JPH02290373A - Noise reduction circuit - Google Patents

Abstract

PURPOSE:To eliminate the deviation of display position of a character by providing a means eliminating noise superimposed on a horizontal synchronizing pulse to an output control circuit corresponding to a TV display pattern. CONSTITUTION:A timing generating circuit 1 generates a gate signal 102 regulating the passing timing of a pulse (1) having a slightly shorter period than a reference period of a horizontal synchronizing pulse 1 forming a horizontal synchronizing signal 101 inputted from a terminal 51 and inputs the signal to a gate circuit 2. The circuit 2 outputs a horizontal synchronizing signal 103 including only a horizontal synchronizing pulse (2) corresponding to the passing timing of the signal 102 and sends it to the circuit 1 and an output control circuit 3. The circuit 1 applies the control in the timing of the pulse (2) to set the output initial state of the signal 102 newly on each occasion and the signal 102 is outputted to the circuit 2 as a gate signal in a timing in matching with the timing of the pulse (1). Thus, the pulse (2) forming the signal 103 outputted from the circuit 2 is a signal in matching with the passing timing of the signal 102 at all times and inputted to the circuit 3.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a noise removal circuit, and particularly to a semiconductor integrated circuit for on-screen character display that displays characters such as time, channel, number, etc. on a television display screen. , a noise removal circuit that removes noise from a horizontal synchronization input signal is developed.

[Prior Art] Conventionally, in this type of semiconductor integrated circuit, as shown in an example block diagram in FIG. Output and fil that control the display position of characters such as time, channel number, etc. on the John display screen
Generally, the output signal is input directly to the output control circuit 3, and the output signal from the output control circuit 3 is sent to the television display section. [Problems to be Solved by the Invention] In the conventional semiconductor integrated circuit described above, the horizontal synchronization input signal input to the output WII control circuit for television display is directly input to the output control circuit. Therefore, if noise introduced by a weak electric field or other electrical products etc. intervenes in the horizontal synchronization signal, the output control circuit is operated by the water synchronization pulse with the superimposed noise, which causes the noise on the TV display screen to The disadvantage is that the character display position is shifted.

[Means to solve the problem]

The noise removal circuit of the present invention is an output control circuit composed of a semiconductor integrated circuit for displaying predetermined characters on a television display screen, and in which a predetermined gate signal is input to a stage before the output control circuit. a gate circuit that regulates the passage timing of a horizontal synchronizing pulse signal (1) that forms a horizontal synchronizing input signal, outputs a horizontal synchronizing pulse signal (2), and sends it to the output control circuit; 2) and input the horizontal sync pulse signal (1).
and a timing generation circuit that generates the gate signal that matches the timing of.

〔Example〕

Next, the present invention will be explained with reference to the drawings. FIG. 1 is a block diagram of one embodiment of the present invention. As shown in FIG. 1, this embodiment includes a timing generation circuit 1 and a gate circuit 2 corresponding to an output control circuit 3. As shown in FIG.

In FIG. 1, the timing generation circuit 1 has a cycle slightly shorter than the reference cycle of the horizontal synchronizing pulse (1) forming the horizontal synchronizing input signal 101 inputted from the terminal 5l, and the horizontal synchronizing pulse (1) ) is generated and input to the gate circuit 2. In the gate circuit 2, the horizontal synchronization pulse (1) forming the horizontal synchronization input signal 101 inputted from the terminal 51 is controlled by the gate signal 102 inputted from the timing generation circuit 1, and is controlled by the passage timing of the gate signal 102. A horizontal synchronization signal 103 containing only the corresponding horizontal synchronization pulse (2) is output and sent to the timing generation circuit 1 and the output control circuit 3.

In the timing generation circuit 1, by inputting the horizontal synchronization pulse (2) sent from the gate circuit 2, the output initial state of the gate signal 102 is controlled by the timing of the horizontal synchronization pulse (2), and the output initial state of the gate signal 102 is changed each time. The newly set gate signal 102 is output to the gate circuit 2 as a gate signal whose timing matches the timing of the horizontal synchronizing pulse (1). Therefore, the horizontal synchronizing pulse (
2) is always output at the timing of passage of the gate signal 102 and input to the output control circuit 3.

FIGS. 2(a), (b), and (c) respectively show an example of the operation timing diagram of the horizontal synchronization input signal 101, the gate signal 102, and the horizontal synchronization signal 103.
The noise contained in the horizontal synchronization pulse (1) in the horizontal synchronization input signal 101 in FIG. 2(a) is removed by the gate signal 102 shown in FIG. 2(b), and the horizontal synchronization pulse (
2) is input to the output control circuit 3 together with the data signal 104 in a noise-free state.

That is, the noise removal circuit constituted by the timing generation circuit 1 and the gate circuit 2 completely removes noise that does not match the timing of the horizontal synchronization pulse among the noise contained in the horizontal synchronization input signal 101 input from the terminal 5l. be done.

〔Effect of the invention〕

As described above in detail, the present invention is applied to an output control circuit corresponding to a television display screen, and eliminates noise superimposed on the horizontal synchronizing pulse inputted to the output control circuit without compromising the noise. By effectively removing the noise without using a circuit, it is possible to remove deviations in the display position of characters, etc. due to noise on the television display screen.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the present invention, and FIG.
), (b) and (c) are operation timing diagrams of a horizontal synchronization input signal, a gate signal, and a horizontal synchronization signal, respectively, in the above embodiment, and FIG. 3 is a block diagram of a conventional output control circuit. In the figure, 1...timing generation circuit, 2...
...Gate circuit, 3-...Output control circuit. Agent Patent Attorney Uchihara Old Shoulder Figure/01 Bian? figure. 3 Earth Phantom Treasures] Aim T times Z each million J figure

Claims (1)

[Claims] In an output control circuit composed of a semiconductor integrated circuit for displaying predetermined characters on a television display screen, a predetermined gate signal is input to a preceding stage of the output control circuit to form a horizontal synchronization input signal. a gate circuit that regulates the passage timing of the horizontal synchronizing pulse signal (1) and outputs the horizontal synchronizing pulse signal (2) and sends it to the output control circuit; A noise generation circuit comprising: a timing generation circuit that generates the gate signal that matches the timing of the horizontal synchronization pulse signal (1).