JPH04354281A - Image display device - Google Patents

Abstract

PURPOSE:To protect the neck part of the CRT from collision by detecting the fact that a video signal has become a silence signal and suppressing a signal to be supplied to a CRT below a black level, when a video signal having an aspect ratio different from that of the CRT is displayed. CONSTITUTION:A vertical synchronizing signal VD from a synchronizing separation circuit 1 is supplied to a diode 12, a resistance 6, a capacitor 8 and a transistor 9 which comprise a silence signal detection circuit, the presence or absence of the synchronizing signal is detected, the base voltage of a transistor 10 is controlled, and a signal level to be supplied to the CRT is controlled by the transistor 10 and a transistor 11 to whose base the control signal of a screen display mode is inputted.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to an image display device that displays video signals with different aspect ratios, and in particular displays high-definition television images with a wide aspect ratio called Hi-Vision, as well as standard aspect ratios. Ratio N
The present invention relates to an image display device that can also display TSC television images.

0002

[Prior Art] Conventionally, as image display devices that display video signals with different aspect ratios from the display section, current television receivers with a screen aspect ratio of 4:3 and high-definition screens with an aspect ratio of 16:9 have been used. When displaying a TV video signal or a movie with a wide aspect ratio, and vice versa, when displaying an NTSC TV video signal with an aspect ratio of 4:3 on a high-definition TV receiver with a screen aspect ratio of 16:9. There is. Furthermore, there are two methods for displaying NTSC television video signals on a high-definition television receiver: a normal mode in which the screen is displayed at an aspect ratio of 12:9 with the vertical direction of the screen as a reference, and non-displayed areas and additional information are displayed on the left and right sides; There are two types of wide aspect modes: display at an aspect ratio of 16:12 based on the horizontal direction of the screen, and cut out the upper and lower parts that are not displayed. According to these modes, it is necessary to switch the operation of the deflection circuit, for example, as shown in Japanese Patent Application No. 3-19103 ``Vertical Deflection Device for High Definition Television Receiver''. In order to prevent the electron beam from colliding with the neck of the CRT and heating and damaging the neck due to an increase in the deflection angle, a blanking signal that is expanded during the image period above and below the CRT is not displayed. It is added.

FIG. 2 shows such a conventional image display device. The input video signal is supplied to a synchronization separation circuit 1 and a video signal processing circuit 4. The sync separation circuit 1 separates the vertical sync signal VD from the input video signal and outputs it to the deflection circuit 2. The deflection circuit 2 generates a flyback pulse (FBP) for deflection from the input vertical synchronization signal VD and outputs it to the blanking signal generation circuit 3. The blanking signal generating circuit 3 generates a vertical blanking signal V-BLK from the input flyback pulse and outputs it to one input terminal of the mixing circuit 5. This vertical blanking signal V-BL
K and the video signal processed by the video signal processing circuit 4 are mixed by a mixing circuit 5 and sent to a CRT (display unit) not shown.

0004

[Problems to be Solved by the Invention] In the above-mentioned conventional image display device, when the image display device is in a no-signal state in which no video signal is input in the wide aspect mode, the deflection circuit 2 goes into a free-run state, and the vertical The timing of the blanking period and the vertical deflection did not match, and the electron beam collided with the neck of the CRT, causing the neck of the CRT to heat up and break.

Therefore, an object of the present invention is to suppress the generation of electron beams by lowering the video signal supplied to the CRT below the black level when there is no video signal, and to prevent CRT from collision with the electron beams.
An object of the present invention is to provide an image display device that protects the neck portion of an RT.

[0006]

[Means for Solving the Problems] Therefore, in order to achieve the above-mentioned object, the first present invention has a display section having a first aspect ratio, and a display section having the same aspect ratio as the first aspect ratio. or a second video signal having a second aspect ratio different from the first aspect ratio to display the first video signal and display the second video signal. When the signal is input, the synchronizing signal is separated from the first or second video signal in a display device that displays the vertical or horizontal length of the first aspect ratio according to the control signal. a synchronization separation circuit to output, a no-signal detection circuit to detect the presence or absence of a video signal from the synchronization signal, and a blackout video signal to be output to the display section based on the output from the no-signal detection circuit and the control signal. control means for controlling the temperature below the level.

[0007] The second invention has an aspect ratio of 16:9.
has a display section, and a first display section with the same aspect ratio as this display section.
or a second video signal with an aspect ratio of 4:3 is selectively input and displayed, and when the second video signal is input, the horizontal length is set to the horizontal length of the display section. In a display device that displays images in the same manner as above, a synchronization separation circuit separates and outputs a vertical synchronization signal from the first or second video signal, and a no-signal detection circuit detects the presence or absence of a video signal from this vertical synchronization signal. and a control means for controlling the video signal output to the display section to be below the black level based on the output from the no-signal detection circuit.

The third aspect of the present invention has a display section with an aspect ratio of 4:3, and a first video signal with the same aspect ratio as the display section or a second video signal with an aspect ratio of 16:9. In a display device that selectively inputs and displays a video signal, and when a second video signal is input, the vertical length is the same as the vertical length of the display section, a synchronization separation circuit that separates and outputs a horizontal synchronization signal from a video signal; a no-signal detection circuit that detects the presence or absence of a video signal from this horizontal synchronization signal; and control means for controlling the output video signal to be below the black level.

[0009]

[Operation] According to the present invention, the no-signal detection circuit smoothes the synchronization signal output from the synchronization separation circuit, and does not act on the video signal output to the CRT if the synchronization signal is always input. , if it is not input, the entire video signal going to the CRT is made below the black level.
This prevents the electron beam from colliding with the neck of the CRT, which is caused by the phase difference between the blanking period of the video signal and the deflection, thereby damaging the neck of the CRT. is solving a problem.

0010

Embodiment An embodiment of the present invention will be described below with reference to FIG. The figure shows the case where the present invention is applied to an image display device that displays a high-definition television with an aspect ratio of 16:9 or an NTSC television video signal with an aspect ratio of 4:3 on a display section with an aspect ratio of 16:9. . In the figure, a diode 12, resistors 6 and 7, a capacitor 8, and a transistor 9
constitute a no-signal detection circuit, and transistors 10 and 11
and constitute a control means, and the other parts are the same as the conventional one shown in FIG.

Next, the operation of the above-described image display device will be briefly explained. The input video signal is output to a synchronization separation circuit 1 and a video signal processing circuit 4, and the synchronization separation circuit 1 separates a horizontal synchronization signal (not shown) and a vertical synchronization signal VD. is outputted to the deflection circuit 2 and also to the diode 12 constituting the no-signal detection circuit. The deflection circuit 2 to which the vertical synchronization signal VD is input generates a flyback pulse for deflection and supplies it to the blanking signal generation circuit 3. The blanking signal generating circuit 3 generates a vertical blanking signal V-BLK and supplies it to one input terminal of the mixing circuit 5. The video signal from the video signal processing circuit 4 is supplied to the other input terminal of the mixing circuit 5, mixed with the vertical blanking signal V-BLK, and sent to a display section such as a CRT (not shown).

The vertical synchronizing signal VD input to the diode 12 is smoothed (integrated) by a resistor 6 and a capacitor 8, and then supplied to the base of a transistor 9. Vertical synchronization signal VD
If is always being output, by setting the values of resistor 6 and capacitor 8 appropriately, voltage will always be applied to the base of transistor 9, transistor 9 will be in the ON state, and the base voltage of transistor 10 will be at ground potential. Transistor 10 is turned off. Next, when the vertical synchronization signal VD is no longer output from the synchronization separation circuit 1, that is, when no video signal is input to the image display device, the base potential of the transistor 9 becomes the ground potential, and the transistor 9 is turned off. +
It becomes the potential of B. Therefore, the transistor 10 is turned on. When the screen is in the wide aspect mode, a control signal indicating the screen display mode is applied to the base of the transistor 11 to turn on this transistor. As a result, transistors 10 and 11 are turned on when the video signal becomes a no-signal state in wide aspect mode.
In this state, the video signal output to the CRT becomes approximately ground voltage, which makes the CRT completely black and prevents the electron beam from exiting the electron gun.The timing of the vertical blanking period and the vertical deflection does not match, and the electron beam reaches the CRT. This prevents the top and bottom of the neck from colliding.

In the above embodiment, the aspect ratio of the screen is 16.
We have described an image display device that displays an NTSC television video signal with an aspect ratio of 4:3 on a display section with a :9 aspect ratio.
In the case of an image display device that displays a high-definition television video signal with an aspect ratio of 16:9 on a display unit with a screen aspect ratio of 4:3, the aspect ratio is set to 5.3:3 with the vertical direction of the screen as the standard. When displaying by cutting off the portion that protrudes in the horizontal direction, the horizontal synchronization signal separated from the synchronization separation circuit 1 is smoothed and applied to the base of the transistor 9. Therefore, similarly to the above embodiment, when the horizontal synchronizing signal is no longer input, transistor 9 is turned off and transistor 10 is turned on. A control signal is applied to the transistor 10 in the ON state and the base of the transistor 11 in the ON state, and the video signal output to the display section becomes approximately ground potential, and the video signal becomes below the black level, and the electron beam is turned into the electron gun. This can prevent the electron beam from colliding with the left and right sides of the neck of the CRT due to misalignment of the timing between the horizontal blanking period and the horizontal deflection.

It goes without saying that the present invention can also be applied to an image display device that displays movies with a wide aspect ratio, for example, an aspect ratio other than 16:9 or 4:3.

Furthermore, in order to prevent the viewer from being confused due to the video signal being below the black level, an LED or the like may be lit to indicate that no video signal is being input. Furthermore, instead of lowering the video signal below the black level, a switching circuit may be provided to display on the display section a video signal that has been recorded in advance in a memory or the like and which calls the viewer's attention.

[0016]

As explained above, the present invention detects that the synchronization signal is in a no-signal state, and blanks the entire video signal at that time (brings the video signal below the black level). This has the effect of preventing the neck of the CRT from being heated and broken due to collision of electron beams with the neck.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention.

FIG. 2 is a block diagram showing a conventional embodiment.

[Explanation of symbols]

1 Synchronous separation circuit 2 Deflection circuit 3 Blanking generation circuit 4 Video signal processing circuit 5 Mixed circuit 6,7 Resistance 8 Capacitor 9,10,11 Transistor 12 Diode

Claims (3)

[Claims] 1. A first video signal having a display portion having a first aspect ratio, and having the same aspect ratio as the first aspect ratio or a second aspect ratio different from the first aspect ratio. selectively inputs a second video signal having
A display device that displays a display device with the same aspect ratio as vertical or horizontal length, a synchronization separation circuit that separates and outputs a synchronization signal from the first or second video signal, and the presence or absence of a video signal from the synchronization signal. The present invention is characterized by comprising: a no-signal detection circuit that detects the no-signal detection circuit; and a control means that lowers the video signal output to the display section to a black level or below based on the output from the no-signal detection circuit and the control signal. Image display device. 2. A display unit having a display unit with an aspect ratio of 16:9, and selectively inputting a first video signal having the same aspect ratio as the display unit or a second video signal having an aspect ratio of 4:3. In a display device that displays the same horizontal length as the horizontal length of the display unit when a second video signal is input, vertical synchronization is performed from the first or second video signal. A synchronization separation circuit that separates and outputs a signal, a no-signal detection circuit that detects the presence or absence of a video signal from this vertical synchronization signal, and a video signal that is output to the display section based on the output from this no-signal detection circuit. An image display device comprising: control means for controlling the image to a black level or lower. 3. It has a display section with an aspect ratio of 4:3, and selectively inputs a first video signal with the same aspect ratio as the display section or a second video signal with an aspect ratio of 16:9. In a display device that displays the same vertical length as the vertical length of the display unit when a second video signal is input, the horizontal synchronization is performed from the first or second video signal. A synchronization separation circuit that separates and outputs a signal, a no-signal detection circuit that detects the presence or absence of a video signal from this horizontal synchronization signal, and a video signal that is output to the display section based on the output from this no-signal detection circuit. An image display device comprising: control means for controlling the image to a black level or lower.