JPH06141203A - Signal processor - Google Patents

Abstract

PURPOSE:To always stably operate a signal processing system and to switch image erasure and image display smoothly by switching by changing a control voltage to feedback control when a synchronizing signal is transferred from 'absence' to 'presence'. CONSTITUTION:A signal HD or VD is inputted to a discrimination circuit 15, and the circuit 15 outputs 'H' when the synchronizing signal is inputted, and 'L' when no synchronizing signal is inputted. When 'H' is outputted, a control circuit 16 outputs a signal 'H' to control a switch circuit 12 to a reference voltage Vo side, and a control circuit 17 outputs the signal 'H' to control a switch circuit 14 to a feedback loop side. At this time, the control voltage VL is outputted to an amplitude control terminal, and the feedback control can be stably performed, and a conversion circuit 11 per-forms the level conversion of the voltage V of a contrast volume to a voltage VR when a feedback loop is operated normally. As a result, switching to the feedback control can be performed by changing the control voltage gradually when a state where no synchronizing signal exists is transferred to a state when it exists.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal processing device in a video signal processing device of a color television receiver.

[0002]

2. Description of the Related Art As a conventional signal processing apparatus for a television receiver, there is, for example, a signal processing apparatus as shown in the block diagram of FIG. In FIG. 3, 31 is a superimposing circuit for adding a control pulse to the video signal, 32 is a control circuit for controlling the amplitude of the video signal and a DC reproduction value by the control pulse, 33 is an amplifying circuit for generating a drive signal of the CRT, Reference numeral 34 is a generation circuit that generates a control signal for the control circuit 32.

The superimposing circuit 31 superimposes control pulses 1 and 2 for controlling the signal amplitude and the direct current reproduction value on the video signal in the blanking period. As a result, the output of the superposition circuit 31 becomes as shown in FIG. The video signal on which the control pulse is superimposed is input to the control circuit 32. Then, the amplitude is adjusted and the direct current is reproduced, and further amplified by the amplifier circuit 33 so as to become a CRT drive signal.

The output of the amplifier circuit 33 is also input to the generation circuit 34. The generation circuit 34 detects the control pulse superposed by the superposition circuit 31 from the input video signal. The amplitude of the control pulse 1 (that is, the amplitude from the pedestal level) is detected, and the gain variation is monitored by comparison with the reference signal. The peak value of the control pulse 2 is detected,
Fluctuations in DC regeneration are monitored by comparison with a reference signal.
Then, control signals for suppressing the fluctuation are generated in the generation circuit 34, and these control signals are generated by the control circuit 3.
2 is input to the amplitude control terminal and the DC reproduction value control terminal to control the amplitude and the DC reproduction value of the video signal.

The control pulse 1 is controlled by the feedback loop of the control circuit 32, the amplification circuit 33, and the generation circuit 34 so as to always have the same amplitude as the reference signal. 5A shows the output of the control circuit 32 in the stable state, FIG. 5B shows the output of the control circuit 32 at the moment when the level of the control pulse 1 is lowered from the stable state, and FIG. Shows the output of the control circuit 32 which is in a stable state again. In the feedback loop, if the amplitude of the control pulse 1 superimposed by the superimposing circuit 31 is reduced as shown in FIGS. 5A to 5B, the lowered amplitude of the control pulse 1 is the same as that in FIG. 5A. Control to become.

As a result, the amplitude of the entire video signal becomes large. On the contrary, if the level of the control pulse 1 for superimposing in the superimposing circuit 31 is raised, the amplitude of the entire video signal can be reduced. As described above, the contrast can be controlled by changing the level of the control pulse 1.

The peak value of the control pulse 2 is clamped by the feedback loop of the control circuit 32, the amplification circuit 33, and the generation circuit 34 so that it always has the same DC value as the reference signal.
At this time, the clamp level should be the cutoff level. Brightness control can be performed by changing the level at which the superimposing circuit 31 superimposes.

[0008]

However, in the conventional structure as described above, the control pulses 1 and 2 are generally synchronized with the blanking period of the video signal, and therefore are generated from the synchronization signal. Therefore, when the synchronizing signal is not input, the control pulses 1 and 2 are not created and no signal is superimposed during the blanking period. Therefore, the amplitude of the control pulse 1 detected by the signal generation circuit 34 is 0. Therefore, as described above, the operation of the feedback loop works to make the amplitude of the video signal infinite (actually the maximum amplitude limited by the power supply voltage) and restore the amplitude of the control pulse 1.

As a result, the contrast control in the control circuit 32 works so that the video signal has the maximum amplitude at the moment when the synchronizing signal is input. As a result, the CRT will shine with high brightness.

In view of the above points, the present invention turns on the main power supply when a control pulse for signal processing is added during the blanking period.
Even when the video signal or sync signal is input from the outside, that is, when the feedback loop begins to operate, the signal processing system always operates stably, and smooth image switching and image switching are possible. An object is to provide a signal processing device for a television receiver.

[0011]

According to the present invention, there is provided a conversion circuit for converting a control voltage, a first switch circuit for switching between an output voltage of the conversion circuit and a reference voltage, and charging by an output voltage of the first switch circuit. Charging circuit, a second switch circuit for switching between the output voltage of the charging circuit and the control voltage in the feedback loop and outputting to the control terminal, a discrimination circuit for detecting the presence or absence of a synchronization signal, the output of the discrimination circuit and charging A first control circuit for controlling the first switch circuit by the output of the circuit, and a second control circuit for controlling the second switch circuit by the output of the discrimination circuit and the output of the charging circuit. is there.

[0012]

According to the present invention, the feedback control loop is cut off when there is no synchronizing signal and the control signal is supplied at a constant voltage to stabilize the control, and when the synchronizing signal is restored, the charging circuit gradually operates. Since the control level changes to
The control operation is stable even when there is no synchronization signal, and smooth switching can be performed without displaying an abnormal image in the transition period even when returning.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of a signal processing device for controlling the amplitude of a video signal according to an embodiment of the present invention.

In FIG. 1, 11 is a conversion circuit for converting the voltage of the contrast volume, 12 is a first switch circuit for switching between the output voltage of the conversion circuit 11 and the reference voltage, and 13 is an output of the first switch circuit 12. A charging circuit that is charged by a voltage, 14 is a second switch circuit that switches between the output voltage of the charging circuit 13 and the control voltage in the feedback loop, 15 is a determination circuit that detects the presence or absence of a synchronization signal, and 16 is the output of the determination circuit 15. And a first control circuit for controlling the first switch circuit 12 by the output of the charging circuit 13, and a second control circuit 17 for controlling the second switch circuit 14 by the output of the discrimination circuit 15 and the output of the charging circuit 13. This is a control circuit, and the output of the second switch circuit 14 is connected to the amplitude control terminal and controls the amplitude of the video signal.

In addition, this embodiment uses the generator circuit 3 in the conventional example.
4 and the control circuit 32, the control voltage in the feedback loop in FIG. 1 is the output voltage of the generation circuit 34 in FIG. 3, and the amplitude control terminal in FIG. 1 is the control circuit in FIG. Three
2 is an amplitude control terminal.

The operation of the signal processing apparatus of this embodiment constructed as above will be described below.

First, the case where there is a sync signal and the feedback loop operates normally will be described. The horizontal synchronizing signal (HD) or the vertical synchronizing signal (VD) is input to the input of the determination circuit 15. For example, the determination circuit 15 outputs the H level when the synchronization signal is input, and outputs the L level when the synchronization signal is not input.

When the feedback loop is operating normally and the discrimination circuit 15 outputs the H level, the first control circuit 1
Reference numeral 6 outputs a signal for controlling the first switch circuit 12 to the reference voltage side, for example, an H level. The L level is a signal for controlling the first switch circuit 12 to the conversion circuit 11 side.

Similarly, when the feedback loop is operating normally and the discrimination circuit 15 outputs the H level, the second control circuit 17 controls the second switch circuit 14 to the feedback loop side, for example, H signal. Output level. The L level is a signal for controlling the second switch circuit 14 to the charging circuit 13 side.

At this time, the control voltage V _L in the feedback loop is input to the amplitude control terminal through the second switch circuit 14, and stable feedback control is performed. In addition, the conversion circuit 11
Is outputting to level conversion so that the voltage V of the contrast volume V _R. It is controlled so that V _L = V _R when the feedback loop is operating normally. Further, the charging circuit 13 is charged with the reference voltage V ₀ through the first switch circuit 12. It is assumed that the reference voltage V ₀ is a voltage that makes the contrast minimum, that is, the amplitude of the video signal to 0 when input to the amplitude control terminal, for example.

Next, the output of the discrimination circuit 15 changes from H level to L level.
The operation when the level is changed or when the L level is changed to the H level, that is, when the presence or absence of the synchronization signal is changed will be described.

FIG. 2 is a timing chart when the output of the discrimination circuit 15 changes from the H level to the L level, and conversely when it changes from the L level to the H level. (A) is a timing chart of the determination circuit 15, (B) is a timing chart of the second control circuit 17, (C) is a timing chart of the first control circuit 16, and (D) is a charging circuit 13.
Is a change in the control voltage in the feedback loop, and (F) is another timing chart of the first control circuit 16.

Until the time t ₁ , the synchronizing signal is always present, so that the discriminating circuit 15 constantly outputs the H level. By the output signal of the discrimination circuit 15, both the first control circuit 16 and the second control circuit 17 output H level until time t ₁ .

However, when the output of the discrimination circuit 15 changes from the H level to the L level at the time t ₁ of FIG. 2A, the output of the second control circuit 17 becomes the H level as shown in FIG. 2B. To L level. The output of the discrimination circuit 15 is H.
Even if the level changes from the L level to the L level, the output voltage of the charging circuit 13 remains in the V ₀ state, so that the output level of the first control circuit 16 does not change and maintains the H level. Therefore, the first switch circuit 12 holds the reference voltage V ₀ side, and the second switch circuit 14 switches to the charging circuit 13 side.

As a result, the charging circuit 13 is connected to the amplitude control terminal.
Since the voltage V ₀ charged in is input, the amplitude of the video signal becomes zero.

At this time, the control voltage in the feedback loop is at the voltage level V∞ that makes the amplitude of the video signal infinite.

Next, when the output of the discrimination circuit 15 changes from the L level to the H level at time t _{2 in} FIG.
That is, the case where the synchronization signal is input will be described.

The output of the first control circuit 16 is the charging circuit 13
When the output voltage of V2 slightly exceeds V ₀ , it changes from H level to L level at time t ₂ as shown in FIG. The output voltage of the charging circuit 13 is V
Since it does not change until it reaches _R , it does not change at time t ₂ and maintains the L level.

Therefore, the first switch circuit 12 switches to the conversion circuit 11 side, and the second switch circuit 14 holds the charging circuit 13 side.

As a result, the charging circuit 13 is charged with the output voltage V _R of the conversion circuit 11, and the charging circuit 13 is connected to the amplitude control terminal.
Voltage change, that is, the control voltage V with an amplitude of 0 as shown in FIG.
₀ control voltage changes V _R is inputted from. At this time, the control voltage V _L in the feedback loop changes from the control voltage V ∞, which makes the amplitude infinite, to V _R , as shown in FIG.

Next, at time t ₃ in FIG. 2A, time t
_{When a} sufficient time T has passed from ₂ and the charging voltage of the charging circuit 13 reaches V _R , the charging circuit 13 causes the first control circuit 16,
A control signal for changing the output from the L level to the H level is sent to the second control circuit 17. The outputs of the first control circuit 16 and the second control circuit 17 change from the L level to the H level by this control signal.

As a result, the first switch circuit 12 is switched to the reference voltage side and the second switch circuit 14 is switched to the feedback loop side.

When the second switch circuit 14 is switched from the charging circuit 13 side to the feedback loop side, the control voltage V _L in the feedback loop is also V _R , so that the amplitude of the video signal does not change and the smooth switching is performed. Is done.

As described above, according to this embodiment, when there is no synchronizing signal, the feedback loop is opened and controlled by the reference voltage, and when there is no synchronizing signal, the control voltage is gradually changed. Since the feedback control is switched to the feedback control, the smooth switching can be performed without outputting the abnormal image in the transition period even when the synchronization signal is input from the state where the synchronization signal is not input. Also, the appearance time of the image can be adjusted by adjusting the time constant of the charging circuit 13 and changing the time T.

Although the amplitude control of the video signal has been described in this embodiment, the present invention can be applied to other control, for example, the control of the direct current reproduction value. Further, after the time T has passed, the first control circuit 16 and the second control circuit 17 are simultaneously switched to the H level. However, as shown in FIG. 2 (F), the second control circuit 17 is at the H level. The first control circuit 16 may be controlled so as to switch to the H level after switching to.

[0036]

As described above, according to the present invention, smooth switching can be performed without outputting an abnormal image in the transition period even when the state where the synchronizing signal is input is changed to the state where the synchronizing signal is input. It is possible and its practical effect is great.

[Brief description of drawings]

FIG. 1 is a block diagram of a signal processing device for controlling an amplitude of a video signal according to a first embodiment of the present invention.

FIG. 2 is an operation waveform diagram of the embodiment.

FIG. 3 is a block diagram of a conventional example.

FIG. 4 is an output waveform diagram of the superposition circuit.

[Figure 5] Waveform diagram when contrast is increased

[Explanation of symbols]

 11 Conversion Circuit 12 First Switch Circuit 13 Charging Circuit 14 Second Switch Circuit 15 Discrimination Circuit 16 First Control Circuit 17 Second Control Circuit

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Hiroshi Masuda 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (1)

[Claims] 1. A conversion circuit for converting a control voltage, a first switch circuit for switching between an output of the conversion circuit and a reference voltage, a charging circuit charged by an output of the first switch circuit, and the charging. A second switch circuit for switching between the output voltage of the circuit and the control voltage in the feedback loop;
A discriminating circuit that detects the presence or absence of a synchronization signal, a first control circuit that controls the first switch circuit by the output of the discriminating circuit and the output of the charging circuit, and an output of the discriminating circuit and the charging circuit. A second control circuit for controlling the second switch circuit according to the output, and smoothly changing the operation of the feedback loop when the presence / absence state of the sync signal changes abruptly. A characteristic signal processing device.