JPS62133872A - Video signal switching circuit of display monitoring equipment - Google Patents

Abstract

PURPOSE:To improve operability by providing a switching circuit that control video signals outputted from a signal outputting circuit stoppably according to presence or absence of horizontal synchronizing signals and monitoring video made by specified video signals when horizontal synchronizing signals are not inputted. CONSTITUTION:A personal computer is connected to an input terminal A by a signal cable. When horizontal synchronizing signals are outputted from the computer, the signals are detected by a diode 1 to obtain DC voltage, and smoothened by a capacitor 2. When a diode 5 is made on by the output through an invertor 4, a signal output circuit 6 becomes low level, and video signals are not inputted to a video circuit 7. On the other hand, when horizontal synchronizing signals are inputted to the terminal A, output of the invertor 4 in a switching control circuit becomes high level the diode 5 is made off. Thereby, specified video signals are inputted from the circuit 6 to the circuit 7, and a video formed by specified video signals is displayed on the display screen.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a display monitor for monitoring on a display a video signal from a television or the like or a video signal from a personal computer. Concerning L4 id! The present invention relates to a video signal switching circuit that switches between multiple video signals.

[Conventional technology]

Conventionally, a display monitor device inputs a video signal from a television or a personal computer, and displays the video signal on the Nice Play! If there are at least two or more video signals, connect the devices that generate the video signals using connection cables and connectors, and install the manual on the display side. Generally, a method is used in which a video signal switching circuit using a switch or a switching IC is provided and two or more video signals are switched by nine steps.
It is.

Mata. For example, in a configuration where a personal computer that outputs one video signal and this display monitor device are connected, if the video signal is not output from the personal computer, or if the connector for the connection is disconnected. Normally, nothing was displayed on the display.

[Problem that the invention seeks to solve]

In the video switching circuit of the conventional display monitor device as described above, the above-mentioned manual switch, etc. must be operated each time multiple video signal switching circuits are to be switched, which makes the operation cumbersome. In a connected state where a pair of devices such as a personal computer are connected, for example, if the :t connector of that connection is disconnected, nothing will be displayed on the screen and it will be difficult to determine whether or not the connection is connected. I'm afraid the problem is that you can't do it on the screen.

This invention was made in order to solve all of the above-mentioned problems.It is a display monitor that can be identified on the display screen when the connection between the device that outputs the video signal and the ice play device is disconnected. The objective is to obtain money for the video signal switching circuit of the device.

[A precautionary measure to resolve the problem]

The video signal switching circuit of the display monitor device 4 according to the present invention includes a signal output circuit that outputs a predetermined video signal;
A switching circuit is provided, which converts a horizontal synchronizing signal of a video signal inputted from the outside into a direct current, and controls the video signal outputted from the signal output circuit to be stopped depending on the presence or absence of this horizontal synchronizing signal, and the horizontal synchronizing signal is When no input is made, the video according to the predetermined video No. 1Δ can be monitored on the display.

[Effect]

The video signal switching circuit according to the present invention switches the predetermined video f'G signal output from the signal output circuit when the horizontal synchronizing signal from the external personal computer is lost due to disconnection from the external personal computer or the like. By inputting it to the video circuit, it is displayed on the screen of a predetermined video love play, and if there is a horizontal open 1υjii No. 4, this signal is converted to DC, and this DC output (low level) is output from the signal output circuit. A predetermined one signal? Since the image from the personal computer or the like is displayed on the picture IC of the gold display, it is possible to judge whether there is a connection between the external devices as described above on the display screen.

[Embodiments of the Invention] Hereinafter, all the drawings of the embodiments of the present invention will be explained. FIG. 1 is a circuit diagram showing one embodiment of the present invention.

In the figure, (1) to (5) are the components constituting the switching control circuit flG, and (1) is a diode (first diode), which is connected to a signal cable (connection +2). +31 is connected to the ground potential and the cand fl11 of the diode (1) so that the DC voltage detected by this diode +11 is completely smoothed. A capacitor and a resistor (4) are connected in parallel between the capacitor (2) and the resistor (3), and the inverter receives all the DC voltage smoothed by the capacitor (2) and resistor (3) and inverts the polarity.

In this embodiment, a two-man powered gate (2NAND-GATE) is used.
) is connected to the input side, the polarity of the input high or low level DC voltage is inverted, and the full low or high level output is produced, respectively. In addition, 15) is a diode (
A second diode is connected at its cathode to the output of the inverter. (61 is a signal output circuit that generates a predetermined video signal.

Its output is connected to the video circuit (7) and the switching control circuit Ill.
When the output of the inverter +41 is at a high level, a predetermined video signal is input to the video circuit (7), and when it is at a low level, the signal is input by the action of the diode (5). The output circuit (61) and the video circuit (7) are set to a low level to stop inputting a predetermined video signal to the video circuit (7).

Next, the operation of the display monitor device having the above configuration will be explained with reference to FIG. First, when a horizontal synchronizing signal is input from the personal computer to input terminal a, that is, when the personal computer is connected to this display monitor device by a signal cable, and when the horizontal synchronizing signal is output from the personal computer, This horizontal synchronization signal is connected to the diode (1)
By detecting the waves, a direct current '1' is obtained, and this direct current pressure is smoothed by a capacitor (2). Here, the constants of this capacitor (2) and resistor (3) are such that when the horizontal synchronizing signal is input, the connection line between the cathode of the diode tl+ and the inverter (4) is at a high level (H
The constant must be set so that the Next, when the high level signal tone inverter (4) is input, its output becomes low level (LOW LbvgL).
The diode (5) then turns on, and this on operation causes the output side of the signal output circuit (61 to be at ground center).
The video signal output from the signal output circuit (6) is not input to the video circuit (7). Therefore, when the horizontal synchronizing signal is input to the input terminal A, the video signal from the signal output circuit +61 is stopped by the action VC of the switching control circuit III.

On the other hand, if the horizontal synchronizing signal is not input to input terminal A because the signal cable between the personal computer and this display monitor device is disconnected, the output of the inverter (4) in the switching control circuit becomes high level, and the diode ( 51 turns off.

By turning this off, a predetermined video signal is input from the signal output circuit (61) to the video circuit (7), and a video based on the predetermined video signal is displayed on the display screen. It is possible to determine whether the signal cable between the two is disconnected or the video signal is not being input.

Note that in the above embodiment, the signal output circuit is as follows.

A predetermined video signal is output, but instead of this video signal, a video signal such as a video signal used for a general television etc. is used, and when the personal computer is not in use, It may be displayed on the screen of a display, and the same effect as in the above embodiment can be achieved.

〔Effect of the invention〕

As described above, according to the present invention, the horizontal synchronizing signal from an external personal computer or the like connected to the display monitor device is converted to DC by the switching control circuit, and the signal output circuit outputs the signal depending on the presence or absence of this horizontal synchronizing signal. Since the predetermined video signal is controlled so that it can be stopped by the output of this switching control circuit, it can be switched automatically without manual operation using a manual switch, etc., and it is easy to connect to an external personal computer. A predetermined image is displayed on the display screen when the lint is disconnected, making it easier to determine whether it is connected or not, improving operability.
It also has the effect of being economical because it can be constructed from inexpensive parts.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing a video signal switching circuit of a display monitor (a) according to an embodiment of the present invention. In the figure, (1) is a diode (first diode)
, +2) is a capacitor, (, phantom is a resistor, (4) is an inverter, (5) is a diode (second diode), !(
i+ is a signal output circuit, ;7) is video version '4.013
is a switching control circuit. Note that the same reference numerals in Figure 1 indicate the same or equivalent parts.

Claims (2)

[Claims] (1) Connected to the video circuit in a video signal switching circuit of a display monitor device that inputs externally input video signals to the video circuit in a switchable manner and monitors the video on the display using the input video signals. A signal output circuit that outputs a predetermined video signal to this video circuit is connected to a connection point between the video circuit and the signal output circuit, and the horizontal synchronization signal of the video signal input from the outside is converted to DC. a switching control circuit configured to stop the output of the signal output circuit; when a video signal is input from the outside to the switching control circuit, an image based on this video signal is displayed on the display; 1. A video signal switching circuit for a display monitor device, characterized in that a predetermined video signal output from the signal output circuit is displayed on a display when no video signal is input. (2) The switching circuit includes a first diode that detects a horizontal synchronizing signal in the other input video signal, a resistor that smoothes the signal detected by the diode, and a smoothing circuit that includes a capacitor. It consists of an inverter that inverts this smoothed DC signal and a second diode that operates when the output of this inverter is at a low level.
When the horizontal synchronization signal is input, the output of the inverter becomes low level, so that the output of the signal output circuit is set to ground potential via the second diode, and the output of this signal output circuit is stopped. A video signal switching circuit for a display monitor device according to claim 1, characterized in that: