JP2002215097A - Electronic display and driving method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electronic display capable of displaying a picture with a highly accurate gradation expression even in a low signal level area. SOLUTION: When a data discrimination driving circuit 11 discriminates that a write current of a pixel data Dv from a signal source circuit 1 exceeds Io, a high quality picture with a gradation expression proportional to a recording current I of the pixel data Dv is displayed on a display 7 by a driving signal Fd of a reference duty ratio from a data discrimination driving circuit 12 via a change-over terminal t1 of a switch circuit 10, and when it is discriminated that the write current of the pixel data Dv is not higher than Io, a high quality picture with a gradation expression not higher than the No exactly corresponding to the signal level is displayed on the display 7 by a driving signal Fdm of a duty raio larger than the reference duty ratio according to the signal level of the picture data Dv outputted from an FRC circuit 3 via a change-over terminal t2 of the switch circuit 10, and thus a high quality picture with gradations exactly expressing picture signals at the whole signal levels can be displayed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic display comprising a plurality of light emitting elements arranged at intersections between scanning lines and signal lines arranged in a matrix and a driving method thereof.

[0002]

2. Description of the Related Art LDs (light emitting diodes) and EL elements (electroluminescent elements) are used as light emitting elements, and these light emitting elements are arranged at intersections between scanning lines and signal lines arranged in a matrix. Electronic display configured by FA (Factory Automat)
ion) In recent years, not only in the field of devices and financial terminals, but also in the field of workstations, taking advantage of the feature that high-precision, large-capacity display is possible. As a light-emitting element of this type of electronic display, an EL element has recently attracted attention. In particular, a thin-film EL element having a multilayer thin-film structure in which a base material is added and a base material is sandwiched between electrodes has been used in a thin-film display panel. Convenient and long operating life,
Low drive voltage of 10V or less, several hundred to several thousand cd
/ Cm ^2, which is capable of displaying a high-luminance image, has been rapidly developed.

As the above-mentioned electronic display, an active matrix type electronic display which drives a light emitting element by an active element such as a MOS transistor arranged corresponding to the light emitting element is generally used. The configuration of the main part of the electronic display shown in FIG. 3 is as shown in FIG. 3, and a signal source circuit 1 for outputting pixel data Dv corresponding to an input video signal is provided. A driver circuit 6 for supplying the drive signal Fd to the active element and causing the light emitting element to emit light corresponding to image data is connected, and a driver active matrix display 7 is connected to an output terminal of the driver circuit 6.

In a conventional electronic display having such a configuration, the gray scale (IRE) of image display obtained by the light emitting element emitting light by the write current supplied from the active element to the light emitting element, and the write current (I) and FIG.
As shown in (1), a linear relationship of the gradient corresponding to the material of the light emitting element is recognized. In this type of electronic display, an image display is performed by supplying a write current at a predetermined duty ratio to a light emitting element connected to a selected scanning line via an active element, and performing image display. If the number of scanning lines is increased and the number of light emitting elements is increased, the writing time of the writing current, that is, the charging time of the capacitor charged with the writing current to the light emitting elements is shortened. When the write time is shortened in this way, especially in a region where the write current value is small, the write time is insufficient and the capacitor cannot be charged with a predetermined amount of electric charge within the time. Corresponding gradation display is not performed, the contrast of the image is disturbed, and the quality of the displayed image is reduced.

[0005]

In order to solve the above-mentioned problem, the same parts as those shown in FIG. 3 are provided with the same reference numerals as those shown in FIG. In this electronic display, a data discriminating drive circuit 11 for discriminating the signal level of the pixel data Dv and performing a driving operation based on the discrimination result is connected to an output terminal of the signal source circuit 1. Are connected to the switching terminal t1 of the switch circuit 10, and the control terminal of the data discrimination drive circuit 11 is connected to the zero approximation circuit 8 that performs zero gradation approximation and to the stitch circuit 10. And
The output terminal of the zero approximation circuit 8 is connected to the switching terminal t2 of the switch circuit 10, and the common terminal to of the switch circuit 10
Are connected to the driver circuit 6, and the output terminal of the driver circuit 6 is connected to the active matrix display 7.

In this electronic display, the signal source circuit 1
The signal level of the pixel data Dv is determined by the data determination drive circuit 11, and the write current I corresponding to the determination value is I
When the value exceeds o, the switch circuit 5 is switched to the switching terminal t1 side by the control signal from the control terminal of the data discrimination drive circuit 11, and the drive signal Fd of the reference duty ratio output from the data discrimination drive circuit 11 is output. Is input to the driver circuit 6 via the switch circuit 10, and the driver circuit 6 supplies a write current proportional to the signal level of the pixel data Dv to the light emitting element via the active element.
In the active matrix display 7, an image is displayed at a gradation corresponding to the pixel data Dv accurately.

On the other hand, when the write current corresponding to the discrimination value in the data discrimination drive circuit 11 is equal to or less than Io, the switch circuit 1 is controlled by the control signal from the data discrimination drive circuit 11.
0 is switched to the switching terminal t2 side, and from the zero approximation circuit 8 operated by the control signal from the data discrimination drive circuit 11,
The zero approximation command signal Fo is input to the driver circuit 6 via the switch circuit 10. Then, based on the zero approximation command signal Fo, the drive signal output from the driver circuit 6 causes the active matrix display 7 to display the signal shown in FIG.
As shown in (5), the gradation is set to 0 in the low signal level region where the write current is equal to or lower than Io, and black image display is performed on the pixel data Dv in the low signal level region.

Thus, according to the electronic display having the configuration shown in FIG. 5, the data discrimination drive circuit 11 determines that the write current corresponding to the signal level of the pixel data Dv based on the input video signal has exceeded Io. Then
The switch circuit 10 is switched to the switching terminal t1 side, and the drive signal Fd of the reference duty ratio output from the data discrimination drive circuit 11 is input to the driver circuit 6 via the switch circuit 10 and is driven by the driver circuit 6. In the active matrix display 7, the recording current I is supplied to the light-emitting element based on the drive signal Fd, and the light-emitting element emits light in a gradation expression proportional to the recording current I, and accurately outputs the pixel data Dv. The corresponding image is displayed. On the other hand, when the data discrimination drive circuit 11 determines that the write current corresponding to the signal level of the pixel data Dv based on the input video signal is equal to or less than Io, the data discrimination drive circuit 11 causes the switch circuit 10 to switch to the switching terminal. t
2 and the zero approximation command signal Fo output from the zero approximation circuit 8 is input to the driver circuit 6 via the switch circuit 10, and the drive signal from the driver circuit 6 causes the active matrix display 7 to write data. The gradation is set to 0 for a low-level region where the input current is equal to or less than Io, and a black image is displayed for the pixel data Dv in the low-level region.

As described above, the zero approximation setting for setting the gradation to 0 below the gradation No. is performed, and a single black display is performed on the pixel data Dv in the corresponding low-level area, which is a conventional problem. Disturbance in the contrast of the image in the low signal level region is prevented, but with this gradation No, gradation cannot be displayed, and the image is in a blackened state, and a high-quality image display appropriately corresponding to the input video signal is performed. Can not.

The present invention has been made in view of the current state of image display on such an electronic display as described above, and a first object of the present invention is to provide a high-precision gradation expression even in a low signal level region. To provide an electronic display capable of displaying a selected image. A second object of the present invention is to provide a driving method of an electronic display that drives an electronic display so that an image can be displayed with high-precision gradation expression even in a low signal level region.

[0011]

In order to achieve the first object, according to the present invention, a scanning line and a signal line are arranged in a matrix, and a plurality of the scanning lines and the signal lines are provided. A light emitting element and an active element for driving the light emitting element are arranged at the intersections of, respectively, current is supplied to the light emitting element by the active element, light emission corresponding to pixel data is performed, and an input video signal is generated. In an electronic display for displaying a corresponding image, a data discriminating means for discriminating a signal level of the pixel data, and when a signal level discriminated by the data discriminating means exceeds a predetermined value, a reference duty ratio is used. Normal control means for driving the light emitting element to emit light by a current supplied from the active element to the light emitting element in accordance with the signal level; and When the signal level determined by the different means is equal to or less than the predetermined value, based on a duty ratio larger than the reference duty ratio, the current supplied from the active element to the light emitting element in accordance with the signal level. And low-level control means for driving the light emitting element to emit light.

According to such a means, the signal level of the pixel data is determined by the data determining means, and when the determined signal level exceeds a predetermined value, the normal control means determines the signal level based on the reference duty ratio. Accordingly, if the light emitting element is driven to emit light by the current supplied from the active element to the light emitting element in accordance with the signal level of the pixel data, and the signal level determined by the data determining means is lower than a predetermined value, The light emitting element is driven and emitted by the current supplied from the active element to the light emitting element in accordance with the signal level of the pixel data with a duty ratio larger than the reference duty ratio by the level control means. The duty ratio is changed in accordance with Gradation display in the low signal level region is performed with high accuracy, proper precise gradation expression over a wide signal level is high quality image display is performed is performed.

According to a second aspect of the present invention, a scanning line and a signal line are arranged in a matrix, and light is emitted at a plurality of intersections between the scanning line and the signal line. An element and an active element for driving the light emitting element are arranged, and a current is supplied to the light emitting element by the active element, light emission corresponding to pixel data is performed, and image display corresponding to an input video signal is performed. In a method for driving an electronic display, a data determining step of determining a signal level of the pixel data, and when the signal level determined in the data determining step exceeds a predetermined value, the signal level is determined based on a reference duty ratio. A normal control step of driving the light emitting element to emit light by a current supplied from the active element to the light emitting element corresponding to the level, When the signal level determined in the data determination step is equal to or less than the predetermined value, the signal is supplied from the active element to the light emitting element in accordance with the signal level based on a duty ratio larger than the reference duty ratio. A low-level control step of driving the light-emitting element by a current to emit light.

According to such a method, the signal level of the pixel data is determined in the data determining step, and when the determined signal level exceeds a predetermined value, a normal control step is performed based on the reference duty ratio. Accordingly, if the light emitting element is driven to emit light by the current supplied from the active element to the light emitting element in accordance with the signal level of the pixel data, and the signal level determined in the data determination step is equal to or lower than a predetermined value, In the level control step, the light emitting element is driven and illuminated by the current supplied from the active element to the light emitting element in accordance with the signal level of the pixel data according to the signal level of the pixel data with a duty ratio larger than the reference duty ratio. By changing the duty ratio in accordance with the Gradation display in level region is carried out with high precision, suitable precise gradation expression over a wide signal level is high quality image display is performed is performed.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on an embodiment of an electronic display with reference to FIGS. FIG. 1 is a block diagram illustrating a configuration of a main part of the present embodiment, and FIG. 2 is a characteristic diagram illustrating an operation of the present embodiment.

In the present embodiment, as shown in FIG. 1, a signal source circuit 1 for outputting pixel data Dv corresponding to an input video signal is provided, and the output terminal of the signal source circuit 1 is
Connected to a data discrimination drive circuit 12 for discriminating the signal level of the pixel data Dv and performing a driving operation based on the discrimination result;
The output terminal of the data discrimination drive circuit 12 is connected to the switch circuit 1
0 is connected to the switching terminal t1. Further, the control terminal of the data discrimination drive circuit 12 is connected to the FRC (frame rate conversion) circuit 3 for adjusting and setting the duty ratio, and also connected to the switch circuit 10.
Is connected to the switching terminal t2 of the switch circuit 10, the common terminal to of the switch circuit 10 is connected to the driver circuit 6, and the output terminal of the driver circuit 6 is connected to the active matrix display 7.

The operation of this embodiment having such a configuration will be described. In the present embodiment, the signal level of the pixel data Dv from the signal source circuit 1 is determined by the data determination drive circuit 12, and the write current corresponding to the signal level is Io.
Is exceeded, the switching circuit 5 is switched to the switching terminal t1 side by the switching signal from the control terminal of the data determination driving circuit 12, and the driving signal Fd of the reference duty ratio output from the data determination driving circuit 12 is output. Is input to the driver circuit 6 via the switch circuit 10, and a drive signal from the driver circuit 6 supplies a write current proportional to the signal level of the pixel data Dv to the light emitting element via the active element. In the matrix display 7, an image is displayed at a gray scale that accurately corresponds to the pixel data Dv.

On the other hand, the data discriminating drive circuit 12
The write current corresponding to the signal level of the pixel data Dv is Io
If it is determined that the current is less than or equal to the following, the switch circuit 10 is switched by the control signal from the data determination drive circuit 12 to the switching terminal t.
2 and the control signal from the data discriminating drive circuit 12 causes the FRC circuit 3 to set a duty greater than the reference duty ratio, which is set in advance corresponding to a write current value equal to or lower than Io in the low signal level region. Ratio drive signal F
dm is output. Then, this drive signal Fdm is input to the driver circuit 6 via the switch circuit 10, and the drive signal from the driver circuit 6 causes the active matrix display 7 to write the write current of Io or less as shown in FIG. In the low-level signal region, the light-emitting element is driven and emitted by the active element at a duty ratio that is selected in advance according to the signal level of the pixel data Dv. In this case, the drive signal Fdm output from the FRC circuit 3 corresponds to the write current value in the low level signal region.
Are set in advance, and a drive signal Fdm having a duty ratio selected corresponding to the write current value from these is output from the FRC circuit 3,
In the FRC area below the gradation, an image is displayed at a gradation corresponding to the selected duty ratio.

As described above, in the present embodiment, the signal level of the pixel data Dv from the signal source circuit 1 is determined by the data determination drive circuit 11, and the write current corresponding to the signal level is Io. Is determined to have exceeded the threshold value, the active matrix display 7 supplies pixel data to the active matrix display 7 based on the drive signal Fd of the reference duty ratio output from the data determination drive circuit 11 via the switch circuit 10 switched to the switch terminal t1 side. When a high-quality image of gradation expression proportional to the recording current I is displayed corresponding to the signal level of Dv, and the write current corresponding to the signal level of the pixel data Dv is determined to be Io or less, the switching terminal t2 side Selected according to the signal level of the pixel data Dv by the FRC circuit 3 via the switch circuit 10 switched to Drive signal Fdm of duty ratio
Based on the active matrix display 7,
Even in a low-level region where the gradation is equal to or less than No, a high-quality image of a gradation expression corresponding to the signal level is displayed accurately. Therefore, according to the present embodiment, the pixel signals of all signal levels including the low-signal region are displayed. Therefore, it is possible to display a high-quality image accurately expressed in gradation in accordance with the image quality. In this case, since the width of the low-level region is set to the minimum width at which stable light emission is possible, image quality deterioration due to gradation setting in the FRC region is scarcely recognized, and the circuit configuration of the FCR circuit 3 can be simplified. It is also possible to suppress an increase in cost.

[0020]

According to the present invention, the scanning lines and the signal lines are arranged in a matrix.
At a plurality of intersections between the scanning line and the signal line, a light emitting element and an active element for driving the light emitting element are arranged, respectively.
A current is supplied to the light emitting element by the active element, light emission corresponding to the pixel data is performed, and an image display corresponding to the input video signal is performed. In this case, the signal level of the pixel data is determined by the data determination unit. When the determined signal level exceeds a predetermined value, the signal level of the pixel data is determined by the normal control unit based on the reference duty ratio. In response to the above, when the light-emitting element is driven to emit light by the current supplied from the active element to the light-emitting element, and the signal level determined by the data determination means is equal to or less than a predetermined value, the low level control means The light emitting element is driven and emits light by the current supplied from the active element to the light emitting element according to the signal level of the pixel data with the duty ratio larger than the ratio. As described above, in the low signal level region, the duty ratio is changed according to the signal level, and the light emitting current corresponding to the signal level is supplied to the light emitting element accurately. Is performed with high accuracy, and high-quality image display in which accurate gradation expression is performed over a wide range of signal levels becomes possible.

According to a second aspect of the present invention, a scanning line and a signal line are arranged in a matrix, and the light emitting element and the light emitting element are arranged at a plurality of intersections between the scanning line and the signal line. An electronic display in which the active elements to be driven are arranged is driven, a current is supplied to the light emitting elements by the active elements, light emission corresponding to pixel data is performed, and image display corresponding to the input video signal is performed. In this case, in the data determination step, the signal level of the pixel data is determined. When the determined signal level exceeds a predetermined value, the signal level of the pixel data is determined in the normal control step based on the reference duty ratio. In response to the above, when the light emitting element is driven to emit light by the current supplied from the active element to the light emitting element, and the signal level determined in the data determination step is equal to or less than a predetermined value, the reference duty is reduced in the low level control step. The light emitting element is driven and emits light by the current supplied from the active element to the light emitting element in accordance with the signal level of the pixel data with the duty ratio larger than the ratio. As described above, in the low signal level region, the duty ratio is changed according to the signal level,
The light-emitting element is supplied with a light-emitting current that accurately corresponds to the signal level, so that gradation display in the low signal level region is performed with high accuracy, and high-quality display is performed over a wide range of signal levels. Can be displayed.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a main part of an electronic display according to an embodiment of the invention.

FIG. 2 is a characteristic diagram showing an operation of the embodiment.

FIG. 3 is a block diagram showing a configuration of a main part of a conventional electronic display.

FIG. 4 is a characteristic diagram showing an operation of a conventional electronic display whose main part is shown in FIG.

FIG. 5 is a block diagram showing a configuration of a main part of another conventional electronic display.

FIG. 6 is a characteristic diagram showing an operation of the conventional electronic display whose main part is shown in FIG.

[Explanation of symbols]

1 ··· Signal source circuit, 3 ··· FRC circuit, 6 ··· Driver circuit, 7 ··· Active matrix display, 10
..Switch circuits, 12... Data discrimination drive circuits.

Claims (2)

[Claims] 1. A scanning line and a signal line are arranged in a matrix, and a light emitting element and an active element for driving the light emitting element are arranged at a plurality of intersections between the scanning line and the signal line, respectively. A current is supplied to the light emitting element by an active element, light emission corresponding to pixel data is performed, and in an electronic display for displaying an image corresponding to an input video signal, a data determination unit that determines a signal level of the pixel data. When the signal level determined by the data determination unit exceeds a predetermined value, based on a reference duty ratio, the current supplied from the active element to the light emitting element in accordance with the signal level, Normal control means for driving the light emitting element to emit light; and when the signal level determined by the data determination means is equal to or less than the predetermined value, Based on the duty ratio larger than the quasi-duty ratio, corresponding to the signal level,
An electronic display, comprising: a low-level control unit that drives and emits light from the light emitting element by a current supplied from the active element to the light emitting element. 2. A scanning line and a signal line are arranged in a matrix, and a light emitting element and an active element for driving the light emitting element are arranged at a plurality of intersections of the scanning line and the signal line, respectively. A current is supplied to the light emitting element by an active element, light emission corresponding to pixel data is performed, and a method of driving an electronic display for displaying an image corresponding to an input video signal, comprising: data for determining a signal level of the pixel data. A determination step, and a signal level determined in the data determination step is:
A normal control step of driving the light emitting element to emit light by a current supplied from the active element to the light emitting element, based on a reference duty ratio, based on a reference duty ratio, when the predetermined value exceeds a predetermined value; If the signal level determined in the data determination step is equal to or less than the predetermined value, the current supplied from the active element to the light emitting element corresponding to the signal level based on a duty ratio larger than the reference duty ratio And driving the light emitting element to emit light.