JP4496469B2 - Display drive device, display device, and drive control method thereof - Google Patents

Description

  The present invention relates to a display drive device, a display device, and a drive control method thereof, and more particularly, a display pixel including a current control type light emitting element that emits light at a predetermined luminance gradation by supplying a current according to display data. The present invention relates to a display drive device applicable to a display panel formed by arranging a plurality of display devices, a display device including the display drive device, and a drive control method in the display device.

  Conventionally, a light emitting operation is performed at a predetermined luminance gradation in accordance with a current value of a driving current supplied like an organic electroluminescent element (hereinafter abbreviated as “organic EL element”) or a light emitting diode (LED). 2. Description of the Related Art A light emitting element type display (display device) including a display panel in which display pixels each having a current control type light emitting element are two-dimensionally arranged is known.

  In particular, a light-emitting element type display using an active matrix driving method has a higher display response speed than a liquid crystal display (LCD) widely used in various electronic devices including portable devices in recent years. There is no viewing angle dependency, and it is possible to achieve high brightness, high contrast, high definition of display image quality, etc., and unlike the case of liquid crystal display devices, a backlight is not required, making it even thinner and lighter. It has the extremely advantageous feature of being able to reduce power consumption, and research and development are actively conducted as a next-generation display.

  In such a light emitting element type display, various drive control mechanisms and control methods for controlling light emission of the above-described current control type light emitting element have been proposed. For example, as described in Patent Document 1 and the like, for each display pixel constituting the display panel, in addition to the light-emitting element, a drive circuit including a plurality of switching means for controlling light emission of the light-emitting element ( A device having a light emission drive circuit) is known.

  FIG. 22 is a schematic configuration diagram showing a main part of a light emitting element type display in the prior art, and FIG. 23 is a configuration example of display pixels (light emitting drive circuit and light emitting element) applicable to the light emitting element type display in the prior art. FIG.

  As shown in FIG. 22, the active matrix organic EL display device described in Patent Document 1 and the like schematically includes a plurality of scanning lines (selection lines) SL and data lines (signal lines) arranged in the row and column directions. ) A display panel 110P in which a plurality of display pixels EMp are arranged in a matrix in the vicinity of each intersection of DL, a scanning driver (scanning line driving circuit) 120P connected to each scanning line SL, and a connection to each data line DL As shown in FIG. 23, each display pixel EMp has a gate terminal on the scanning line SL, and a source terminal and a drain terminal on the data line. The thin film transistor (TFT) Tr111 connected to the DL and the contact N111 respectively, and the gate terminal is connected to the contact N111, and the source terminal A light emitting drive circuit DCp having a thin film transistor Tr112 to which a ground potential Vgnd is applied, and an anode terminal connected to a drain terminal of the thin film transistor Tr112 of the light emission drive circuit DCp, and a cathode terminal having a potential lower than the ground potential Vgnd It has an organic EL element (current control type light emitting element) OEL to which a low power supply voltage Vss is applied.

  Here, in FIG. 23, Cp is a parasitic capacitance (retention capacitance) formed between the gate and the source of the thin film transistor Tr112. The thin film transistor Tr111 is formed of an n-channel field effect transistor, and the thin film transistor Tr112 is formed of a p-channel field effect transistor.

  In the display device including the display panel 110P including the display pixel EMp having such a configuration, first, the scan driver 120P sequentially applies the high level scan signal Vsel to the scan line SL of each row, thereby The thin film transistor Tr111 of each display pixel EMp (light emission drive circuit DCp) is turned on, and the display pixel EMp is set to the selected state.

  In synchronization with this selection timing, the grayscale signal voltage Vpix corresponding to the display data is generated by the data driver 130P and applied to the data line DL of each column, whereby the grayscale signal voltage Vpix is applied to each display pixel EMp. The voltage is applied to the contact N111 (that is, the gate terminal of the thin film transistor Tr112) via the thin film transistor Tr111 of the (light emission drive circuit DCp). Thereby, the thin film transistor Tr112 is turned on in a conductive state corresponding to the gradation signal voltage Vpix, and a predetermined light emission drive current flows from the ground potential Vgnd to the low power supply voltage Vss through the thin film transistor Tr112 and the organic EL element OEL. The organic EL element OEL emits light at a luminance gradation corresponding to display data.

  Next, by applying a low level scanning signal Vsel from the scanning driver 120P to the scanning line SL, the thin film transistor Tr111 of the display pixel EMp in each row is turned off, and the display pixel EMp is set to a non-selected state. The data line DL and the light emission drive circuit DCp are electrically disconnected. At this time, on the basis of the voltage applied to the gate terminal of the thin film transistor Tr112 and held in the parasitic capacitance Cp, the thin film transistor Tr112 is maintained in the on state. The light emission drive current flows to the organic EL element OEL via the thin film transistor Tr112, and the light emission operation is continued. This light emission operation is controlled so as to continue, for example, for one frame period until the gradation signal voltage Vpix corresponding to the next display data is applied (written) to the display pixel EMp of each row.

  Such a drive control method adjusts the voltage (gradation signal voltage Vpix) applied to each display pixel EMp (the gate terminal of the thin film transistor Tr112 of the light emission drive circuit DCp), thereby causing the light emission drive current to flow through the organic EL element OEL. This is called a voltage designation method (or voltage application method) because the light emission operation is performed at a predetermined luminance gradation by controlling the current value of the current.

  By the way, in the display pixel EMp provided with the light emission drive circuit DCp adopting such a voltage designation method, the element characteristics (channel resistance and the like) of the thin film transistor Tr111 having the selection function and the thin film transistor Tr112 having the light emission drive function are affected by the external environment. When variation or fluctuation (deterioration) occurs depending on (ambient temperature, etc.) or use time, the light emission driving current supplied to the light emitting element (organic EL element OEL) fluctuates. There is a problem that it becomes difficult to stably realize desired light emission characteristics (display with a predetermined luminance gradation) over a period of time.

  Further, when each display pixel is miniaturized in order to increase the definition of the display panel, variation in operating characteristics (such as a source-drain current) of the thin film transistors Tr111 and Tr112 constituting the light emission driving circuit DCp increases. Appropriate gradation control cannot be performed, and there is a problem in that the light emission characteristics of each display pixel vary and display image quality deteriorates.

  Therefore, as a configuration for solving such a problem, a configuration of a light emission driving circuit corresponding to a drive control method called a current application method (or current designation method) is known. A specific configuration example of a display pixel (light emission drive circuit) corresponding to this current application method will be described in detail in “Best Mode for Carrying Out the Invention” to be described later. It has a configuration and operation (function).

  That is, in the light emission drive circuit corresponding to the current application method, the drive current control means (the above-described thin film transistor described above) that controls the current value and the supply state of the light emission drive current supplied to the light emitting element (for example, the above-described organic EL element). A gradation current that specifies a current value corresponding to display data to the drive current control means from the data driver via each data line to each display pixel (light emission). The grayscale current is held as a voltage component by the drive current control means, and the current value of the light emission drive current and the supply state thereof are controlled based on the voltage component, whereby the light emitting element is The light emission operation is continuously performed at a predetermined luminance gradation.

  Therefore, in the drive current control means, a function (current / voltage conversion function) for converting the current level of the gradation current corresponding to the display data supplied to each display pixel into a voltage level, and a predetermined value based on the voltage level Since both the function of supplying a light emission drive current having a current value to the light emitting element (light emission drive function) is realized, the drive current control means is constituted by, for example, a single active element (thin film transistor). Therefore, there is an advantage that the influence on the light emission drive current can be suppressed by the variation in the operation characteristics between the plurality of thin film transistors as shown in FIG.

JP 2002-156923 A (pages 3 to 4, FIGS. 1 and 2)

However, the light emission drive circuit employing the current application method as described above has the following problems.
In other words, in the current designation type light emission driving circuit, when the gradation current based on the display data having the lowest or relatively low luminance gradation is written to each display pixel (at the time of low gradation display), the luminance gradation of the display data is displayed. It is necessary to supply a signal current having a small current value corresponding to 1 to each display pixel.

  Here, the operation of writing the display data (gradation current) to each display pixel is performed by applying a parasitic component (line parasitic capacitance; due to inter-wiring capacitance, storage capacitance provided in each display pixel, etc.) parasitic to the data line. This corresponds to charging to a predetermined voltage. Since this line parasitic capacitance is a capacitance component added to the data line, it is the same at any position (display pixel) on the data line and supplies a gradation current based on the same luminance gradation. In this case, substantially the same writing time is required.

  Therefore, for example, when the number of scanning lines increases due to an increase in the size or definition of the display panel, the selection period of each scanning line (display pixel in each row) is set to be relatively short. The display data (gradation current) writing time cannot be set (ensured) long enough to sufficiently charge the line parasitic capacitance. As a result, insufficient writing of display data occurs in each display pixel, and the current value of the light emission drive current supplied to the light emitting element (organic EL element) is compared with the gradation current (writing current) at the time of writing. Therefore, the light emitting operation cannot be performed with an appropriate luminance gradation according to the display data, and the display image quality is deteriorated. It should be noted that detailed simulation results for this problem will be described in detail in “Best Mode for Carrying Out the Invention” to be described later for convenience of explanation.

  Therefore, in view of the above-described problems, the present invention supplies a gradation current corresponding to display data to each display pixel constituting the display panel to perform a light emission operation at a predetermined luminance gradation, thereby controlling the current application method. In the display device adopting the method, the display data (grayscale current) is not written insufficiently due to the capacitance component parasitic on the data line, and the light emitting element is operated to emit light at an appropriate luminance gradation, thereby improving the display image quality. It is an object of the present invention to provide a display drive device, a display device, and a drive control method thereof that can be realized.

According to a first aspect of the present invention, there are provided a plurality of display pixels each including a plurality of signal lines and a plurality of scanning lines orthogonal to each other and a current-controlled light emitting element disposed in the vicinity of an intersection of the signal lines and the scanning lines. A gradation current corresponding to a luminance gradation of display data composed of a plurality of bits of digital signals is supplied to each display pixel of the display panel including the plurality of bits through the signal lines, and the gradation current causes the in the display driving device for light-emitting operation of each of light emitting elements by the light emission driving current supplied to the light emitting element based on the amount of charge written in the display pixels, the input number greater than or equal to the number of bits of the display data A number of bits, a plurality of drive gradation values corresponding to the number of input bits, and conversion so that a luminance gradation value of the display data is assigned to one of the plurality of drive gradation values The value of the gradation current is set to a value proportional to the respective drive gradation value, said drive gradation values assigned to the luminance gradation, said assigned to the luminance gradation of the display data and the A change characteristic of the current value of the light emission drive current supplied to the light emitting element according to the gray scale current corresponding to the drive gray scale value with respect to a change in the value of the luminance gray scale is set to a value that approximates linearity . A gradation conversion means is provided.

According to a second aspect of the present invention, in the display drive device according to the first aspect, the gradation converting means is an active element provided in at least the display pixel and related to the supply of the light emission drive current to the light emitting element. A correspondence relationship for converting each gradation value of the luminance gradation of the display data into the driving gradation value is set based on element characteristics.

According to a third aspect of the present invention, in the display driving device according to the first or second aspect , the number of input bits of the gradation converting means is the same as the number of bits of the display data, and the luminance gradation of the display data Means for converting each gradation value into a specific driving gradation value selected from the same number of driving gradation values as the number of gradations.
According to a fourth aspect of the present invention, in the display driving device according to the third aspect , the display driving device corresponds to the gradation corresponding to the number of driving gradation values equal to the number of gradations of the luminance gradation of the display data. Signal driving means for generating a current and supplying the current to each signal line is provided.

According to a fifth aspect of the present invention, in the display driving device according to the first or second aspect , the number of input bits of the gradation converting means is larger than the number of bits of the display data, and the luminance gradation of the display data is Means for converting each gradation value into the driving gradation value of the same number as the gradation number selected from the driving gradation values larger than the gradation number; .

According to a sixth aspect of the present invention, in the display drive device according to the fifth aspect , the display drive device corresponds to the drive gradation value corresponding to a number greater than the number of gradation levels of the luminance gradation of the display data. Signal driving means for generating a gradation current and supplying it to each of the signal lines is provided.
According to a seventh aspect of the present invention, in the display drive device according to the third or fifth aspect , the gradation converting means is constituted by a logic gate circuit.

According to an eighth aspect of the present invention, in the display driving device according to the third or fifth aspect , the gradation converting means associates the gradation value of the luminance gradation of the display data with the driving gradation value. A tone conversion table is provided, and means for determining the drive tone value uniquely by referring to the tone conversion table is provided.
According to a ninth aspect of the present invention, in the display driving device according to the eighth aspect , the gradation conversion table can rewrite a correspondence relationship between the gradation value of the luminance gradation of the display data and the driving gradation value. It is configured.

According to a tenth aspect of the present invention, in the display driving device according to the fourth or sixth aspect , the signal driving means has a current larger than the light emission driving current supplied to the light emitting element based on the driving gradation value. The gradation current having a value is generated.
According to an eleventh aspect of the present invention, in the display driving device according to the tenth aspect , the signal driving means supplies the light emitting element with a current value of the gradation current based on the driving gradation value. Means is provided for setting the current value to be a predetermined coefficient multiple of the current value.

According to a twelfth aspect of the present invention, there is provided a display panel in which a plurality of display pixels each including a current control type light emitting element are arranged in the vicinity of intersections of a plurality of signal lines and a plurality of scanning lines orthogonal to each other. Light emission based on the amount of charge written to the display pixel by supplying a gradation current corresponding to the luminance gradation of display data made up of a plurality of bits of digital data to each of the plurality of display pixels via a line In a display device that supplies a driving current to the light emitting element to perform a light emission operation and displays desired image information on the display panel, at least sequentially applying a scanning signal to the plurality of scanning lines of the display panel, has a scanning driving means for sequentially set to the selected state display pixels, the number of input bits having greater than or equal to the number of bits of the display data, the number of input bits A plurality of corresponding drive gradation values, and converting the brightness gradation value of the display data so as to be assigned to any one of the plurality of drive gradation values. is set to a value proportional to the tone value, the drive gradation values assigned to the luminance gradation is the gradation current corresponding to the drive gradation values assigned to the luminance gradation of the display data Accordingly, a gradation conversion means that is set to a value that brings the change characteristic of the current value of the light emission driving current supplied to the light emitting element with respect to a change in the value of the luminance gradation close to linear , and the drive gradation value Based on the display pixel set in the selected state by the scan driving means by generating the gradation current having a current value larger than the light emission driving current supplied to the light emitting element. Signal driving means for supplying gradation current; Characterized in that it comprises a.

According to a thirteenth aspect of the present invention, in the display device according to the twelfth aspect , the number of input bits of the gradation converting means is the same as the number of bits of the display data, and each gradation of the luminance gradation of the display data Means is provided for converting a value into a specific driving gradation value selected from the same number of driving gradation values as the number of gradations.
According to a fourteenth aspect of the present invention, in the display device according to the thirteenth aspect , the signal driving means corresponds to the gradation current corresponding to the same number of driving gradation values as the number of gradations of luminance gradations of the display data. Is generated and supplied to each of the signal lines.

According to a fifteenth aspect of the present invention, in the display device according to the twelfth aspect , the number of input bits of the gradation converting means is larger than the number of bits of the display data, and the gradation values of the luminance gradation of the display data are set. And a means for converting the driving gradation values to the same number as the number of gradations selected from the driving gradation values larger than the number of gradations.
According to a sixteenth aspect of the present invention, in the display device according to the fifteenth aspect , the signal driving means corresponds to the number of the driving gradation values corresponding to the number of gradations larger than the number of gradations of the luminance gradation of the display data. Means for generating a regulated current and supplying it to each of the signal lines is provided.

According to a seventeenth aspect of the present invention, in the display device according to any one of the twelfth to sixteenth aspects, the display pixel includes at least a storage capacitor that stores a charge based on the gradation current as a voltage component. And a drive current control means for causing the light emission drive current to flow to the light emitting element based on the voltage component held in the charge holding means, and the gradation conversion means includes at least The drive current control means is configured, and based on the element characteristics of the active element related to the supply of the light emission drive current to the light emitting element, each gradation value of the luminance gradation of the display data is set as the drive gradation value. A correspondence relationship to be converted is set.
According to an eighteenth aspect of the present invention, in the display device according to any one of the twelfth to seventeenth aspects, the light emitting element is an organic electroluminescent element.

According to a nineteenth aspect of the present invention, there is provided a display panel in which a plurality of display pixels each including a current control type light emitting element are arranged in the vicinity of intersections of a plurality of signal lines and a plurality of scanning lines orthogonal to each other, Light emission based on the amount of charge written to the display pixel by supplying a gradation current corresponding to the luminance gradation of display data made up of a plurality of bits of digital data to each of the plurality of display pixels via a line In a drive control method for a display device in which a drive current is supplied to the light emitting element to perform light emission operation and desired image information is displayed on the display panel, at least a luminance gradation value of the display data is set to the display data. Conversion to assign to any of a plurality of drive gradation values corresponding to the number of input bits equal to or greater than the number of bits, and the value of the gradation current is converted to each of the drive gradation values Set proportional value, the light emission of the drive gradation value assigned to the luminance gradation in accordance with the gradation current corresponding to the drive gradation values assigned to the luminance gradation of the display data Setting a change characteristic of the current value of the light emission drive current supplied to the element to a value that approximates linearity with respect to a change in the value of the luminance gradation; and supplying the light emission element based on the drive gradation value Generating the gradation current having a current value larger than the light emission driving current and supplying the gradation current to the display pixel.

According to a twentieth aspect of the present invention, in the display device drive control method according to the nineteenth aspect , the number of input bits is the same as the number of bits of the display data, and each gradation value of the luminance gradation of the display data is set as the gradation value. The step of converting into drive gradation values converts each gradation value of the luminance gradation of the display data into a specific drive gradation value selected from the same number of drive gradation values as the number of gradations. It is characterized by doing.

The invention according to claim 21 is the drive control method for a display device according to claim 19 , wherein the number of input bits is larger than the number of bits of the display data, and each gradation value of the luminance gradation of the display data is set to the drive level. The step of converting to a tone value includes selecting each of the gradation values of the luminance gradation of the display data from the drive gradation values having a number greater than the number of gradations, and the same number of the drivings as the number of gradations. It is characterized by converting to a gradation value.

That is, the display drive device, the display device, and the drive control method thereof according to the present invention provide current control for performing light emission operation at a predetermined luminance gradation in accordance with the current value of the light emission drive current supplied, such as an organic EL element. A plurality of display pixels can be two-dimensionally provided by supplying a gradation current corresponding to display data composed of a plurality of bits of digital data to a display pixel including a light emitting element of a type to emit light at a predetermined light emission luminance. In a display device that displays desired image information on an arrayed display panel, a light emitting element is provided in a display pixel to which a gradation current according to display data is supplied in a display data writing operation to each display pixel. In accordance with the gradation characteristics defined based on the element characteristics of the active elements (transistor elements) involved in the supply of the light emission drive current to the display, the gradation conversion means (signal correction circuit) Tone values of Dokaicho is configured to convert (luminance gradation value) to a specific drive gradation value (gradation conversion processing). Specifically, the number of input bits is equal to or greater than the number of bits of the display data , and there are a plurality of drive gradation values corresponding to the number of input bits, and the luminance gradation of the display data is The value is converted to be assigned to one of a plurality of drive gradation values, the value of the gradation current is set to a value proportional to each drive gradation value, and the drive gradation value assigned to the luminance gradation is The change characteristic of the current value of the light emission drive current supplied to the light emitting element corresponding to the luminance gradation of the display data with respect to the change in the luminance gradation value is set to a value that approximates linearity .

  Further, the gradation generated based on the drive gradation value by the signal driving means (data driver) according to the current characteristic defined based on the capacitance component parasitic on the signal line provided in the display panel. The current is set so as to be larger than the current value of the light emission drive current supplied to the light emitting element of each display pixel corresponding to the luminance gradation of the display data (current setting process), The display pixel is supplied to the display pixel through a signal line.

  According to this, non-linearity of gradation characteristics caused by transistor characteristics of transistor elements constituting display pixels (light emission drive circuits) arranged in the display panel is suppressed, and display with respect to luminance gradation of display data is performed. The light emission luminance of the pixel (light emitting element) can be controlled to have linearity, and the display data writing shortage caused by the parasitic capacitance added to the data line provided in the display panel is suppressed. A light emission driving current having a current value corresponding to the luminance gradation of the display data can be supplied to the light emitting element.

  Therefore, even if the number of scanning lines is increased due to an increase in the size or definition of the display panel and the selection period of each scanning line (display pixel in each row) is set relatively short, the display data Therefore, the light emitting element can be operated to emit light (gray scale display) with a light emission luminance appropriately corresponding to the above, and display image quality of image information can be improved.

Here, in the gradation conversion processing executed by the gradation conversion means, the number of input bits of the gradation conversion means is the same as the number of bits of the display data, and each gradation value of the luminance gradation of the display data is expressed as It may be converted to a specific drive gradation value selected from the same number of drive gradation values as the number of gradations and smaller than the number of luminance gradations of the display data, or gradation conversion. The number of input bits of the means is larger than the number of bits of display data and the number of drive gradation values selected from the number of gradations of luminance gradation of the display data is set to the same number of drive gradation values as the number of gradations. You may convert.

  In the former gradation conversion processing, a data driver that generates gradation currents corresponding to the number of drive gradation values (that is, the number of bits) equal to the number of luminance gradations of the display data and supplies it to each signal line Therefore, the display device according to the present invention can be configured at low cost. In the latter gradation conversion process, a data driver corresponding to a driving gradation value (number of bits) larger than the number of luminance gradations of the display data is applied, and the gradation of the driving gradation is applied. Since the number can be the same as the number of luminance gradations of the display data, it is possible to prevent a decrease in the number of gradations in the gradation conversion process and suppress deterioration in display image quality.

  Further, as the gradation conversion means for executing the gradation conversion processing, for example, a logic gate circuit corresponding to the correspondence relationship (gradation conversion pattern) between the gradation value of the luminance gradation of the display data and the drive gradation value, By applying the gradation conversion table (table data), the current value of the light emission driving current supplied to the light emitting element is linear with respect to the current value of the gradation current supplied to the display pixel based on the driving gradation value. Therefore, the process of converting each gradation value of the luminance gradation of the display data into a specific driving gradation value can be executed simply and uniquely.

  Therefore, when a logic gate circuit is applied as the gradation converting means, the luminance gradation value of the display data is fixed to a predetermined driving gradation value according to the gradation conversion pattern while reducing the circuit scale. When the gradation conversion table is applied as the gradation conversion means, the gradation conversion table is stored in a rewritable storage means (table memory), and the gradation conversion pattern is stored in the gradation conversion table. By appropriately rewriting, it is possible to realize gradation conversion processing according to the gradation characteristics of the display panel without changing the configuration of the gradation conversion means.

Hereinafter, a display drive device, a display device, and a drive control method thereof according to the present invention will be described in detail with reference to embodiments.
<Display device>
First, a schematic configuration of a display device to which the display driving device according to the present invention can be applied will be described with reference to the drawings.
FIG. 1 is a schematic block diagram illustrating a basic configuration of a display device according to the present invention, and FIG. 2 is a schematic configuration diagram illustrating a main configuration of the display device according to the present invention. Here, a configuration equivalent to the above-described conventional technique (FIG. 22) will be described with the same or equivalent reference numerals.

  As shown in FIG. 1 and FIG. 2, the display device 100 according to the present invention generally includes intersections of a plurality of scanning lines SL and a plurality of data lines (signal lines) DL arranged so as to be orthogonal to each other. In the vicinity, for example, a display panel 110 in which a plurality of display pixels EM composed of a light emission drive circuit and a current control type light emitting element (organic EL element), which will be described later, are arranged in a matrix, and a scanning line SL of the display panel 110 A scanning driver (scanning driving means) 120 that is connected and sequentially applies the scanning signal Vsel to each scanning line SL at a predetermined timing to set the display pixel EM for each row to a selected state, and a display signal generation circuit to be described later 160 is a signal correction circuit that converts the luminance gradation of the display data supplied from 160 to a specific gradation (driving gradation value) corresponding to the gradation characteristics of the display panel 110. ) 140 and the display line 110 connected to the data line DL of the display panel 110, and the display data converted by the signal correction circuit 140 described above (hereinafter referred to as “corrected display data”) are taken in, and each data line is read at a predetermined timing. Based on a timing signal supplied from a data driver (signal driving means) 130 for supplying gradation current Ipix corresponding to display data after correction to DL and a display signal generation circuit 160 described later, at least the scanning driver 120 and data Based on a system controller 150 that generates and outputs a scanning control signal, a data control signal, and a correction control signal for controlling the operating state of the driver 130 and the signal correction circuit 140, and a video signal supplied from the outside of the display device 100, for example. Display data (luminance gradation data) is generated in the signal correction circuit 140. A display signal generation circuit that extracts or generates a timing signal (system clock or the like) for displaying predetermined image information on the display panel 110 based on the corrected display data and supplies the timing signal to the system controller 150 160.

Hereafter, each said structure is demonstrated concretely.
(Display panel 110)
The display pixels EM arranged in the display panel 110 shown in FIG. 2 are supplied from the data driver 130 to the data line DL based on the timing of applying the scanning signal Vsel from the scanning driver 120 to the scanning line SL, as will be described later. The gradation current Ipix is taken in, a writing operation for holding a voltage component corresponding to the gradation current Ipix, and a light emission driving current based on the voltage component is supplied to the light emitting element to emit light at a predetermined luminance gradation And a light emitting operation to be selectively executed.

  That is, the display pixel EM (light emission drive circuit) applied to the present invention has a gradation in a selection state (selection period) set by applying a scanning signal Vsel of a selection level (for example, high level). When the current Ipix is supplied and display data is written (writing operation), the supply of the light emission drive current to the light emitting element is cut off and the light emission state is turned off, while the scanning signal of the non-selection level (for example, low level) In a non-selection state (non-selection period) set by applying Vsel, a light emission drive current based on the gradation current Ipix written by the writing operation is supplied to the light emitting element, and the light emitting element Light is emitted at a predetermined luminance gradation (light emission operation). A specific circuit example and circuit operation of the display pixel EM (light emission drive circuit) applied to the display panel according to the present invention will be described in detail later.

(Scanning driver 120)
The scan driver 120 sequentially applies a selection level (for example, high level) scan signal Vsel to each of the scan lines SL based on a scan control signal supplied from the system controller 150, thereby displaying the display pixels EM for each row. Is set to the selected state, and based on display data (strictly, corrected display data) supplied by the data driver 130 via each data line DL during the period (selection period) set in the selected state. The gradation current Ipix is controlled to be written in each display pixel EM.

  Specifically, as shown in FIG. 2, the scan driver 120 includes a plurality of stages of shift blocks SB1, SB2, SB3,... Each including a shift register and a buffer corresponding to each scan line SL. Based on the scanning clock signal SCK supplied from the system controller 150 as a scanning control signal, a shift signal generated while sequentially shifting the scanning start signal SST from the upper side to the lower side of the display panel 110 is transferred to a predetermined voltage via a buffer. The signal is converted to a level (high level) and applied to each scanning line SL as a scanning signal Vsel.

(Data driver 130)
FIG. 3 is a schematic block diagram showing an example of a data driver applicable to the display device according to the present invention, and FIG. 4 is a voltage-current conversion / current supply circuit applicable to the data driver of the display device according to the present invention. It is a circuit block diagram which shows an example.

  Based on the data control signal supplied from the system controller 150, the data driver 130 is supplied from the display signal generation circuit 150, which will be described later, and is converted by the signal correction circuit 140. (Corrected display data) is sequentially fetched and held at a predetermined timing, and a gradation current Ipix having a current value corresponding to the gradation value of the corrected display data is generated and set for each scanning line SL. Is supplied to each data line DL within a selected period.

  Specifically, as shown in FIG. 3, the data driver 130 sequentially outputs shift signals based on data control signals (shift clock signal CLK, sampling start signal STR) supplied from the system controller 150. Shift register circuit 131 and a data register circuit for sequentially fetching corrected display data D0 to Dm for one row supplied from the display signal generation circuit 160 via the signal correction circuit 140 based on the input timing of the shift signal 132, a data latch circuit 133 that holds corrected display data D0 to Dm for one row fetched by the data register circuit 132 based on a data control signal (data latch signal STB), and power supply not shown Based on the gradation reference voltages V0 to Vp supplied from the means. D / A converter (digital-analog converter) 134 for converting the corrected display data (drive gradation values) D0 to Dm into a predetermined analog signal voltage (gradation voltage Vpix), and conversion into an analog signal voltage The gradation current Ipix having a current value corresponding to the displayed display data (corrected display data) is generated, and at the timing based on the data control signal (output enable signal OE) supplied from the system controller 150, A voltage-current conversion / current supply circuit 135 that supplies the regulated current Ipix to the respective display pixels EM all at once via the data line DL is configured.

  As the voltage-current conversion / current supply circuit 135 applicable to the data driver 130, for example, as shown in FIG. 4, one input terminal (negative input (−)) has a reverse polarity via an input resistor R. Grayscale voltage (−Vpix) is input, and the other input terminal (positive input (+)) is supplied with a reference voltage (ground potential) via the input resistor R, and the output terminal is connected to the feedback resistor R. The potential of the operational amplifier OP1 connected to the input terminal (−) and the contact NA provided to the output terminal of the operational amplifier OP1 via the output resistor R is input to one input terminal (+), and the output terminal An operational amplifier OP2 connected to the other input terminal (−) and connected to the input terminal (+) of the operational amplifier OP1 via the output resistor R, and connected between the contact NA and the data line DL, and an output enable. Signal OE It has a switching means SW to ON / OFF operation based on a circuit configuration with a.

  According to the circuit configuration in which such a voltage / current conversion / current supply circuit 135 is provided for each data line, −Ipix = (− Vpix) with respect to the input negative gradation voltage (−Vpix). Negative gradation current composed of −Vpix) / R is generated, and the supply state to each data line DL is controlled based on the output enable signal OE. In the circuit configuration shown in FIG. 4, since the generated gradation current Ipix has a negative polarity, an operation state in which the current is drawn from the data line (display pixel) side toward the data driver 130 is controlled.

  Here, the gradation current Ipix generated by the voltage-current conversion / current supply circuit 135 can be set to an arbitrary current value by appropriately setting the value of the resistor R. In this embodiment, the gradation current Ipix will be described later. As described above, it is possible to suppress insufficient writing of display data due to a parasitic component (mainly a sum of wiring capacitances, retention capacitors provided in each display pixel, etc.) parasitic to the data lines DL provided in the display panel 110. As described above, the current value of the gradation current Ipix is larger than the current value of the light emission drive current supplied to the light emitting element of each display pixel EM (for example, a value obtained by multiplying the value by a predetermined coefficient α (α> 1)). ) Set (current setting process). The current setting process in the data driver 130 (voltage / current conversion / current supply circuit 135) will be described in detail later.

(Signal correction circuit 140)
The signal correction circuit 140 emits light to the light emitting element at least in each display pixel EM (light emission driving circuit) arranged in the display panel 110 with respect to each luminance value of the display data supplied from the display signal generation circuit 160. Based on the element characteristics of an active element (thin film transistor serving as drive current control means) that controls the supply state of the drive current, a process of converting into a predetermined number of gradation values (drive gradation values) is performed.

  Here, the relationship between the current value of the gradation current Ipix supplied from the data driver 130 to each display pixel EM via the data line DL and the current value of the light emission drive current supplied to the light emitting element in each display pixel EM. As described later, the inventors of the present application have found that non-linear characteristics are exhibited due to the element characteristics of the active elements involved in the supply of the light emission driving current.

  Therefore, in consideration of the capacitance component parasitic on the data line DL by the data driver 130 described above, the current value of the gradation current Ipix supplied to each display pixel is determined by the light emission driving current flowing in the light emitting element of the display pixel. Is set to a large value, the relationship (gradation characteristics) of the light emission luminance (output gradation) of the light emitting element with respect to the luminance gradation (input gradation) of the display data exhibits nonlinearity, thereby realizing appropriate gradation display. I can't.

  Therefore, in the present invention, in the signal correction circuit 140, each gradation value of the luminance gradation of the display data supplied from the display signal generation circuit 160 is changed to the current of the light emission driving current supplied to the light emitting element for each gradation value. A gradation conversion process for converting to a gradation value corresponding to the gradation current Ipix in which the difference in values is approximately equal (that is, the difference in display gradation defined by the light emission luminance of the light emitting element is substantially uniform). Execute. That is, in consideration of the element characteristics of the active elements related to the supply of the light emission driving current in each display pixel in advance, the gradation characteristics of the display panel (the relationship between the luminance gradation and the light emission luminance) have linearity. Each gradation value of the luminance gradation is converted into a driving gradation value.

  Although a specific configuration example of the signal correction circuit 140 will be described in detail later, for example, a logic gate circuit that converts a gradation value fixedly based on the previously determined nonlinearity of the gradation characteristic, It is possible to apply a method of converting gradation values with reference to table data (gradation conversion table) storing gradation conversion patterns (correspondence between input gradations and output gradations).

(System controller 150)
The system controller 150 outputs a scanning control signal, a data control signal, and a correction control signal for controlling the operation state to the scanning driver 120, the data driver 130, and the signal correction circuit 140 described above, whereby each driver is set in a predetermined manner. The display data (corrected display data) generated by the display signal generation circuit 160 and converted by the signal correction circuit 140 is generated by generating the scanning signal Vsel and the gradation current Ipix by outputting at the timing and outputting it to the display panel 110. Control is performed to display the predetermined image information by writing to each display pixel EM and causing it to emit light.

(Display signal generation circuit 160)
For example, the display signal generation circuit 160 extracts a luminance gradation signal component from a video signal supplied from the outside of the display device 100 and corrects the signal as display data (luminance gradation data) for each row of the display panel 110. The data is supplied to the data driver 130 via the circuit 140. Here, when the video signal includes a timing signal component that defines the display timing of image information, for example, a television broadcast signal (composite video signal), the display signal generation circuit 160 displays the luminance gradation. In addition to the function of extracting the signal component, it may have a function of extracting the timing signal component and supplying it to the system controller 150. In this case, the system controller 150 scans signals and data control signals supplied to the scan driver 120, the data driver 130, and the signal correction circuit 140 based on the timing signal supplied from the display signal generation circuit 160. Then, a correction control signal is generated.

<Specific examples of display pixels>
Next, specific circuit examples of the display pixels arranged in the above-described display panel will be described with reference to the drawings.
FIG. 5 is a circuit configuration diagram illustrating a specific circuit example of a display pixel (light emission drive circuit) applicable to the display device according to the present invention, and FIG. 6 illustrates an operation state of the light emission drive circuit according to the present embodiment. It is a conceptual diagram. FIG. 7 is a timing chart showing the basic operation of the display pixel to which the light emission driving circuit according to this embodiment is applied. FIG. 8 is a schematic block diagram illustrating a configuration example of a display device to which the display pixel according to the present embodiment is applied.

  As shown in FIG. 5, the display pixel EM according to the present embodiment sets the display pixel EM to a selected state based on the scanning signal Vsel applied from the scan driver 120 described above, and the data driver in the selected state. The light emission driving circuit DC that takes in the gradation current Ipix (based on the corrected display data) supplied from 130 and supplies the light emission driving current corresponding to the gradation current Ipix to the light emitting element, and the light emission driving circuit DC And a current-controlled light emitting element such as an organic EL element OEL that emits light at a predetermined luminance gradation based on the light emission driving current.

  Specifically, in the light emission drive circuit DC, for example, as shown in FIG. 5, the gate terminal is connected to the scanning line SL, the source terminal is connected to the power supply line VL (power supply voltage Vsc), and the drain terminal is connected to the contact N1. N channel type thin film transistor Tr11, n channel type thin film transistor Tr12 whose gate terminal is connected to scan line SL, source terminal and drain terminal connected to data line DL and contact N12, respectively, and gate terminal to contact N11, source An n-channel thin film transistor (drive current control means) Tr13 having a terminal and a drain terminal connected to the power supply line VL and the contact N12, respectively, and a capacitor (charge holding means) Cs connected between the contact N11 and the contact N12. The anode terminal of the organic EL element OEL is connected to the contact N12, the cathode Terminals are respectively connected to the ground potential. Here, the capacitor Cs may be a parasitic capacitance formed between the gate and the source of the thin film transistor Tr13.

  The light emission drive control of the light emitting element (organic EL element OEL) in the light emission drive circuit DC having such a configuration is performed, for example, within one scan period Tsc with one scan period Tsc as one cycle, as shown in FIG. The display pixel EM connected to the scanning line SL is selected, and the gradation current Ipix corresponding to the corrected display data is written and held as a voltage component (writing operation period) Tse, and the selection period Tse A non-selection period (light emission operation period) Tnse in which a light emission drive current corresponding to the corrected display data is supplied to the organic EL element OEL based on the written and held voltage components and the light emission operation is performed at a predetermined luminance gradation. Are set (Tsc = Tse + Tnse). Here, the selection period Tse set for each scanning line SL to which the display pixels EM of each row are connected is set so that there is no time overlap.

(Selection period)
That is, in the display pixel selection period Tse, as shown in FIG. 7, first, the high-level scanning signal Vsel is applied from the scanning driver 120 to the specific scanning line SL to select the display pixel in the row. At the same time, the low level power supply voltage Vsc is applied to the power supply line VL of the display pixels in the row. In synchronization with this timing, a negative gray-scale current (-Ipix) having a current value corresponding to the display pixel in the row is supplied from the data driver 130 to each data line DL.

  As a result, the thin film transistors Tr11 and Tr12 constituting the light emission drive circuit DC are turned on, and the low-level power supply voltage Vsc is applied to the contact N11 (that is, the gate terminal of the thin film transistor Tr13 and one end of the capacitor Cs), and the data By performing an operation of drawing a negative gradation current (-Ipix) through the line DL, a voltage level lower than the low-level power supply voltage Vsc becomes the contact N12 (that is, the source terminal and the capacitor of the thin film transistor Tr13). (The other end of Cs).

  Thus, the potential difference is generated between the contacts N11 and N12 (between the gate and the source of the thin film transistor Tr13), so that the thin film transistor Tr13 is turned on, and as shown in FIG. 6A, the thin film transistor Tr13, A write current Ia corresponding to the current value of the gradation current Ipix flows through the data driver 130 via the contact N12, the thin film transistor Tr12, and the data line DL.

  At this time, a charge corresponding to a potential difference generated between the contacts N11 and N12 (between the gate and the source of the thin film transistor Tr13) is accumulated in the capacitor Cs and held (charged) as a voltage component. Further, the power supply line VL is applied with a power supply voltage Vsc having a voltage level equal to or lower than the ground potential, and the write current Ia is controlled to flow in the direction of the data line DL, so that the organic EL element OEL Since the potential applied to the anode terminal (contact N12) is lower than the potential of the cathode terminal (ground potential), and a reverse bias voltage is applied to the organic EL element OEL, the organic EL element OEL is driven. No current flows and no light emission operation is performed.

(Non-selection period)
Next, in the non-selection period Tnse after the end of the selection period Tse, as shown in FIG. 7, the low-level scan signal Vsel is applied from the scan driver 120 to the specific scan line SL, and the display pixels in the row are displayed. Is set to a non-selected state, and a high-level power supply voltage Vsc is applied to the power supply line VL of the display pixel in the row. In synchronization with this timing, the operation of drawing the gradation current Ipix by the data driver 130 is stopped.

  As a result, the thin film transistors Tr11 and Tr12 constituting the light emission drive circuit DC are turned off, and the application of the power supply voltage Vsc to the contact N11 (that is, the gate terminal of the thin film transistor Tr13 and one end of the capacitor Cs) is cut off. Since the application of the voltage level due to the pull-in operation of the gradation current Ipix by the data driver 130 to N12 (that is, the source terminal of the thin film transistor Tr13 and the other end of the capacitor Cs) is cut off, the capacitor Cs The electric charge accumulated in is held.

  In this manner, the capacitor Cs holds the charging voltage during the writing operation, whereby the potential difference between the contacts N11 and N12 (between the gate and the source of the thin film transistor Tr13) is held, and the thin film transistor Tr13 is turned on. To maintain. Further, since the power supply voltage Vsc having a voltage level higher than the ground potential is applied to the power supply line VL, the potential applied to the anode terminal (contact N2) of the organic EL element OEL is the potential of the cathode terminal (ground potential). ).

  Therefore, as shown in FIG. 6B, a predetermined light emission drive current Ib flows in the forward bias direction from the power supply line VL to the organic EL element OEL via the thin film transistor Tr13 and the contact N12, and the organic EL element OEL emits light. . Here, the potential difference (charge voltage) based on the charge accumulated by the capacitor Cs corresponds to the potential difference when the write current Ia corresponding to the gradation current Ipix is caused to flow down in the thin film transistor Tr13, and thus flows down to the organic EL element OEL. The light emission drive current Ib to be performed has a current value equivalent to the write current Ia. Thus, in the non-selection period Tnse after the selection period Tse, the light emission drive current Ib is generated via the thin film transistor Tr13 based on the voltage component corresponding to the display data (gradation current Ipix) written in the selection period Tse. The organic EL element OEL continues to operate to emit light at a luminance gradation corresponding to the display data.

Then, by sequentially repeating the above-described series of operations for all the scanning lines SL constituting the display panel 110, display data for one screen of the display panel is written, light is emitted at a predetermined luminance gradation, Desired image information is displayed.
Here, the thin film transistors Tr11 to Tr13 applied to the light emission drive circuit DC according to the present embodiment are not particularly limited. However, by configuring all the thin film transistors Tr11 to Tr13 with n channel thin film transistors, an n channel can be obtained. The type amorphous silicon TFT can be satisfactorily applied. In this case, an already established amorphous silicon manufacturing technique can be applied to manufacture a light emission drive circuit with stable operating characteristics at a relatively low cost.

  Further, as a configuration for applying a predetermined power supply voltage Vsc to the power supply line VL in the light emission drive circuit DC according to the present embodiment, for example, as shown in FIG. 8, in addition to the configuration of the display device shown in FIG. A power supply driver 170 connected to a plurality of power supply lines VL arranged in parallel to each scan line SL of the panel 110 is provided, and is output from the scan driver 120 based on a power supply control signal supplied from the system controller 150. At a timing synchronized with the scanning signal Vsel (see FIG. 7), a power supply voltage Vsc having a predetermined voltage value from the power supply driver 170 is applied to the row to which the scanning signal Vsel is applied by the scanning driver 120 (display pixels set in a selected state). EM) can be satisfactorily applied to the configuration applied to the power supply line VL.

  Note that the display pixel described above includes three thin film transistors as the light emission driving circuit, generates a negative gradation current by the data driver, and then from the display pixel (light emission driving circuit) to the data driver direction via the data line. Although the circuit configuration corresponding to the current application method in which the gradation current is drawn is shown in FIG. 1, the present invention is not limited to this embodiment. That is, at least a display device including a light emission drive circuit corresponding to a current application method, and provided with drive current control means (corresponding to the thin film transistors Tr11 and Tr13) for controlling the supply of the light emission drive current to the light emitting element, The drive current control means holds the gradation current according to the display data (corrected display data) (as the voltage component in the charge holding means), supplies the light emission drive current based on the gradation current, and Any circuit having another circuit configuration may be used as long as the light emission operation is performed with a predetermined luminance gradation. For example, a circuit configuration including four thin film transistors may be used. Furthermore, a circuit configuration corresponding to a mode in which a positive gray scale current is generated by the data driver 130 and the gray scale current is supplied from the data driver 130 to the display pixel (light emission drive circuit) via the data line DL. You may have.

  In the above-described embodiments, the configuration in which the organic EL element is applied as the light emitting element constituting the display pixel is shown. However, the display device according to the present invention is not limited to this, and the supplied light emission driving current is used. In addition to the organic EL element described above, for example, a light-emitting diode or other light-emitting element is applied as long as the current-controlled light-emitting element emits light with a predetermined luminance gradation according to the current value. Also good.

<Display device drive control method>
Next, a drive control method in the display device according to the present invention will be described.
Here, first, the insufficient writing of display data (gradation current) in each display pixel and the relationship between the write current (gradation current) and the light emission drive current (the relationship between the output gradation and the input gradation) will be described. Thereafter, a drive control method (gradation conversion process, current setting process) of the display device according to the present invention for solving such a problem will be described in detail.

(Examine issues)
FIG. 9 is a simulation result showing the relationship (current characteristics) between the gradation current (input current) based on the display data supplied to the display panel (display pixel) and the light emission drive current (output current) supplied to the light emitting element. FIG. 6 is a characteristic diagram showing a correspondence relationship (gradation characteristics) between the luminance gradation (input gradation) of display data and the light emission luminance (output gradation) of the light emitting element based on the simulation result.

Here, as shown in Table 1, the simulation result shown in FIG. 9 has a screen size of 30 inches WXGA, the number of horizontal pixels 1280, the number of vertical pixels 2304, the wiring width of the data line 6 μm, the parasitic of the data line. Using a display panel having a capacitance (wiring capacitance) of 89.1 pF, a pixel selection time of 6 μsec, a maximum gradation current value of 4 μA / pix (4.0E-06A / pix), and an emission luminance of 500 cd / m ² are set. The current value of the light emission drive current (output current) and the light emission luminance (output gradation) when supplying the gradation current (input current) corresponding to each gradation value of the luminance gradation (input gradation) of the display data ) Is calculated. Note that the circuit configuration (see FIG. 5) including the light emission drive circuit and the organic EL element described above is applied to each display pixel arranged in the display panel.

  As shown in FIG. 9A, the organic EL of each display pixel EM with respect to the gradation current Ipix (≈write current Ia; input current) supplied from the data driver 130 to each display pixel EM via the data line DL. The light emission drive current Ib (output current) supplied to the element OEL indicates an ideal writing state in which an output current having a current value equivalent to the input current (having linearity) is supplied. Compared to the current characteristic line Sri (arbitrary output current on the current characteristic line Sri), the current characteristic line Sri is significantly smaller (that is, the write-in shortage state where the light emission drive current Ib is smaller than the gradation current Ipix). A simulation result (current characteristic line Spi) showing a relationship in which the change tendency of the output current with respect to the input current is not uniform (that is, non-linearity in which the difference between the output currents with respect to the input current is not equal) is obtained. .

  Here, the organic EL element (light emitting element) OEL provided in each display pixel EM is a current control type light emitting element in which the light emission luminance (output gradation) with respect to the current value of the light emission drive current Ib (output current) exhibits linearity. Therefore, as shown in FIG. 9B, the current value of the input current shown in FIG. 9A corresponds to the luminance gradation (input gradation) defined by the gradation current Ipix, and the output The current value of the current corresponds to the light emission luminance (output gradation) of the organic EL element OEL. Therefore, the gradation characteristic line Srg indicating the ideal relationship between the output gradation and the input gradation based on the current characteristic line Sri exhibits linearity, and each display pixel EM is based on the current characteristic line Spi. The gradation characteristic line Spg, which is the relationship of the output gradation with respect to the input gradation, shows non-linearity.

  According to such a simulation result, based on the display data generated in the display signal generation circuit 160 shown in the display device 100 described above, the gradation current Ipix having a predetermined current value is applied to each display pixel by the data driver 130. When supplied to EM, if the gradation current Ipix is set to a current value corresponding to the display data itself, insufficient writing as shown in FIG. 9 occurs, and the display data is appropriately handled. The organic EL element OEL cannot be operated to emit light with the light emission brightness and the gradation difference of the light emission brightness in the light emission operation is not uniform with respect to the brightness gradation value of the display data. There is a problem that display quality of information is remarkably deteriorated.

  Therefore, as a result of intensive investigations on such insufficient writing and non-linearity, the present inventors have found that the insufficient writing to the display pixel is parasitic on the data line disposed between the data driver and each display pixel. This is due to the capacitance component (parasitic capacitance), and the non-linearity of the current characteristic and the gradation characteristic is caused by the transistor characteristic of the thin film transistor as the drive current control means constituting the light emission drive circuit provided in each display pixel. A conclusion was reached that this was due.

The details of the study will be described in detail below.
FIG. 10 is a schematic circuit diagram showing an addition circuit (connection) of parasitic capacitance to a display pixel applied to the display device according to the present invention and an equivalent circuit in which the circuit configuration is simplified in order to analyze the simulation result. It is.

  As shown in FIG. 5, the display pixel EM applied to the display device according to the present invention is supplied with a light emission drive circuit DC including three thin film transistors Tr11 to Tr13 and a capacitor Cs, and the light emission drive circuit DC. And an organic EL element OEL that emits light by the light emission drive current Ib.

  Here, as shown in FIG. 10A, the data line DL connected to a specific display pixel EM generally includes an inter-wiring capacitance Cdata-s between the data line DL and the scanning line SL, an organic The capacitance component Cdata-c between the cathode electrode (ground potential) of the EL element OEL, the holding capacitor Cpix (corresponding to the capacitor Cs) provided in the display pixel EM (light emission drive circuit DC), and the gate capacitance of the thin film transistor Tr13 Cin, another display pixel connected to the data line DL, a capacitance component Ct2 caused by an adjacent display pixel, and the like are added as parasitic capacitance. Each of these parasitic capacitances has a large capacitance value related to the occurrence of insufficient writing in the above-described writing operation of the gradation current Ipix (input current Ia) to the display pixel EM.

  A sum of these parasitic capacitances (total capacitance value = Cpix + Cin + Cdata-c + Cdata-s + Ct2)) is set as Cttl, and a predetermined gradation current Ipix is supplied from the data driver 130 to each display pixel EM via the data line DL as a voltage component. Considering the case where the capacitor Cs holds (write operation), as shown by a thick line in FIG. 10A, the thin film transistors Tr12 and Tr13 provided from the data line DL to the light emission drive circuit DC of the display pixel EM are used. Thus, the write current Ia (≈gradation current Ipix) flows through the power supply line VL. Therefore, when the circuit is simplified, the input current Idata (write current) is roughly shown in FIG. The transistor element TrA (corresponding to Ia) is connected to a current path between the current supply source SCi and the ground potential, and the gate and the source are short-circuited (the thin film element described above). To correspond to the transistor Tr 13), the gate of the transistor element TrA - a parasitic capacitance (sum) CTTL connected between the drain can be represented by an equivalent circuit composed of.

  According to such an equivalent circuit, the input current Idata (write current Ia) supplied to the light emission drive circuit DC at the time of the write operation can be expressed as the following equation (11). In the equation (11), Vt is a potential difference generated at both ends of the parasitic capacitance Cttl during the write operation, μe is a dielectric constant of the gate insulating film of the transistor element TrA, and W and L are the respective transistors. The width and length of the gate electrode of the element TrA.

  In this equation (11), when the time change Vt of the potential difference is set as follows when t = 0 and t = ∞, the time change of the current flowing through the transistor element TrA (corresponding to the write current Ia) It can be expressed as in equation (12). Here, in the writing operation, the current level flowing in the current path of the transistor element TrA is converted into the voltage level of the gate-drain of the transistor element TrA and accumulated as a charge in the parasitic capacitance Cttl (voltage component). As)).

  Next, considering the case where the supply of the gradation current Ipix from the data driver 130 to each display pixel EM is cut off, and the organic EL element (light emitting element) OEL connected to the light emission driving circuit DC is operated to emit light, FIG. In FIG. 10A, since the thin film transistor Tr13 and the organic EL element OEL are connected in series between the power supply line VL to which the power supply voltage Vsc is applied and the ground potential, as schematically shown in FIG. The current path of the transistor element TrA and the equivalent circuit in which the organic EL element OEL is connected between the voltage supply source SCv of the power supply voltage Vsc and the ground potential can be expressed.

  In this light emitting operation, although the supply of the input current Idata from the current supply source SCi is interrupted, the potential based on the charge (voltage component) accumulated in the parasitic capacitance Cttl is held at the gate of the transistor element TrA. The transistor element TrA continues to be turned on in a conductive state equivalent to that during the writing operation. As a result, an output current It (corresponding to the light emission drive current Ib) equivalent to the current shown in the equation (12) is supplied to the organic EL element OEL, and the light emission operation is performed at a predetermined luminance gradation.

  Here, according to the above equation (12), the output current It is affected by the parasitic capacitance Cttl added to the data line DL, like the current characteristic line Spi according to the simulation shown in FIG. 9A. , The current value becomes smaller than the input current Idata (that is, smaller than the current characteristic line Sri indicating the ideal writing state), and the transistor of the transistor element TrA for driving current control that constitutes the light emission driving circuit DC Under the influence of the characteristics (element characteristics), it has been found that the changing tendency of the output current It with respect to the input current Idata exhibits nonlinearity.

  Therefore, in the display device according to the present invention, the current value of the input current Idata (that is, the gradation current Ipix supplied from the data driver 130 to the display pixel EM) is calculated based on the above-described examination results, and the luminance of the display data. The current value of the output current It (that is, the light emission driving current Ib supplied to the organic EL element of each display pixel EM) is set to be larger than the current value defined by the gradation (current setting process), and a desired value is obtained. The brightness gradation of the display data corresponding to the input current Idata is converted into a specific drive gradation value while controlling to be equal to or approximate to the current value when the organic EL element OEL performs the light emission operation with the brightness gradation. (Gradation conversion processing), drive control is performed so that the change tendency of the output current It (output gradation) with respect to the input current Idata (input gradation) exhibits linearity.

<First Embodiment>
(Current setting process / gradation conversion process)
FIG. 11 shows the relationship between the gradation current (input current) and the light emission drive current (output current) for explaining the first embodiment of the current setting process and the gradation conversion process in the display device according to the present invention. FIG. 6 is a diagram illustrating a correspondence relationship between luminance gradation (input gradation) and light emission luminance (output gradation). Here, when a gradation current (input current) of 6.2 μA (6.2E-06A) is supplied as the maximum gradation current to the display panel having the screen size of 30 inches WXGA shown in Table 1, light emission is performed. A case where a current value of 3.7 μA (3.7E-06A) corresponding to the output gradation value 14 is obtained as the drive current (output current) will be described.

That is, in the display device according to the present invention, as shown in FIG. 11A, the display signal generation circuit 160 generates the gradation current Ipix supplied to the display pixel EM as the input current Idata by the data driver 130. The current value corresponding to the luminance gradation itself of the display data to be displayed (that is, the current value on the current characteristic line Spi shown in FIG. 9A) is set larger by a predetermined coefficient α (α> 1). The current setting process is performed, and the current value of the light emission drive current Ib supplied to the organic EL element OEL as the output current It (that is, the current value on the current characteristic line Shi) is expressed on each floor on the current characteristic line Sqi indicating linearity. The current value of the input current Idata (gradation current Ipix) corresponding to each gradation value of the input gradation is set so as to match or approximate the output current value corresponding to the tone (for example, from 0 to 6.2 μA) Any power Value).

  Further, as shown in FIG. 11B, the signal correction circuit 140 causes the gradation value of the luminance gradation of the display data to be a predetermined value in the organic EL element OEL out of the output current It on the current characteristic line Shi. A specific drive gradation value (shown in FIG. 11 (b)) corresponding to an output current value (a circled point in FIG. 11 (a)) capable of realizing a light emission operation with light emission luminance (output gradation). Gradation conversion processing for conversion to a gradation characteristic line Srg), and replacing with a drive gradation value having a smaller number of gradations than the luminance gradation (input gradation) of the display data, Each gradation on the gradation characteristic line Srg corresponding to the current characteristic line Sri having a linear characteristic in which the relationship of the output gradation to the input gradation in the display pixel EM (gradation characteristic line Shg) is an ideal writing state. A gradation conversion pattern is set so as to match or approximate the value.

  Specifically, for example, the gradation conversion process includes 16 gradations with display data luminance gradations of 0 to 15, and a 4-bit data driver 130 corresponding to the 16 gradations is used. When the gradation current Ipix (input current Idata) is generated, the display is performed in consideration of the influence of the parasitic capacitance Cttl added to the data line DL and the transistor characteristics of the transistor element TrA, as shown in FIG. The current value (current characteristic line Shi) of the light emission drive current Ib (output current It) supplied to the organic EL element OEL corresponding to each gradation value of the luminance gradation of data is linear with respect to each gradation value. As shown in FIG. 11B, each gradation value 0 to 15 of each luminance gradation of the display data is selected from among 16 gradations. 8 gradation values of 0, 3, 5, 6, 7, 8, 9, 10 Configured to assign to.

  Here, in each gradation value 0, 3, 5, 6, 7, 8, 9, 10 of the input gradation replaced by the gradation conversion processing, the current characteristics shown in FIGS. Based on the gradation characteristics, output current It having current values corresponding to the gradation values 0, 2, 4, 6, 8, 10, 12, and 14 of the output gradation is obtained.

  In other words, in the present embodiment, the signal correction circuit 140 converts each gradation value of 0 to 15 gradations defined by the display data supplied from the display signal generation circuit 160 to 0, 3, 5, 6, It is converted into gradation values (drive gradation values) of 7, 8, 9, 10 (as corrected display data) and supplied to the data driver 130, and the data driver 130 corresponds to the converted gradation values. The current value of the gradation current Ipix is set to a predetermined coefficient α times the light emission drive current Ib supplied to the organic EL element OEL at the gradation value (input maximum current value 3.7 μA → 6.2 μA; α = 2) .3) and supplying each display pixel EM with a current value corresponding to each output gradation (emission luminance) of 0, 2, 4, 6, 8, 10, 12, 14 The light emission drive current Ib having the organic EL element OE It is driven and controlled so as to be supplied to.

(Configuration example of signal correction circuit)
Next, a specific configuration example of a signal correction circuit applicable to the display device according to the present embodiment will be described with reference to the drawings.
First, in order to simplify the description, a 2-bit type logic gate circuit is shown, and the gradation conversion processing of the signal correction circuit according to the present embodiment will be described.
FIG. 12 is a logic circuit diagram and a truth table showing a first configuration example of the signal correction circuit according to the present embodiment. Expression (21) is a logical operation expression in the signal correction circuit according to this configuration example.

  As shown in FIG. 12A, the signal correction circuit according to the first configuration example is an inverter that inverts an input value Ain out of 2-bit input values Ain and Bin that define the luminance gradation of display data. 21, a two-input AND circuit (hereinafter abbreviated as “AND circuit”) 22 having the inverted output from the inverter 21 as one input and the input value Bin as the other input, and the input value Ain as one And a 2-input OR circuit (hereinafter abbreviated as “OR circuit”) 23 having the logic output of the AND circuit 22 as the other input, and the logic output of the OR circuit 23 as the output value Aout. The output value Bout is constantly set to “0”.

  That is, in the signal correction circuit according to this configuration example, as shown in the equations (b) and (21) of FIG. 12, 2-bit, 4-gradation (0-3) gradation data consisting of input values Ain and Bin. (Brightness gradation value of display data) is converted into gradation data of two gradations consisting only of gradation values 0 and 2 (driving gradation value of corrected display data; input gradation to data driver 130). be able to.

Next, a specific configuration example of a signal correction circuit having a 4-bit logic gate circuit corresponding to a simulation result in the above-described display panel and gradation conversion processing thereof will be described.
FIG. 13 is a logic circuit diagram showing a second configuration example of the signal correction circuit according to the present embodiment, and FIG. 14 is a truth table in the signal correction circuit according to the configuration example. Expression (22) is a logical operation expression in the signal correction circuit according to this configuration example.

  As shown in FIG. 13, the signal correction circuit according to the second configuration example includes the input values Ain, Bin, Cin among the 4-bit input values Ain, Bin, Cin, Din that define the luminance gradation of the display data. Inverters 31, 32, and 33, and an AND circuit 34 that inputs the input values Ain and Bin, and an AND circuit 35 that uses the inverted output from the inverter 31 as one input and the input value Bin as the other input. AND circuit 36 having the input value Ain as one input and the inverted output from the inverter 32 as the other input and the AND circuit 36 having the inverted output from the inverter 32 as one input and the input value Cin as the other input The circuit 37, an AND circuit 38 having the input value Bin as one input and the inverted output from the inverter 33 as the other input, the input value Ain and the inverted output from the inverter 32, and the inverter 33 An AND circuit (three-input AND circuit) 39 having the inverted outputs of the AND circuit 35 as one input, an OR circuit 40 having the logical output of the AND circuit 35 as one input and the logical output of the AND circuit 36 as the other input, and AND An OR circuit 41 having the logic output of the circuit 36 as one input and the input value Cin as the other input, and an OR circuit (three-input OR circuit) 42 having the logic outputs of the AND circuits 37, 38, and 39 as inputs. The logical output of the AND circuit 34 is the output value Aout, the logical output of the OR circuit 40 is the output value Bout, the logical output of the OR circuit 41 is the output value Cout, and the logical output of the OR circuit 42 is the output value Dout. It is configured as follows. Note that the input value Din is not used for a logical operation in the signal correction circuit according to this configuration example.

  That is, in the signal correction circuit according to the present configuration example, as shown in FIGS. 14 and (22), a 4-bit, 16-gradation (0-15) gradation composed of input values Ain, Bin, Cin, and Din. The data (luminance gradation value of display data) is converted into gradation data of 8 gradations composed of gradation values 0, 3, 5, 6, 7, 8, 9, 10 (driving gradation value of corrected display data). Can be made to correspond to the gradation value of the input gradation (corrected display data) supplied to the data driver 130 shown in FIG.

  Therefore, according to the display device 100 according to the present embodiment, the display data (each gradation value of the luminance gradation) supplied from the display signal generation circuit 160 corresponds to the gradation characteristics of the display panel 110 by the signal correction circuit 140. The corrected display data (driving gradation value) is generated by the conversion, and the gradation corresponding to the corrected display data by the data driver 130 and having a current value corresponding to the current characteristic of the display panel 110 is generated. By generating a current and supplying the current to each display pixel EM, non-linearity at the time of gradation display due to the transistor characteristics of the transistor elements constituting the display pixel EM provided in the display panel 110 is suppressed. In addition, the display data writing DL caused by the parasitic capacitance added to the data line DL provided in the display panel 110 can be prevented from being insufficiently written. Since it can be able to emit light of the organic EL element (light emitting element) in proper luminance gradation corresponding to display data, improve the display image quality at the time of image display.

Next, another configuration example of the signal correction circuit applicable to the present embodiment and its gradation conversion processing will be described.
FIG. 15 is a functional block diagram illustrating a third configuration example of the signal correction circuit according to the present embodiment, and FIG. 16 illustrates an example of a gradation conversion table applied to the signal correction circuit according to the configuration example. FIG.

  In the first and second configuration examples described above, the case where each gradation value of the luminance gradation of the display data is fixedly converted using a predetermined logic gate circuit (logical operation expression) has been described. In this configuration example, table data (gradation conversion table) in which each gradation value of display data and each gradation value (drive gradation value) after display data are associated in advance based on the gradation characteristics of the display panel. Is used to perform the gradation conversion process.

  That is, as shown in FIG. 15, the signal correction circuit according to the present configuration example is based on the gradation characteristics of the display panel (that is, the gradation characteristic lines Srg and Shg as shown in FIG. 11B). 16, a table memory (storage means) 51 that stores the correspondence between gradation values (gradation conversion pattern) as shown in FIG. 16 and display data supplied as a digital signal from the display signal generation circuit 160. A gradation value (luminance gradation value) that defines the luminance gradation is extracted, the gradation value (driving gradation value) corresponding to the luminance gradation value is read with reference to the table data, and the driving floor And a gradation value reference unit 52 that generates corrected display data composed of tone values.

Here, a rewritable storage unit may be applied as the table memory 51, and the gradation conversion pattern may be appropriately rewritten (or updated) according to the gradation characteristics of the display panel 110.
According to this, similarly to the signal correction circuits according to the first and second configuration examples described above, the organic EL element (light emitting element) can be caused to emit light at a luminance gradation appropriately corresponding to display data. Even if the gradation characteristics vary from display device to display device or the display panel specifications are changed, the gradation conversion pattern can be rewritten as appropriate according to the gradation characteristics of the display panel. Therefore, a desired gradation conversion process can be easily executed by a signal correction circuit and a data driver having the same or equivalent configuration.

<Second Embodiment>
(Current setting process / gradation conversion process)
Next, a second embodiment of the current setting process and the gradation conversion process in the display device according to the present invention will be described with reference to the drawings. FIG. 17 shows the simulation results (current characteristics) shown in FIG. Is a characteristic diagram showing another correspondence relationship (gradation characteristic) between the luminance gradation (input gradation) based on display data and the light emission luminance (output gradation) of the light emitting element. Here, as in the first embodiment described above, a gradation current (input current) of 6.2 μA (6.2E-06A) is applied to the display panel having the specifications shown in Table 1 as the maximum gradation voltage. A case where a current value of 3.7 μA (3.7E-06A) corresponding to the output gradation value 7 is obtained as the light emission drive current (output current) when supplied will be described.

  In the present embodiment, the display panel 110 (display pixel EM) has the same characteristics as the simulation result shown in FIG. 9A described above, and is supplied from the data driver 130 to each display pixel EM. The current value of the light emission drive current Ib (output current) supplied to the organic EL element OEL of each display pixel EM is parasitic on the data line DL with respect to the gradation current Ipix (≈write current Ia; input current). Current characteristics that cause a shortage of writing due to the capacitance component and are small overall and non-linear as compared to current characteristics (current characteristic line Sri having linearity) indicating an ideal writing state ( Current characteristic line Spi), and as shown in FIG. 17, the luminance gradation (input gradation) of the display data is set to 8 gradations (that is, 3 bits) of gradation values 0 to 7, and Based on the current characteristic line Sri The light emission luminance (output gradation) of the organic EL element OEL with respect to each gradation value of the above-described luminance gradation is compared with the gradation characteristic (gradation characteristic line Srg having linearity) indicating an ideal relationship as a whole. A case where the gradation characteristic (gradation characteristic line Spg) is low and has nonlinearity will be described.

  In the first embodiment described above, when the gradation current Ipix corresponding to the luminance gradation of the display data is generated, as shown in FIG. 11A, the parasitic capacitance C added to the data line DL. In consideration of the influence of the transistor characteristics of the transistor element TrA and a specific gradation such that the current value of the light emission drive current Ib supplied to the organic EL element OEL with respect to each gradation value of the luminance gradation has linearity Since only the value (driving gradation value) is selectively extracted and the gradation conversion processing for setting each gradation value of the luminance gradation as the driving gradation value is applied, the luminance gradation of the display data is changed. The number of gradations after gradation conversion is reduced with respect to the number of gradations. Therefore, depending on the degree of gradation expression of the image information displayed on the display panel, there is a possibility that the display image quality is deteriorated due to the decrease in the number of gradations.

  Therefore, in the display device (display driving device) according to the present embodiment, the number of input bits of the data driver that generates the gradation current corresponding to the luminance gradation of the display data is set to the number of gradations of the luminance gradation of the display data. When the gradation conversion processing is performed in the display panel (display pixel) having the above-described characteristics, the same number of luminance gradations of the display data are set. By converting the drive gradation value having the number of gradations (that is, setting the number of input gradations and the number of output gradations to the same number), it is possible to suppress the deterioration in display image quality due to the decrease in the number of output gradations. And a control method.

This will be specifically described below.
FIG. 18 is a diagram illustrating the relationship between the gradation current (input current) and the light emission drive current (output current) for explaining the current setting process according to the present embodiment. FIG. It is a figure which shows the correspondence of input gradation (luminance gradation) and output current (light emission drive current) for demonstrating the gradation conversion process which concerns. Here, when a gradation current (input current) of 6.2 μA (6.2E-06A) is supplied as the maximum gradation voltage to the display panel shown in Table 1, as a light emission drive current (output current), A case where a current value of 3.7 μA (3.7E-06A) corresponding to the output gradation value 7 is obtained will be described.

That is, in the display device according to the present embodiment, as shown in FIG. 11A, the data driver 130 supplies the display pixel EM as the input current Idata as shown in FIG. 18A. The gradation current Ipix (≈write current Ia) is set to a predetermined value with respect to the current value corresponding to the luminance gradation itself of the display data (that is, the current value on the current characteristic line Spi shown in FIG. 9A). A current setting process is performed to set the coefficient α (α> 1) times larger so as to approximate the output current value corresponding to each gradation on the current characteristic line Sqi exhibiting linearity (current characteristic line Shj). .

  Here, based on the gradation characteristics shown in FIG. 17 and the current characteristics based on the current setting process shown in FIG. 18A, each gradation value (0 to 7) of the input gradation (luminance gradation of display data). ) And the value of the input current, as shown in FIG. 18B, when the input current value corresponds to the input gradation value “3”, the output corresponding to the output gradation value “1” is obtained. When the current value is obtained and the input current value corresponds to the input gradation value “5”, the output current value corresponding to the output gradation value “2” is obtained and the input corresponding to the input gradation value “6”. An output current value corresponding to the output gradation value “3” is obtained for the current value, and an output current corresponding to the output gradation value “4” is obtained for the input current value corresponding to the input gradation value “7”. When the input current value corresponding to the input gradation value “8” is obtained, the output current value corresponding to the output gradation value “5” is obtained. When the input current value corresponds to “9”, an output current value corresponding to the output gradation value “6” is obtained, and when the input current value corresponds to the input gradation value “10”, the output gradation value “ An output current value corresponding to 7 ″ is obtained (refer to each circled point in FIG. 18A). Note that the numbers in the box in FIG. 18A indicate the correspondence between the output current value and the output gradation value in each current characteristic (current characteristic lines Sri, Shj).

  In the display device according to the present embodiment, the correspondence (characteristic line Shk) between the input gradation (luminance gradation based on display data) and the input current (gradation current, write current) is linear. (The characteristic line Sti in FIG. 18B), the signal correction circuit 140 sets each gradation value of the input gradation (eight gradations 0, 1, 2, 3, 4, 5, 6, 7). Are selected from gradation values having a larger number of gradations (for example, 16 gradations) and correspond to a specific driving gradation value having the same number of gradations as the input gradations in a 1: 1 ratio. (Tone conversion processing) is performed.

  In the gradation conversion processing, the number of input bits (4 bits) of the data driver 130 is larger than the number of bits (3 bits) corresponding to the number of gradations (8 gradations) of the luminance gradation (input gradation) of the display data. ) Is set to increase, and the data driver 130 has each gradation value (0, 1, 2, 3, 4,...) Of the luminance gradation (input gradation) based on the display data as shown in FIG. 5 to 8 gradations (5, 6, 7) are selectively extracted from the gradation values (16 gradations from 0 to 15) set according to the number of input bits, and replaced with a 1: 1 relationship. Each gradation value (0, 3, 5, 6, 7, 8, 9, 10) is input (see input gradation (returned gradation) in FIG. 19).

  Here, as shown in FIG. 19, the relationship (characteristic line Shj) of the output gradation (or output current) with respect to the input gradation in each display pixel EM is a current characteristic line Sri indicating an ideal writing state. The gradation conversion pattern is set so as to match or approximate each input gradation value on the corresponding gradation characteristic line Srg having linearity.

  In other words, in the present embodiment, each of the gradation values (0, 1, 2, 3, 4, 5) based on the luminance gradation of the display data supplied from the display signal generation circuit 160 by the signal correction circuit 140 is displayed. , 6, 7) are obtained from 16 gradations 0 to 15 so that an output gradation corresponding to the gradation value (output current value corresponding to each gradation on the gradation characteristic line Srg) is obtained. Corresponding to the luminance gradation of the display data by converting the gradation values (drive gradation values) of 0, 3, 5, 6, 7, 8, 9, 10 to 1: 1 and supplying them to the data driver 130 Drive control is performed so as to supply a light emission drive current Ib having a current value to the organic EL element.

(Configuration example of signal correction circuit)
Next, a specific configuration example of a signal correction circuit applicable to the display device according to the present embodiment will be described with reference to the drawings.
FIG. 20 is a logic circuit diagram showing a configuration example of the signal correction circuit according to the present embodiment, and FIG. 21 is a truth table of the signal correction circuit according to the present embodiment. Expression (31) is a logical operation expression in the signal correction circuit according to this configuration example.

  As shown in FIG. 20, the signal correction circuit 140 according to this configuration example inverts the input values Ain, Bin, and Cin out of the 3-bit input values Ain, Bin, and Cin that define the luminance gradation of the display data. Inverters 61, 62, and 63 to be processed, an AND circuit 64 that inputs the input values Ain and Bin, and an AND circuit (three-input AND circuit that receives the input value Ain and the inverted output from the inverter 62, and the input value Cin, respectively) ) 65 and the input value Bin as one input, the AND circuit 66 having the inverted output from the inverter 61 as the other input, the inverted output from the inverter 62 as one input, and the input value Ain as the other input AND circuit 68 that receives the input values Bin and Cin and the inverted output from the inverter 61, and the input value Bin as one input and the inverted signal from the inverter 63 AND circuit 69 with the other input as input, AND circuit 70 with input value Ain and the inverted output from inverter 62, and inverted output from inverter 63 as input, and inverted outputs from inverters 61, 62, and 63, respectively. The AND circuit 71 and the logical output of the AND circuit 64 as one input and the logical output of the AND circuit 65 as the other input and the logical output of the AND circuit 65 as one input, respectively. An OR circuit 73 having the logic output of the AND circuit 66 as the other input, an OR circuit 74 having the logic output of the AND circuit 67 as one input and the logic output of the AND circuit 68 as the other input, and an AND circuit 69 OR circuit (three-input OR circuit) 75 having the logical outputs of 70, 71 as inputs, and the logical output of the OR circuit 72 as the output value Aout, OR circuit The logical output 73 is the output value Bout, the logical output of the OR circuit 74 is the output value Cout, and the logical output of the OR circuit 75 is the output value Dout.

  That is, in the signal correction circuit according to the present configuration example, as shown in FIGS. 21 and (31), 3-bit 8-gradation (0-7) gradation data (display) composed of input values Ain, Bin, Cin (display) The luminance gradation value of the data is composed of a specific gradation value (for example, 0, 3, 5, 6, 7, 8, 9, 10 described above) out of 4 bits and 16 gradations (0 to 15). It can be converted into 8-gradation gradation data (driving gradation value of display data after correction) in a 1: 1 relationship, and the input floor supplied to the data driver 130 shown in FIG. 18B and FIG. It is possible to correspond to the gradation value of the tone (gradation after conversion).

  Therefore, the display device according to the present embodiment also has linearity corresponding to the gradation characteristics of the display panel by the signal correction circuit for each gradation value of the luminance gradation of the display data supplied from the display signal generation circuit. The gray level in which the current value is set by the data driver so as to correspond to the converted gray level value (driving gray level value) and to have linearity corresponding to the current characteristic of the display panel A current can be generated and supplied to each display pixel.

  Here, in the signal correction circuit according to the present embodiment, each gradation value of the luminance gradation in the gradation conversion processing is converted into gradation characteristics from among gradation values larger than the number of gradations of the luminance gradation. By selecting a gradation value (driving gradation value) that can be linearized and performing a conversion process of replacing the gradation value with the same number as the luminance gradation of the display data by 1: 1. The non-linearity at the time of gradation display due to the transistor characteristics of the transistor elements constituting the display pixels arranged in the display panel can be suppressed and added to the data lines arranged in the display panel. Since insufficient writing of display data due to parasitic capacitance can be suppressed, the organic EL element (light emitting element) can be caused to emit light at a luminance gradation appropriately corresponding to the display data. Preparation It is possible to suppress satisfactorily drop in display quality is secured.

  In the second embodiment described above, the configuration using the logic gate circuit as the signal correction circuit is shown. However, the present invention is not limited to this, and the first embodiment described above is not limited thereto. Similarly to the case of the configuration example 2, the table data having the correspondence relationship (gradation conversion pattern) shown in FIG. 14 is used for each gradation value of the luminance gradation of the display data. A corresponding drive gradation value may be read out and 1: 1 gradation conversion may be performed.

  Further, the specific configuration examples (logic gate circuit and table data) of the signal correction circuit shown in each of the above-described embodiments correspond only to the gradation characteristics of the display panel that is the object of the above-described simulation. It goes without saying that the invention is not limited to this. Therefore, based on the gradation conversion processing corresponding to the gradation characteristics of the display device (display panel) to which the present invention is applied, the logic gate circuit appropriately combining the logic gates and the correspondence between the gradation values are appropriately determined. The set table data may be applied.

It is a schematic block diagram which shows the basic composition of the display apparatus which concerns on this invention. It is a schematic block diagram which shows the principal part structure of the display apparatus which concerns on this invention. It is a schematic block diagram which shows an example of the data driver applicable to the display apparatus which concerns on this invention. It is a circuit block diagram which shows an example of the voltage current conversion and current supply circuit applicable to the data driver which concerns on this embodiment. It is a circuit block diagram which shows the specific circuit example of the display pixel (light emission drive circuit) applicable to the display apparatus which concerns on this invention. It is a conceptual diagram which shows the operation state of the light emission drive circuit which concerns on a present Example. 3 is a timing chart showing a basic operation of a display pixel to which the light emission driving circuit according to the present embodiment is applied. It is a schematic block diagram which shows one structural example of the display apparatus to which the display pixel which concerns on a present Example is applied. Relationship between gradation current (input current) based on display data supplied to a display panel (display pixel) and light emission drive current (output current) supplied to a light emitting element, and luminance gradation (input) based on display data It is a simulation result showing the relationship between the (gradation) and the light emission luminance (output gradation) of the light emitting element. In order to analyze the simulation result shown in FIG. 9, a schematic circuit showing an addition (connection) state of parasitic capacitance to a display pixel applied to the display device according to the present embodiment and an equivalent circuit in which the circuit configuration is simplified. FIG. The relationship between the gradation current (input current) and the light emission drive current (output current) and the luminance gradation (input gradation) for explaining the current setting process and gradation conversion process in the display device according to the present embodiment. ) And the light emission luminance (output gradation). It is a logic circuit diagram and a truth table showing a first configuration example of a signal correction circuit according to the present embodiment. It is a logic circuit diagram which shows the 2nd structural example of the signal correction circuit which concerns on this embodiment. It is a truth table in the signal correction circuit according to this configuration example. It is a functional block diagram which shows the 3rd structural example of the signal correction circuit which concerns on this embodiment. It is a figure which shows an example of the gradation conversion table applied to the signal correction circuit which concerns on this structural example. Based on the simulation results (current characteristics) shown in FIG. 9A, another correspondence relationship (tone characteristics) between the luminance gradation (input gradation) based on the display data and the light emission luminance (output gradation) of the light emitting element. FIG. It is a figure which shows the relationship between the gradation current (input current) and the light emission drive current (output current) for demonstrating the electric current setting process which concerns on this embodiment. It is a figure which shows the correspondence of input gradation (luminance gradation) and output current (light emission drive current) for demonstrating the gradation conversion process which concerns on this embodiment. It is a logic circuit diagram which shows one structural example of the signal correction circuit which concerns on this embodiment. It is a truth table of the signal correction circuit concerning this embodiment. It is a schematic block diagram which shows the principal part of the light emitting element type display in a prior art. It is an equivalent circuit diagram which shows the structural example of the display pixel (light emission drive circuit and light emitting element) applicable to the light emitting element type display in a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Display apparatus 110 Display panel 120 Scan driver 130 Data driver 140 Signal correction circuit 150 System controller 160 Display signal generation circuit 170 Power supply driver EM Display pixel DC Light emission drive circuit OEL Organic EL element SL Scan line DL Data line TrA Transistor element C Parasitic capacitance

Claims (21)

A display panel comprising: a plurality of signal lines and a plurality of scanning lines orthogonal to each other; and a plurality of display pixels each provided with a current-controlled light emitting element disposed in the vicinity of the intersection of each signal line and each scanning line. A gradation current corresponding to the luminance gradation of display data composed of a plurality of bits of digital signals is supplied to each display pixel via each signal line, and the amount of charge written to the display pixel by the gradation current is supplied. in the display driving device for light-emitting operation of each of light emitting elements by the light emission driving current supplied to the light emitting element have group Dzu,
The number of input bits equal to or greater than the number of bits of the display data, a plurality of drive gradation values corresponding to the number of input bits, and the luminance gradation value of the display data The drive gradation value is converted to be assigned to any one of a plurality of drive gradation values, the gradation current value is set to a value proportional to each of the drive gradation values, and the drive gradation value assigned to the luminance gradation , the luminance gradation of the value of the current value of the light emitting drive current supplied to the light emitting element in accordance with the gradation current corresponding to the drive gradation values assigned to the luminance gradation of the display data A display drive device comprising gradation conversion means set to a value that makes the change characteristic with respect to the change close to linear.   The gradation converting means is configured to provide each gradation value of a luminance gradation of the display data based on an element characteristic of an active element that is provided in at least the display pixel and is related to the supply of the light emission driving current to the light emitting element. The display driving apparatus according to claim 1, wherein a correspondence relationship for converting the value into the driving gradation value is set. The number of input bits of the gradation conversion means is the same as the number of bits of the display data, and each gradation value of the luminance gradation of the display data is selected from the same number of driving gradation values as the number of gradations 3. The display driving device according to claim 1, further comprising means for converting the driving gradation value into the specific driving gradation value. The display driving device includes signal driving means that generates the gradation current corresponding to the number of driving gradation values equal to the number of gradations of the luminance gradation of the display data, and supplies the gradation current to the signal lines. The display driving apparatus according to claim 3, wherein The number of input bits of the gradation converting means is larger than the number of bits of the display data, and the gradation values of the luminance gradation of the display data are selected from the driving gradation values having a number larger than the number of gradations. been, display driver of claim 1 or 2, characterized in that it comprises a means for converting the gradation number and the same number of the drive gradation value. The display driving device includes signal driving means for generating the gradation current corresponding to the driving gradation value that is greater in number than the number of gradations of the luminance gradation of the display data and supplying the gradation current to the signal lines. 6. The display driving device according to claim 5, further comprising: The gradation conversion means, display driving apparatus according to claim 3 or 5, wherein it is configured by the logic gate circuit. The gradation conversion means includes a gradation conversion table in which the gradation value of the luminance gradation of the display data is associated with the driving gradation value, and the gradation conversion table is uniquely defined by referring to the gradation conversion table. the display driving apparatus according to claim 3 or 5, wherein in that it comprises means for determining a driving gradation value. 9. The display driving device according to claim 8 , wherein the gradation conversion table is configured to rewrite a correspondence relationship between a gradation value of a luminance gradation of the display data and the driving gradation value. Said signal driving means, on the basis of the driving grayscale value, claim 4, characterized in that to generate the gradation current having a large current value than the light emission drive current supplied to the light emitting device or 6 The display driving device described. The signal driving means sets the current value of the gradation current based on the driving gradation value so as to be a predetermined coefficient multiple of the current value of the light emission driving current supplied to the light emitting element. 11. The display driving device according to claim 10 , further comprising means. A display panel including a plurality of display pixels each including a current-controlled light emitting element is disposed in the vicinity of each intersection of a plurality of signal lines and a plurality of scanning lines orthogonal to each other, and the plurality of the display lines are arranged via the signal lines. By supplying to each display pixel a gradation current corresponding to the luminance gradation of display data composed of a plurality of bits of digital signals , a light emission driving current based on the amount of charge written to the display pixel is supplied to the light emitting element. In a display device that emits light and displays desired image information on the display panel,
at least,
Scan driving means for sequentially applying scanning signals to the plurality of scanning lines of the display panel to sequentially set the display pixels in a selected state;
The number of input bits equal to or greater than the number of bits of the display data, a plurality of drive gradation values corresponding to the number of input bits, and the luminance gradation value of the display data The drive gradation value is converted to be assigned to any one of a plurality of drive gradation values, the gradation current value is set to a value proportional to each of the drive gradation values, and the drive gradation value assigned to the luminance gradation , the luminance gradation of the value of the current value of the light emitting drive current supplied to the light emitting element in accordance with the gradation current corresponding to the drive gradation values assigned to the luminance gradation of the display data Gradation conversion means set to a value that makes the change characteristic with respect to the change close to linear,
Based on the driving gradation value, the gradation current having a current value larger than the light emission driving current supplied to the light emitting element is generated, and the display set in the selected state by the scanning driving means Signal driving means for supplying the gradation current to the pixel;
A display device comprising: The number of input bits of the gradation conversion means is the same as the number of bits of the display data, and each gradation value of the luminance gradation of the display data is selected from the same number of driving gradation values as the number of gradations 13. The display device according to claim 12 , further comprising means for converting to the specific drive gradation value. The signal driving means includes means for generating the gradation current corresponding to the number of the drive gradation values equal to the number of gradations of the luminance gradation of the display data and supplying the gradation current to the signal lines. The display device according to claim 13 . The number of input bits of the gradation converting means is larger than the number of bits of the display data, and the gradation values of the luminance gradation of the display data are selected from the driving gradation values having a number larger than the number of gradations. 13. The display device according to claim 12 , further comprising means for converting the drive gradation values to the same number as the number of gradations. The signal driving means includes means for generating the gradation current corresponding to the driving gradation value that is greater in number than the gradation number of the luminance gradation of the display data and supplying the gradation current to the signal lines. The display device according to claim 15 , wherein the display device is a display device. The display pixel is at least
Charge holding means comprising a holding capacitor for holding the charge based on the gradation current as a voltage component;
Drive current control means for causing the light emission drive current to flow to the light emitting element based on the voltage component held in the charge holding means;
A light emission drive circuit comprising:
The gradation conversion means constitutes at least the drive current control means, and each of the gradations of the brightness gradation of the display data based on element characteristics of an active element involved in the supply of the light emission drive current to the light emitting element display device according to any one of claims 12 to 16 and sets a correspondence relationship for converting the value to the drive gradation value. The light emitting device, a display device according to any one of claims 12 to 17, characterized in that an organic electroluminescence element. A display panel including a plurality of display pixels each including a current-controlled light emitting element is disposed in the vicinity of each intersection of a plurality of signal lines and a plurality of scanning lines orthogonal to each other, and the plurality of the display lines are arranged via the signal lines. By supplying to each display pixel a gradation current corresponding to the luminance gradation of display data composed of a plurality of bits of digital signals , a light emission driving current based on the amount of charge written to the display pixel is supplied to the light emitting element. In a drive control method for a display device that performs a light emission operation and displays desired image information on the display panel,
at least,
The luminance gradation value of the display data is converted to be assigned to any one of a plurality of driving gradation values corresponding to the number of input bits equal to or greater than the number of bits of the display data, and the gradation set the value of the current value proportional to the respective drive gradation values, the drive gradation value assigned to the luminance gradation, the drive gradation values assigned to the luminance gradation of the display data Setting a change characteristic of the current value of the light emission drive current supplied to the light emitting element in response to the corresponding gradation current to a change in the luminance gradation value to a value that approximates linearity;
Based on the drive gradation value, the gradation current having a current value larger than the light emission drive current supplied to the light emitting element is generated, and the gradation current is supplied to the display pixel. Steps,
A drive control method for a display device, comprising: The step of converting each gradation value of the luminance gradation of the display data into the driving gradation value is equal to each gradation of the luminance gradation of the display data , wherein the number of input bits is the same as the number of bits of the display data. 20. The drive control method for a display device according to claim 19 , wherein a value is converted into the specific drive gradation value selected from the same number of drive gradation values as the number of gradations. The step of converting each gradation value of the luminance gradation of the display data into the driving gradation value when the number of input bits is larger than the number of bits of the display data, 20. The drive control of the display device according to claim 19 , wherein the drive gradation value is selected from the drive gradation values greater than the number of gradations, and is converted into the same number of drive gradation values as the number of gradations. Method.

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