KR102293838B1 - Liquid Crystal Display Device and Driving Method thereof - Google Patents

Abstract

The present invention provides a liquid crystal display device including a liquid crystal panel and a data driver. The liquid crystal panel displays an image. The data driver is connected to the data lines of the liquid crystal panel and performs charge-sharing in the direction of the dominant polarity of the data voltage.

Description

Liquid Crystal Display Device and Driving Method thereof

The present invention relates to a liquid crystal display device and a driving method thereof.

As information technology develops, the market for display devices, which is a connection medium between users and information, is growing. Accordingly, a Flat Panel Display (FPD) such as a Liquid Crystal Display (LCD), an Organic Light Emitting Diode Display (OLED), and a Plasma Display Panel (PDP). ) is on the rise. Among them, a liquid crystal display capable of realizing a high resolution and capable of being miniaturized as well as enlarged is widely used.

The liquid crystal display includes a liquid crystal panel and a backlight unit. The liquid crystal panel includes a liquid crystal layer positioned between a transistor substrate on which a thin film transistor, a storage capacitor, and a pixel electrode are formed, and a color filter substrate on which a color filter and a black matrix are formed. The liquid crystal panel operates based on the gate signal supplied from the gate driver and the data voltage supplied from the data driver.

The liquid crystal display uses a charge sharing method of sharing charges to solve a power consumption problem caused by the driving characteristics of a data driver that inverts and outputs a data voltage to positive and negative polarities.

The charge-sharing method proposed in the prior art changes the liquid crystal panel to the middle level of the high potential voltage (VDD) by closing (ON) the switches of all channels of the data driver under all conditions without any special option to increase the dynamic current. lower it The charge-sharing method proposed in the prior art has room for improvement in order to reduce current consumption and lower the temperature generated during driving, so research on this is required.

SUMMARY OF THE INVENTION The present invention for solving the problems of the above-described background technology reduces the dynamic current consumed in the output amplifier of the data driver and lowers the temperature generated during driving.

As a means for solving the above problems, the present invention provides a liquid crystal display device including a liquid crystal panel and a data driver. The liquid crystal panel displays an image. The data driver is connected to the data lines of the liquid crystal panel and performs charge-sharing in the direction of the dominant polarity of the data voltage.

The data driver compares the data signals of the previous line and the current line to analyze the degree of direct current, and forms a charge share voltage in the negative direction if the current line dominates in the negative polarity direction. A charge share voltage can be formed in the direction

The data driver may form the charge share voltage at an intermediate level of the high potential voltage when the data signals of the previous line and the current line are the same.

The data driver includes a charge share unit that performs charge sharing, a comparison circuit unit that compares the data signal of the previous line and the data signal of the current line stored in the first latch and the second latch, and outputs a result value corresponding to the comparison result; and a charge control signal generator configured to output a charge control signal for controlling the charge share unit based on a result value transmitted from the circuit unit.

The charge sharing unit may include a first switch group including switches configured to perform charge sharing for each channel, and a second switch group including switches configured to perform charge sharing between the same polarity.

The first switch group performs a switching operation to form a charge share voltage at an intermediate level of the high potential voltage when the data signals of the previous line and the current line are the same, and the second switch group operates in a negative polarity direction when the current line dominates in the negative polarity direction. to form a charge share voltage, and if dominant in a positive polarity direction, a switching operation may be performed to form a charge share voltage in a positive polarity direction.

In another aspect, the present invention provides a method of driving a liquid crystal display. A method of driving a liquid crystal display device includes the steps of comparing a previous data signal of a previous line with a current data signal of a current line and calculating a degree of a direct current between them; and forming a charge share voltage in a negative polarity direction when the current line dominates in a negative polarity direction, and forming a charge share voltage in a positive polarity direction when the current line dominates in a positive polarity direction.

The forming of the charge share voltage may further include forming the charge share voltage at an intermediate level of the high potential voltage when the amounts of direct current between the previous line and the current line are all the same.

The present invention has the effect of reducing the dynamic current consumed by the output amplifier of the data driver by performing charge-sharing in the dominant direction of the polarity occupied in the image. In addition, according to the present invention, the load received by the output amplifier of the data driver is reduced by performing charge-sharing in the dominant direction of the polarity, so that the temperature generated during driving can be lowered.

1 is a block diagram schematically showing a liquid crystal display device;
FIG. 2 is a circuit diagram schematically illustrating the sub-pixel shown in FIG. 1;
3 is an exploded perspective view of a liquid crystal panel module according to an embodiment of the present invention;
4 is a waveform diagram for explaining a charge sharing method proposed in the related art;
5 is a block diagram schematically illustrating an internal configuration of a data driver according to an embodiment of the present invention;
6 is a waveform diagram illustrating a charge sharing method according to an embodiment of the present invention.
7 is a flowchart illustrating a charge sharing method according to an embodiment of the present invention.
8 is an exemplary view illustrating a charge control unit according to an embodiment of the present invention;
9 is an exemplary view illustrating a charge share unit according to an embodiment of the present invention;

Hereinafter, specific details for carrying out the present invention will be described with reference to the accompanying drawings.

1 is a block diagram schematically showing a liquid crystal display device, FIG. 2 is a circuit diagram schematically showing a sub-pixel shown in FIG. 1, and FIG. 3 is an exploded perspective view of a liquid crystal panel module according to an embodiment of the present invention, 4 is a waveform diagram illustrating a conventionally proposed charge sharing method.

1 and 2 , the liquid crystal display includes a timing controller 130 , a gate driver 140 , a data driver 150 , a liquid crystal panel 160 , and a backlight unit 170 .

The timing controller 130 outputs a gate timing control signal GDC for controlling the operation timing of the gate driver 140 and a data timing control signal DDC for controlling the operation timing of the data driver 150 . The timing controller 130 supplies the data signal DATA supplied from the image processor 110 together with the data timing control signal DDC to the data driver 150 .

The gate driver 140 outputs a gate signal while shifting the level of the gate voltage in response to the gate timing control signal GDC supplied from the timing controller 130 . The gate driver 140 supplies a gate signal to the sub-pixels SP included in the liquid crystal panel 160 through the gate lines GL. The gate driver 140 is formed in the form of an integrated circuit (IC) or is formed in the liquid crystal panel 160 in the form of a gate in panel.

The data driver 150 samples and latches the data signal DATA in response to the data timing control signal DDC supplied from the timing controller 130 , converts it into a gamma reference voltage, and outputs it. The data driver 150 may output by inverting the polarity of the data voltage in one frame cycle. The data driver 150 supplies a data voltage (or a data signal) to the sub-pixels SP included in the liquid crystal panel 160 through the data lines DL. The data driver 150 is formed in the form of an integrated circuit (IC).

The liquid crystal panel 160 displays an image in response to the gate signal supplied from the gate driver 140 and the data voltage supplied from the data driver 150 . The liquid crystal panel 160 includes sub-pixels SP that control the light provided through the backlight unit 170 .

One sub-pixel includes a switching transistor SW, a storage capacitor Cst, and a liquid crystal layer Clc. The gate electrode of the switching transistor SW is connected to the gate line GL1 , and the source electrode is connected to the data line DL1 . One end of the storage capacitor Cst is connected to the drain electrode of the switching transistor SW and the other end is connected to the common voltage line Vcom. The liquid crystal layer Clc is formed between the pixel electrode 1 connected to the drain electrode of the switching transistor SW and the common electrode 2 connected to the common voltage line Vcom.

The liquid crystal panel 160 has a TN (Twisted Nematic) mode, VA (Vertical Alignment) mode, IPS (In Plane Switching) mode, FFS (Fringe Field Switching) mode depending on the structure of the pixel electrode 1 and the common electrode 2 . Alternatively, it is implemented in an Electrically Controlled Birefringence (ECB) mode. The liquid crystal panel 160 may be implemented as red, green, and blue sub-pixels or as white sub-pixels along with red, green, and blue sub-pixels to reduce current consumption.

The backlight unit 170 provides light to the liquid crystal panel 160 using a light source that emits light. The backlight unit 170 includes a light emitting diode (hereinafter LED), an LED driving unit for driving the LED, an LED board on which the LED is mounted, a light guide plate that converts the light emitted from the LED into a surface light source, a reflector that reflects light from the lower part of the light guide plate, and optical sheets for condensing and diffusing the light emitted from the light guide plate.

The liquid crystal panel 160 and the backlight unit 170 are accommodated by a cover or the like and manufactured as a liquid crystal panel module, which will be schematically described as follows.

As shown in FIG. 3 , the liquid crystal panel modules 160 , 165 , and 170 have a cover bottom 171 positioned below the backlight unit 170 and a cover top 165 positioned above the liquid crystal panel 160 . has a structure housed by

The cover bottom 171 and the support main 177 accommodate the LED 174 , the reflective plate (or reflective sheet) 172 , the light guide plate 175 , and a plurality of light diffusion sheets 176 . And the cover top 165 and the support main 177 accommodate the liquid crystal panel 160 and the like.

Hereinafter, a configuration positioned between the cover bottom 171 and the cover top 165 and their functions will be described.

The reflector 172 is seated on the cover bottom 171 . The reflector 172 serves to reflect light from the lower portion of the light guide plate.

The light guide plate 175 is mounted on the reflection plate 172 . The light guide plate 175 serves to convert the light emitted from the LED 174 into a surface light source. The LED substrate 173 on which the LED 174 is mounted is installed on the light incident part (or the other side) of the light guide plate 175 .

A plurality of light diffusion sheets 176 are mounted on the light guide plate 175 . The plurality of light diffusion sheets 176 serve to condense and diffuse the light emitted from the light guide plate 175 . The plurality of light diffusion sheets 176 are composed of sheets having one or more different structures and functions.

The support main 177 is seated on the cover bottom 171 . The support main 177 supports the liquid crystal panel 160 , and serves to fix a plurality of optical expansion sheets 176 and the like to be safely accommodated in the cover bottom 171 . The support main 177 has a frame shape capable of passing the light emitted through the plurality of light diffusion sheets 176 .

The liquid crystal panel 160 is seated on the support main 177 . The liquid crystal panel 160 serves to display an image. The liquid crystal panel 160 includes a lower substrate 160a on which a switching transistor is formed, an upper substrate 160b on which a color filter is formed, and a liquid crystal layer formed therebetween. The liquid crystal panel 160 is accommodated by the cover top 165 and the support main 177 . The cover top 165 has a frame shape that can expose the display area of the liquid crystal panel 160 .

The liquid crystal display device described above inverts the polarity of the data voltage in units of horizontally and vertically adjacent sub-pixels by adopting a dot inversion method in order to reduce a DC offset component and reduce liquid crystal deterioration. The polarity of the data voltage is determined based on the common voltage. The positive (+) data voltage is selected within a range higher than the common voltage, and the negative (-) data voltage is selected within a range lower than the common voltage.

However, in this dot inversion method, since the data voltage applied to the same data line must swing between the positive polarity (+) and the negative polarity (-) every horizontal period, the number of data transitions increases by the vertical resolution. For this reason, the liquid crystal display uses a charge sharing method in which charges are shared in order to solve the current consumption problem caused by the driving characteristics of the data driver that inverts the data voltage into positive and negative polarity and outputs it. .

In FIG. 4 , SOE denotes a source output enable signal, N, N+1 to N+3 denote horizontal lines (or horizontal periods) such as the current line and the next line, and the C/S section denotes charge sharing. This means the period in which this occurs. As can be seen from the drawings, the conventionally proposed charge-sharing method switches (SW1 to SWN) of all channels (CH1 to CHN) of the data driver under all conditions without any special selection in response to the source output enable signal (SOE). By closing (ON), the liquid crystal panel changes to an intermediate level of the high potential voltage (VDD) to lower the dynamic current.

The charge-sharing method proposed in the prior art has room for improvement in order to reduce current consumption and lower the temperature generated during driving, so research on this is required.

5 is a block diagram schematically showing an internal configuration of a data driver according to an embodiment of the present invention, FIG. 6 is a waveform diagram for explaining a charge sharing method according to an embodiment of the present invention, and FIG. It is a flowchart for explaining a charge sharing method according to an embodiment of the present invention, FIG. 8 is an exemplary diagram illustrating a charge controller according to an embodiment of the present invention, and FIG. 9 is a charge sharing unit according to an embodiment of the present invention. It is an example diagram shown.

5 to 7 , in the data driver according to an embodiment of the present invention, a shift register (SR), a first latch (LAT1; 1'st latch), and a second latch (LAT2; 2) 'nd latch), a DA conversion unit (DAC; PDAC and NDAC), a switch array 143 , a charge control unit 141 , and a charge share unit 145 . The output amplifier positioned at the rear end of the charge share unit 145 is omitted.

The data driver according to the operations of the shift register SR, the first and second latches LAT1 and LAT2, the DA converter DAC, the switch array 143, the charge controller 141, and the charge share part 145 It converts a digital data signal into a data voltage and outputs it through its own output channels (CH1 to CHN). Hereinafter, the configuration included in the data driver will be schematically described as follows.

The shift register SR outputs a sampling signal in response to a source start pulse and a source sampling clock output from the timing controller. The first and second latches LAT1 and LAT2 sequentially sample a digital data signal in response to a sampling signal output from the shift register SR, and data corresponding to one line sampled in response to a source output enable signal. signals are output at the same time.

The DA converter DAC converts a data signal corresponding to one line into an analog data voltage in response to the first to nth gamma grayscale voltages output from the gamma voltage generator (not shown) and outputs the converted data voltage. The DA converter (DAC) is a positive DA converter (PDAC) and a negative DA converter that converts the gamma grayscale voltage into positive (+) and negative (-) data voltages in response to the polarity control signal output from the timing controller. and a converter NDAC.

The source start pulse is a signal that controls the data sampling start timing of the data driver. The source sampling clock is a signal that controls the data sampling timing of the data driver based on a rising or falling edge. The source output enable signal is a signal for controlling the output timing of the data driver. The polarity control signal is a signal for controlling the vertical polarity of data voltages output to the data driver.

The switch array 143 operates so that the positive data voltage and the negative data voltage output from the positive DA conversion unit PDAC and the negative DA conversion unit NDAC are alternately output to adjacent channels. The switch array 143 is installed or omitted at the rear end of the DA conversion unit DAC according to a rendering method and a driving method of the sub-pixels included in the liquid crystal panel.

The charge share unit 145 is located at the rear end of the switch array 143 or at the rear end of the DA conversion unit DAC (when there is no switch array). The charge share unit 145 selectively connects (or shorts) the data lines so that charges (or data voltages) remaining in the data lines of the liquid crystal panel are shared. The charge share unit 145 selectively connects (or shorts) the data lines in response to the charge control signal CS output from the charge control unit 141 .

The charge control unit 141 controls the charge share unit 145 . The charge control unit 141 analyzes the degree of the DC amount between the previous line and the current line, and controls the charge share unit 145 to change the charge share level under conditions favorable to the current charge sharing operation. The charge control unit 141 refers to the source output enable signal SOE and outputs a charge control signal CS for controlling the charge share unit 145 based on the data signals applied to the previous line and the current line.

The charge control unit 141 calculates the amount of direct current for each line (S110). The charge control unit 141 compares the degree of the DC amount between the previous line N-1 and the current line N in order to calculate the DC amount for each line (S120). The degree of the DC amount can be found by comparing the previous data signal stored in the previous line N-1 of the latch with the current data signal stored in the current line N. For example, the charge controller 141 may calculate the DC level by summing the data signals of the previous line N-1 and the current line N, but is not limited thereto.

When the amount of direct current between the previous line (N-1) and the current line (N) is the same (Yes), the charge controller 141 controls all channels (CH1 to CHN, All Channels) of the data driver to share a charge in common. A signal is output (S125).

The charge control unit 141 differs in the amount of direct current between the previous line (N-1) and the current line (N), but if the current line (N) dominates in the positive (+) direction (Yes), the positive (+) prevails A signal for controlling the charge-sharing in the direction is output (S135).

The charge control unit 141 differs in the amount of direct current between the previous line (N-1) and the current line (N), but when the current line (N) dominates in the negative (-) direction (No), the negative (-) prevails A signal for controlling the charge-sharing in the direction is output (S140).

The charge control unit 141 controls the charge share unit 145 in the same manner as above. The charge share voltage applied to the output channels CH1 to CHN of the data driver is at the intermediate level of the high potential voltage VDD and has a positive polarity. It changes to a voltage in the (+) direction or a voltage in the negative (-) direction. In FIG. 6 , the C/S section means a section in which charge sharing occurs.

8 and 9 , the charge control unit 141 includes a comparison circuit unit COP and a charge control signal generation unit CSG. The charge share unit 145 includes a first switch group SWG1 , a second switch group SWG2 , and a third switch group SWG3 . The third switch group SWG3 may be omitted.

9, P and N mean the positive DA conversion unit and the negative DA conversion unit included in the DA conversion unit (DAC), SWM means the switches included in the switch array 143, +5, - 67, +45 to +16, and -230 represent grayscale voltages.

The comparison circuit unit COP compares the data signal of the previous line and the data signal of the current line stored in the first latch LAT1 and the second latch LAT2 and takes the result value (or signal) corresponding to the comparison result as a charge control signal It is transmitted to the generator (CSG).

The charge control signal generating unit CSG refers to the source output enable signal SOE, but the first to third charge controls for controlling the charge share unit 145 based on the result value transmitted from the comparison circuit unit COP. Outputs the signals CS1 to CS3.

The first switch group SWG1 operates in response to the first charge control signal CS1 output from the charge control signal generator CSG. The second switch group SWG2 operates in response to the second charge control signal CS2 output from the charge control signal generator CSG. The third switch group SWG3 operates in response to the third charge control signal CS3 output from the charge control signal generator CSG.

The first switch group SWG1 includes switches configured to perform charge sharing for each channel of the data driver. The switches included in the first switch group SWG1 are configured to electrically connect adjacent output lines. To this end, the switches included in the first switch group SWG1 have one end and the other end connected between the first output line and the second output line. The switches included in the first switch group SWG1 are turned on to short-circuit all output lines in response to the first charge control signal CS1 supplied to the switch electrode.

The second switch group SWG2 includes switches configured to perform charge sharing between the same polarity. The switches included in the second switch group SWG2 are configured to electrically connect output lines having the same polarity. To this end, switches included in the second switch group SWG2 have positive polarity switches and negative polarity switches.

Switches for positive polarity have one end and the other end connected between the first output line and the second output line. The switches for positive polarity included in the second switch group SWG2 are turned on to short-circuit output lines having a voltage corresponding to the same polarity as the second charge control signal CS2 supplied to the switch electrode.

Similarly, the switches for negative polarity also have one end and the other end connected between the first output line and the second output line. The switches for the negative polarity included in the second switch group SWG2 are also turned on to short-circuit output lines having a voltage corresponding to the same polarity as the second charge control signal CS2 supplied to the switch electrode.

The third switch group SWG3 includes switches configured to perform charge sharing in units of sub-pixels. The switches included in the third switch group SWG3 are configured to electrically connect the output lines of sub-pixel units. To this end, the switches included in the third switch group SWG3 have switches for the red sub-pixel, switches for the green sub-pixel, and switches for the blue sub-pixel, or further have switches for the white sub-pixel.

One end and the other end of the switches for the red sub-pixel are connected between the first output line and the second output line. The switches for the red sub-pixel included in the third switch group SWG3 are turned on to short-circuit output lines corresponding to the same sub-pixel as themselves in response to the third charge control signal CS3 supplied to the switch electrode. The switches for the green sub-pixel included in the third switch group SWG3 are turned on to short-circuit output lines corresponding to the same sub-pixel as themselves in response to the third charge control signal CS3 supplied to the switch electrode. The switches for the blue sub-pixel included in the third switch group SWG3 are turned on to short-circuit output lines corresponding to the same sub-pixel as themselves in response to the third charge control signal CS3 supplied to the switch electrode.

The charge share unit 145 further includes a mux group MUXG in addition to the first switch group SWG1 , the second switch group SWG2 , and the third switch group SWG3 . The mux group MUXG is located (or installed) at the end of the charge share unit 145 .

When the charge sharing unit 145 only performs charge sharing for each channel or charge sharing between the same polarities, the mux group MUXG may be omitted. However, since the charge share unit 145 has to output only the charge share voltage corresponding to the charge sharing type (charge share common to all channels, charge share in the polarity dominant direction) through the output terminal, it is not necessary to configure the MUXG. desirable.

An input terminal of the mux group MUXG is connected to one end of the first switch group SWG1, the second switch group SWG2, and the third switch group SWG1 to SWG3, respectively. And output terminals of the mux group MUXG are respectively connected to the output channels CH1 to CHN of the data driver. The mux group MUXG may operate based on the first to third charge control signals CS1 to CS3 output from the charge control unit 141 , but is not limited thereto.

The mux group MUXG operates to output the first charge share voltage formed by the first switch group SWG1 when the first switch group SWG1 operates. The mux group MUXG operates to output the second charge share voltage formed by the second switch group SWG2 when the second switch group SWG2 operates. The mux group MUXG operates to output the third charge share voltage formed by the third switch group SWG3 when the third switch group SWG3 operates.

As described above, the present invention has the effect of reducing the dynamic current consumed by the output amplifier of the data driver by performing charge-sharing in the dominant direction of the polarity occupied by the image. In addition, according to the present invention, the load received by the output amplifier of the data driver is reduced by performing charge-sharing in the dominant direction of the polarity, so that the temperature generated during driving can be lowered.

Although the embodiments of the present invention have been described above with reference to the accompanying drawings, the technical configuration of the present invention can be changed to other specific forms by those skilled in the art to which the present invention pertains without changing the technical spirit or essential features of the present invention. It will be appreciated that this may be practiced. Therefore, it should be understood that the embodiments described above are illustrative in all respects and not restrictive. In addition, the scope of the present invention is indicated by the claims to be described later rather than the above detailed description. In addition, all changes or modifications derived from the meaning and scope of the claims and their equivalents should be construed as being included in the scope of the present invention.

130: timing controller 140: gate driver
150: data driver 160: liquid crystal panel
170: backlight unit 141: charge control unit
145: charge share unit COP: comparison circuit unit
CSG: charge control signal generator LAT1, LAT2: first and second latches
CS1 to CS3: first to third charge control signals
SWG1 ~ SWG3: 1st to 3rd switch group

Claims (11)

a liquid crystal panel for displaying an image; and
and a data driver connected to the data lines of the liquid crystal panel and performing charge-sharing in a direction of a dominant polarity of the data voltage;
The data driver
Analyzes the degree of direct current by comparing the data signals of the previous line and the current line. If the current line dominates in the negative direction, a charge share voltage is formed in the negative direction. If the current line dominates in the positive direction, it is charged in the positive direction. A liquid crystal display that forms a share voltage. delete According to claim 1,
The data driver
A liquid crystal display device that forms a charge share voltage at an intermediate level of a high potential voltage when the data signals of the previous line and the current line are the same. According to claim 1,
The data driver
a charge sharing unit that performs the charge sharing;
a comparison circuit unit for comparing the data signal of the previous line and the data signal of the current line stored in the first latch and the second latch and outputting a result value corresponding to the comparison result;
and a charge control signal generating unit configured to output a charge control signal for controlling the charge share unit based on the result value transmitted from the comparison circuit unit. 5. The method of claim 4,
The charge share unit
a first switch group including switches configured to perform charge sharing on a per channel basis;
A liquid crystal display including a second switch group including switches configured to perform charge sharing between the same polarity. 6. The method of claim 5,
The first switch group performs a switching operation to form a charge share voltage at an intermediate level of the high potential voltage when the data signals of the previous line and the current line are the same;
The second switch group performs a switching operation to form a charge share voltage in a negative polarity direction when the current line dominates in a negative polarity direction, and forms a charge share voltage in a positive polarity direction when the current line dominates in a positive polarity direction. Comparing the previous data signal of the previous line and the current data signal of the current line, calculating a degree of direct current between them; and
and forming a charge share voltage in a negative polarity direction when the current line dominates in a negative polarity direction and forming a charge share voltage in a positive polarity direction when the current line dominates in a positive polarity direction. 8. The method of claim 7,
The step of forming the charge share voltage is
and forming a charge share voltage at an intermediate level of a high potential voltage when the amount of direct current between the previous line and the current line is the same. According to claim 1,
The data driver
a DA converter that converts the data signal into an analog data voltage and outputs it;
a charge sharing unit that performs the charge sharing;
and an output amplifier positioned at a rear end of the charge share unit. 10. The method of claim 9,
The charge share unit
a first switch group including switches configured to perform charge sharing for each channel of the data driver;
a second switch group comprising switches configured to perform charge sharing between the same polarity;
A liquid crystal display including a third switch group including switches configured to perform charge sharing in units of sub-pixels. 11. The method of claim 10,
The data driver
Further comprising a mux group located at the end of the charge share,
The mux group
When the first switch group operates, it operates to output the first charge share voltage formed by the first switch group, and when the second switch group operates, outputs the second charge share voltage formed by the second switch group and outputting a third charge share voltage formed by the third switch group when the third switch group operates.

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