JP2001078053A - Drive signal generator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily exclude the influence of various noises, to prevent the occurrence of, for example, horizontal jitters, and to prevent the frequency of a horizontal drive signal from being quickly changed even in the case of the quick frequency changes of an external noise or an input synchronizing pulse. SOLUTION: An H synchronizing frequency measuring circuit 2 measures the frequency of an input H synchronizing pulses. A time window generator 4 generates a time window having a period corresponding to the frequency of the input H synchronizing pulses. An input H synchronizing pulse discrimination circuit 3 discriminates whether the input H synchronizing pulses exist within the time window; if they do not exist within the time window, a pseudo pulse generation circuit 6 is controlled so as to generate a pseudo pulse within the time window. The circuit 3 controls a selection switch 5 so that it selects only the input H synchronizing pulses existing within the time window and the false pulse. A horizontal drive waveform generation circuit 7 uses the pulse outputted from the selection switch to generate a horizontal drive waveform.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive signal generator for generating a horizontal drive signal supplied to, for example, a monitor.

[0002]

2. Description of the Related Art Conventionally, most horizontal drive signal generators for generating a horizontal drive signal to be supplied to a monitor device have a built-in PLL (Phase-Locked Loop) circuit.
The PLL circuit synchronizes the internal pulse with the input sync pulse, and generates a horizontal drive signal (horizontal drive waveform) based on the internal pulse.

Thus, the conventional horizontal drive signal generator prevents the internal pulse from abruptly changing, for example, even when the input sync pulse is disturbed or when the frequency changes abruptly.

[0004]

However, in the case of the above-described horizontal drive signal generator using the conventional PLL circuit, various noises such as power supply noises are generated by the above-mentioned P drive circuit.
It affects the operation of the LL circuit, and the horizontal drive signal is also affected by these various noises. As a result, there is a problem that horizontal jitter occurs on the screen of the monitor device.

[0005] It is very difficult to remove these noises, and therefore, great efforts have been conventionally required to remove them.

Further, in the conventional horizontal drive signal generator, the internal pulse is not changed rapidly even if the input sync pulse is disturbed or the frequency is changed suddenly by using a PLL circuit. Depending on the design of the device, the oscillation frequency of the internal pulse may suddenly change due to external noise or a change in the frequency of the input sink. When the oscillation frequency of the internal pulse suddenly changes in this way, the frequency of the horizontal drive signal output from the horizontal drive signal generator also suddenly changes accordingly. In this case, in the monitor device, the horizontal output transistor may be destroyed.

Accordingly, the present invention has been made in view of such a situation, and makes it possible to easily remove the influence of various noises, for example, to prevent the occurrence of horizontal jitter, and to further prevent external noise and noise. Even if there is a sudden change in the frequency of the input sync pulse, it is possible to prevent a situation in which the frequency of the output horizontal drive signal changes abruptly.
It is an object to provide a drive signal generator.

[0008]

According to the present invention, there is provided a drive signal generating apparatus comprising: a frequency measuring means for measuring a frequency of an input sync pulse; and a time window generating means for generating a time window having a predetermined period according to the measured frequency. Means for determining whether or not an input sync pulse is present in the time window; and, when no input sync pulse is present in the time window, a pseudo pulse in a time window in which the input sync pulse is not present. Pseudo-pulse generating means for generating, a selection means for selecting only an input sync pulse existing in the time window and a pseudo pulse generated in a time window in which the input sync pulse does not exist, and a pseudo-pulse output from the selection means. The above-mentioned problem is solved by having drive waveform generating means for generating a predetermined drive waveform using the generated pulse.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows a schematic configuration of a horizontal drive signal generating circuit according to an embodiment of the present invention.

In FIG. 1, a horizontal sync pulse (hereinafter, appropriately referred to as H sync, H sync pulse) is input to an input terminal 1. This input H sync is input to the H sync frequency measurement circuit 2 and the input H sync determination circuit 3.

The H sync frequency measuring circuit 2 measures the frequency of the input H sync, and sends the measured frequency information to the input H sync determining circuit 3.

The input H sync determination circuit 3 includes a time window generator 4
The time window generator 4 operates an internal counter (not shown) according to the frequency information supplied from the H-sync frequency measurement circuit 2 to obtain a period T (μ) as shown in FIG.
S) Generate a time window W of ± a (μS). 2A shows a pulse of an input H sink, and FIG. 2B shows an enlarged view of a circle E in FIG. 2A. The input H sink determination circuit 3 determines whether the state of the input H sink supplied from the input terminal 1 is stable using the time window W generated by the time window generator 4.

That is, in the input H sync determination circuit 3,
As shown in FIG. 2B, for example, the (n + 1) th input H
When the sync (n + 1th H sync pulse HPn + 1) is 1
The previous n-th input sync (n-th H sync pulse H
If the input H sink is within a time window W separated by the period T (μs) ± a (μs) from Pn), it is determined that the input H sink at this time is stable, and the stable input H
The operation of sending the sync to the horizontal drive waveform generation circuit 7 via the switched terminal 5A of the selection switch 5 is repeated for each pulse of each H sync.

At this time, the horizontal drive waveform generating circuit 7
Outputs a horizontal drive waveform as shown in FIG. 2C based on the stable input H sink supplied via the switched terminal 5A of the selection switch 5. The phase difference PD and duty DT of the horizontal drive waveform
Is controlled by an external analog adding circuit (not shown). The horizontal drive waveform output from the horizontal drive waveform generation circuit 7 is sent from the output terminal 8 to the monitor device as a horizontal drive signal.

As described above, when the H sink is stable, each pulse of the input H sink has the period T (μs).
Therefore, the state of the input H sink can be determined based on whether or not each pulse of the input H sink is within the time window W for every ± a (μs). It is.

However, when the H sink is not stable, for example, when one pulse is missing from the input H sink, or when the number of input H pulses increases and the pulse is positioned before the time window W, Generating a horizontal drive waveform based on the input H sync leads to a sudden change in the frequency of the horizontal drive signal, which is not preferable.

For this reason, in this embodiment, for example, FIG.
As shown in the figure, when the input H sink misses one pulse,
As shown in FIG. 4, when the number of input H pulses increases and the pulses are positioned before the time window W, the horizontal drive waveform is generated by the following process. FIGS. 3 and 4 are diagrams shown in the same manner as FIG. 2, and FIG. 3A and FIG. 4A show pulses of the input H sink, and FIG. 4B are enlarged views of the circle E in FIGS. 3A and 4A, respectively, and FIGS. 3C and 4C show output horizontal drive waveforms, respectively. ing.

First, for example, assuming that one pulse is missing from the input H sink, the input H sink determination circuit 3 determines that the H which is normal up to the n-th one as shown in FIGS. 3A and 3B. The sync is, for example, 1 at the portion corresponding to the (n + 1) th.
As a result of the missing pulse, the pulse of the input H sink does not exist in the time window Wn + 1 of the period T (μs) ± a (μs) corresponding to the position of the (n + 1) th H sync pulse. In the example of FIG. 3 (B), when it is confirmed that the H sync pulse that should be present as the (n + 1) th pulse does not exist in the time window Wn + 1, "H sync is abnormal" immediately
(Determined at the timing of T (μs) ± a (μs) + α), and outputs control signals to the pseudo pulse generation circuit 6 and the selection switch 5, respectively.

The pseudo-pulse generation circuit 6 which has received the control signal from the input H-sync determination circuit 3 immediately generates the H-sync pseudo pulse Qhp as shown in FIG. The pseudo pulse Qhp is sent to the switched terminal 5B of the selection switch 5. The selection switch 5 at this time is
Switching to the switched terminal 5B side is performed by the control signal from the input H sync determination circuit 3; therefore, the pseudo pulse Qhp from the pseudo pulse generation circuit 6 is sent to the horizontal drive waveform generation circuit 7. become.

In the case of the example of FIG. 3, the period of the next (n + 2) th H sync pulse HPn + 2 is T (μs) ±
Since it exists within the time window Wn + 2 of a (μs), the input sync determination circuit 3 determines that the input H sink is normally present.

The horizontal drive waveform generating circuit 7 uses a normal input H sink excluding the portion where the one pulse is missing and the pseudo pulse Qhp generated in the portion where the pulse is missing.
A horizontal drive waveform as shown in FIG. The horizontal drive waveform output from the horizontal drive waveform generation circuit 7 is sent from the output terminal 8 to the monitor device as a horizontal drive signal.

Next, when the number of input H pulses increases, the time window W
As shown in FIGS. 4A and 4B, the input H-sync determination circuit 3 determines, for example, that the pulse is located before the Nth H-sync pulse HPn + 1.
Time window W of period T (μs) ± a (μs) corresponding to position
When it is confirmed that there is an extra pulse HPe before n + 1, it is immediately determined that “H sync has an abnormality”,
A control signal is output to the selection switch 5.

At this time, the selection switch 5 is switched to the switched terminal 5B by a control signal from the input H sync determination circuit 3. However, in this case, since no pulse is generated from the pseudo pulse generation circuit 6, the extra pulse HPe is not input to the horizontal drive waveform generation circuit 7.

After that, the input H-sync determining circuit 3 uses the time windows Wn + 1, Wn + 2,. The presence / absence is determined, and if there is no abnormality, the respective H sinks are made normal, and the selection switch 5 is switched to the switched terminal 5A side.

Thus, the horizontal drive waveform generating circuit 7
Are normal input H sinks (pulses HPn, HPn + 1, HPn + 2...) From which the above-mentioned extra pulse HPe has been removed.
Only will be sent.

The horizontal drive waveform generating circuit uses a normal input H sink (pulses HPn, HPn + 1, HPn + 2...) After the extra pulse HPe is removed.
A horizontal drive waveform as shown in FIG. The horizontal drive waveform output from the horizontal drive waveform generation circuit 7 is sent from the output terminal 8 to the monitor device as a horizontal drive signal.

In the above description, the case where the frequency of the input H sink is constant (hereinafter, referred to as a constant frequency mode) is taken as an example, but the input H sink is shifted from the frequency f (Hz) to the frequency f + b (Hz). ),
The horizontal drive signal generator of the present embodiment operates as follows.

When the input H sink is switched from the frequency f (Hz) to the frequency f + b (Hz) and the generation cycle of the H sync pulse is changed, the H is set within the time window W of the period T (μs) ± a (μs). Since there are no sync pulses,
The input H-sink determination circuit 3 determines that "H-sync is abnormal", switches the selection switch 5 to the switched terminal 5B side, and generates the above-described pseudo pulse Qhp from the pseudo pulse generation circuit 6. Further, when the input H sink is switched from the frequency f (Hz) to the frequency f + b (Hz), the H sink does not exist in the next time window W after it is determined that “the H sync is abnormal”. Therefore, the input H-sink determination circuit 3 continues to determine that “the H-sync is abnormal”, and also maintains the control of the selection switch 5 on the switched terminal 5B side. Is controlled so as to continuously generate the pseudo pulse Qhp.

As described above, when the determination of “H sync is abnormal” is continued over a plurality of time window cycles (at least two cycles), the operation mode of the input H sink determination circuit 3 is as described above. The mode shifts from the constant frequency mode to the frequency switching mode.

When the mode shifts to the frequency switching mode, the input H sync determination circuit 3 determines the frequency f (H) received from the H sync frequency measurement circuit 2 in the constant frequency mode.
Based on the frequency information corresponding to z), the pseudo pulse generation circuit 5 is controlled so as to continuously generate the pseudo pulse Qhp having the frequency f (Hz).

On the other hand, the H-sync frequency measuring circuit 2 measures the frequency after the frequency is switched from f (Hz) to f + b (Hz), and measures the input H-sync after the frequency switching. At the time when the frequency is stabilized, a flag indicating that the input H sink is stabilized is set and sent to the input H sink determination circuit 3, and thereafter, frequency information corresponding to f + b (Hz) of the input H sink after the frequency switching is performed. It is sent to the input H sync determination circuit 3.

The input H-sink determining circuit 3 which has received the flag indicating the stability of the input H-sync and the frequency information of the input H-sync after the frequency switching controls the pseudo-pulse generating circuit 6 to generate the pseudo-pulse Qhp. The frequency is gradually approached from the frequency f (Hz) before the frequency switching to the frequency f + b (Hz) after the frequency switching,
Finally, the generation frequency of the pseudo pulse Qhp becomes the frequency f + b
(Hz).

Next, the input H-sink determination circuit 3 outputs the generated frequency f + b (Hz) from the pseudo pulse generation circuit 6.
In the state where the pseudo pulse Qhp is generated, a time window is generated in the same manner as described above with a cycle corresponding to the frequency f + b (Hz), and whether or not the pulse of the input H sink exists in the continuous N time windows When it is determined that there is a pulse of the input H sink in each of the N consecutive time windows, the selection switch 5 is switched to the switched terminal 5A side, and the pseudo pulse generation circuit 6 Is controlled to stop the pseudo pulse generation operation of.

As described above, according to the horizontal drive signal generator of the embodiment of the present invention, the operation states of the system are determined when the input H sink is stable, when the input H sink is abnormal, and when the frequency is switched. Thinking in three patterns,
By realizing the optimum operation according to each pattern, the amount of horizontal jitter can be reduced as compared with the device using the conventional PLL circuit, and therefore, the most experience is needed in the electric circuit design of the display monitor. By controlling the waveform of the horizontal drive signal using an input H-sync or pseudo pulse, it is possible to reduce the number of steps required to study the jitter, and to prevent the problem that the frequency of the horizontal drive signal waveform changes rapidly. I am holding it down.

[0036]

As is apparent from the above description, the drive signal generating apparatus of the present invention generates a time window corresponding to the frequency of an input sync pulse, and when the input sync pulse does not exist within the time window. By generating a pseudo pulse in the time window, and generating a predetermined drive waveform using only the input sync pulse existing in the time window and the pseudo pulse generated in the time window, various noises are generated. Can be easily removed to prevent, for example, the occurrence of horizontal jitter.Furthermore, even if there is external noise or a sudden change in the frequency of the input sync pulse, the frequency of the output horizontal drive signal will suddenly increase. It is possible to prevent the occurrence of a changing situation.

[Brief description of the drawings]

FIG. 1 is a block circuit diagram showing a schematic configuration of a horizontal drive signal generator according to an embodiment of the present invention.

FIG. 2 is a diagram used to explain the operation of the horizontal drive signal generator according to the present embodiment when the state of the input H sink is stable;

FIG. 3 shows an example in which the state of the input H sink becomes abnormal.
FIG. 7 is a diagram used to explain the operation of the horizontal drive signal generation device of the present embodiment when one pulse is missing from the sync.

FIG. 4 shows an example in which the state of the input H sink becomes abnormal.
FIG. 9 is a diagram used to explain the operation of the horizontal drive signal generation device according to the present embodiment when an extra sync pulse is generated.

[Explanation of symbols]

1 input terminal, 2 H sink frequency measurement circuit, 3
Input H sync judgment circuit, 4 time window generator, 5 selection switch, 6 pseudo pulse generation circuit, 7 horizontal drive waveform generation circuit, 8 output terminals

Claims (2)

[Claims] 1. A frequency measuring means for measuring a frequency of an input sync pulse; a time window generating means for generating a time window having a predetermined period according to the measured frequency; and an input sync pulse existing in the time window. Determination means for determining whether or not to perform the processing; and when there is no input sync pulse in the time window, pseudo pulse generation means for generating a pseudo pulse in a time window in which the input sync pulse does not exist; Selecting means for selecting only an input sync pulse existing in the input signal and a pseudo pulse generated in a time window in which the input sync pulse does not exist; and a drive for generating a predetermined drive waveform using the pulse output from the selecting means. A drive signal generator comprising a waveform generator. 2. When the frequency of the input sync pulse changes, the pseudo pulse generation means continuously generates the pseudo pulse at a frequency corresponding to the frequency before the change, and When only the pseudo pulse is selected and the frequency after the change is detected to be stable at the frequency measurement frequency, the frequency of the pseudo pulse generated by the pseudo pulse generating means is changed from the frequency before the change to the frequency after the change. And the determination means determines whether or not the input sync pulse after the change of the frequency exists within a time window generated according to the frequency after the change, When it is determined in the time window generated according to the frequency after the change that the input sync pulse after the change of the frequency exists continuously plural times, -Option drive signal generator of claim 1, wherein the switching input sync pulse after the above-mentioned frequency is stable from the pseudo pulse.