KR100486909B1 - Driving method and apparatus of electro-luminescence display panel - Google Patents

Abstract

The present invention relates to an EL display panel driving apparatus and method capable of reducing power consumption when the amount of light emitting cells is relatively large.

An EL display panel driving apparatus of the present invention includes: a scan driver for driving scan electrode lines; A data driver for driving data electrode lines; A data counter for counting input data to determine a data conversion coefficient; A data converter for converting the input data into smaller data at the same rate and supplying the data driver to the data driver when the data conversion coefficient is equal to or greater than a specific value in response to the data conversion coefficient; A timing controller is provided for controlling the drive timing of the scan driver and the data driver and for supplying data.

Description

Driving device and method of electroluminescent display panel {DRIVING METHOD AND APPARATUS OF ELECTRO-LUMINESCENCE DISPLAY PANEL}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electroluminescent display device, and more particularly, to a driving device of an electroluminescent display panel capable of reducing average power consumption.

Recently, various flat panel displays have been developed to reduce weight and volume, which are disadvantages of cathode ray tubes. Such a flat panel display includes a liquid crystal display, a field emission display, a plasma display panel, and an electroluminescence (hereinafter, EL). And display devices.

Among them, the EL display device is a self-luminous device that emits a fluorescent material by recombination of electrons and holes, and is classified into inorganic EL and organic EL according to its material and structure. Such an EL display device has an advantage that the response speed is as fast as that of a cathode ray tube as compared to a passive light emitting device requiring a separate light source like a liquid crystal display device. In addition, since the EL display device has a low DC driving voltage and is capable of ultra-thin film, the EL display device can be applied to a wall-mounted or portable device.

1 is a cross-sectional view showing a general organic EL structure for explaining the light emission principle of an EL display device. The organic EL includes an electron injection layer 4, an electron transport layer 6, a light emitting layer 8, a hole transport layer 10, and a hole injection layer 12 stacked between the cathode 2 and the anode 14.

When a voltage is applied between the anode 14, which is a transparent electrode, and the cathode 2, which is a metal electrode, electrons generated from the cathode 2 are directed toward the light emitting layer 8 through the electron injection layer 4 and the electron transport layer 6. Move. In addition, holes generated from the anode 14 move toward the light emitting layer 8 through the hole injection layer 12 and the hole transport layer 10. Accordingly, in the light emitting layer 8, light is generated by collision between electrons and holes supplied from the electron transport layer 6 and the hole transport layer 10 and recombination, and the light is externally transmitted through the anode 14 which is a transparent electrode. Is emitted so that the image is displayed. The luminescence brightness of such an EL organic element is not proportional to the voltage across the element but proportional to the supply current, so that the anode 14 is usually connected to a constant current source.

FIG. 2 is a diagram showing a general passive matrix type EL display device.

The EL display device illustrated in FIG. 2 includes an EL display panel 20 including EL cells PE arranged at each intersection of the scan electrode line SL and the data electrode line DL, and the scan electrode lines SL. ) And a data driver 24 for driving the data electrode lines DL.

Each of the EL cells PE is selected when a scan pulse is applied to the scan electrode line SL, which is a cathode, to generate light corresponding to a pixel signal, that is, a current signal, supplied to the data electrode line DL, which is an anode. Each of the EL cells PE is equivalently represented by a diode connected between the data electrode line DL and the scan electrode line SL. Each of the EL cells PE is supplied with a negative scan pulse to the scan electrode line SL and emits light when a positive voltage is applied to the data electrode line DL and a forward voltage is applied thereto. On the contrary, the reverse direction voltage is applied to the EL cells PE included in the unselected scan lines so as not to emit light. In other words, forward charges are charged in the EL cells PE that emit light, whereas opposite charges are charged in the EL cells PE that do not emit light.

The scan driver 22 sequentially supplies the negative scan pulses to the plurality of scan electrode lines SL in line order.

The data driver 24 supplies a current signal having a current level or pulse width corresponding to the data signal to the data electrode lines DL every horizontal period.

In this way, the EL display device supplies a current signal having a current level or pulse width proportional to the input data to the EL cells PE. Accordingly, since the amount of current supplied in proportion to the amount of input data is increased, the amount of power consumption increases in proportion to the amount of light emitting cells as shown in a graph P showing the relationship between the amount of light emitting cells and the power consumption shown in FIG. 3. As described above, the conventional EL display device has a disadvantage in that the power consumption is too large when the number of light emitting cells is large.

It is therefore an object of the present invention to provide an EL display panel driving apparatus and method which can reduce power consumption when the amount of light emitting cells is relatively large.

In order to achieve the above object, an EL display panel driving apparatus according to an aspect of the present invention comprises: a scan driver for driving scan electrode lines; A data driver for driving data electrode lines; A data counter for counting input data to determine a data conversion coefficient; A data converter for converting the input data into smaller data at the same rate and supplying the data driver to the data driver when the data conversion coefficient is equal to or greater than a specific value in response to the data conversion coefficient; A timing controller is provided for controlling the drive timing of the scan driver and the data driver and for supplying data.

In particular, the data converter includes a lookup table, and when the data conversion coefficient exceeds a specific value by using the lookup table, the input data is converted into smaller data at the same rate and output.

Here, the data counter and the data converter are integrated with any one of a timing controller and a data driver.

According to another aspect of the present invention, there is provided a driving apparatus of an EL display panel, comprising: a timing controller for generating scan timing control signals and data timing control signals and sorting and outputting input data; A data counter for counting data from the timing controller to determine a conversion coefficient; A pulse width converter for converting a pulse width of a pulse width modulated clock signal included in the data timing control signal and supplying the converted data to the data driver when the conversion coefficient is greater than or equal to a specific value in response to the conversion coefficient; A scan driver for driving scan electrode lines using scan timing control signals; And a data driver for supplying a current signal having a pulse width proportional to the data to the data electrode lines using the data timing control signals and the pulse width modulated clock signal from the pulse width converter.

In particular, the pulse width converter may reduce and output the pulse widths of the pulse width modulated clock signals of a specific unit in the same ratio when the conversion coefficient exceeds a specific value.

Here, the data counter and the pulse width converter may be integrated with any one of a timing controller and a data driver.

According to still another aspect of the present invention, there is provided a driving apparatus of an EL display panel, comprising: a scan driver for driving scan electrode lines; A data driver for driving data electrode lines; A timing controller for controlling the drive timing of the scan driver and the data driver and for supplying data to the data driver; The timing controller includes: a data counter for counting input data and determining a conversion coefficient; A synchronization frequency converter for converting frequencies of the vertical synchronization signal and the horizontal synchronization signal, which are input when the data conversion coefficient is equal to or greater than a specific value in response to the conversion coefficient; A control signal generator for generating timing control signals for controlling the scan driver and the data driver by using the vertical synchronization signal and the horizontal synchronization signal from the synchronous frequency converter; And a data alignment unit for sorting and outputting the input data.

In particular, the synchronous frequency converter is characterized by reducing the frequency of the vertical synchronization signal and the horizontal synchronization signal when the conversion coefficient exceeds a specific value.

A method of driving an EL display panel according to an aspect of the present invention includes the steps of counting input data to determine a data conversion coefficient; Converting and outputting the data when the data conversion coefficient is greater than or equal to a specific value in response to the data conversion coefficient; And supplying a current signal in response to the output data to the data electrode lines.

In particular, the step of converting and outputting data is characterized in that the step of converting and outputting the input data to a smaller value of data at the same ratio when the data conversion coefficient exceeds a specific value.

According to another aspect of the present invention, there is provided a method of driving an EL display panel, comprising: generating a pulse width modulated clock signal; A data counter for counting input data to determine a conversion coefficient; Converting and outputting a pulse width of a pulse width modulated clock signal when the conversion coefficient is greater than or equal to a specific value in response to the conversion coefficient; And supplying a current signal having a pulse width proportional to the data to the data electrode lines using the output pulse width modulated clock signal.

In particular, the step of converting and outputting the pulse width is characterized in that the step of reducing and outputting the pulse width of the pulse width modulated clock signals of a specific unit when the conversion coefficient exceeds a specific value.

According to still another aspect of the present invention, there is provided a method of driving an EL display panel, comprising: determining a conversion coefficient by counting input data; Converting and outputting frequencies of the vertical synchronizing signal and the horizontal synchronizing signal if the conversion coefficient is greater than or equal to the specific value in response to the conversion coefficient; And driving the scan electrode lines and the data electrode lines by using the output vertical sync signal and the horizontal sync signal.

In particular, the step of converting and outputting the frequency of the vertical synchronizing signal and the horizontal synchronizing signal is characterized in that the step of reducing and outputting the frequency of the vertical synchronizing signal and the horizontal synchronizing signal when the conversion coefficient exceeds a specific value.

Other objects and features of the present invention in addition to the above objects will become apparent from the description of the embodiments with reference to the accompanying drawings.

Hereinafter, exemplary embodiments of the present invention will be described with reference to FIGS. 4 to 7.

4 is a block diagram showing a driving device of an EL display panel according to an embodiment of the present invention.

The EL display panel driver shown in Fig. 4 includes a timing controller 30 for supplying various control signals and data signals, and a data counter for counting the amount of data output from the timing controller 30 to determine the data conversion coefficient ( 32 and a data converter 34 for converting the data from the timing controller 30 and supplying the data to the data driver 36 in response to the data conversion coefficient from the data counter 32.

The timing controller 30 generates timing control signals for controlling the driving timing of the data driver 36 and the scan driver (not shown) using control signals (vertical synchronization signal, horizontal synchronization signal, etc.) input from the outside. do. In addition, the timing controller 30 sorts and outputs data signals input from the outside.

The data counter 32 determines the data conversion coefficient by counting the data amount output from the timing controller 30 in a specific unit, that is, in a frame unit. The data conversion coefficient determined by this data counter 32 is proportional to the counted data amount.

The data converter 34 converts the data from the timing controller 30 in response to the data conversion coefficient from the data counter 32, and outputs the converted data to the data driver 36. To this end, the data converter 34 is provided in the form of a look up table for selecting and outputting the converted data matching the input data and the data conversion coefficients. The input data stored in the data converter 34 and the converted data matching the data conversion coefficients are predetermined values by repeated experiments. Specifically, the data converter 34 converts the input data into data having a smaller value as the data conversion coefficient from the data counter 32 increases, thereby reducing the luminance of the EL display panel (not shown). In this case, the data converter 34 converts the data of a specific unit, i.e., the frame unit, into reduced data at the same rate and outputs the gray scale so that the gray scale implementation becomes normal. In particular, the data converter 34 converts the input data value into data having a small value and outputs the data only when the data conversion coefficient from the data counter 32 is equal to or greater than a specific value.

The data driver 36 supplies a current signal having a current level or pulse width in response to the data from the data converter 34 to the data electrode lines of the EL display panel. In particular, the data driver 36 can reduce power consumption by decreasing the current level or pulse width proportional to the data in proportion to the data converted by the data converter 34 when the amount of light emitting cells increases. do.

As described above, the EL display panel driving apparatus according to the embodiment of the present invention can reduce power consumption by converting data into small data at the same ratio when the amount of light emitting cells exceeds a specific value. Here, the data counter 32 and the data converter 34 may be embedded in the timing controller 30 or the data driver 36 or may be implemented in a separate IC form.

For example, the data converter 34 inputs data only when the ratio of the amount of light emitting cells in one frame exceeds about 40% of the total light emitting cells as shown in the graph P of the amount of light emitting cells and power consumption shown in FIG. 5. Will be converted to small value data and output. As the amount of light emitting cells increases, the input data is converted into data having a smaller value and output. Accordingly, when the amount of light emitting cells exceeds about 40%, such as the change amount VDQ of the output data compared to the input data shown in FIG. 5, the output data is significantly reduced compared to the input data. In particular, as shown in FIG. 5, when the input data amount exceeds a specific value, the data amount DDQ reduced on the screen by the data converter 34 becomes larger as the input data amount increases. As a result, when the amount of light emitting cells exceeds about 40%, the amount of power consumption (DPQ) reduced in the EL display device also increases.

6 is a block diagram showing a driving device of an EL display panel according to another embodiment of the present invention.

The EL display panel driver shown in FIG. 6 includes a timing controller 40 for supplying various control signals and data signals, and a data counter 42 for counting the amount of data output from the timing controller 40 to determine the conversion coefficient. And a pulse width converter 44 for converting and outputting a pulse width of a pulse width modulation (hereinafter referred to as PWM) clock signal from the timing controller 40 in response to the conversion coefficient from the data counter 32, And a data driver 46 for supplying a current signal having a pulse width in response to the data signal from the timing controller 40 to the data electrode lines using the PWM clock signal from the pulse width converter 44.

The timing controller 40 controls data timing control signals for controlling the driving of the data driver 36 using control signals (vertical synchronization signal, horizontal synchronization signal, etc.) input from the outside, and a scan driver (not shown). Generates scan timing control signals to control the driving of the. Here, the data timing control signals include a PWM clock signal to be used for the PWM operation of the data driver 46. In addition, the timing controller 40 sorts and outputs data signals input from the outside.

The data counter 42 determines the conversion coefficient by counting the amount of data output from the timing controller 40 in a specific unit, that is, in a frame unit. The conversion coefficient determined by this data counter 42 is proportional to the input data amount.

The pulse width converter 44 converts the pulse width of the PWM clock signal from the timing controller 40 in response to the data conversion coefficient from the data counter 42 and outputs it to the converted PWM clock signal data driver 46. . Specifically, the pulse width converter 44 decreases and outputs the pulse width of the PWM clock signal as the conversion coefficient from the data counter 42 increases. In other words, the pulse width converter 44 increases and outputs the frequency of the PWM clock signal as the conversion coefficient increases. In particular, the pulse width converter 44 reduces and outputs the pulse width of the PWM clock signal only when the conversion coefficient from the data counter 42 is equal to or greater than a specific value. For example, the pulse width converter 44 is a PWM only when the ratio of the amount of light emitting cells in one frame exceeds about 40% of the total light emitting cells as shown in the graph P of the amount of light emitting cells and power consumption shown in FIG. 5. The pulse width of the clock signal is reduced and output. As the amount of light emitting cells increases, the pulse width of the PWM clock signal is decreased and output.

The data driver 46 uses a PWM clock signal from the pulse width converter 44 to output a current signal having a pulse width proportional to the data input from the timing controller 40 to the data electrode of the EL display panel (not shown). To the lines. In particular, when the pulse width of the PWM clock signal from the pulse width converter 44 is reduced, that is, when the frequency of the PWM clock signal is increased, the pulse width of the current signal output from the data driver 46 is reduced. When the PWM clock signal with the reduced pulse width is used, the current signals output by the data driver 46 in a specific unit, that is, in the unit of frame, are reduced by the same ratio, so that power consumption is reduced and the overall luminance is relatively reduced, while gradation is reduced. It can be implemented normally.

As described above, the EL display panel driving apparatus according to another embodiment of the present invention can reduce the power consumption by reducing the pulse width of the current signal in response to the data at the same ratio when the amount of light emitting cells exceeds a specific value. Here, the data counter 42 and the pulse width converter 44 may be embedded in the timing controller 40 or the data driver 46, or may be implemented in a separate IC form.

7 is a block diagram showing a driving device of an EL display panel according to another embodiment of the present invention.

The EL display panel driving apparatus shown in FIG. 4 uses the timing controller 50 for supplying various control signals and data signals, and the EL display panel using timing control signals output from the timing controller 50 (not shown). A data driver for driving data electrode lines of an EL display panel (not shown) by using a scan driver 60 for driving the scan electrode lines of the PDP) and timing control signals and data signals output from the timing controller 50. 62 is provided.

The timing controller 50 generates timing control signals for controlling driving timings of the scan driver 60 and the data driver 60 using control signals (vertical synchronization signal, horizontal synchronization signal, etc.) input from the outside. In addition, the timing controller 50 sorts and outputs data signals input from the outside. In particular, the timing controller 50 converts and outputs the frame frequency, that is, the frequencies of the vertical synchronizing signal V and the horizontal synchronizing signal H, when the amount of data input is equal to or greater than a specific value. The frequency of the timing control signals is converted to the scan driver 60 and the data driver 62 according to the frequency-converted vertical synchronizing signal V and the horizontal synchronizing signal H.

To this end, the timing controller 50 synchronizes the frequency of the input signal in response to the conversion coefficient from the data counter 52 and the data counter 52 which determines the conversion coefficient by counting the amount of data inputted. A timing control signal generator 56 for generating timing control signals using the frequency converter 54, a synchronization signal from the synchronous frequency converter 54, and a data alignmentr 58 for aligning and outputting the input data; It is provided.

The data counter 52 determines the conversion coefficient by counting the amount of data input to the timing controller 50 in a specific unit, that is, in a frame unit. The conversion coefficient determined by this data counter 52 is proportional to the input data amount.

The synchronous frequency converter 54 generates a timing control signal by converting the frequencies of the vertical synchronizing signal V and the horizontal synchronizing signal H input to the timing controller 50 in response to the data conversion coefficient from the data counter 52. Output to the unit 56. Specifically, the synchronization frequency converter 54 decreases and outputs the frequencies of the vertical synchronization signal V and the horizontal synchronization signal H as the conversion coefficient from the data counter 52 increases. In particular, the synchronous frequency converter 54 reduces and outputs the frequencies of the vertical synchronizing signal V and the horizontal synchronizing signal H only when the conversion coefficient from the data counter 52 is equal to or greater than a specific value. For example, the synchronous frequency converter 54 is vertical only when the ratio of the amount of light emitting cells in one frame exceeds about 40% of the total light emitting cells as shown in the graph P of the amount of light emitting cells and power consumption shown in FIG. 5. The frequency of the synchronization signal V and the horizontal synchronization signal H are reduced and output. As the amount of light emitting cells, that is, the amount of input data increases, the frequencies of the vertical synchronizing signal V and the horizontal synchronizing signal H are further reduced and output.

The control signal generator 56 uses the vertical synchronizing signal V and the horizontal synchronizing signal H from the synchronizing frequency converter 54 to perform a scan start pulse, a scan shift clock signal, and the like necessary for driving the scan driver 60. Similarly, scan timing control signals and data timing control signals such as a data start pulse and a data shift clock signal required for driving the data driver 62 are generated. Accordingly, when the frequencies of the vertical synchronizing signal V and the horizontal synchronizing signal H are reduced, the frequencies of the scan timing control signals and the data timing control signals using the same are also reduced.

The data alignment unit 58 aligns the data input from the outside and outputs the data to be suitable for driving the data driver 62.

The scan driver 60 sequentially drives the scan electrode lines of the EL display panel using the scan timing control signals from the timing controller 50. In particular, when the frequency of the scan timing control signals from the timing controller 50 is reduced, the scan driver 60 drives the scan electrode lines at a lower speed, thereby reducing power consumption.

The data driver 62 uses a data timing control signal from the timing controller 50 to output a current signal having a current level or pulse width corresponding to data input from the timing controller 50 to the data electrode lines of the EL display panel. To feed. In particular, when the frequency of the data timing control signals from the timing controller 50 is reduced, the current signal supply speed from the data driver 62 is reduced, thereby reducing power consumption.

As such, the EL display panel driving apparatus according to another embodiment of the present invention can reduce power consumption by reducing the frame frequency when the amount of light emitting cells exceeds a specific value.

As described above, the EL display panel driving apparatus and method according to the present invention can reduce power consumption by converting data, pulse width or frame frequency when the amount of light emitting cells exceeds a specific value.

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.

1 is a cross-sectional view showing the structure of a conventional organic EL element.

Fig. 2 is a diagram showing a driving device of a conventional organic EL display panel.

3 is a graph showing the relationship between the amount of light emitting cells and power consumption in a conventional organic EL display panel driving apparatus.

4 illustrates an organic EL display panel driving apparatus according to an exemplary embodiment of the present invention.

Fig. 5 is a graph showing the relationship between the amount of light emitting cells and power consumption in the organic EL display panel driving apparatus according to the present invention.

6 is a diagram illustrating an organic EL display panel driving apparatus according to another exemplary embodiment of the present invention.

7 illustrates an organic EL display panel driving apparatus according to still another embodiment of the present invention.

<Description of Symbols for Main Parts of Drawings>

2 metal electrode 4 electron injection layer

6: electron transport layer 8: light emitting layer

10 hole transport layer 12 hole injection layer

14 transparent electrode 20 EL display panel

22, 60: scan driver 24, 36, 46, 62: data driver

30, 40, 50: timing controller 32, 42, 52: data counter

34: data converter 44: pulse width converter

54 Synchronous Frequency Converter 56 Timing Control Signal Generator

58: data sorting unit

Claims (14)

A driving device of an EL display panel, comprising an electro-luminescence (hereinafter referred to as EL) cell at each intersection of scan electrode lines and data electrode lines. A scan driver for driving the scan electrode lines; A data driver for driving the data electrode lines; A data counter for counting input data to determine a data conversion coefficient; A data converter for converting the input data into smaller data at the same rate and supplying the data driver to the data driver in response to the data conversion coefficient; And a timing controller for controlling the driving timing of the scan driver and the data driver and for supplying the data. The method of claim 1, And the data converter includes a look-up table, and converts and outputs the input data when the data conversion coefficient exceeds a specific value using the look-up table. The method of claim 1, And the data counter and data converter are integrated together with any one of the timing controller and data driver. A driving device of an EL display panel, comprising an electro-luminescence (hereinafter referred to as EL) cell at each intersection of scan electrode lines and data electrode lines. A timing controller which generates scan timing control signals and data timing control signals and aligns and outputs input data; A data counter for counting data from the timing controller to determine a conversion coefficient; A pulse width converter converting a pulse width of a pulse width modulated clock signal included in the data timing control signal and supplying the converted data to the data driver when the conversion coefficient is greater than or equal to a specific value in response to the conversion coefficient; A scan driver for driving the scan electrode lines using the scan timing control signals; And a data driver for supplying a current signal having a pulse width proportional to the data to the data electrode lines using the data timing control signals and a pulse width modulated clock signal from the pulse width converter. EL display panel drive device. The method of claim 4, wherein And the pulse width converter reduces and outputs the pulse widths of the pulse width modulated clock signals in a specific unit at the same ratio when the conversion coefficient exceeds a specific value. The method of claim 4, wherein And the data counter and the pulse width converter are integrated together with any one of the timing controller and data driver. A driving device of an EL display panel, comprising an electro-luminescence (hereinafter referred to as EL) cell at each intersection of scan electrode lines and data electrode lines. A scan driver for driving the scan electrode lines; A data driver for driving the data electrode lines; A timing controller which controls driving timing of the scan driver and the data driver and supplies data to the data driver; The timing controller A data counter for counting input data to determine a conversion coefficient; A synchronous frequency converter for converting frequencies of the vertical synchronizing signal and the horizontal synchronizing signal, which are input when the conversion coefficient is greater than or equal to a specific value in response to the conversion coefficient; A control signal generator for generating timing control signals for controlling the scan driver and the data driver by using the vertical synchronizing signal and the horizontal synchronizing signal from the synchronizing frequency converter; And a data alignment unit for sorting and outputting the input data. The method of claim 7, wherein And the synchronous frequency converter reduces and outputs frequencies of the vertical synchronous signal and the horizontal synchronous signal when the conversion coefficient exceeds a specific value. A method of driving an EL display panel including an electro-luminescence cell (hereinafter referred to as EL) at each intersection of scan electrode lines and data electrode lines. Counting input data to determine a data conversion coefficient; Converting and outputting the data when the data conversion coefficient is greater than or equal to a specific value in response to the data conversion coefficient; And supplying a current signal in response to the output data to the data electrode lines. The method of claim 9, Converting and outputting the data And converting the input data into data having a smaller value at the same ratio when the data conversion coefficient exceeds a specific value, and outputting the same. A method of driving an EL display panel including an electro-luminescence cell (hereinafter referred to as EL) at each intersection of scan electrode lines and data electrode lines. Generating a pulse width modulated clock signal; A data counter for counting input data to determine a conversion coefficient; Converting and outputting a pulse width of the pulse width modulated clock signal when the conversion coefficient is greater than or equal to a specific value in response to the conversion coefficient; And supplying the output pulse width modulated clock signal to the data electrode lines with a current signal having a pulse width proportional to the data. The method of claim 11, Converting the pulse width and outputting And outputting the pulse widths of the pulse width modulated clock signals of a specific unit in the same ratio when the conversion coefficient exceeds a specific value. A method of driving an EL display panel including an electro-luminescence cell (hereinafter referred to as EL) at each intersection of scan electrode lines and data electrode lines. Counting input data to determine a data conversion coefficient; Converting and outputting a frequency of a vertical synchronizing signal and a horizontal synchronizing signal input when the conversion coefficient is greater than or equal to a specific value in response to the conversion coefficient; And driving the scan electrode lines and the data electrode lines by using the output vertical synchronization signal and horizontal synchronization signal. The method of claim 13, Converting and outputting frequencies of the vertical synchronization signal and the horizontal synchronization signal And reducing the frequencies of the vertical synchronization signal and the horizontal synchronization signal when the conversion coefficient exceeds a specific value.