JP5437558B2 - Electromagnetic noise countermeasure structure for printed circuit boards - Google Patents

Description

  The present invention relates to an electromagnetic noise countermeasure structure for a printed circuit board.

  The ground (hereinafter referred to as “GND”) formed on the printed circuit board includes a power supply GND, a signal GND for supplying a return current, a frame GND for supplying a reference potential, and the like. Further, the signal GND includes a GND in an analog circuit and a GND in a digital circuit, and a GND corresponding to a frequency band handled by the analog circuit, for example, is provided. The same applies to digital circuits.

  These GNDs are heterogeneous GNDs that cannot be directly connected to each other because they directly interfere with each other as noise when they are directly connected to each other. On the other hand, when these different types of GND are adjacent to each other, if the GND is not connected, the potential between the two GNDs is not stable, becomes a source of electromagnetic noise, and is vulnerable to noise intrusion from the outside. There is a problem.

  As an electromagnetic noise countermeasure method for GND formed on a printed circuit board, for example, in Patent Document 1, in a multi-layer board in which an analog circuit and a digital circuit are mixedly mounted, an analog ground provided on a surface layer and an intermediate layer are provided. A method of reducing interlayer noise by connecting a capacitor to the digital ground is disclosed.

  For example, in Patent Document 2, in a circuit board on which an analog circuit block and a digital circuit block are mixedly mounted on the same plane, a plurality of electronic components (electrolytic capacitors) are provided between the analog circuit block and the digital circuit block. Are arranged side by side and shielded from each other to thereby reduce the mixing of high frequency noise from the digital circuit block to the analog circuit block.

JP 2001-284828 A JP 2006-165035 A

  However, the electromagnetic noise countermeasure methods described in Patent Documents 1 and 2 are both electromagnetic noise countermeasure methods for signal GND, and between analog GND and digital GND, and are adjacent to the same kind of circuit. There has not yet been proposed an effective electromagnetic noise countermeasure method that can be applied when the above-mentioned various types of GND are adjacent to each other, such as between different types of GND, or between adjacent frame GND and signal GND.

  In recent years, the international standard CISPR (International Radio Interference Special Committee) for electromagnetic interference EMI (Electro Magnetic Interference) due to unwanted radiation radiated from electronic equipment, and the international standard IEC (International There is a request that the Electrotechnical Commission) be established and observed.

  The present invention has been made in view of the above. When there are two GNDs that cannot be directly connected due to a difference in characteristics on the same substrate surface, reduction of unnecessary radiation noise due to the two GNDs and external noise can be prevented. An object of the present invention is to obtain an electromagnetic noise countermeasure structure for a printed circuit board that can improve resistance.

  In order to achieve the above-described object, in the present invention, when two grounds arranged adjacent to each other on the same board surface cannot be directly connected due to a difference in characteristics, the two grounds are It is connected through any one circuit element of a resistor element, a capacitor, and an inductor.

  According to the present invention, since the potential between two GNDs that cannot be directly connected due to the difference in characteristics can be stabilized, it is possible to reduce unnecessary radiation noise and improve resistance to external noise.

  According to the present invention, when there are two GNDs that cannot be directly connected due to a difference in characteristics on the same substrate surface, it is possible to reduce unnecessary radiation noise and improve resistance to external noise by the two GNDs. There is an effect.

  Exemplary embodiments of an electromagnetic noise countermeasure structure for a printed circuit board according to the present invention will be described below in detail with reference to the drawings.

Embodiment 1 FIG.
FIG. 1 is a conceptual diagram showing the configuration of an electromagnetic noise countermeasure structure for a printed circuit board according to Embodiment 1 of the present invention. In FIG. 1, GND1 and GND2 arranged adjacent to the same board surface of the printed circuit board are heterogeneous GNDs that cannot be directly connected due to their characteristic differences. As such a different type GND, there are various types such as a power supply GND and a signal GND, a frame GND and a signal GND, a GND in an analog circuit and a GND in a digital circuit, and a different type GND adjacent to the same type circuit.

  In such a case, in the first embodiment, GND1 and GND2 are connected via a circuit element 3 of any one of a resistance element, a capacitor, and an inductor, and the potential between the two GNDs is connected. So that countermeasures against electromagnetic noise can be taken.

  According to this configuration, the objective is to clear international standards CIRPR (publ.11 etc .: radiated electromagnetic field), IEC (61000-4-2 etc .: electrostatic immunity) or to reduce other unnecessary radiated noise. It is possible to easily cope with this problem by selecting an appropriate circuit element depending on whether the purpose is to improve the resistance against external noise.

  As a specific example, a capacitor of 1000 pF to 10000 pF is used for the circuit element 3 in response to a request for reduction of radiation noise of 30 MHz to 1000 MHz defined in the international standard CIRPR (publ. 11 etc.). In particular, when GND1 is an audio circuit and GND2 is a digital circuit, by setting a capacitance value of 1000 pF to 10000 pF, a noise component of 1 MHz or less that affects the audio circuit is not mixed from the digital circuit to the audio circuit. Only a noise component of 30 MHz to 1000 MHz can be taken.

  Further, in order to meet the demand for improvement in electrostatic immunity defined by IEC (61000-4-2 etc.), a capacitor of 1000 pF to 1 μF is used for the circuit element 3.

  In order to improve other static electricity immunity, a resistance element having a resistance value of about 100Ω to 1 kΩ is used for the circuit element 3, and a noise component is dissipated by the resistance element. In addition, as another measure for reducing unnecessary radiation noise, GND1 and GND2 are physically insulated, but in the case where the DC level is desired to be the same, an inductor is used for the circuit element 3 so that a minute direct current flows. To.

  As described above, according to the first embodiment, even when there are two GNDs that cannot be directly connected to the same substrate surface, the potential between them can be stabilized. Electromagnetic noise immunity can be improved. As a result, it is possible to increase the possibility of conforming to the international standards CIRPR (publ.11 etc .: radiated electromagnetic field) and IEC (61000-4-2 etc .: electrostatic immunity), which have conventionally been difficult to take countermeasures. In addition, there is a possibility that an effect can be expected to reduce other unnecessary radiation noise and improve noise immunity.

Embodiment 2. FIG.
FIG. 2 is a conceptual diagram showing a configuration of an electromagnetic noise countermeasure structure for a printed circuit board according to Embodiment 2 of the present invention. As shown in FIG. 2, in the second embodiment, the two grounds 1 and 2 are provided with a plurality of pads 4 on opposite sides, respectively, so that the circuit elements 3 can connect between the pads selected as necessary. I have to.

  According to this configuration, the optimum connection location and number can be selected as appropriate.

Embodiment 3 FIG.
FIG. 3 is a conceptual diagram showing a configuration of an electromagnetic noise countermeasure structure for a printed circuit board according to Embodiment 3 of the present invention. As shown in FIG. 3, in the third embodiment, the two grounds 1 and 2 in the configuration shown in FIG. 2 are separated by an interval 5 sufficient to avoid electromagnetic induction.

  According to this configuration, it becomes possible to eliminate uncertain factors for noise countermeasures. In the third embodiment, an example of application to the second embodiment has been described. Needless to say, the third embodiment can be similarly applied.

  As described above, the printed circuit board electromagnetic noise countermeasure structure according to the present invention reduces unnecessary radiation noise caused by two GNDs when there are two GNDs that cannot be directly connected due to the difference in characteristics on the same board surface. In particular, electronic devices that are required to have low radiation electromagnetic wave level and high noise resistance at the same time (for example, electronic devices for automobiles, personal computers and their peripheral devices, electronic devices) Suitable for application to medical equipment, measuring equipment, industrial equipment, etc.

It is a conceptual diagram which shows the structure of the electromagnetic noise countermeasure structure of the printed circuit board by Embodiment 1 of this invention. It is a conceptual diagram which shows the structure of the electromagnetic noise countermeasure structure of the printed circuit board by Embodiment 2 of this invention. It is a conceptual diagram which shows the structure of the electromagnetic noise countermeasure structure of the printed circuit board by Embodiment 3 of this invention.

Explanation of symbols

1, 2 Ground (GND)
3 circuit element 4 pad 5 gap

Claims (1)

In a printed circuit board, when two grounds arranged adjacent to each other on the same board surface cannot be directly connected due to a difference in characteristics,
The two grounds are connected via a circuit element of any one of a resistance element, a capacitor, and an inductor,
Each of the two grounds has a plurality of convex patterns at positions corresponding to each other on opposite sides,
The two grounds are circuit elements only between one convex pattern selected from the plurality of convex patterns on one side and one convex pattern selected from the plurality of convex patterns on the other side. Connected with
The circuit element is a resistance element of 100Ω to 1 kΩ,
Each of the two grounds has a substantially rectangular shape,
In the two grounds, the plurality of convex patterns in one ground are arranged on the side facing the other ground while being spaced apart from each other, and extend so as to approach the other ground. The first width and the second width wider than the first width are included as the width in the direction along the side facing the first, and the first spacing is the spacing in the direction along the side facing the other ground . An interval and a second interval wider than the first interval;
In the two grounds, the plurality of convex patterns in the other ground are arranged on the side facing the one ground while being spaced apart from each other, and extend so as to approach one ground. The first width and the second width are included as the width in the direction along the side facing the first, and the first distance and the second width are separated as the spacing in the direction along the side facing the one ground . An electromagnetic noise countermeasure structure for a printed circuit board, characterized by comprising an interval of 2 .

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