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JP2002509645

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DESCRIPTION JP2002509645
[0001]
FIELD OF THE INVENTION The present invention relates to a device for protecting an electrical
circuit against interface microdischarges, and to the application of this device to specific
electrical circuits. The phenomenon of electrical microdischarge has been correctly pointed out
as a source of degradation of tone reproduction in Hi-Fi (high fidelity) systems. In this type of
device, when the conductor-electrical insulator interface is exposed to a variable electric field,
discharge occurs at the level of this interface even in situations where the electric field is
generated from low voltages, on the order of millivolts. Get up. The voltage values are very
common when operating with audio frequency signals. Although very rapidly at 0.1 μs,
relatively low levels at the audio frequency, -80 dB, their discharges still cause considerable
change in the emitted electric field. In detail, they are known as boundary microdischarges. Their
pulse repetition rates fall in particular in the audio frequency range, and they are correlated to
the audio frequency signal, the latter degrading the sound quality of the music played on this
kind of device. Technical elements related to the manufacturing method and intended to improve
the tone are described in French patent no. Specifically described in 96 12369. The French
patent is included in this patent application for reference. Thus, when the insulated conductor is
exposed to a variable electric field, a discharge is generated at the conductor / insulator interface
by a relaxation process according to the highest probability hypothesis. See Figure 0a. However,
the electric field emitted can be very high with respect to the device ground or reference voltage
and can not be considered negligible in any case. Based on the hypothesis of a destructive
discharge or breakdown in the insulating layer in direct contact with the conductor, C1 is
conductive in relation to the model produced to represent the phenomenon as shown in FIG. C2
represents the conductive capacitor reference voltage or ground, e represents the discharge gap
that "causes" the microdischarge phenomenon. The variable voltage applied to the terminals of
the electrical capacitor C1 of the insulating layer in direct contact with the conductor is shown in
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FIG. This voltage is evidence of the presence of a very fast relaxation oscillation, whose repetition
rate disturbs the audio frequency signal. However, in the laboratory of ELECTRIC DE FRANCE,
Mr. P. Research on microdischarge phenomena conducted by JOHANNET pointed out the
following characteristics.
Microdischarges occur at very low ambient voltages, less than 1 millivolt. They appear to be
unaffected by the threshold. The breakdown voltage of these microdischarges is very low,
probably between 1 μV and 1 mV. The front of the discharge is very fast, less than 1 ns. The
microdischarges necessarily produce locally an electromagnetic wave which constitutes a large
destructive element, in particular in electrical circuits or electronic circuits of audio frequencies.
Furthermore, the same kind of discharge may appear on the outer surface of the insulator
covering the conductor, in fact the insulator-air interface. This phenomenon is particularly
justified by the Maxwell-Wagner effect that charge concentration may appear at the interface
between two layers of insulating material. Another study has shown that these microdischarges,
in the verbal mechanical sense of their support, are extremely sensitive to seismic conditions.
Thus, this phenomenon also relates the phenomenon of microdischarges to known triboelectric
phenomena, but because of the direct effect on electronic audio frequency signals generated,
transmitted or processed by their circuits, one Or there are also multiple harmful electromagnetic
waves. The manner in which they work with respect to the support conductor, shown in FIG. 0d,
can be determined in the manner described below. In effect to the conductor-insulator
breakdown phenomenon, they damage the current flowing through the support conductor and
remove electrical energy. The extent of this loss depends on the local state of the support
conductor medium. Given that the capacitances involved are of very low value, a few picofarads,
the manner in which they act locally is limited. However, the whole of their actions can not be
overlooked. In fact, in general terms, like any discharge, microdischarge phenomena generate
electromagnetic waves. The electromagnetic waves may be guided by conductor parts. The
wavelength associated with the microdischarge phenomenon is between 1 cm and 30 cm in
vacuum. The range corresponds to radio frequencies between 3 GHz and 30 GHz. A direct
confirmation of the above phenomena and features is, on the one hand, by indicating the
transmission of such electromagnetic waves that occur between the output terminal of the power
supply and the casing to which the power supply is in turn grounded, and on the other hand
According to one of the objects of the invention, this is obtained by means of the attenuation
which tends to be applied to this electromagnetic wave. When the electromagnetic waves
associated with the interface microdischarges reach the electronic circuit, part of it is picked up
by the circuit elements, due to the characteristics of their non-linear transmission at the
frequency in question-and this in particular of the solder and contacts The case is--perform the
detection phenomenon to produce a parasitic voltage.
This phenomenon is further exacerbated by the fact that microdischarges are often correlated to
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the transmitted electrical signal BF, or even to the mechanical vibrations caused or caused by the
latter. Their tremors can disturb the phenomenon to a very high degree. Thus, taking into
account the above phenomenon, and more specifically, the microwave part of the so generated
parasitic electromagnetic wave, the part related to the SHF type and the interface
microdischarge, the paradox of the latter on the circuit The effects can be summarized as follows.
Individual electrical components tend to act as both a transmitter and a receiver. As receivers,
they may pick up their own transmissions and thus amplify them, or pick up transmissions of
external components and amplify them. The effect of the electromagnetic waves associated with
the interface microdischarges on the effective signal is in the form of intermodulation and
flooding, given the transmission non-linearities present at such radio frequencies. The placement
of the parts is very important, as the placement of the parts determines the ability of the part to
pick up this electromagnetic wave. Therefore, it seems more advantageous to arrange the parts in
a random orientation. -For the same reasons, the composition and structure of the wiring and
printed circuit are important. The reason is that each conductor constitutes a transmitting
antenna and a receiving antenna at the above frequency. The presence of an insulator on the line
also promotes the process of generating this electromagnetic wave. Clearly analgesia parts such
as bypass or connector sockets can prove to be catastrophic. Electrically insulating or other
absorbing screens show very variable behavior at the above frequencies, which may concentrate,
reflect or diffract electromagnetic waves, resulting for example in totally unexpected results. -The
electromagnetic waves associated with the interface microdischarge may be conducted outside
the conductor and thus can completely enter into any other parts such as plugs, transformers or
windings. -Mounting on racks or other structures that operate completely on the test bench has
proved to be disadvantageous with regard to the tones generated by audio frequency devices,
while conventional electronic such as signal to noise ratio etc. The measurements may hardly
change or even appear to be improved. In practice, it has been unexpectedly found that this type
of attachment has the effect of producing a resonator or even a "microwave" to the
electromagnetic waves associated with interface discharges.
-Electromagnetic waves as a result of microdischarges may be at insulator-conductor interface or
insulator-insulator interface where there is an electrostatic field associated with the audio signal
due to the effect of the avalanche. May cause a microdischarge. The main power supply appears
to be the main source of minor discharges. -The high voltage is 230V. Propagation of the
discharge produced by all receivers connected in the vicinity. The object of the present invention
is to provide an apparatus for protecting an electrical circuit from interface microdischarges.
Another object of the present invention is, more particularly, to provide means for attenuating
the electromagnetic waves associated with interface microdischarges which can be placed in any
electrical circuit. It is also an object of the present invention, more particularly, to reduce the
contribution of triboelectricity to the electromagnetic waves associated with interface
microdischarges by means of absorbing mechanical vibrations which tend to affect the electrical
circuit. It is to provide. The device proposed according to the invention, used to protect the
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electrical circuits from the interface microdischarges and the radio interference caused by the
interface microdischarges, is easier to read from the following description, read in conjunction
with the attached drawings. Will be understood. The attached drawings, apart from FIGS. 0a to
0d, show the inventor Mr. P. It relates to the technical elements known to JOHANNET. FIG. 1a
represents a first embodiment of a device for protecting an electrical circuit from interface
microdischarges configured to achieve the object of the present invention. FIG. 1b shows a
second embodiment of the device for protecting an electrical circuit from interface
microdischarges configured to achieve the object of the present invention. FIG. 2 represents a
device for protecting an electrical circuit from interface microdischarges configured to achieve
the object of the invention, wherein the electrical circuit is a loudspeaker. FIGS. 3a, 3b and 3c
represent devices for protecting the electrical circuit from interface microdischarges configured
to achieve the object of the invention, wherein the electrical circuit connects the wires of the
audio sensor in the pick-up unit . -Figures 4a and 4b represent devices for protecting the
electrical circuitry from interface microdischarges configured to achieve the object of the
invention, wherein the electrical circuitry is comprised of a transformer and a separation
transformer, respectively. -Figures 5a and 5b consist of circuits of discrete electrical components
in which the electrical circuits are wired on a printed circuit board, the interface microcircuits
configured to achieve the object of the present invention from the electrical circuit Represents a
first change and a second change of the device to be protected. -Figures 6a, 6b, 6c and 6d
represent devices protecting the electrical circuit from interface microdischarges configured to
achieve the object of the invention, the electrical circuit being a specific electrical or electronic
connector.
FIGS. 7a and 7b show a part of an apparatus for protecting an electrical circuit from interface
microdischarges configured to achieve the object of the invention, wherein the electrical circuit is
comprised of discrete elements wired to a printed circuit board. Represents a change of 1 and a
second change. FIG. 8 represents a device for protecting an electrical circuit from interface
microdischarges configured to achieve the object of the invention, wherein the electrical circuit is
a stabilized power supply. The various figures are shown at least partially in cross section to
more clearly show the various parts. A more detailed description of an apparatus configured to
achieve the object of the present invention for protecting electrical circuits from interface
microdischarges and radio interference caused by those interface microdischarges is shown in
FIG. 1a. And 1b, given below with reference to the first embodiment and then the second
embodiment. Generally speaking, the device proposed by the invention for protecting electrical
circuits from interface microdischarges and radio interference caused by those interface
microdischarges is also applicable to any kind of electrical circuit . The concept of electrical
circuit is a conductor or a simple electrical cable, a much more advanced electrical circuit such as
a transformer, an electrical circuit with discrete components or an electrical circuit in the form of
integrated circuit components wired to a printed circuit board, electrical connectors and
electronics It includes the broad field of at least one of the connector, a motorized device such as
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a speaker, or, for example, associated with the pickup of an audio sensor. Generally speaking, the
devices proposed by the invention for protecting the electrical circuit from the interface
microdischarges and the radio interference caused by the interface microdischarges are arranged
in the vicinity of the electrical circuit. It is noteworthy that the device is an element that
attenuates the electromagnetic wave generated by the interface microdischarge. With reference
to FIG. 1a, given by way of example and not limitation in any way, the electrical circuit of this
figure may be composed of a plurality of conductors, such as enamelled wire, having a diameter
of 5/10 mm. It has been known. Those conductors are indicated by reference numeral 1 in FIG.
1a. Between the conductor 1 and the surrounding space, and even with their lines, ie the
shielding enamels covering the conductors, there are elements for attenuating the
electromagnetic waves generated by their interface microdischarges which normally occur. It is
indicated in FIG. 1a by reference numeral 2. Advantageously, in the embodiment shown in FIG.
1a, the element 2 for attenuating the electromagnetic waves generated by their interface
microdischarges is a coating of semiconductor material deposited on the outer surface of the
conductor 1.
According to one advantageous feature of the invention, the element 2 is made of this
semiconductor material, such that the outer surface of the conductor is maintained at an
electrostatic potential with a constant local value close to that of the conductor 1, The linear
resistivity of the semiconductor material is selected to be within a particular value range, during
which all of the non-constant discharge currents caused by the interface microdischarge are
absorbed, whereby the electromagnetic waves generated by them are It is attenuated. More
specifically, the linear resistivity per unit length of the semiconductor coating constituting
element 2 to attenuate electromagnetic waves is in the range of 0.1 Ωm and 10 Ωm. Nonlimiting embodiments of devices configured to achieve the object of the present invention for
protecting electrical circuits from interface microdischarges and radio interference caused by
those interface microdischarges. The element 2 for absorbing electromagnetic waves generated
by the interface microdischarge in the form of a liquid salt solution or a gel thereof having a
resistivity close to 0.7 Ωm, which corresponds to the resistivity of physiological serum, for
example Can. This solution has been found to work particularly well. Obviously, in order to
provide this absorbent element as a sleeve enclosing the conductor 1 as shown in FIG. 1a, for
example, made from polystyrene or polytetrafluoroethylene, for example, the same reference
numerals as in FIG. It is necessary to provide an envelope containing plastic tubes, shown at 20.
The envelope thus provided is provided with an end-sealing sleep shown at 21 in FIG. 1a and a
complete seal by adding a silicon seam shown at 22 in the same FIG. 1a. Seal by. The silicone
seams / sealing sleeves 21, 22 constitute, for example, a sealed passage of the conductor 1.
Finally, a heat shrinkable sheath 23 is provided at each end of the plastic envelope or tube 20 to
provide a protected cable that achieves the objects of the present invention. The protected cable
is indicated by the reference symbol CP after this description. The passage for the electrical
conductor 1 through the sealing sleeve 21 can be filled with an epoxy resin, which is indicated in
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FIG. Finally, in a preferred embodiment, attenuation element 2 can be provided in the form of
0.9% sodium chloride solution NaCl or physiological serum. Due to the particularly advantageous
features provided by the present invention, the elements 2 used to attenuate the electromagnetic
waves generated by the interface microdischarge are elements which absorb the electromagnetic
waves generated by their disturbing discharges. is there.
For example, as will be described in more detail after this description, it attenuates all the
unstable discharge current generated by the interface microdischarge, and the damping effect
attenuates the amplitude of the radiated electromagnetic field according to Maxwell's law Also,
apart from absorbing, this same element 2 used to attenuate the electromagnetic waves
propagates the electromagnetic waves generated by the interface microdischarge by radiation
due to the semiconductivity of the above attenuation element 2 It can also be absorbed by
attenuating the applied electric field. It will be recalled that the conditions at the boundaries of
the conducting walls of the waveguide require electric field values that are approximately zero in
the vicinity of the walls in order to cause the electromagnetic waves to propagate and guide in
the waveguide. Likewise, due to its semiconducting properties, the damping element 2 has the
effect of reducing the value of the emitted electromagnetic field which occurs as a result of any
microdischarge. A second variant of the embodiment of the interface microdischarges and the
device for protecting the electrical circuit from radio interference caused by the interface
microdischarges is described below with reference to FIG. 1b. By way of non-limiting example in
any respect, the electrical circuit shown in the case of FIG. 1b is a transformer. In this case, it is
particularly advantageous to provide the element 2 for attenuating the electromagnetic waves
generated by the interface microdischarge in the form of an element for absorbing mechanical
vibrations which tend to affect the electrical circuit in question. It is known to be. The
transformers shown in FIG. 1b with reference number 1 are the locations of the
electromechanical quakes and their electromechanical quakes generate electrical
microdischarges, hence due to the presence of those microdischarges Radio interference tends to
occur. Reference numeral 2 in FIG. 1b indicates an element used to attenuate the electromagnetic
wave generated by the microdischarge. This element is an element that absorbs the mechanical
vibration. By choice, it can be a powdery element with the above-mentioned semiconductor
properties. In the same FIG. 1 b, reference 20 designates a casing containing the electrical circuit
1. The electrical circuit consists of a transformer which is submerged in the powdered element 2
and the powdered element. The powdered element is also shown in FIG. 1b. Obviously, the other
components are, for example, graphitize the transformer windings with a very thin graphite
layer, and an external link between the transformer forming the electrical circuit 1 and the
external circuit. By graphitizing the constituent conductors it can be incorporated as a means of
reducing the effects of interface microdischarges as much as possible.
The casing 20 can be of the type made of a suitable, sufficiently rigid plastic material. In a
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preferred embodiment, silica sand containing 0.1% by volume of powdered graphite was used as
the powdered element 2. In terms of its effect, the phenomenon of interface microdischarge is
similar to that of electromagnetic interference. However, its particularly complex action makes it
more easily distinguished from electromagnetic interference. Thus, it requires specific protection.
Its mode of operation is actually tied to various interface microdischarge sources. Of course, you
can pick out the following: -A high power source not correlated to the audio signal to be
disturbed: essentially a sector at 50 Hz (and its harmonics) and means to convert it; a
transformer, a motor, to be correlated to the audio signal to be disturbed High power sources
that are: speakers and amplifiers-speaker cables,-small power sources that are not correlated to
the audio signal being disturbed: conductors close to the system, which are generally negligible
compared to other sources,-disturbed Small power sources correlated to audio signals: essentially
electronic devices and associated wiring, although they are assumed to be isolated from
vibration, it is not always the case that seismic switches and other Explains why the support
structure of is used. The types of operations that can be taken on the audio signal with respect to
the microdischarges and the associated electromagnetic waves are as follows without exclusion.
Direct action on the current of the effective signal when a microdischarge occurs; If the included
capacity value is very small, the model shows that this effect is probably negligible. Detection of
electromagnetic waves emitted by microdischarges by non-linear elements of the circuit: this
type of operation is more likely to occur. The reason is that the detection is performed by an
element that is actually partially corrected, such as a solder or bimetal contact. Soldering
problems have been raised for quite some time by audio workers. It has to be pointed out that, at
the frequency in question, all conducting elements should be modified to some extent. It is
conceivable that an electromagnetic wave highly correlated with the audio signal may be
detected and reinjected into the circuit to effectively cause degradation of the musical tone.
Action by an external source that is not correlated to the effective signal (sector). Although this is
more difficult to reveal. However, on the assumption that microdischarges exist-and in an effort
to eliminate them-the efficiency of the designed sector filter represents one possible mode of
operation.
The 50 Hz sector and the associated transformer supply an electromagnetic wave of a
microdischarge which is not correlated to the audio signal but which has a large amplitude. The
electromagnetic wave tends to promote or even trigger microdischarges in the audio circuit
which is itself polarized by the signal itself. Then we do intermodulation between the latter and
the 50 Hz signal and its harmonics when the trigger element is a 50 Hz sector and when the
triggered signal is an electromagnetic wave of a microdischarge in the effective signal Faced with
the whole set of. The effectiveness of the device proposed according to the invention for
protection against microdischarges proves indirectly the presence of microdischarges. Basic
protection is assumed to be electrical conductor, insulated, Fully conductive to promote local
equipotentiality, and consumes electromagnetic waves associated with microdischarges And
surrounding with semiconductor material that is sufficiently resistant to absorb. Since
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microdischarges are generated at the conductor-insulator interface, the condenser generates
microdischarges. Only air (or vacuum) capacitors have some effect. By covering the transformer
with a mechanical absorber allowing simultaneous consumption of the electromagnetic waves,
the transformer is protected against the emission of microdischarges. In the differential mode, it
is preferable that microdischarges can be absorbed by the RC circuit. R: non-inductive resistance,
preferably carbon resistance, close to the characteristic impedance of the conductor in question,
C: air condenser or vacuum capacitor. In the in-phase mode, absorbing the electromagnetic
waves associated with the microdischarges is a delicate issue and involves coating the circuit
with a semiconductor medium. The medium also absorbs vibrations in the case of seismic
elements (motors, transformers). This electrical circuit is a detailed description of an apparatus
configured to achieve the object of the present invention to protect the electrical circuit from the
interface microdischarges and the interference caused by the interface microdischarges. The case
of being a loudspeaker will be described below with reference to FIG. In a conventional manner,
the loudspeaker shown in this figure has a magnetic head provided with a gap section LE,
designated CU, and an electrical coil connected to the cone of the loudspeaker. The cone is
indicated by M in FIG. The periphery of the cone M is joined to the frame A in a conventional
manner. The frame A is substantially in the shape of a salad bowl and is connected to the
magnetic head CU.
An electrical coil distributed on the base of the cone M is arranged in the gap section LE. The coil
is connected to the output terminals BS1 and BS2 and to the connection of those terminals. The
connection line is connected to the output terminal of the electrical amplifier. Generally speaking,
and in order to protect the loudspeaker unit shown in FIG. 2 against the interface microdischarge
phenomenon, on the one hand a thin graphite coating is applied to the coil placed on the base of
the cone M The coil, which is shown in FIG. Apart from the above mentioned graphite coating on
the speaker coil, the device shown in FIG. 2 which constitutes the object of the present invention
has a lining of semiconductor foam material, indicated by reference numeral 2. This lining is
located at the bottom of the gap section LE. The walls of the interstitial compartments also have a
surface finish of the semiconductor material. Finally, the terminals BS1, BS2 can be provided with
a protective coating. This coating protects the terminals and connects the wires of the terminals,
which is made of semiconductor material and covers the latter over at least a part of its length.
The coil coated with the graphite layer 10 is provided with a coating of semiconductor material,
and the protective coatings on the terminals BS1 and BS2 and the connection lines of those
terminals are the same conductive as used in the bottom of the gap section LE It should also be
pointed out that sex forms can be made. In a non-limiting embodiment, the connection between
the terminals BS1, BS2 and the electrical amplifier terminals is provided in the form of a
protected line CP, such as the one described above in connection with FIG. 1a. be able to.
Furthermore, at the end of the connection line, i.e. for example the line CP to be protected, a filter
can be provided which removes very high radio frequencies. The removal filter is connected to
the end of the line or to the part of the connecting line which is coated with semiconductor
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material. In another non-limiting embodiment, the rejection filter can be provided in the form of a
low value resistance in series with the central core of the line. Those resistors, indicated by R in
FIG. 2, are connected by capacitors C of small value. In one non-limiting embodiment, resistor R
has a value between 0.1 and 2.5 ohms, capacitor C has a value between 30 pf and 100 pf, and
resistor R 'has a value of 10 ohms and 50 ohms. Between. More specifically, the operation of the
apparatus described with reference to FIG. 2 will be described below in relation to the apparatus
constituting the object of the invention.
The speaker coil has, for example, one or two layers of conductor wires which are enamelled on
the insulating tube connected to the cone M. The coil is placed in a uniform magnetic field
because of its position in the interstitial section LE. As a result, the coil is subjected to strong
vibrations due to its important function, thus producing a large number of microdischarges
which may disturb the power amplifier via the above mentioned connection lines. As described
with reference to FIG. 2, the device proposed according to the invention significantly reduces the
microdischarges occurring in the source of the circuit with the speaker coil, in particular by
absorbing the electromagnetic waves emitted by those microdischarges. Can be attenuated. The
emission level of the microdischarges can be reduced by adhering the semiconductor material
such as graphite to the actual coil in a controllable manner. The coil is thereby deposited with
graphite in order to form the graphite deposited coil 10 described at the beginning of this
description. Graphite can be deposited by spraying a film of graphite on a separate support from
the coil. The graphite used is, for example, Graphite 33 or Blindotub, both of which are
commercially available. When the film of graphite is completely dried on the support, a tool such
as a pad removes some of the dried graphite so as to blacken the pad. Thereafter, the graphite is
periodically attached to the speaker coil by the pad, so the graphite is attached over the entire
surface of the coil. It can then be buffed using a non-graphite containing pad. The buffing
operation is ended when the speaker coil has a slightly gray and shiny appearance. The portion
of the head CU which is absorbed by the semiconductor foam 20 situated near the coil at the
bottom of the gap section LE and which in any case does not impede the movement of the cone,
ie the head, which is emitted by the microdischarges At the base of, there is, for example, a cone
guard that constitutes a dome. The cone guard is shown in FIG. 2 at 20 for this reason. For the
foam being used, the semiconductor foam can be a high density foam, for example, having a
resistivity less than or equal to 15 ohm-m, such as that available from Vermason et Vitec. This
type of foam has the particular feature of having open cells. A suitable form for the above
operation can be the form sold under the number 167-848 in the FARNELL catalog by Vermason
et Vitec.
However, more conductive foams with resistivities approximately equal to 1 Ωm may be
preferred. For the task of depositing graphite to the coil, for the purposes of the present
invention, the coating deposited in this way allows local isoelectric potentials to be generated and
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allows adjustment of the surface magnetic field. However, the coating must be sufficiently
resistant to avoid trapping microdischarges in the resonant cavity. In other words, excess
graphite in the coil seems to degrade the results obtained. The wavelength specific to the
phenomenon of interface microdischarge is a wavelength in the centimeter range. Thus,
semiconductor foams configured to absorb the electromagnetic waves generated by the interface
microdischarge at their wavelength are efficient at absorbing that electromagnetic radiation, and
to avoid reflection of the electromagnetic waves, this same degree of It may be advantageous to
have length irregularities or indentations. However, in terms of capacitors C used in filters
intended to remove very high radio frequencies, those capacitors can be placed in the form of air
capacitors which are less likely to generate microdischarges internally or in vacuum. It is
preferable to provide it in the form of a condenser placed in a dry or neutral gas, which can be
air depending on the environment. It is particularly advantageous to use an enclosed capacitor,
since it can be protected from changes in the surrounding atmosphere when it is enclosed in
vacuum, in a neutral gas atmosphere, or in air, so that it is provided in this way The rejection
filter is particularly more stable at frequencies, particularly at very high frequency cutoff
frequencies to be transmitted. Finally, in the case of a loudspeaker in which an iron fluid is used
in the gap, in particular in the case of a loudspeaker known as a "tweeter", the device proposed
by the invention is due to the phenomenon of microdischarges As a means to absorb the
generated electromagnetic waves, 0.1 vol% to 1 vol% of colloidal graphite can be further included
in the irons fluid. A more detailed description of an apparatus configured to achieve the object of
the present invention for protecting electrical circuits from interface microdischarges and radio
interference caused by those interface microdischarges is shown in FIG. 3a. Or FIG. 3c in the
following. In those figures, the circuit includes a pick-up unit for a disc or phonogram, also
known as a microgroove. A brief description of how the conventional pick-up unit of the audio
sensor works will again be given below.
Audio sensors typically have a pick-up needle electrically connected to the two moving coils. The
two movable coils are positioned 90 ° apart to form a stereo pickup unit. The moving coil
moves about a pivot axis in a magnetic field indicated by H. In this situation, which is particularly
shown in FIGS. 3a and 3b, the device proposed according to the invention comprises a coating of
semiconductor material covering the moving coil and the wire constituting the wire. As shown in
the above figures, the coating of semiconductor material covering the wires making up the
moving coil can be attached to them in the form of graphite in the same process as described
above in connection with the speaker coil. However, due to the thin wires used to make these
moving coils, their work requires special attention. Furthermore, the absorbent foam of the
semiconductor material is introduced at the same level as any circuit and any compartment or
space, provided that it does not impede the movement of the moving coil. Thus, in FIGS. 3a and
3b, apart from coating the coil with graphite, the moving coil is connected to the cap m of the
form of semiconductor material surrounding the actual pick-up head and the amplifier of the
signal generated by the moving coil. The sheath is shown surrounding the wire. For this reason,
08-05-2019
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in the same way as in the above figure, the graphite-coated moving coil in FIGS. 3a and 3b is
indicated by the reference 11 at the lead connecting the moving coil to the amplifier, and the cap
m and the actual pickup head And a sheath of semiconductive foam attached to the graphitecoated wire 11 is indicated by the reference numeral 20. Special measures need to be taken to
protect the pickup unit, ie the conductor connected to the moving coil. The coils are fed through
the pick-up arm as shown in FIG. 3a or 3b. Generally speaking, it is advantageous to reconnect to
the arm as follows. -Selection of conductor: deposit enameled wire with a diameter of 1/10 mm
to 2/10 mm, for example a high temperature double coated polyurethane enamel. Replace the
existing conductors with the graphite conductors mentioned above in the description related to
the speaker coil. The graphite-coated conductor 11 is coated with a semiconductor foam 20 so as
to produce a protective sheath along the entire length of the pick-up arm. In particular, the wire
connection can be mounted inside the pick-up arm as shown in FIG. 3a and the sheath is inserted
inside this arm or mounted outside the pick-up arm as shown in FIG. 3b It should be pointed out
that, in this case, the sheath + conductor assembly is held by a clamping or clamping collar made
of polytetrafluoroethylene tape.
These fastening tapes are indicated by the reference 21 in FIG. 3b. Obviously, a filter is provided
which removes high radio frequencies at the output of the connection 11, ie in fact at the input
of the pickup amplifier. This filter has a resistor R and a capacitor C of comparable value to those
mentioned above in the loudspeaker description. In the case of a stereo pickup head having a left
channel G and a right channel D, removal filters are provided for each of the left and right
channels as shown in FIG. 3c. This can be placed under the pickup table TL itself as shown in
schematic form in FIG. 3c. The resistors used and the capacitors R, C are of the same nature and
of the same value as mentioned above in the description relating to the structure of the rejection
filter for the loudspeaker. A more detailed description of the device proposed according to the
invention, which is used when the electrical circuit is that of a mains voltage transformer, is given
below in connection with FIGS. 4a and 4b. As shown in FIG. 4a, the power supply voltage
transformer has a primary winding indicated by reference numeral 11 and a secondary winding
indicated by reference numeral 12. Similar to the device shown in FIG. 1b, the device proposed
according to the invention has a sealed envelope provided with a tightly sealed passage, as
schematically shown in FIG. 4a. The casing 20 constitutes the The enclosed passage is indicated
at 21. The enclosed envelope formed by the casing 20 has and comprises a primary winding 11
and a secondary winding 12 and, like the device shown in FIG. 1b, the mechanical vibration of
the transformer Semiconductor material that is absorbed is also filled. Also, the primary winding
11 and the secondary winding 12 are connected to one another in the enclosed path by means of
the connecting lines indicated in the figure by the reference numerals 13 and 14. Used for
primary winding 11 and secondary winding 12 in a manner analogous to the electrical circuit
described above, optionally and on the one hand for the speaker coil and on the other hand for
the moving coil of the pickup head Advantageously, the coating of the semiconductor material is
provided on the wire and on the wire connecting the primary winding and the secondary winding
08-05-2019
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with the passages 13 and 14 which enclose the latter. The semiconductor material can be
provided in the form of a deposited and buffed graphite film as described earlier in this
description. Furthermore, the enclosed envelope formed by the casing 20 is filled with
semiconductor material.
The primary winding 11 and the secondary winding 12 are embedded in the semiconductor
material 2 because the purpose is to absorb mechanical vibrations. Similar to FIG. 1b, the
semiconductor material that absorbs mechanical vibrations is a powdery material such as sand to
which graphite is mixed under the conditions described later in this description. A description is
given below of how the device operates with respect to protecting the transformer circuit from
the occurrence of boundary microdischarges. Generally speaking, after the speaker and audio
pickup unit, the transformer represents a large interface microdischarge source. Voltageinsulated windings can be accessed on the outside of their transformers. The exterior of the
toroidal transformer is also made entirely of windings. -Motor power and magnetostriction
constraints cause high levels of vibration, multiply microdischarges, and even more so if the
external winding is connected to the phase instead of the neutral point of the AC power network.
It is. Therefore, the measures taken to dampen or sufficiently suppress the occurrence of
interface microdischarges to the same level as circuits such as transformers,-create local
equipotentials at the level of the external winding,-mechanical To prevent or absorb vibrations as
much as possible-to absorb the electromagnetic waves emitted by their microdischarges and the
current generated by the latter. For example, in a similar manner, a layer of local isoelectric
potentials, such as the speaker coil or the moving coil of the audio pick-up unit, under the
conditions outlined in the beginning of this description, for example Blidotub or Graphite 33
graphite. By adhering to the outer surface of the transformer, it can be formed at the same level
as the outer surface of the transformer. A transformer temporary winding 11 and a secondary
winding 12 are placed inside the enclosed casing 20 to damp and absorb mechanical vibrations.
The space between the transformer and the casing is never smaller than 1 cm, in order to be able
to insert a suitable layer of suitable powdered semiconductor material with sufficient thickness
so as to absorb the above mechanical vibrations. Once the winding has been placed in the casing,
the open space is, for example, a graphite powder or colloidal graphite in an appropriate
proportion, such as 0.1% by volume to 0. Filled with a powdered damping mixture containing at a
rate of 8% by volume. With regard to the percentage of graphite or colloidal graphite added to
the pulverulent element, the resistivity of the so homogeneous mixture so constructed must be
between 0.1 Ωm and 10 Ωm, as mentioned at the beginning of the description. In particular, it
must be pointed out.
With regard to the base of the powdered material used, it can be in the form of silica sand to
which powdered graphite or colloidal graphite is added in the above proportions. In particular,
the volume percentage of graphite depends on the resistivity of the silica sand or powdered
08-05-2019
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material used, bearing in mind that this material is of course semiconductive if silica sand is used.
With regard to the filling of the envelope containing the primary and secondary windings, this
contains silica sand and graphite and is filled with a mixture which avoids any settling. The
mixture is injected so as to lightly cover the upper part of the transformer, strictly speaking. With
regard to the outlet of the channel 21 which is enclosed, the connection can be made using the
protected line CP, as outlined above in the description in connection with FIG. 1a. Providing a
sheath of electrically conductive foam, as shown for the connection of the secondary windings
14, assuming that the line CP protected for their connection is not used according to the device
proposed by the present invention It is advantageous. The sheath surrounds the connection line
over a large portion of its length. Furthermore, in all cases the reference CP, as shown for
connection of the primary winding of FIG. It is also advantageous to retain the ferrite core
indicated by 23. Ferrite cores that are particularly well suited for this purpose can be ferrite
cores, such as those manufactured by PHILIPS and sold under the product code 3B25 in the
SELECTRONIC catalog. Because of the electromagnetic constraints that the ferrite cores impose
on the connecting wires, they help to fight the disturbance caused by the common mode
microdischarge that tends to be propagated on the connecting wires by attenuation. Other
materials capable of absorbing mechanical vibrations can be used if they prove necessary or
more appropriate or more practical depending on the particular application being considered.
Thus, a liquid or gel, ie, “a physiological serum, a mixture of insulating oil comprising 1 to
several volume percent of suspended colloidal graphite, of an enclosed envelope made up of a
casing 20. Those insulating oils are probably from the group of paraffin oil, petrolatum oil, DIALA
insulating oils sold by SHELL, graphitized lubricating oils commonly used in mechanical
engineering. -A mixture of silica sand / physiological serum,-A mold of a molten paraffin coating
containing an appropriate percentage of graphite, and cooling the paraffin into a homogeneous
block holding assembly as a transformer Low-melting waxes, polyurethane-coated resins, epoxy
or silicone compounds, their various products are optionally filled with graphite.
They can be used if it is not necessary to disassemble the inside of the transformer. Can be filled
with a viscous liquid such as Generally speaking, the casing 20 can be made from an insulating
material, such as conventional ABS or other material, or, if necessary, a metallic conductor that
deserves the required protection for the conditions of use. If a metal casing is used, later
grounding this casing does not improve the protection provided to the circuit against the
occurrence of interface microdischarges, but may even only degrade that protection. It may be
advantageous for the casing 20 to be a double wall envelope, in which case it must be stated that
the gap between the double walls is filled with a semiconductor material such as a liquid
semiconductor material. In this case, it is preferred to use the salt solution mentioned earlier in
this description or the above physiological serum as liquid semiconductor material. In order to
ensure adequate protection, the dimensions of the gap can be of the order of about 2 cm in the
direction perpendicular to the surface of the casing. The electrical circuit is a particularly
advantageous embodiment of a device designed to achieve the object of the invention, for
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protecting the electrical circuits from the interface microdischarges and the disturbances caused
by the interface microdischarges. It will be described with reference to FIG. 4b which is a
separation transformer. The separation transformer consists of a first transformer and a second
transformer, the secondary windings of which are interconnected and the primary winding of
one of the transformers, for example transformer T1, is powered. Connected to the network and
the primary winding of the second transformer T2 is connected to the output terminal to supply
a power supply voltage approximately equal to that of the grid network without direct electrical
connection to the grid network You must first point out that it is a thing. In that case, as shown in
FIG. 4b, the device provided by the present invention comprises a first transformer T1 and a
second transformer T2 inside the enclosed casing 20, The transformers are interconnected by
their secondary windings, and the primary windings of each transformer are mutually enclosed
at the input / output terminals by the enclosed path, indicated by the reference numeral 21. A
sheath of semiconductor material, such as graphite, is connected to at least one of the primary
and secondary windings of the transformers T1 and T2 clearly, for example, a coil of a
loudspeaker or a moveable winding of an audio pickup head Can be attached in the same way as
described in connection with. The same applies to the connecting lines linking the primary
winding of the first and second transformer to the enclosed passage 21.
As far as the wires interconnecting the primary windings of the transformers, their connecting
wires are indicated by the reference numeral 22 in FIG. 4b, as we have at the beginning of this
description, semiconductor materials such as thin graphite films etc. Coatings can also be
provided on their connection lines. Also, in a particularly advantageous manner, a resistancecapacitance attenuation circuit, indicated by reference numeral 23 in FIG. 4b, is provided. The
damping circuit is interconnected in parallel between the mutually connected secondary
windings of the transformers T1 and T2. Finally, the transformers T1, T2 and the damping circuit
23 are embedded in the semiconductor material 2 contained inside the casing 20. The
attenuation circuit 23 can have at least one resistor, indicated by R. At least one electrical
capacitor enclosed in vacuum, in air or in a neutral gas is connected in series with this resistor.
This enclosed capacitor, indicated by C, is probably brought together in parallel with a capacitor
C 'of larger value. In one practical embodiment, transformers T1 and T2 are ring transformers
with a primary voltage of 110 V or 240 V, a secondary voltage of 2 × 40 V, 250 VA, sold under
the product numbers 432-453 from the FARNELL catalog. It was a bowl. Capacitor C was an air
capacitor with values in the range of 60 pf and 100 pf, and capacitor C 'was a polypropylene
capacitor with values in the range of 0.47 μf and 2, 2 μf. The resistance R was a carbon
resistance with an adaptive resistance of 3 W, 22 to 50 Ω. The semiconductor material 2
constituting the element for attenuating the electromagnetic waves generated by the interface
microdischarge was the graphitized sand mentioned at the beginning of this description. The
device proposed according to the invention is protected against the occurrence of interface
microdischarges, the electrical circuit proposed according to the invention, for example a large
number of discrete parts or a large number of integrated parts mounted on a printed circuit
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board. In connection with the case of being an electrical circuit or an electronic circuit, it will be
described below with reference to FIGS. 5a and 5b. 5a and 5b show the arrangement of
transistors, resistors, capacitors or similar discrete components on one side of a printed circuit
board. The other side of the printed circuit board is contoured and printed in a conventional
manner. As shown in FIG. 5a, the device proposed according to the invention has at least one
casing 20 which is open at one of its ends. This casing contains the semiconductor material
designated by reference numeral 2 in FIG. 5a.
The semiconductor material constitutes an element that absorbs an electromagnetic wave
generated by the phenomenon of boundary microdischarge. Also, as shown in FIG. 5a above, a
flexible plastic material is indicated by the reference numeral 21 so as to protect the electronic
circuit from the semiconductor medium or semiconductor material 2 provided in liquid form. A
protective sheath made from is provided. Thereafter, the assembly comprising the electronic
circuit CB and the protective sheath 21 is submerged in the liquid semiconductor material 2
contained in the casing 20. In the embodiment shown in FIG. 5a, the casing is open at the top.
Clearly, a sealing seal designated by reference numeral 22 is provided. This seal provides a tight
seal for the sheath 21 at the periphery of the open casing, as shown in FIG. 5a. The embodiment
shown in FIG. 5 is clearly not limiting. In particular, the plastic sheath 21 is at least the upper
edge rigidly manufactured to mechanically hold the electronic circuit CE in a substantially
vertical position, as shown in FIG. 5a. Furthermore, on the top of the circuit CE which extends
horizontally into the free air beyond the free surface of the liquid semiconductor material, the
heat generated by the operation of the circuit or circuit CE can be dissipated It is advantageous
because a radiator R can be provided. Clearly, the wire connecting the whole electronic circuit is
connected to the connection terminal of the electronic circuit CE and is the same as outlined
above in connection with the connecting wire used for the moving coil of a speaker, transformer
or audio pickup Is protected. It should be pointed out that the connecting cable and the electrical
circuit or electronic circuit CE are also protected by the plastic sheath 21 against any contact
with the liquid semiconductor material. The embodiment shown in FIG. 5 is satisfactory. It is
particularly easy and inexpensive to set up. The liquid semiconductor material can, for example,
be the salt solution or physiological serum mentioned at the beginning of this description. This is
the case when the liquid semiconductor material exerts a static pressure on the protective plastic
sheath 21 and presses it onto the electronic circuit CE. It is then particularly well protected from
interface microdischarges. The embodiment of the protection device proposed according to the
invention shown in FIG. 5a is satisfactory, wherein salt solution or physiological serum can of
course be replaced by, for example, graphitized sand impregnated with physiological serum. it
can.
However, a simplified version is shown in FIG. 5b. The appeal of this simplified variant is that the
space requirements and portability of the unit are improved, in particular because it is quick and
08-05-2019
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easy to assemble and that the semiconductor elements can be removed in the form of separate
individual elements, Thus, at least one of use and handling is much easier. In that case, as shown
in FIG. 5b, in more detail, in addition to the casing open at one of the ends, as indicated by 20,
the device proposed by the invention is a part And a plurality of packer cushions for the circuit
CE. Each packer cushion is comprised of a sheath made of plastic material filled with
semiconductor material as described in connection with FIG. 5a. In FIG. 5b, each cushion is
indicated by reference numerals 211 212, again referring to FIG. 5a, and can be given a higher
reference number if more than two cushions are used. Four cushions can be used, two of those
cushions protecting the electronic circuit CE and securing it so as to protect its electronic circuit
CE and its cushioning action, the paper on which FIG. 5b is drawn Block any movement in the
plane of the two cushions, not shown, protect the electronic circuit CE and its cushioning action
in the plane perpendicular to the paper on which FIG. 5b is drawn Used for With regard to
applying the various cushions described above, in one advantageous embodiment, the electronic
circuit CE is placed in the casing 20 which is open as shown in the initial state in FIG. In order to
protect the electronic circuit CE and its cushioning action in the plane of the paper on which FIG.
5 b is depicted, empty cushions 21, 22 are introduced as shown in the above figures. In its first
state, the cushions 21, 22 are empty. The last condition shown in FIG. 5 b is to fill each cushion
211, 212 with an absorbing liquid semiconductor material such as physiological serum, and
then, as shown by reference numeral 22 in FIG. For example, it can be obtained by sealing the
cushion in a heat sealing operation. Clearly, the two side cushions providing protection and
cushioning in a plane perpendicular to the paper on which FIG. 5b is drawn can be configured in
a similar manner. It should be pointed out that instead of using a salt solution or physiological
serum 2, it is also possible to fill the cushion with graphitized oil, silica sand containing graphite
or silica sand impregnated with serum.
Later in those cases where they are particularly effective for coping with vibration, various
cushions are first filled with silica sand and then serum is injected until the sand is completely
impregnated. Other materials, such as conductive gels of appropriate resistivity, can also be used,
or materials such as sponges that can stabilize physiological serum, or foams, such as
polyurethane foams, can be made semiconductive by the addition of graphite . The device
proposed by the invention can be used for any type of electrical circuit, as mentioned at the
beginning of this description. Apart from the various electrical circuits already mentioned, the
device proposed according to the invention can be used for any electrical or electronic connector
which constitutes a suitable route for the electromagnetic waves generated by the
microdischarges. In fact, research conducted at the laboratory of ELECTRICITE DE FRANCE has
shown that the disturbance caused, which was a radio disturbance, clearly passes through the
body of the insulator / frame-connector route ing. A first example of an embodiment of a device
for protecting against interface microdischarges and thereby caused radio interference, for
example in connection with Fig. 6a where the electrical connector is an RCA connector First, it
will be described. FIG. 6a shows a cross section of the RCA type mounted on the frame CH. In a
08-05-2019
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conventional manner, this connector has an RCA connector head with coaxial type conductors. Its
central core constitutes a conducting part. The connector head unit is attached to the frame and
secured thereto by means of bolts EC. The central core AC is surrounded by a dielectric material
which provides coaxial transmission with the outer metal casing. As shown in FIG. 6a, the device
proposed according to the invention comprises a sleeve of semiconductor foam which surrounds
the outer casing unit Ee of the RCA-type connector over its given length. The semiconductor
foam sleeve is indicated at 20 in FIG. 6a. Also as shown in the above figures, the sleeve 20 made
of semiconductor foam is a ferrite ring 21 sold at the end thereof, and in particular near the
frame CH, under the symbol 3B25 by PHILIPS. Can be held by The purpose of this ferrite ring is,
as mentioned at the beginning of this description, to suppress interference in the common mode.
Similarly, a cap of semiconductor foam is provided on the outside of the frame CH, i.e. on the
right-hand part of FIG. 6a.
It is configured to cover the entire upper structure protruding from the frame CH. This
superstructure is formed by the male end bolt EC of the RCA connector shown in FIG. 6a and a
conventional fastening means which can be a metal washer or other means. The cap shown in
FIG. 6a is indicated by the reference numeral 23. In some cases, as shown in FIG. 6b, it may be
desirable to make a connection to an internal electrical circuit or internal electronic circuit, in
particular by means of a protected line CP as described above, for better protection. It may be
advantageous to move the connector out of the frame CH. An embodiment of this kind is shown
in FIG. 6b above. In the figure, the connection is made at the level of the electrical or electronic
circuit CE by means of the line CP protected as described above, on the outer part of the frame
CH, in other words to the left of the drawing of the frame CH given in FIG. The length of the
positioned part is chosen to be approximately the length of the tube soldered to the metal frame,
indicated by the reference number TU for this purpose. This length of tube is filled with
semiconductor foam, indicated by reference numeral 20 in FIG. 6b. This unit provides a
particularly effective and robust sleeve, whereby the protected wire CP connected to the circuit
CH is then inserted through the sleeve. The ferrite ring indicated by reference numeral 21 can
also be placed inside the frame CH to further protect against common mode interference, as
mentioned at the beginning of this description. Clearly, the line CP to be protected can be of any
length in advance. However, if very long cables are used, it is preferable to provide protection
near the connector itself, such as that shown in FIG. 6b, as shown in FIG. 6c. It corresponds to the
female RCA connector in the above figure. As shown in FIG. 6c, which is the case just mentioned,
in the vicinity of the above-mentioned female connector, the device proposed by the present
invention is shown by the sleeve made of semiconductor foam, reference 20 Is placed on the
actual protected cable CP in the vicinity of this connector and a ferrite ring, indicated by
reference numeral 21, is placed on this sleeve. The ferrite ring is probably of the type sold by
PHILIPS mentioned at the beginning of this description.
08-05-2019
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The ferrite ring 21 is protected by a coating of semiconductor foam designated by the reference
numeral 22. This coating not only covers the ferrite ring 21 but also covers the sleeve 20. Thus,
the coating 22 can be held by the fasteners 23, such as the retaining collar or the like shown in
FIG. 6c. This protection is manufactured from an adhesive copper table, for example, a 9.5 to
12.7 mm wide, product of 3M product no. 1181, on the mains power ring corresponding to the
equipment to be powered. Combining by attaching the sleeve 20 of semiconductor foam as close
as possible to the power connector of the device, placed tightly around the ring by the collar 21
and separated by 15 to 25 mm as shown in 6d Can be completed or complete. One or two copper
rings 21 at the end can be replaced by a ferrite core 22 as previously described in FIG. 6c.
Obviously, as a means of protection, it is necessary to make various modifications to the circuit in
which the device proposed by the invention is to be used. As the electrical circuit or electronic
circuit in question has discrete components as shown in the examples of FIGS. 5a and 5b, it is not
easy to make the required changes to those circuits, the circuit itself should be minimal The
preferred non-limiting embodiment of the device proposed by the present invention which
requires modification can be used. It will be described with reference to FIGS. 7a and 7b. As
shown in the above figures, the device proposed according to the invention has at least one
casing which is open at one of the ends. This casing constitutes a frame at least comprising at
least the upper part designated CH1 and the lower part designated CH2. Both parts are metal
parts and are electrically isolated from one another. As shown in the above figure, the casing has
at least one frame divided into two parts, upper part CH1 and lower part CH2, and an electronic
circuit CE with many parts. The printed side of the circuit, i.e. its bottom surface in FIG. 7b, is
provided with a coating of insulating dielectric, indicated by the reference numeral 20. This
protective insulator can be the varnish of the printed circuit itself or an additional varnish.
Furthermore, the device proposed according to the invention consists of a material of the type of
semiconductor foam designated by the reference numeral 21 placed on the inner surface of the
casing, ie on the inner surface of the upper part CH1 and the lower part CH2. Has an internal
lining.
A printed circuit surface having an insulating dielectric coating 20 is placed near the inner lining
of semiconductor foam material. In particular, as shown in FIG. 7b, the two opposite sides
forming the upper part CH1 and CH2 of the frame with the inner lining of the semiconductor
foam are corrugated as shown in the above figure. In fact, it has an inner lining with The
waveform has a depth h in a direction perpendicular to the upper portion CH1 and the lower
portion CH2 and is separated by a distance d in a second direction perpendicular to the first
direction. FIG. 7a shows various embodiments that may be used to produce a waveform suitable
for use as an inner lining made of the above-described semiconductor foam 21. FIG. The
pyramidal waveform at point A in FIG. 7a to the dihedral shown at point B in this same figure and
finally the accordion and spring shaped ranges shown at points C and D in the same FIG. 7a
Various shapes of waveforms can be used. In the case of accordion-shaped corrugations, foam
sheets of the appropriate thickness are folded into accordion pleats as shown in FIG. 7a and then
08-05-2019
18
held in place by insulation retaining pins, indicated by reference numeral 22. Be done. In the case
of point D in FIG. 7a, the spring can be made from preformed elements made of semiconductor
foam material. The preformed elements are assembled sequentially from top to end in a
symmetrical arrangement with respect to the vertical plane and glued appropriately. The
assembly is held together by the holding pins 21. With regard to the dimensions of the
corrugations, the semiconductor foam boards or linings can be made in a manner similar to that
used in anechoic chambers. The mean height of the depressions or corrugations is of the order of
h = 5 cm ± 3 cm. As a general rule, if the height h is equal to 5 cm ± 3 cm as described above,
the spacing d is approximately equal to the value of h / 2. Clearly, the pointed side of the
corrugation is directed to the circuit to be protected, and then a short distance, ie a few
centimeters away. Furthermore, the upper plate CH1 and the lower plate CH2 can be electrically
isolated, in which case they can be used particularly advantageously as a means of generating an
electrostatic field which makes it possible to prevent microdischarges. To that end, said two outer
surfaces CH1 and CH2 facing said corrugated inner surface are provided with a conductive
coating which is made to have a static potential difference determined by a DC voltage generator
E as shown in FIG. 7b. , Perform functions related to their inner surface.
The voltage applied to produce the electrostatic field is on the order of 80 to 100 volts. This
voltage is applied to the plates CH1 and CH2 by means of a resistance R with a value of 100
K.OMEGA. To 1 M.OMEGA. In order to limit the strength of the residual voltage in case of
accidental contact. Generally speaking, the corrugated foam should have teeth of a length at least
equal to the shortest wavelength to be absorbed. The wavelength may be around 30 cm or more.
In a preferred manner, the efficiency of the coating can be improved if the coating 21 of the
corrugated semiconductor foam is bonded to the conductive surfaces of the frame, i.e. the plates
CH1 and CH2. In this case, the absorption appears to be more complete, due to the fact that the
electromagnetic waves are reflected from the corresponding metal wall. In a preferred
embodiment, the coating 21 is comprised of several semiconductive foam plates bonded together
with graphitized paperboard inserted between them. Of course, only the inner surface faces the
electronic circuit CE having a waveform. Graphitized paperboard can be replaced by copper
plates of 0.1 to 0.2 mm thickness. Finally, in one particular embodiment of the device proposed
by the invention, more particularly, against the occurrence of interface microdischarges, in the
situation in which radio interference caused is induced, against radio interference An
embodiment of the device designed for the case where the circuit to be protected is a power
supply is described below. The phenomenon that leads to radio interference caused by the
occurrence of interface microdischarges is that if the equipment part not protected against
interface microdischarges is connected to the device, the frequency of this device is low. Even if it
runs completely, it is particularly problematic. In this case, the electromagnetic waves associated
with the microdischarges are caused to propagate through the connecting conductors, thus
disrupting the connected equipment. In such a case, the device proposed by the present
invention has a set of protected cables CP, as shown in FIG. Each cable is used to connect to the
08-05-2019
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actual stabilized power supply positive terminal and one of the negative terminal or the ground
terminal, the cables to be protected are bundled together and the bundle itself is a sleeve made of
semiconductor foam material , And indicated by reference numeral 20 in FIG. The end of the
sleeve is anchored by a ring or core 21 made of ferromagnetic material in FIG. It is also possible
to insert in the ferrite ring 21 a cable connecting the stabilized power supply to the main power
supply network.
In a preferred embodiment, this ring can have a ground conductor, which is connected to the
ground of the connector part by a shock inductance of suitable impedance or a carbon resistance
of 270 Ω. Furthermore, as schematically shown in FIG. 8, each cable CP to be protected is
connected via an attenuation circuit RC to a cable which makes a ground connection of the
device to supply stabilized power. The attenuation circuit RC may comprise an air capacitor or a
capacitor enclosed in vacuum, the value of which is 100 pf, and the stabilized power supply may
be an air capacitor of a larger value in the range between 100 pf and 500 pf or It is
advantageous because it can be connected by a vacuum capacitor. Finally, the earth conductor of
the stabilized power supply can be grounded at the same level as the connection to the device to
be supplied with a resistance R of approximately the same value. Thus, the attenuating circuits R,
C 'adapt the impedance for microdischarges in differential mode and the resistor R plays the
same role for the common mode. In order to reduce the disturbances caused by the interface
microdischarge in the common mode, in particular the neutral point of the sector is connected to
the terminal adapted to the supply voltage, which isolates the earth of the power supply, and It is
advantageous to find the correct orientation to connect to the mains plug at each part of the
equipment in order to connect to the local ground by means of a resistor R with a value between
50 and 270 as described above. A conventional standard known to those skilled in the art for
finding the orientation in which the outer surface of the transformer is connected to the neutral
point, which is the correct orientation for connecting the grid connector and allows the level of
grid disturb to be reduced. It is possible to proceed using Tests were carried out at the laboratory
of ELECTRICITE DE FRANCE using the device proposed according to the invention. Those tests
are, for example, hi-fi (high fidelity) by simply moving the screen designed to protect the
electronic circuit made of discrete parts as shown in FIGS. 7a and 7b. Emphasized the fact that
the output of the device can be modified considerably. . The following results were obtained by
sequentially moving the screens. -Particularly dull, the tone is rapidly suppressed, the tone is
totally unclear in the worst sense of the word, a faint even sound,-the stretched tone is
suppressed, the signal separation is excellent Sound that can be described as aggressive when the
overall space feel is particularly pleasing, high tone quality-timbre suppression is stretched and
appears to be difficult to separate, the entire experience of the listener is This is a feeling of rapid
distortion that causes the listener to quickly reduce the volume.
The overall interpretation of this phenomenon is described below. For example, an audio signal
08-05-2019
20
transmitted and processed on a hi-fi (high fidelity) device, if it is a music signal, is generally
composed of an atk, the body of the actual signal, and dragging or suppression of the timbre. .
This dragging is probably at an acoustic level of -20 to -40 dB relative to the body of the signal.
This dragging, which is the basis of the musical tone quality of the signal perceived by the
listener, sees its perception largely disturbed by radio interference caused by the interface
microdischarge. In fact, the rest of the signal, or even external causes, produce electromagnetic
waves which are rectified or demodulated by the non-linear elements of the circuit. Non-linear
elements are, for example, solder and bimetal contacts, which result in a broad spectrum of
background noise that is present only when an audio signal is present. In the various situations
mentioned at the beginning of this specification, protection against the occurrence of interface
microdischarges by means of the device proposed by the present invention can be achieved by
attenuating or suppressing the effects of electromagnetic waves caused by said microdischarges.
It will be. Therefore, if the solution recommended and described above can prevent the
occurrence of microdischarges without adversely affecting the operation of the circuit, then
preventing microdischarges from being generated; It makes it possible to prevent the
electromagnetic waves generated by the discharge from approaching the sensitive circuits, and
to absorb said electromagnetic waves at the level of all circuits.
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