TWI384451B - Liquid crystal display device and driving device thereof - Google Patents

Description

Liquid crystal display device and driving device thereof

The present invention relates to a liquid crystal display device and a driving device thereof, and more particularly to a liquid crystal display device having a display with high display quality and a driving device therefor.

The first figure shows a schematic structural view of a typical liquid crystal display device 1.

The liquid crystal display device 1 includes a liquid crystal element array 2, a gate line driving circuit 7, and a source bus line driving circuit 8, wherein the liquid crystal element array 2 is composed of a liquid crystal cell 3 arranged in a matrix form.

Each of the liquid crystal elements 3 is constructed by a thin film transistor 4, a liquid crystal display element 5, and an auxiliary capacitor 6; wherein the liquid crystal display element 5 is connected to a capacitor between the drain of the thin film transistor 4 and the ground, and the auxiliary capacitor 6 is connected in parallel, and the gate and source of the thin film transistor 4 are respectively connected to the gate line and the source bus.

In addition, the gate line driving circuit 7 sequentially drives the gate lines of the respective rows, and the thin film transistors of the liquid crystal elements of the respective rows are commonly connected to the respective gate lines. Furthermore, the source bus bar driving circuit 8 provides a voltage signal to the sources of the respective thin film transistors of the liquid crystal cells of the respective columns connected in common to the source bus bar.

The liquid crystal display device must have a hue display. When a pixel is displayed, the data code corresponding to the hue is transmitted to the driving device, and is converted into a voltage signal corresponding to the data code by the driving device. The voltage signal is transmitted to the source line of the liquid crystal element of the pixel connected to the drain of the thin film transistor, and a high voltage is transmitted to the gate line to turn on the gate of the thin film transistor, so that The voltage signal is transmitted to the liquid crystal cell to change the transmittance to obtain a desired image.

At this time, the relationship between the data code and the driving voltage is nonlinear, and has a characteristic called a gamma curve. The second figure is a schematic diagram of the structure of the voltage corresponding to the gamma curve in the prior art.

The figure shows the relationship between the data and the voltage. As shown in the figure, it can obtain 256-tone voltage, and its corresponding data code is 0 to 255, which can also be transmitted by 8-bit data. Get the voltage you want.

First, in order to obtain the voltage range, 17 kinds of voltages, such as V0 to V16, are taken out from a reference voltage generator 10, wherein the reference voltage generator 10 is composed of 18 resistor dividers connected in series between the power source and the ground. Seventeen voltages (V0 to V16) are obtained by resistor division. Using the upper 4 bits of the data and the 4-bit switch matrix selector 20, 16 voltage ranges can be selected, the output voltage range is V _n and V _n+1 ; and the lower 4 bits and 4 bits of the data are reused. The meta-linear digital analog converter (DAC) 30 can select any one of 16 voltages in the selected voltage range. In the example shown in the second figure, the voltage indicating the output falls within the voltage range V14-V15, and is assigned to any one of the data codes 223 to 239.

The third drawing is a schematic block diagram of a driving device for a color liquid crystal display device which applies a source voltage to a source bus bar; wherein the same portions as those of the second figure are denoted by the same reference numerals. The driving device shown in the third figure supplies voltage to two columns of liquid crystal elements, wherein each column of liquid crystal elements includes three color components (R, G, B).

At this time, when the voltage data of the red (R) liquid crystal element applied to a certain pixel in the nth column is supplied, as in the description of the second figure, 17 kinds of voltage values are taken out from the reference voltage generator 10, and then The voltage selector 20 of the 4-bit DA converter selects two voltage values V _n and V _n+1 corresponding to the upper 4 bits of the voltage data from 16 voltage ranges of 17 voltage values; The two voltage values V _n and V _n+1 are applied to the source bus bar of the pixel column, and are transmitted to the 4-bit lower-order bit DA converter 31 to obtain a corresponding data value and fall on the The voltage within the voltage range. The buffer 41 stabilizes the voltage; the stabilized voltage is applied to the source busbar SB1R of the red pixel line by a 1-to-3 demultiplexer 51. Further, a precharge circuit 60 is provided in order to prevent the display operation from being delayed due to a large voltage fluctuation in each of the source bus bars.

With the above configuration, when a voltage is applied to a column of source busbars, pre-charging is first performed to prepare and drive the red column of the first column, and then the green column of the first column is prepared and driven, and then Prepare and drive the blue column of the first column. As described in U.S. Patent Publication No. 2004-0174347.

However, the above structure has a drawback in that it is affected by a voltage change when driving adjacent columns.

That is, when the red column of the first column is driven, the green column is driven in a state in which the source bus bar forms the voltage V1; when the voltage rises, the red column also has a potential increase due to the voltage rise. It is caused by the parasitic capacitance coupling between the source busbars. Similarly, the adjacent source bus bars are affected by voltage fluctuations, which will cause damage to the picture image.

Therefore, if two rows of units are to be driven, the following method will be used. First, when the red column of the first column is driven, it will be prepared first. The red column of the second column is driven; in the red column driver of the second column, the green column of the first column is also prepared for driving; thus, the driving is performed in two columns.

However, in the driving of such two columns of units, each column needs to be precharged, and thus it is necessary to provide a precharge circuit. Therefore, it consumes a lot of power and cannot meet the requirements of reducing power consumption.

The driving device of the liquid crystal display device of the present invention drives a liquid crystal display element by supplying a source voltage to a color tone, and the driving device includes: a reference voltage generator that generates a set voltage, the set voltage is applied to the color tone a range of voltages; a first digital analog converter that extracts a value representing a voltage range from a reference voltage generator through a level bit of a data code, wherein the tone voltage corresponds to one of the liquid crystal elements of the liquid crystal display device; a second and a third digital analog converter configured in two columns, wherein the second and a third digital analog converter selects a voltage range specified by the first digital analog converter according to a lower order bit of the data code a second value and a third digital analog converter selectively outputting detailed values; and a demultiplexer selectively connecting the outputs of the second and third digital analog converters to the even columns Any one column.

Since the present invention does not perform pre-charging, pre-driving is performed to raise the potential to a value close to that originally required, so that the voltage shift of the source bus bar is small, thereby maintaining good display quality.

In addition, since the pre-charge circuit is not required, the portion can be reduced The circuit area is also simple, so the cost can be reduced.

Furthermore, a buffer amplifier with lower speed and lower power than the previous DA conversion system can be used.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the preferred embodiments will be described in detail with reference to the accompanying drawings.

The fourth drawing is a block diagram of a driving device of a liquid crystal display device according to an embodiment of the present invention, and is described in comparison with the conventional structure shown in the third figure. In addition, this embodiment also illustrates a structure including two pixel columns of three color compositions.

The reference voltage generator 110 for obtaining the voltage range has a similar structure to that shown in the third figure, and has 18 resistor dividers connected in series between the power source and the ground to obtain V0 to V16 by resistor division, etc. 17 Kind of voltage. The 17 voltages are transferred to the voltage selector 120 of the 4-bit DA converter by a 17-bit bus.

The voltage selector 120 outputs the voltage values V _n and V _n+1 within the display voltage range corresponding to the upper 4 bits of the transmitted data.

The voltage values V _n and V _{n+1 are} transferred to a 4-bit linear digital analog converter (DAC) 131 and a 4-bit linear digital analog converter (DAC) 132.

The DACs 131 and 132 correspond to any of the 16 voltages within the specified voltage range of the lower 4-bit output of the data, and the outputs are stabilized by the negative feedback buffers 141, 142, respectively. In addition, a two-to-six-demultiplexer 152 is connected between the two input sides and the six output sides, and by the action of the two-to-six-demultiplexer 152, three colors can be formed in two columns. 6 source busbars SB1R, SB1G, SB1B, SB2R, SB2G, SB2B are arbitrarily selected and applied with an output voltage.

In addition, unlike the third figure, in this embodiment, the pair is The 4-bit linear digital analog converters (DACs) 131 and 132 input the pre-drive signal PRD, and the buffers 141, 142 are also different from the buffers 41, 42 in the third figure. This embodiment is a negative feedback connection operational amplifier. . In this embodiment, one 2-pair 6-demultiplexer is configured instead of the two 1-to-3 demodulators shown in the third figure, and in this example, there is no need to configure a pre-charge circuit.

The fifth diagram shows a circuit diagram of the 4-bit linear digital analog converter (DAC) 131 connected to the buffer 141 in the present invention.

In the circuit diagram shown, the range enclosed by dotted lines represents a conventional 4-bit linear digital analog converter (DAC) 31 having five parallel capacitors, one of which is commonly grounded at one end and has a capacitance Take C as the unit capacitance, which is 1C, 1C, 2C, 4C, 8C. The other end of each of these capacitors are respectively connected to the switch SW10, SW11, SW12, SW13, SW14, the voltage selector for two voltage values output from the switch 120 ₁ to V _n and V _{n +;} and such a capacitor They are also connected to switches SW20, SW21, SW22, SW23, SW24, respectively, and are controlled by the pre-drive signal PRD. The other ends of the switches SW20, SW21, SW22, SW23, SW24 are commonly connected to the buffer 141. Further, also a switch SW25, to the pre-driver control signal by the PRD and the direct voltage V _n input buffers, wherein the line switching switch SW25 SW20, SW21, SW22, SW23, SW24 and opposite to the operation. In addition, the switch SW25 can also supply the voltage Vn ₊₁ to the buffer as indicated by the broken line in the fifth figure.

FIG. 6 is a timing diagram showing the operation of the circuit in accordance with the fourth and fifth figures. Here, a total of six columns of two columns of three color components are taken as an example, and the source voltage is supplied to the source bus bar as an example.

Now let's take n=1 as an example, and in the fourth figure, 6 source busbars SB1R, SB1G, SB1B, SB2R, SB2G, SB2B supply source voltage.

The sixth figure shows the two actions shown in [A][B] interactively; that is, the setting and pre-driving of the first column are performed during the initial period, and the voltage specified by the data code is driven, and the The second column is set and pre-driven; when the second column is driven during the connection period, the third column is set and pre-driven; in the same manner, the setting and pre-driving time history are alternately repeated between the two columns. Drive the time course.

The voltage selector 120 selects two voltages V _n and V _{n+1 of the} display voltage range among the 17 voltage values taken out from the reference voltage generator 10 shown in FIG. 4 according to the upper order bits of the data code, and It is supplied to two 4-bit linear digital analog converters (DACs) 131 and 132.

These 4-bit linear digital analog converters (DACs) 131 and 132 are connected as shown in the fifth figure to five capacitors having unit capacitances 1C, 1C, 2C, 4C, and 8C, respectively, to voltages V _n or V _{n+ . 1} , and the switches SW10, SW11, SW12, SW13, SW14 are switched according to the order 4 bits below the data code.

The driving voltage applied to the source busbar is set according to the data of the order bits below the data code. Specifically, the switches SW20, SW21, SW22, SW23, and SW24 of the fifth figure are open, and the switching of the switches SW10, SW11, SW12, SW13, and SW14 is controlled according to the data of the order 4 bits below the data code. In addition, five capacitors having unit capacitances 1C, 1C, 2C, 4C, and 8C are respectively connected to the voltage V _n or V _{n+1 to} charge the capacitors. That is to say, taking the switch SW10 as an example, even if the data is 0000, the lowest voltage can be generated, and the voltage of V _n+1 can still be supplied to the capacitor.

Further, the pre-driver supplies the voltage V _n+1 (in the present case, V2) to the buffer by turning off the switch SW25. Therefore, the setting and pre-driving can be performed at the same time. As a result of the pre-drive, the voltage of the first column will rise to the value output from the voltage selector 120, as shown in the voltage waveform diagram of the source bus bar of the sixth figure.

In the second period, the voltages stored in the capacitors of the 4-bit linear digital analog converter (DAC) 131 by turning off the switches SW20, SW21, SW22, SW23, SW24 are supplied to the drive voltage specified by the data code. Buffer amplifier 141. Then, the demultiplexer 152 supplies the output of the buffer amplifier 141 to one of the six rows as the driving voltage (in the case of this example, V1).

In addition, the adjacent 4-bit linear digital analog converter (DAC) 132 delays the timing shown in the sixth figure to start the same operation, as shown in [B]. That is, during the driving of the first column, the setting and pre-driving of the second column are simultaneously performed; and when the driving voltage is output during the subsequent period, the demultiplexer 152 switches the number of columns to be supplied with the driving voltage, and supplies the driving voltage. V2.

Furthermore, when driving the second column, [A] performs the setting and pre-driving of the third column. The same action is performed below.

As described above, in the present invention, since the pre-drive of the voltage supplied to the display voltage range is simultaneously performed in the set period, it is not necessary to provide the precharge circuit. Therefore, the circuit area can be reduced, and the power can be reduced, and the cost can be reduced.

In addition, since the pre-drive causes the source busbar potential to rise to a value close to the original driving voltage, the voltage fluctuation caused by the driving of the adjacent pixels (the ΔVc' caused by V2-Vin in the sixth figure) is also reduced, so the vision The damage of the effect is also less. Furthermore, those skilled in the art will understand that the present invention is not limited to the above embodiments, and the modified examples and the like are included in the present invention. Within the scope of the invention.

For example, the number of columns to which the present invention is applied can be applied to any even column other than two columns and six columns.

Further, such a liquid crystal display device is suitable as the display device 1 of the portable telephone device 100 shown in FIG. 7, but is not limited to a portable telephone device, and is also applicable to a digital camera, a personal digital assistant (PDA), and a notebook type. Any kind of electronic device such as a computer, a desktop computer, a television, a car display, or a portable DVD player.

1‧‧‧Liquid crystal display device

2‧‧‧Liquid array

3‧‧‧Liquid crystal components

4‧‧‧film transistor

5‧‧‧Liquid display components

6‧‧‧Auxiliary capacitor

7‧‧‧ gate line driver circuit

8‧‧‧Source busbar drive circuit

10‧‧‧Reference voltage generator

20‧‧‧Voltage selector

30‧‧‧4-bit linear digital analog converter (DAC)

31‧‧‧4 bit lower level bit DA converter

41‧‧‧buffer

42‧‧‧buffer

51‧‧‧1 to 3 solution multiplexer

60‧‧‧Precharge circuit

110‧‧‧Reference voltage generator

120‧‧‧Voltage selector

131‧‧‧4-bit linear digital analog converter (DAC)

132‧‧‧4-bit linear digital analog converter (DAC)

141‧‧‧Negative feedback buffer

142‧‧‧Negative feedback buffer

152‧‧ ‧ multiplexer

223~239‧‧‧Information Code

PRD‧‧‧ pre-drive signal

SB1B‧‧‧Source Busbar

SB1G‧‧‧Source Busbar

SB1R‧‧‧ source busbar

SB2B‧‧‧ source busbar

SB2G‧‧‧Source Bus

SB2R‧‧‧ source busbar

SW10‧‧‧ switch

SW11‧‧‧ switch

SW12‧‧‧ switch

SW13‧‧‧ switch

SW14‧‧‧ switch

SW20‧‧‧ switch

SW21‧‧‧ switch

SW22‧‧‧ switch

SW23‧‧‧ switch

SW24‧‧‧ switch

SW25‧‧‧ switch

V _n ‧‧‧ voltage

V _n+1 ‧‧‧ voltage

The first figure shows a schematic structural view of a typical liquid crystal display device 1.

The second figure is a schematic diagram of the structure of the voltage corresponding to the gamma curve in the prior art.

The third drawing is a schematic block diagram showing the configuration of a driving device of a color liquid crystal display device.

The fourth drawing is a block diagram of a driving device of a liquid crystal display device of an embodiment of the present invention.

Fig. 5 is a circuit diagram showing the connection of a 4-bit linear digital analog converter to a buffer in the present invention.

FIG. 6 is a timing diagram showing the operation of the circuit in accordance with the fourth and fifth figures.

The seventh diagram is a schematic view showing a portable telephone device to which the liquid crystal display device of the present invention is applied.

110‧‧‧Reference voltage generator

120‧‧‧Voltage selector

131‧‧‧4-bit linear digital analog converter (DAC)

132‧‧‧4-bit linear digital analog converter (DAC)

141‧‧‧Negative feedback buffer

142‧‧‧Negative feedback buffer

SB1B‧‧‧Source Busbar

SB1G‧‧‧Source Busbar

SB1R‧‧‧ source busbar

SB2B‧‧‧ source busbar

SB2G‧‧‧Source Bus

SB2R‧‧‧ source busbar

152‧‧ ‧ multiplexer

Claims (4)

A driving device for a liquid crystal display device, wherein a liquid crystal display device is driven by supplying a tone voltage of a source bus, the driving device of the liquid crystal display device comprising: a reference voltage generator, which generates a set voltage, Setting a voltage within a range of the tone voltage; a first digital analog converter that extracts a value representing a voltage range from the reference voltage generator through a level bit of a data code, wherein the tone voltage corresponds to a liquid crystal element of the liquid crystal display device; a second and a third digital analog converter configured in two columns, wherein the second and third digital analog converters select the pixel according to the lower order bit of the data code The second and third digital analog converters may selectively output the detailed value when the first digital analog converter indicates a detailed value in the voltage range indicated by the first digital analog converter; the second and third digital analog converters include: a first switch group, which is set corresponding to the lower order bit of the data code, and switches the connection and disconnection of one of the common grounding capacitors corresponding to the data content of the lower order bit, Displaying two values of the voltage range; and a second switch group, when the switches of the first switch group are all disconnected, sending any output from the capacitor or the output of the first digital analog converter a buffer amplifier; a demultiplexer selectively connecting the outputs of the second and third digital analog converters to any one of the even column outputs; and a buffer amplifier disposed at the Second and third digits The analog converter is interposed between the demultiplexer and the demultiplexer; wherein the buffer amplifier is a negative feedback connected operational amplifier. The driving device of the liquid crystal display device of claim 1, wherein the number of columns of the even columns is 6, which corresponds to two columns of three colors. A liquid crystal display device comprising: a plurality of gate lines; a plurality of source bus bars; a liquid crystal display element array comprising a plurality of liquid crystal display elements arranged in each of the gate lines and the respective source confluences Connected to a gate of a thin film transistor on the gate lines and to the drain and source of the thin film transistor on the gate lines; a gate line driving device that drives the gate line And a driving device according to any one of claims 1 to 2, which drives the source busbars. The liquid crystal display device according to claim 3, wherein the liquid crystal display device is installed in a portable telephone device, a digital camera, a personal digital assistant (PDA), a notebook computer, a desktop computer, a television, and a car. Display or portable DVD player.