JP3426430B2 - Electrical equipment with reduced high-frequency noise - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric device for reducing high frequency noise around an external interface connector mounted on a printed circuit board.

[0002]

2. Description of the Related Art The potential levels of a power supply pattern, a signal pattern and a ground pattern formed on a printed circuit board vary due to noise caused by crosstalk between patterns and reflection / resonance. If the potential level of the ground pattern fluctuates, the reference level of each component mounted on the printed circuit board fluctuates, which is likely to cause malfunction.

FIG. 4 is a diagram simply showing the mechanism by which the potential level of the ground pattern fluctuates. As shown in the drawing, when the ground terminals of the components A and B are connected to the ground pattern with a distance L, the ground pattern has an impedance (hereinafter,
Common impedance) ZG. Therefore, the part A
When the current IA flows from the ground terminal of to the ground pattern, the potential of the ground pattern changes by IAZG,
The voltage level of the ground terminal of the component B also changes by this potential.

Thus, simply connecting the ground terminals of a plurality of components to the ground pattern is likely to be affected by noise due to the common impedance of the ground pattern. Therefore, a method has been proposed in which the common impedance of the ground pattern is eliminated by taking a one-point ground to reduce noise.

FIG. 5 is a diagram for explaining the outline of the one-point ground, and shows an example of the one-point ground in which the ground terminal of each component on the printed circuit board and the ground terminal of the power source are directly connected to dedicated ground patterns. ing. 1 as shown in FIG.
If the point ground is taken, the ground pattern has no common impedance, and the potential of each ground pattern does not fluctuate under the influence of other ground patterns. However, in order to establish a one-point ground, it is necessary to lay a ground pattern for each component, and in many cases, it is not possible to obtain a one-point ground if the packaging density of the components is high. Therefore, in general, the ground pattern is often made thicker than other patterns, or a solid ground pattern is often provided on the inner layer surface of the printed board.

[0006]

On the other hand, there are low frequency low frequency noise and high frequency high frequency noise as noise, and it is known that low frequency noise can be efficiently reduced by the solid pattern described above. However,
High-frequency noise cannot often be reduced even by a solid pattern, and performance deterioration and malfunction due to high-frequency noise have been regarded as problems. In particular, many electric devices are often arranged in close contact with each other inside a vehicle, and if high-frequency noise is generated from each electric device, the operation of other electric devices may be adversely affected. As far as possible, it is desirable to reduce high frequency noise.

It is an object of the present invention to provide an electric device which can efficiently reduce the high frequency noise flowing to the ground of the printed board.

[0008]

The present invention will be described with reference to FIG. 1 showing an embodiment of the present invention. In the present invention, a high frequency wave having a printed circuit board 1 to which a connector 2 for an external interface is attached. It is applied to electrical equipment with reduced noise and has through holes 4 formed on both sides sandwiching the connector 2 in a direction substantially orthogonal to the mounting / removing direction of the connector 2 in the printed circuit board 1, and the peripheral portion of the connector 2 and the metal fitting 5. A ground plane 1a is formed on the metal plate 6 and the metal case 6 of the electric device is fixed to the printed circuit board 1 by inserting the metal fitting 5 into the through hole 4 so that the current including the high frequency noise component flowing through the ground plane 1a is directed toward the metal fitting 5. The above object is achieved by forming the slits 7 having a predetermined width and a predetermined length along the direction in which the metal fittings 5 are arranged in the ground plane 1a so as to flow. In the invention described in claim 1, the connector 2
The ground plane 1a is formed around the metal fitting 5, and the slits 7 are formed in the ground plane 1a along the direction in which the metal fittings 5 are arranged.
a is at least partially separated into two regions. As a result, the current containing the high-frequency noise component flowing in the ground plane 1a is prevented from flowing in the direction of the connector 2 beyond the slit 7, and flows in the direction of the metal fitting 5 along the slit 7. A second aspect of the present invention is the electric device with reduced high frequency noise according to the first aspect, wherein the connector 2 is attached to an end portion of the printed circuit board 1, and the connector 2 is attached.
The slit 7 is formed so as to surround the connector 2 except for the surface facing the end portion of the. In the invention described in claim 2, the connector 2 is attached to the end portion of the printed board 1 as shown in FIGS. 1 and 2, and the slit 7 is formed so as to surround the connector 2. As a result, the current containing the high-frequency noise component flowing in the direction of the slit 7 can be reliably cut off by the slit 7, and the ground plane 1a surrounding the connector 2 surrounded by the slit 7 is not affected by the high-frequency noise. A third aspect of the present invention is the electric device with reduced high frequency noise according to the first or second aspect, wherein the ground plane 1a is formed on the inner layer surface of the printed board 1. According to the third aspect of the invention, the ground plane 1a is formed on the inner layer surface of the printed circuit board 1, and the ground plane is not formed on the component mounting surface or the solder surface of the printed circuit board 1 on which the signal pattern and the power supply pattern are formed. To do.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows high frequency noise according to the present invention.
It is a figure explaining the electric equipment which reduced . In FIG. 1, reference numeral 1 is a printed circuit board on which an external interface connector 2 and an EMI filter 3 for reducing radiation noise are mounted. In addition, various electronic components are mounted on the printed circuit board 1, but they are omitted in FIG. A solid ground plane 1a is formed on the inner layer surface of the printed circuit board 1 as shown in the figure. In FIG. 1, the component mounting surface 1b of the printed circuit board 1 and the ground plane 1a of the inner layer surface are drawn separately for the sake of clarity, but in reality they are bonded.

The connector 2 is attached to an end portion of the printed board 1, and through holes 4 for screwing are formed on both sides of the printed board 1 with the connector 2 interposed therebetween. A fitting 5 can be inserted into the through hole 4 as shown in the drawing, and the printed board 1 is screwed to the metal case 6 by the fitting 5.
Specifically, the opening 6a formed in the metal case 6 and the connector 2 of the printed circuit board 1 are aligned with each other, and the printed circuit board 1 is pressed by a claw (not shown) formed in the metal case 6, and the through hole is formed. The metal fitting 5 is inserted through the screw 4 and the printed circuit board 1 and the metal case 6 are screwed. Thereby, even if the lid of the metal case 6 is closed, the connector 2 can be attached and detached.

The connector 2 is provided with a signal terminal, a power supply terminal and a ground terminal, and the signal terminal is the printed circuit board 1.
The power supply terminal is connected to the power supply pattern in the upper signal pattern. The ground terminal is connected to the ground plane 1a in the inner layer.

FIG. 2 is a view showing the pattern shape of the ground plane 1a formed on the inner layer surface of the printed board 1. In FIG. 2, the mounting positions of the connector 2 and the EMI filter 3 are indicated by dotted lines. The ground plane 1a is
Basically, the pattern is formed by a solid pattern, and the pattern is removed only at the positions of the through holes 4 on the printed circuit board 1, the signal terminal positions of each mounting component, and the slit positions described later. The periphery of the through hole 4 (through hole 4 so that the ground plane 1a is electrically connected to the metal case 6 when the metal plate 5 is inserted into the through hole 4 and the printed circuit board 1 and the metal case 6 are fixed to each other.
(Including the inner peripheral surface of) also has a ground pattern formed. That is, the ground of the printed circuit board 1 and the frame ground are electrically connected via the metal fitting 5.

Further, in the ground plane 1a, slits 7 (more specifically, inverted U-shapes) are formed substantially parallel to the direction in which the metal fittings 5 are arranged, and the slits 7 partially form a solid pattern. It is divided into two areas. Therefore, for example, even if a current including a high frequency noise component flows from the ground terminal of each mounted component on the printed board toward the ground plane 1a, this current cannot flow in the direction of the connector 2 due to the slit 7. Slit 7
Along the direction toward the metal fitting 5, and flows through the metal fitting 5 into the metal case 6. Therefore, the connector 2 and the EMI
The ground plane 1a around the filter 3 is not affected by high frequency noise.

As described above, in this embodiment, the slit 7 is formed in the ground plane 1a formed on the inner layer surface of the printed circuit board 1, and the current including the high frequency noise component flowing through the ground plane 1a flows around the connector 2. Instead, it is made to flow to the metal case 6 via the metal fitting 5, so that high frequency noise in the peripheral portion of the connector in the ground plane 1a can be efficiently reduced. That is, by forming the slit 7, it is possible to obtain the same effect as the one-point ground.

In the above embodiment, an example in which the slit 7 is formed in the ground plane 1a on the inner layer surface has been described. However, when the printed board 1 having no inner layer surface is used, the component mounting surface 1b or the solder surface is formed. Ground plane 1 mentioned above
A may be formed and a slit may be formed in a part thereof.

In the above embodiment, an example in which only one connector 2 is connected has been shown, but when a plurality of connectors 2 are mounted, each connector 2 is connected as shown in FIG. 3 (a). Slits 7 are formed for each, or as shown in FIG.
Slits 7 corresponding to the plurality of connectors 2 as shown in (b)
One may be formed. Further, in the above-described embodiment, the shape of the slit 7 is an inverted U shape, but the shape and forming position of the slit 7 are not limited to the above-described embodiment. That is, any shape may be used as long as it can guide a current flowing through the ground plane 1a and including a high-frequency noise component toward the metal fitting 5.

[0017]

As described in detail above, according to the present invention, the slits are formed in the ground plane formed in the peripheral portion of the connector and the metal fitting along the direction in which the metal fittings are arranged. A current containing a high frequency noise component can be passed through the metal case to the metal case, and the ground plane around the connector is not affected by the high frequency noise. According to the invention as set forth in claim 2, since the slit is formed so as to surround the connector, the current containing the high frequency noise component flowing in the direction of the connector can be reliably blocked by the slit, and the current can be passed along the slit. Can be guided in the direction of the metal fittings. According to the third aspect of the invention, since the ground plane is formed on the inner layer surface of the printed board, high density mounting is possible.

[Brief description of drawings]

FIG. 1 is a diagram for explaining an electric device with reduced high frequency noise according to the present invention.

FIG. 2 is a diagram showing a pattern shape of a ground plane formed on an inner layer surface of a printed board.

FIG. 3 is a diagram showing a slit shape when a plurality of connectors are connected on a printed circuit board.

FIG. 4 is a diagram simply showing a mechanism in which the potential level of the ground pattern fluctuates.

FIG. 5 is a diagram illustrating an outline of a one-point ground.

[Explanation of symbols]

1 printed circuit board 2 connectors 3 EMI filter 4 through holes 5 metal fittings 6 openings

Claims (3)

(57) [Claims] 1. A high frequency noise reduction device comprising a printed circuit board to which a connector for an external interface is attached.
In the electric device , through holes are formed on both sides of the connector in a direction substantially orthogonal to the mounting / removing direction of the connector in the printed circuit board, and a ground plane is formed in the peripheral portion of the connector and the metal fitting. , Fixing the metal case of the electric device and the printed circuit board by inserting a metal fitting into the through hole, and in the ground plane such that a current including a high frequency noise component flowing through the ground plane flows toward the metal fitting. An electric device with reduced high frequency noise , characterized in that a slit having a predetermined width and a predetermined length is formed along the direction in which the metal fittings are arranged. 2. The connector is attached to an end portion of the printed circuit board, and the slit is formed so as to surround the connector except a surface facing the end portion of the connector. Electricity with reduced high frequency noise described in
Equipment . 3. The high frequency noise according to claim 1, wherein the ground plane is formed on an inner layer surface of the printed board.
Electrical equipment .