JP4028084B2 - Computer system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a liquid crystal display device and a computer system using the same, and more particularly to an active matrix liquid crystal display device such as a TFT for driving each image on a liquid crystal panel using a gradation voltage corresponding to an input signal, and a display monitor for the same. As a computer system.
[0002]
[Prior art]
In general, gradation characteristics in a TFT liquid crystal display device are determined by a γ-corrected power supply voltage (gradation correction reference voltage) input to a source driver. This gradation correction reference voltage is generated by the gradation voltage circuit in the TFT liquid crystal display device, and the source driver corresponds to the input signal using the gradation correction reference voltage generated from the gradation voltage circuit. By determining the gradation voltage and supplying the gradation voltage to the source line as a driving voltage, each image on the TFT liquid crystal panel is driven. Thereby, multi-tone display such as color is realized.
[0003]
However, since the gradation voltage circuit normally has only one gradation characteristic, the relationship between the gradation level and the gradation correction reference voltage value is always constant. For this reason, it is impossible to realize two or more gradation characteristics such as an easy-to-view gradation characteristic considering the optical characteristics unique to the TFT liquid crystal display device and the same gradation characteristic as the CRT monitor. There is a problem that the gradation of the image looks different depending on whether the image is viewed on the TFT liquid crystal display device or the CRT monitor.
[0004]
In addition, when displaying a still image or a moving image, there is a problem that it is difficult to recognize the image with human eyes because there are few gradation differences in dark portions in images with many dark gradation portions. there were.
[0005]
[Problems to be solved by the invention]
As described above, conventionally, only one predetermined gradation characteristic can be used, and the gradation characteristic cannot be changed according to the display image and application.
The present invention has been made in view of such circumstances, and provides a liquid crystal display device capable of selectively displaying a screen using a plurality of gradation characteristics and a computer system using the same. Objective.
[0006]
[Means for Solving the Problems]
In order to solve the above-described problems, the present invention provides a computer system that uses a liquid crystal display device that drives each pixel of a liquid crystal panel using a gradation voltage corresponding to an input signal as a display monitor. Select the gradation characteristic to be used from among the plurality of gradation characteristics according to the input gradation selection signal, which has a plurality of gradation characteristics in which the relationship between the gradation level and the gradation correction reference voltage value is different from each other. A gradation voltage generating means for generating a gradation correction reference voltage value based on the selected gradation characteristic is provided, and a liquid crystal is generated based on the gradation correction reference voltage value generated by the gradation voltage generation means and the input signal. A first display mode configured to drive each pixel of the panel and displaying a screen on the liquid crystal display; and an external CRT display connectable to the liquid crystal display and the computer system A display control means for controlling the screen display in any one of these display modes and switching the display mode to be used in response to a predetermined key input, and the display mode. And a means for supplying to the liquid crystal display device a gradation selection signal for switching to a gradation characteristic corresponding to the display mode to be switched to.
[0008]
Thus , the gradation characteristics are automatically switched in conjunction with the display mode switching . Thus, when displaying on the screen of the liquid crystal display device, use easy-to-see gradation characteristics considering the optical characteristics unique to the liquid crystal display device, and when performing simultaneous display of the CRT monitor and the liquid crystal display device, It is possible to perform control such as using gradation characteristics that can obtain the same gradation as when viewed on a CRT monitor.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows a configuration of a TFT liquid crystal display device according to an embodiment of the present invention. This TFT liquid crystal display device is an active matrix display device that drives and controls each image on a liquid crystal panel using a gradation voltage corresponding to an input signal. Reference numeral 11 denotes an input terminal, which includes a display controller built in an information terminal such as a personal computer and a display signal such as characters / graphics / moving pictures generated from a power supply circuit, a control signal, a power supply, and a GND. Etc. are entered.
[0010]
A voltage circuit 12 converts a voltage input from the input terminal 11 into various power supply voltages such as a circuit voltage, a driver IC voltage, a gate voltage, a counter voltage, and a liquid crystal applied voltage in the TFT liquid crystal display device.
[0011]
A gradation voltage generating circuit 13 has a plurality of gradation characteristics in which the relationship between the gradation level and the gradation correction reference voltage value is different from each other, and generates the gradation correction reference voltage value based on the selected gradation characteristic. It is. A gradation characteristic to be used is selected by a gradation selection signal, and a gradation correction reference voltage corresponding to the selected gradation characteristic is output from the gradation voltage generation circuit 13. Each gradation characteristic is set in a range of a gradation voltage width determined by the relationship between transmittance [%] and applied voltage [V] according to various conditions such as liquid crystal material and temperature.
[0012]
A timing control IC 14 receives control signals and display data, supplies display data to the source driver IC 16, and controls the source driver IC 16 and the gate driver IC 15.
[0013]
A gate driver IC 15 includes a shift register circuit, a level shift circuit, an output buffer circuit, and the like, and drives the gate of the TFT arranged for each pixel of the TFT liquid crystal panel 17.
[0014]
A source driver IC 16 includes a shift register circuit, a latch circuit, a D / A converter circuit, an output buffer circuit, and the like. By using the gradation correction reference voltage output from the gradation voltage generating circuit 13, reference numeral 16 denotes a source driver IC. Then, the gradation voltage corresponding to the display signal having the gradation sent from the timing control IC 14 for each pixel is determined, and the gradation voltage is supplied to the corresponding source line of the liquid crystal display panel 17 as a drive voltage.
[0015]
Reference numeral 17 denotes a TFT liquid crystal panel which is driven by a gate driver IC 15 and a source driver IC to perform screen display.
Reference numeral 18 denotes a switch which selects one gradation characteristic from a plurality of gradation characteristic parameters and supplies it to the gradation voltage generation circuit 13 as a gradation selection signal. In this example, the switch 18 is not built in the panel and is provided outside for easy operation. Also, here, it is assumed that one of the three gradation characteristics of the gradation voltage generation circuit 13 is selected by a 3-bit gradation selection signal, and the 3-bit gradation selection signal is used as it is. It is sent to the voltage generation circuit 13. Alternatively, a gradation selection signal may be input as one of the control signals, and the gradation characteristics used by the gradation voltage generation circuit 13 may be selectively controlled via the timing control IC 14.
[0016]
FIG. 2 shows three types of gradation characteristics that the gradation voltage generation circuit 13 has.
For example, the gradation characteristics of a CRT monitor, the gradation characteristics of a general TFT liquid crystal display device, the gradation characteristics for increasing the gradation difference in a dark part, and improving the image recognition performance, etc. 3 is defined. A plurality of different gradation characteristics are prepared in the gradation voltage generation circuit 13.
[0017]
In FIG. 2, the ratio becomes brighter as 100% and becomes darker as 0%. Considering the case where the gradation level is 64 gradations as an example, the 0th gradation is the leftmost end of the gradation, and the 63rd gradation is the rightmost end. Therefore, the gradation characteristic represents what ratio is configured from the left side to the right side (dark → bright) or from the right side to the left side (bright → dark). The plurality of gradation characteristics means that there are two or more curves having different ratios (curve shapes) such as three types in the figure. The voltage value of 100 [%] is always constant, and this corresponds to the maximum voltage width determined by the relationship between the transmittance [%] and the applied voltage [V] according to various conditions such as liquid crystal material and temperature. The maximum voltage width is the same for all gradation characteristics, and the gradation correction reference voltage value to be output for each gradation level is individually determined for each characteristic within the range of the voltage width.
[0018]
FIG. 3 shows a configuration example of the gradation voltage generation circuit 13. The gradation voltage generation circuit 13 is prepared in the number X necessary for gradation characteristics. Reference numeral 131 denotes a first gradation characteristic, and a gradation correction reference voltage value corresponding to each gradation level is generated based on the first gradation characteristic. Reference numeral 132 denotes a second gradation characteristic, and a gradation correction reference voltage value corresponding to each gradation level is generated based on the second gradation characteristic. Reference numeral 133 denotes a third gradation characteristic, and a gradation correction reference voltage value corresponding to each gradation level is generated based on the third gradation characteristic. Reference numeral 134 denotes an Xth gradation characteristic, and a gradation correction reference voltage value corresponding to each gradation level is generated based on the Xth gradation characteristic.
[0019]
A gradation selection circuit 135 selects and outputs one gradation characteristic to be used from a plurality of gradation characteristics.
FIG. 4 shows an example of the gradation characteristic selection processing operation that the gradation voltage generation circuit 13 has.
[0020]
First, in step S101, the above-described switch 18 connected to the panel generates a gradation selection signal and notifies which gradation characteristic has been selected. In step S102, a gradation characteristic to be used is selected in the gradation voltage generation circuit 13 based on the gradation selection signal, and a gradation correction reference voltage is generated according to the selected gradation characteristic. Thereafter, the gradation correction reference voltage generated by the gradation voltage generation circuit 13 is supplied to the source driver 16 in step S103.
[0021]
FIG. 5 shows an example of a specific circuit configuration of the gradation voltage generation circuit 13.
The gradation voltage generation circuit 13 includes three voltage generation circuits 51, 52, and 53 corresponding to the three gradation characteristics, respectively, and any one of the three voltage generation circuits 51, 52, and 53 is a switch. It is selected by the selection signal from 18 and operates. The voltages A, B, and C are supplied from the voltage circuit 12 of FIG. 1, and the relationship between the transmittance [%] and the applied voltage [V] depending on various conditions such as liquid crystal material and temperature depending on the value of the voltage A. The maximum gradation voltage width determined by is determined.
[0022]
The voltage generation circuit 51 corresponds to the first gradation characteristic, and when selected by the switch 18, the gate of the transistor T1 is grounded, whereby the gate of the transistor T1 becomes low level, and the gate of the transistor T2 Becomes a low level, the series circuit of the plurality of resistors R3... Ry and the transistor T2 is in an operating state, and the gradation correction reference corresponding to the resistance division value of the maximum gradation voltage width from the contact between each resistor and the transistor T2. Voltages a to x are output and input to the source driver. The source driver uses the gradation correction reference voltage in any number of divisions.
[0023]
The voltage generation circuits 52 and 53 correspond to the second and third gradation characteristics, respectively, and the resistance division ratio constituting the series circuit of the output stage is different from that of the voltage generation circuit 51. The configuration is the same as that of the voltage generation circuit 51.
[0024]
In this way, the plurality of voltage generation circuits 51, 52, 53 are configured to generate a predetermined gradation correction reference voltage value for each gradation level within the range of the same voltage width. Regardless of the gradation characteristics selected from the tonal characteristics, the effective voltage supplied to each pixel via the source line is kept constant, so that the contrast remains constant even when the gradation characteristics are switched. Is possible.
[0025]
Next, the control operation of the TFT liquid crystal display device of FIG. 1 will be described.
Here, a case where the gradation selection signal is output from an information terminal such as a personal computer using the TFT liquid crystal display device as a display monitor is illustrated. When display data, a control signal, a power supply, a GND, and a gradation selection signal are input to the input terminal 11 from a display controller and a power supply circuit built in an information terminal such as a personal computer, the voltage circuit 12 generates the display data. Various power sources and various signals generated by the timing controller 14 are output to the gate driver IC 15 and the source driver IC 16, and an image is displayed on the TFT liquid crystal panel 17 by the drive control by the gate driver IC 15 and the source driver IC 16.
[0026]
At this time, the gradation characteristic is selected by the gradation selection signal, and a gradation correction reference voltage corresponding to the selected gradation characteristic is created by the gradation voltage generation circuit 13 and output to the source driver IC 16. The A gradation voltage corresponding to the gradation level of the display data sent for each pixel from the control IC 14 is determined by the source driver IC 16 based on the gradation correction reference voltage, and this is the source line driving of the TFT liquid crystal panel 17. Used as voltage.
[0027]
As described above, a plurality of gradation characteristics are prepared in advance, and the gradation characteristics are selected by an external input such as a switch or a signal from an information terminal such as a personal computer. An image can be displayed by selecting an optimum gradation characteristic.
[0028]
FIG. 6 shows a configuration example of a personal computer having a gradation characteristic selection function.
A CPU 61 controls the operation of the entire personal computer by executing a program. A RAM 62 is used as a main memory and is used for storing application programs and various data. A BIOS-ROM 63 contains a BIOS program for controlling various hardware of the personal computer.
[0029]
Reference numeral 64 denotes a control IC comprising a gate array (GA), which serves as an interface for data transmission / reception between the BIOS and the power supply microcomputer 71. Reference numeral 65 denotes a display controller which controls display on the TFT liquid crystal display device. The display controller 65 has an LCD display mode for displaying a screen only on a TFT liquid crystal display device, a CRT display mode for displaying a screen only on an external CRT monitor connectable to a personal computer, and the same screen on the TFT liquid crystal display device and the external CRT monitor. There is a simultaneous display mode for simultaneous display, and the display mode to be used can be set / changed by key input such as a hot key or BIOS environment setting.
[0030]
A keyboard controller (KBC) 66 controls an interface for data transmission / reception between the keyboard and the BIOS. Reference numeral 67 denotes a power supply circuit unit that supplies power to the system. The power supply unit has a power supply microcomputer 71.
[0031]
Reference numeral 100 denotes the TFT liquid crystal display device described with reference to FIG. 1, which has a gradation control terminal for inputting a gradation selection signal, and is configured so that gradation characteristics change according to the inputted gradation selection signal. ing.
[0032]
Reference numeral 69 denotes a keyboard which transmits a key input from the user to the KBC 66. Reference numeral 70 denotes a C-MOS, which holds the setup state of hardware. Reference numeral 71 denotes a power supply microcomputer, which receives a gradation selection instruction via the BIOS and the control IC 64, or via the KBC 66 and the control IC 64, and generates a gradation selection signal accordingly.
[0033]
FIG. 7 shows the procedure of display mode switching processing using hot keys.
Here, the hot key is a key for directly requesting the CPU 61 to switch various operation modes for setting / changing the system environment. Assigned as that hotkey. When this hot key is operated, a BIOS display mode change processing routine is called and executed by an interrupt signal to the CPU 61. In this hot key processing, unlike normal key data transmission, an interrupt signal such as SMI is issued to the CPU 61, thereby notifying the CPU 61 that the hot key has been pressed.
[0034]
That is, as shown in FIG. 7A, when a hot key for switching the display mode prepared on the keyboard 69 is pressed, an interrupt signal is first sent to the CPU 61, and the BIOS display mode change processing routine is performed. Is called (step S201). Next, the display controller 65 is controlled by the BIOS, and a display mode changing process is performed (step S202). As shown in FIG. 7B, the display mode toggles every time the hot key for switching the display mode is pressed, and changes to the LCD display mode, the simultaneous display mode, the CRT display mode, and the LCD display mode. .
[0035]
The BIOS executes the process shown in FIG. 8 in response to an instruction for such a display mode switching process.
That is, first, a new display mode designated by the hot key is checked to determine whether it is the simultaneous display mode or the LCD display mode (steps S401 and S404). In the case of the simultaneous display mode, a gradation selection command for the simultaneous display mode for realizing the same gradation characteristics as the CRT on the TFT liquid crystal display device is transmitted to the power supply microcomputer 71 (step S402). The display controller 65 is set to the simultaneous display mode (step S403). In response to the gradation selection command, the power supply microcomputer 71 outputs a gradation selection signal for selecting gradation characteristics for the simultaneous display mode.
[0036]
On the other hand, in the LCD display mode, a gradation selection command for the LCD display mode is transmitted to the power supply microcomputer 71 in order to realize a dedicated gradation characteristic optimum for the LCD characteristics on the TFT liquid crystal display device. (Step S405) Then, the display controller 65 is set to the LCD display mode (Step S406). In response to the gradation selection command, the power supply microcomputer 71 outputs a gradation selection signal for selecting gradation characteristics for the LCD display mode.
[0037]
If the display mode is the CRT display mode, the display controller 65 is set to the CRT display mode (step S407).
As described above, by switching the gradation characteristics in conjunction with the display mode, the TFT-like gradation characteristics can be automatically set in the LCD display mode, and the CRT gradation characteristics can be changed in the simultaneous display mode. By automatically setting the TFT liquid crystal display device, the image displayed on the LCD and the image displayed on the CRT can have the same characteristics.
[0038]
【The invention's effect】
As described above, according to the present invention, a plurality of gradation characteristics are prepared in advance in the gradation voltage generation circuit of the liquid crystal display device. For example, a switch that can be operated by a user or the liquid crystal display device is used as a display monitor. A gradation characteristic to be used is selected according to a selection signal from the computer. Thereby, a screen display can be performed by selectively using a plurality of gradation characteristics, and the gradation characteristics can be switched according to the display image and application. In particular, since the gradation characteristics can be automatically switched in conjunction with the switching of the display mode of the computer, it is easy to see in consideration of the viewing angle unique to the liquid crystal display device when displaying the screen on the liquid crystal display device. When gradation characteristics are used and when a CRT monitor and a liquid crystal display device are simultaneously displayed, control is automatically performed such that gradation characteristics that can obtain the same gradation as when viewed on the CRT monitor are used. Can be performed.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of a liquid crystal display device according to an embodiment of the present invention.
FIG. 2 is a view for explaining a plurality of gradation characteristics prepared in the liquid crystal display device of the embodiment.
FIG. 3 is an exemplary view showing a basic configuration of a gradation voltage generating circuit provided in the liquid crystal display device of the embodiment.
FIG. 4 is a view showing a gradation characteristic selection operation in the liquid crystal display device of the embodiment.
FIG. 5 is a circuit diagram showing an example of a specific configuration of a gradation voltage generating circuit provided in the liquid crystal display device according to the embodiment;
FIG. 6 is an exemplary diagram showing a configuration of a personal computer using the liquid crystal display device of the embodiment as a display panel.
7 is a diagram for explaining a display mode switching operation by a hot key in the personal computer of FIG. 6;
8 is a diagram for explaining a gradation characteristic selection operation that is automatically executed in conjunction with the display mode switching operation in the personal computer of FIG. 6;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 11 ... Input terminal 12 ... Voltage circuit 13 ... Gradation voltage generation circuit 14 ... Timing control IC
15 ... Gate driver IC
16 ... Source driver IC
17 ... Liquid crystal panel 18 ... Switch

Claims (4)

In a computer system using a liquid crystal display device that drives each pixel of a liquid crystal panel using a gradation voltage corresponding to an input signal as a display monitor,
The liquid crystal display device has a plurality of gradation characteristics in which the relationship between the gradation level and the gradation correction reference voltage value is different from each other, and is used from the plurality of gradation characteristics in accordance with the inputted gradation selection signal. A gradation voltage generation unit that selects a gradation characteristic and generates a gradation correction reference voltage value based on the selected gradation characteristic, and inputs the gradation correction reference voltage value generated by the gradation voltage generation unit It is configured to drive each pixel of the liquid crystal panel based on the signal ,
A first display mode for displaying a screen on the liquid crystal display device; and a second display mode for simultaneously displaying a screen on the liquid crystal display device and an external CRT display connectable to the computer system. Display control means for controlling the screen display and switching the display mode to be used according to a predetermined key input ;
A computer system comprising: means for supplying to the liquid crystal display device a gradation selection signal for switching to a gradation characteristic corresponding to a display mode to be switched in response to switching of the display mode . The gradation voltage generating means includes
A plurality of gradation voltage generation circuits provided corresponding to each of the plurality of gradation characteristics, each configured to generate a plurality of gradation correction reference voltages according to the corresponding gradation characteristics;
Means for selecting a gradation voltage generating circuit corresponding to the gradation characteristic selected from the plurality of gradation characteristics;
The computer system of claim 1, wherein the gradation correction reference voltage value outputted from the selected gradation voltage generating circuit is configured to be supplied to said drive means. The plurality of gradation voltage generation circuits are configured to generate a gradation correction reference voltage value determined in advance for each gradation level within the same voltage range, and the plurality of gradation characteristics. 3. The computer system according to claim 2, wherein the effective voltage for driving each pixel is kept constant regardless of which gradation characteristic is used . The gradation voltage generating means has a first gradation characteristic corresponding to the first display mode, and generates a plurality of gradation correction reference voltages with the first gradation characteristic. And a second voltage generation circuit having a second gradation characteristic corresponding to the second display mode and generating a plurality of gradation correction reference voltages with the second gradation characteristic, 2. The computer system according to claim 1, wherein one of the first voltage generation circuit and the second voltage generation circuit is selected in response to a tone selection signal.

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