JPH0149233B2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention provides a video input terminal for inputting an external video signal and an RGB input terminal for inputting character/graphic information in addition to a normal television signal receiving circuit. This invention relates to a television receiver equipped with input terminals such as the following.

Conventional configuration and its problems In a television receiver equipped with a video input terminal and an RGB input terminal, the video mode,
As a method for switching to RGB mode, for example, if there are three video inputs, there is a method of sequentially switching from TV to Video 1 to Video 2 to Video 3 to RGB to TV. This is convenient when operating with a remote control transmitter. However, with this method, when the next broadcast is received while viewing the image of video 1,
If you want to watch a TV screen based on RF television signals (TV mode), you have to switch to video 2, video 3, and RGB sequentially, which is inconvenient.

Therefore, if you press the channel selection button on the television receiver, it will automatically return to TV mode, which will be very convenient as you can easily change to TV mode even if you are in any other mode. Therefore, there are conventional methods that do this.

The above-mentioned conventional example will be explained below with reference to the drawings. FIG. 1 shows a circuit in which, when the channel button of a television receiver is pressed, it returns to the television mode, no matter which mode it was previously in.

In FIG. 1, 1 is a counter, and when a mode switching pulse is input to a clock input terminal 1, a high level signal "H" is sequentially output to terminals . This high level “H”
The signal controls the mode switching of the screen. In the above counter, the terminal is a reset terminal, and when a reset pulse is input to this terminal, the counter is reset to television mode (terminal output "H").

The high-level "H" output terminals are sequentially switched by the mode switching pulse, but after switching sequentially from TV → Video 1 → Video 2 → Video 3 → RGB, if the next mode switching pulse is input again, the counter will start switching. 1 terminal becomes “H” level,
This "H" pulse is input to the reset terminal through the diode 4, and the TV mode (terminal "H") is reset.

3 is a reset pulse generation circuit when the power is turned on, which generates a reset pulse when the power is turned on, and this pulse is applied to the reset terminal of the counter 1 through the diode 5, and when the power is turned on, the counter starts from the TV mode (butterfly "H"). I will do it.

Reference numeral 2 denotes a circuit that generates a pulse when switching channels, and uses, for example, an AFC defect pulse when switching channels.

A pulse output from the pulse generating circuit 2 at the time of channel switching is applied to the reset terminal of the counter 1 through the diode 6. As a result, when the channel is changed, the mode is reset to the TV mode, and the mode returns to the TV mode even if the mode was previously in any other mode.

Now, some television receivers equipped with such an operation have a function of displaying a channel display number on-screen on a cathode ray tube screen when changing channels. The display method is also such that the size of the channel display number is changed in three stages by a channel switching pulse generated when switching channels. That is, the letters are first displayed in uppercase, then medium, then lowercase, and finally disappear.

Also, when switching the screen mode, for example, RGB
When changing from mode to TV mode, the number of the selected channel is displayed in lowercase letters, and when changing from TV mode to Video 1 mode, it is configured to display "Video 1" in lowercase letters. A conventional example is a television receiver.

When a television receiver with such a function is reset from video mode to television mode by pressing the channel button, the microcomputer that controls the on-screen first determines the channel change, and then In order to determine that the mode has changed, the channel number is briefly displayed in uppercase letters on the cathode ray tube screen, and then in lowercase letters, which creates an unnatural feeling when viewing.

One possible solution to this problem is to turn off the on-screen display for a certain period of time (the time during which lowercase letters are displayed) when pressing the channel button to change from video mode to television mode.

An example of a circuit for realizing this is shown in FIG. In FIG. 2, the same parts as in FIG. 1 are given the same numbers. In the figure, 7 is an on-screen display circuit, which is used when switching channels, modes, etc.
It operates to display on-screen the channel number, characters indicating the display mode, etc. on the cathode ray tube screen.
The collector of the transistor 9 is connected to the blanking terminal 7a of the on-screen display circuit 7,
The configuration is such that no on-screen display is performed when the transistor 9 is turned on. Reference numeral 10 denotes a transistor, to the base of which a positive pulse output from the pulse generation circuit 2 is applied via a resistor 11 during channel switching. A load resistor 12 is connected between the collector of the transistor 10 and the power supply terminal (12V).
A capacitor 13 is connected between each of them and the ground. Furthermore, the collector of the transistor 10 is connected to the transistor 18 via the Zener diode 14.
is connected to the base of Here, reference numeral 15 indicates an off-guarantee resistance of the transistor 18, and reference numeral 16 indicates a base resistance. The collector of the transistor 18 is connected to the anode of the diode 6 and the base of the transistor 9 via the resistor 8, respectively. 17
is the collector load resistance.

Next, the operation of the above configuration will be explained.
A pulse at the time of channel switching is applied to the base of the transistor 10 via the resistor 11. The pulse when switching channels is normally at “L” level.
Set to "H" level when switching channels. Therefore, normally the transistor 10 is off and its collector is at the "H" level, so the Zener diode 14 is conductive and the transistor 18 is turned on and the collector of the transistor 18 is at the "L" level. Therefore, transistor 9 is off, and on-screen display circuit 7 operates. On the other hand, when switching channels, the channel switching pulse enters the base, so the transistor 10 is turned on during that period, the charge stored in the capacitor 13 is discharged through the transistor 10, and the transistor 18 is turned off.

Next, when the channel switching pulse period ends, there is a delay by the charging time determined by the resistor 12 and the capacitor 13 and the time until the Zener diode 14 becomes conductive. goes from off to on. When the transistor 18 is off, the collector of the transistor 18 is at "H" level, and the transistor 9 is turned on for a certain period of time.
The on-screen display is blanked to prevent it from appearing.

Therefore, if you set this fixed time to the time when the uppercase letters of the first channel display are displayed, even if the channel is reset from video mode to TV mode, the on-screen display will not change when the channel is changed. Only the lowercase letters that are displayed at times will be displayed. However, when configured in this way, in a television receiver having an auto search channel selection function, a channel switching pulse is generated from the channel switching pulse generation circuit 2 each time a channel is selected during auto search, and the on-screen display circuit 7 is blanked for a certain period of time, which causes the problem that the on-screen display does not appear.

OBJECTS OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems and to provide a television receiver in which on-screen display is performed even during automatic search channel selection.

Structure of the Invention The television receiver according to the present invention is configured to stop the operation of the means for stopping the on-screen operation for a certain period of time when switching channels during automatic sweep tuning, and to switch to the automatic sweep tuning mode. By stopping the operation of the means in conjunction with the switching, channel on-screen display can be performed even during automatic sweep channel selection.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. In the figure, the same parts as in FIGS. 1 and 2 are given the same numbers.

FIG. 3 shows an embodiment of the present invention. In FIG. 3, reference numeral 19 denotes a channel switching pulse generation circuit, which also includes a fixed time delay circuit shown in FIG.
20 is an automatic sweep channel selection circuit, and 21 is a changeover switch, which has two circuits and two contacts, and the two circuit changes are interlocked with each other.

The terminal 25 of the changeover switch 21 is connected to the connection point between the resistor 8 and the base of the transistor 9.
6 is connected to ground, and the terminal 27 is an empty terminal (open). Terminal 2 constituting one switching circuit
2, 23, and 24 are connected by an automatic sweep channel selection circuit 20.

The side where terminals 22 and 23 are connected to each other (input side)
When the switch 21 is switched to , preset channel selection becomes possible (preset mode), and when a separately provided auto search switch is pressed, auto search for channel selection starts. When the preset mode is set in this way, the channel display is normally displayed on-screen on the cathode ray tube screen by flashing to indicate the preset mode, and during auto search the on-screen channel display signal is sent to the on-screen display circuit 7. It is output as . When the preset mode is set in this way, the terminals 25 and 2 of the switch 21
6 are connected to each other, the base of transistor 9 becomes low level, transistor 9 is turned off,
The on-screen display circuit 7 is no longer subject to blanking. That is, as described above, each time a channel is selected, the channel number is displayed on-screen in a blinking state.

If this switch 21 were not present, a default pulse would be generated from the channel switching pulse generation circuit 19 and applied to the base of the transistor 9, so that the on-screen signal would be defeated and not appear on the screen.

Note that when the preset mode is canceled, the switch 21 is turned off, the terminal 25 is not connected to the terminal 26, and the transistor 9 is not forced off.
As in the case of FIG. 2, when switching channels, on-screen defective operation is performed for a certain period of time.

With the above configuration, the initial objective can be achieved and channel on-screen display can be performed during automatic sweep channel selection.

Effects of the Invention According to the present invention, when changing channels from video mode, the on-screen display can display only the lowercase letters that are displayed when changing channels, while automatic sweep channel selection Also, the channel number can be displayed on-screen, which is extremely convenient in practice.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a conventional television receiver, FIG. 2 is a circuit diagram of a television receiver proposed prior to the present invention, and FIG. 3 is a circuit diagram of a television receiver according to an embodiment of the present invention. FIG. DESCRIPTION OF SYMBOLS 1... Counter, 7... On-screen display circuit, 9... Transistor, 19... Channel switching pulse generation circuit, 20... Automatic sweep channel selection circuit, 21... Changeover switch.

Claims (1)

[Claims] 1. For television receivers equipped with multiple external input terminals, when switching channels, the channel display number is displayed on-screen in three stages (upper case, middle case, and lower case), and when switching screen modes, , has a display means that displays a mode display with only lowercase letters on-screen on the screen, and a function to return to TV mode when channel selection is switched in a mode other than TV, and has an on-screen function for a certain period of time when switching channels. A stop control means for stopping, a return control means for restoring the on-screen function after a certain period of time, an automatic sweep selection means for automatically sweeping channels to be selected, and a period of time during which the automatic sweep selection means can operate. The television receiver comprises means for stopping the operation of a stop control means for stopping the on-screen function for a certain period of time when switching channels.