JP3666967B2 - Ground connection structure - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a grounding structure between printed circuit boards having a frame ground connected to a conducting portion of a housing and a ground separated from the frame ground, for example, a signal ground.
[0002]
[Prior art]
As a source of common mode noise (noise generated between the frame ground and the output terminal) in a system in which a plurality of substrates on which digital circuits and analog circuits are formed are connected via a frame ground and a cable, respectively, for example, a digital circuit There is switching noise generated in This switching noise affects analog circuits formed on the same substrate, as well as other substrates connected via a frame ground or cable.
[0003]
As countermeasures against the influence of the switching noise as described above, generally, the ground of both the digital circuit and the analog circuit is connected to the frame ground at one point, or the signal ground and the frame ground are weakly connected. . FIG. 8 shows an example of a conventional ground-to-ground connection structure.
[0004]
As shown in FIG. 8, the conventional ground-to-ground connection structure is a structure in which a signal ground 229 and a frame ground 230 are connected to each other by a ground-to-ground connection 231 having a sufficiently small pattern width on a printed board. ing.
[0005]
[Problems to be solved by the invention]
However, in the conventional ground-to-ground connection structure described above, the switching noise of the digital circuit does not affect the analog circuit in the board, but it occurs in other devices and board circuits connected via cables and frame grounds. When such high frequency noise enters from a cable or a frame ground, there is a problem that it is not a sufficient measure and is affected by the high frequency noise.
[0006]
In some cases, high-frequency noise is generated in the board, and the propagation of high-frequency noise from the signal ground to the frame ground cannot be prevented. Other devices and boards to which the high-frequency noise is connected via the frame ground There is also a problem of affecting the circuit.
[0007]
The object of the present invention is to solve the above problems, be free from the influence of high-frequency noise from the outside, and between grounds where high-frequency noise generated in the board does not affect other equipment or the board. It is to provide a connection structure.
[0008]
[Means for Solving the Problems]
The ground-to-ground connection structure of the present invention is provided with a digital circuit and an analog circuit, and has a first grounding portion connected to the conducting portion of the housing and at least one second grounding portion separated from the first grounding portion. A connection structure between grounds in a printed circuit board, wherein the first grounding part is a frame ground common to the digital circuit and the analog circuit, and the second grounding part is provided in each of the digital circuit and the analog circuit. and it has a signal ground, wherein the first and second grounding portion, characterized in that it is connected via a printed inductor having a predetermined shape pattern formed on the printed circuit board.
[0009]
In the inter-ground connection structure, a cable connected to the outside of the printed circuit board may be attached to the digital circuit .
[0011]
Furthermore, the shape pattern of the printed inductor may be a parallel zigzag shape, a spiral shape, a spiral shape, or a combination thereof.
[0012]
Furthermore, at least a part of the printed board may be made of a magnetic material, and the printed inductor may be formed on the magnetic material.
[0013]
Further, a magnetic material may be uniformly applied on the surface on which the printed inductor is formed.
[0014]
<Action>
In the ground-to-ground connection structure of the present invention configured as described above, for example, high-frequency noise propagating from an external device to the first ground portion (frame ground) via a cable or the like is prevented from propagating by the printed inductor. Therefore, for example, the high frequency noise does not affect the analog circuit connected to the second ground portion. Further, for example, the high frequency noise generated in the digital circuit connected to the second grounding portion is prevented from propagating by the printed inductor, so that the high frequency noise propagates through the first grounding portion (frame ground) and other Does not affect the equipment.
[0015]
In the present invention in which a magnetic material is used as a part of the configuration, a printed inductor is formed on the magnetic material, or a magnetic material is applied on the printed inductor, so that a larger inductance can be obtained. As the inductance increases, the effect of preventing high-frequency noise propagation increases.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described with reference to the drawings.
[0017]
By forming a wiring made of a conductor film on a printed board in, for example, a zigzag shape, a spiral shape, or a spiral shape, a function as an inductor can be obtained. The inter-ground connection structure of the present invention is characterized in that grounds are connected by a printed inductor on a printed circuit board.
[0018]
<First embodiment>
1A and 1B are diagrams for explaining a schematic configuration of a connection structure between grounds according to a first embodiment of the present invention. FIG. 1A is a plan view and FIG. 1B is a diagram showing an equivalent circuit thereof.
[0019]
The ground-to-ground connection structure of the present embodiment is a structure in which a signal ground and a frame ground are connected on a printed circuit board by a printed inductor, and the configuration is as shown in FIG. 2 are connected by a printed inductor 3.
[0020]
The printed inductor 3 is formed by forming a plurality of parallel zigzag wirings (meander type wirings) folded at a predetermined interval on a printed circuit board. One end of the wiring is the signal ground 1 and the other end is It is connected to the frame ground 2. The printed inductor 3 configured in this way is equivalent to a coil as shown in FIG.
[0021]
FIG. 2 shows the impedance characteristics of the inter-ground connection structure configured as described above. As can be seen from FIG. 2, in this inter-ground connection structure, the impedance is low when the frequency is low, and the impedance is high when the frequency is high. Therefore, the high frequency noise has a high impedance, and the propagation of the high frequency noise is hindered.
[0022]
FIG. 3 is a diagram showing a state of high-frequency noise propagation in an apparatus using the inter-ground connection structure shown in FIG.
[0023]
In FIG. 3, an apparatus 110 has a printed circuit board on which a digital circuit 111 is formed. The printed circuit board is not provided with a ground-to-ground connection structure using a printed inductor. It is connected to the body 113.
[0024]
The device 120 includes a printed circuit board on which a digital circuit 121 and an analog circuit 122 are formed. A digital ground 122 of the digital circuit 121 is connected to a housing 126 via a printed inductor 124, and an analog ground 123 of the analog circuit 122 is It is connected to the housing 126 via the printed inductor 125. That is, a ground-to-ground connection structure using the printed inductor shown in FIG. 1 is formed.
[0025]
The device 110 and the device 120 are connected by a cable 30, and the casings (conducting portions of the casing) 113 and 126 of these devices are electrically connected.
[0026]
In the system configured as described above, the high frequency noise generated in the digital circuit 111 propagates from the housing 113 to the housing 126 via the cable 30, but the high frequency noise is prevented from propagating in the printed inductor 125. The analog circuit 122 is not affected by the high frequency noise.
[0027]
On the other hand, the high frequency noise generated in the digital circuit 121 is prevented from being propagated to the device 1 side via the cable because the printed inductor 125 prevents the high frequency noise from propagating. Therefore, the high frequency noise generated in the digital circuit 121 does not affect other devices connected via the cable or the frame ground.
[0028]
The above-described ground-to-ground connection structure of the first embodiment uses a printed inductor in which wirings made of a conductor film are formed in a parallel zigzag pattern on a printed board, but the shape of the printed inductor is limited to this. However, it may have a function as an inductor, and may be, for example, a spiral shape or a spiral shape, or a combination of a plurality of different shape patterns. An example of a ground-to-ground connection structure using printed inductors having different wiring patterns is given below.
[0029]
<Second embodiment>
FIG. 4 is a plan view of the inter-ground connection structure according to the second embodiment of the present invention.
[0030]
In FIG. 4, the printed circuit board is of a multilayer type having first and second wiring layers, and a signal ground 9 and a frame ground 10 are formed on the first wiring layer (substrate surface).
[0031]
In the first and second wiring layers, a plurality of through-hole pairs composed of two through-holes formed at equal intervals are arranged in parallel, and the first and second wirings are arranged via these through-holes. Three-dimensionally zigzag wiring (spiral wiring) is formed in the layer. One end of the spiral wiring of the printed inductor 12 is formed in the first wiring layer, connected to the frame ground 10, and the other end is formed in the second wiring layer. It is connected to a signal ground 9 formed in the first wiring layer through a hole. That is, the signal ground 9 and the frame ground 10 are connected by a printed inductor 12 having a spiral wiring pattern.
[0032]
The ground-to-ground connection structure configured as described above can also prevent high-frequency noise from propagating as in the first embodiment described above.
[0033]
<Third embodiment>
FIG. 5 is a plan view of an inter-ground connection structure according to a third embodiment of the present invention.
[0034]
In FIG. 5, the printed circuit board is a multilayer type having first and second wiring layers, and a digital ground 14, an analog ground 15, and a frame ground 17 are formed on the first wiring layer (substrate surface). Yes.
[0035]
The printed inductors 13a and 13b have a parallel zigzag wiring pattern, and their shapes are inverted. One end of the wiring of the printed inductor 13a is connected to the digital ground 14, one end of the wiring of the printed inductor 13b is connected to the analog ground 15, and these are connected at the other end of the wiring. .
[0036]
The printed inductor 18 has a spiral wiring pattern. One end (the outer end of the vortex) of the wiring of the printed inductor 18 is connected to the connection portion of the printed inductors 13a and 13b. The other end is connected to one end of the lower lead line 16 formed in the second wiring layer via the through hole 19a. The other end of the lower lead line 16 is connected to a frame ground 17 formed in the first wiring layer through a through hole 19b.
[0037]
That is, in the connection structure between the grounds of the present embodiment, the digital ground 14 and the analog ground 15 are connected via the printed inductors 13a and 13b, and the digital ground 14 and the frame ground 17 are connected via the printed inductors 13a and 18. The analog ground 15 and the frame ground 17 are connected via the printed inductors 13 b and 18.
[0038]
The ground-to-ground connection structure configured as described above can prevent the propagation of high-frequency noise as in the first and second embodiments described above.
[0039]
<Fourth embodiment>
FIG. 6A is a plan view of the inter-ground connection structure according to the fourth embodiment of the present invention, and FIG. 6B is a cross-sectional view taken along line AA ′ of FIG.
[0040]
In FIG. 6, a frame ground 24 is formed on the back surface of the printed circuit board 28, and a signal ground 20 having a square wiring pattern and a printed inductor 22 having a spiral wiring pattern are formed on the front surface. The printed inductor 22 is formed in the signal ground 20, and one end of the wiring (end outside the vortex) is connected to the signal ground 20. The printed circuit board 28 is screwed to the casing 25 on the back side of the frame ground 24 by screws 21 at the end of the printed inductor 22 on the center side of the vortex. That is, the other end of the printed inductor 22 (end on the center side of the vortex) is electrically connected to the frame ground 24 via the screw 21.
[0041]
Also in the connection structure between the grounds of the present embodiment configured as described above, high-frequency noise can be prevented from propagating as in the first to third embodiments described above.
[0042]
In the connection structure between the grounds of the embodiments described above, the slope of the impedance characteristic curve shown in FIG. 2 becomes larger as the inductance of the printed inductor increases. Therefore, it is desirable that the printed inductor has a larger inductance. Since the inductance of the printed inductor increases as the length of the wiring pattern increases, for example, in the case of a zigzag printed inductor, the wiring pattern is lengthened by increasing the number of turns of the wiring, and a larger inductance can be obtained. . However, since the area where the printed inductor can be formed is limited in terms of mounting, there is a limit to increasing the inductance by lengthening the wiring pattern.
[0043]
As the one of the means for increasing the inductance, for example, a portion of the printed circuit board or printed circuit board composed of a magnetic material, there is a method of forming a printed inductor on the magnetic body. Specifically, a magnetic material such as ferrite is used as the base material of the printed board 28 shown in FIG. 6B, or the magnetic material is previously formed on the surface on which the printed inductor is formed on the printed board 28. Or apply. Thereby, propagation of high frequency noise can be effectively prevented. Also, as shown in FIG. 7, the same effect can be obtained by uniformly applying a magnetic layer 27 made of a magnetic material such as ferrite on the surface on which the printed inductor is formed. In this case, it is desirable to apply a magnetic material only on the printed inductor.
[0044]
【The invention's effect】
Since the present invention is configured as described above, the following effects can be obtained.
[0045]
In the first and second aspects, high-frequency noise generated on the first grounding portion side (ground frame) is not propagated to the second grounding portion side. Since the high frequency noise generated on the second grounding portion side is not propagated to the second grounding portion side, the influence of the high frequency noise from the outside extends to, for example, an analog circuit connected to the second grounding portion. In addition, there is an effect that it is possible to prevent the influence of the high frequency noise generated on the second grounding portion side from reaching other devices connected via the first grounding portion.
[0046]
According to the third aspect of the present invention, there is an effect that a ground-to-ground connection structure that achieves the above-described effect can be realized.
[0047]
According to the fourth and fifth aspects of the present invention, since the inductance can be increased by the magnetic material, the effect of high frequency noise can be prevented more effectively.
[Brief description of the drawings]
1A and 1B are diagrams for explaining a schematic configuration of a ground connection structure according to a first embodiment of the present invention, in which FIG. 1A is a plan view and FIG.
FIG. 2 is a graph showing impedance characteristics of the ground connection structure shown in FIG. 1;
3 is a diagram showing a state of high-frequency noise propagation in an apparatus using the inter-ground connection structure shown in FIG.
FIG. 4 is a plan view of an inter-ground connection structure according to a second embodiment of the present invention.
FIG. 5 is a plan view of an inter-ground connection structure according to a third embodiment of the present invention.
6A is a plan view of an inter-ground connection structure according to a fourth embodiment of the present invention, and FIG. 6B is a cross-sectional view taken along line AA ′ of FIG.
7 is a cross-sectional view of a configuration in which a magnetic layer is provided in the inter-ground connection structure shown in FIG.
FIG. 8 is a plan view of a conventional inter-ground connection structure.
[Explanation of symbols]
1, 9, 20 Signal ground 2, 10, 17, 24 Frame ground 3, 12, 13a, 13b, 18, 22 Printed inductor 11, 16 Lower lead wire 14 Digital ground 15 Analog ground 19a, 19b Through hole 21 Screw 25 Housing Body 27 Magnetic layer 28 Printed circuit board

Claims (5)

A ground-to-ground connection structure in a printed circuit board provided with a digital circuit and an analog circuit, and having a first grounding part connected to a conducting part of a housing and at least one second grounding part separated from the first grounding part. The first ground portion is a frame ground common to the digital circuit and the analog circuit, and the second ground portion is a signal ground provided in each of the digital circuit and the analog circuit . The inter-ground connection structure, wherein the first and second grounding portions are connected via a printed inductor having a predetermined shape pattern formed on the printed board. In the inter-ground connection structure according to claim 1,
A ground-to-ground connection structure, wherein a cable connected to the outside of the printed circuit board is attached to the digital circuit. In the inter-ground connection structure according to claim 1,
A connection structure between grounds, wherein a shape pattern of the printed inductor is a parallel zigzag shape, a spiral shape, a spiral shape, or a combination thereof. In the inter-ground connection structure according to claim 1,
An inter-ground connection structure, wherein at least a part of the printed circuit board is made of a magnetic material, and the printed inductor is formed on the magnetic material. In the inter-ground connection structure according to claim 1,
A connection structure between grounds, wherein a magnetic material is uniformly applied on a surface on which the printed inductor is formed.

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