to the current driving element, the frequency thereof is set to 50 Hz or more. Driving method.   13. The method for driving an electronic device according to claim 1, wherein interlaced scanning is performed when scanning the scanning line. A drive provided with a plurality of scanning lines, a plurality of signal lines, and a current driving element disposed corresponding to each intersection of each of the scanning lines and the signal lines, and supplied to the current driving element An electronic device that operates according to the amount of current,
The electronic device is characterized in that the drive current amount is defined by a value of the drive current and a length of a period in which the drive current is periodically supplied to the current drive element.   15. The electronic device according to claim 14, wherein the value of the driving current can be arbitrarily changed.   16. The electronic apparatus according to claim 14, wherein the current driving element is a current driving optical element whose optical characteristics are controlled by a current.   17. The electronic device according to claim 14, wherein a length of a period during which the driving current is supplied can be arbitrarily changed.   18. The electronic device according to claim 17, wherein an off-control transistor is connected in series to the current-driven optical element, and a period for supplying the drive current is arbitrarily changed by controlling on / off timing of the off-control transistor. An electronic device characterized in that the electronic device is made to operate.   The electronic device according to claim 17, wherein a length of a period for supplying the driving current is arbitrarily changed by an off control transistor, and a part of a circuit in which the off control transistor sets a value of the driving current An electronic device characterized by being also used. The electronic device according to claim 18 or 19,
A plurality of display-off control scan lines are provided corresponding to the plurality of scan lines, the off-control transistor is connected to the display-off scan line, and the selected scan is synchronized with the selection operation of the scan line. An electronic device comprising a display off scanning line driving circuit for outputting a display off scanning signal to the off control transistor via a display off scanning line corresponding to the line. The electronic device according to claim 20,
The display-off scanning line driving circuit is controlled by a scanning line driving circuit that selectively controls the plurality of scanning lines and a control circuit that controls a data line driving circuit that supplies a data signal to the plurality of signal lines. Electronic device characterized.   22. The electronic device according to claim 16, wherein the current driving optical element is an organic electroluminescence element, and the amount of the driving current corresponds to a gradation level. . The electronic device according to any one of claims 14 to 22,
The electronic apparatus according to claim 1, wherein the period for supplying the driving current to the current driving element includes at least two sub periods.   24. The electronic apparatus according to claim 23, wherein the driving current is supplied to the current driving element in any one of the sub-periods when performing low gradation display or low luminance display. .   25. The electronic device according to claim 23, wherein, when expressing at least a minimum gradation among a plurality of gradations expressed by supplying the driving current to the current driving element, the current An electronic apparatus comprising: the sub-period in which the driving current is not supplied to the driving element.   26. The electronic device according to claim 25, wherein the sub-period for supplying the drive current to the current drive element is the same as or longer than the sub-period for not supplying the drive current. Electronic device to play.   27. The electronic apparatus according to claim 14, wherein the frequency is set to 50 Hz or more when the driving current that is periodically repeated is supplied to the current driving element.   28. The electronic device according to claim 14, wherein interlaced scanning is performed when scanning a plurality of scanning lines. A plurality of first signal lines; a plurality of second signal lines; and a driven element disposed corresponding to an intersection of the plurality of signal lines and the plurality of second signal lines. An electronic device that operates according to the amount of drive current supplied to the driven element,
The amount of the drive current is set by a value of the drive current and a length of a sub-period in which the drive current is supplied to the driven element provided within a predetermined period that is periodically repeated. Electronic device to play. 30. The electronic device of claim 29.
The length of the sub period is different depending on the amount of the driving current or the type of the driven element. A semiconductor integrated circuit for supplying a drive current to a driven element,
It is possible to set the amount of drive current to be supplied by the value of the drive current and the length of a sub-period in which the drive current is supplied to the driven element provided within a predetermined period that is periodically repeated. Semiconductor integrated circuit. 31. An electronic device on which the electronic device according to claim 14 is mounted.