KR20060091952A - Method and device for driving organic light emitting diode - Google Patents

Abstract

The present invention relates to a method and a device for driving an organic light emitting diode, wherein output pulses of a pulse width modulation (PWM) method output in one horizontal period are output at intervals without outputting at the same time. This is to prevent the occurrence of distributed driving pulses by matching the end of the cycle.

To this end, the present invention is a method of driving an organic light emitting device or other display device using a pulse width modulation pulse driving method, the drive by setting the output reference time of the drive current in one horizontal period differently according to the column (column) The present invention provides an organic light emitting diode driving method and apparatus for outputting a pulse and driving an output reference time of a driving current for some pixels at an end time of one horizontal period, thereby solving a concentration phenomenon of current and providing a luminance difference. It is possible to improve the brightness of the display data of half gray scale while preventing display performance deterioration.

Organic light emitting diode (OELD), pulse width modulation (PWM) method, driving pulse, drive circuit (IC)

Description

Organic light emitting diode driving method and device {Method and Device for driving Organic Light Emitting Diode}

1 is a conceptual diagram of a general organic light emitting display device.

2 is a pulse waveform diagram of a pulse width modulation method used in a conventional organic light emitting diode driving method.

3 is a pulse waveform modulation driving pulse waveform diagram used in the conventional modified organic light emitting diode driving method.

4 is a pulse waveform diagram of a pulse width modulation method used in an organic light emitting diode driving method according to an embodiment of the present invention;

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for driving an organic light emitting diode (OLED), and more particularly, to a driver circuit of an organic electroluminescent device or other display device driven by a pulse width modulation method. The present invention relates to an organic light emitting diode driving method and apparatus capable of resolving a concentration of current flowing in the and improving a display performance of a half gray scale.

Generally, in the conventional organic light emitting diode, as shown in FIG. 1, the anode and the cathode are arranged in a matrix shape of columns and rows, and organic materials are formed at the intersections of each column and row. As a device that emits light from organic materials as it is deposited and flows in a row direction from a column, it emits light by itself and emits light, so a backlight device such as a liquid crystal display is not required. It has been largely used as a display device.

The conventional method of driving an organic light emitting diode is a method of supplying a pulse width modulation (PWM) driving pulse to each drive circuit, and supplying a scan signal to a cathode through a row drive circuit as shown in FIG. The column drive circuit supplies a pulse width modulated signal having a pulse width corresponding to the gray level to the anode as a drive signal, wherein the drive signal supplied to the column drive circuit is shown in the pulse waveform diagram of FIG. 2. The driving pulses for all columns (column1 to m) are output based on the start time t1 of one horizontal period (1H).

However, in this driving method, the pulse width modulation (PWM) type driving pulse concentrates the output of driving current for all columns at the start of one horizontal period. Therefore, the density of current shows a high density of 7 at the beginning of one horizontal period. While it is formed, it can be seen that only 1 flows at the end of one horizontal period. As such, the amount of current flowing out to the corresponding scan line increases in the initial stage of driving, and thus, a voltage drop largely occurs at the start of one horizontal line. As a result, such a voltage drop causes a drop in the operating voltage of the driving IC used in the drive circuit, which causes the driving IC to operate in a region having a large voltage dependence of current rather than a normal operating range.

Therefore, the current fluctuates even with a small voltage fluctuation, which causes a change in luminance, which causes a decrease in display characteristics such as luminance loading of the light emitting device.

On the other hand, Japanese Patent Application Laid-Open No. 2000-221943 (see the pulse waveform diagram of FIG. 3) is disclosed as one of the conventional technologies developed to solve the problem caused by the current concentration phenomenon.

According to the prior art, a first driver circuit for supplying a scan signal to a cathode and a second driver circuit for supplying a pulse width modulated signal having a pulse width according to a gray level to the anode as a drive signal, wherein the second driver circuit is provided. The start timing of the output of the drive signal supplied by the driver circuit is set to be different for each column, that is, dividing one horizontal period into predetermined sections and outputting driving pulses for each column sequentially at the start of each section. It is a driving method.

According to the conventional driving method, when the driving start time point is not the start time point of one horizontal line, a case where the driving pulse does not end until the end point of one horizontal period may occur. For example, as shown in the pulse waveform diagram of FIG. 3, the driving pulses for the fourth column (column 4) and the sixth column (column 6) of one horizontal period are driven until the end point of the one horizontal period. In this case, the driving pulse should be composed of distributed pulses so that the remaining current can be output from the beginning of one horizontal line.

However, such a prior art has a problem in that the configuration of the driving circuit is not only complicated, but also a difference in luminance occurs during distributed pulse driving and continuous pulse driving. That is, even if the current is output for the same time to express the same gray level, the driving pulses (constant pulses) for the third column (column 3) and the driving pulses (column 4) for the fourth column (column 4) of FIG. Pulse), the luminance is unlikely to be the same.

In addition, there is a problem in that the luminance difference due to the difference in the start time of the driving pulse occurs. That is, even if the current is output for the same time (the first and second column driving pulses of FIG. 3) to express the same gray level, the pulse (first column of FIG. 3) that starts outputting at the first section (time point t1) and If the start point of the driving pulse is different, such as the pulse (second column of FIG. 3) which starts output in the second section (time point t2), the luminance is not likely to be the same.

Therefore, the present invention has been made to solve the above-mentioned conventional problems, the present invention is to concentrate the current by outputting at a time interval without output pulse pulse modulation (PWM) drive pulses sent out in one horizontal period at the same time Then, for some pixels, the temporal reference of the driving pulse is set at the end of one horizontal period, and the driving pulse is output when the time for expressing the corresponding gray scale is secured so that the end point of the driving pulse is one horizontal period. By coinciding with the end of and using the drive mode alternately, it is possible to prevent the degradation of display performance due to the luminance difference that may occur due to other reasons such as distributed drive pulse or drive pulse output start time instead of continuous drive pulse. Organic light emitting diode driving room for improving the brightness of grayscale display data Its purpose is to provide a law and a device.

 One embodiment of the present invention for achieving the above object is a method for driving an organic light emitting device or other display device using a pulse width modulation type driving pulse, the output reference time of the drive current in one horizontal period The present invention provides a method of driving an organic light emitting diode, in which a driving pulse is output by setting differently according to a column and driving the output reference time of the driving current for some pixels at the end time of one horizontal period.

In particular, the driving method according to an embodiment of the present invention preferably divides the driving current into a start mode in which the output reference time of the drive current is set to the start time of one horizontal cycle and end mode set to the end time of one horizontal cycle. Do.

In addition, the driving method according to the embodiment of the present invention outputs driving pulses in the start mode to as many pixels as half of one horizontal period, and outputs driving pulses of the end mode to the other half of the pixels. Other embodiments may be configured.

In the driving method according to each embodiment of the present invention, the driving pulse of the end mode is output when the time for representing the gray scale is secured so that the end point of the driving pulse always coincides with the end point of one horizontal period. It would be desirable to do so.

In addition, the driving method according to the exemplary embodiment of the present invention may operate by changing the operation mode of the driving pulse for each adjacent pixel or adjacent unit pixel, or by changing the operation mode of the driving pulse for each adjacent pixel or adjacent unit pixel. Another embodiment may be configured by changing the operation mode of the driving pulse for each row).

In addition, the driving method according to the embodiments of the present invention alternates with respect to adjacent frames in such a manner that, in driving a single pixel, a driving pulse in the start mode is output in one frame and an end mode driving pulse is output in the next frame. Change the operation mode of the driving pulse, change the operation mode of the driving pulse for each unit pixel of each of the red (R) / green (G) / blue (B), or drive the red (R) / green ( Another embodiment may be configured by a method in which an operation mode of the driving pulse is changed for each pixel of which three unit pixels of G) / blue (B) are combined to form one display unit.

In addition, an organic light emitting diode driving apparatus including a second drive circuit for outputting a pulse width modulation driving signal to an anode of an organic light emitting diode or other display device may be implemented by the driving method according to each embodiment of the present invention. .

These objects, features and advantages of the present invention will be more readily understood by reference to the accompanying drawings and the following detailed description.

In the following specification, a method of driving an organic light emitting diode will be described as an example. However, the main concept of the present invention is applicable to other display devices using a pulse width modulation (PWM) type driving pulse. The technical spirit of the present invention is not limited thereto, but may be variously modified and modified by those skilled in the art.

Hereinafter, the configuration and operation of the preferred embodiment of the present invention with reference to the accompanying drawings in detail as follows.

4 is a pulse diagram showing a pulse width modulation driving pulse waveform used in an organic light emitting diode driving method according to an exemplary embodiment of the present invention, which is an organic light emitting diode driving method according to an exemplary embodiment of the present invention. The output reference time of the current is set differently according to columns 1 to 7 to illustrate the state of outputting a driving pulse and the concentration of current evenly distributed in one horizontal period. In this case, looking at the concentration of the current, it can be seen that the current flows relatively uniformly over one horizontal period. In this example, the driving currents of the first and second columns during one horizontal period (1H) are three gradations (L3), respectively, and the driving currents of the third, fourth, and sixth columns are five gradations (L5), respectively, and the driving currents of the fifth column are two. The gradation L2 and the driving current in the seventh column exemplify the case of the seventh gradation L7. In particular, an arrow indicates a reference time point and direction of the gradation calculation.

In the driving method according to the present invention illustrated in FIG. 4, some pixels, that is, a first column (column 1), a third column (column 3), a fifth column (column 5), and a seventh column (column 7) The output reference time of the drive current with respect to the start time of one horizontal period is set for the other pixels, that is, the second column (column 2), the fourth column (column 4), and the sixth column (column 6). The output reference time of the drive current is driven at the end of one horizontal period. Here, the pulse in which the output reference time of the drive current is set to the start time of one horizontal period is called a pulse in the start mode (S mode), and the pulse in which the output reference time of the drive current is set to the end time of one horizontal period. Is referred to as an end mode pulse.

The driving method according to an embodiment of the present invention is a method of outputting driving pulses of the start mode to as many pixels as half of one horizontal period and outputting driving pulses of the end mode to the other half of the pixels, in particular, the start. In the mode and the end mode, it is possible to drive the divided drive or the drive mode alternately. In this case, it is preferable that the driving pulse of the end mode is output at a time point when the time for representing the gray scale is secured so that the end point of the driving pulse always coincides with the end point of one horizontal period.

In addition, the driving method according to each embodiment of the present invention may be configured by changing the operation mode of the driving pulse for each adjacent pixel or adjacent unit pixel.

In addition, the driving method according to the embodiment of the present invention is another method of changing the operation mode of the driving pulse for each adjacent row (row) by changing the operation mode of the driving pulse for each adjacent pixel or adjacent unit pixel. An example configuration is possible.

In addition, the driving method according to the embodiments of the present invention alternates with respect to adjacent frames in such a manner that, in driving a single pixel, a driving pulse in the start mode is output in one frame and an end mode driving pulse is output in the next frame. Change the operation mode of the driving pulse, change the operation mode of the driving pulse for each unit pixel of each of the red (R) / green (G) / blue (B), or drive the red (R) / green ( Another embodiment can be configured by a method in which the operation mode of the driving pulse is changed for each pixel forming a display unit in which three unit pixels (G) / blue (B) are added together.

The above-described driving method outputs start mode (S mode) drive pulses to as many pixels as half of one horizontal period, and output modes of end mode (E mode) drive pulses to the other half pixels. It can be implemented by any one of these, namely, the driving method illustrated in Tables 1-4.

Table 1 below shows that the adjacent unit pixels change from E to S to E mode starting from S mode, i.e., in odd columns (1, 3, ..., m-1) regardless of rows. The driving pulse of the start mode (S mode) is output and the driving pulse of the end mode (E mode) is output to the next even columns (2, 4, ..., m).

       Column Row One 2 3 4 ... m-1 m One S E S E ... S E 2 S E S E ... S E 3 S E S E ... S E 4 S E S E ... S E ... ... ... ... ... ... ... ... n-1 S E S E ... S E n S E S E ... S E

Table 2 below shows that starting from E mode, adjacent unit pixels change from S → E → S mode, i.e., end to odd columns (1,3, ..., m-1) regardless of rows. The driving pulse of the mode (E mode) is output and the driving pulse of the start mode (S mode) is output to the next even columns (2, 4, ..., m).

       Column Row One 2 3 4 ... m-1 m One E S E S ... E S 2 E S E S ... E S 3 E S E S ... E S 4 E S E S ... E S ... ... ... ... ... ... ... ... n-1 E S E S ... E S n E S E S ... E S

Table 3 below shows the driving pulse of the start mode (S mode) in the odd columns (1, 3, ..., m-1) in the first row (row 1), and then the even columns (2, 4, ..., m) outputs the driving pulse of the end mode (E mode), and in the second row (row 2), the end mode (E mode) to the odd columns (1, 3, ..., m-1) This method alternates the method of outputting the driving pulse of and outputting the driving pulse of the start mode (S mode) to the next even columns (2, 4, ..., m).

       Column Row One 2 3 4 ... m-1 m One S E S E ... S E 2 E S E S ... E S 3 S E S E ... S E 4 E S E S ... E S ... ... ... ... ... ... ... ... n-1 S E S E ... S E n E S E S ... E S

Table 4 shows output pulses of the end mode (E mode) in odd columns (1, 3, ..., m-1) in the first row (row 1), and then the even columns (2, 4, ..., m) outputs driving pulses in the start mode (S mode), and in the second row (row 2), the odd mode columns (1, 3, ..., m-1) are used in the start mode (S mode). It outputs the driving pulse of and outputs the driving pulse of the end mode (E mode) to the next even columns (2, 4, ..., m).

       Column Row One 2 3 4 ... m-1 m One E S E S ... E S 2 S E S E ... S E 3 E S E S ... E S 4 S E S E ... S E ... ... ... ... ... ... ... ... n-1 E S E S ... E S n S E S E ... S E

In particular, the driving method according to the embodiment of the present invention may be performed by changing the operation mode of the driving pulse for each adjacent pixel or adjacent unit pixel, or by changing the operation mode of the driving pulse for each adjacent pixel or adjacent unit pixel, row) a method in which the operation mode of the driving pulse is changed for each driving method, or in the case of driving a single pixel, an adjacent frame by outputting a driving pulse in the start mode in one frame and an driving pulse in the end mode in the next frame. Alternately, the operation mode of the driving pulse is alternately driven, or the operation mode of the driving pulse is changed for each unit pixel of each of red (R), green (G), and blue (B), or red (R). The driving mode is changed by changing the operation mode of the driving pulse for each pixel of which three unit pixels of green, green, and blue are combined to form one display unit. Are each embodiment is possible as well in a way. That is, the present invention uses the driving method of Table 1 in one frame and the driving method of Table 2 in another frame, or the driving method of Table 3 in one frame. It is also possible to use a method using the driving method shown in Table 4 in the other frame.

In the driving method according to each embodiment of the present invention, the driving pulse of the end mode (E mode) is output at a time point when the time for expressing the corresponding gray scale is secured so that the end point of the driving pulse is always one horizontal period. It would be desirable to match the end point.

According to the driving method of the present invention as described above, in order to solve the concentration phenomenon of the current, the driving pulse corresponding to a part of the pixel is not timed at all at the start time of one horizontal period. In this case, the current is sent to as many pixels as half of the pixels at the beginning of one horizontal cycle, and the current is sent to the other half of the pixels based on the end of one horizontal cycle time. With the temporal reference at the end of one horizontal period, some pixels driven in the end mode have the end point of the driving pulse always coincident with the end of one horizontal period, so that the concentration of current during one horizontal period is shown in FIG. As shown in the drawing, the distance is less than half of that of the conventional driving method (see also the pulse waveform of FIG. 2). The effect is expected for minor but it is possible to expect a significant effect on the display data of the gray level of less.

The circuit configuration is simplified because only the starting point of each driving pulse is determined, and there is no scattered pulse. Therefore, the luminance difference is not generated due to the occurrence of distributed pulses. It becomes possible.

That is, the start mode (S mode) is the same as the conventional PWM driving method, and the end mode (E mode) can be driven by setting the start point of the driving pulse to 'total number of gray scales to be displayed'.

For example, in the case where the entire gradation classification is performed in eight steps, to express gradation 5 of the fourth column (column 4) and the sixth column (column 6) of FIG. 4, 8-5 = 3, that is, the third The drive can be started from the time unit t3.

In this way, according to the above driving method, since only continuous pulses are generated, the problem of display performance deterioration due to the luminance difference as described in Japanese Patent Laid-Open No. 2000-221943 does not occur.

In addition, in the present invention, since the start point of the driving pulse is different, the luminance difference as in the Japanese Patent Laid-Open Patent, that is, the first column (column 1) of FIG. 4 is the start mode (S mode) and the second column (column 2) is the end. Mode (E mode), the third column (column 3) is again the start mode (S mode), the fourth column (column 4) is the end mode (E mode), so even if the same gradation (same pulse width), the luminance difference appears. However, in the present invention, since the start mode (S mode) and the end mode (E mode) are alternately used for the same unit pixel or the same pixel, such luminance differences are eventually canceled.

According to the present invention, it is possible to solve the phenomenon that the current is concentrated at a certain time point by outputting the pulse width modulation (PWM) type driving pulses output in one horizontal period at a time point instead of simultaneously outputting them.

In addition, according to the present invention, for some pixels, the time reference of the driving pulse is set at the end of one horizontal period, and the driving pulse is output when the time for expressing the gray scale is secured so that the end point of the driving pulse is one horizontal. By matching the end of the period and enabling the driving mode to be used alternately for the same unit pixel or for the same pixel, the luminance at which the output start time of the distributed driving pulse or the driving pulse, rather than the continuous driving pulse, may occur for other reasons. It is possible to obtain an effect of improving the brightness of the display while preventing display performance degradation due to the difference.

Claims (10)

In the method for driving the organic light emitting device or other display device using a pulse width modulation pulse driving method, The driving pulse is output by setting the output reference time of the driving current in one horizontal period differently according to the column, but driving the output reference time of the driving current for some pixels at the end time of one horizontal period. An organic light emitting diode driving method. According to claim 1, wherein the pulse width modulation system driving pulse, An organic light emitting diode driving method, characterized in that the driving current is divided into a start mode in which the output reference time is set as the start time of one horizontal period and an end mode in which the end time of one horizontal period is set. The method of claim 2, A method of driving an organic light emitting diode, comprising: driving pulses in a start mode are output to as many pixels as half of one horizontal period, and driving pulses of an end mode are output to the other half pixels. The method of claim 3, wherein The driving pulse of the end mode is output when the time for expressing the gray level is secured so that the end point of the driving pulse is always coincident with the end point of one horizontal period. The method of claim 3, wherein And driving the operation mode of the driving pulse for each adjacent pixel or adjacent unit pixel. The method of claim 3, wherein And changing the operation mode of the driving pulse for each adjacent row while changing the operation mode of the driving pulse for each adjacent pixel or adjacent unit pixel. The method of claim 3, wherein In driving the same unit pixel or the same pixel, the operation mode of the driving pulse is alternately changed for adjacent frames by outputting the driving pulse of the start mode in one frame and the driving pulse of the end mode in the next frame. Driving an organic light emitting diode, characterized in that for driving. The method of claim 7, wherein The red (R), green (G), blue (B) of the organic light emitting diode driving method, characterized in that for driving the driving mode of the drive pulse for each unit pixel. The method of claim 7, wherein A method of driving an organic light emitting diode, characterized in that the operation mode of the driving pulse is changed for each pixel of which three unit pixels of red (R), green (G), and blue (B) form one display unit. An organic light emitting diode comprising a second drive circuit for outputting a pulse width modulation driving signal to an anode of an organic light emitting element or other display element by the method according to any one of claims 1 to 9. Drive system.

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