CN115299184B - Circuit boards and electronic equipment - Google Patents

Abstract

A signal line group including a ground line is connected to the circuit board (21). A communication circuit unit (50) for processing a signal received via a signal line group or a signal transmitted via a signal line group is mounted on a circuit board (21). The circuit board (21) has: a first ground pattern (60), which can be connected to the ground line in the signal line group; a second ground pattern (70), which is connected to the first ground pattern (60) via an inductance element (90) Electrically connected, the second ground pattern (70) is grounded via the first ground wire (30); and the third ground pattern (80), which is electrically connected to the second ground pattern (70) via the capacitive element (100), and The first ground pattern (60) is insulated, and the third ground pattern is connected to a ground terminal of the communication circuit unit (50).

Description

Circuit boards and electronic equipment

technical field

The invention relates to a circuit substrate and electronic equipment

Background technique

Electronic devices having a function of communicating with external devices are known. Such electronic equipment includes a circuit board on which a communication circuit is mounted, and a connector connected to a communication cable.

If such electronic equipment is exposed to static electricity, lightning, or electromagnetic noise generated from other electronic equipment disposed around, or other electronic equipment connected to a common power supply via a power cable, the intrusion from the connector connected to the communication cable Electromagnetic noise may intrude into an electronic device through a conductor pattern on a circuit board.

If the intruding electromagnetic noise is transmitted to the communication circuit, the performance of the electronic device may decrease. Therefore, a circuit board is used in which a ground pattern connected to the housing of the electronic device is separated from a ground pattern of the communication circuit.

For example, Patent Document 1 describes a circuit board in which a slit is arranged between a ground pattern of a housing of an electronic device to be grounded and a ground pattern of a communication circuit to separate these patterns.

Patent Document 1: Japanese Patent Laid-Open No. 2010-050298

Contents of the invention

However, in the circuit board described in Patent Document 1, electromagnetic noise in the high-frequency band entering from the shield portion of the communication cable is not released to the ground due to the impedance of the ground wiring connected to the equipment housing including the circuit board. Therefore, electromagnetic noise in the high-frequency band may be transmitted to the communication circuit, and the communication circuit may malfunction.

In addition, in the circuit board described in Patent Document 1, by not connecting the ground wiring, it is possible to reduce intrusive electromagnetic noise. However, in general, in order to maintain stable communication with other devices, a circuit board or a metal device housing is connected with a ground wire.

Since such ground wiring has residual inductance, residual resistance, etc., it has high impedance against electromagnetic noise entering from outside the circuit board. If electromagnetic noise enters from the communication cable through the ground wiring, it is transmitted to the communication circuit including the semiconductor element, and the communication circuit may malfunction.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a circuit board that is less susceptible to the influence of electromagnetic noise.

In order to achieve the above object, the circuit board according to the present invention is connected to a signal line group including a ground line, and a communication circuit part is mounted on the circuit board. The communication circuit part responds to signals received through the signal line group or via the signal line group The signal sent by the line group is processed,

The circuit board has:

a first ground pattern capable of being connected to the ground line in the signal line group;

a second ground pattern electrically connected to the first ground pattern via an inductance element, and the second ground pattern is grounded via a first ground line; and

A third ground pattern electrically connected to the second ground pattern via a capacitive element, the third ground pattern is insulated from the first ground pattern, and the third ground pattern is connected to a ground terminal of the communication circuit unit.

The effect of the invention

According to the present invention, it is possible to provide a circuit board and an electronic device in which electromagnetic noise in a high-frequency band entering from a connector to which a communication cable is connected is less likely to be transmitted to the communication circuit unit and less likely to return to the original path. And electronic equipment is not easily affected by electromagnetic noise.

Description of drawings

FIG. 1 is a perspective view of an electronic device according to Embodiment 1. As shown in FIG.

FIG. 2 is a top view of the electronic device shown in FIG. 1 .

FIG. 3 is a circuit diagram of the electronic device shown in FIG. 1 .

FIG. 4 is a diagram showing a modified example of the electronic device shown in FIG. 1 .

FIG. 5 is a circuit diagram of an electronic device according to Comparative Example 1. FIG.

FIG. 6 is a circuit diagram of an electronic device related to Comparative Example 2. FIG.

FIG. 7 is a circuit diagram of an electronic device according to Embodiment 1. FIG.

8 is a graph showing the results of electromagnetic field simulations of the electronic device shown in FIG. 1 and the electronic device according to Comparative Example 1. FIG.

FIG. 9 is a plan view of an electronic device according to Embodiment 2. FIG.

FIG. 10 is a circuit diagram of the electronic device shown in FIG. 9 .

FIG. 11 is a plan view of an electronic device according to Embodiment 3. FIG.

FIG. 12 is a circuit diagram of the electronic device shown in FIG. 11 .

Fig. 13 is a perspective view of the electronic device shown in Fig. 11 .

FIG. 14 is a plan view of an electronic device according to Embodiment 4. FIG.

FIG. 15 is a circuit diagram of the electronic device shown in FIG. 14 .

FIG. 16 is a plan view of an electronic device according to Embodiment 5. FIG.

FIG. 17 is a perspective view of an electronic device according to Embodiment 6. FIG.

FIG. 18 is a top view of the electronic device shown in FIG. 17 .

FIG. 19 is a cross-sectional view of the electronic device shown in FIG. 17 .

Detailed ways

(Embodiment 1)

Next, electronic device 1 including circuit board 21 according to Embodiment 1 will be described with reference to the drawings.

As shown in the perspective view of FIG. 1 , the electronic device 1 has: a metal frame 10 covering circuit elements, wiring, etc.; a circuit substrate 21 carrying pins, elements, integrated circuits, etc. a copper foil pattern formed by printing; and a ground wiring 30 electrically connected to the frame body 10 .

In addition, the pattern mentioned here means the circuit electrode including the conductor foil printed on the circuit board, and does not mean the shape of a foil.

The circuit board 21 is disposed on the frame body 10 . The circuit board 21 is, for example, a single-sided board in which a copper foil pattern is arranged only on one side of a dielectric board.

The ground wiring 30 is, for example, a copper wire connected to a ground rod buried in the ground and grounded. Hereinafter, a description will be given assuming that the ground wiring 30 is grounded.

In addition, the potential of ground is not limited to an absolute potential. The potential of ground broadly includes, for example, the potential of a conductor that is not connected to a ground rod, serves as a return path of a common mode current, and serves as a reference potential of a plurality of connected electronic devices.

The ground wiring 30 is an example of a first ground line in the claims.

In addition, as shown in the plan view of FIG. 2 , the electronic device 1 has a connector 40 of a communication cable connected to an external device, and a communication circuit unit 50 connected to the connector 40 .

Connector 40 is a receptacle that accommodates a plug or interface of a communication cable. The communication cable includes signal lines such as a pair of differential communication wires DS1 and DS2 and shielded wire SW, as indicated by dotted lines.

As shown by the solid line, the connector 40 has: a connector body B1; and conductor terminals T1, T2, T3 covered by the connector body B1 and electrically connected by physically contacting the terminals of the communication cable.

When the communication cable is connected to the connector 40 , the shielded wire SW of the communication cable and the differential communication wires DS1 and DS2 are electrically connected to the terminals T1 , T2 , and T3 of the connector 40 , respectively.

The shield wiring SW is an example of a ground wire in the claims. The set of differential communication wirings DS1 and DS2 and shielded wiring SW is an example of a signal line set in the claims.

In addition, the shield wiring SW may be a wiring that covers the connector 40 with a conductor, and connects a metal shield case, shield sheath, shield frame, etc. electrically connected to the conductor to the circuit board 21 .

The signal line may not be a pair of differential communication lines DS1 and DS2 , but may be a single-ended communication line of one line that uses the shielded line SW as a return path of current.

In addition, a normal noise filter may be provided on the differential communication wiring DS1, DS2 or the single-ended communication wiring. The noise filter may be arranged inside the connector 40 or may be arranged between the connector 40 and the communication circuit unit 50 on the circuit board 21 . Noise filters usually contain components that reduce noise, such as combinations of resistors, line-to-line capacitors, ground-to-ground capacitors, transformers, normal mode choke coils, common mode choke coils, etc.

Three connection portions P1 , P2 , and P3 are provided on the copper foil pattern of the circuit board 21 .

The connection portion P1 is a connection point provided on the first ground pattern 60 . The connection portion P1 is a connection portion that connects the first ground pattern 60 to the lead of the terminal T1 protruding from the connector 40 by solder.

In addition, the shielding wiring SW and the first ground pattern 60 may be directly connected without passing through the pin of the terminal T1. In addition, the above-mentioned metal shielding case, shielding sheath, shielding frame, etc. may be arranged between the shielding wiring SW and the first ground pattern 60 in order of the shielding wiring SW, the shielding case, and the first ground pattern 60. connect.

The connection parts P2 and P3 are connection points provided on the pattern of signal lines extending from the communication circuit part 50 . The connection parts P2 and P3 are connection parts for connecting the pattern of the signal line extending from the communication circuit part 50 to the pins of the terminals T2 and T3 protruding from the connector 40 with solder.

In the following description, details of the connector 40 are omitted. In addition, the electrical connection of the pins via the terminals T1, T2, and T3 may be described as wiring.

The communication circuit unit 50 mounts circuit elements including an integrated circuit (IC, Integrated Circuit) for communication, a high-frequency transistor, a common mode choke coil, a crystal oscillator, and the like. The communication circuit unit 50 is an electronic circuit that processes signals received via the differential communication lines DS1 and DS2 and the shielded line SW.

The ground wiring 30 is electrically connected to the housing 10 , and the second ground pattern 70 is electrically connected to the housing 10 . Therefore, the housing 10, the ground wiring 30, and the second ground pattern 70 are grounded.

The third ground pattern 80 is a copper foil pattern on the circuit board 21 that supplies a reference potential to the communication circuit unit 50 . The third ground pattern 80 is electrically connected to the ground terminal of the communication circuit unit 50 .

The first ground pattern 60 , the second ground pattern 70 and the third ground pattern 80 are formed on the surface of the circuit board 21 .

In the drawings, the first ground pattern 60 , the second ground pattern 70 , and the third ground pattern 80 are hatched in different patterns for easy understanding.

The electronic device 1 also has an inductance element 90 and a capacitance element 100 .

As shown in FIGS. 1 and 2 , the first ground pattern 60 and the second ground pattern 70 are connected via an inductance element 90 . In addition, the second ground pattern 70 and the third ground pattern 80 are connected by a capacitive element 100 .

On the other hand, the first ground pattern 60 and the third ground pattern 80 are not connected by any of conductors, capacitive elements, and inductive elements, nor are they connected by connecting members.

Hereinafter, it is expressed as insulation not being connected through any one of a conductor, a capacitive element, and an inductive element.

Termination including bob smith termination may be performed between the differential communication wiring DS1 and the first ground pattern 60 and between the differential communication wiring DS2 and the first ground pattern 60 . In addition, termination including Bob Smith termination may be performed between the differential communication wiring DS1 and the third ground pattern 80 and between the differential communication wiring DS2 and the third ground pattern 80 . In this way, when performing communication using differential signals, it is preferable to terminate the ends of the differential communication lines DS1 and DS2 to the same ground pattern, for example, to the first ground pattern 60 or the third ground pattern 80 .

In addition, in Bob Smith termination, noise mixed in the common mode tends to flow through the differential communication lines DS1 and DS2 . In addition, since noise easily flows through the communication circuit unit 50 via the third ground pattern 80 , it is preferable to connect the differential communication lines DS1 and DS2 to the third ground pattern 80 rather than connecting the differential communication lines DS1 and DS2 to the third ground pattern 80 . on the first ground pattern 60 .

Next, the inductance value L of the inductance element 90 and the capacitance value C of the capacitance element 100 will be described with reference to FIG. 3 which is a circuit diagram of the electronic device 1 .

In addition, in FIG. 3 , the noise source is represented by NS, and the electromagnetic noise generated by the noise source NS acts on the shielded wiring SW of the communication cable.

Specifically, the inductance value L of the inductance element 90 is an inductance value L that becomes high impedance with respect to electromagnetic noise HN of 1 MHz or more in a high-frequency band assumed to enter from the connector 40 .

The inductance element 90 may be an element having both a resistance component and an inductance component, and whose characteristics change according to frequency, for example, a ferrite bead. Next, a case where a ferrite bead is used as the inductance element 90 will be described.

Switching circuits, lightning, and the like generate electromagnetic noise that has a large amplitude in low-frequency components and a small amplitude in high-frequency components.

Electromagnetic noise in such a low-frequency band is less likely to be affected by the residual inductance component of the ground wiring 30 and tends to return to the noise source NS. Residual inductance is sometimes called parasitic inductance, stray inductance, self-inductance, etc., but it is called residual inductance in this embodiment.

On the other hand, electromagnetic noise in the high-frequency band generated by electrostatic discharge, brush motors, etc. is easily affected by the residual inductance component. In addition, the impedance of the capacitive element 100 is small with respect to electromagnetic noise in the high-frequency band. Therefore, electromagnetic noise in a high-frequency band invades the circuit board 21 .

If a ferrite bead is used as the inductance element 90 , the impedance is high only for a specific high-frequency band, so electromagnetic noise HN in the high-frequency band is less likely to intrude into the circuit board 21 . In particular, if a ferrite bead having a property of making it difficult to pass electromagnetic noise having a frequency close to the frequency of a signal used for communication is used, it is possible to more effectively prevent malfunction of the communication circuit unit 50 .

In addition, the residual inductance of the inductance element 90, the capacitance element 100, and the ground wiring 30 is a type of T-shaped filter circuit of the LCL. This T-shaped filter circuit has a property of performing series resonance at a resonance frequency defined by the circuit constant of the inductance element 90 and the circuit constant of the capacitive element 100 .

Electromagnetic noise having a frequency component close to the resonance frequency is transmitted from the noise source NS to the communication circuit unit 50 via the inductance element 90 and the capacitance element 100 .

Therefore, if the resonance frequency is close to the frequency of the signal used for communication, the transmitted electromagnetic noise may have a greater influence on the operation of the communication circuit unit 50 .

Therefore, it is preferable that the capacitance value C of the capacitive element 100 and the inductance value L of the inductance element 90 be set to values such that the resonant frequency of the T-shaped filter circuit is different from the frequency of a signal used for communication.

In addition, when the frequency band of the signal used for communication in the communication circuit unit 50 is wide, it is preferable to use a ferrite bead having a large resistance component as the inductance element 90 and to use a resistance element arranged in series with the inductance element 90 . Accordingly, the resonance amplitude of the T-shaped filter circuit of the LCL can be reduced, and the amount of electromagnetic noise transmitted to the communication circuit unit 50 can be reduced.

More preferably, the capacitance value C of the capacitive element 100 and the inductance value L of the inductance element 90 are set so that the resonance frequency is not only different from the fundamental frequency of the frequency of the signal used for communication, but also different from the frequency of the nth harmonic. value.

The case where the ferrite bead is used as the inductance element 90 has been described above.

In the electronic device 1 shown in FIGS. 1 to 3 , the inductance element 90 is disposed on the circuit substrate 21 . However, the inductance element 90 may also be arranged inside the connector 40 .

Specifically, the capacitance value C of the capacitive element 100 is a capacitance value C that becomes high impedance with respect to electromagnetic noise LN of a low frequency band, for example, several hundred kHz or less, which is assumed to intrude from the connector 40 .

The capacitive element 100 disposed between the second ground pattern 70 and the third ground pattern 80 may be two or more capacitors.

For example, the specifications of the inductance element 90 and the capacitance element 100 and the arrangement on the circuit board 21 are obtained by simulation using a computer.

While referring to FIGS. 5 and 6 showing circuit diagrams of electronic devices 2 and 3 according to Comparative Examples 1 and 2 having structures different from those of electronic device 1, and FIG. 7 showing another circuit diagram of electronic device 1 according to Embodiment 1, The behavior when the electronic device 1 having the above configuration is exposed to electromagnetic noise will be described.

(comparative example 1)

Unlike the electronic device 1 , the electronic device 2 including the circuit board 22 according to Comparative Example 1 does not have the first ground pattern 60 and the inductance element 90 . In the electronic device 2 , the shield wire SW of the connector 40 is directly connected to the second ground pattern 70 .

In FIG. 5 , the transmission path of the noise when the electromagnetic noise HN and the electromagnetic noise LN in the low-frequency band invades the electronic device 2 is indicated by thick arrows.

With respect to the electromagnetic noise LN in the low frequency band entering from the connector 40 , the capacitive element 100 has a high impedance, and the ground wiring 30 has a low impedance.

Therefore, the electromagnetic noise LN in the low frequency band is released from the second ground pattern 70 to the ground through the ground wiring 30 .

Therefore, the electromagnetic noise LN of the low frequency band is not transmitted to the communication circuit section 50 .

On the other hand, the capacitive element 100 has low impedance with respect to electromagnetic noise HN in the high frequency band entering from the connector 40 , but the ground wiring 30 has high impedance due to the residual inductance component.

Therefore, the electromagnetic noise HN in the high frequency band cannot be discharged to the ground through the ground wiring 30 , and is transmitted from the second ground pattern 70 to the third ground pattern 80 via the capacitive element 100 , and enters the communication circuit unit 50 .

(comparative example 2)

In electronic device 3 including circuit board 23 according to Comparative Example 2, unlike electronic device 1 , first ground pattern 60 is not electrically separated from third ground pattern 80 . The first ground pattern 60 and the third ground pattern 80 are connected by a connection member 130 .

In FIG. 6 , the transmission path of the noise when the electromagnetic noise HN and the electromagnetic noise LN in the low-frequency band invades the electronic device 3 is indicated by thick arrows.

Since it has a capacitive component, the connection member 130 is represented by a capacitive element 130 connected between the first ground pattern 60 and the third ground pattern 80 in FIG. 6 .

With respect to the electromagnetic noise LN in the low frequency band entering from the connector 40 , the inductance element 90 has low impedance, and the capacitive element 100 and the connection member 130 have high impedance.

Therefore, the electromagnetic noise LN in the low frequency band is discharged to the ground through the first ground pattern 60 , the inductance element 90 , the second ground pattern 70 , and the ground wiring 30 .

On the other hand, the inductance element 90 has a high impedance and the connection member 130 has a low impedance with respect to the electromagnetic noise HN in the high-frequency band entering from the connector 40 .

Therefore, electromagnetic noise HN in the high frequency band cannot be discharged to the ground through the inductance element 90 , but is transmitted from the first ground pattern 60 to the third ground pattern 80 through the connection member 130 , and enters the communication circuit unit 50 .

As described above, in the electronic devices 2 and 3 according to Comparative Examples 1 and 2, the performance of the communication circuit unit 50 may be degraded because electromagnetic noise HN in the high frequency band invades the communication circuit unit 50 .

On the other hand, as indicated by thick arrows in FIG. 7 , in the electronic device 1 according to Embodiment 1, not only the electromagnetic noise LN in the low frequency band but also the electromagnetic noise HN in the high frequency band is not transmitted to the communication circuit unit 50 .

Next, the transmission path of the noise when the electromagnetic noise HN of the high frequency band and the electromagnetic noise LN of the low frequency band enter the electronic device 1 will be described.

The inductance element 90 has low impedance with respect to the electromagnetic noise LN in the low frequency band entering from the connector 40 .

Therefore, similarly to Comparative Example 2, the electromagnetic noise LN in the low frequency band is discharged to the ground through the first ground pattern 60 , the inductance element 90 , the second ground pattern 70 , and the ground wiring 30 .

In addition, the inductance element 90 becomes high impedance with respect to electromagnetic noise HN in the high-frequency band entering from the connector 40 .

Therefore, unlike Comparative Example 1, the electromagnetic noise HN in the high frequency band cannot be discharged to the ground through the inductance element 90 . In addition, unlike Comparative Example 2, since the first ground pattern 60 and the third ground pattern 80 are not connected, the electromagnetic noise HN in the high frequency band is not transmitted to the third ground pattern 80 .

Therefore, the electromagnetic noise HN in the high frequency band is reflected by the inductance element 90 and is not transmitted to the communication circuit unit 50 .

The high-frequency electromagnetic noise HN reflected by the inductance element 90 is attenuated by the loss of the shield wiring SW if the shield wiring SW is sufficiently long.

In addition, when the ground wiring 30 is long, the ground wiring 30 has a high residual inductance against electromagnetic noise HN in the high-frequency band. However, in this case, according to the electronic device 1 , since the electromagnetic noise HN in the high-frequency band is not transmitted to the ground wiring 30 , it does not enter the communication circuit unit 50 .

FIG. 8 shows the results of electromagnetic field simulation comparing the circuit board 21 of the electronic device 1 and the circuit board 22 of the electronic device 2 . This simulation shows that when electromagnetic noise HN in the high-frequency band is applied between the first ground pattern 60 and the ground potential, the amount of noise transmitted to the differential communication wiring of the communication circuit unit 50 is output as an S parameter. the result of.

The circuit board 21 shown by the solid line suppresses the amount of noise more effectively in almost all frequency ranges than the circuit board 22 shown by the dotted line. In particular, in the vicinity of 100 MHz, the circuit board 21 suppresses noise by about 10 dB compared with the circuit board 22 .

In the electronic device 1 described above, the housing 10 and the second ground pattern 70 are connected by the ground wiring 30 , but the method of connecting the housing 10 and the second ground pattern 70 is not limited to this.

For example, in the circuit board 29 shown in perspective view in FIG. 4 , the second ground pattern 70 is electrically connected to the metal protrusion 11 formed by protruding a part of the housing 10 .

For example, the second ground pattern 70 and the housing 10 may be connected by the following method.

Screw holes are formed on the second ground pattern 70 of the circuit board 29 . Just below the screw hole, a convex portion 11 is formed on the frame body 10 , and a screw hole is formed at an upper end portion of the convex portion 11 . Metal is exposed on the back surface of the circuit board 29 by performing solder leveling on the second ground pattern 70 . The exposed metal portion is brought into contact with the convex portion 11 . Screws are inserted from above the second ground pattern 70 to fit into the screw holes of the protrusions 11 to fix them with screws.

In this way, since the second ground pattern 70 is pressed and fixed to the protrusion 11 , the contact resistance between the second ground pattern 70 , the housing 10 and the ground wiring 30 is reduced.

Furthermore, the ground wiring 30 may be wiring using a metal plate, a bus bar, or a combination thereof. That is, as long as it is a conductor that electrically connects the second ground pattern 70 and the housing 10 and is equal to the ground potential with respect to direct current without the influence of residual inductance, it is not limited to the harness shape shown in the figure.

Also, for DC, similarly, since the ground wiring 30 has a residual resistance component, a potential difference is generated between the ground potential and the second ground pattern 70 or the housing 10 according to the current flowing through the ground wiring 30 . Since the residual resistance component of the ground wiring 30 is sufficiently small, it is considered below that the potential of the ground wiring 30 and conductors electrically connected via the ground wiring 30 is equal to the ground potential.

(Embodiment 2)

The electronic device 4 including the circuit board 24 according to the second embodiment has the same structure as the electronic device 1 according to the first embodiment, and the distances between the first ground pattern 60 , the second ground pattern 70 and the third ground pattern 80 have the relationship described later.

9, the shortest distance DA between the first ground pattern 60 and the third ground pattern 80 of the circuit board 24 is greater than the shortest distance DB between the second ground pattern 70 and the third ground pattern 80. .

Even if a parasitic capacitance component occurs between the first ground pattern 60 and the third ground pattern 80 , its capacitance value is relatively small compared to the capacitance element 100 .

In the circuit diagram shown in FIG. 10 , the capacitance value of capacitive element 100 is C, and the capacitance value of parasitic capacitance component 140 generated between first ground pattern 60 and third ground pattern 80 is C0.

In addition, let the opposing cross-sectional area of the first ground pattern 60 and the third ground pattern 80 be S1 [m ² ], and let the opposing cross-sectional area of the second ground pattern 70 and the third ground pattern 80 be S2 [m ^{2 ]} . ].

As described above, the distance DA is larger than the distance DB.

Therefore, as shown in the following mathematical formula, regarding the capacitance C1 [F] between the first ground pattern 60 and the third ground pattern 80 and the capacitance C2 [F] between the second ground pattern 70 and the third ground pattern 80 , C2>>C1 can be satisfied.

[mathematical formula 1]

ε ₀ [F/m] is the dielectric constant of vacuum

ε _r [F/m] is the relative permittivity of the circuit substrate 21

The capacitance C0 of the parasitic capacitance component 140 is usually C0>C1. However, if DA is made sufficiently larger than DB, the value of C0 can be made sufficiently small.

Accordingly, the capacitance value C0 of the parasitic capacitance component 140 is negligibly small for the electromagnetic noise HN in the high-frequency band.

Therefore, as shown by the thick arrow, electromagnetic noise HN in the high-frequency band entering from the connector 40 is not transmitted to the third ground pattern 80 through the parasitic capacitance component 140 . In addition, since the inductance element 90 has high impedance to the electromagnetic noise HN in the high frequency band, the electromagnetic noise HN in the high frequency band is not transmitted to the communication circuit unit 50 through the inductance element 90 .

As described above, according to the electronic device 4 , compared with the electronic device 1 , it is possible to more effectively prevent the intrusion of the electromagnetic noise HN in the high-frequency band.

(Embodiment 3)

In the electronic devices 1 and 2, only the second ground pattern 70 is grounded, but the first ground pattern 60 and the second ground pattern 70 may be grounded together.

As shown in FIG. 11 , an electronic device 5 including a circuit board 25 according to Embodiment 3 has the same structure as that of electronic device 1 according to Embodiment 1, and has a connection to a first ground pattern 60 except for a ground wiring 30 . The grounding wiring 31.

The ground wiring 30 is electrically connected to the second ground pattern 70 through the ground wiring connection portion 71 , and the ground wiring 31 is electrically connected to the first ground pattern 60 through the ground wiring connection portion 61 .

The ground wiring connection parts 61 and 71 are connection parts of conductors provided on the copper foil pattern, and are, for example, metal rings.

In FIG. 12 , the noise transmission path when the electromagnetic noise HN and the electromagnetic noise LN in the low-frequency band invades the electronic device 5 is indicated by thick arrows.

The inductance element 90 has a low impedance and the capacitive element 100 has a high impedance with respect to the electromagnetic noise LN in the low frequency band entering from the connector 40 .

Therefore, the electromagnetic noise LN in the low frequency band is discharged to the ground through the first ground pattern 60 , the inductance element 90 , the second ground pattern 70 , and the ground wiring 30 .

On the other hand, electromagnetic noise HN in the high-frequency band entering the first ground pattern 60 from the connector 40 cannot pass through the inductance element 90 .

In addition, the ground wiring 31 has a residual inductance component similarly to the ground wiring 30 . Nevertheless, if the ground wiring 31 is short, the impedance value of the residual inductance component with respect to the electromagnetic noise HN in the high-frequency band is relatively small.

Therefore, electromagnetic noise HN in the high-frequency band entering from the connector 40 is discharged to the ground through the ground wiring 31 without returning to the shield wiring SW.

As described above, according to the electronic device 5, not only the electromagnetic noise HN in the high frequency band is not transmitted to the communication circuit unit 50, but also the reflected wave of the electromagnetic noise HN in the high frequency band can be transmitted to other devices connected via the communication cable. inhibition.

Therefore, it is possible to prevent malfunctions of other devices connected to the electronic device 5 via the communication cable.

In addition, the ground wiring 31 is not limited to a harness shape, and may be a plate shape such as a metal plate or a bus bar.

The ground wiring 31 is an example of the second ground line in the claims.

The electronic device 5 has two wirings, a ground wiring 30 and a ground wiring 31 . However, the wiring for grounding the first ground pattern 60 and the second ground pattern 70 may be a single ground wiring 30, and the first ground pattern 60 and the second ground pattern 70 may be electrically connected to the housing 10. .

Specifically, as shown in FIG. 13 , metal protrusions 11 and 12 may be arranged on the frame body 10, the first ground pattern 60 and the protrusion 12 may be connected by screws 110, and the second ground pattern 70 may be connected by screws 110. It is connected with the convex part 11.

As a result, the first ground pattern 60 and the second ground pattern 70 are grounded through the housing 10 .

(Embodiment 4)

The ground wiring 31 of the electronic device 5 is a wiring that directly grounds the first ground pattern 60 , but the structure for grounding the first ground pattern 60 is not limited thereto.

As shown in FIG. 14 , electronic device 6 according to Embodiment 4 has ground wiring 32 different from ground wiring 30 on circuit board 26 . In addition, the electronic device 6 has a fourth ground pattern 150 electrically connected to the ground wiring 32 and different from the first ground pattern 60 , the second ground pattern 70 , and the third ground pattern 80 .

Between the first ground pattern 60 and the fourth ground pattern 150 is arranged a varistor element 160 which is an element whose resistance value decreases when the applied voltage increases.

The electronic device 6 has an effect of efficiently releasing the electromagnetic noise HHN in the high-voltage high-frequency band to the ground.

Referring to FIG. 15 , the effects of the electronic device 6 will be described.

When high voltage and high frequency electromagnetic noise HHN enters from the connector 40, a high voltage is applied to the varistor element 160 connected to the first ground pattern 60, and the varistor element 160 becomes low impedance. Therefore, the high-voltage and high-frequency electromagnetic noise HHN entering from the connector 40 is released from the ground wiring 32 to the ground through the varistor element 160 and the fourth ground pattern 150 .

Therefore, according to electronic device 6 , even if high-voltage and high-frequency electromagnetic noise HHN enters from connector 40 , insulation breakdown of inductance element 90 , capacitance element 100 , communication circuit unit 50 , and the like can be prevented.

In addition, the ground wiring 32 is an example of the 2nd ground line in a claim.

(Embodiment 5)

The inductance element 90 connected between the first ground pattern 60 and the second ground pattern 70 does not need to be a coil as a separate component.

As shown in FIG. 16 , electronic device 7 including circuit board 27 according to Embodiment 5 has copper foil pattern 91 instead of inductance element 90 .

The copper foil pattern 91 is printed in an elongated rectangular shape between the first ground pattern 60 and the second ground pattern 70 .

This copper foil pattern 91 is a conductor having an inductance component with respect to electromagnetic noise HN in a high-frequency band. The specific position, width, length, thickness, etc. of such copper foil pattern 91 are based on the structure of the circuit board 27, the material and thickness of the dielectric contained in the circuit board 27, for example, by a method such as a common strip line or a microstrip line. Wait for the design.

According to the electronic device 7 , when the first ground pattern 60 and the second ground pattern 70 are printed, the inductance element 90 in the electronic device 1 can be formed with the copper foil pattern 91 . In this way, since the coil as a separate component is unnecessary, the number of components of the electronic device 7 can be reduced compared to the electronic device 1 .

Therefore, according to the electronic device 7 , the design freedom of the circuit board 27 is improved, and the space saving and weight reduction of the electronic device 7 are realized.

In addition, the shape of the copper foil pattern 91 is not limited to an elongated rectangle. The copper foil pattern 91 may be, for example, a coil formed using layers of the circuit board 27 . Thereby, the inductance value of the copper foil pattern 91 can be made large.

(Embodiment 6)

The electronic device 8 according to the sixth embodiment is different from the electronic device 1 in which the circuit board 21 is constituted by a single-sided substrate. Features a copper foil pattern.

As shown in FIG. 17, a multilayer substrate 170 has two dielectric layers 171, 172 as dielectric layers, an inner layer 173 that is a layer sandwiched between the two dielectric layers 171, 172, and a surface layer 174 disposed on the outermost side. The communication circuit unit 50 , the first ground pattern 60 , the second ground pattern 70 , the third ground pattern 80 , and the like are mounted on the surface layer 174 .

The dielectric layer 171 is an example of the first dielectric layer in the claims, the dielectric layer 172 is an example of the second dielectric layer in the claims, and the surface layer 174 is an example of the outermost layer in the claims.

As shown in FIG. 18 , the first ground pattern 60 , the second ground pattern 70 , and the third ground pattern 80 are arranged on the outermost layer of the multilayer substrate 170 .

In addition, as indicated by the dotted line, a fifth ground pattern 81 which is a copper foil pattern is arranged at a position facing the communication circuit unit 50 .

As shown in FIG. 19 , which is a cross-sectional view of electronic device 8 taken along line A-A, fifth ground pattern 81 is arranged on inner layer 173 and sandwiched between dielectric layers 171 and 172 .

The third ground pattern 80 arranged on the surface layer 174 is electrically connected to the fifth ground pattern 81 arranged on the inner layer 173 through the via hole 180 .

The via hole 180 is an example of a connection conductor in the claims.

So far, the case where the electromagnetic noise HN in the high frequency band enters from the connector 40 has been studied. However, electromagnetic noise HN in the high frequency band is not limited to intrusion from the connector 40 .

For example, due to electromagnetic spatial coupling, electromagnetic noise HN in the high-frequency band may intrude from a path other than the connector 40 .

When the potential of one of the front and rear surfaces of dielectric layer 171 changes due to electromagnetic noise HN in the high-frequency band, the potential of the other surface also changes. Also, potentials varying in the same phase cancel each other due to common-mode coupling. Therefore, no voltage fluctuation occurs between the communication circuit unit 50 , the third ground pattern 80 , and the fifth ground pattern 81 .

The reason for this will be described below.

First, when the electromagnetic noise HN in the high frequency band enters the communication circuit unit 50 and the voltage of the communication circuit unit 50 varies by ΔV, the voltage of the fifth ground pattern 81 disposed opposite to the communication circuit unit 50 also varies by ΔV. Furthermore, since the third ground pattern 80 and the fifth ground pattern 81 are electrically connected through the via hole 180 , the voltage of the third ground pattern 80 also fluctuates by ΔV.

Therefore, the voltage of the communication circuit unit 50 and the voltage of the third ground pattern 80 are kept at the same voltage.

In addition, if the electromagnetic noise HN in the high-frequency band enters the third ground pattern 80 and the voltage of the third ground pattern 80 varies by ΔV, the voltage of the fifth ground pattern 81 electrically connected to the third ground pattern 80 through the via hole 180 The voltage also varies by ΔV. Furthermore, the voltage of the communication circuit unit 50 arranged to face the fifth ground pattern 81 also fluctuates by ΔV.

Therefore, the voltage of the communication circuit unit 50 and the voltage of the third ground pattern 80 are kept at the same voltage.

In addition, even when electromagnetic noise HN in the high-frequency band invades both the communication circuit unit 50 and the third ground pattern 80, the voltage of the communication circuit unit 50 and the voltage of the third ground pattern 80 are kept the same. Voltage.

In this way, even when electromagnetic noise HN in the high-frequency band enters from a route other than the connector 40 , there will be a gap between the voltage of the communication circuit unit 50 and the voltage of the third ground pattern 80 serving as the reference potential of the communication circuit unit 50 . also does not make a difference.

Therefore, according to the electronic device 8, even in such a case, malfunction of the communication circuit unit 50 is less likely to occur.

The present invention can be made into various embodiments and modifications without departing from the broad spirit and scope of the present invention. In addition, the above-mentioned embodiments are for describing the present invention, and do not limit the scope of the present invention. That is, the scope of the present invention is shown not by the embodiment but by the claims. Furthermore, various modifications implemented within the scope of the claims and within the scope of the disclosure equivalent thereto are deemed to fall within the scope of the present invention.

Explanation of labels

1, 2, 3, 4, 5, 6, 7, 8 electronic equipment, 10 frame body, 11, 12 convex part, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29 circuit board, 30, 31, 32 ground wiring, 40 connector, 50 communication circuit part, 60 first ground pattern, 61 ground wiring connection part, 70 second ground pattern, 71 ground wiring connection part, 80 third ground pattern, 81 Fifth ground pattern, 90 Inductance element, 91 Copper foil pattern, 100 Capacitance element, 110 Screw, 130 Connection part, 140 Parasitic capacitance component, 150 Fourth ground pattern, 151 Ground wiring connection part, 160 Varistor element, 170 Multi-layer substrate, 171, 172 dielectric layer, 173 inner layer, 174 surface layer, 180 via hole, B1 connector body, C, C0 capacitance value, distance between DA 1st ground pattern and 3rd ground pattern, DB 2nd ground pattern Distance from the third ground pattern, DS1, DS2 differential communication wiring, NS noise source, electromagnetic noise in HN high-frequency band, L inductance value, electromagnetic noise in LN low-frequency band, electromagnetic noise in HHN high-voltage high-frequency band, P1 , P2, P3 connectors, SW shielded wiring, T1, T2, T3 terminals.

Claims (8)

1. A circuit board connected to a signal line group including a ground line, a communication circuit unit mounted on the circuit board, the communication circuit unit processing a signal received via the signal line group or a signal transmitted via the signal line group,

the circuit board comprises:

a 1 st ground pattern connectable to the ground line in the signal line group;

a 2 nd ground pattern electrically connected to the 1 st ground pattern via an inductance element, the 2 nd ground pattern being grounded via a 1 st ground line; and

and a 3 rd ground pattern electrically connected to the 2 nd ground pattern via a capacitor element, the 3 rd ground pattern being insulated from the 1 st ground pattern, the 3 rd ground pattern being connected to a ground terminal of the communication circuit section.

2. The circuit substrate of claim 1, wherein,

the shortest distance between the 1 st ground pattern and the 3 rd ground pattern is greater than the shortest distance between the 2 nd ground pattern and the 3 rd ground pattern.

3. The circuit substrate according to claim 1 or 2, wherein,

the 2 nd grounding wire is electrically connected with the 1 st grounding pattern,

the 1 st ground line is different from the 2 nd ground line.

4. The circuit substrate according to claim 3, wherein,

the circuit substrate has a 4 th grounding pattern, the 4 th grounding pattern is electrically connected with the 1 st grounding pattern through a variable resistance element,

the 2 nd ground line is electrically connected with the 4 th ground pattern.

5. The circuit substrate according to claim 1 or 2, wherein,

the inductance element is a copper foil pattern.

6. The circuit substrate according to claim 1 or 2, wherein,

the circuit board includes: a 1 st dielectric layer comprising a 1 st dielectric; a 2 nd dielectric layer comprising a 2 nd dielectric; an inner layer disposed between the 1 st dielectric layer and the 2 nd dielectric layer, the inner layer including a 5 th ground pattern; and an outermost layer which is a layer in contact with the 1 st dielectric layer and is located on a different side from the inner layer,

the 1 st grounding pattern, the 2 nd grounding pattern and the 3 rd grounding pattern are arranged on the surface layer,

the 3 rd ground pattern and the 5 th ground pattern are electrically connected by a connection conductor penetrating the 1 st dielectric layer,

the communication circuit unit is disposed on the outermost layer so as to face the 5 th ground pattern.

7. The circuit substrate according to claim 1 or 2, wherein,

the resonant frequency of the T-shaped filter circuit comprising the inductance element, the capacitance element and the 1 st grounding wire is different from the frequency of the received signal or the frequency of the transmitted signal.

8. An electronic device comprising the circuit substrate of any one of claims 1 to 7, the electronic device having:

a connector connected to the signal line group; and

and a wiring for connecting the signal line group to the communication circuit section via the connector and connecting the ground line to the 1 st ground pattern.

Images