KR20030073581A - An electroluminescence display device and a method for compensating for pixel voltage distortion in driving the device - Google Patents

Abstract

PURPOSE: An electro-luminescence display device and a method for compensating distortion of a pixel voltage in a driving process are provided to obtain the uniformity of luminance by calculating and generating a pixel voltage according to the amount of data and providing the pixel voltage to a panel. CONSTITUTION: An electro-luminescence display device includes a logic and image signal processing portion(1), a voltage generation portion(2), and a panel(3). The logic and image signal processing portion(1) calculates and generates a pixel voltage which is controlled according to a variation of data to frame and generates a logic signal to control a displaying operation. The voltage generation portion(2) converts the pixel voltage of the logic and image signal processing portion(1) to an analog signal and amplifies the analog signal. The panel(3) is used for performing the displaying operation. The logic and image signal processing portion(1) includes a memory(12) and a CPU(central Processing Unit)(11).

Description

EL ELECTROLUMINESCENCE DISPLAY DEVICE AND A METHOD FOR COMPENSATING FOR PIXEL VOLTAGE DISTORTION IN DRIVING THE DEVICE}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electroluminescence display device known as an EL element, and more particularly to an electroluminescence display element that compensates for pixel voltage by a compensation algorithm and pixel voltage distortion during its driving. It is about how to compensate.

An electroluminescent display element is a display element using the phenomenon which light emission is performed by applying an electric field to the fluorescent substance apply | coated on the transparent glass film, ie, electroluminescence. Since the light emitting sheet has a small thickness, the electroluminescent display device can be manufactured in an ultra-thin film and a flat surface, and operates at a low voltage to drastically reduce power consumption, and thus its application as a display device of a terminal for a monitor, PDA, and IMT-2000. The width is gradually expanding.

In such an electroluminescent display, the pixel voltage is distorted according to the amount of change of data per frame input for display, and thus a phenomenon in which luminance is uneven in the panel as a whole occurs. This is a phenomenon in which when the amount of data is large, that is, when the pixels are turned on a lot, the current value applied to the resistance of each pixel drops (this is called “IR Drop”) and the pixel voltage drops gradually and the luminance of the entire screen becomes uneven. . Thus, it is necessary to maintain the pixel voltage appropriately in accordance with the amount of data per frame to be input so as to display uniform picture quality.

Meanwhile, a common voltage compensation circuit for compensating for distortion of pixel voltage in a liquid crystal display has been disclosed in Korean Patent Publication No. 1998-21034 (published date: June 25, 1998). In the common voltage compensation circuit, a method of solving a problem in which a pixel voltage drop occurs due to a change in temperature and data per frame, and thus, flicker, in which image quality becomes irregular, is as follows. The difference is calculated by inputting a data voltage to a reference pixel at which a constant potential is applied to the gate electrode and an actual pixel driven in synchronization with the gate scan line of the liquid crystal display. The difference is applied in addition to the common voltage generator to maintain the potential difference between the pixel electrode and the common electrode of the liquid crystal panel. As a result, the voltage applied to the liquid crystal panel becomes constant so that generation of flicker can be significantly reduced.

However, since the conventional patent is a method of calculating and feeding back a potential difference of a liquid crystal panel to maintain a constant voltage in addition to an existing voltage value, there is a problem that a time delay occurs in outputting data, as well as a voltage compensation method. This complexity has a problem that the voltage compensation circuit is complicated.

The present invention has been made under the technical background as described above. The voltage suitable for the amount of data per frame input for display operation is calculated in advance by the algorithm proposed in the present invention, and the calculated voltage is directly provided to the EL element panel. It is therefore an object of the present invention to provide an electroluminescent display device capable of compensating pixel voltage distortion and a method for compensating pixel voltage distortion during its driving.

1 is an overall configuration diagram of an electroluminescent display element driving system according to the present invention.

2 is a flowchart of a pixel voltage distortion compensation algorithm according to the present invention.

(Explanation of symbols for the main parts of the drawing)

1: Logic and video signal processor 11: CPU

12 memory 2 voltage generator

21: D / A converter 22: current amplifier

3: panel

Electroluminescent display device driving method of the present invention for achieving the above object,

A logic and image signal processor configured to calculate and generate a pixel voltage so as to be adjusted according to a change in an input data amount per frame, and to generate and output a logic signal for driving a display operation;

A voltage generator which converts the pixel voltage output from the logic and image signal processor into an analog signal form and then amplifies the signal level to a predetermined level; And,

And an EL element panel which performs a display operation according to the pixel voltage output from the voltage generator and the logic signal output from the logic and image signal processing unit.

In the present invention described above, the pixel voltage is calculated and generated according to the change in the amount of data per frame input for the display operation, and the pixel voltage is appropriately maintained according to the amount of data per frame input by providing the pixel voltage directly to the panel. This makes it possible to realize uniformity in luminance.

The objects, technical configurations, and effects thereof of the present invention described above will become more apparent from the following description of the embodiments.

Hereinafter, with reference to the accompanying drawings will be described in detail a preferred embodiment of the present invention.

First, the electroluminescent display element driving system according to the present invention will be described with reference to FIG. 1.

1 shows the overall configuration of an electroluminescent display element driving system according to the present invention.

As shown in FIG. 1, the electroluminescent display element driving system according to the present invention comprises a logic and image signal processor 1, a voltage generator 2, and an EL element panel 3. As shown in FIG. The logic and image signal processor 1 includes a central processing unit (CPU) 11 and a memory 12. The voltage generator 2 includes a digital / analog converter 21 and a current amplifier. It consists of 22.

The memory 12 may be embodied as a ROM, which may be internal or external to the CPU 11, and stores an algorithm for calculating a pixel voltage for an input data amount per frame. When power is supplied and data for a display operation is input, an algorithm stored in the memory 12 is loaded and the CPU 11 executes this algorithm. The contents of this algorithm will be described later in detail with reference to the flowchart of FIG. 2. The CPU 11 calculates a pixel voltage for the data amount per frame input by the algorithm and outputs the pixel voltage to the voltage generator 2, while generating a logic signal for controlling the panel. Output to In Fig. 1, reference numeral A denotes a pixel voltage in the form of digital data, reference numeral B denotes a logic signal, and reference numeral C denotes a pixel voltage converted into an analog signal.

The pixel voltage A output from the CPU 11 is input to the digital-to-analog converter 21 of the voltage generator 2 in the form of digital data and converted into an analog signal. The signal level is then amplified to the level required for the panel by the current amplifier 22 and then applied to each pixel line of the panel 3. The panel 3 performs the display operation by the logic signal B and the pixel voltage C described above.

Next, a method of compensating pixel voltage when driving the EL display device according to the present invention will be described with reference to FIG. 2.

In the present invention, an algorithm for compensating for the distortion of the pixel voltage according to the amount of data per frame input for the display operation of the electroluminescent display is proposed. This algorithm, which solves the problem of low luminance when the amount of data is large and high luminance when the amount of data is adapted, generates a voltage suitable for the pixel according to the amount of data change per input frame, and applies this voltage to the EL element panel to achieve uniformity. Luminance can be obtained and image quality can be improved.

The algorithm can be represented by the following equation.

In the above equation, VDD _{(n + 1)} is the final pixel voltage, D _n is an average value of the n th frame data, D _{n + 1} is an average value of the n + 1 th frame data, and VDD _(n) is Initial voltage value for the n-th frame data average value.

According to the above equation, when the n + 1 th data amount is larger than the immediately preceding n th data amount, the final pixel voltage VDD _{(n + 1} ) is higher than the initial voltage VDD _(n) , In this case, the final pixel voltage VDD _{(n + 1} ) is lower than the initial voltage VDD _(n) . Thus, an appropriate voltage can be calculated and applied to the pixels of the panel 3 according to the amount of data input for the display operation.

Next, a detailed process of calculating the pixel voltage VDD _{(n + 1)} according to the above equation will be described based on the flowchart of FIG. 2.

When the algorithm stored in the program form in the memory 12 is loaded, the operation is started (S1). The n-th and n + 1-th data average values of the input data for the display operation are input (S2). Subsequently, the (D _{n + 1} -D _n ) / D _n part of the above equation is calculated (S3). Meanwhile, while the steps S2 to S3 are in progress, the initial pixel voltage VDD _(n) for the nth data is input (S4). Then, the final pixel voltage VDD _{(n + 1} ) is calculated using the initial pixel voltage input in step S4 (S5), which is the same as the above-described equation. The final pixel voltage VDD _{(n + 1)} obtained by this step is output from the logic and video signal processor 1 to the voltage generator 2 (S6), and then execution of the program is terminated ( S7).

As described above, according to the present invention, the pixel voltage is calculated and generated in accordance with the change of the amount of data input for the display operation, and the pixel voltage is input in accordance with the amount of data per frame input by directly providing the pixel voltage to the panel. By maintaining the voltage appropriately, uniformity in luminance can be realized. In addition, by calculating the voltage corresponding to the amount of data per input frame by the algorithm proposed in the present invention and providing the calculated voltage directly to the panel, it is possible to reduce the time delay of the data output compared to the prior art and voltage compensation Simplify the way.

Claims (7)

A logic and image signal processor configured to calculate and generate a pixel voltage so as to be adjusted according to a change in an input data amount per frame, and to generate and output a logic signal for controlling a display operation; A voltage generator which converts the pixel voltage output from the logic and image signal processor into an analog signal form and then amplifies the signal level to a predetermined level; And, And a panel configured to perform a display operation according to a pixel voltage output from the voltage generator and a logic signal output from the logic and image signal processor. The method of claim 1, The logic and image signal processor A memory storing an algorithm for pixel voltage calculation; And, And a central processing unit for calculating a pixel voltage according to an algorithm stored in the memory and generating a logic signal for controlling a display operation of the panel. The method of claim 1, The voltage generator A digital / analog converter for converting the pixel voltage output from the logic and image signal processor into an analog signal in the form of digital data; And, And a current amplifier for amplifying the signal level of the pixel voltage output from the digital / analog converter to a level required by the panel. The method of claim 1, The pixel voltage of the logic and image signal processor is calculated by the following equation. Where VDD _{(n + 1)} is the pixel voltage for the n + 1 th data value, D _n is a representative value of the n th frame data, D _{n + 1} is a representative value of the n + 1 th data, VDD _{(n )} Is the initial pixel voltage value for the nth frame data value) The method of claim 5, And a representative value of the n th and n + 1 th frame data is an average value. A first step of receiving data of an n th frame and an n + 1 th frame among data input for a display operation and extracting representative values thereof; A second step of subtracting the representative value of the n th frame data from the representative value of the n + 1 th frame data obtained in the first step, and dividing the value by the representative value of the n th frame data; A third step of measuring an initial voltage for n-th frame data in parallel with the first and second steps; A fourth step of calculating a pixel voltage by multiplying an initial voltage of the n-th frame data measured in the third step by the result obtained in the second step and adding the multiplied result to an initial pixel voltage of the n-th frame data. ; And, And a fifth step of outputting the pixel voltage obtained in the fourth step. The method of claim 5, And a representative value of the n th and n + 1 th frame data is an average value.