JP5692903B2 - High frequency noise filter for vehicle equipment and filter connection method - Google Patents

Description

  The present invention relates to a high-frequency noise filter for on-vehicle equipment and a filter connection method, and is used, for example, to reduce high-frequency noise generated in a frequency band of radio broadcasting.

  For example, when receiving and listening to radio waves of medium wave broadcasting (AM (amplitude modulation) broadcasting in a frequency band of 520 kHz to 1650 kHz) with an in-vehicle radio receiver, the frequency of high-frequency electromagnetic noise generated from equipment on the vehicle is broadcast. Since it overlaps with the frequency band, this noise is received by the antenna of the in-vehicle radio receiver, noise is mixed into the received broadcast, and noise appears in the sound output from the speaker.

  Since various devices, switches, and the like that perform current switching are mounted around the engine or the like on the vehicle, these serve as noise sources and generate high-frequency electromagnetic noise. In addition, a rear defogger (condensation preventer for the rear window), a high-mount stop lamp, and the like often exist in the vicinity of the antenna for the vehicle-mounted radio.

  Accordingly, high-frequency electromagnetic noise generated by a noise source on the vehicle propagates to a load such as a rear defogger or a high-mount stop lamp via the power line. And the electromagnetic noise radiated | emitted from such a load is received by the antenna which exists in the vicinity, and mixes with the input for vehicle-mounted radios, and has a bad influence.

  Therefore, in order to reduce high-frequency noise radiation, a noise filter is generally inserted in a power supply line connected to a load such as a rear defogger through which noise propagates (Patent Document 1). A noise filter used for such an application is configured by a single capacitor in appearance, but since this capacitor has a residual inductance inside, equivalently, the capacitance of one capacitor ( A capacitance) component (C) and a residual inductance component (L) are connected in series to form a self-resonant trap filter. In other words, the impedance of the circuit decreases near the resonance frequency. By connecting this noise filter between the power line and ground, only the high-frequency noise component near the resonance frequency is filtered and radiated electromagnetic waves (noise) ) Is reduced.

  Further, as other conventional techniques related to this type of noise filter, for example, Patent Document 2 and Patent Document 3 are known. Patent Document 2 proposes a configuration in which a bobbin case that simultaneously accommodates a core and a connector terminal is provided in an air core portion of a coil, and the coil and the connector terminal are directly joined. Thereby, the filter portion and the connector portion are integrated, and variation in impedance characteristics is suppressed, and miniaturization and cost reduction are realized. Patent Document 3 proposes that a noise filter using a capacitor similar to that in Patent Document 1 is built in the joint connector to reduce the amount of wiring and the number of wiring work.

JP 2006-238529 A JP 2009-54713 A JP 2009-146570 A

  By the way, in the case of a self-resonant trap filter using a capacitor as shown in Patent Document 1 or Patent Document 3, a power supply line (usually a + 12V line) connected to a load such as a rear defogger is filtered. It is necessary to connect one end of a capacitor and connect the other end of the capacitor to ground.

  In an automobile, a vehicle body generally made of a metal such as iron is electrically connected to a negative electrode such as a battery or a generator that is a power source mounted on the vehicle, that is, a ground terminal. Therefore, for example, if a metal bracket connected to the other end (ground side terminal) of the capacitor, which is a filter, is fixed to the vehicle body using a bolt or the like, as in the joint connector disclosed in Patent Document 3, this is all that is required. A capacitor can be connected to ground.

  However, in recent years, automobiles having various structures exist, and there are many cases where a conductor electrically connected to a vehicle body as a ground is not exposed to the outside. Therefore, for example, when a capacitor type filter is to be connected to the power line of the rear defogger on the vehicle, when the conductor on the vehicle body side is not exposed in the vicinity of the rear defogger, the bracket connected to the capacitor is attached to the vehicle body. It cannot be fixed. Therefore, an electric wire connected to the ground terminal of the capacitor is added, this electric wire is extended to the position where the conductor connected to the ground of the vehicle body exists, and the tip of the electric wire is fixed to the conductor to connect to the ground Will be realized.

  However, if an electric wire is added for ground connection, the electrical characteristics of the filter will fluctuate. Specifically, the substantial resonance frequency of the filter changes under the influence of the added electric wire. For example, as shown in FIG. 4, the characteristics of the attenuation amount of the capacitor type filter are maximized at the attenuation pole frequency that is the resonance point, and the attenuation amount decreases as the distance from the attenuation pole frequency increases and decreases. If the resonance frequency changes due to the addition of the electric wire, a desired noise reduction effect cannot be obtained in the frequency band assumed in the design.

  That is, for example, even though a filter designed to obtain a sufficient attenuation over the entire frequency band of 520 kHz to 1650 kHz is connected, the resonance frequency changes due to the addition of the electric wire, and the frequency band of 520 kHz to 1650 kHz. A large amount of electromagnetic noise is radiated, and this is mixed into the input of the in-vehicle radio via the antenna.

  The present invention has been made in view of the above-described circumstances, and its purpose is that even when the conductor connected to the ground is not exposed near the load on the vehicle that radiates electromagnetic noise, An object of the present invention is to provide a high-frequency noise filter for on-vehicle equipment and a filter connection method capable of obtaining a sufficient attenuation amount in a frequency band assumed at the time of design.

In order to achieve the above-described object, the high-frequency noise filter for on-vehicle equipment according to the present invention is characterized by the following (1) to (4).
(1) A high-frequency noise filter for on-vehicle equipment configured by a self-resonant filter that forms a resonance circuit in which a capacitor component and an inductor component are connected in series,
One end side of the self-resonant filter can be electrically connected to a power line connecting one end of the in-vehicle DC power source and one end of the load of the in-vehicle device, and the other end side of the self-resonant filter can be grounded. And electrically connectable to the other end of the load,
A first connection terminal connected to a first electrode on one end side of the self-resonant filter and connecting a part of the power supply line to the first electrode;
A second connection terminal connected to the second electrode on the other end side of the self-resonant filter, and connecting the other end of the load and the earth to the second electrode;
With
The second connection terminal is provided with two electrodes connected to the ground and the other end of the load.
(2) The high-frequency noise filter for on-vehicle equipment according to (1) above,
At least one of the first connection terminal and the second connection terminal includes a plurality of external electrodes drawn from different locations on the outer periphery of the electrically insulating case surrounding the self-resonant filter.
(3) The high-frequency noise filter for on-vehicle equipment according to (1) above,
At least one of the first connection terminal and the second connection terminal includes a plurality of external electrodes drawn from the same location on the outer periphery of the electrically insulating case surrounding the self-resonant filter.
(4) The high-frequency noise filter for on-vehicle equipment according to (1) above,
At least one of the one end side of the self-resonant filter and the other end side of the self-resonant filter is drawn from the outer periphery of an electrically insulating case surrounding the self-resonant filter.

According to the high-frequency noise filter for on-vehicle equipment having the configuration (1) above, it is possible to prevent the resonance frequency of the filter from changing even when an additional wire is used for ground connection. is there. Therefore, even when the conductor connected to the ground is not exposed near the load on the vehicle that radiates electromagnetic noise, a sufficient amount of attenuation can be obtained in the frequency band assumed at the time of design.
According to the high-frequency noise filter for in-vehicle devices having the configuration ( 2 ), a plurality of electric wires can be simultaneously connected to the first connection terminal and / or the second connection terminal. By connecting a plurality of electric wires to the ground-side terminal, the load-side terminal and the power-supply-side ground electrode can be independently connected via these.
According to the on-vehicle equipment high frequency noise filter having the configuration ( 3 ), a plurality of electric wires can be simultaneously connected to the first connection terminal and / or the second connection terminal. By connecting a plurality of electric wires to the ground-side terminal, the load-side terminal and the power-supply-side ground electrode can be independently connected via these.
According to the high-frequency noise filter for on-vehicle equipment having the configuration ( 4 ), the filter can be connected to the electric wire in a state where the self-resonant filter is accommodated in the case.

In order to achieve the above-mentioned object, the filter connection method according to the present invention is characterized by the following ( 5 ).
( 5 ) A filter connection method for reducing high-frequency noise by connecting a self-resonant filter that forms a resonance circuit in which a capacitor component and an inductor component are connected in series between an in-vehicle DC power source and a load of an in-vehicle device Because
Connect one end of the self-resonant filter to a power line connecting one end of the in-vehicle DC power source and one end of the load,
The other end of the load is connected to the other end of the self-resonant filter via a predetermined first electric wire without being grounded, and the first electric wire and the other end of the self-resonant filter are connected to each other. The ground connection point is formed in the vicinity of the other connection point on the ground side of the in-vehicle DC power supply from the connection point via a predetermined second electric wire from the connection point.

According to the filter connection method of the above configuration ( 5 ), even if the conductor connected to the ground is not exposed near the load on the vehicle that radiates electromagnetic noise, the first electric wire and By connecting the ground side using the second electric wire, a sufficient attenuation can be obtained in the frequency band assumed at the time of design.

  According to the high-frequency noise filter for in-vehicle equipment and the filter connection method of the present invention, even if the conductor connected to the ground is not exposed near the ground of the filter itself, the frequency band assumed at the time of design is sufficient. Attenuation is obtained.

  The present invention has been briefly described above. Further, details of the present invention will be further clarified by reading through the modes for carrying out the invention described below with reference to the accompanying drawings.

It is a wiring diagram of the electric circuit of the vehicle equipment which shows the example of a connection of the noise filter in embodiment. FIG. 2 is an electric circuit diagram illustrating an equivalent circuit corresponding to the connection example illustrated in FIG. 1. It is a wiring diagram which shows the structure of two types of high frequency noise filters for vehicle equipment of embodiment. It is a graph which shows the specific example of the attenuation amount-frequency characteristic when a noise filter is connected. It is a wiring diagram of the electric circuit of the vehicle equipment which shows the example of a connection of the conventional noise filter. FIG. 6 is an electric circuit diagram illustrating an equivalent circuit corresponding to the connection example illustrated in FIG. 5. It is a front view which shows the external appearance of the noise filter of a prior art example.

  Specific embodiments relating to the high-frequency noise filter for automotive devices and the filter connection method of the present invention will be described below with reference to the drawings.

  Configurations of two types of high-frequency noise filters 10A and 10B for in-vehicle devices that are embodiments of the present invention are shown in FIG. In FIG. 3, elements corresponding to each other are shown with the same reference numerals. Each of the high-frequency noise filters 10A and 10B for in-vehicle devices shown in FIG. 3 is configured mainly by one filter element 11.

  This filter element 11 is a capacitor (capacitor) type self-resonant filter, and looks like a single capacitor. However, like the equivalent circuit shown in FIG. 2, the capacitor (C: 2 μF, for example) A resonance circuit is formed in which an electrostatic capacitance component and an inductor (L) component are connected in series. That is, since the impedance between both ends of the filter element 11 becomes small in a frequency band (for example, 520 kHz to 1650 kHz) in the vicinity of the resonance frequency of the resonance circuit, high-frequency noise including components in the corresponding frequency band can be attenuated. it can.

  As shown in FIG. 3, the filter elements 11 of the on-vehicle equipment high-frequency noise filters 10A and 10B are covered and fixed in a filter case 12 made of an electrically insulating material (for example, resin). .

  As for the high frequency noise filter 10 </ b> A for in-vehicle equipment, as shown in FIG. 3, two external electrodes 13 and 14 are electrically connected to the first electrode 11 a that is one end of the filter element 11. Further, the two external electrodes 13 and 14 are arranged so as to be exposed to the outer surface of the filter case 12 from different locations. Two external electrodes 15 and 16 are also electrically connected to the second electrode 11 b which is the other end of the filter element 11. Further, the two external electrodes 15 and 16 are arranged so as to be exposed on the outer surface of the filter case 12 from different locations.

  As for the other on-vehicle equipment high frequency noise filter 10B, as shown in FIG. 3, the first electrode 11a, which is one end of the filter element 11, has a first connection terminal exposed on the outer surface of the filter case 12. 17 is connected. The second connection terminal 18 exposed on the outer surface of the filter case 12 is connected to the second electrode 11 b which is the other end of the filter element 11. The first connection terminal 17 is provided with two external electrodes 17a and 17b, and the second connection terminal 18 is provided with two external electrodes 18a and 18b.

  Therefore, when the on-vehicle equipment high-frequency noise filter 10 </ b> A shown in FIG. 3 is used, both the external electrodes 13 and 14 can be used as terminals for connection to the first electrode 11 a of the filter element 11. Moreover, both the external electrodes 15 and 16 can be utilized as a terminal for connecting with the 2nd electrode 11b. That is, an electric wire can be connected to each part of the external electrodes 13, 14, 15 and 16.

  Similarly, when using the on-vehicle equipment high-frequency noise filter 10B shown in FIG. 3, both the external electrodes 17a and 17b can be used as terminals for connection to the first electrode 11a of the filter element 11. Further, both the external electrodes 18a and 18b can be used as terminals for connection to the second electrode 11b. That is, an electric wire can be connected to each part of the external electrodes 17a, 17b, 18a and 18b.

  In the embodiment of the present invention described with reference to FIG. 3, the first electrode 11 a, the external electrodes 13, 14, and the first electrode 11 are electrically connected to the power line 31 at one end of the filter element 11. Using the member of the connection terminal 17, the other end of the filter element 11 can be grounded, and the second electrode 11 b, the external electrodes 15 and 16, and the second electrode can be electrically connected to the other end 22 b of the load 22. The member of the connection terminal 18 was used. Thereby, the filter element 11 can be connected to the electric wire in a state where the self-resonant filter is accommodated in the filter case 12. However, these members are not essential for carrying out the present invention. One end side of the filter element 11 can be electrically connected to a power line 31 that connects one end of the in-vehicle DC power source 21 and one end 22a of the load 22 of the in-vehicle device, and the other end side of the filter element 11 can be grounded. It only needs to be electrically connectable to the other end 22 b of the load 22. For example, at least one of the one end side of the filter element 11 and the other end side of the filter element 11 may be drawn from the outer periphery of the filter case 12.

  A connection example (connection diagram) of a noise filter to which the filter connection method of the present invention is applied is shown in FIG. In addition, although the above-mentioned high frequency noise filter 10A for vehicle equipment is used in FIG. 1, the high frequency noise filter 10B for vehicle equipment can also be used instead.

  In FIG. 1, it is assumed that electromagnetic noise affecting the electric circuit of the in-vehicle device is reduced. In other words, various electric devices are mounted on the vehicle as in-vehicle devices, and often include a switching circuit such as an inverter that repeats large current switching at high speed, a relay, a switch, and the like. Such a switching circuit or the like serves as a noise source and generates high-frequency noise of various frequencies.

  Such a noise source 23 is directly connected to the power line 31 of the in-vehicle DC power source 21 as shown in FIG. 1 or a wire harness (not shown) arranged in the vicinity of the power line 31. Often connected. Therefore, high frequency noise generated at the noise source 23 propagates to various in-vehicle devices via the power supply line 31.

  For example, in-vehicle radio receiver antennas often exist in the vicinity of a hot wire or a high-mount stop lamp that is a load of a rear defogger mounted on a vehicle. Therefore, the high frequency noise generated in the noise source 23 propagates to the rear defogger or the like via the power supply line 31 and is radiated as electromagnetic noise from the portion of the hot wire that is the load, and this is transmitted to the vehicle-mounted radio receiver via the antenna. Mixed into the input.

  Therefore, in order to reduce electromagnetic noise radiated from the rear defogger, etc., it is common to connect a capacitor (capacitor) type self-resonant filter between the power supply line and the earth line near the load. is there. Thereby, since the amplitude of high-frequency electromagnetic noise close to the resonance frequency of the filter is attenuated before the load, the electromagnetic noise radiated from the load is reduced.

  For such applications, a noise filter CF having a configuration as shown in FIG. 7 is generally used. The noise filter CF includes a filter element (capacitor) that forms a resonance circuit in which a capacitor (C) component and an inductor (L) component are connected in series, and includes terminals 41 and 42 and a ground bracket 43. ing. That is, the terminal 41 is connected to the power supply line, and the terminal 42 is connected to the load. Further, the metal ground bracket 43 is screwed and fixed to the vehicle body serving as a ground, thereby connecting the filter element to the ground.

  However, the location of the vehicle body made of a conductor such as iron may not be exposed near the load. In this case, the ground bracket 43 cannot be screwed to the vehicle body, and therefore the ground bracket 43 cannot be connected to the ground. Therefore, in order to properly connect the ground in order to make the noise filter CF function, as shown in FIG. 5, it is appropriate to connect between the electrode (P2) of the ground bracket 43 of the noise filter CF and the ground of the in-vehicle DC power source 21. A simple ground connection wire 32 must be connected.

  By the way, the state of the connection example shown in FIG. 5 is the same as the equivalent circuit shown in FIG. That is, since the inductor component (Le: 200 nH, for example) exists in the ground connection wire 32 itself, the ground side electrode (P2) of the noise filter CF is grounded at the ground connection point 28 via the inductor component (Le). Connected to.

However, in the equivalent circuit shown in FIG. 6, the inductor component (L) and capacitor component (C) of the noise filter CF and the inductor component (Le) of the ground connection wire 32 constitute a series resonance circuit. The influence of the inductor component (Le) appears on the actual characteristics of the filter CF. That is, the resonance frequency fo in this case is expressed by the following equation.
fo = 1 / (2π√ ((L + Le) · C)) (1)

  That is, the resonance frequency is shifted by an amount corresponding to the inductor component (Le) of the ground connection wire 32 as compared with the resonance frequency of the noise filter CF alone assumed at the time of design. As shown in FIG. 4, the attenuation characteristic of this type of noise filter generally has a maximum attenuation in the vicinity of the resonance frequency (attenuation pole frequency), and tends to decrease as the distance from the resonance frequency increases or decreases. is there. Therefore, when the resonance frequency fo changes due to the influence of the inductor component (Le) of the ground connection wire 32, the attenuation pole frequency of the attenuation characteristic of the noise filter CF moves as shown in FIG. Moreover, since an inductor component (Le) of about 1 μH per 1 m of wiring length actually exists, it is also affected by the length of the ground connection electric wire 32 to be used. As a result, a sufficient amount of attenuation cannot be obtained in a part or the entire frequency band (for example, 520 kHz to 1650 kHz) assumed at the time of design.

  In order to prevent such a movement of the attenuation pole frequency, the filter connection method of the present invention is applied and the connection is made as shown in FIG. That is, as shown in FIG. 1, one end of the electric wire 24 is connected to the power line 31 of the in-vehicle DC power source 21, and the other end of the electric wire 24 is connected to the in-vehicle device high-frequency noise filter 10 </ b> A at the location (P1) of the external electrode 13. Connecting. In addition, one end of the electric wire 25 is connected to the on-vehicle equipment high frequency noise filter 10 </ b> A at the location (P 1) of the external electrode 14, and the other end of the electric wire 25 is connected to one end 22 a of the load 22. For this reason, the electric wires 24 and 25 also form electric wire lines. Furthermore, the other end 22b of the load 22 is connected to one end of the first electric wire 27 without being grounded, and the other end of the first electric wire 27 is connected to the high-frequency noise for in-vehicle equipment at the location of the external electrode 16 (P2). Connect to the filter 10A. Further, one end of the second electric wire 26 is connected to the on-vehicle equipment high frequency noise filter 10A at the position (P2) of the external electrode 15, and the other end of the second electric wire 26 is connected to an earth electrode at an appropriate earth connection point 28. (For example, a vehicle body).

  An equivalent circuit corresponding to the connection example shown in FIG. 1 is shown in FIG. In the equivalent circuit shown in FIG. 2, the use of the second electric wire 26 increases the distance from the position (P2) of the ground side terminal of the high frequency noise filter 10A for in-vehicle equipment to the ground connection point 28. However, the inductor component (Le) does not affect the attenuation pole frequency.

That is, one end (P1) of the in-vehicle device high-frequency noise filter 10A is connected to the one end 22a of the load 22 through the electric wire 25, and the other end (P2) of the in-vehicle device high-frequency noise filter 10A through the first electric wire 27. Thus, the influence of the inductor component (Le) is excluded from these circuits since it is directly connected to the other end 22b of the load 22. That is, the resonance frequency fo of the filter that affects the electromagnetic noise radiated from the load 22 is expressed by the following equation.
fo = 1 / (2π√ (L · C)) (2)

  Therefore, even if the ground side terminal (P2) of the high frequency noise filter for vehicle equipment 10A is connected to the ground at the ground connection point 28 away from this position using the second electric wire 26 as shown in FIG. The attenuation pole frequency of this filter does not move due to the influence of the inductor component (Le).

  Note that the length of the ground connection wire 32 to be used and the position of the ground connection point 28 can be appropriately changed, and even if these are changed, the attenuation pole frequency does not change. For example, it may be connected to the ground in the vicinity of one end (P2) of the on-vehicle equipment high-frequency noise filter 10A. However, if the vehicle body side conductor is not exposed in the vicinity of the load 22 such as a rear defogger to be reduced in noise, it cannot be connected to the ground by a member such as the ground bracket 43 shown in FIG. It is necessary to connect one end (P2) of the on-vehicle equipment high-frequency noise filter 10A to the ground at the ground connection point 28 at an appropriate position via the ground connection electric wire 32 having an appropriate length.

  In addition, when using the high frequency noise filter 10B for in-vehicle devices, the electric wire 24, the electric wire 25, the second electric wire 26, and the first electric wire 27 shown in FIG. 1 are respectively connected to the external electrodes 17a, 17b, 18a, and 18b. Just connect.

  In any case, by using the high frequency noise filter 10A or 10B for in-vehicle equipment shown in FIG. 3 and connecting as shown in FIG. 1, the inductor component (Le) when using the ground connection wire 32 is filtered. Can be prevented from affecting the attenuation-frequency characteristics. Therefore, even in the actual mounting state of the high-frequency noise filter 10A or 10B for in-vehicle devices, sufficient attenuation can be obtained in the entire frequency band (for example, 520 kHz to 1650 kHz) assumed at the time of design, and electromagnetic noise is generated in the in-vehicle radio receiver Etc. can be prevented from being mixed into the input.

  As described above, the high-frequency noise filter and filter connection method for on-vehicle equipment according to the present invention can be used to prevent electromagnetic noise generated on the vehicle from being mixed into the input of the on-vehicle radio receiver or the like. In particular, even when the conductor on the vehicle body side is not exposed in the vicinity of the position where the noise filter is to be connected (for example, the rear defogger), it can be easily connected to the ground without affecting the performance of the noise filter. It becomes possible.

10A, 10B In-vehicle equipment high frequency noise filter 11 Filter element 11a First electrode 11b Second electrode 12 Filter case 13, 14, 15, 16 External electrode 17 First connection terminal 17a, 17b External electrode 18 Second connection Terminals 18a, 18b External electrode 21 In-vehicle DC power supply 22 Load on in-vehicle equipment 23 Noise source 24, 25 Electric wire 26 Second electric wire 27 First electric wire 28 Ground connection point 31 Power supply line 32 Electric wire for ground connection

Claims (5)

A high-frequency noise filter for on-vehicle equipment configured by a self-resonant filter that forms a resonance circuit in which a capacitor component and an inductor component are connected in series,
One end side of the self-resonant filter can be electrically connected to a power line connecting one end of the in-vehicle DC power source and one end of the load of the in-vehicle device, and the other end side of the self-resonant filter can be grounded. And electrically connectable to the other end of the load,
A first connection terminal connected to a first electrode on one end side of the self-resonant filter and connecting a part of the power supply line to the first electrode;
A second connection terminal connected to the second electrode on the other end side of the self-resonant filter, and connecting the other end of the load and the earth to the second electrode;
With
The high frequency noise filter for on-vehicle equipment, wherein the second connection terminal is provided with two electrodes connected to the ground and the other end of the load.   At least one of the first connection terminal and the second connection terminal includes a plurality of external electrodes drawn from different locations on the outer periphery of the electrically insulating case surrounding the self-resonant filter. The high frequency noise filter for vehicle equipment according to claim 1.   The at least one of the first connection terminal and the second connection terminal includes a plurality of external electrodes drawn from the same portion of the outer periphery of the electrically insulating case surrounding the self-resonant filter. Item 2. A high-frequency noise filter for vehicle equipment according to Item 1.   2. At least one of one end side of the self-resonant filter and the other end side of the self-resonant filter is drawn from an outer periphery of an electrically insulating case surrounding the self-resonant filter. The high frequency noise filter for vehicle equipment as described in 2. A filter connection method for reducing a high-frequency noise by connecting a self-resonant filter that forms a resonance circuit in which a capacitor component and an inductor component are connected in series between an in-vehicle DC power source and a load of an in-vehicle device. ,
Connect one end of the self-resonant filter to a power line connecting one end of the in-vehicle DC power source and one end of the load,
The other end of the load is connected to the other end of the self-resonant filter via a predetermined first electric wire without being grounded, and the first electric wire and the other end of the self-resonant filter are connected to each other. An earth connection point is formed in the vicinity of the other connection point on the ground side of the in-vehicle DC power supply from the connection point via a predetermined second electric wire from the connection point. Filter connection method.

Images