FORM 2

THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
[See section 10, Rule 13]
NOISE FILTER;
MITSUBISHI ELECTRIC CORPORATION, A CORPORATION ORGANISED
AND EXISTING UNDER THE LAWS OF JAPAN, WHOSE ADDRESS IS 7-3,
MARUNOUCHI 2-CHOME, CHIYODA-KU, TOKYO 100-8310, JAPAN
THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE
INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED.

2
SPECIFICATION

5
Technical Field
[0001] The present application relates to a noise filter.
Background Art
10 [0002] A noise filter is inserted between an AC power supply and a load device
to reduce noise entering from the power supply to the load device and noise
leaking from the load device to the power supply. In the noise filter, filter
components such as a common mode choke coil and a capacitor are mounted on
a circuit board or a metal mounting plate (for example, refer to Patent
15 Document 1).
Citation List
Patent Document
[0003] Patent Document 1: Japanese Unexamined Utility Model Application
20 Publication H6-38224(paragraphs 0011 to 0016, FIGS. 1 to 3).
Summary of Invention
Problems to be solved by Invention
[0004] However, in a general noise filter including the one in the disclosure of
25 Patent Document 1, an input-side capacitor connected to an AC power supply
and input-side wiring are disposed to face an output-side capacitor connected
to a load device and output-side wiring in close proximity. Further, since
input terminals connected to the AC power supply and output terminals
connected to the load device are disposed in the same phase arrangement order,
30 directions of normal mode noise currents flowing through the line-to-line
capacitors on the input side and the output side are in the same direction to
each other.
3
[0005] Therefore, the magnetic field generated in a current loop formed by the
input-side capacitor and the wiring and the magnetic field generated in a
current loop formed by the output-side capacitor and the wiring reinforce each
other. As a result, owing to the magnetic coupling between the current loop
5 on the input side and the current loop on the output side, a noise propagation
path not through the wiring member is formed, resulting in a problem that the
noise reduction effect is deteriorated.
[0006] The present application is to solve the problem described above and an
object thereof is to obtain a noise filter having an excellent noise reduction
10 effect.
Means for solving Problems
[0007] A noise filter disclosed in the present application includes: a circuit
board; a plurality of input terminals disposed in array arrangement at one end
15 of the circuit board in accordance with a phase line system of an input power
supply; a plurality of output terminals disposed in array arrangement at the
other end in an opposite direction to the one end thereof in accordance with the
plurality of input terminals; a plurality of input-side line-to-line capacitors in
which one end of each thereof is connected to one of the plurality of input
20 terminals and the other ends thereof together are connected to a neutral point;
a plurality of output-side line-to-line capacitors in which one end of each
thereof is connected to one of the plurality of output terminals and the other
ends thereof together are connected to a neutral point; and a choke coil
including a plurality of coils in which one end of each thereof is connected to
25 one of the plurality of input terminals and each of the other ends thereof is
connected to one of the output terminals that is located diagonally with respect
to one of the input terminals in the array arrangement among the plurality of
output terminals.
30 Effect of Invention
[0008] According to the noise filter disclosed in the present application, since
the directions of the normal mode noise currents flowing through the
4
line-to-line capacitors on the input side and the output side are opposite to
each other, generation of a noise propagation path is suppressed, and a noise
filter excellent in a noise reduction effect can be obtained.
5 Brief Description of Drawings
[0009] FIG. 1 is a partially see-through bird’s-eye view showing a configuration
of a noise filter according to Embodiment 1.
FIG. 2 is a circuit diagram showing a circuit configuration of the noise filter
according to Embodiment 1.
10 FIG. 3A and FIG. 3B are a partially see-through top view and a partially
see-through bottom view, respectively, of the noise filter according to
Embodiment 1.
FIG. 4 is a diagram showing normal mode noise attenuation characteristics
for each of the noise filter according to Embodiment 1 and a noise filter
15 according to a comparative example.
FIG. 5A and FIG. 5B are a partially see-through top view and a partially
see-through bottom view, respectively, of a noise filter according to
Embodiment 2.
FIG. 6 is a circuit diagram showing a circuit configuration of a noise filter
20 according to Embodiment 3.
FIG. 7 is a partially see-through bottom view of a noise filter according to
Embodiment 3.
FIG. 8A and FIG. 8B are a partially see-through top view and a partially
see-through bottom view, respectively, of a noise filter according to
25 Embodiment 4.
FIG. 9 is a partially see-through top view of a noise filter according to
Embodiment 5.
FIG. 10A and FIG. 10B are a top view and a bottom view, respectively, of a
noise filter according to Embodiment 6.
30
Modes for carrying out Invention
[0010] Embodiment 1
5
FIG. 1 to FIG. 4 illustrate a noise filter according to Embodiment 1, and FIG.
1 is a partially see-through bird’s-eye view showing a configuration of the noise
filter in which a circuit board is made see-through, and FIG. 2 is a circuit
diagram showing a circuit configuration of the noise filter and a setting region
5 in a spatial arrangement for a part of the configuration. In addition, FIG. 3A
and FIG. 3B are partially see-through top view (FIG 3A corresponding to a
view from the arrow direction A in FIG. 1) and bottom view (FIG. 3B
corresponding to a view from the arrow direction B in FIG. 1) of the noise filter
in which the circuit board is made see-through in the case where the side on
10 which a common mode choke coil is mounted is defined as a top face. FIG. 4 is
a graph showing frequency characteristics (normal mode noise attenuation
characteristics) of the attenuation amount with respect to normal mode noise
in each of the noise filter according to Embodiment 1 and the noise filter
according to the comparative example, as a semi-logarithmic graph of the
15 frequency and the attenuation amount.
[0011] In the noise filter 1 according to Embodiment 1, as shown in FIG. 2,
line-to-line capacitors 3 and 4 are disposed, respectively, in connection wires
connecting the common mode choke coil 5 to input terminals 8 that are
connected to an AC power supply and connection wires connecting the common
20 mode choke coil 5 to output terminals 9 that are connected to a load device.
For example, each of input terminals 8a, 8b, and 8c for a corresponding one of
phases (U, V, W) is disposed on the AC power supply side, and each of the input
terminals 8 is connected to the common mode choke coil 5 (strictly speaking,
coils 52 (FIG. 3A)) by the wires. One end of each of the line-to-line capacitors
25 3a, 3b, and 3c is connected to a corresponding one of the wires connected to the
input terminals 8a, 8b, and 8c, and the other ends of the line-to-line capacitors
3 together are connected to a neutral point.
[0012] Similarly, output terminals 9a, 9b, and 9c for a corresponding one of the
phase (u, v, w) is disposed on a load device side, and each of the output
30 terminals 9 is connected to the common mode choke coil 5 (coils 52) by the
wires. One end of each of the line-to-line capacitors 4a, 4b, and 4c is
connected to a corresponding one of the wires connected to the output
6
terminals 9a, 9b, and 9c, and the other ends of the line-to-line capacitors 4
together are connected to the neutral point. As shown in FIG. 1, FIG. 3A and
FIG. 3B, the input terminals 8a, 8b, and 8c are disposed at intervals on one
end side of the circuit board 2, and the output terminals 9a, 9b, and 9c are
5 disposed at intervals on the other end side of the circuit board 2.
[0013] Further, the common mode choke coil 5 is disposed on the top face 2fa
which is one face of the circuit board 2 such as a printed circuit board provided
with printed wiring, and the line-to-line capacitors 3 and 4 are disposed on a
bottom face 2fb which is the face opposite to the top face 2fa. Thus, a
10 mounting area of wiring members related to the noise filter can be reduced,
and the noise filter 1 can be miniaturized.
[0014] As shown in FIG. 3A, the common mode choke coil 5 includes, for
example, a toroidal core 51 (or a ring core) and the coils 52 wound around the
toroidal core 51, and coil ends are directly connected to printed wiring of the
15 circuit board 2. In this case, when the coil 52 included in the common mode
choke coil 5 is made of a coil having a large wire diameter, the rigidity of the
coil 52 is high, so that the toroidal core 51 wound thereby is disposed on the
circuit board 2 even if it is not supported by a support member or fixed with
resin. Although the common mode choke coil 5 is, strictly speaking, composed
20 of two coils whose winding directions are reversed to each other for each of the
phases, and they are simply referred to as the coil 52 in the description of the
present application.
[0015] Note that the above configuration is the same as a basic configuration of
a general noise filter including the one in Patent Document 1.
25 In contrast, in the noise filter 1 according to each embodiment of the present
invention, wiring members (region Ro) on the load device side are spatially
disposed so as to be in a different phase arrangement order with respect to
wiring members (region Rs) on the AC power supply side shown in FIG. 2.
Specifically, the coils 52 are led out so as to connect diagonally located
30 terminals together such that the phase arrangement order (U, V, W) of the
input terminals 8a, 8b, 8c connected to the AC power source and the phase
7
arrangement order (u, v, w) of the output terminals 9a, 9b, 9c connected to the
load device are reversed.
[0016] The line-to-line capacitors 3, 4 serve to return the normal mode noise
entering from the AC power supply or leaking from the load device, to the
5 noise source. As described above, in the present application, the phase
arrangement order of the input terminals 8a, 8b, and 8c connected to the AC
power supply and the phase arrangement order of the output terminals 9a, 9b,
and 9c connected to the load device are reversed, and the AC power supply and
the load device are connected accordingly to the noise filter 1. Then, with
10 respect to the normal mode noise received from the AC power source or the
load device, the directions of normal mode noise currents flowing through the
line-to-line capacitors 3a, 3b, and 3c and normal mode noise currents flowing
through the line-to-line capacitors 4a, 4b, and 4c are opposite to each other.
[0017] Thus, a magnetic field generated in a current loop of the normal mode
15 noise flowing through the line-to-line capacitors 3a, 3b, and 3c on the AC
power supply side and a magnetic field generated in a current loop of the
normal mode noise flowing through the line-to-line capacitors 4a, 4b, and 4c on
the load device side are cancelled to each other. Therefore, generation of a
noise propagation path that does not pass through the wiring members (filter
20 members) constituting the noise filter 1 is suppressed, and deterioration of the
normal mode noise attenuation characteristics is suppressed.
[0018] Here, a noise filter in which the same filter members as those of the
noise filter 1 of the present application is used but the phase arrangement
order on the AC power supply side and the load device side is the same as the
25 only difference is prepared as a comparative example, and is compared with
the noise filter 1 of the present application in terms of the normal mode noise
attenuation characteristics. As a result, as shown in FIG. 4, the normal mode
noise attenuation characteristic P1 (solid line) of the noise filter 1 of the
present application has a lower attenuation amount in all frequency band of
30 0.1 to 20 MHz than the normal mode noise attenuation characteristic PC
(dashed line) of the noise filter of the comparative example. That is, it is
confirmed that the noise filter 1 of the present application has the better
8
normal mode noise attenuation characteristic than a general noise filter in
which the phase arrangement order is not reversed.
[0019] In the present application, the phase arrangement order of the input
terminals 8a, 8b, and 8c connected to the AC power supply and the phase
5 arrangement order of the output terminals 9a, 9b, and 9c connected to the load
device are reversed in the spatial arrangement. That is, the input terminals
8 and the output terminals 9 located diagonally to each other are connected by
the coils 52 such that each of the line-to-line capacitors 4 on the load device
side facing one of the line-to-line capacitors 3 on the AC power source side is
10 different in the phase. And thus, the directions of the normal mode noise
currents flowing through the line-to-line capacitors 3 on the AC power supply
side and the line-to-line capacitors 4 on the load device side are opposite to
each other, and the magnetic fields generated around them are canceled to
each other. As a result, the generation of the noise propagation path that
15 does not pass through the filter members of the noise filter 1 is suppressed,
and the noise reduction effect that has not been achieved in the prior art can
be achieved.
[0020] Note that, in Embodiment 1, a three phase noise filter inserted and
connected between a three phase AC power supply and a three phase load
20 device is shown as an example, but the present invention is not limited to this,
and a three phase four wire system may be used. Further, for example, a
single phase noise filter inserted and connected between a single phase AC
power supply and a single phase load device may be used, and the same effect
can be obtained by connecting terminals located diagonally to each other
25 regardless of the phase line system. Note that, in each of the following
embodiments, a three phase noise filter will be described as an example in the
same manner as in Embodiment 1, but the noise reduction effect can be
achieved regardless of the phase line system.
[0021] Further, in the noise filter 1 according to Embodiment 1 and
30 Embodiments 2 to 5 described later, the line-to-line capacitors 3 and 4 are
mounted on the opposite side (bottom face 2fb) of the mounting face (top face
2fa) of the common mode choke coil 5. This reduces the mounting area and
9
can meet a demand for the miniaturization. Then, along with the
miniaturization, the interval between the line-to-line capacitors 3 and the
line-to-line capacitors 4 becomes narrower, and noise can be reduced by
suppressing the generation of the noise propagation path, and thus both the
5 miniaturization and the noise reduction can be achieved.
[0022] Embodiment 2
In Embodiment 1, an example is described in which capacitors on the power
supply side and the load side in different phase are arranged to face each other
in the same direction. In the present embodiment, an example will be
10 described in which the orientation of the inter-phase capacitors on the load
side is set in accordance with the state of winding of the common mode choke
coil.
[0023] FIGS. 5A and 5B are a partially see-through top view (corresponding to
a view from the arrow direction A in FIG. 1) and a partially see-through
15 bottom view (corresponding to a view from the arrow direction B in FIG. 1)
respectively in which the circuit board of the noise filter according to
Embodiment 2 is made see-through. The configuration except for the part
related to the orientation of the line-to-line capacitors on the load side of the
noise filter according to Embodiment 2 is the same as the configuration
20 described in Embodiment 1, and thus the circuit diagram of FIG. 2 will be
referred to.
[0024] In the noise filter 1 according to Embodiment 2, as shown in FIG. 5A
and FIG. 5B, the orientation of the line-to-line capacitors 4 on the load device
side is set in accordance with positions of regions Rb of the toroidal core 51 in
25 which the coils 52 of the common mode choke coil 5 are not wound. In the
common mode choke coil 5, as shown in FIG. 5A, one of the coils 52
corresponding to each of the phases (U-u, V-v, W-w) are wound at intervals, so
that the regions Rb in which the coils 52 are not wound in the circumferential
direction occur in the toroidal core 51. Meanwhile, as shown in FIG. 5B, each
30 of the line-to-line capacitors 4 is in columnar shape in which electrodes 43 and
44 are disposed on both ends, and is mounted such that a line D4c that
10
connects both electrodes 43 and 44 and is aligned to the direction of the
displacement current is parallel to the mounting face (bottom face 2fb).
[0025] Then, the common mode choke coil 5 and the line-to-line capacitors 3
and 4 are mounted on the opposite sides to each other across the circuit board
5 2, and one of the regions Rb located at the closest position with respect to the
line-to-line capacitors 3 and 4 is that located right near the line-to-line
capacitors 4 on the load device side. Therefore, the orientation of the
line-to-line capacitors 4 on the mounting face (2fb) are set such that the
tangent line Lt (FIG. 5A) at the midpoint Pm on the outer periphery of the
10 closest one of the regions Rb and the line D4c (FIG. 5B) connecting the
electrodes 43 and 44 are parallel to each other. In the line-to-line capacitors 4,
since the displacement current flows along the line D4c connecting one
electrode 43 to the other electrode 44 on both ends, the direction of the
displacement current and the tangent line Lt is set parallel.
15 [0026] From the one of the regions Rb where the coils 52 are not wound in the
toroidal core 51 of the common mode choke coil 5, a leakage magnetic field is
generated in the same direction as the tangent line Lt at the midpoint Pm on
the outer periphery. In contrast, a magnetic field in the direction that meets
the right-handed screw rule is generated concentrically around the
20 displacement current flowing in the direction of the line D4c between the
electrodes on both ends of the line-to-line capacitor 4. At this time, if the
tangent line Lt and the line D4c are parallel to each other, the leakage
magnetic field generated from the common mode choke coil 5 and the magnetic
field generated around the displacement current between the electrodes 43
25 and 44 of the line-to-line capacitor 4 are interlinked. Therefore, by the
interference between the leakage magnetic field generated from the common
mode choke coil 5 and the magnetic field generated by the displacement
current between the electrodes of the line-to-line capacitor 4, it is possible to
suppress deterioration in the noise reduction effect.
30 [0027] Note that, in Embodiment 2, the line-to-line capacitors 4 on the load
device side are mounted such that the line D4c connecting the electrodes 43
and 44 is parallel to the tangent line Lt at the midpoint Pm on the outer
11
periphery of the closest one of the regions Rb, but this is not the limitation.
For example, when one of the regions Rb is located to be closest to the
line-to-line capacitors 3 on the AC power supply side, the orientation of the
line-to-line capacitors 3 may be set such that a line connecting electrodes
5 formed on both ends of the line-to-line capacitor 3 is parallel to the tangent
line Lt. Alternatively, depending on the arrangement of the regions Rb, both
the line-to-line capacitors 3 and the line-to-line capacitors 4 may be parallel to
the tangent line Lt.
[0028] Embodiment 3
10 In Embodiment 3, regarding the line-to-line capacitors on the load device side,
an example in which a grounding capacitor is added to a neutral connection
point shared by the line-to-line capacitors on the load device side will be
described. FIG. 6 and FIG. 7 illustrate a noise filter according to
Embodiment 3. FIG. 6 is a circuit diagram showing a circuit configuration of
15 the noise filter and a setting region in a spatial arrangement for a part of the
configuration, and FIG. 7 is a partially see-through top view corresponding to
a view from the arrow direction A in FIG. 1, in which a circuit board of the
noise filter is made see-through. Note that the configuration of the noise
filter according to Embodiment 3 is the same as the configuration described in
20 Embodiment 1, except for the part related to the installation of the grounding
capacitor on the load side.
[0029] In the noise filter 1 according to Embodiment 3, as shown in FIG. 6 and
FIG. 7, a grounding capacitor 6 is disposed between the neutral connection
point at the other ends of the line capacitors 4a, 4b and 4c on the load device
25 side and the ground 7 (a ground terminal 6g is shown in FIG. 7). The
grounding capacitor 6 serves to release a common mode noise current to the
ground 7. Therefore, the common mode noise current entering from the AC
power supply is caused to flow to the ground 7 by the grounding capacitor 6,
and thereby the common mode noise entering the load device can be reduced.
30 In addition, by causing the common mode noise current flowing out from the
load device to flow to the ground 7, it is also possible to reduce the common
mode noise flowing out to the AC power supply.
12
[0030] In Embodiment 3, although an example in which one grounding
capacitor 6 is disposed is shown, since the operation is similar to the case in
which a grounding capacitor having a capacitance of one third is disposed
between each phase on the load device side and the ground 7, the number of
5 parts can be reduced and the noise filter 1 can be miniaturized. Further,
since each of the line-to-line capacitors 4a, 4b, and 4c on the load device side
for the countermeasure to the normal mode noise is only the capacitance
connected between the lines, the capacitances of the line-to-line capacitors 4a,
4b, and 4c do not change even if the grounding capacitor 6 for the
10 countermeasure to the common mode noise exists.
[0031] The setting of the capacitance of the grounding capacitor 6 in
Embodiment 3 will now be described. When a combined capacitance of the
line-to-line capacitors 4a, 4b, and 4c on the load device side and the grounding
capacitor 6 is denoted as C_XY, the following formula (1) holds among a
15 leakage current I, an input voltage V, and a frequency f of the input voltage.
C_XY = I / (2 π fV) ••• (1)
[0032] That is, the combined capacitance C_XY of the line-to-line capacitors 4a,
4b, 4c and the grounding capacitor 6 on the load device side is determined by a
specified value of the leakage current I different for each load device, the input
20 voltage V, and the frequency f of the input voltage. Thus, the capacitance of
the grounding capacitor 6 is set so that the combined capacitance C_XY along
with the line-to-line capacitors 4a, 4b, and 4c on the load device side satisfies
the formula (1).
[0033] Note that, in Embodiment 3, the grounding capacitor 6 is disposed
25 between the line capacitors 4a, 4b and 4c on the load device side and the
ground 7, but this is not a limitation. For example, the grounding capacitor
may be disposed between the line-to-line capacitors 3a, 3b, and 3c on the AC
power supply side and the ground 7 or may be disposed on the both sides.
Further, since each of the line-to-line capacitors 3a, 3b, and 3c on the AC power
30 supply side for the countermeasure to the normal mode noise is only the
capacitance connected between the lines, the capacitances of the line-to-line
13
capacitors 3a, 3b, and 3c on the AC power supply side do not change even if the
grounding capacitor for the countermeasure to the common mode noise exists.
[0034] Embodiment 4
In Embodiment 3, the example is shown in which the grounding capacitor is
5 disposed between the neutral connection point shared by the line-to-line
capacitors and the ground. In Embodiment 4, an example will be described in
which the orientation of the grounding capacitor is set in accordance with the
state of winding of the common mode choke coil.
[0035] FIG. 8A and FIG. 8B are respectively a partially see-through top view
10 (corresponding to a view from the arrow direction A in FIG. 1) and a partially
see-through bottom view (corresponding to a view from the arrow direction B
in FIG. 1) in which the circuit board of the noise filter according to
Embodiment 4 is made see-through. Note that the configuration except for
the part related to the orientation of the grounding capacitor of the noise filter
15 according to Embodiment 4 is the same as the configuration described in
Embodiment 3, and thus the circuit diagram of FIG. 6 will be referred to.
[0036] In the noise filter 1 according to Embodiment 4, as shown in FIG. 8A
and FIG. 8B, the orientation of the grounding capacitor 6 is set in accordance
with a position of one of the regions Rb of the toroidal core 51 in which the coils
20 52 of the common mode choke coil 5 are not wound. The regions Rb in the
common mode choke coil 5 in which the coils 52 are not wound in the
circumferential direction are the same as Embodiment 2. Meanwhile, as with
the line-to-line capacitors 4 described in Embodiment 2, the line-to-line
capacitors 6 are in columnar shape in which electrodes 63 and 64 are disposed
25 on both ends, and is mounted such that a line D6c connecting both electrodes
63 and 64 is parallel to the mounting face (bottom face 2fb).
[0037] At this time, one of the regions Rb located closest to the grounding
capacitor 6 is that located on the load device side. Therefore, the orientation
of the grounding capacitor 6 on the mounting face (2fb) is set such that the
30 tangent line Lt at the midpoint Pm on the outer periphery of the closest one of
the regions Rb and the line D6c connecting both electrodes 63 and 64 are
parallel to each other. In the grounding capacitor 6, as in the case of the
14
line-to-line capacitors 4 described in Embodiment 2, the displacement current
flows along the line D6c connecting one electrode 63 to the other electrode 64
on both ends, so that the directions of the displacement current and the
tangent line Lt are parallel to each other.
5 [0038] In the toroidal core 51 of the common mode choke coil 5, a leakage
magnetic field is generated in the same direction as the tangent line Lt at the
midpoint Pm on the outer periphery from one of the regions Rb where the coils
52 are not wound. Meanwhile, between the electrodes on both end faces of
the grounding capacitor 6, a magnetic field in the direction that meets the
10 right-handed screw rule is generated concentrically around the displacement
current flowing in the direction of the line D6c connecting the electrodes 63
and 64. At this time, if the tangent line Lt and the line D6c are parallel to
each other, the leakage magnetic field generated from the common mode choke
coil 5 and the magnetic field generated around the displacement current
15 between the electrodes 63 and 64 of the grounding capacitor 6 are interlinked.
Therefore, by the interference between the leakage magnetic field generated
from the common mode choke coil 5 and the magnetic field generated by the
displacement current between the electrodes of the grounding capacitor 6, it is
possible to suppress deterioration of the noise reduction effect.
20 [0039] Note that, in Embodiment 4, the line D6c connecting the electrodes 63
and 64 of the grounding capacitor 6 disposed between the line-to-line
capacitors 4c on the load device side and the ground 7 is parallel to the tangent
line Lt at the midpoint Pm of one of the regions Rb in the common mode choke
coil 5. This is not a limitation. For example, when one of the regions Rb is
25 located to be closest to the line-to-line capacitors 3 on the AC power supply side
and the grounding capacitor is disposed on the line-to-line capacitors 3 side,
the orientation of the grounding capacitor may be set such that a line
connecting the electrodes formed on both ends thereof is parallel to the
tangent line Lt. Alternatively, depending on the arrangement of the regions
30 Rb, both the grounding capacitors on the sides of the line-to-line capacitors 3
and the line-to-line capacitors 4 may be parallel to the tangent line Lt. In
some cases, as described in Embodiment 2, the line connecting each of the
15
electrodes in the line-to-line capacitors 3 and 4 may be parallel to the tangent
line Lt.
[0040] Embodiment 5
In each of the embodiments describe above, the description is made using the
5 diagrams in which a pin shape is expected in use for the input terminals and
the output terminals, but the terminal shape is not limited to this. In
Embodiment 3, an example in which a screw fastening structure is formed in
the input terminals and the output terminals will be described. FIG. 9 is a
partially see-through top view corresponding to a view from the arrow
10 direction A in FIG. 1, in which a circuit board of a noise filter according to
Embodiment 5 is made see-through. Note that the configuration of the noise
filter according to Embodiment 5 except for the input terminals and the load
terminals are the same as that described in each embodiment.
[0041] As shown in FIG. 9, in the noise filter 1 according to Embodiment 5, the
15 input terminals 8a, 8b, and 8c and the output terminals 9a, 9b, and 9c are
respectively provided with screw parts 81 and 91 in contrast to FIG. 3A used in
the description of Embodiment 1. More specifically, the screw parts 81 and 91
have openings at least on the side of the top face 2fa and thus are provided
with screw holes in which screws can be fastened. A region (not shown) for
20 soldering is provided on the bottom face 2fb side.
[0042] Even with such a structure, it is possible to obtain the same effects as
those of the noise filter 1 shown in each of the embodiments described above.
This configuration can facilitate connection of the common mode choke coil 5 to
the circuit board 2 and connection of the AC power supply and the load device
25 to the noise filter 1. In Embodiment 5, although the input terminals 8a, 8b,
and 8c and the output terminals 9a, 9b, and 9c are provided on the placement
(top face 2fa) side of the common mode choke coil 5, this is not the limitation
and they may be provided on the opposite face (bottom face 2fb) side. Further,
not only the screw holes but also press-fit terminals, connection ports for the
30 press-fit terminals, or quick-connect terminals in which connection can be
made just by insertion of an electric wire may be used.
[0043] Embodiment 6
16
In each of the embodiments described above, an example is shown in which
the common mode choke coil and the line-to-line capacitors are disposed on the
opposite sides of the circuit board to each other in order to reduce the
mounting area, but the present invention is not limited thereto.
5 In Embodiment 6, the common mode choke coil and the line-to-line capacitors
are mounted on the same face of the circuit board. FIGS. 10A and 10B are a
top view (corresponding to a view from the arrow direction A in FIG. 1) and a
bottom view (corresponding to a view from the arrow direction B in FIG. 1) in
the noise filter according to Embodiment 6, respectively. The configuration of
10 the noise filter according to Embodiment 6 is the same as that of the other
embodiments except for the part related to the arrangement of components in
the noise filter, and for example, the circuit configuration is the same as that of
FIG. 2 described in Embodiment 1.
[0044] In the noise filter 1 according to Embodiment 6, as shown in FIG. 10A
15 and FIG. 10B, the common mode choke coil 5 and the line-to-line capacitors 3
and 4 are disposed on the same face (top face 2fa) of the circuit board 2. And
wiring (wiring pattern) to the input terminals 8 and the output terminals 9 is
different from that in Embodiment 1 and has the following configuration.
[0045] As wiring patterns on the side of the input terminals 8, as shown in FIG.
20 10A, patterns 82 and patterns 83 disposed for each of the phases and a pattern
84 shared by each phase are formed on the side of the top face 2fa. To the
patterns 83, each of the phases of the common mode choke coil 5 and one end of
each of the line-to-line capacitors 3a, 3b, and 3c are connected, and the other
ends of the line-to-line capacitors 3 are collectively connected to the pattern 84
25 as a neutral point. And as shown in FIG. 10B, patterns 85 which are disposed
for each of the phases and electrically connected to the respective patterns 82
and the respective patterns 83 on the side of the top face 2fa by penetration
through the circuit board 2 are formed on the side of the bottom face 2fb.
[0046] Similarly, as wiring patterns on the side of the output terminals 9,
30 patterns 92 and patterns 93 disposed for each of the phases and a pattern 94
shared by each phase are formed on the side of the top face 2fa. To the
patterns 93, each of the phases of the common mode choke coil 5 and one end of
17
each of the line-to-line capacitors 4a, 4b, and 4c are connected, and the other
ends of the line-to-line capacitors 4 are collectively connected to the pattern 94
as a neutral point. And patterns 95 which are disposed for each of the phases
and electrically connected to the respective patterns 92 and the respective
5 patterns 93 on the side of the top face 2fa by penetration through the circuit
board 2 are formed on the side of the bottom face 2fb
[0047] Thus, although the spatial arrangement of the line-to-line capacitors 3
and 4 with respect to the common mode choke coil 5 is different from that of
the noise filter 1 of Embodiment 1, the circuit as the noise filter 1 is the same
10 as that in FIG. 2 and equivalent thereto. In addition, since the input
terminals 8 and the output terminals 9 located diagonally to each other are
connected by the coils 52, the phase order in the line-to-line capacitors 4
opposed to the line-to-line capacitors 3 are reversed as in the noise filter 1 of
Embodiment 1.
15 [0048] Thus, the magnetic field generated in a current loop of the normal mode
noise flowing through the line-to-line capacitors 3a, 3b, and 3c on the AC
power supply side and the magnetic field generated in a current loop of the
normal mode noise flowing through the line-to-line capacitors 4a, 4b, and 4c on
the load device side are cancelled to each other. As a result, as with
20 Embodiment 1, generation of a noise propagation path that does not pass
through the wiring members (filter members) constituting the noise filter 1 is
suppressed, and deterioration of the normal mode noise attenuation
characteristics is suppressed.
[0049] Note that, although various exemplary embodiments and examples are
25 described in the present specification, various features, aspects, and functions
described in one or more embodiments are not inherent in a particular
embodiment and can be applicable alone or in their various combinations to
each embodiment. Accordingly, countless variations that are not illustrated
are envisaged within the scope of the art disclosed herein. For example, the
30 case where at least one component is modified, added or omitted, and the case
where at least one component is extracted and combined with a component in
another embodiment are included.
18
[0050] For example, the configuration in Embodiment 6 in which the common
mode choke coil 5 and the line-to-line capacitors 3 and 4 are disposed on one
side is not limited to Embodiment 1, but can be applied to the configurations
described in Embodiments 2 to 5 to obtain the same noise reduction effect as
5 those obtained in each embodiment. Further, an example in which the
common mode choke coil 5 is used as a choke coil is shown. However, this is
not a limitation. Even in a choke coil in which a normal mode choke coil is
included, generation of a noise propagation path not passing through the
wiring members (filter members) is suppressed, and deterioration of normal
10 mode noise attenuation characteristics is suppressed.
[0051] As described above, the noise filter 1 configured according to each
embodiment includes the circuit board 2, the plurality of input terminals 8
disposed in array arrangement at one end of the circuit board 2 in accordance
with the phase line system of the input power supply (AC power supply), the
15 plurality of output terminals 9 is disposed in array arrangement at the other
end in an opposite direction to the one end of the circuit board 2 in accordance
with the plurality of input terminals 8, the plurality of line-to-line capacitors
(line-to-line capacitors 3) on the input side in which one end of each thereof is
connected to one of the plurality of input terminals 8 and the other ends
20 thereof together are connected to the neutral point, the plurality of line-to-line
capacitors (line-to-line capacitors 4) on the output side in which one end of
each thereof is connected to one of the plurality of output terminals 9 and the
other ends thereof together are connected to the neutral point, and the
common mode choke coil 5 (choke coil including normal mode choke coil)
25 having the plurality of coils 52 with one end of each thereof connected to one of
the plurality of input terminals 8 and each of the other ends thereof connected
to one of the output terminals 9a, 9b, and 9c that is located diagonally with
respect to one of the input terminals 8a, 8b, and 8c (the order of array
arrangement is reversed) in the array arrangement (of terminals) among the
30 plurality of output terminals 9.
Therefore, the directions of the normal mode noise currents flowing through
the line-to-line capacitors 3 on the input side and the line-to-line capacitors 4
19
on the output side are opposite to each other, generation of a noise propagation
path not through the filter members is suppressed, and the noise filter 1
excellent in noise reduction effect can be obtained.
[0052] In particular, if the plurality of input-side line-to-line capacitors 3 and
5 the plurality of output-side line-to-line capacitors 4 are mounted on the face
(bottom face 2fb) of the circuit board 2 opposite to the face (top face 2fa, for
example) on which the common mode choke coil 5 is mounted, the mounting
area can be reduced, and the demand for miniaturization can be met. With
further miniaturization, if the interval between the line-to-line capacitors 3
10 and 4 is narrower, the noise can be reduced by suppressing generation of the
noise propagation path, and both miniaturization and noise reduction can be
achieved.
[0053] If at least either the plurality of line-to-line capacitors 3 on the input
side or the plurality of line-to-line capacitors 4 on the output side is in
15 columnar shape in which the electrodes (for example, electrodes 43, 44) are
disposed on both ends, and the line (for example, line D4c) connecting the
electrodes on both ends is arranged in parallel with the tangent line Lt at the
midpoint Pm on the outer periphery of one of the regions Rb where the coils 52
are not wound in the circumferential direction in the ring-shaped core (toroidal
20 core 51) constituting the common mode choke coil 5, the leakage magnetic field
generated from the common mode choke coil 5 and the magnetic field
generated around the displacement current between the electrodes in the
line-to-line capacitors 4 or the line-to-line capacitors 3 are interlinked.
Therefore, by the interference between the leakage magnetic field generated
25 from the common mode choke coil 5 and the magnetic field generated by the
displacement current between the electrodes in the line-to-line capacitors 4 or
the line-to-line capacitors 3,, it is possible to suppress deterioration of the
noise reduction effect.
[0054] Further, if the grounding capacitor 6 is provided in which one end
30 thereof is grounded and the other end thereof is connected to the neutral point
to which the other ends of the plurality of line-to-line capacitors 3 on the input
side or the plurality of line-to-line capacitors 4 on the output side are
20
connected together, the common mode noise current entering from the AC
power supply is caused to flow to the ground 7 by the grounding capacitor 6,
and thereby the common mode noise entering the load device can be reduced.
Or, by causing the common mode noise current flowing out from the load
5 device to flow to the ground 7, it is also possible to reduce the common mode
noise flowing out to the AC power supply.
[0055] Further, the grounding capacitor 6 is in columnar shape in which the
electrodes 63, 64 are disposed on both ends thereof, and if the line D6c
connecting the electrodes 63, 64 on both ends is arranged in parallel with the
10 tangent line Lt at midpoint Pm on the outer periphery of one of the regions Rb
where the coils 52 are not wound in the circumferential direction in the
ring-shaped core (toroidal core 51) constituting the common mode choke coil 5,
by the interference between the leakage magnetic field generated from the
common mode choke coil 5 and the magnetic field generated by the
15 displacement current between the electrodes of the grounding capacitor 6, it is
possible to suppress deterioration of the noise reduction effect.
Description of Reference Numerals and Signs
[0056] 1 : noise filter, 2 : circuit board, 2fa :top face, 2fb : bottom face, 3, 3a, 3b,
20 3c : line-to-line capacitor (input side line-to-line capacitor), 4, 4a, 4b, 4c :
line-to-line capacitor (output side line-to-line capacitor), 5 : common mode
choke coil (choke coil), 51 : toroidal core, 52 : coil, 8, 8a, 8b, 8c : input terminal,
9, 9a, 9b, 9c : output terminal, 6 : grounding capacitor, 6g : ground terminal,
7 : ground, D4c, D6c : line (connecting electrodes), Lt : tangent line, Pm :
25 midpoint, Rb : region.

21
We Claim :

1. A noise filter comprising:
a circuit board;
5 a plurality of input terminals disposed in array arrangement at one
end of the circuit board;
a plurality of output terminals disposed in array arrangement at the
other end in an opposite direction to the one end thereof in accordance with the
plurality of input terminals;
10 a plurality of input-side line-to-line capacitors in which one end of each
thereof is connected to one of the plurality of input terminals and the other
ends thereof together are connected to a neutral point;
a plurality of output-side line-to-line capacitors in which one end of
each thereof is connected to one of the plurality of output terminals and the
15 other ends thereof together are connected to a neutral point; and
a choke coil including a plurality of coils in which one end of each
thereof is connected to one of the plurality of input terminals and each of the
other ends thereof is connected to one of the output terminals that is located
diagonally with respect to one of the input terminals in the array arrangement
20 among the plurality of output terminals.

2. The noise filter according to claim 1, wherein a common mode choke coil is
used as the choke coil.
25 3. The noise filter according to claim 1 or 2, wherein the plurality of input-side
line-to-line capacitors and the plurality of output-side line-to-line capacitors
are mounted on a face of the circuit board opposite to a face on which the choke
coil is mounted.
30 4. The noise filter according to any one of claims 1 to 3, wherein at least either
the plurality of input-side line-to-line capacitors or the plurality of output-side
line-to-line capacitors are in columnar shape in which electrodes are disposed
22
on both ends each thereof, and a line connecting the electrodes on both ends is
directed so as to be parallel to a tangent line at a midpoint on an outer
periphery of a region in which the coils are not wound in a circumferential
direction in a ring-shaped core constituting the choke coil.
5
5. The noise filter according to any one of claims 1 to 4, further comprising a
grounding capacitor in which one end thereof is grounded and the other end
thereof is connected to the neutral point to which the other ends of the
plurality of input-side line-to-line capacitors or the plurality of output-side
10 line-to-line capacitors are connected together.
6. The noise filter according to claim 5, wherein
the grounding capacitor is in columnar shape in which electrodes are
disposed on both ends thereof, and
15 a line connecting the electrodes on both ends is directed so as to be in
parallel with a tangent line at a midpoint on an outer periphery of a region
where the coils are not wound in a circumferential direction of the ring-shaped
core constituting the choke coil.