JP2001092410A - Driving device for el display device and gradation display method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress flickers to be generated at the time of performing assigning intensity levels limiting the number of light emissions of an EL element per prescribed fields in the EL driving device of a reversal driving system. SOLUTION: At the time of making respective pixels (EL elements) of an EL display device emit lights, the driving device applies driving voltages for light emission of a positive and a negative to each EL element in a horizontal scanning period. Consequently, when the device performs assigning intensity levels limting the number of light emissions of the EL element by making plural fields a display period, it is unnecessary to turn off the EL element in a two frame unit like in the conventional device and it is possible to turn off the EL element in one frame unit. As a result, the light emitting cycle at the time of performing the assigning intensity levels can be made shorter as compared with that in the conventional device of a field inversion driving system and flickers are suppressed from being generated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving device suitable for gradation display of an EL display device using an EL (electroluminescence) element which is a capacitive element of an AC drive type, and to a driving device using the driving device. The gray scale display method used.

[0002]

2. Description of the Related Art Conventionally, as a driving device for an EL display device, as shown in FIG.
Either positive or negative drive voltage for light emission is alternately applied to the EL elements (all illuminated pixels) to be turned off for each frame in which the display of one screen on the display device is completed. There is known a so-called field inversion drive type driving device that displays a desired image on an EL display device by prohibiting the application of a driving voltage for light emission to an EL element (non-light emitting pixel) to be turned off. (See, for example, Sharp Corporation, Sharp Technical Report, 1987, No. 38).

[0003] Also, pixels (EL) constituting an EL display device are used.
As a gradation display method in which the luminance is changed for each element, a plurality of continuous frames are defined as one display period, during which EL display is performed.
There are known methods for limiting the number of times the element emits light (for example, see Japanese Patent Application Laid-Open Nos. 60-160273 and
2-172396, etc.).

[0004]

In this gradation display method, the display data for light emission inputted to the driving device is thinned out (in other words, the display data for light emission is replaced with the display data for non-light emission (non-display data). ), The average luminance of the EL element per a plurality of frames, which is one display period, is reduced step by step. This gradation display method is applied to the above-described field inversion drive type driving device. In this case, the display data for light emission is 2
It is necessary to thin out each frame.

That is, since the EL element is of the AC drive type, the EL element cannot emit light even when the light-emitting drive voltage of the same polarity is continuously applied. On the other hand, in the driving device of the field inversion driving method, the polarity of the driving voltage for light emission applied to the EL element is switched every frame. For this reason, in the field inversion drive type driving device, when the display data for light emission is thinned out in one frame unit for gradation display, the drive for light emission applied to the EL element to cause the EL element to emit light is performed. The polarity of the voltage does not change, and the EL element cannot emit light in the next frame in which the EL element should emit light, as well as in the frame in which the display data for light emission is thinned out for gradation display. Therefore, when the above-mentioned gradation display method is applied to a drive device of a field inversion drive system, it is necessary to thin out the display data for light emission inputted to the drive device in units of two frames.

However, when the display data for light emission is thinned out in units of two frames in this manner, the luminance of the EL element changes at a rate obtained by thinning out the display data for light emission. The display screen flickers (so-called flicker) due to the period of two frames.
There is a problem that the occurrence of the problem easily occurs.

For example, as shown in FIG. 4, in the case of a halftone pixel in which the number of times the EL element emits light during one display period is halved, the EL element can be switched between emitting and non-emitting in units of two frames. , And the average luminance becomes し て corresponding to the ratio of the number of times of light emission, but the period (light emission period) from the first emission of the EL element to the next light emission after the non-light emission period However, since the cycle (period for one frame) becomes four times (period for four frames) instead of twice the period of full lighting, depending on the driving frequency of the EL display device,
The emission frequency of the EL element may enter the flicker region.

On the other hand, such a problem can be solved by increasing the driving frequency of the EL display device or shortening the period in which the EL element is turned off for gradation display (reducing the number of frames). However, in order to increase the driving frequency of the EL display device, an expensive driving circuit capable of high-speed operation is required. In particular, in an EL display device having a large number of pixels (in other words, the number of scanning electrodes), the driving frequency is increased. May not be possible. Further, in order to shorten the period in which the EL element is turned off for gradation display, for example, if the light-out period is limited to a period of two frames, there is a problem that the number of controllable gradations is limited. .

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and a driving apparatus of an inversion driving system for inverting the polarity of a driving voltage for light emission applied to an EL element and displaying an image on an EL display apparatus. In, EL during one display period
An object of the present invention is to make it possible to increase the limit of flicker that occurs when performing gradation display in which the number of light emission times of an element is limited, as compared with the related art.

[0010]

According to a first aspect of the present invention, there is provided a driving apparatus for an EL display device, comprising: a plurality of scanning electrodes of an EL display device; A scanning voltage is sequentially applied at a predetermined scanning timing, and the scanning voltage switching means changes the scanning voltage from positive to negative or negative within one horizontal synchronization period in which the scanning voltage is applied to the scanning electrodes. From the positive.

Further, display voltage applying means applies a display voltage corresponding to display data indicating light emission / non-light emission of each EL element to a data electrode of the EL display device, and display voltage switching means changes the display voltage. Change. As a result, a voltage for controlling light emission / non-light emission corresponding to the display data is applied to the EL element formed at the intersection of the data electrode to which the display voltage is applied and the scan electrode to which the scan voltage is applied. In addition, the polarity of the applied voltage is reversed to be positive or negative within one horizontal synchronization period synchronized with the scanning timing.

That is, the driving device of the EL display device according to the present invention applies the voltage to the EL element every frame in which the display of one screen of the EL display device is completed, like the driving device of the conventional field inversion driving method. Instead of inverting the polarity of the voltage, the polarity of the voltage applied to the EL element connected to the scan electrode is inverted during one horizontal synchronization period in which the scan voltage is applied to one scan electrode of the EL display device. is there.

For this reason, a positive or negative driving voltage for light emission is applied to an EL element serving as a lighting pixel in an EL display device in one frame.
Even if the application of the drive voltage for light emission is prohibited in frame units, the EL element can normally emit light in the next frame in which the application of the drive voltage for light emission is restarted.

On the other hand, the invention according to claim 2 is a gradation display method for performing gradation display of an EL display device using the driving device of the present invention (claim 1). The average luminance of the corresponding EL element is reduced stepwise by thinning out the application of the display voltage for light emission in units of one frame in which the display of one screen of the EL display device is completed.

That is, although the driving device of the present invention is a driving device of an inversion driving system in which the polarity of the driving voltage for light emission applied to the EL element is inverted and the EL element emits light,
Light emission / non-light emission of the EL element can be switched for each frame. Therefore, in the gradation display method according to the second aspect, instead of switching light emission / non-light emission of the EL element in units of two frames as in the case of performing gradation display using a field inversion drive type driving device, The gradation display is performed by switching the light emission / non-light emission of the EL element in units of one frame.

According to the above gradation display method,
By operating the driving device described above, the time during which light emission of the EL element is prohibited for gray scale display can be shortened as compared with the related art, and flicker can be suppressed. Therefore, according to the present invention (claims 1 and 2), EL within one display period
The generation limit of flicker caused by performing gradation display for limiting the number of times of light emission of the element can be increased as compared with the related art, and gradation display can be performed favorably.

According to the present invention (claims 1 and 2), gradation display can be performed by thinning out the light emission of the EL element in units of one frame, so that the occurrence of flicker can be suppressed. In addition, the display quality of an image can be improved by shortening one display period (the number of frames) at the time of gradation display (half of the conventional device if the number of gradations is the same).

[0018]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an entire configuration of a driving device of an EL display device according to an embodiment to which the present invention is applied.

As shown in FIG. 1, the EL display device 2
The plurality of rows of scan electrodes S-1, S-2,... Arranged in parallel on one side of the L light emitting layer, and on the other side of the EL light emitting layer, are orthogonal to and parallel to each scan electrode S. Are arranged in such a manner that a plurality of columns of data electrodes D-1, D-2,... Are arranged, and EL elements P11, P12. ing. For example,
An EL element P11 is provided in a region where the first row scan electrode S-1 and the first column data electrode D-1 intersect, and the second row scan electrode S-2 and the first column data are interposed. An EL element P21 is formed in a region where the electrode D-1 intersects.

Note that the suffixes "-1" and "-2" given to the code S representing the scanning electrodes represent the row numbers of the scanning electrodes S, and the suffixes "-1" given to the code D representing the data electrodes. Represents the column number of the data electrode D, and the suffixes “11” and “21” added to the symbol P representing the EL element are the scanning electrodes S forming the EL element.
And the row / column number of the data electrode D.

The driving device for driving the EL display device 2 includes the odd-numbered scan electrodes S-1, S-3,... And the even-numbered scan electrodes S-2, S-4,. Each of the scanning driver ICs 4 and 6 for applying a scanning voltage, the display driver IC 8 for applying a display voltage to the data electrodes D-1, D-2,. Scanning voltage supply circuits 10 and 20 for supplying a negative scanning voltage, a display voltage supply circuit 30 for supplying a display voltage for controlling emission / non-emission of the EL element P to the display driver IC 8, and a scanning driver IC 4 , 6 to control the timing of applying the scanning voltage to each scanning electrode S, and the timing of switching the scanning voltage supplied by the scanning voltage supply circuits 10 and 20 to the scanning driver ICs 4 and 6, etc.
A display timing control circuit 50 for controlling the timing of application of a display voltage to each data electrode D by the display driver IC 8 and the timing of switching the display voltage supplied to the display driver IC 8 by the display voltage supply circuit 30; It is composed of

In the driving device of this embodiment, the scanning driver ICs 4 and 6 function as scanning voltage applying means, and the display driver IC 8 functions as display voltage applying means. Although the detailed operation will be described later, the function as the scanning voltage switching means is realized by the scanning voltage supply circuits 10 and 20 and the scanning timing control circuit 40, and the function as the display voltage switching means is the display voltage supply means. This is realized by the circuit 30 and the display timing control circuit 50.

Here, the two scanning voltage supply circuits 1
One of the scanning voltage supply circuits 0 and 20 supplies a positive scanning voltage “+ Vr (for example, +250 V)” to the scanning driver ICs 4 and 6 via the positive voltage supply line L1. And a switching element (hereinafter referred to as a positive voltage supply switch) SWR1 for applying a positive scanning voltage “+ Vr” to the positive voltage supply line L1 and a positive voltage supply line L1 connected to the discharge voltage “VG”. (Hereinafter referred to as a positive voltage side ground switch) SWR2.

The discharge voltage "VG" is changed from 0 V (ground potential) to the voltage supply line L3 from the display voltage supply circuit 30.
Can be set to an arbitrary voltage up to “+ Vm”, but in this embodiment, the description will be made assuming that the ground potential (0 V) is used. Also, the other scanning voltage supply circuit 20
Supplies a negative scanning voltage “−Vr + Vm (for example,“ −Vr + Vm ”) to the scanning driver ICs 4 and 6 via the negative voltage supply line L2.
-205V), and a switching element (hereinafter referred to as a negative voltage supply switch) SWR3 for applying a negative scanning voltage "-Vr + Vm" to the negative voltage supply line L2, and a negative voltage supply line. A switching element (hereinafter referred to as a negative voltage side ground switch) SWR4 for grounding L2 to ground.

On the other hand, the display voltage supply circuit 30 is connected to the display driver IC 8 via a pair of voltage supply lines L3 and L4.
The two types of voltages “+ Vm (for example, +45 V)” and “0
V (in other words, ground potential) ”, a switching element (hereinafter referred to as a display voltage supply switch) SWC1 for applying a voltage“ + Vm ”to the voltage supply line L3, and a power supply line L3 And a switching element (hereinafter, referred to as a display-side grounding switch) SWC2 for grounding the power supply line to the ground. The other voltage supply line L4 is directly grounded to the ground (voltage 0 V).

Here, "Vr" and "Vm" are usually "Vr"
In the case of "r-Vm", the voltage value is set to be lower than the light emission start threshold voltage of the EL element P, and in the case of "Vr", the voltage value is set to be higher than the light emission start threshold voltage. Then, each of the voltage supply circuits 1
Each driver IC receiving power supply from 0, 20, 30
Reference numerals 4, 6, and 8 denote respective electrodes S-1 and S of the EL display device 2, respectively.
-3, S-2, S-4 ..., D-1, D-2 ... push-pull type switching circuits 4a-1, 4a
-3,..., 6a-2, 6a-4,..., 8a-1, 8a-2,. Driver circuits 4b, 6b, and 8b.

The switching circuits 4a, 6a, 8a in the driver ICs 4, 6, 8 are, for example, P-channel FETs (field-effect transistors) 4p, 6p, 8p and N Channel FE
T4n, 6n, and 8n.

In the scanning driver ICs 4 and 6, the switching circuits 4a and 6a respectively constitute 2
Of four FETs 4p, 4n, 6p, 6n
The sources of ET4p and 6p are connected to the positive voltage supply line L1 by N
The sources of the channel FETs 4n and 6n are connected to the negative voltage supply line L2, respectively.

In the display driver IC 8,
Two FETs 8p constituting each switching circuit 8a,
8n, the source of the P-channel FET 8p is connected to the voltage supply line L3, and the source of the N-channel FET 8n is connected to the voltage supply line L4 which is grounded.

The switching circuits 4a, 6
When the devices constituting the devices a and 8a are P-channel and N-channel FETs, both devices are composed of MOS-type FETs and have a parasitic diode that allows a current in a direction opposite to the current to be controlled to pass. Here, each switching circuit 4
a, 6a, and 8a can be constituted by not only a MOS FET but also a bipolar transistor or a thyristor. In these cases, since there is no parasitic diode, it is necessary to configure diodes for passing the current in the reverse direction.

Next, the scanning timing control circuit 40
Various control signals are generated based on a clock signal and an image display synchronization signal input from the outside, and output to the scanning driver ICs 4 and 6 and the scanning voltage supply circuits 10 and 20, thereby defining a horizontal synchronization period. Scan voltage “+ Vr” or “−Vr + Vm” at each predetermined scan timing
Is applied to the scan electrodes S-1 from the first row scan electrodes S-1.
Rows, third row,... Are sequentially switched to select a display row.
When the display row is selected (in other words, within one horizontal synchronization period), the polarity of the scanning voltage applied to the scanning electrode S of the selected display row is changed from the positive voltage “+ Vr” to the negative voltage “ −Vr + Vm ”or vice versa.

On the other hand, the display timing control circuit 50
The scanning timing control circuit 4
0 is read from an external image memory (a so-called VRAM) for one line of display data corresponding to the display row selected,
By outputting to the display driver IC 8, various control signals are generated based on a clock signal and a synchronization signal for image display input from the outside, and output to the display driver IC 8 and the display voltage supply circuit 30, A display voltage “+ Vm” or “0 V” corresponding to the display data is applied to each data electrode D-1, D-2,..., And synchronized with the switching of the polarity of the scanning voltage on the scanning timing control circuit 40 side. The display voltage applied to each data electrode D-1, D-2,... Is changed from "+ Vm" to "0V" or "0V" to "+ V".
m ”.

As described above, the driving apparatus of the present embodiment operates according to various control signals generated by the timing control circuits 40 and 50, and stores the display data stored in the external image memory in the EL display device 2. The corresponding two-dimensional image is displayed. Next, the operation of the driving device during the image display will be described with reference to a time chart shown in FIG.

Here, a case where the scanning voltage is switched from "+ Vr" to "-Vr + Vm" within one horizontal synchronization period will be described. First, a display period from the scan timing T1 to T2 when the scan timing control circuit 40 applies a scan voltage to the scan electrode S-1 in the first row (first row display period).
Will be described.

As shown in FIG. 2, the scanning timing T1
In the first row display period, the scanning timing control circuit 40 outputs a row selection signal to the scanning driver IC 4 to select the first row of the scanning electrodes S-1.
The scanning polarity switching signal PCrow output to each of the scanning driver ICs 4 and 6 is set to a high level.

Then, the scanning driver IC 4 turns on the P-channel FET 4p constituting the switching circuit 4a-1 corresponding to the scanning electrode S-1 in the first row, and turns on the scanning electrode S-1.
And the positive voltage supply line L1. At this time,
Each of the scanning driver ICs 4 and 6 turns off all the FETs connected to the other scanning electrodes S, and brings the other scanning electrodes into a floating state.

At the scan timing T1, the display timing control circuit 50 controls the light emission / non-light emission of each of the EL elements P11, P12,... Connected to the scan electrode S-1 in the first row. The display data for the line is read out from an external image memory, and the display data is output to the display driver IC 8 together with the latch command.
The display polarity switching signal PCcolm output to 8 is set to the high level.

Then, the display driver IC 8 latches one line of display data input from the display timing control circuit 50. According to the latched display data, if the EL elements P11, P12,... Of the first row connected to the data electrodes D-1, D-2,.
By turning on the n-channel FET 8n constituting the switching circuit 8a corresponding to the EL element P,
The data electrode D corresponding to the lighting pixel is connected to a voltage supply line L4 that is grounded. On the other hand, if the EL elements P11, P12,... Of the first row connected to the data electrodes D-1, D-2,. P channel FET8p
Is turned on, the data electrode D corresponding to the unlit pixel is connected to the voltage supply line L3.

At the scanning timing T1, each of the timing control circuits 40, 50 is connected to the corresponding one of the voltage supply circuits 10, 20,.
30 voltage supply switches SWR1, SWR3, SWC
1 is turned off, and the ground switches SWR2, SWR4, SW
C2 is turned on. As a result, the selected scanning electrode S-1 of the first row and all the data electrodes D-1, D-2,... Are both grounded to the ground, and the scanning electrode S-1 of the first row is grounded. Are discharged from the EL elements P11, P12,.

Next, when a predetermined time has elapsed from the scanning timing T1 (time t1), each of the timing control circuits 40, 5
0 turns on the voltage supply switches SWR1 and SWC1 and turns off the ground switches SWR2, SWR4 and SWC2. As a result, the positive scanning voltage "+ Vr" is applied to the scanning electrode S-1, the display voltage "+ Vm" is applied to the data electrode D corresponding to the unlit pixel, and the data electrode D corresponding to the lighting pixel is set. Is in a state of being grounded (voltage: 0 V). Therefore, after time t2, a positive voltage “+ Vr” whose absolute value is higher than the light-emission start threshold voltage is applied to the EL element P serving as a lighted pixel, and the EL element P enters a light-emitting state. E to be the unlit pixel
A voltage “Vr−Vm” having an absolute value smaller than the light emission start threshold voltage is applied to the L element P, and the EL element P
Is turned off.

In FIG. 2, the display data is display data for the data electrode D-1 in the first column. During the display period of the first row, the display data is at the high level, and the EL of the first row and the first column is displayed. The element P11 is a lighting pixel, and during the next display period of the second row, the display data is at the low level, and the EL element P21 of the second row and the first column is a non-lighting pixel.

Next, when a predetermined light emission time has elapsed after time t1 (time t2), each of the timing control circuits 40, 5
0 turns off the voltage supply switches SWR1, SWC1 and turns on the ground switches SWR2, SWR4, SWC2. As a result, the electric charges accumulated in the EL elements P11, P12,... Connected to the scanning electrode S-1 in the first row are discharged again.

Further, at an intermediate point (time point t3) from time point t2 to time point t4 at which a predetermined discharge time elapses, each of the timing control circuits 40 and 50 transmits the scanning polarity switching signal PC.
The row and display polarity switching signal PCcolm are inverted from High level to Low level, respectively.

Then, the scanning driver IC 4 turns off the P-channel FET 4p and the N-channel FET 4n that constitute the switching circuit 4a-1, thereby turning on the N-channel FET 4n.
The scan electrode S-1 is connected to the negative voltage supply line L2. The display driver IC 8 is provided with each switching circuit 8a.
Then, the FET 8p or 8n that has been on until now is turned off, and the FET 8p or 8n that has been off until now turns on. As a result, the data electrode D corresponding to the lighting pixel
Is connected to the voltage supply line L3, and the data electrode D corresponding to the unlit pixel is connected to the voltage supply line L4 grounded to the ground.

When the time t4 is reached, the timing control circuits 40 and 50 turn on the voltage supply switches SWR3 and SWC1 and turn off the ground switches SWR2, SWR4 and SWC2. As a result, a negative scanning voltage “−V” is applied to the scanning electrode S-1.
r + Vm ”is applied, the display voltage“ + Vm ”is applied to the data electrode D corresponding to the lit pixel, and the data electrode D corresponding to the unlit pixel is grounded (ground voltage: 0 V). Therefore, after the time point t4, a negative voltage “−Vr” having an absolute value higher than the light emission start threshold voltage is applied to the EL element P serving as a lighted pixel, and the EL element P is in a light emitting state. In addition, a voltage “−Vr + Vm” having an absolute value smaller than the light emission start threshold voltage is applied to the EL element P serving as a light-off pixel, and the EL element P enters a non-light emitting state.

Next, when a predetermined light emission time has elapsed since time t4 (time t5), each of the timing control circuits 40, 5
0 turns off the voltage supply switches SWR3, SWC1 and turns on the ground switches SWR2, SWR4, SWC2. As a result, the electric charges accumulated in the EL elements P11, P12,... Connected to the first-row scanning electrode S-1 are discharged again.

Next, after the time point t5, the next scanning timing T2 is at an intermediate point from the time point t5 to the time point t1 'at which the predetermined discharge time passes, and the display period is changed from the display period of the first line to the display period of the second line. Switch to. When the display period is switched to the display period for the second row at the scan timing T2, the scanning timing control circuit 40 selects the scan electrode S-2 for the second row with respect to the scanning driver IC6. Output a row selection signal to be driven, and each scanning driver IC
The scanning polarity switching signal PCrow output to
gh level. As a result, in the display period of the second row, the scanning driver IC 6 operates as the P-channel FET 6 that constitutes the switching circuit 6a-2 corresponding to the scan electrode S-2 of the second row.
With p turned on, the scan electrode S-2 is connected to the positive voltage supply line L1. At this time, each of the scanning driver ICs 4 and 6 is connected to another FE connected to another scanning electrode S.
T is all turned off, and the other scanning electrodes are brought into a floating state.

At the scanning timing T2, the display timing control circuit 50 controls the light emission / non-light emission of each of the EL elements P21, P22,... Connected to the scanning electrode S-2 in the second row. The display data for the line is read out from an external image memory, and the display data is output to the display driver IC 8 together with the latch command.
The display polarity switching signal PCcolm output to 8 is set to the high level.

Then, the display driver IC 8 latches the display data as in the case of the scanning timing T1, and, in accordance with the latched display data, the n-channel FE of the switching circuit 8a corresponding to the EL element P serving as the issuing pixel.
By turning on T8n, the data electrode D corresponding to the lit pixel is connected to the voltage supply line L4, and the switching circuit 8a corresponding to the EL element P serving as the unlit pixel.
By turning on the P-channel FET 8p, the data electrode D corresponding to the unlit pixel is connected to the voltage supply line L3.

After that, each timing control circuit 4
0, 50 are the time points t1 ', t2', t3 ', t4', t
At 5 ', the display control for the EL elements P21, P22,... In the second row is performed by performing the same operation as the above-mentioned time points t1 to t5. After the end of the second-row display period (after the scanning timing T3), the scanning driver IC 4 is used for the odd-numbered rows in the same manner as in the first-row display period, and the scanning for the even-numbered rows is performed in the same manner as in the second-row display period. Using the driver IC 6
The display control is performed from the first line to the last line, and when the display control for one screen is completed, the display control is performed again sequentially from the first line.

Here, in the present embodiment, the odd-numbered rows and the even-numbered rows are scanned using the scanning driver ICs 4 and 6, respectively. However, all the rows may be scanned by either the scanning driver 4 or 6. It is possible. As described above, in the driving device of the EL display device 2 according to the present embodiment, the positive and negative light emitting drive voltages “+ Vr”,
In performing the inversion drive in which “−Vr” is alternately applied, the voltage applied to the EL element is changed every frame when the display of one screen of the EL display device is completed as in the conventional field inversion drive type driving device. Is inverted, the polarity of the voltage applied to the EL element is inverted during the display period for one scan electrode S of the EL display device 2 (in other words, during one horizontal synchronization period).

For this reason, according to the driving device of this embodiment,
As shown in FIG. 3, an EL element P serving as a lit pixel (all lit pixels) in the EL display device 2 has a positive and a negative within one frame.
Negative emission drive voltages “+ Vr” and “−Vr” are applied, and even if the emission display data is thinned out for each frame for gradation display, the application of the voltage to emit light is not performed. In the next frame restarted, the EL element P can normally emit light.

In FIG. 3, the driving voltage for light emission is
With reference to the light emission start threshold voltage of the EL element, if the absolute value of the voltage applied to the EL element is equal to or higher than the reference, the magnitude and polarity are indicated, and if the absolute value is equal to or less than the reference voltage, the magnitude is indicated as nil. And does not represent the actual applied voltage to the EL element. The same applies to the driving voltage for light emission shown in FIG.

Therefore, using the driving device of this embodiment, E
When performing gradation display for each pixel (each EL element P) constituting the L display device 2, the display data taken into the display timing control circuit 50 should be the display data for lighting (High level). , Non-display data for turning off (Low level)
Is set in units of one frame to adjust the number of times the EL element P emits light per predetermined frame.

When gradation display is performed in this manner, flicker can be made less likely to occur by shortening the period during which light emission of the EL element is inhibited for gradation display, as compared with the conventional apparatus. . That is, for example, the lower part of FIG. 3 corresponds to the light emission operation of the halftone pixel in the conventional device shown in FIG.
Although the light emission operation of the halftone pixel when the number of times of light emission of the EL element P during one display period is reduced to half is described, as shown in FIG. Since the ON / OFF of the EL element P can be switched for each frame, when the luminance of the EL element P is reduced to １ ／,
What is necessary is just to switch on / off of the EL element P for every frame. In this case, the cycle (light emission cycle) from the first emission of the EL element to the next light emission after the non-light emission period is twice as long as the full lighting cycle (period for one frame). , EL with half the emission cycle
The luminance of the element can be reduced.

Therefore, according to the driving apparatus of the present embodiment, the flicker occurrence limit can be increased as compared with the conventional apparatus, and gradation display can be performed satisfactorily. Further, according to the driving device of this embodiment, the EL element P
Since the gray scale display can be performed by thinning out the light emission in one frame unit, it is possible not only to suppress the occurrence of flicker but also to perform the gray scale display if the number of gray scales of the gray scale display is the same. The number of frames can be reduced to half that of the conventional one, and the display quality of an image can be improved.

When gradation display is actually performed, the display data representing the ON / OFF state of each pixel may be rewritten in units of one frame. There is no need to provide a simple circuit. As mentioned above, although one Example of this invention was described, this invention is not limited to the said Example, You can employ | adopt various aspects.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of an entire driving device of an EL display device according to an embodiment.

FIG. 2 is a time chart illustrating an operation of the driving device according to the embodiment.

FIG. 3 is an explanatory diagram showing a change in a drive voltage for light emission and a light emission operation of the element when the EL element is fully turned on / off and in a gradation display in the drive device of the embodiment.

FIG. 4 shows a conventional driving device in which all the EL elements are turned on.
FIG. 9 is an explanatory diagram illustrating a change in a light emission driving voltage and a light emission operation of an element when a light is turned off and a gradation is displayed.

[Explanation of symbols]

2 ... EL display device, 4,6 ... Scan driver IC, 4
a, 6a: switching circuit, 4b, 6b: driver circuit, 8: display driver IC, 8: switching circuit,
8b: driver circuit, 10, 20: scanning voltage supply circuit,
30: display voltage supply circuit, 40: scanning timing control circuit, 50: display timing control circuit.

Claims (2)

[Claims] 1. An EL light emitting layer, a plurality of scanning electrodes disposed in parallel on one side of the EL light emitting layer, and a plurality of scanning electrodes disposed on the other surface of the EL layer in a direction perpendicular to the scanning electrodes. An EL display device comprising one or more data electrodes and having an EL element serving as a pixel formed at each intersection of the data electrode and the scan electrode, wherein a positive / negative electrode is provided between the data electrode and the scan electrode. A driving device for an EL display device for displaying an image by alternately applying the voltages of the EL elements to selectively emit light of the EL elements, wherein a scanning voltage is sequentially applied to the plurality of scanning electrodes at a predetermined scanning timing. Scanning voltage applying means for applying; display voltage applying means for applying a display voltage corresponding to display data indicating light emission / non-light emission of each of the EL elements to the data electrode; and a period for applying the scan voltage to the scan electrode. Is one horizontal synchronization period Scanning voltage switching means for inverting the scanning voltage applied to the scanning electrode by the scanning voltage applying means from positive to negative or from negative to positive, and a display applied by the display voltage applying means to the data electrode. A driving device for an EL display device, comprising: display voltage switching means for changing a voltage. 2. The driving device according to claim 1, wherein
A method for performing gradation display of an L display device, wherein the application of a display voltage for light emission to the data electrode by the display voltage applying unit is performed in units of one frame in which display of one screen of the EL display device is completed. A gradation display method for an EL display device, wherein the average luminance of the corresponding EL element is reduced stepwise by thinning out.