JPH11316364A - Automatic light controlling device in lcd display - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control luminance of LCD along a curve arbitrarily set for an LCD luminance variation curve by a user. SOLUTION: Backlight luminance (LCD luminance) is controlled by linearly approximating a luminance variation curve showing a relation between an ambient temperature and LCD luminance, discretely setting a start point of the approximate curve, one or more intermediate cross-over points, storing them in a memory (E<2> PROM) 3, determining a luminance variation curve linearly approximating the LCD luminance in accordance with the ambient temperatures, and controlling a driving voltage of CFL2 so that the curve becomes the LCD luminance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic light control device, and more particularly, to an automatic light control device for controlling the brightness of an LCD display device based on ambient illuminance.

[0002]

2. Description of the Related Art There is known an automatic light control device which changes a backlight luminance (LCD luminance) of a liquid crystal display to a predetermined value in accordance with ambient illuminance. In such an automatic light control device, the most suitable LCD luminance is determined in advance for a certain ambient illuminance, and the PW is adjusted so that the LCD luminance is at the ambient illuminance.
The M value is determined in real time, and based on the PWM value, a CFL (Cathode Fluoresc) constituting a backlight generation unit is determined.
PWM control of the drive waveform (or power) of the ent Lamp).

[0003]

The conventional automatic light control device controls the LCD luminance with respect to the ambient illuminance along a straight line shown in FIG. That is, in the conventional automatic light control device, the brightness change curve of the automatic light control is a straight line determined by the min-max value of the brightness, and the brightness can be controlled only along the straight line. For this reason, the user
However, there is a problem that the LCD brightness value in the middle cannot be set arbitrarily, the minimum value min in the brightness change curve cannot be changed, and there is no flexibility in brightness control. In view of the above, it is an object of the present invention to provide an automatic light control device in an LCD display device in which a user can arbitrarily set a change curve of LCD brightness and control the brightness of the LCD along the curve. Another object of the present invention is that even when a luminance change curve is arbitrarily set, a change time from the minimum luminance specified by the curve to the maximum luminance can be set as the set time, and Automatic dimming in an LCD display device that controls the brightness gradually at a low brightness level where the change is easily perceived, and controls the brightness in a short time at a high brightness that is insensitive to the brightness change so that the user does not recognize a sudden brightness change. It is to provide a device.

[0004]

According to the present invention, there is provided an automatic light control device for controlling the brightness of an LCD display device based on the ambient illuminance. A memory for storing, a setting unit for setting a starting point, one or more intermediate break points, and an ending point of the curve to approximate the brightness change curve in a straight line, and storing the result in the memory; This is achieved by an automatic dimming device including a brightness control unit that obtains the LCD brightness from the approximate brightness change curve and controls the brightness of the backlight.

It is another object of the present invention to provide a liquid crystal display (LCD)
A backlight generator for generating a backlight of the display device is provided, and a voltage applied to the backlight generator is PWM.
This is achieved by controlling the LCD luminance by controlling the luminance change curve and specifying the luminance change curve by discrete values of the ambient illuminance and the PWM value. Also, according to the present invention, the above object is achieved by changing the time required to change from the minimum LCD luminance to the maximum LCD luminance, and changing the minimum LCD luminance of each broken line from the maximum LCD luminance
The time required to change to the brightness is set, and the brightness control unit is achieved by the automatic light control device that controls the LCD brightness along the brightness change curve and according to the set time when the ambient illuminance changes.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (a) First Embodiment FIG. 1 is a configuration diagram of an automatic light control device according to a first embodiment of the present invention. In the figure, 1 is an LCD screen composed of an LCD (liquid crystal), and 2 is a C that generates a backlight of a liquid crystal display device
The backlight luminance (LCD luminance) can be controlled by controlling the pulse width (CFL driving voltage) of the CFL driving waveform by PWM control with an FL (Cathode Fluorescent Lamp). Reference numeral 3 denotes a non-volatile memory which stores a luminance change curve indicating a relationship between ambient illuminance and LCD luminance, and is, for example, an E ² PROM. FIG. 2 is an example of a luminance change curve,
The solid line 51 is a luminance change curve set in the present invention, the broken line 52 is a conventional linear luminance change curve, the horizontal axis is the ambient illuminance A (LUX), and the vertical axis is the pulse width of the CFL drive waveform according to the LCD luminance. , That is, PW that determines the CFL drive voltage
M value. The luminance change curve 51 has a starting point (Amin, P ₁ ),
It is specified by one or more intermediate break points (A ₁ , P ₁ ), (A ₂ , P ₂ ), and the end point (Amax, Pmax).

[0007] 4 the discrete points for specifying the brightness change curve 51, i.e., the start point (Amin, P _{1), 1} or more intermediate bending point _{(A 1, P 1),} (A 2, P 2 ), End point (A
max, Pmax), 5 is a photo sensor for detecting ambient illuminance, 6 is an AD converter for AD converting the photo sensor output, and 7 is a microcomputer. The microcomputer 7 converts the input luminance change curve 51 into the E ² PROM 3. A brightness change curve 5 that stores and linearly approximates a PWM value according to the current ambient illuminance.
1 and output. For example PWM value Pa of the surrounding illumination intensity Aa by = equation _{Pa (Aa-A 1) ·} (P 2 -P 1) / (A 2 -A 1) + P 1 (1), can be calculated.

[0008] 8 is a PWM value of duty 0-100
(%), 9 is a switch that turns on / off based on duty, 10 is a vehicle battery power supply,
Reference numeral 11 denotes a DC-DC converter that converts a battery voltage that changes according to the engine speed into a constant DC voltage, and 12 denotes a DC-AC that generates a square wave signal (AC voltage) having the duty by chopping the DC voltage by the switch 9. A converter (so-called inverter) 13 boosts the AC voltage output from the DC-AC converter to about several hundred volts, and
This is a transformer for driving. FIG. 3 is a flowchart of the overall control of the first embodiment. The luminance change curve 51 (FIG. 2) desired by the user is linearly approximated and stored in the E ² PROM 3 from the operation unit 4 via the microcomputer 7 (step 101).
In this state, the microcomputer 7 takes in the ambient illuminance Aa detected by the photo sensor 5 (step 102).
The PWM value Pa corresponding to the ambient illuminance is calculated by the equation (1) (step 103), and a driving voltage waveform (or power) having a pulse width corresponding to the calculated PWM value Pa is applied to the CFL2 to turn on the backlight. Then, an LCD display is performed at the luminance desired by the user (step 104). According to the first embodiment, by setting the E ² PROM PWM values for intermediate each surrounding illuminance of the min value or min-max of LCD automatic dimming (LCD brightness) as a data value, the automatic light intensity The curve can be changed arbitrarily.

(B) Second Embodiment (b-1) Configuration In the first embodiment, the user can arbitrarily set a luminance change curve,
The LCD brightness is controlled according to the curve. Second
In the embodiment, in addition to the above, the time required to change from the minimum LCD luminance to the maximum LCD luminance and the time required to change from the minimum LCD luminance to the maximum LCD luminance in each broken line portion are set, and the luminance control section is set. Controls the LCD brightness along a set brightness change curve and according to a set time when the ambient illuminance changes.

FIG. 4 is a block diagram of a second embodiment of the present invention, and the same parts as those of the first embodiment are denoted by the same reference numerals.
The configuration for controlling the LCD luminance based on the PWM value is the same as the configuration of the first embodiment and is omitted. In FIG. 4, 3 is an E ² PROM, 4 is an operation unit, 5 is a photo sensor, 6 is an AD converter, 7 'is a control unit of a microcomputer configuration, 7a is a PWM counter for outputting a PWM value, 7
b is a PWM value determination unit that determines a PWM value according to the ambient illuminance, 7c is a match detection unit that determines whether the current PWM value matches the target PWM value, and 7d is a PWM counter 7a that counts up / down the pulse. Is a frequency determination unit that determines the frequency f according to the luminance change speed, and 7f is a frequency variable unit that generates a pulse of the frequency f.

(B-2) Brightness control along the brightness change curve 52 The brightness change curve 52 shown in FIG. 5A is initially set in the E ² PROM 3 and the starting point (Amin, Pmin) of the straight line is set. ,
The end point (Amax, Pmax) and the time T required to change from the minimum luminance to the maximum luminance are set and stored. The time T required to change from the minimum luminance to the maximum luminance is constant even if the luminance change curve is changed. In active state luminance change curve 52, the count value (PWM value) of the PWM counter 7a when the ambient illuminance is Aa ₁ is equal to Pa _1,
LCD display is performed at a luminance corresponding to the PWM value Pa _1. In this state, the ambient illuminance is changes from Aa ₁ to Aa _2, PWM value determination section 7a obtains a PWM value Pa ₂ of the target than the luminance change curve 52, is inputted to the coincidence detection section 7c. As a result, the two values input to the coincidence detecting unit become inconsistent, so that the coincidence detecting unit 7c generates a count enable signal. The count enable control unit 7d determines the change direction of the ambient illuminance based on the generation of the enable signal, and instructs the PWM counter 7a to count up the pulses.

In parallel with the above, the frequency control unit 7e determines the frequency based on the set luminance change curve 52 by the following equation f = (Pmax-Pmin) / T (2), and the frequency variable unit 7f Frequency f
Is generated and input to the PWM counter 7a via the count enable control unit 7d. Therefore, when the ambient illuminance changes from Aa ₁ to Aa ₂ , the PWM counter 7 a
The pulse having the frequency of equation (2) is counted up, and when the counted value reaches Pa ₂ , the coincidence detecting unit 7c outputs a count stop signal, whereby the count enable control unit 7d starts counting up the pulse by the PWM counter 7a. Stop. As a result, the changed ambient illuminance in Aa ₂ from Aa _1,
The luminance gradually changes along the straight line 52 over a time T ′ represented by the following equation: T ′ = (Pa ₂ −Pa ₁ ) T / (Pmax−Pmin) and becomes a luminance corresponding to the ambient illuminance Aa ₂ .

(B-3) Luminance control along luminance change curve 51 The starting point (A) of the luminance change curve 51 in FIG.
min, P ₁ ), intermediate break points (A ₁ , P ₁ ), (A ₂ ,
P ₂ ), the end points (Amax, Pmax) and each of the broken lines 51a, 51
1b to the maximum luminance (P ₁ → P ₂ , P ₂ → Pma
The times T ₁ and T ₂ (= T−T ₁ ) required to change to x) are input and stored in the E ² PROM 3. As a result, the luminance change curve changes from the dotted line 52 to the solid line 51. Brightness control along curve 51a When the luminance change curve 51 is set and the ambient illuminance is A
b ₁ When (FIG. 5 (b)) of the count value (PWM value) of the PWM counter 7a is equal to Pb _1, LCD display is performed at a luminance corresponding to the PWM value Pb _1. When ambient illumination this time is changed from Ab ₁ to Ab _2, PWM value determination unit 7b obtains a PWM value Pb ₂ of the target than the luminance change curve 51, is inputted to the coincidence detection section 7c. As a result, the two values input to the match detection unit become inconsistent, so that the match detection unit 7c
Generates a count enable signal. The count enable control unit 7d determines the change direction of the ambient illuminance by generating the enable signal, and instructs the PWM counter 7a to count up the pulses.

In parallel with the above, the frequency control section 7e calculates the following equation f ₁ = (P ₂ −P ₁ ) / T ₁ (3) based on the set luminance change curve 51 and the ambient illuminance Ab ₁ , Ab _2. The frequency variable unit 7f determines the frequency f
A pulse of ₁ is generated and input to the PWM counter 7a via the count enable control section 7d. Therefore, when the ambient illuminance changes from Ab ₁ to Ab ₂ , the PWM counter 7 a
(3) counts up the pulses having a frequency of expression, a match detecting unit 7c count is Pb ₂ outputs a count stop signal, thereby counting enable control unit 7d is a pulse count up by PWM counter 7a Stop. As a result, the changed ambient illuminance in Ab ₂ from Ab _1,
The luminance gradually changes along the straight line 51a over a time T ″ represented by the following equation T ″ = (Pb ₂ −Pb ₁ ) T ₁ / (P ₂ −P ₁ ), and the luminance according to the ambient illuminance Ab ₂ become. Similarly, luminance control along the curve 51b can be performed.

Brightness control along curves 51a and 51b When the brightness change curve 51 is set and the ambient illuminance is A
In the case of b ₁ (FIG. 5B), when the ambient illuminance changes from Ab ₁ to Ab ₃ , the PWM value determination unit 7b outputs the target PWM value P _{2 on the} curve 51a and the target PWM value Pb on the curve 51b.
₃ respectively, and first, the target PW in the curve 51a
The M value P ₂ is input to the coincidence detection section 7c. As a result, the two values input to the coincidence detecting unit become inconsistent, so that the coincidence detecting unit 7c generates a count enable signal. The count enable control unit 7d determines the change direction of the ambient illuminance based on the generation of the enable signal, and instructs the PWM counter 7a to count up the pulses. In parallel with the above, the frequency control unit 7e determines the frequency f ₁ by the equation (3) based on the curve 51a, and the frequency variable unit 7f generates a pulse of the frequency f ₁ and sends it to the count enable control unit 7d. PW
Input to the M counter 7a. Therefore, when the ambient illuminance changes from Ab ₁ to Ab _3, PWM counter 7a counts up the pulses having a frequency of (3), count value P ₂
, The coincidence detecting section 7c outputs a count stop signal,
As a result, the count enable control section 7d stops counting up pulses by the PWM counter 7a.

Next, the PWM value determining section 7b calculates the curve 51b
The target PWM value Pb ₃ inputs the coincidence detection unit 7c in. As a result, the two values input to the coincidence detecting unit become inconsistent, so that the coincidence detecting unit 7c generates a count enable signal. The count enable control unit 7d determines the change direction of the ambient illuminance based on the generation of the enable signal, and
It instructs the counter 7a to count up the pulses. Or in parallel with the frequency control unit 7e determines the frequency f ₂ by = equation _{f 2 (Pmax-P 2)} / T 2 (4) on the basis of the curve 51b, the frequency controller 7f is of the frequency f ₂ Generates pulse and count enable control unit 7
Input to the PWM counter 7a via d. Therefore, P
WM counter 7a counts up the pulses having a frequency of (4), the coincidence detection section 7c and the count value becomes Pb ₃
Outputs a count stop signal, whereby the count enable control unit 7d stops counting up pulses by the PWM counter 7a.

[0017] Thus, increasing the time T _1, by reducing the time T _2, the gradual brightness along the curve 51a changes from Pb ₁ to P _2, and thereafter, rapidly brightness along the curve 51b the can vary from P ₂ to Pb _3. As described above, according to the second embodiment, the minimum value of the luminance level, the luminance change curve, and the time constant of the luminance change curve portion can be freely changed. Properties can be obtained.
As described above, the present invention has been described with reference to the embodiments. However, the present invention can be variously modified in accordance with the gist of the present invention described in the claims, and the present invention does not exclude these.

[0018]

According to the present invention, the ambient illuminance and the LCD
A luminance change curve indicating the relationship of luminance is linearly approximated, and the start point, one or more intermediate break points, and the end point of the approximate curve are discretely set and stored in a memory, and the LCD luminance according to the ambient illuminance is linearly approximated. Since the brightness is controlled from the obtained brightness change curve and the brightness is controlled so as to be the LCD brightness, an arbitrary brightness change curve desired by the user can be set and the brightness control can be performed along the curve.

According to the present invention, a backlight generator for generating a backlight of an LCD display device is provided, and a pulse width of a voltage waveform (or power) applied to the backlight generator is controlled by PWM to control the LCD. Since the luminance is controlled and the luminance change curve is specified by the discrete values of the ambient illuminance and the PWM value, the luminance control can be easily performed by the PWM control. Also, according to the present invention, the minimum LC
The time required to change from D brightness to the maximum LCD brightness,
The time required to change from the minimum luminance to the maximum luminance of each bent line portion is set, and the luminance control unit controls the LCD luminance along the luminance change curve and according to the set time when the ambient illuminance changes. Accordingly, the luminance can be controlled along the luminance change curve desired by the user and according to the luminance change speed desired by the user. As a result, the user can be prevented from recognizing a sharp luminance change by gradually controlling the luminance at a low luminance level at which the luminance change is easy to be perceived and rapidly controlling the luminance in a short time at a high luminance insensitive to the luminance change.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an automatic light control device of the present invention.

FIG. 2 is an explanatory diagram of a luminance change curve according to the present invention.

FIG. 3 is a flowchart of the overall control of the first embodiment.

FIG. 4 is a configuration diagram of a second embodiment.

FIG. 5 is a diagram illustrating a luminance change curve and a luminance change time according to the present invention.

FIG. 6 is an explanatory diagram of a conventional linear luminance change curve.

[Explanation of symbols]

1 ... LCD screen 2 ·· CFL (Cathod Fluorescent Lamp) 3 ·· E 2 PROM 4 ·· operation section 5 .. photosensor 6 ... AD converter 7 .. microcomputer 9 · switch 11 ... DC-DC converter 12. DC-AC converter 13. Transformer

Claims (3)

[Claims] 1. An automatic light control device for controlling the brightness of an LCD display device based on the ambient illuminance, a memory for storing a brightness change curve indicating a relationship between the ambient illuminance and the LCD brightness, and a linear approximation to the brightness change curve. At the start of the curve,
A setting unit for setting one or more intermediate break points and an end point and storing the same in a memory; obtaining an LCD luminance according to the current ambient illuminance from the luminance change curve obtained by approximating the straight line; An automatic dimming device for an LCD display, comprising a brightness control unit for controlling the brightness. 2. An LCD display device comprising: a backlight generating section for generating a backlight; and controlling a voltage applied to the backlight generating section by PWM to control the LCD.
2. The automatic dimming device for LCD display according to claim 1, wherein the luminance is controlled and the luminance change curve is specified by discrete values of ambient illuminance and PWM value. 3. The time required to change from the minimum LCD luminance to the maximum LCD luminance and the time required to change from the minimum LCD luminance to the maximum LCD luminance of each broken line portion are set, and the luminance control unit changes the ambient illuminance. 2. The automatic dimming device for LCD display according to claim 1, wherein the LCD brightness is controlled along the brightness change curve and according to a set time.