KR20080025556A - Circuit for supplying gamma reference voltage - Google Patents

Abstract

A circuit for supplying gamma reference voltages is provided to display stable images in an LCD(Liquid Crystal Display) panel by supplying gamma buffer voltages having the same absolute value to a source driver through buffering of buffers. A circuit for supplying gamma reference voltages includes a source driver(117) and plural gamma buffers(600,610,620,630). The source driver converts digital data into analog data and outputs the converted data to column lines of an LCD(Liquid Crystal Display) panel. The gamma buffers having two buffers supply a reference voltage, which is used for the conversion of the source driver, to the source driver by buffering alternately two gamma reference voltages having the same absolute value in the two buffers according to a frame signal.

Description

Gamma Reference Voltage Supply Circuit {CIRCUIT FOR SUPPLYING GAMMA REFERENCE VOLTAGE}

1 is a view showing the configuration of a driving circuit module of a general LCD panel;

2 is a diagram illustrating a configuration of a plurality of source drivers in a driving circuit module of an LCD panel;

3 is a view illustrating an example of a driving circuit module of an LCD panel in which a chip of a source driver is integrated on a glass substrate of an LCD panel;

4 is a view showing another example of a driving circuit module of an LCD panel with a source driver packaged on a glass substrate of the LCD panel;

5 is a diagram illustrating a configuration in which a source driver bypasses a gamma reference voltage and transfers the same to another source driver.

6 is a diagram illustrating a configuration in which a source driver buffers a gamma reference voltage into a buffer and transfers the same to another source driver; and

7 is a diagram showing the configuration of a gamma reference voltage supply circuit of the present invention.

The present invention relates to a gamma reference voltage supply circuit.

In general, an LCD panel is one of display devices that display an image while controlling the amount of light transmitted by applying an electric signal having a predetermined level according to display data to liquid crystal molecules.

The LCD driving module for driving the LCD panel includes a timing controller which receives display information from a graphics board such as a video graphics adapter (VGA) and controls timing of a source driver, and a gamma reference voltage for converting digital data into analog data. A gamma reference voltage generator configured to generate a plurality of sources, a plurality of source drivers for converting digital data into analog data based on the gamma reference voltage and outputting the analog data to column lines of an LCD panel, and a plurality of sequentially driving row lines of the LCD panel. And a gate driver, a timing controller, a gamma reference voltage generator, a plurality of source drivers, and a power supply unit for supplying an operating voltage to each of the plurality of gate drivers.

The LCD driving module having the above configuration is configured in a PCB (Printed Circuit Board) made of a multi-layer (Multi Layer) separately from the LCD panel. In this case, since the gamma reference voltage generated by the gamma reference voltage generator can be supplied to the plurality of source drivers and the plurality of gate drivers, respectively, the gamma reference voltages supplied to the plurality of source drivers and the plurality of gate drivers are constant.

In general, the manufacturing cost of the multilayered PCB takes a large part in manufacturing the entire driving circuit module of the LCD panel. Therefore, in manufacturing the driving circuit module of the LCD panel, in order to reduce the cost of the PCB, the driving circuit module of the LCD panel that does not use the PCB has been developed.

The driving circuit module of the LCD panel which does not use a PCB typically integrates a source driver on the glass substrate of the LCD panel, and supplies an operating voltage, data, and gamma reference voltage from the outside of the LCD panel.

In this case, one source driver among the plurality of source drivers integrated on the glass substrate receives the gamma reference voltage from the outside and transfers the received gamma reference voltage to another source driver adjacent to the plurality of source drivers. It should be configured to deliver the gamma reference voltage sequentially.

One source driver receives a gamma reference voltage and transfers the received gamma reference voltage to other source drivers. The source drivers bypass the gamma reference voltage, and the source driver includes a buffer. There is a method of buffering and transferring a gamma reference voltage in a buffer.

In the method of bypassing the gamma reference voltage, a source driver receiving a gamma reference voltage first from an external source may convert digital data into analog data accurately with a gamma reference voltage having a sufficient level.

However, the voltage drop occurs sequentially while bypassing the gamma reference voltage. As a result, the source driver receiving the gamma reference voltage has a low voltage level of the gamma reference voltage, thereby converting the digital data into analog data accurately. Can not.

In addition, the method of buffering and transferring the gamma reference voltage to the buffer may supply a gamma reference voltage having a stable voltage level to all source drivers according to the buffering in the buffer.

However, when the buffer buffers the gamma reference voltage, an offset voltage is generated in the buffer, which causes a problem that the level of the gamma reference voltage supplied by each source driver is slightly different.

Therefore, in a plurality of source drivers, when the buffer buffers the gamma reference voltage, it is required to prevent the gamma reference voltage from being changed by the offset voltage generated in the buffer.

An object of the present invention is to integrate a plurality of source drivers on the glass substrate of the LCD panel, so that the offset voltage generated in the buffer is compensated when the buffers provided in the plurality of source drivers sequentially buffer and transfer the gamma reference voltage Therefore, the present invention provides a gamma reference voltage supply circuit that does not vary the range of the gamma reference voltage.

Therefore, the gamma reference voltage supply circuit of the present invention includes a source driver for converting input digital data into analog data and outputting the result to a column line of an LCD panel, and two buffers, each having the opposite polarity and the same absolute level. And a plurality of gamma buffer units configured to alternately buffer two gamma reference voltages according to a frame signal and supply the source driver as a reference voltage for converting the digital data into analog data. .

Each of the plurality of gamma buffer units may respectively buffer first and second switching units that alternately select gamma reference voltages having positive and negative polarities according to a frame signal, and gamma reference voltages selected by the first and second switching units, respectively. A third switching unit configured to select a gamma reference voltage having a positive polarity according to the frame signal from two gamma reference voltages buffered by the two buffers, and to supply the gamma reference voltage to the source driver, and the two buffers A fourth switching unit for selecting a gamma reference voltage having a negative polarity according to the frame signal among the buffered gamma reference voltages and supplying the gamma reference voltage to the source driver, wherein each of the first to fourth switching units is a multiplexer. It is done.

The source driver may include a plus string unit configured to generate a plurality of plus voltages by dividing a plus polarity gamma reference voltage output by the first and second gamma buffer units, and a negative polarity output by the first and second gamma buffer units. A negative string portion for generating a plurality of plus voltages by dividing a gamma reference voltage of A plurality of negative digital / analog converters for selecting a single negative voltage according to a value of digital data input from a graphics board among a plurality of negative voltages generated by the negative string unit, a plurality of negative digital / analog converters, Plus digital to analog converter A plurality of multiplexers for selecting a positive voltage to be selected or a negative voltage selected by the plurality of negative digital-to-analog converters according to a polarity selection signal and outputting them to a column electrode of the LCD panel, wherein each of the plus string portion and the negative string portion Is a plurality of resistors connected in series to divide the gamma reference voltage.

Hereinafter, with reference to the accompanying drawings illustrating a preferred embodiment of the gamma reference voltage supply circuit of the present invention, the same parts will be given the same reference numerals will be described in detail. However, in describing the present invention, when it is determined that detailed descriptions of related known functions or configurations may unnecessarily obscure the subject matter of the present invention, detailed description thereof will be omitted.

1 is a view illustrating a configuration of a driving circuit module of a general LCD panel. Here, reference numeral 100 denotes an LCD panel, reference numeral 110 denotes a source drive module for driving a column line of the LCD panel 100, and reference numeral 120 denotes a gate drive module for driving a low line of the LCD panel 100.

The source drive module 110 receives a display information from a graphic board and controls the timing, and a gamma reference voltage generator 113 for generating a gamma reference voltage for converting digital data into analog data. And a gamma reference generated by the gamma reference voltage generator 113 to generate digital data input from a graphics board operating at the operating voltage supplied from the power supply unit 115 and the power supply unit 115 to supply an operating voltage. A plurality of source drivers 117-1 and 117-2, which are converted into analog data based on a voltage and output the analog data to column lines of the LCD panel 100 according to timing control of the timing controller 111. , ..., 117-N).

The gate drive module 120 operates at an operating voltage supplied from the power supply 115, and sequentially drives the row lines of the LCD panel 100 according to timing control of the timing controller 111. Of the gate drivers 121-1, ..., 121-N.

In the driving circuit module of the LCD panel having such a configuration, the power supply unit 115 of the source drive module 110 generates an operating voltage, and thus a plurality of source drivers 117-1, 117-2, ..., 117-N and gate drive. Supply to the plurality of gate drivers 121-1,..., 121 -N provided in the module 120. The gamma reference voltage generator 113 generates a gamma reference voltage, and the generated gamma reference voltages are supplied to the plurality of source drivers 117-1, 117-2, ..., 117-N.

In this state, the timing control unit 111 generates a timing control signal according to the data input from the graphics board, and the generated timing control signals are a plurality of source drivers 117-1, 117-2, ..., 117-N. And a plurality of gate drivers 121-1, ..., 121-N.

Then, each of the plurality of source drivers 117-1, 117-2,..., 117 -N converts the digital data input from the graphics board into analog data based on the gamma reference voltage and then the timing controller. In accordance with the timing control signal input from the 111, the output to the column line of the LCD panel 100. The gate drivers 121-1,..., 121 -N sequentially drive the low lines of the LCD panel 100 in response to a timing control signal input from the timing controller 111, and thus the LCD panel 100. A predetermined image is displayed on the screen.

2 is a diagram illustrating a configuration of a plurality of source drivers 117 (117-1, 117-2, ...) in a driving circuit module of an LCD panel. Referring to FIG. 2, each of the plurality of source drivers 117 may include a plus string unit 200, a minus string unit 210, a plurality of plus digital / analog converters 220-1, 220-2,. And a digital to analog converter (230-1, 230-2, ...) and a plurality of multiplexers (240-1, 240-2, 240-3, 240-4, ...).

The plus string unit 200 has a plurality of resistors connected in series, and positive gamma reference voltages GAM + H and + GAML, which are externally input to both terminals of the plurality of resistors connected in series, are applied to the plus gamma reference voltage. Generate a plurality of positive voltages having a voltage level between (+ GAMH) and positive gamma reference voltage (+ GAML).

The negative string unit 200 has a plurality of resistors connected in series, and a negative gamma reference voltage (-GAMH, -GAML) input from the outside is applied to both ends of the plurality of resistors connected in series, respectively, so that the negative gamma reference voltage ( Generate a plurality of negative voltages having a voltage level between -GAMH) and a negative gamma reference voltage (-GAML).

Each of the plurality of plus digital / analog converters 220-1, 220-2, ... receives a plurality of positive voltages generated by the plus string unit 200, and receives a plurality of plus voltages from the graphic board. Select one plus voltage accordingly.

Each of the plurality of negative digital-to-analog converters 230-1, 230-2,..., Receives a plurality of negative voltages generated by the minus string unit 200, and inputs a plurality of negative voltages to a digital data value input from a graphic board. Accordingly select one negative voltage.

Each of the multiplexers 240-1, 240-2, 240-3, 240-4,..., 2 is a pair of the multiplexers 240-1, 240-2, 240-3, 240-4. )… Each of them is a positive and negative digital-to-analog converter 220-1, 230-1 (220-2 230-2). They input the positive and negative voltages respectively output, and select one voltage according to the polarity selection signal POL and output them to the column electrode of the LCD panel 100.

Each of the source drivers 117 having such a configuration generates a plurality of positive voltages by dividing the input plus gamma reference voltages (+ GAMH, + GAML) into a plurality of resistors by the plus string unit 200. The negative gamma reference voltages (-GAMH and -GAML) are generated by the negative string unit 210 divided into a plurality of resistors to generate a plurality of negative voltages.

A plurality of positive voltages generated by the plus string unit 200 are input to a plurality of plus digital / analog converters 220-1, 220-2,..., And a plurality of negative voltages generated by the minus string unit 210. The voltage is input to the plurality of negative digital-to-analog converters 230-1, 230-2, ....

The digital data for each pixel of the image to be displayed on the LCD panel 100 from an external graphic board is divided into a plurality of positive digital / analog converters 220-1, 220-2, ..., and a plurality of negative digital / analog converters. (230-1, 230-2, ...) are selectively input.

Then, a plurality of plus digital / analog converters 220-1 and 220-2 are provided. Each of them selects a single plus voltage corresponding to the value of the input digital data so that the multiplexer 240-1, 240-2 (240-3, 240-4). And a plurality of negative digital-to-analog converters 230-1 and 230-2. Each of them selects a single negative voltage corresponding to the value of the input digital data, so that the multiplexers 240-1, 240-2 (240-3, 240-4). Will output

Each of the multiplexers 240-1, 240-2, 240-3, 240-4,..., Alternately selects a positive voltage and a negative voltage according to an input polarity selection signal POL. That is, when the multiplexers 240-1, 240-3, ... select the positive voltage according to the polarity selection signal POL, the multiplexers 240-2, 240-4, ... select the negative voltage, and the polarity line The multiplexers 240-2, 240-4, ... select the positive voltage when the multiplexers 240-1, 240-3, ... select the negative voltage according to the tack signal POL.

The positive voltage and the negative voltage alternately selected by the multiplexers 240-1, 240-2, 240-3, 240-4,... Are output to the column lines of the LCD panel 100 to display the LCD panel 100. A predetermined image is displayed on.

In the driving circuit module of the LCD panel having such a configuration, the source drive module 110 is configured in a PCB made of a multilayer. Since the multilayer PCB is very expensive, a large portion of the costs of manufacturing the entire driving circuit module of the LCD panel is taken up.

Therefore, in manufacturing the driving circuit of the LCD panel, the source substrate 117 is formed on the glass substrate by extending the glass substrate constituting the LCD panel 100 without forming the source drive module 110 on the multilayer PCB. Doing.

3 is a diagram illustrating an example of a driving circuit module of an LCD panel in which a source driver is integrated into a glass substrate of the LCD panel. Referring to FIG. 3, the glass substrate 300 on which the LCD panel 100 is formed is extended, and a plurality of source drivers 117-1, 117-2,..., 117 -N are provided on the extended glass substrate 300. ), And the data, the operating voltage and the gamma reference voltage are input from the outside of the glass substrate 300 so that the plurality of source drivers 117-1, 117-2,..., 117 -N can be sequentially transferred. Configured.

4 is a diagram illustrating another example of a driving circuit module of an LCD panel in which a source driver is integrated into a glass substrate of the LCD panel. Referring to FIG. 4, the plurality of source drivers 117-1, 117-2,..., 117 -N packaged on the side of the LCD panel 100 are attached, and data and operation are performed outside the LCD panel 100. A voltage and a gamma reference voltage are input to sequentially transmit the plurality of source drivers 117-1, 117-2,..., 117 -N.

As shown in FIG. 3, the chips of the plurality of source drivers 117-1, 117-2,..., 117 -N are integrated on the glass substrate 300 of the LCD panel 100 or packaged as shown in FIG. 4. By attaching to the LCD panel 100 of the source drivers 117-1, 117-2,..., 117 -N, it is not necessary to use an expensive multilayer PCB to configure the source drive module 110.

However, any one of the plurality of source drivers 117-1, 117-2,..., 117 -N receives data, an operating voltage and a gamma reference voltage from an external source, and the received data, the operating voltage and the gamma reference voltage. Must be passed sequentially to other source drivers.

As a method of sequentially transmitting the gamma reference voltages by the plurality of source drivers 117-1, 117-2,..., 117 -N, the source drivers 117-1, 117-2,. There is a method of bypassing the gamma reference voltage, and a method of providing a buffer in the source drivers 117-1, 117-2, ..., 117-N, and buffering and transmitting the gamma reference voltage in the buffer.

5 is a diagram illustrating a configuration in which a source driver bypasses a gamma reference voltage and transfers the same to another source driver. Referring to FIG. 5, in the method of bypassing the gamma reference voltage, the gamma reference voltage input terminals of each of the plurality of source drivers 117 are connected in a pattern.

Therefore, the method of bypassing the gamma reference voltage causes the externally input gamma reference voltages (+ GAMH, + GAML, -GAML, -GAMH) to be input to the positive string unit 200 and the negative string unit 210, and The gamma reference voltages (+ GAMH, + GAML, -GAML, and -GAMH) input from the outside are bypassed and transferred to another source driver 117.

However, in the method of bypassing the gamma reference voltage, the length of the pattern for bypassing the gamma reference voltage is relatively long, so that the parasitic resistance (R) and the parasitic capacitance (C) occur in the pattern, and thus the gamma reference voltage supplied is The gamma reference voltage is attenuated by the parasitic resistance R and the parasitic capacitance C, and the gamma reference voltage supplied to each of the plurality of source drivers 117 is different.

FIG. 6 is a diagram illustrating a configuration in which a source driver buffers a gamma reference voltage in a buffer and transfers the gamma reference voltage to another source driver. Referring to FIG. 6, a method of buffering a gamma reference voltage into a buffer includes buffers 600, 610, 620, and 630 in each of the plurality of source drivers 117. The buffers 600, 610, 620, and 630 are respectively buffered with gamma reference voltages (+ GAMH, + GAML, -GAML, and -GAMH) input from the outside, and thus, the plus string unit 200 and the minus string unit 210 are buffered. The gamma reference voltages (+ GAMH, + GAML, -GAML, -GAMH) buffered by each of the buffers 600, 610, 620, and 630 are transferred to another adjacent source driver 117.

As described above, in the method of buffering the gamma reference voltage to the buffer, the input gamma reference voltage is buffered by the buffers 600, 610, 620, and 630 to supply the positive string portion 200 and the negative string portion 210. It passes to the source driver 117 of the next stage.

Therefore, the method of buffering the gamma reference voltage to the buffer may provide the gamma reference voltages to the plurality of source drivers 117 more stably than the method of bypassing the gamma reference voltage.

However, when the buffers 600, 610, 620, and 630 buffer the gamma reference voltages (+ GAMH, + GAML, -GAML, and -GAMH), the buffers 600, 610, 620, and 630 have different levels of offset. Since the voltage is generated, the voltage of the correct level according to the digital data cannot be output to the column line of the LCD panel 100, and thus the contrast of the image displayed on the LCD panel 100 is changed.

7 is a diagram showing the configuration of a gamma reference voltage supply circuit of the present invention. Referring to FIG. 7, the gamma reference voltage supply circuit of the present invention includes two buffers, and the two buffers alternately buffer the gamma reference voltages (+ GAMH and -GAMH) according to a frame signal so that the source driver ( A first gamma buffer 710 to be supplied to the 117 and two buffers, and the two buffers alternately buffer the gamma reference voltages (+ GAML and -GAML) in accordance with the frame signal so that the source driver 117 It is composed of a second gamma buffer unit 710 to be supplied to.

Here, each of the gamma reference voltages (+ GAMH, -GAMH) (+ GAML, -GAML) has symmetrical voltage levels, and polarities are different, but absolute voltage levels are the same.

The first gamma buffer unit 710 may alternately select gamma reference voltages (+ GAMH and −GAMH) having opposite polarities according to frame signals, respectively. And buffers 713-1 and 713-2 which respectively buffer the gamma reference voltages selected by the first and second switching units 711-1 and 711-2, and the buffers 713-1 and 713-2. A third switching unit 715-1 for supplying a gamma reference voltage (+ GAMH) to the source driver 117 according to the frame signal among the gamma reference voltages buffered by the respective ones, and the buffer 713-1. , 713-2 selects a gamma reference voltage (-GAMH) from the buffered gamma reference voltages according to the frame signal, and supplies it to the source driver 117.

The second gamma buffer unit 720 alternately selects gamma reference voltages (+ GAML and -GAML) having opposite polarities according to frame signals, respectively, in order to alternately select first and second switching units 721-1 and 721-2. ), Buffers 723-1 and 723-2 for respectively buffering the gamma reference voltages selected by the first and second switching units 721-1 and 721-2, and the buffers 723-1 and 723-. A third switching unit 725-1 which selects a gamma reference voltage (+ GAML) according to the frame signal among the gamma reference voltages buffered by 2) to the source driver 117, and the buffer 723-. 1 and 723-2 each include a fourth switching unit 725-2 which selects a gamma reference voltage (-GAML) from the buffered gamma reference voltages according to the frame signal and supplies it to the source driver 117. .

Each of the first and second switching units 711-1, 711-2, 721-1, and 721-2 is configured as, for example, a multiplexer, and is switched according to an input frame signal so that positive polarity and negative polarity are switched. Alternately select a gamma reference voltage, and each of the third and fourth switching units 715-1, 715-2, 725-1, and 725-2 is also composed of a multiplexer and is switched according to an input frame signal. The gamma reference voltages of plus and minus polarity are selected respectively.

In the gamma reference voltage supply circuit of the present invention configured as described above, the first and second switching units 711-1 and 711-2 of the first gamma buffer unit 710 have a gamma reference having positive polarity and negative polarity according to a frame signal. Alternately selects the voltage (+ GAMH, -GAMH).

The gamma reference voltages alternately selected by the first and second switching units 711-1 and 711-2 are buffered in the buffers 713-1 and 713-2, respectively, so that the third and fourth switching units 715-1 715-2).

Then, the third switching unit 715-1 may apply a positive polarity gamma reference voltage (+ GAMH) according to the frame signal among the gamma reference voltages buffered by the buffers 713-1 and 713-2, respectively. The fourth switching unit 715-2 selects and supplies the source driver 117, and the fourth switching unit 715-2 has a negative polarity according to the frame signal among the gamma reference voltages buffered by the buffers 713-1 and 713-2, respectively. The gamma reference voltage (-GAMH) is selected and supplied to the source driver 117.

For example, when the potential of the frame signal is high, the gamma reference voltage (+ GAMH) having a positive polarity is selected by the first switching unit 711-1 and buffered in the buffer 713-1, and the buffer 713- The gamma reference voltage + GAMH of the positive polarity buffered in 1) is selected by the third switching unit 715-1 and is supplied to the source driver 117. The gamma reference voltage of negative polarity (-GAMH) is selected by the second switching unit 711-2 and buffered in the buffer 713-2, and the gamma reference voltage of negative polarity buffered in the buffer 713-2 (−). The GAMH is selected by the fourth switching unit 715-2 and supplied to the source driver 117.

When the potential of the frame signal is low, the gamma reference voltage (+ GAMH) having a positive polarity is selected by the second switching unit 711-2 and buffered in the buffer 713-2, and the buffer 713-2. The gamma reference voltage (+ GAMH) having a positive polarity buffered at is selected by the third switching unit 715-1 and is supplied to the source driver 117. The negative polarity gamma reference voltage (-GAMH) is selected by the first switching unit 711-1 and buffered in the buffer 713-1, and the negative polarity gamma reference voltage (− GAMH) is buffered in the buffer 713-1. The GAMH is selected by the fourth switching unit 715-2 and supplied to the source driver 117.

That is, the first gamma buffer unit 710 receives two input buffers 713-1 and 713-2 according to the frame signal by inputting a gamma reference voltage (+ GAMH) having a positive polarity and a gamma reference voltage (-GAMH) having a negative polarity. ) Are alternately buffered and supplied to the source driver 117.

In addition, the second gamma buffer unit 720 receives the same gamma reference voltage (+ GAML) of positive polarity and a gamma reference voltage (-GAML) of negative polarity which are input in the same manner as the first gamma buffer unit 710 according to the frame signal. Since two buffers 723-1 and 723-2 are alternately buffered and supplied to the source driver 117, a detailed description of the operation is omitted.

As described above, the plus string unit 200 divides the gamma reference voltages (+ GAMH and + GAML) supplied from the first and second gamma buffer units 710 and 720 into a plurality of resistors to generate a plurality of positive voltages. The generated plurality of positive voltages are input to the plurality of plus digital / analog converters 220-1, 220-2,...

The negative string unit 210 divides the negative gamma reference voltages (-GAMH and -GAML) supplied from the first and second gamma buffer units 710 and 720 into a plurality of resistors to generate a plurality of negative voltages. The generated plurality of negative voltages are input to the plurality of negative digital-to-analog converters 230-1, 230-2, ....

Then, a plurality of plus digital / analog converters 220-1 and 220-2 are provided. Each of them selects a single plus voltage corresponding to the value of the input digital data so that the multiplexer 240-1, 240-2 (240-3, 240-4). And a plurality of negative digital-to-analog converters 230-1 and 230-2. Each of them selects a single negative voltage corresponding to the value of the input digital data, so that the multiplexers 240-1, 240-2 (240-3, 240-4). Will output

Each of the multiplexers 240-1, 240-2, 240-3, 240-4,..., Alternately selects a positive voltage and a negative voltage according to an input polarity selection signal POL. The positive and negative voltages selected by the multiplexers 240-1, 240-2, 240-3, 240-4,... Alternately are outputted as column lines of the LCD panel 100, and the predetermined voltages are output to the LCD panel 100. The image is displayed.

On the other hand, while the present invention has been shown and described with respect to specific preferred embodiments, various modifications and changes of the present invention without departing from the spirit or field of the invention provided by the claims below It can be easily understood by those skilled in the art.

For example, in the above description, two gamma buffer units are provided, and each gamma buffer unit has two gamma buffers, respectively, to alternately buffer the gamma buffer voltage. In the present invention, when there are a plurality of input gamma reference voltages, that is, when there are a plurality of gamma buffer voltages having opposite polarities and the same absolute value, a plurality of gamma buffer units are provided according to the plurality of gamma reference voltages. Various modifications can be made, such as the configuration of the gamma buffer voltage to be buffered.

As described in detail above, the present invention includes a plurality of gamma buffer parts according to input gamma reference voltages, and each of the plurality of gamma buffer parts has two gamma buffer voltages having opposite polarities and the same absolute value. Alternately buffers and feeds the source driver.

Therefore, when the gamma buffer unit buffers a plurality of gamma reference voltages, the offset voltage generated in the buffer is compensated, and thus a stable image can be displayed on the LCD panel.

Claims (5)

A source driver for converting input digital data into analog data and outputting the analog data to column lines of the LCD panel; And Converting the digital data into analog data in the source driver by alternately buffering two gamma reference voltages having two buffers and having opposite polarities and having the same absolute level in accordance with a frame signal. A gamma reference voltage supply circuit including a plurality of gamma buffer units for supplying a reference voltage for the reference. The display device of claim 1, wherein each of the plurality of gamma buffer parts comprises; First and second switching units alternately selecting gamma reference voltages having positive and negative polarities according to the frame signal; Two buffers respectively buffering the gamma reference voltage selected by the first and second switching units; And A third switching unit which selects a gamma reference voltage having a positive polarity from among the gamma reference voltages buffered by the two buffers according to the frame signal and supplies the same to the source driver; And And a fourth switching unit configured to select a gamma reference voltage having a negative polarity according to the frame signal from among the gamma reference voltages buffered by the two buffers and to supply the gamma reference voltage to the source driver. The method of claim 2, wherein each of the first to fourth switching unit; A gamma reference voltage supply circuit, characterized in that the multiplexer. The method of claim 1, wherein the source driver; A positive string unit generating a plurality of positive voltages by dividing a gamma reference voltage of positive polarity output by the first and second gamma buffer units; A negative string unit for generating a plurality of positive voltages by dividing a gamma reference voltage having negative polarity output by the first and second gamma buffer units; A plurality of plus digital / analog converters for selecting one plus voltage according to a value of digital data input from a graphic board among a plurality of plus voltages generated by the plus string unit; A plurality of negative digital-to-analog converters for selecting one minus voltage according to a value of digital data input from a graphics board among a plurality of minus voltages generated by the minus string unit; And And a plurality of multiplexers for selecting a positive voltage selected by the plurality of plus digital / analog converters or a negative voltage selected by the plurality of negative digital / analog converters according to a polarity selection signal and outputting them to the column electrodes of the LCD panel. Gamma reference voltage supply circuit. 5. The apparatus of claim 4, wherein each of the plus string portion and the minus string portion; A gamma reference voltage supply circuit, characterized in that a plurality of resistors are connected in series to divide the gamma reference voltage.

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