JPS62117481A - Brightness adjusting circuit - Google Patents

Abstract

PURPOSE:To automatically control brightness according to the state of a picture and to constantly and easily see the picture of a liquid crystal television by comparing a reference voltage relating to a white level of a video signal with the video signal and controlling the brightness of a picture display part by a comparison output. CONSTITUTION:The video signal Sv inputted from a video signal input terminal 1 is inputted to a negative input terminal of a comparator 2. To the positive input terminal of the comparator 2, the reference voltage E is inputted from a direct current power source 3 selected to a required value for obtaining the picture of the easily seeing brightness. From an output terminal 2a of the comparator 2, an output signal Sc of a pulse corresponding to a time length of the video signal of the white level exceeding the reference voltage is outputted and a voltage elevated according to a white level time is outputted from an integration circuit 4. The voltage outputted from a terminal 5 is inputted to an alternating current driving waveform generating circuit as a luminance signal to maintain a constant brightness.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a brightness adjustment circuit for an image display device, and more specifically to a brightness adjustment circuit suitable for application to a liquid crystal television.

[Prior art]

Conventional liquid crystal televisions on the market have a configuration in which the brightness of the image display section is adjusted by manually operating a brightness adjustment knob provided on a variable resistor.

[Problem to be solved]

Conventional liquid crystal televisions of this type require manual operation to adjust the brightness of the image, resulting in the inconvenience of having to frequently operate the brightness adjustment knob as the image condition changes.

In other words, it is necessary to lower the brightness when bright images continue, and increase the brightness when dark images continue to obtain an easy-to-see image.

[Means for solving problems]

The present invention has been made to solve such problems, and the present invention compares the video signal of the image displayed on the image display section with a reference voltage related to the level within the video signal, and uses the comparison to determine By controlling the brightness of the image display section using the obtained output, it! The brightness of the small part of the image table is changed in relation to the brightness of 1itJJ.

The brightness adjustment times +1'3 of the present invention are displayed on the image display section.
A comparator circuit is provided for comparing the reference voltage point associated with the video signal level of the video signal and the video signal level of the video signal, and the output of the comparator circuit is The present invention is characterized in that the brightness of the display section can be controlled by L7, and further, the brightness can be controlled by the output number of an integrating circuit that integrates the output of the comparator.

[Effect]

When the video signal 114 has a high level 4), the brightness of the rllII image front edge is automatically adjusted in relation to the video signal so that the brightness is lowered.

〔Example〕

The present invention will be described in detail below based on drawings showing embodiments thereof. FIG. 1 is an electrical circuit diagram showing a luminance jlQ adjustment circuit according to the present invention, in which 1 is a video signal input terminal for a video signal Sv, and 2 is an input terminal for a video signal Sv.

Video signal input terminal 1 is connected to one terminal of inverter 2 via resistor R3. -1 terminal of comparator 2? This is done through 11℃mR, 1. -c Itg
iP power n,: 1 of 3 DC power supplies for +<lj;
醋)子 is followed by 1. The reference voltage jE E's voltage L[shi・\le is] 4 is an image of easy-to-see brightness 4 The required blue color (llII?i2 is selected.21 Output of inverter 2, '$1'2a is resistance ti'+l F?
', Sheeny:,, Integral cycle lI' consisting of %den90
84 to the end of the brightness adjustment i'J variable resistor Rv (
, 7, , tl, * et al.
The intermediate terminal portion Rci,'I of ν, the image display portion ζ1, and the luminance signal output terminal Y5 which provides the luminance.

-1 Luminance adjustment emergency town change grinding resistor Rv is not shown in the figure j-1 brightness m [
The intermediate terminal portion Rc is interlocked and connected to the adjusting tab pp.

In the circuit configured as described above, the video signal Sv is transmitted from the video input terminal I to one end/l of the input terminal 2.
','' given, the comparator L/-Y2 is the same D4
Perform the 11-axis operation with the reference voltage Sv and the reference voltage rr [i:).

Figure 2 is a waveform diagram showing the relationship between the video signal white L -\ and the reference voltage 1F, which is applied to three fields of the video signal. The peak) indicates the case where there are many white peaks that exceed the reference voltage r=, and the peak) indicates the case where there are few white peaks that exceed the reference voltage r=. When a video signal Sv as shown in FIG. , and outputs a pulse output signal Sl corresponding to the video signal time width of the portion exceeding .

The pulse width of the output f-JSc of comparator 2 exceeds the reference voltage E...depending on the short time, it changes to 2. Then, corresponding to the output signal Sc, the terminal voltage of the aza 0 is gradually reduced to 1! by an integral operation. n'sa-U
Therefore, 111 variable resistance 1? The middle of ν+Mil 7 part 11c, that is, the luminance signal output terminal 5? li T-T is -1, -Isui・.

The voltage at this luminance signal output terminal /-5 is given by (, i, C AC drive waveform generation times Vat:) -j,
J+ and Fig. 2 fat, (Ill Bideny signal Sv
Corresponds to ゛・(-Figure 3(a).

■) The cross/Af and driving J waveforms VD as shown in i! JY1
, this is applied to the image display section, and the i+Iiii image is displayed on the 1illii image display section.

That is, when the video signal white level exceeds the reference voltage jF F many times in a row, as shown in 1b+ in FIG.
In this way, the height of the AC drive waveform is lowered and the brightness is lowered to display an easy-to-see image. J: Tatan SI Otoko 2nd
Figure 1b+! , : Nishi J-like, base! 'P turtle pressure i-: Deni Teo's signal is white! When the number of /-• is small and not continuous, the voltage at the brightness signal output terminal 5 is low, and the brightness is maintained as it is, as shown in FIG. In other words, video (R
The heights of the AC driving waveforms VC) are approximately the same as the peaks in FIG. 3(a), and uniform brightness is always obtained.

However, considering the extent to which the image is difficult to see, the brightness of the image display section is low and the image is difficult to see. When this happens, the voltage level is set high, and on the other hand, when the display state is such that images with high brightness and difficult to see continue, ζ2.' is set to a high voltage level.
Set health low.

Since the voltage at the luminance signal input terminal 5 gradually increases to 11 due to the integration operation by the integrating circuit 4,
When the output signal Vc of the pulse is extremely sporadic, the voltage 11- of the luminance signal output terminal 5 is low, so that the video signal 1, which exceeds the reference voltage E, is generated from Qj. In this case, lower the brightness by -1 and do not adjust the brightness.

Integral time again! /34 resistances 1 and 2! )-'Fusa0
By changing the value of , the sensitivity of luminance (11J) can be made smaller or higher.

Effect C] As explained in detail in the present invention, 1. The brightness adjustment of the image display section is automatically adjusted in relation to the video signal white level of the image displayed on the image display section. , The troublesome adjustment operation by one movement is l'P'+! Erase. Also, the brightness is related to the video signal white/hell, and the image displayed on the image display section is always easy to see.'7.
ir, it is possible to provide a high-quality liquid crystal television with excellent performance. Further, the present invention provides similar effects even when the image display section is a cathode ray tube.

[Brief explanation of drawings]

FIG. 1 is a brightness adjustment circuit for implementing the present invention, FIG. 2 (a) is an explanatory diagram showing the relationship between the video signal waveform and the base voltage, and FIG. (+11 is an AC drive waveform diagram input to the image display section. 1... Video amplification terminal section 2... Comparator 3
...DC power supply 4...Integrator circuit 5...Brightness signal output 6g/S v...Video signal Sc...
・Output ratio -1-E...Reference voltage

Claims (1)

[Scope of Claims] 1. A comparison circuit that compares a video signal of an image to be displayed on an image display section with a reference voltage related to a video signal white level of the video signal, and an output of the comparison circuit compares a video signal of an image to be displayed on an image display section. A brightness adjustment circuit characterized in that the circuit is designed to control the brightness of a computer. 2. A circuit comparison circuit that compares a video signal of an image to be displayed on an image display section with a reference voltage related to the video signal level of the video signal, and an integration circuit that provides an output of the comparison circuit, the integration circuit A brightness adjustment circuit characterized in that the brightness of an image display section is controlled by the output of.