JP2012182719A - Noise removal device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide noise reduction measures which are simple and capable of accommodating to changes in noise environment.SOLUTION: A noise detection section 11 detects noise transmitted over a power line to acquire a noise waveform, an inverting amplifier circuit 12 inverts the phase of the detected noise waveform and amplifies the level thereof to generate an inverted signal, and a canceling waveform application section 14 applies the inverted signal to the power line. This can cancel the noise signal superposed on the power line to implement simple noise reduction measures in a simple configuration requiring no modifications to existing electric products and apparatuses. The automatic operation responsive to changes in noise environment can significantly reduce a maintenance load.

Description

  The present invention relates to a technique for removing periodic noise superimposed on electric wires such as a power supply line and a communication line.

  In general, electrical and electronic equipment generates unnecessary noise during its operation, and the noise is transmitted through power lines and communication cables, or radiated through space, and may cause electromagnetic effects on other equipment. is there. Depending on the intensity and nature of such noise, the affected device may break down or cause a malfunction, and measures to prevent the influence of noise are required.

  As measures against noise, there are measures to reduce the noise on the device that generates noise, and measures to prevent the noise on the device that receives the noise (see Non-Patent Document 1).

  Conventionally, as countermeasures on the side of devices that make noise, devise the mounting of electronic circuits, etc., to prevent conductive noise and radiation from being emitted to the outside as much as possible, and to provide electromagnetic shielding to devices and their components, etc. Measures are being taken. For wired and wireless communication devices, a means for attenuating unnecessary spurious noises other than the frequency band used for communication is used for the communication output using a filter or the like.

  On the other hand, as countermeasures on the side of equipment that receives noise, electromagnetic shielding is applied to the entire equipment to prevent radioactive and inductive noise, or filters are pre-installed on communication lines and power lines to prevent conductive noise. Measures to insert are taken. As a filter in this case, a common mode filter is used to attenuate external noise. However, since the effective frequency band of the filter is limited, it is necessary to assume the frequency band of noise in advance. In that case, it is impossible to cope with noise of an unexpected frequency. In a communication line or the like, noise outside the band can be removed by using a normal mode filter that passes only the frequency band used for communication.

  As countermeasures against lightning and overvoltage, a surge protection element (SPD) is attached to the communication line or power line, and when a large voltage or large current exceeding the threshold flows into the device, it can escape to the ground or the communication line A countermeasure is taken to bypass the surge voltage / current from the power supply line or vice versa (see Non-Patent Document 2).

“Latest Electromagnetic Wave Absorption and Shielding”, 2nd edition, Nippon Engineering Books, September 10, 1999, p. 4-5 Shoichi Kuramoto, “Lightning Protection Technology for Broadband Communication Equipment”, NTT Technical Journal, Nippon Telegraph and Telephone Corporation, March 2003, Vol. 15, No. 3, p. 47-50 “The latest noise countermeasure technology”, General Technology Publishing Co., Ltd., July 30, 1986, p. 118-125 "Reason for use | Ferrite core | Basic knowledge | Murata Manufacturing Co., Ltd." [online], Murata Manufacturing Co., Ltd. [Search February 15, 2011], Internet <URL: http://www.murata.co.jp /products/emc/basic/ferrite/reason.html>

  In the conventional noise countermeasure, the electromagnetic shield is not effective for the conductive noise flowing into the device via the power line, and therefore a countermeasure using a filter is taken. However, since the power supply frequency is as low as 50 Hz or 60 Hz, an attempt to construct a low-pass filter at this frequency in order to realize a normal mode filter requires a large-capacity capacitor, inductance, and coil with a large current capacity. It becomes a heavy and expensive filter. On the other hand, as the common mode filter, an insulating transformer (Non-patent Document 3), an external filter using a ferrite core or the like (Non-Patent Document 4) is used. As for the former, it is necessary to increase the number of windings and use a core material with high transmittance in order to reduce power loss, and there is a drawback that it becomes large, heavy and expensive as the current capacity is increased. Regarding the latter, the attenuation frequency range as a filter is limited by the material and shape thereof, and in order to perform effective noise removal, it is necessary to change the filter according to the noise frequency. In this case, it is necessary to take the method that the maintenance person measures and analyzes the frequency characteristics and time waveform of the noise, selects the filter, and responds in the situation where the failure or malfunction actually occurs, Maintenance personnel's knowledge, skills, and experience were also required. In order to cope with noise in a wide band in advance, it is necessary to install a plurality of filters at the same time, which causes problems in terms of size and price.

  In addition, these noise countermeasures cannot cope with changes in noise frequency or waveform due to changes in the surrounding environment, and there is a problem that new countermeasures need to be taken separately.

  The present invention has been made in view of the above, and an object thereof is to provide a noise reduction measure that is easy and can cope with a change in a noise environment.

  The noise removing apparatus according to the present invention generates a reverse signal in which the phase of the noise waveform detected by the detection means is inverted and the amplitude is amplified to a desired value by detecting the noise superimposed on the electric wire. It has an inverting amplification means and an application means for applying the inverted signal to the electric wire.

  In the noise removal apparatus, an A / D conversion unit that converts a noise waveform detected by the detection unit into a digital signal, a storage unit that inputs the digital signal from the A / D conversion unit, and stores the digital signal. D / A conversion means for reading out the digital signal from the storage means, converting it to an analog signal at a timing delayed by an integral multiple of the noise period, and outputting the analog signal to the inverting amplification means. .

  In the noise removal apparatus, the inverting amplification unit is disposed in front of the D / A conversion unit, and reads the digital signal from the storage unit and performs data processing on the digital signal. A digital inverted signal is generated by inverting the phase of the noise waveform and amplifying the amplitude to a desired value, and the D / A conversion means converts the digital inverted signal into an inverted signal that is an analog signal and applies the applied signal Output to the means.

  In the above-described noise removal apparatus, the detection means and the application means are commonly used as a single device, and the noise detection processing by the detection means and the inverted signal application processing by the application means are controlled in a time-sharing manner. It has the means.

  In the noise removing apparatus, an effect measuring unit that measures a noise component remaining on the electric wire to which the applying unit has applied the inverted signal, an application timing of the inverted signal based on a measurement result of the effect measuring unit, and the inversion Evaluation means for controlling both or any one of the amplification levels of the signal.

  According to the present invention, it is possible to provide a noise reduction measure that is easy and can cope with a change in a noise environment.

It is a functional block diagram which shows the structure of the noise removal apparatus in 1st Embodiment. It is a graph which shows the power supply voltage waveform and noise waveform of a power supply line. It is a functional block diagram which shows the structure of the noise removal apparatus in 2nd Embodiment. It is a figure for demonstrating degradation of the cancellation effect when a cancellation waveform is delayed. It is a figure for demonstrating the cancellation effect at the time of delaying a cancellation waveform by 1 period. It is a functional block diagram which shows the structure of the noise removal apparatus in 3rd Embodiment. It is a functional block diagram which shows the structure of the noise removal apparatus in 4th Embodiment. It is a functional block diagram which shows the structure of the noise removal apparatus in 5th Embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following, noise removal in a general commercial AC power supply line will be described as an example. However, the present invention is not limited to the AC power supply line and can be widely applied to electric wires such as communication lines. In particular, it is effective for noise removal when the noise has a certain periodicity.

[First Embodiment]
FIG. 1 is a functional block diagram showing the configuration of the noise removal apparatus according to the first embodiment. The noise removal apparatus 1 shown in FIG. 1 includes a noise detection unit 11, an inverting amplification circuit 12, a gain control unit 13, and a cancellation waveform application unit 14. In the present miscellaneous eliminator 1, a noise detection unit 11 and a canceling waveform application unit 14 are attached to a power supply line that supplies power from the power supply 100 to the load 110, thereby removing noise conducted through the power supply line. FIG. 2 shows a power supply voltage waveform 300 and a noise waveform 200 of the power supply line. The frequency of commercial power supply in Japan and overseas is 50 Hz or 60 Hz, and as shown in FIG. 2, the noise superimposed on the power supply line is often synchronized with the cycle of the power supply voltage of 50 Hz or 60 Hz. Hereinafter, each part of the noise removal apparatus 1 will be described.

  The noise detector 11 detects common mode noise superimposed on the power supply line to obtain a noise waveform. The noise detector 11 can be realized using a current probe for measuring a common mode current, a capacitive voltage probe for measuring a common mode voltage, or the like. As for the noise current waveform, electrical processing is facilitated by terminating it with a constant impedance and extracting it as a voltage waveform. Although FIG. 1 shows an example of a power supply line, in the case of a power supply line, the potential difference between one side (cold side) and the earth ground may be directly measured. In the case of a communication line that performs balanced transmission, the potential difference between one of the pair lines and the earth ground may be directly measured.

  The inverting amplifier circuit 12 receives the noise waveform detected by the noise detection unit 11 and generates an inverted signal whose level is amplified to a desired value by inverting the phase of the input noise waveform. The inverting amplifier circuit 12 sets the signal amplification gain to a desired value in accordance with an instruction from the gain control unit 13. This can be realized by using an existing variable gain inverting amplifier circuit or the like.

  The cancellation waveform application unit 14 applies the inverted signal generated by the inverting amplifier circuit 12 to the power supply line. As a result, an inverted signal having a waveform that cancels the original noise signal is added to the power line. By setting the level of the inverted signal at the gain control unit 13 so as to be the same value as the original noise signal, it is possible to cancel the noise signal. As a result, it is possible to suppress and eliminate noise that propagates along the power line. The cancellation waveform applying unit 14 can use a current probe or a capacitive voltage probe having the same structure as the noise detecting unit 11 for signal application. In addition, it is also possible to use various devices that are used for EMC measurement or the like, such as a capacitive coupling clamp, and have a function of applying a common mode signal to a power supply line or a communication line. In addition, a voltage may be applied directly between both wires and ground. When noise is detected as a current by the noise detection unit 11, it is possible to remove noise with high accuracy by applying an inversion signal for cancellation in the form of current using a current probe or the like.

  As described above, according to the present embodiment, the noise detection unit 11 detects the noise conducted through the power supply line, and inverts the phase of the noise waveform detected by the inverting amplifier circuit 12 to amplify the level. By applying an inverted signal to the power supply line by the cancellation waveform applying unit 14, the noise signal superimposed on the power supply line can be canceled, so that the existing electric product or electrical device can be modified with a simple configuration. It is possible to easily reduce noise without adding it. In addition, since the operation automatically follows even when the noise environment changes, it is possible to greatly reduce the operation for the maintenance person.

[Second Embodiment]
FIG. 3 is a functional block diagram showing the configuration of the noise removal apparatus according to the second embodiment. The noise removal apparatus 2 shown in FIG. 1 includes a noise detection unit 21, an A / D conversion unit 22, a memory 23, a data read / D / A conversion unit 24, a timing control unit 25, an inverting amplification circuit 26, a gain control unit 27, And a cancellation waveform applying unit 28.

  The noise detection unit 21 has a function similar to that of the first embodiment, and detects noise for at least one cycle of a power supply frequency of 50 Hz or 60 Hz.

  The A / D converter 22 converts the analog waveform of noise detected by the noise detector 21 into a digital signal. This can be realized by using an existing analog / digital conversion circuit or the like.

  The memory 23 stores and holds the A / D converted noise waveform in the form of digital information. Since the level of white noise mixed during measurement is reduced by the averaging process, the noise waveform may be accumulated in the memory 23 over a plurality of periods and averaged to remove the influence of the white noise.

  The data read / D / A converter 24 delays the detected noise by an integer multiple of the noise period, reads the digital information of the noise waveform stored in the memory 23, and converts it into an analog signal. The data read timing can be arbitrarily set by an instruction from the timing control unit 25, and can be read repeatedly at specific intervals. These functions can be realized using existing memory technology, its input / output technology, D / A conversion circuit technology, and the like.

  Further, as means for transmitting an analog signal at a desired timing, the analog signal after D / A conversion may be delayed to control the delay time. These can be realized by means such as using a coaxial tube whose physical transmission path length can be changed, or switching several delay lines of different lengths with an analog switch. It is also possible to realize a combination of the data read timing and the above-described analog delay control.

  The inverting amplifier circuit 26, the gain control unit 27, and the cancellation waveform application unit 28 have the same functions as those in the first embodiment, and invert the intensity of the analog signal output from the data read / D / A conversion unit 24. Then, the level is amplified and applied to the power supply line.

  In the case where the delay time generated between the detection of noise by the noise detection unit 21 and the cancellation waveform application unit 28 applying the inverted signal is so small as to be negligible compared to the noise period, the first embodiment As in the embodiment, noise can be canceled only by gain control. However, in reality, a delay occurs due to noise waveform conversion, storage, readout, inversion processing, and the like. In this case, the noise inversion waveform 201 in FIG. 4B with respect to the noise waveform 200 in FIG. 4A becomes a waveform including a time lag, and as a result, the waveform 202 after the cancellation processing is the waveform in FIG. As shown in FIG. 2, the canceling effect is not sufficiently exhibited. In the example shown in FIG. 4, the noise inversion waveform 201 is delayed by about 160 μs with respect to the noise waveform 200.

  Thus, for example, for periodic noise synchronized with commercial power supply frequencies of 50 Hz and 60 Hz, the delay time from when the noise detecting unit 21 detects the noise until the cancellation waveform applying unit 28 applies the inverted signal is The delay time is controlled to be an integral multiple of the period. By applying a noise inversion waveform 211 obtained by inverting the noise waveform 200 by delaying the noise period by one period to the power supply line, the maximum noise removal effect can be obtained as shown in FIG. In the example shown in FIG. 5, the noise inversion waveform 211 is delayed from the noise waveform 200 by about 20 ms.

  As described above, according to the present embodiment, the detected analog waveform of noise is converted into a digital signal and stored in the memory 23, and the data read / D / A converter 24 is connected to the memory 23. Read the digital information of the noise waveform stored above and convert it to an analog signal, invert the phase of the converted analog signal to amplify the level, and delay the detected noise by an integer multiple of the noise period Since the noise signal can be canceled by applying to the power supply line, it is possible to suppress and remove the noise transmitted through the power supply line.

[Third Embodiment]
FIG. 6 is a functional block diagram showing the configuration of the noise removal apparatus according to the third embodiment. The noise removal apparatus 3 shown in the figure includes a noise detection unit 31, an A / D conversion unit 32, a memory 33, a data read / inverted amplification signal generation unit 34, a timing / gain control unit 35, a D / A conversion unit 36, and A cancellation waveform application unit 37 is provided.

  The noise detection unit 31, the A / D conversion unit 32, the memory 33, and the cancellation waveform application unit 37 have the same functions as those in the second embodiment. The third embodiment has a data read / inverted amplified signal generation unit 34 in front of the D / A conversion unit 36, and the data read / inverted amplified signal generation unit 34 receives a digital signal having a noise waveform from the memory 33. In addition to reading, the amplitude and inversion and amplification are performed by signal processing at the digital signal stage based on the timing and gain instructions from the timing / gain controller 35. Thereafter, the D / A converter 36 converts the digital signal into an analog signal to generate an inverted signal for cancellation, and the cancellation waveform application unit 37 applies the inverted signal to the power supply line.

  As described above, according to the present embodiment, the detected noise analog waveform is converted into a digital signal, stored and held in the memory 33, and the data read / inverted amplified signal generation unit 34 stores the memory 33. A noise waveform digital signal is read out from the signal, and the amplitude is inverted and amplified by signal processing at the stage of the digital signal, and the D / A converter 36 converts the digital signal after the signal processing into an analog signal and applies it to the power supply line. Thus, the noise signal can be canceled out, so that it is possible to suppress and remove the noise propagating through the power line.

[Fourth Embodiment]
FIG. 7 is a functional block diagram showing the configuration of the noise removal apparatus according to the fourth embodiment. The noise removal apparatus 4 shown in the figure includes a noise detection / cancellation waveform application unit 41, an A / D conversion unit 42, a memory 43, a data read / D / A conversion unit 44, a timing control unit 45, an inverting amplification circuit 46, a gain. A control unit 47 and a time division control unit 48 are provided.

  The current probe and the capacitive voltage probe used in the noise detection units 21 and 31 of the second and third embodiments can be used for the cancellation waveform application units 28 and 37 by using the same probe for signal application. Therefore, in the fourth embodiment, a noise detection / cancellation waveform application unit 41 that shares noise detection and cancellation waveform application by the same probe is provided, and a time division control unit 48 is used to operate in a time division manner.

  For example, the time division control unit 48 is used for noise detection for a certain period, and the subsequent 499 periods are used for canceling the waveform based on data measured for one period, that is, once every 10 seconds. Noise removal is performed based on the result of noise measurement of 20 msec. In this case, a noise component remains for one period out of 500 periods, but the influence of noise as power is extremely small.

  Therefore, according to the present embodiment, the noise detection / cancellation waveform application unit 41 sharing the noise detection and cancellation waveform application by the same probe is provided, and the time division control unit 48 is used to perform the operation in time division. Thus, the apparatus can be simplified and downsized.

[Fifth Embodiment]
FIG. 8 is a functional block diagram showing the configuration of the noise removal apparatus according to the fifth embodiment. The noise removal apparatus 5 shown in the figure includes a noise detection unit 51, an A / D conversion unit 52, a memory 53, a data read / D / A conversion unit 54, a timing control unit 55, an inverting amplification circuit 56, a gain control unit 57, A cancellation waveform application unit 58, an effect measurement unit 59, and an error evaluation unit 60 are provided.

  The fifth embodiment further includes an effect measurement unit 59 and an error evaluation unit 60 as compared with the second embodiment shown in FIG. 3, and controls the timing control unit 55 and the gain control unit 57. This is automatic control by feeding back the noise reduction effect. Noise detector 51, A / D converter 52, memory 53, data read / D / A converter 54, timing controller 55, inverting amplifier circuit 56, gain controller 57, and cancellation waveform applying unit of noise removing apparatus 5 Since 58 has the same function as that of the second embodiment, the description thereof is omitted here.

  The effect measuring unit 59 measures the residual component of noise reduced by the cancellation waveform applying unit 58 applying the cancellation waveform.

  The error evaluation unit 60 detects a residual noise waveform when the cancellation effect measured by the effect measurement unit 59 is insufficient, and feeds back the result to the timing control unit 55 and the gain control unit 57. The timing control unit 55 and the gain control unit 57 automatically adjust the delay and gain so that the residual noise is minimized.

  Therefore, according to the present embodiment, by providing the effect measurement unit 59 and the error evaluation unit 60 and feeding back the noise reduction effect, the noise suppression effect can be obtained automatically without requiring adjustment or the like.

  Of course, the first, third, and fourth embodiments may include the effect measurement unit 59 and the error evaluation unit 60.

DESCRIPTION OF SYMBOLS 1, 2, 3, 4, 5 ... Noise removal apparatus 11, 21, 31, 51 ... Noise detection part 41 ... Noise detection and cancellation waveform application part 48 ... Time division control part 12, 26, 46, 56 ... Inversion amplifier circuit 13, 27, 47, 57... Gain control unit 14, 28, 37, 58 .. canceling waveform applying unit 22, 32, 42, 52... A / D conversion unit 23, 33, 43, 53. ... D / A converter 25, 45, 55 ... Timing controller 34 ... Data read / inverted amplified signal generator 35 ... Timing / gain controller 44 ... Data read / D / A converter 59 ... Effect measuring part 60 ... Error Evaluation unit 100 ... Power supply 110 ... Load

Claims (5)

Detecting means for detecting noise superimposed on the electric wire;
An inverting amplification means for inverting the phase of the noise waveform detected by the detection means to generate an inverted signal in which the amplitude is amplified to a desired value;
Applying means for applying the inverted signal to the electric wire;
A noise removal apparatus comprising: A / D conversion means for converting the noise waveform detected by the detection means into a digital signal;
Storage means for inputting and storing the digital signal from the A / D conversion means;
D / A conversion means for reading the digital signal from the storage means, converting it to an analog signal and outputting the analog signal to the inverting amplification means at a timing delayed by an integral multiple of a noise period with respect to the noise;
The noise removal apparatus according to claim 1, wherein: The inverting amplification means is disposed in front of the D / A conversion means, and reads out the digital signal from the storage means and applies data processing to the digital signal, thereby changing the phase of the noise waveform. Generate a digital inverted signal that is inverted and amplified to the desired value,
3. The noise removing apparatus according to claim 2, wherein the D / A converting means converts the digital inverted signal into an inverted signal that is an analog signal and outputs the inverted signal to the applying means. The detection means and the application means are shared to form a single device,
4. The noise removing apparatus according to claim 2, further comprising a control unit that controls, in a time division manner, a noise detection process by the detection unit and an inversion signal application process by the application unit. An effect measuring means for measuring a noise component remaining in the electric wire to which the applying means applied the inverted signal;
Evaluation means for controlling the application timing of the inverted signal and / or the amplification level of the inverted signal based on the measurement result of the effect measuring means;
The noise removal device according to claim 1, wherein

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