JPH0327120B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a signal switching device for a color television receiver that is equipped with an external RGB input terminal and has an on-screen display function.

Conventional configuration and its problems FIG. 1 shows a block diagram of a conventional signal switching device for a color television receiver having an external RGB input terminal and using an on-screen display.
In Fig. 1, the integrated switching circuit A switches the color difference signals R-Y, G-Y, B-Y and the RGB external input signal, and the next switching circuit B switches the color difference signals selected by the switching circuit A. Signal and on-screen RGB
Switching signals. Here, switching circuit A controls switching between the color difference signal and RGB external input signal using the TV/RGB switching signal, and switching circuit B uses the on-screen character display signal to control switching between the signal selected by switching circuit A and the on-screen RGB input signal. Controls signal switching. However, with this switching means,
Two switching ICs are required, making the cost extremely high.

OBJECT OF THE INVENTION The present invention eliminates the above-mentioned drawbacks and provides a
To provide a signal switching device capable of switching between a color difference signal, an external RGB signal, and an on-screen display RGB signal with a single IC, and also giving priority to the on-screen display RGB signal even when an external RGB signal is selected. The purpose is to

Composition of the Invention The signal switching device according to the present invention has a color difference signal and a color difference signal.
While a single integrated switching circuit is used for RGB signal switching, a blanking circuit for on-screen character display signals consisting of transistors, resistors, capacitors, etc. is provided, and when on-screen display is performed, this blanking circuit is used. outside
By applying blanking to the RGB signal and superimposing the on-screen RGB signal through a diode during the blanking period, the RGB
This gives priority to on-screen display when selecting a signal.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 2 is a wiring diagram of a signal switching device in an embodiment of the present invention. In FIG. 2, three color difference signals R-Y, G-Y and B-Y are supplied as one input to a switching circuit 1 which is an integrated circuit. The RGB external input signal (hereinafter abbreviated as external RGB signal) has resistors 6 and 5, resistors 12 and 1, respectively.
1, and is connected to the switching circuit 1 as the other input through a series circuit of resistors 18 and 17. The TV/RGB switching signal is connected to the switching control terminal 1a of the switching circuit 1.

The RGB signals of the on-screen color signal are sent to the RGB switching circuit 1 through diodes 2, 3, and 4, respectively.
Connected to the input side.

Also, during on-screen display, the on-screen character display signal that becomes "H" level is connected to capacitor 9 and resistor 10, and capacitor 16 and resistor 1.
5. It is connected to the bases of transistors 7, 13, and 19 through parallel circuits of a capacitor 22 and a resistor 21, respectively. Each transistor 7, 13,
19 has a resistor 8 for low level guarantee.
14 and 20 are each connected between the ground.
Further, the emitters of transistors 7, 13, and 19 are each connected to ground. The collector of transistor 7 is connected to the connection point between resistors 5 and 6, the collector of transistor 13 is connected to the connection point between resistors 11 and 12, and the collector of transistor 19 is connected to the connection point between resistors 17 and 18, respectively. Further, the onstareen character display signal is connected to the switching control terminal 1a of the switching circuit 1 via a diode 23.

Next, the operation of this circuit will be explained. Switching circuit 1
is on the color difference signal side if the switching control terminal 1a is at "L" level, and if it is at "H" level.
It switches to the RGB signal side.

Switching between the color difference signal of the TV signal and the external RGB signal is controlled by the TV/RGB switching signal. is applied to the switching control terminal 1a and controlled.
Now, the TV/RGB switching signal is at “H” level.
When the RGB external input signal is selected and the on-screen character display signal goes to "H" level at the same time, the transistors 7, 13, and 19 are turned on, and the RGB external input signal is not input to the switching circuit 1. Instead, on-screen color signals R, G, and B are applied to the switching circuit 1 via diodes 2, 3, and 4 to display on-screen characters.

In other words, only the on-screen display part is displayed externally.
This means that the RGB signal has been blanked,
When RGB mode is selected, on-screen signals will have priority. Here, capacitors 9, 16,
22 is for blanking and phase correction of on-screen color signals.

Effects of the Invention As described above, according to the present invention, it is possible to switch between a color difference signal, an external RGB signal, and an on-screen display RGB signal with a single switching circuit.
Furthermore, even when selecting an external RGB signal, priority can be given to the RGB signal for on-screen display.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a conventional signal switching device, and FIG. 2 is a wiring diagram of a signal switching device according to an embodiment of the present invention. 1...Switching circuit, 2, 3, 4, 23...Diode, 5, 6, 8, 10, 11, 12, 14, 1
5, 17, 18, 20, 21...Resistance, 7, 1
3,19...transistor, 9,16,22...
condenser.

Claims (1)

[Claims] 1. A color difference signal, an external RGB signal, and an on-screen display RGB signal are input, and a color difference signal and an RGB signal are input.
A signal switching device capable of outputting an RGB signal for on-screen display when displaying a color difference signal and on-screen display of an RGB signal for on-screen display when displaying an external RGB signal, comprising: signal and either an external RGB signal or an RGB signal for on-screen display are input, and either a color difference signal or an RGB signal is output depending on the TV/RGB switching signal input to the control terminal. a switching circuit for supplying an on-screen display RGB signal connected to an RGB signal input of the switching circuit; and a pair of unidirectional elements for supplying an RGB signal for on-screen display connected to an RGB signal input of the switching circuit; The external
a set of switching means for blanking an input of an RGB signal to the RGB signal input; an anode connected to an input of the set of switching means for supplying an on-screen character display signal;
a cathode connected to a control terminal of the switching circuit, and when the switching circuit is in the color difference signal selection state, inputting the on-screen character display signal causes the switching circuit to be in the RGB signal selection state. a first on-screen display mode in which an RGB signal for on-screen display is displayed on-screen; and a first on-screen display mode in which an RGB signal for on-screen display is displayed on-screen; and when an RGB signal is selected by the switching circuit, an external RGB signal is displayed by inputting an on-screen character display signal The second one cuts off the RGB signal for on-screen display and displays it on-screen.
A signal switching device configured to allow selection of on-screen display modes.