JP4157566B2 - Reference voltage source circuit for gamma correction and liquid crystal display device - Google Patents

Description

The present invention relates to a gamma correction reference voltage source circuit that generates a reference voltage for gamma correction of gradation display characteristics, and a liquid crystal display device using the gamma correction reference voltage source circuit .

  FIG. 7 shows a configuration diagram of a conventional liquid crystal display device. In the figure, reference numeral 100 denotes an LCD panel, which includes a source line 210 constituting a data line and a gate line 310 constituting a scanning line, adding a data signal from the source driver 200 to the source line 210 and receiving a scanning signal from the gate driver 300. In addition to the gate line 310, display is performed. Reference numeral 400 denotes a display control interface that separates a video signal supplied from the outside via an input signal line 410 into a digitized video signal 420, a source driver control signal 430, and a gate driver control signal 440 necessary for display on the LCD panel 100. Reference numeral 500 denotes a reference voltage source for multi-gradation display.

Next, the operation will be described.
The digitized video signal 420 is taken into the register A 230 separately for each pixel under the control of the shift register 220, and is converted into an analog signal by the D / A converter 250 via the register B 240. This analog signal voltage is converted into a voltage (reference voltage) having a voltage value after gamma correction corresponding to the analog signal voltage by controlling an analog switch of the selector 260. The voltage after the gamma correction is applied to the source of the liquid crystal element of the display pixel of the LCD panel 1. The conversion to the voltage having the voltage value after the gamma correction is performed as follows. A reference voltage power source 500 is provided that generates a plurality of voltages (reference voltages) having a voltage value obtained by multiplying the voltage value of the analog signal voltage by a gamma correction coefficient corresponding to the voltage value in the range that the analog signal voltage can take. Has been. Then, by controlling the analog signal voltage, the analog signal voltage is switched to a reference voltage from a reference voltage source having the gamma correction value having a magnitude corresponding to the voltage value of the analog signal.

  The reference voltage power supply 500 is constituted by a voltage dividing circuit 520 that divides the voltage from the stabilized power supply 510 by resistors (R1 to R10) and outputs the divided voltage via an emitter follower (EF1 to EF0). Voltage is sent out. Each resistance value of the voltage dividing circuit is preset and incorporated in correspondence with a specific gamma correction coefficient.

  Since the conventional device has the above configuration, in order to change the gamma correction coefficient, it is necessary to change the combination of each resistor of the voltage dividing circuit. could not. However, as the image quality of display devices has improved and the opportunity to handle color-type screens has increased, the demand to be able to set gamma correction suitable for each type has become stronger. It was no longer possible to use a fixed type.

The present invention has been made to solve the above-described problems, and a gamma correction reference voltage source circuit that can easily switch to a plurality of types of gamma correction coefficients, and the gamma correction reference. An object of the present invention is to provide a liquid crystal display device using a voltage source circuit .

A reference voltage source circuit for gamma correction according to the present invention is a reference voltage source circuit that generates a plurality of reference voltages related to gamma correction of a signal line driver unit that drives a signal line of a liquid crystal panel , and a plurality of reference voltages. Corresponding to each of the plurality of reference voltages read from the first storage unit and the first storage unit that stores the plurality of storage data, the storage data related to the reference voltage is temporarily stored. A plurality of rewritable second storage units that are stored in memory, and a plurality of stored data related to the reference voltages stored in the second storage unit corresponding to the plurality of reference voltages, A plurality of reference voltage generation circuits to be generated and a rewrite circuit for reading stored data from the outside to the second storage unit through a rewrite control terminal, and the storage data stored in the first storage unit is read Being second The first reference voltage data is temporarily stored in the memory unit and output to the signal line driver unit as the first reference voltage for gamma correction via the reference voltage generation circuit. When changing the gamma correction, a new reference The stored data relating to the voltage is read into the second storage unit as the second reference voltage data through the rewriting circuit, and a plurality of reference voltages relating to gamma correction are generated by the reference voltage generating circuit based on the second reference voltage data It is made to be done.
The liquid crystal display device according to the present invention comprises a liquid crystal panel, a signal line driver section for driving a signal line of the liquid crystal panel, and the above-described gamma correction reference voltage source circuit, and the rewrite circuit is connected to the rewrite control terminal. After that, the data stored in the second storage unit is temporarily rewritten with the reference voltage, and the gamma correction is performed based on the storage data different from the storage data related to the reference voltage stored in the first storage unit. It is what I did.

A reference voltage source circuit for gamma correction according to the present invention stores a plurality of data relating to correction of gradation display characteristics in a first storage unit, calls it, and temporarily stores it in a second storage unit for gamma correction. This is realized because the first reference voltage data and the storage data related to the new reference voltage are stored in the second storage unit from the rewrite circuit through the rewrite control terminal and used as the second reference voltage data related to gamma correction. There are no restrictions on the types of gamma correction that can be performed, and fine gamma correction is possible.

Embodiment 1
FIG. 1 shows a configuration diagram of a liquid crystal display device according to Embodiment 1 of the present invention. In FIG. 1, reference numeral 1 denotes an LCD panel which includes a source line 21 and a gate line 31. A data signal is applied from the source driver 2 to the source line 21, and a scanning signal is applied from the gate driver 3 to the gate line for display. Reference numeral 4 denotes a display control interface that divides an external video signal into signals necessary for display on the LCD panel 1. Reference numeral 5 denotes a reference voltage power source for multi-gradation display.

  Next, the operation will be described. The video signals digitized and arranged in series for each pixel in time are taken into each register of the register group A23 as a signal for each pixel under the control of the shift register 22, and then transferred to the register group B24. The output signal of each register of the register group B24 is converted by the D / A converter group 25 into an analog signal having a size corresponding to the luminance of each pixel. This analog signal is replaced by a selector group 26 with the analog signal after D / A conversion replaced with the corresponding gamma-corrected reference voltage and applied to the source of the liquid crystal element of each pixel of the display screen of the LCD panel 1. When the gate voltage of the liquid crystal element is applied from the gate driver 3, the liquid crystal element displays a brightness corresponding to the voltage applied through the selector group 26.

The relationship between the analog voltage of the D / A converter and the corresponding reference voltage deviates from the straight line according to the gamma correction coefficient. Specifically, the relationship shown in FIG. 3 is set for the graphic mode, FIG. 4 is set for the natural image mode, and the relationship shown in FIG. In these figures, the horizontal axis represents input data, and the vertical axis represents the corresponding output voltage. This voltage corresponds to a reference voltage (V1,... V10...) Supplied from the reference voltage power source 5. Because of the above configuration, in order to perform display with changing gamma correction corresponding to each mode for each display, the reference voltage power supply 5 corresponds to each voltage value in the range that the analog signal can take. The reference voltage required for each mode must be able to be generated with a simple operation. In the liquid crystal display device according to the present invention, the reference voltage power source 5 that generates a reference voltage that can meet such a demand is configured as follows.

  FIG. 2 is a diagram for explaining the details of the reference voltage power supply 5. In FIG. 2, 51 is a mode selection terminal, 52 is an address conversion circuit for each mode, 53 is an address designating unit, 54 is a standard for correcting gradation display characteristics for each mode such as graphic mode, natural image mode, and TV image mode. Memory (ROM) 55 for storing voltage data of voltage (for example, voltage data of mode a: V1a, V2a,... V10a,...) Is provided corresponding to each reference voltage. A rewritable memory group (RAM), 56 is a D / A converter group provided corresponding to each reference voltage, 57 is a reference voltage line for deriving each reference voltage to the selector group 26, 58 is a RAM rewriting circuit, 59 is a rewrite control terminal.

  Next, the operation will be described. When a mode designation signal is applied to the mode designation terminal 51, the mode designation signal is converted into an address signal by the mode-specific address conversion unit 52, led to the memory 54 through the address designation unit 53, and stored in the memory 54. The address of the voltage data of the reference voltage for the gamma correction in the designated mode is designated and read out. The read voltage data of the reference voltage is temporarily stored in the rewritable memory group 55. This voltage data is a set of data corresponding to each reference voltage stored in the form of digital data. This set of digital data corresponds to the reference voltages V1, V2,... V10... Of the specified mode, and analog voltages are obtained by each D / A converter of the prepared D / A converter group 56. And supplied to the selector group 26 through the reference voltage line 57. As described above, if voltage data corresponding to the reference voltage for each mode is stored in the memory 54, the voltage data can be designated and called to generate the corresponding reference voltage. A screen display with a gamma correction coefficient applied can be performed.

In the above, the case where the data related to one set of gamma correction coefficients is read and the gamma correction is performed has been described. However, the data related to two sets of gamma correction coefficients are read at a time, and the average value or weighting of these two data is read. An average value can be calculated and used to perform gamma correction. As a result, it is possible to meet the demand for applying an intermediate correction between the two modes. In addition, since the data stored in the rewritable memory 55 can be read from the rewrite control terminal 59 via the RAM rewrite circuit 58, the data temporarily read into the memory 55 can be read in addition to the data prepared in the memory 54 in advance. You can also use a new mode to perform gamma correction.

1 is an overall configuration diagram according to Embodiment 1 of the present invention. It is a detailed block diagram of the reference voltage power supply part which concerns on Embodiment 1 of this invention. It is explanatory drawing regarding the gamma correction of a graphic mode. It is explanatory drawing regarding the gamma correction of a natural image mode. It is explanatory drawing regarding the gamma correction of TV image mode. It is the data which shows the input / output voltage relationship of various modes regarding a gamma correction coefficient. It is a block diagram of the conventional liquid crystal display device.

Explanation of symbols

1: LCD panel,
2: source driver, 21: source line group, 22: shift register,
23: Register group A, 24: Register group B, 25: D / A converter group,
26: selector group,
3: gate driver, 31: gate line group,
4: Display control interface, 41: Input signal line, 42: Video signal line,
43 Source driver control line, 44 Gate driver control line,
5: Reference voltage power supply 51: Mode selection terminal
52: Address conversion unit by mode, 53: Address specifying unit,
54: Memory, 55: Rewritable memory group,
56: D / A converter group, 57: Reference voltage line, 58: RAM rewriting circuit,
59: Rewrite control terminal.

Claims (3)

A reference voltage source circuit that generates a plurality of reference voltages related to gamma correction of a signal line driver unit that drives a signal line of a liquid crystal panel ,
A first read-only storage unit that stores a plurality of stored data related to a plurality of reference voltages;
A plurality of rewritable second storage units that temporarily store a plurality of storage data related to the reference voltage corresponding to each of the plurality of reference voltages read from the first storage unit;
A plurality of reference voltage generation circuits for inputting a plurality of stored data relating to a reference voltage stored in the second storage unit corresponding to the plurality of reference voltages, and generating the plurality of reference voltages;
A rewriting circuit for reading stored data from the outside to the second storage unit through a rewrite control terminal;
The stored data stored in the first storage unit is read out and temporarily stored as first reference voltage data in the second storage unit, and a first gamma correction related to gamma correction is performed via the reference voltage generation circuit. Is output to the signal line driver unit as one reference voltage,
When changing the gamma correction, stored data related to a new reference voltage is read into the second storage unit as second reference voltage data through the rewrite circuit, and a plurality of reference voltages related to the gamma correction are: A reference voltage source circuit for gamma correction generated by the reference voltage generation circuit based on the second reference voltage data. 2. The reference voltage source circuit for gamma correction according to claim 1, wherein the reference voltage generation circuit is a D / A converter . A liquid crystal panel, a signal line driver unit that drives a signal line of the liquid crystal panel, and a gamma correction reference voltage source circuit according to claim 1 or 2,
From the rewrite control terminal via the rewrite circuit, the data stored in the second storage unit is temporarily rewritten, and the stored data related to the reference voltage is stored in the first storage unit. Is a liquid crystal display device that performs gamma correction based on different stored data .

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