JP2636339B2 - On-screen mixing circuit - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an on-screen mixing circuit of a television receiver with built-in character multiplexing.

2. Description of the Related Art Initially, for a television receiver, a character multiplex decoder was formed separately in the form of an adapter and sold separately. Therefore, today's television receivers with built-in character multiplexing are simply televisions with built-in character multiplexing adapters, and the on-screen mixing circuit is switched on-screen by a switching circuit 30 integrated as shown in FIG. The signal and the character multiplex signal are switched to match the character multiplex signal and the on-screen signal.

That is, the on-screen blanking signal (hereinafter referred to as "O-BLK") and the transistor 31 receiving the O-BLK signal are used to switch the output signal which is an on-screen signal only during the O-BLK period and which is otherwise a character multiplex signal. It was obtained from the output of circuit 30. Although not shown, this signal is switched to an RGB signal by television broadcasting at a later stage and displayed on a screen. In FIG. 3, a switching circuit 30 for switching between an on-screen signal and a character multiplex signal has a character multiplex RGB signal on pins 1, 2, and 3 and an on-screen RGB signal on pins 11, 12, and 13.
O-BLK to which signals are respectively input and added to pin 4
The signal is switched between a character multiplexed RGB signal and an on-screen RGB signal, and a character multiplexed signal combining the on-screen signals is output from pins 5, 6, and 8. This signal is switched to a television RGB signal by an O-BLK signal and a character multiplexed Ys signal at a later stage.

However, the character multiplexed RGB signal is composed of a full luminance signal, a half luminance signal, and a full black signal (no signal), and as shown in FIG. A signal indicating the presence or absence of a signal, a Z signal indicating “L” level at half luminance,
-Made by B signal. That is, a character multiplexing circuit
Signal processing is performed at 40, and R,
It is added as G and B signals. In FIG. 4, 41 and 42 are TTL AND circuits, and 43 is an emitter-follower IC. The R signal is input from pins 10 and 12 of the TTL AND circuit 41, and the buffered R signal is output from pin 11. On the other hand, the Z signal is applied to pin 9 and its AN
The D output is output from pin 8. This output (pins 11 and 8
Pin) is mixed by resistors R1 and R2, and emitter-follower IC
It is input to the 10th pin 43, and is output as a character multiplexed R signal from the 4th pin. G signal and B signal are processed in the same way,
It becomes character multiplexed R, G, B signals. As described above, conventionally, an on-screen signal is added after converting a character multiplex signal into a complete signal, so that the circuit is complicated, and the advantage of the television with built-in character multiplex is not utilized. Therefore,
The cost was also high.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide a television receiver with a built-in character multiplexing circuit that can combine a character multiplexed signal and an on-screen signal with a simple and inexpensive circuit.

Means for Solving the Problems An on-screen mixing circuit according to the present invention receives an on-screen R, G, B signal and an on-screen blanking signal, shapes the waveform, and outputs each signal.
An input AND TTL circuit, a two-input AND TTL circuit that receives a character multiplexed R, G, B signal and an inverted on-screen blanking signal, and a character multiplexed R, G, B signal and polarity It has a three-input AND TTL circuit for inputting an inverted on-screen blanking signal and a character multiplexed half-brightness signal, and an output circuit for mixing and outputting the outputs of the respective AND TTL circuits by resistance coupling. .

Function The on-screen mixing circuit of the present invention makes it possible to mix a character multiplexed signal and an on-screen signal with a simple circuit and supply them at low cost, taking advantage of the advantage of a television with built-in character multiplexing.

Embodiment An embodiment of the present invention will be described below with reference to FIG. 1 and FIG.

In FIG. 1, on-screen RG is used as an input signal.
There are a B signal and an O-BLK signal, and a character multiplexed RGB signal and a Z signal (character multiplexed half-brightness signal). On-screen R,
The G and B signals and the O-BLK signal are input to a two-input AND TTL circuit 1 and buffered, and are respectively 8, 11, and
Output from pins 3 and 6. O- output from pin 6
The BLK signal is inverted by the transistor 4 at the same time when the BLK signal is connected to the circuit at the subsequent stage.
Input to pins 3, 11, and 13 of AND TTL circuit 4 with pins 9 and 12 and 3 inputs. Each AND gate Z of 2-input AND TTL circuit 2
Character multiplexed R, G, and B signals are applied to the other inputs of R, ZG, and ZB through pins 13, 10, and 5, respectively. Also, 3 inputs
The remaining two inputs of each of the AND gates HR, HG, HB of the AND TTL circuit 3 are supplied with R, G, B and Z signals of character multiplex. Accordingly, during the O-BLK period, all the AND TTL outputs of the AND TTL circuits 3 and 4 are at the “L” level, and the on-screen RGB signals are output at a level determined by the peripheral resistance value.

In addition, the character multiplexed R signal is input to the 13
The input is input to the pin 10 of the 3-input AND TTL circuit 3 and the 11-pin of the 2-input AND TTL circuit 2 outputs a character multiplexed R signal excluding the O-BLK period. The Z signal is input to pin 9 of the 3-input AND TTL circuit 3, and the O-
Character multiplexing R excluding BLK period and character multiplexing half-brightness period
A signal is output. The output of pin 11 of the 2-input AND TTL circuit 2 and the output of pin 8 of the 3-input AND TTL circuit 3 are mixed via a resistor to form a character multiplexed R signal, and further mixed with an on-screen R signal. Connected to the circuit. FIG. 4 shows a waveform example of this signal.

Similarly, the G and B signals are processed in the same manner, connected to the subsequent circuit, switched to the television signal in the subsequent circuit, and displayed on the screen.

Effect of the Invention As described above, the on-screen mixing circuit of the present invention makes use of the advantage that a character multiplex signal and an on-screen signal coexist in the same device, which is an advantage of a television with a built-in character multiplex, and makes it possible to use a character multiplex signal at low cost. And an on-screen signal can be mixed, which is particularly advantageous in terms of cost and practicality.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of an on-screen mixing circuit according to one embodiment of the present invention, FIG. 2 is a signal waveform diagram for explaining the operation of FIG. 1, and FIG. FIG. 4 is a circuit diagram of a conventional circuit for processing a character multiplexed signal. 1, 2, ... 2 input AND TTL circuit, 3 ... 3 input AND TTL
Circuit 4, transistor.

Claims (1)

(57) [Claims] 1. A first two-input AND TTL circuit for receiving on-screen R, G, B signals and an on-screen blanking signal, shaping waveforms and outputting respective signals, and character multiplexing R, G, A second two-input AN that receives the B signal and the on-screen blanking signal whose polarity is inverted.
A D TTL circuit, a three-input AND TTL circuit that receives the character multiplexed R, G, B signals, an on-screen blanking signal with inverted polarity, and a character multiplexed half-brightness signal;
R, G, B output signals of the two-input AND TTL circuit of
An on-screen mixing circuit comprising an output circuit that outputs each output signal of an input AND TTL circuit and a three-input AND TTL circuit by resistance coupling.