JP3287176B2 - Pulse generation circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pulse generation circuit for preventing a phenomenon in which color is delayed when a channel of a color television receiver is switched.

[0002]

2. Description of the Related Art In recent years, a high-definition television receiver has been demanded as a color television receiver becomes larger and more multifunctional. For example, in Japanese Patent Application Laid-Open No. 53-126212, a discomfort phenomenon at the time of channel switching is removed by superimposing a blanking pulse on a video signal at the time of selecting a channel or suppressing sound. As described above, a circuit for preventing an unpleasant phenomenon such as slow coloring of a color at the time of channel switching or the like is regarded as important.

Hereinafter, an example of the above-described conventional pulse generating circuit will be described with reference to the drawings. FIG. 3 shows a block diagram of a conventional pulse generating circuit. In FIG. 3, reference numeral 301 denotes a slice circuit, 302 denotes a video blanking circuit, and 303 denotes an SCP (sandcastle pulse).
Generating circuit, 304 is a fixed resistor, 305 is a diode element, 306 is a fixed resistor, 307 is a diode element, 30
8 is a fixed resistor, 309 is an FBP (flyback pulse) which becomes HIGH during a horizontal retrace period, 310 is an image for darkening an image output when a channel is switched or an external video input is switched, or the like. A blanking pulse 311 is a pulse for driving another integrated circuit or blanking a period necessary for another integrated circuit, and includes a burst gate period, a horizontal blanking period, a vertical blanking period, and the like. SCP (Sandcastle pulse) with information, 312 is SECAM demodulation circuit,
313 is a matrix circuit, 314 is a luminance signal input to the matrix circuit 313, 315 is an RGB signal which is an output signal of the matrix circuit 313, and 316 is the S signal.
A BY color difference signal 317, which is an output signal from the ECAM demodulation circuit 312, is an RY color difference signal, which is an output signal from the SECAM demodulation circuit 312.

The operation of the pulse generating circuit configured as described above will be described below. First, FBP
309 is a pulse having a waveform as shown in FIG.
In the normal state, the image blanking pulse 310 is
It is LOW as shown in FIG. These waveforms correspond to the fixed resistors 304, 306, 308 and the diode element 30.
As shown in FIG. 4C, the waveform input to the slice circuit 301 passes through the multiplexing circuit composed of 5, 307. The slice circuit 301 is a circuit that provides a slice voltage at a certain level and outputs HIGH when a signal higher than the slice level is input. The output waveform of this circuit is as shown in FIG. The video blanking circuit 302 is a circuit for blanking the horizontal retrace period of the RGB output signal 315 and the color difference output signals 316 and 317 with the input of FIG. The SCP generation circuit 303 receives the input shown in FIG. 4D and outputs an SCP as shown in FIG. 4E to the outside of the integrated circuit. This pulse is used as a driving pulse for an external integrated circuit that requires a clock, and is used to supply horizontal and vertical blanking pulses necessary for the SECAM demodulation circuit 312. The SECAM demodulation circuit 312 receives the SCP 311 shown in FIG. 5A, separates the vertical retrace period and the horizontal retrace period into the same, and generates pulses necessary for SECAM demodulation. And the SECAM demodulation circuit 312
Are output to a matrix circuit 313, and after being calculated with a luminance signal 314 and added with a video blanking pulse, are output as RGB output signals 315 to the outside of the integrated circuit.

[0005]

However, in the above-described configuration, when the screen is completely darkened (blanking an image) in order to eliminate an unpleasant phenomenon due to channel switching or the like, the side effect of slow color coloring is caused. Will occur. This will be described with reference to FIGS. 3, 4, and 5.

In order to eliminate an unpleasant phenomenon by channel switching or the like, an image blanking pulse 310 in FIG. 3 is set to HIGH as shown in FIG. At this time, the waveform input to the slice circuit 301 is as shown in FIG.
The output of 01 becomes HIGH at DC voltage. By inputting this waveform, the video blanking circuit 302
The output signal 315 can be blanked to make the screen black. However, the output waveform of the SCP generation circuit 303 is shown in FIG.
(J) or, as shown in FIG.
Will not be output.

When this pulse is input to the SECAM demodulation circuit 312, a circuit for separating the vertical retrace period and the horizontal retrace period in this circuit does not operate normally.
Pulses necessary for CAM demodulation cannot be created, and SECAM
The color demodulation circuit does not operate. Then, the channel switching is completed, and the video blanking pulse 310 becomes LOW.
When this happens, the SCP 311 returns to a normal waveform.
The SECAM color demodulation circuit of the AM demodulation circuit 312 starts operating normally.

That is, after the video blanking is completed,
Since color demodulation is not performed for a while, there is a problem that coloring of colors is slow when the screen is completely darkened at the time of channel switching.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and provides a pulse generation circuit for preventing a phenomenon in which coloring of colors is delayed when switching channels.

[0010]

In order to solve the above-mentioned problems , a pulse generating circuit according to the present invention comprises a video blanking period pulse and a video blanking period pulse.
A multiplexing circuit for multiplexing with an image blanking pulse;
Using the output signal of the multiplexing circuit as input and setting the first slice level
A first slice circuit having the first slice circuit,
A video blanking circuit to which an output signal is input;
The same signal or image as the signal input to one slice circuit
Only the image retrace period pulse is input and the first slice
A second slice with a second slice level different from the bell
And an output signal of the second slice circuit is input.
With a sandcastle pulse generation circuit
Wherein the output signal of the multiplexing circuit is
The first slice level and the second slice level in the
Different in the second slice level in the slice circuit.
To slice at two different slice levels
Or the output signal of the multiplexing circuit is
In one slice circuit, at the first slice level
Slicing and applying a video retrace period pulse to the second slice
The circuit is different from the first slice level in the circuit.
Slice at the second slice level
It is characterized by having .

[0011]

According to the present invention, it is possible to prevent a phenomenon in which coloring of color is slow at the time of channel switching or the like by the above-described configuration.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a pulse generating circuit according to an embodiment of the present invention will be described with reference to the drawings.

(Embodiment 1) FIG. 1 is a block diagram showing a pulse generating circuit according to a first embodiment of the present invention. FIG.
, Reference numeral 101 denotes a slice circuit, 102 denotes a slice circuit, 103 denotes an SCP (Sandcastle pulse) generation circuit, 104 denotes an SCP, 105 denotes an FBP (flyback pulse), 106 denotes a multiplexing circuit for multiplexing pulses,
07 is a video blanking pulse.

The operation of the pulse generating circuit configured as described above will be described below with reference to FIGS. First, the multiplexing circuit 106 includes the fixed resistor 30 shown in FIG.
4, 306, 308 and diode elements 305, 307
May have the same configuration as the circuit formed by the above.

FIG. 6A shows a multiplex circuit 1 in a normal state.
FIG. 6B shows an output waveform of the multiplexing circuit 106 in a state where the video is blanked. In each figure, there are two solid lines A and B, where A represents the slice level of the slice circuit 102 and B represents the slice level of the slice circuit 101. In the normal state, the output waveform of the slice circuit 101 is shown in FIG. 6C, the output waveform of the slice circuit 102 is also FIG. 6C, and the SCP 104 is shown in FIG. 6E.

Next, in the video blanking state, the output waveform of the slice circuit 101 is shown in FIG.
6D and FIG. 6E for the SCP 104. That is, since the SCP 104 does not change the waveform even when the video blanking is applied, the coloring is not slow at the time of channel switching or the like.

As described above, according to the present embodiment, by providing two circuits having different slice levels, it is possible to prevent a phenomenon that coloring is slow at the time of channel switching or the like.

(Embodiment 2) Hereinafter, a second embodiment of the present invention will be described with reference to the drawings. FIG. 2 is a block diagram showing a pulse generating circuit according to a second embodiment of the present invention. 2, reference numeral 201 denotes a slice circuit;
2 is a slice circuit, 203 is an SCP generation circuit, 204 is an SCP, 205 is a video blanking pulse, and 206 is F
BP and 207 are multiplex circuits for multiplexing pulses.

The operation of the pulse generating circuit configured as described above will be described below with reference to FIGS. First, the multiplexing circuit 207 includes the fixed resistor 30 shown in FIG.
4, 306, 308 and diode elements 305, 307
May have the same configuration as the circuit formed by the above. The FBP 20 input to the slice circuit 202
6 is independent of the video blanking pulse 205, the waveform does not change in any state, and is always the waveform of FIG. Therefore, the waveform output from the SCP generation circuit 203 is always the waveform shown in FIG. 6E, and the coloring is not slow when switching channels.

On the other hand, the video blanking pulse 205 is HIGH at the time of blanking, the output waveform of the multiplexing circuit 207 is a waveform as shown in FIG. 6B, and the slice level of the slice circuit 201 is as shown in FIG. Therefore, the output of the slice circuit 201 becomes HIGH, and the entire screen is blanked. The video blanking pulse 205 is LOW in the normal state, and the output waveform of the multiplexing circuit 207 has a waveform as shown in FIG. Since the slice level of the slice circuit 201 is that shown in FIG. 6B, the output of the slice circuit 201 is as shown in FIG. 6C, and the horizontal blanking period is in the blanking state.

As described above, according to this embodiment, by inputting the FBP pulse for SCP generation from another input terminal, it is possible to prevent a phenomenon in which the color is delayed at the time of channel switching or the like.

[0022]

As described above, according to the present invention, two circuits having different slice levels are provided, and an FBP pulse for SCP generation is inputted from another input terminal, so that color can be changed at the time of channel switching or the like. Can be prevented from being colored slowly.

[Brief description of the drawings]

FIG. 1 is a block diagram of a pulse generation circuit according to a first embodiment of the present invention;

FIG. 2 is a block diagram of a pulse generation circuit according to a second embodiment of the present invention;

FIG. 3 is a block diagram of a conventional pulse generation circuit.

FIG. 4 is a waveform diagram of a conventional pulse generation circuit.

FIG. 5 is a waveform diagram of a conventional pulse generation circuit.

FIG. 6 is a waveform diagram of a pulse generation circuit according to the first and second embodiments of the present invention.

DESCRIPTION OF SYMBOLS 101 slice circuit 102 slice circuit 103 SCP generation circuit 104 SCP 105 FBP 106 multiplex circuit 107 video blanking pulse 201 slice circuit 202 slice circuit 203 SCP generation circuit 204 SCP 205 video blanking pulse 206 FBP 207 multiplex circuit

Claims (2)

(57) [Claims] 1. A multiplexing circuit for multiplexing a video retrace period pulse and a video blanking pulse; a first slice circuit having an input signal from the multiplexing circuit as an input and having a first slice level ; Slice circuit output signal is input
A video blanking circuit is, the first signal and the same signal is input to slice circuit is input the first
A second slice circuit having a second slice level different from the slice level; and a sandcastle pulse generation circuit to which an output signal of the second slice circuit is input . 1 slice times
The first slice level and the second slice
2 different in the second slice level in the chair circuit.
A pulse generating circuit , wherein each of the slices is sliced at one of two slice levels . A multiplexing circuit for 2. A multiplexed the video blanking interval pulses and the video blanking pulse, a first slice circuit having a first slice level and an output signal of the multiplexing circuit, said first Slice circuit output signal is input
A video blanking circuit to be input and a second video signal having only a video retrace period pulse and different from the first slice level.
And a sandcastle pulse generation circuit to which an output signal of the second slice circuit is input, and an output signal of the multiplex circuit.
In the first slice circuit.
Level and slice the video retrace period pulse to the second
The slice circuit is different from the first slice level.
Slice at each of the second slice levels
Pulse generating circuit, characterized in that the the like.