JPH0620311B2 - Television receiver - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a television receiver provided with a video input terminal and a group of RGB external input terminals in addition to ordinary television broadcast reception.

2. Description of the Related Art Generally, in a television receiver of this type, when a screen mode is changed, a mode selection switch is manually operated to select a signal appearing on the screen. Conventionally, the RGB external input terminal group includes an RGB 21-pin input type having an AV control signal input terminal and an RGB 8-bin input type having no AV control signal input terminal. In the case of the RGB 21-pin input type, it is not necessary to operate the mode selection switch on the television receiver side by switching the AV control signal on the personal computer side connected to the television receiver. It is necessary to operate the mode selection switch on the receiver side to switch the mode.

Problems to be Solved by the Invention As described above, conventionally, in the case of the RGB 8-pin input type, when it is desired to display the personal computer input screen on the television, it is necessary to press the screen mode selection switch to switch it, which is inconvenient in terms of operability.

An object of the present invention is to provide a television receiver in which the screen automatically switches from the television mode to the RGB external input mode when a signal is input to the RGB external input terminal group.

Means for Solving the Problem The television receiver of the present invention is provided with a detection circuit for detecting the presence / absence of a horizontal synchronizing signal at a horizontal synchronizing signal input terminal of an RGB 8-pin input type external RGB input terminal group, and an image receiving unit. The external RG when the detection circuit detects a horizontal synchronizing signal in the television / external RGB switching circuit for selecting the signal to
The detection circuit is configured to supply the B signal to the image receiving unit, the horizontal synchronization signal input terminal of the external RGB input terminal group is connected to the base of the first transistor through the first resistor, and The collector of the transistor is connected to the power supply voltage, the emitter of the first transistor is connected to ground through the second resistor, and the emitter of the first transistor is connected to the base of the second transistor through the integrating circuit. ,
The collector of the second transistor is connected to the base of the third transistor and to the power supply voltage via the third resistor, the emitter of the second transistor and the emitter of the third transistor are connected to ground, and The collector of the transistor of 3 is connected to the power supply voltage via the fourth resistor,
From the collector of the third transistor to TV / external RGB
It is characterized in that the control signal for the switching circuit is taken out.

With this configuration, when the power supply of the device connected to the RGB external input terminal group is turned on and the external horizontal synchronizing signal is input from the RGB external input terminal group, this is detected and the screen display mode is switched. , It is not necessary to manually operate the screen mode selection switch on the television receiver side.

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

In the figure, reference numeral 1 denotes an external RGB 8-pin input terminal group, and signals from external devices applied to pins 1 to 8 are as follows.

1st pin ... Empty bin 2nd pin ... R signal 3rd pin ... G signal 4th pin ... B signal 5th pin ... Ground 6th pin ... Ground 7th pin ... Horizontal sync signal 8th pin ... Vertical sync signal Reference numeral 16 is a detection circuit for detecting the presence or absence of an external horizontal synchronizing signal, and the base of the emitter follower of the transistor 5 is connected to the seventh pin of the input terminal group 1. Transistor 5
The signal of the emitter of is integrated by the integrating circuit composed of the resistor 7 and the capacitor 8. When there is a horizontal synchronizing signal, the base of the transistor 10 becomes "high" level, the transistor 10 becomes conductive, and the collector of the transistor 10 becomes The "low" level, and the collector of the transistor 12 becomes the "high" level. 2, 4, 6, 9, 11, 13, and 14 are resistors, 3 is a protective zener diode, and + B is a power supply voltage. Reference numeral 15 is a television / external RGB switching circuit, the collector voltage of the transistor 12 is applied to the control terminal through the resistor 13, and the voltage applied to the control terminal is "high".
If it is a level, the switching circuit 15 is on the external RGB side, and the output signal to the display section is in the external RGB mode.

With this configuration, the RGB image can be displayed on the television receiver.
When the power of the external device connected through the pin input terminal group 1 is turned on, the horizontal synchronizing signal is input to the 7th pin by this, the collector of the transistor 12 is inverted to the “high” level, and the switching circuit 15 is automatically operated. Therefore, it is switched to the external RGB side applied to the 2nd to 4th pins, and there is no need to operate the screen mode selection switch on the television receiver side as in the prior art. When the power of the external device is turned off, the horizontal synchronizing signal input to the 7th pin disappears and the base of the transistor 10 returns to the "low" level.
The transistor 10 is turned off. Therefore transistor 12
Is turned on, the collector of the transistor 12 becomes "low" level, the control terminal of the switching circuit 15 becomes "low" level, the switching circuit 15 becomes the television mode side, and the television signal is displayed on the display portion.

In the above embodiment, the RGB pin input type has been described as an example. However, by using the RGB 21 pin input type, a television image can be received only by turning on the power of the external device without switching the AV control signal on the external device side. The screen display mode of the machine can be set to the external device side.

EFFECTS OF THE INVENTION As described above, the television receiver of the present invention is provided with a detection circuit for detecting the presence / absence of the horizontal synchronizing signal of the horizontal synchronizing signal input terminal of the external RGB input terminal group, and the signal to the image receiving unit Since the television / external RGB switching circuit to be selected is configured so that the detection circuit supplies the external RGB signal to the image receiving unit when the horizontal synchronizing signal is detected, the external device connected via the external RGB input terminal group is turned on. The screen display mode can be switched by simply turning it on / off, and the operability is greatly improved compared to the conventional one in which it is always necessary to manually operate the mode selection switch on the television receiver side when switching the screen display mode. It is a thing. The mode selection switch on the television receiver side is made possible by a connector part having a simple structure using an RGB 8-pin input type external RGB input terminal group without an AV control signal input terminal and a detection circuit connected to this connector part. The screen display mode can be automatically switched to the external device side without any operation.

[Brief description of drawings]

The drawing is a block diagram of the essential portions of an embodiment of a television receiver of the present invention. 1 ... External RGB 8-pin input terminal group, 5, 10, 12 ... Transistor, 8 ... Integrating capacitor, 15 ... TV /
External RGB switching circuit, 16 ... Detection circuit

Claims (1)

[Claims] 1. A television / external RGB switch for selecting a signal to an image receiving portion by providing a detection circuit for detecting the presence or absence of a horizontal synchronizing signal at a horizontal synchronizing signal input terminal of an RGB 8-pin input type external RGB input terminal group. A circuit is configured to supply an external RGB signal to the image receiving unit when the detection circuit detects a horizontal synchronization signal, and the detection circuit is configured to connect the horizontal synchronization signal input terminal of the external RGB input terminal group through a first resistor. Is connected to the base of the first transistor, the collector of the first transistor is connected to the power supply voltage, and the emitter of the first transistor is connected to the ground via the second resistor.
The emitter of the transistor is connected to the base of the second transistor through the integrating circuit, the collector of the second transistor is connected to the base of the third transistor, and is connected to the power supply voltage through the third resistor, The emitter of the second transistor and the emitter of the third transistor are connected to ground, the collector of the third transistor is connected to the power supply voltage via the fourth resistor, and the collector of the third transistor is connected to the TV / external RGB. A television receiver configured to extract a control signal for a switching circuit.