JP3180858B2 - Liquid crystal display - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device characterized in that control data of a driving voltage for driving a liquid crystal display is controlled in accordance with a change in temperature of the liquid crystal display so as to appropriately obtain the luminance of the liquid crystal display. .

[0002]

2. Description of the Related Art FIG. 3 is a block diagram showing the configuration of a conventional liquid crystal display device. In the figure, 1 is a lookup table, 2
In the liquid crystal driving voltage generating circuit for outputting a driving voltage V to the source driver 4 for driving the liquid crystal display 3, and outputs a driving voltage V on the basis of the control data D _i lookup tables 1.

[0003] Reference numeral 5 denotes a temperature sensor for measuring the temperature of the liquid crystal display 3, and 6 denotes a read-only memory (hereinafter referred to as R).
OM), correction data groups # 1 data, # 2 data,... Of the drive voltage V are stored in different temperature ranges.
For example, the # 1 data includes a group of control data D _0i (i = 1 to n) of the driving voltage V in the temperature range from T ₀ to T ₁ , and the # 2 data includes the driving data in the temperature range from T ₁ to T _2. It consists of control data D _1i group (i = 1 to n) of voltage V.

Correction data group # stored in ROM 6
1 data, # 2 data,...
The data is collectively downloaded to the lookup table 1 based on the address specified by U7. Then, the downloaded corrected data set # 1 data, # 2 data, ..., the address is specified by the display data S _1, is output to the liquid crystal driving voltage generation circuit 2 as control data D _i. The liquid crystal drive voltage generating circuit 2 is configured to
And it outputs a driving voltage V to the source driver 4 based on the control data D _i input from the table 1.

[0005] 8 _1, 8 _2, ... 8 ₄ is a three-state buffer for switching the bus under the control of the CPU 7. Three-state buffers _81, 82, the correction data set # 1 data stored in the ROM 6, # 2 data, ...
Is turned on when the data is downloaded to the lookup table 1, and the three-state buffers 8 ₃ and 8 ₄ are turned on.
Is turned on when the correction data group # 1 data, # 2 data,... Downloaded to the lookup table 1 are read out by the liquid crystal drive voltage generation circuit 2.

[0006]

In such a conventional liquid crystal display device, it is necessary to download all correction data groups stored in the ROM to a look-up table when the device is started. It has the disadvantage of requiring a lookup table with a correspondingly large capacity, and has the disadvantage that the time for downloading is long and the startup time is long. Further, the switching between the writing of the lookup table and the reading from the lookup table needs to be performed using a three-state buffer, which complicates the circuit.

The present invention has been made in view of the above points, and uses a memory having at least two input ports and a bank in a look-up table, and controls the control data every time the temperature of the liquid crystal display changes. The required correction data group is downloaded to the bank that does not output the correction data. Then, control data is read out from the downloaded correction data group to the liquid crystal drive voltage generation circuit based on designation of display data,
With a three-state buffer or the like, there is no need to switch between writing and reading, a look-up table can be configured with a small-capacity memory, and a display device that can reduce startup time can be provided.

[0008]

In order to achieve the above object, the present invention changes the control data of the driving voltage for driving the liquid crystal display in accordance with the temperature of the liquid crystal display so that the brightness of the liquid crystal display can be adjusted properly. A liquid crystal display device having a ROM in which a correction data group of the drive voltage corresponding to a temperature change of the liquid crystal display is stored for each different temperature range, and at least two input ports and a bank. The control data from the correction data group downloaded from the ROM is read out, and the correction data group corresponding to the temperature change is stored in the bank on the side not outputting the control data in accordance with the temperature change. Lookup that is downloaded
And a table.

[0009]

In the lookup table, a correction data group corresponding to the changed temperature is downloaded from the ROM every time there is a temperature change to the bank on which the control data is not output. In the lookup table, after the correction data group is downloaded, the bank is switched, and control data is read out from the downloaded correction data group to the liquid crystal drive voltage generation circuit based on the address specified by the display data.

[0010]

An embodiment of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a configuration block diagram showing one embodiment of the liquid crystal display device of the present invention. In the figure, components having the same functions as those in FIG. 3 are described with the same reference numerals.

Reference numeral 10 denotes a look-up table, which is a dual-port R having two input ports and two banks.
AM is used. Look-up table 10, the liquid crystal display 3 in the correction data set # 1 data stored in when there is a temperature change ROM 6, # 2 data, ... on the side of the bank does not output the control data D _i from the The necessary correction data group is downloaded. For example, based on the specified display data S _1, the control from the bank 0 data D _i
Is output to the liquid crystal drive voltage generating circuit 2 and if there is a temperature change in the liquid crystal display 3, the look-up
In the table 10, a correction data group corresponding to a temperature change, for example, # 1 data from among the correction data groups # 1 data, # 2 data,... Stored in the ROM 6, is downloaded to the bank 1.

When the correction data group # 1 data corresponding to the temperature change is downloaded to the bank 1, a look-up
Table 10, the bank is switched, based on the specified address of the display data S ₁ inputted from the port 1, the control data D _i the liquid crystal driving voltage generating from the corrected data set # 1 data downloaded to the bank 1 Circuit 2
Output to Thus, look-up table 10
Indicates that the temperature correction data group # 1 data is stored in the bank on the side that is not outputting control data every time the temperature changes.
After the # 2 data is downloaded, the bank is switched, and the downloaded correction data group is read out to the liquid crystal drive voltage generation circuit 2.

2A and 2B are time charts for explaining the operation of the liquid crystal display device of the present invention. FIG. 2A shows the time on the horizontal axis, the temperature change on the liquid crystal display on the vertical axis, and FIG.
(C) shows the contents of bank 1 and (D) shows the bank of correction data to be output to the liquid crystal drive voltage generation circuit. Incidentally, from T ₀ to T ₁ # 1 data range, from T ₁ T ₂
The # 2 data range, T ₃ from T ₂ are # 3 data range, T ₃
From T ₄ is # 4 data range, the correction data group set in each temperature, to avoid losing linearity to the brightness of the liquid crystal display 3 based on the voltage output from the liquid crystal driving voltage generating circuit 2 The voltage is corrected.

(1) At time t ₀ , that is, when the temperature of the liquid crystal display is in the range of T ₂ to T ₃ , data # 3 from bank 0 is output to the liquid crystal drive voltage generating circuit 2 in accordance with the address specified by the display data S _1. Is done. (2) at time t ₁ the temperature of the liquid crystal display when raised to T _3, # 4 data bank 1 from ROM6 is downloaded. (3) If the bank 1 # 4 data is downloaded, the lookup table 10 is switched from the bank 0 by the bank switching status signal S ₂ input from the CPU11 to the bank 1, specifies display data S ₁ The control data D is supplied to the liquid crystal drive voltage generation circuit 2 according to the address.
Output _i . (4) Thereafter, the bank is switched at times t ₂ , t ₃ , and t ₄ ,
Data # 3, 2, and 1 corresponding to the temperature at that time are output to the liquid crystal drive voltage generation circuit 2.

[0015]

As described above in detail, the liquid crystal display device of the present invention downloads the necessary correction data group to the bank on which the control data is not output every time the temperature of the liquid crystal display changes. The control data is read out from the downloaded correction data group to the liquid crystal drive voltage generation circuit based on the designation of the display data. Therefore, the look-up table can be configured with a small-capacity memory, the start-up time can be reduced, and there is no need to particularly provide a three-state buffer for switching between writing and reading.

[Brief description of the drawings]

FIG. 1 is a configuration block diagram showing one embodiment of a liquid crystal display device of the present invention.

FIG. 2 is a time chart illustrating an operation of the liquid crystal display device of the present invention.

FIG. 3 is a configuration block diagram of a conventional liquid crystal display device.

[Explanation of symbols]

 2 Liquid crystal drive voltage generation circuit 3 Liquid crystal display 10 Look-up table 11 CPU

Claims (1)

(57) [Claims] Control data according to claim 1] driving voltage for driving the liquid crystal display vary depending on the temperature of the liquid crystal display, the liquid crystal display device LCD brightness is controlled to be a proper, the temperature change of the liquid crystal display According to the driving voltage
RO data in which the correction data groups are stored for different temperature ranges
And M, have at least two input ports and banks, before
From the correction data group downloaded from the ROM
Control data is read and the control data is output
The ROM on the other side is stored in the ROM according to temperature changes.
The correction data group corresponding to the temperature change is downloaded from
A liquid crystal display device comprising: a lookup table;