KR100568598B1 - Method and apparatus for driving electro-luminescence display device - Google Patents

Abstract

The present invention relates to a driving device of an electro luminescence display element capable of preventing horizontal crosstalk and a driving method thereof.

The method of driving an electroluminescent display device includes a scan line in which a voltage level is changed by comparing first pixel data of a k-th scan line (k is a natural number) scan line of a display panel with second pixel data of a k + 1 th scan line. Determining by the voltage comparison controller; And generating a pixel signal corresponding to the determined scan line by the converter.

Description

TECHNICAL AND APPARATUS FOR DRIVING ELECTRO-LUMINESCENCE DISPLAY DEVICE}             

1 is a cross-sectional view schematically showing a conventional organic electroluminescent cell.

Fig. 2 is a plan view showing a passivated organic electroluminescent display element and its driving apparatus.

3 is a waveform diagram illustrating a driving signal of the organic electroluminescent display device illustrated in FIG. 2.

4 is a diagram illustrating a specific pattern including a window causing horizontal crosstalk in a conventional organic electroluminescent panel.

5 is a block diagram illustrating a driving apparatus of an electro luminescence display device according to an exemplary embodiment of the present invention.

6 is a block diagram illustrating in detail the voltage comparison controller shown in FIG. 5.

FIG. 7 is a circuit diagram illustrating in detail the DC-DC converter shown in FIG. 5.

<Description of Symbols for Main Parts of Drawings>

1 substrate 2 anode

3: hole injection layer 4: light emitting layer

5: cathode 10,110: display panel

12,112: data driver 14,114: scan driver

16,116: timing control unit 18,118: DC-DC converter unit

20,120: EL cell 122: voltage comparison control unit

124: PWM control unit 126: comparison unit

128: DAC

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electroluminescent display element, and more particularly, to a driving apparatus for an electroluminescent display element capable of preventing horizontal crosstalk and a driving method thereof.

Recently, various flat panel displays have been developed to reduce weight and volume, which are disadvantages of cathode ray tubes. Flat display devices include Liquid Crystal Display (LCD), Field Emission Display (FED), Plasma Display Panel (PDP) and Electro-luminescence (EL). Display elements;

PDP is most advantageous for large screens because of its relatively simple structure and manufacturing process, but it has the disadvantages of low luminous efficiency, low luminance and high power consumption. As LCDs are mainly used as display elements in notebook computers, demand is increasing. However, since LCD is manufactured by a semiconductor process, it is difficult to make a large screen and it is not a self-emitting device, so a separate light source is required and power consumption is large due to the light source. In addition, LCD has a disadvantage of high light loss and a narrow viewing angle due to optical elements such as a polarizing filter, a prism sheet, and a diffusion plate. EL display devices are classified into inorganic ELs and organic ELs, and have advantages of fast response speed and high luminous efficiency, luminance, and viewing angle. The organic EL display element is attracting attention as a next generation display element because it can display an image with a high luminance of tens of thousands [cd / m 2] with a voltage around 10 [V].

The organic EL cell forms an anode 2 made of a transparent conductive material on the substrate 1 as shown in FIG. 1, on which the hole injection layer 3, the light emitting layer 4 made of organic material, and a metal having a low work function are formed. The cathodes 5 made up are stacked. When an electric field is applied between the anode 2 and the cathode 5, the holes in the hole injection layer 3 and the electrons in the metal proceed toward the light emitting layer 4, respectively, and are combined in the light emitting layer 4. Then, the fluorescent material in the light emitting layer 4 is excited and transitions to generate visible light. At this time, the luminance becomes proportional to the current between the anode 2 and the cathode 5.

FIG. 2 is a diagram showing a driving device of an organic EL display element having a plurality of organic EL cells shown in FIG.

The driving apparatus of the organic EL display element shown in Fig. 2 includes: a display panel 10 having an EL cell 20; A scan driver 14 driving the scan line SL of the display panel 10; A data driver 12 driving the data line DL of the display panel 10; A timing controller 16 for controlling each of the scan driver 14 and the data driver 12 is provided.

The display panel 10 includes EL cells 20 that are arranged at intersections of the scan line SL and the data line DL and are equivalently represented by diodes. Each of these EL cells 20 is selected when the scan pulse SCAN is applied to the scan line SL and the positive data voltage Vdd supplied to the data line DL, which is an anode, as shown in FIG. 3. Light corresponding to the pixel signal DATA, that is, the current signal, is generated. That is, each of the EL cells 20 is supplied with a negative scan pulse SCAN to the scan line SL and a positive current according to the pixel signal DATA is applied to the data line DL, so that the forward voltage is increased. The EL cells 20 of the scan line SL that are caught emit light. In this case, the reverse direction voltage is applied to the EL cells 20 included in the unselected scan line SL so as not to emit light.

The scan driver 14 sequentially supplies the negative scan pulses SCAN to the plurality of scan lines SL, which are cathodes, to select the scan lines SL to display data.

The data driver 12 supplies a constant current signal synchronized with the scan pulse SCAN to each of the data lines DL using a constant current source (not shown).

The timing controller 16 supplies the scan control signal SCS to the scan driver 14 and also supplies the data control signal DCS to the data driver 12 together with the pixel data R, G, and B. FIG.

The DC-DC converter section 18 receives power from a power supply section (not shown) to generate voltages and currents required for driving the EL display elements. For example, the DC-DC converter 18 generates an input voltage Vbatt having a relatively low voltage level supplied from a power supply unit, and generates a base voltage Vcc having a relatively high voltage level.

When the conventional base pressure Vcc is lower than the data voltage Vdd required by the EL cell 20, the constant current source included in the data driver 10 cannot generate a desired constant current signal. In this case, since the current from the EL cell 20 passes through the scan line SL, the current from the EL cell 20 within the scan line SL exceeds a certain value and the line included in the scan line SL. Voltage drop due to resistance is generated. This voltage drop causes horizontal crosstalk as shown in FIG. That is, as shown in FIG. 4, an area including a window area BW implementing black gray and implementing white gray corresponding to the kth scan line SLk; A luminance difference is generated between the k-1 th and k + 1 th scan lines SLk-1 and SLk + 1 without including the window region BW and the region implementing the corresponding white gray. That is, horizontal crosstalk is generated in the region corresponding to the kth scan line SLk and implementing white gray, which is relatively brighter than the region implementing the remaining white gray.

Accordingly, it is an object of the present invention to provide a driving device of an EL display element and a driving method thereof which can prevent horizontal crosstalk.

In order to achieve the above object, a method of driving an electro luminescence display device according to an exemplary embodiment of the present invention may include the first pixel data of a k-th scan line (k is a natural number) and a k + 1 th scan line of a display panel. Comparing the two pixel data to determine a scan line whose voltage level is changed by the voltage comparison controller; And generating a pixel signal corresponding to the determined scan line by the converter.

Comparing the first pixel data of the k (k is a natural number) scan line of the display panel and the second pixel data of the k + 1th scan line, the voltage comparison controller determines whether the scan line having the changed voltage level is changed. Comparing the first and second pixel data in a comparison unit; And converting the pixel signal from the voltage-falling second pixel data by using the digital-to-analog converter when the voltage difference between the first and second pixel data is greater than or equal to the threshold by the comparator.

The generating of the pixel signal corresponding to the determined scan line by the converting unit includes increasing the voltage level of the pixel signal converted by the digital-to-analog converting unit by a predetermined range using a DC-DC converter. It features.

In order to achieve the above object, a driving apparatus of an electroluminescent display device according to the present invention comprises a display panel for displaying an image using an organic light emitting cell, and a k (k is a natural number) scan line of the display panel. A voltage comparison controller for comparing the first pixel data with the second pixel data of the k + 1th scan line to determine a scan line having a changed voltage level; And a converter configured to generate a pixel signal corresponding to the scan line determined by the voltage comparison controller.

The voltage comparison controller includes: a comparing unit which compares the first and second pixel data; And a digital-to-analog converter for converting the voltage-dropped second pixel data into a pixel signal when the voltage difference between the first and second pixel data is greater than or equal to a threshold by the comparator.

The converter is a DC-DC converter that raises the voltage level of the pixel signal converted by the digital analog converter by a predetermined range.

Hereinafter, exemplary embodiments of the present invention will be described with reference to FIGS. 5 to 7.

5 is a block diagram showing a driving apparatus of an organic EL display element according to the present invention.

The driving device of the organic EL display element shown in Fig. 5 includes a display panel 110 having an EL cell 120; A scan driver 114 driving the scan line SL of the display panel 110; A data driver 112 driving the data line DL of the display panel 110; A timing controller 116 for controlling each of the scan driver 114 and the data driver 112; A voltage comparison controller 122 is provided to compensate for luminance deviation between horizontal lines.

The display panel 110 includes EL cells 120 that are arranged at intersections of the scan line SL and the data line DL and are equivalently represented by diodes. Each of the EL cells 20 is selected when the scan pulse SCAN is applied to the scan line SL, which is a cathode, and is supplied with a positive data voltage (eg, supplied to the data line DL, which is a cathode). Light corresponding to the pixel signal DATA having Vdd, that is, the current signal is generated. That is, each of the EL cells 120 is supplied with a negative scan pulse SCAN to the scan line SL and a positive current according to the pixel signal DATA is applied to the data line DL, so that the forward voltage is increased. The EL cells 120 of the scan line SL that are caught emit light. In this case, the reverse direction voltage is applied to the EL cells 120 included in the unselected scan lines SL so that they do not emit light.

The scan driver 114 sequentially supplies the negative scan pulses SCAN to the plurality of scan lines SL to select the scan lines SL to display data.

The data driver 112 supplies a constant current signal to each of the data lines DL in synchronization with the scan pulse SCAN using a constant current source (not shown).

The timing controller 116 supplies the scan control signal SCS to the scan driver 14 and also supplies the data control signal DCS to the data driver 112 together with the pixel data R, G, and B. FIG.

As illustrated in FIG. 6, the voltage comparison controller 122 compares the voltage difference between the horizontal lines, and a digital-to-analog converter converting the pixel data of the current horizontal line into a pixel signal based on the comparison result. Analog Converter (DAC) unit 128 is included.

The comparator 122 includes previous pixel data PR, PG, and PB supplied to the EL cell 120 connected to the previous scan line, and current pixel data to be supplied to the EL cell 120 connected to the current scan line. Compare R, G and B). That is, when the voltage difference between the previous pixel data and the current pixel data compared by the comparison unit 122 is greater than or equal to the threshold, the voltage level supplied to the EL cell connected to the scan line SL by the resistance of the scan line SL. This is the case. On the other hand, in order to compare the previous pixel data (PR, PG, PB) and the current pixel data (R, G, B) may be further provided with a line memory that can store the pixel data in units of lines.

The DAC unit 128 converts the current pixel data R, G, and B, in which the voltage difference from the previous pixel data PR, PG, and PB is greater than or equal to the threshold, into the pixel signal Vdac, and feeds it back to the DC-DC converter 118. (feedback)

The DC-DC converter 118 raises the voltage of the pixel signal Vdac from the DAC unit 128 by a predetermined voltage range to generate a reference supply voltage Vcc capable of driving a constant current, thereby driving the data driver 110. To feed.

To this end, the DC-DC converter 118 includes an inductor L for storing a current supplied from an input voltage source Vbat and a diode D for rectifying a current from the inductor L, as shown in FIG. 7. ), A transistor Q1 connected to the first node N1 between the inductor L and the diode D and connected to the ground voltage source GND, and PWM / for controlling switching of the transistor Q1. PFM control unit 132, and a capacitor (C) for storing the voltage supplied through the diode (D).

The inductor L stores the current from the input voltage source Vbat during the conduction time of the transistor Q1 and emits the current stored at the cutoff time of the transistor Q1 toward the diode D. The diode D rectifies the current emitted from the inductor L and blocks the reverse current.

The transistor Q1 connects the inductor L to one of the base voltage source GND and the diode D in response to the switching control signal of the PWM / PFM controller 132.

The capacitor C stores the voltage output through the diode D and outputs the stored voltage value. At this time, the EL cells 120 are driven by using the voltage output through the capacitor C. FIG.

The capacitor C stores the voltage output through the diode D and outputs the stored voltage value. The EL cells 18 are driven by using the voltage output through the capacitor C. FIG.

The divided resistors R1 and R2 divide the voltage output through the diode D by the resistance ratio. The divided voltage and the feedback pixel signal Vdac dropped by the third resistor R3 are added to appear on the second node N2. The voltage on this second node N2 is supplied to the PWM controller 124.

The PWM controller 124 compares the error amplifier OP2 for amplifying the potential difference between the voltage on the second node N2 and the reference voltage Vref, and the output voltage from the error amplifier OP2 and the input voltage of the sawtooth wave. And a comparator OP1 for switching the transistor Q1.

The error amplifier OP2 amplifies the potential difference between the reference voltage Vref from the reference voltage circuit (not shown) and the voltage at the second node N2 between the voltage divider resistors R1 and R2. That is, the output voltage of the error amplifier OP2 increases / decreases according to the voltage on the second node N2.

The comparator OP1 compares the output of the sawtooth wave from the oscillator (not shown) with the output of the error amplifier OP2 and outputs a signal. Accordingly, the comparator OP1 compares the output voltage of the error amplifier OP2 with the sawtooth wave to control the pulse width of the switching control signal for controlling the conduction time of the transistor Q1.

The DC-DC converter 118 feeds back the voltage on the second node N2 to compare the pulse voltage of the switching control signal for controlling the switching of the transistor Q1 by comparing with the reference voltage Vref. By controlling the output voltage of the inductor (L) is adjusted.

As such, the DC-DC converter 118 generates the pixel signal Vdac fed back from the voltage comparison controller 122 as a base voltage Vcc having a relatively high voltage level, that is, a constant current, and generating data. It supplies to the drive part 112. In other words, the DC-DC converter 118 raises the voltage level of the pixel signal to be supplied to the scan line to which the voltage is dropped, so that the EL display panel can be driven with a constant current.

As described above, the driving device of the EL display element and the driving method thereof according to the present invention are the voltage of the current pixel data when the voltage difference between the previous pixel data supplied to the previous scan line and the current pixel data to be supplied to the current scan line is greater than or equal to the threshold value. Raise the level to drive constant current. Accordingly, the luminance deviation between the previous EL cell connected with the previous scan line and the current EL cell connected with the current scan line can be reduced, thereby preventing horizontal crosstalk.

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the technical spirit of the present invention. Therefore, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification but should be defined by the claims.

Claims (6)

Comparing the first pixel data of the k (k is a natural number) scan line of the display panel with the second pixel data of the k + 1 th scan line and determining a scan line having a changed voltage level by the voltage comparison controller; And generating a pixel signal corresponding to the determined scan line by a converting unit. The method of claim 1, The step of comparing the first pixel data of the k (k is a natural number) scan line of the display panel with the second pixel data of the k + 1 th scan line and determining a scan line having a changed voltage level by the voltage comparison controller Comparing the first and second pixel data in a comparison unit; And converting the pixel signal from the voltage-falled second pixel data by using the digital-to-analog converter when the voltage difference between the first and second pixel data is greater than or equal to the threshold by the comparator. Method of driving display element. The method of claim 2, The generating unit generates a pixel signal corresponding to the determined scan line. And increasing the voltage level of the pixel signal converted by the digital-to-analog converter by a predetermined range using a DC-DC converter. A display panel displaying an image using an organic light emitting cell, A voltage comparison controller configured to compare the first pixel data of the k (k is a natural number) scan line of the display panel with the second pixel data of the k + 1 th scan line to determine a scan line having a changed voltage level; And a converter configured to generate a pixel signal corresponding to the scan line determined by the voltage comparison controller. The method of claim 4, wherein The voltage comparison controller A comparator for comparing the first and second pixel data; And a digital-to-analog converter for converting the voltage-dropped second pixel data into a pixel signal when the voltage difference between the first and second pixel data is greater than or equal to a threshold by the comparator. Device. The method of claim 5, wherein And the DC-DC converter is a DC-DC converter that raises the voltage level of the pixel signal converted by the digital-to-analog converter by a predetermined range.

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