JPH0875803A - Voltage fall detection trigger generation device - Google Patents

Abstract

PURPOSE: To make the response speed faster, and reduce influence of an external noise, so as to enable any voltage fall to be precisely detected by providing an AND circuit, etc., for outputting a logical product of a detection unit output. CONSTITUTION: The voltage level of an input waveform is adjusted by means of a waveform level adjuster 26 and then sent to detection units 28 and 30. The detection unit 28 generates a first output which reaches Hi or Lo level respectively when the positive direction voltage of the input waveform is smaller or greater than a first detection level. The detection unit 30 generates a second output which reaches Hi or Lo level respectively when the positive direction voltage of the input waveform is smaller or greater than a second detection level. When a voltage falls, both first and second outputs remain in Hi level status. The logical product of the first and second outputs is obtained by means of an AND circuit 32 and sent to a timer unit 34. Then, the output of the timer unit 34 varies and falls, and trigger is output from a trigger output unit 36 by means of this falling edge. Thereby, trigger can be applied within a time longer than a voltage fall latter half period.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a voltage drop detection trigger generator for commercial power supply voltage or the like, which is provided in a waveform recorder for displaying waveforms of measured voltage, current, power, etc. on a screen and recording them on paper. .

[0002]

2. Description of the Related Art Conventionally, a waveform recorder equipped with a voltage drop detection trigger generator is used to monitor a voltage drop such as a commercial power supply voltage, and a trigger is generated when the voltage level of an input waveform falls below a predetermined level. After the trigger, the input waveform or the like captured after the trigger or before and after the trigger is displayed on the screen for a certain period of time and recorded on paper for observation. This voltage drop detection trigger generator includes an input terminal 10, a full-wave rectifier 12, a smoothing capacitor 1 as shown in FIG.
4, an AMP (amplifier) 16, a comparator 18, and the like. Therefore, if the AC voltage waveform such as the commercial power supply voltage that enters the input terminal 10 is full-wave rectified and smoothed, and then put into the AMP 16,
The voltage level can be adjusted by the AMP 16. Therefore, when the level-adjusted voltage is input to one terminal of the comparator 18 and compared with the DC voltage Vref of the reference power source 20 indicating the voltage drop detection level applied to the other terminal, the voltage drop of the input waveform is found. It can detect and generate a trigger signal.

[0003]

However, since such a voltage drop detection trigger generator uses the smoothing action of the capacitor 14, the trigger is not applied unless the voltage drop state of the input waveform continues for several cycles. Therefore, the response speed is slow and the voltage drop cannot be accurately detected. In addition, when the foreign nozzle is placed on the input waveform, the voltage drops and triggers. Therefore, there is a problem that the foreign nozzle is easily affected.

The present invention has been made in view of such conventional problems, and provides a voltage drop detection trigger generator which has a high response speed, is hardly affected by an external nozzle, and can accurately detect a voltage drop. The purpose is to provide.

[0005]

In order to achieve the above object, a voltage drop detection trigger generator 22 according to the present invention is provided with a waveform level adjuster 26 for adjusting the voltage level of an input waveform in the preceding stage and its level in the middle stage. + Of adjusted input waveform
When the directional voltage is lower than the first detection level set in the + direction, the first detection unit 28 generates a first output that is at the Hi level and when the directional voltage is higher than the first detection level, and when the voltage is at the higher level, the − direction voltage of the level-adjusted input waveform is the A second detection unit 30 that generates a second output that has a Hi level when the detection level is equal to that of the first detection level and is greater than the second detection level set in the negative direction of the opposite polarity, and becomes a Lo level when the polarity is smaller, and the like. The first of
An AND circuit 32 that outputs a logical product of the second outputs,
A timer unit 34 that outputs a pulse having a width corresponding to a little more than a half cycle of the input waveform at one of the rising edge and the falling edge of the logical product output in the subsequent stage, and a trigger by the falling edge of the output of the timer unit 34 And a trigger output unit 36 for outputting.

Then, the waveform level adjuster 42 in the preceding stage
It is preferable to interpose an AD converter 48 for converting the level-adjusted input waveform from an analog value to a digital value between the first and second detection sections 44 and 46 in the middle stage.

[0007]

With the above configuration, the voltage level of the input waveform is adjusted by the waveform level adjuster 26 and then applied to the first and second detectors 28 and 30. Then, the first detection unit 28 generates a first output that is at the Hi level when the + direction voltage of the level-adjusted input waveform is smaller than the first detection level set in the + direction, and at the Lo level when the voltage is larger than the first detection level, the second output. Detection unit 30
Is a Hi level when the − direction voltage of the level-adjusted input waveform is equal in magnitude to the first detection level and is higher than a second detection level set in the − direction of the opposite polarity, and is a Lo level when the voltage is lower than the second detection level. Generate output. Therefore, when the commercial power supply voltage or the like is stable at a predetermined value, Hi level and Lo level are alternately and regularly generated in both the first output and the second output, while the voltage drops. , The first output and the second output do not become Lo level,
It remains in the Hi level state. Therefore, the AND circuit 32
The logical product of the first output and the second output is obtained by and is given to the timer unit 34.

Then, the timer section 34 outputs a pulse having a width corresponding to a little more than a half cycle of the input waveform by one of the rising edge and the falling edge of the logical product output. Therefore, when the next rising or falling of the logical product output occurs within a time period corresponding to a little more than a half cycle of the input waveform after the rising or falling of the logical product output, the output of the timer unit 34 continues to be Hi. Remains leveled. However, if the next logical product output does not rise or fall, the timer unit 34
Output changes and falls. Then, the trigger is output from the trigger output unit 36 by this falling edge.

An A-D converter 48 for converting the level-adjusted input waveform from an analog value to a digital value is interposed between the waveform level adjuster 42 and the first and second detectors 44 and 46. In other words, the ± direction voltages of the level-adjusted input waveform can be converted into digital values and then applied to the first and second detectors 44 and 46, respectively. Therefore, the first detection unit 44 can perform comparison with the first detection level and the second detection unit 46 can perform comparison with the second detection level based on the digital value.

[0010]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a circuit diagram showing the configuration of a voltage drop detection trigger generator for a waveform recorder to which the present invention is applied. In the figure, 22 is a voltage drop detection trigger generator for a waveform recorder,
24 is the grounded input terminal, 26 is an AMP (amplifier), 28 is the first detector, 30 is the second detector, and 32 is A.
An ND (and) circuit, 34 is a timer section, and 36 is a trigger output section. The AMP 26 is a waveform level adjuster for amplifying or attenuating the voltage level of the input waveform such as the commercial power supply voltage which is input to the terminal 24. Therefore, AMP26
The level-adjusted input waveforms are respectively input to the first detection unit 28 and the second detection unit 30 connected to.

When the level-adjusted input waveform is input, the first detector 28 is at the Hi level when the + direction voltage of the input waveform is smaller than the first (voltage drop) detection level set in the + direction, and is at the Lo level when it is larger. Produces the first output
The second detection unit 30 is at the Hi level when the − direction voltage of the input waveform has the same magnitude as the first detection level and is larger than the second (voltage drop) detection level set in the − direction of the opposite polarity, and is Lo level when the voltage is smaller. It produces a second output that is level.
Therefore, when the voltage such as the commercial power supply voltage is stable at a predetermined value, both the first output and the second output are at the Hi level and Lo level.
Levels are generated alternately and regularly, but when the voltage drops, neither the first output nor the second output goes to the Lo level, and the Hi level remains. So AND
The circuit 32 obtains the logical product of the first and second outputs and supplies the logical product to the timer unit 34.

Then, the timer unit 34 raises the edge of the logical product output from the Lo level to the Hi level or the H level.
A pulse having a width corresponding to a little more than a half cycle of the input waveform is output by one of the edges falling from the i level to the Lo level. Therefore, when the next rising or falling of the logical product output occurs within a time period corresponding to a little more than a half cycle of the input waveform after the rising or falling of the logical product output, the output of the timer unit 34 continues to be Hi. Remains leveled. However, if the next logical product output does not rise or fall, the timer unit 34
Output changes and falls. Then, the trigger output unit 3
6 issues a trigger at the falling edge of the timer section output. When these operations are performed, the reference clock is output from the output line 38 of the first and second detection units 28, 3
0, the timer unit 34, and the trigger output unit 36. Each of the first and second detection units 28 and 30, the timer unit 34, the trigger output unit 36, and the like uses a specially made IC or a combination of general-purpose ICs.

The timing of such a series of operations is shown in FIG. In the figure, when the AND output rises, a positive logic pulse whose width is indicated by the length of a straight line with double-ended arrows is generated as the output of the timer unit 34, and when the voltage level of the input waveform is stable at a predetermined value. This indicates that the input of the next rising edge is input during the previous pulse output (Hi level), and a pulse of a little more than a half cycle is continuously output again from that point. If the frequency of the input waveform is 50 Hz, 1 cycle is 1/50 = 20 ms, so the pulse width is 10 ms. In this way, if the input waveform is checked every half cycle and a voltage drop is detected, it is possible to trigger within the time of the latter half cycle of the voltage drop, the response speed is fast, and the voltage drop is accurate. Can be detected.

FIG. 3 is a circuit diagram showing the configuration of another voltage drop detection trigger generator for a waveform recorder to which the present invention is applied. In the voltage drop detection trigger generator 40, the AMP4
An A-D converter 48 is interposed between the second and the first and second detection units 44 and 46. Therefore, the input waveform entering the terminal 50 is A- after being adjusted in voltage level by the AMP 26.
Enter the D converter 48. Then, the ± direction voltage of the input waveform whose level has been adjusted can be converted from an analog value to a digital value by the AD converter 48. In this way, the level-adjusted input waveform is converted into a digital value and then input into the first and second detection units 44 and 46, and the first detection unit 44 compares the digital value with the first detection level, After the second detection section 46 makes a comparison with the second detection level, the AND circuit 52, the timer section 54, the trigger output section 56 and the like are caused to perform the same operations as the corresponding portions in the previous embodiment. . Then, even if external noise is added to the input waveform, it is less likely to be affected by the noise, and triggers due to malfunction are eliminated. However, CL
From the K (clock) signal line 58 to the AD converter 4
8, clock pulses are input to the first and second detection units 44 and 46, the timer unit 54, the trigger output unit 56, and the like. A digital IC is used for the first and second detectors 44 and 46.

[0015]

According to the present invention described above, claim 1
Then, after adjusting the voltage level of the input waveform with the waveform level adjuster, the voltage level of the input waveform is checked by comparing the input waveform voltage level with the first and second detection levels every half cycle in the first and second detection units. The AND circuit and the timer section detect the voltage drop of and the trigger output section can trigger the voltage within a little more than a half cycle after the voltage drop. Therefore, the response speed is fast and the voltage drop can be accurately detected.

According to a second aspect of the present invention, the ± direction voltage of the level-adjusted input waveform is converted from an analog value to a digital value by the AD converter, and then the voltage is put into the first and second detection sections and the subsequent processing is performed. Therefore, not only is the response speed fast, but it is also less susceptible to the influence of external noise, so that a trigger due to malfunction does not occur, and the voltage drop can be detected more accurately.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a configuration of a voltage drop detection trigger generator for a waveform recorder to which the present invention is applied.

FIG. 2 is a timing chart showing an operation of each unit of the same voltage drop detection trigger generator.

FIG. 3 is a circuit diagram showing a configuration of another voltage drop detection trigger generator for a waveform recorder to which the present invention is applied.

FIG. 4 is a circuit diagram showing a configuration of a conventional voltage drop detection trigger generator for a waveform recorder.

[Explanation of symbols]

22, 40 ... Detection trigger generator for waveform recorder 24,
50 ... Input terminals 26, 42 ... AMP 28, 44 ... 1st detection part 30, 46 ... 2nd detection part 32, 52 ... AN
D circuit 34, 54 ... Timer unit 36, 56 ... Trigger output unit 48 ... A-D converter

Claims (2)

[Claims] 1. A waveform level adjuster for adjusting a voltage level of an input waveform, and H when a + direction voltage of the level-adjusted input waveform is smaller than a first detection level set in the + direction.
At the i level, a first detection unit that generates a first output that becomes a Lo level when the i level is large and a −
When the direction voltage has the same magnitude as the first detection level and the polarity is larger than the second detection level set in the negative-direction, H
At the i level, a second detection unit that generates a second output that becomes Lo level when small, an AND circuit that outputs a logical product of the first and second outputs thereof, and a rising edge or a rising edge of the logical product output. A voltage comprising a timer unit that outputs a pulse having a width corresponding to a little more than a half cycle of an input waveform by one of the falling edges, and a trigger output unit that outputs a trigger by the falling edge of the output of the timer unit. Drop detection trigger generator. 2. An A-D converter for converting a level-adjusted input waveform from an analog value to a digital value is interposed between the waveform level adjuster and both the first and second detectors. The voltage drop detection trigger generation device according to claim 1.