JP3615098B2 - Computer support system and layout CAD display method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a bypass capacitor (bulk capacitor) and a snubber circuit inserted between a power plane and a ground plane in order to prevent resonance between power planes and a ground plane and reduce EMI noise in a printed circuit board (PCB) layout design. The present invention relates to a layout design assisting system for realizing a low EMI design of a PCB that makes it possible to indicate an effective insertion position.
[0002]
[Prior art]
Conventionally, the three-dimensional behavior of the electromagnetic field is analyzed, the resonance between the power plane and the ground plane is analyzed to obtain the resonance mode, and based on this result, the EMI noise is reduced to reduce the EMI noise between the power plane and the ground plane. Although it was possible to examine the effective insertion position of the bulk capacitor to be inserted, it takes a lot of calculation time to analyze the three-dimensional behavior of the electromagnetic field and cannot be used in daily design work.
[0004]
[Problems to be solved by the invention]
For the above-described conventional printed circuit board having a general shape, there is no method for accurately obtaining the resonance mode in a short time. There was a problem.
Therefore, the present invention has been made to solve the above-described problem, and by utilizing the fact that the resonance mode between the power plane and the ground plane is a TM wave which is a form of microwaves, the governing equation of electromagnetic waves is obtained. Efficient insertion position of bulk capacitor to be inserted between power plane and ground plane based on this resonance mode by solving simplified and simplified equation by finite element method to find resonance mode between power plane and ground plane The system which shows is realized. In this system, the calculation time required for rigorous analysis of the resonance frequency and resonance mode of electromagnetic waves is only a few minutes, so that the configuration incorporated in the layout CAD system has novelty and feasibility as an invention. . Thereby, the insertion position of the bulk capacitor by the system of the present invention can be adopted as the insertion position of the snubber circuit, and the efficiency of the EMI reduction design is greatly improved.
[0005]
[Means for Solving the Problems]
The present invention is an interface unit and the data from the layout CAD system is input; input via the said interface unit the data indicating the ground portion of the PCB that is specified on the layout CAD, the outer peripheral shape of the ground portion A PCB ground outer shape extracting unit for extracting data; a PCB ground outer shape finite element for automatically generating finite element method mesh data of the ground outer shape from the outer shape data of the ground portion extracted by the PCB ground outer shape extracting unit; Law mesh automatically generating unit and; a finite element mesh data of the ground outer peripheral shape that is automatically generated by the PCB ground peripheral shape FEM mesh automatically generating unit, and a dielectric constant data of the PCB dielectric PCB of Resonance mode between power plane and ground plane A resonance mode calculation unit between the power plane and the ground plane that calculates the power as a TM wave; and a bulk inserted between the power plane and the ground plane based on the resonance mode calculated by the power plane / ground plane resonance mode calculation unit. A computer-aided system comprising: a bulk capacitor insertion portion display unit for displaying a capacitor insertion position; and diagnosing a bypass capacitor or snubber circuit insertion position. In addition, the present invention provides a storage unit that stores board data, an insertion position diagnosis unit that diagnoses an insertion position of a bypass capacitor or a snubber circuit inserted between a power plane and a ground plane of the printed circuit board, and the insertion position. A display processing unit for visually displaying the analysis result by the diagnosis unit, and the insertion position diagnosis unit receives data indicating the ground portion of the PCB designated on the layout CAD from the storage unit as an interface unit. type via extracts data of the outer shape of the ground portion, from the data of the peripheral shape of the extracted ground portion, a finite element method mesh data of the ground peripheral shape automatically generated, which is the auto-generated ground and finite element method mesh data of the outer shape, Pawapu the PCB from the dielectric constant data of the dielectric of the PCB The resonance mode between over down ground plane calculated as TM wave, based on the calculated resonance mode, color-coded depending on the need of the insertion position of the bulk capacitor inserted between the power plane ground plane, said In the display processing unit, a layout CAD display method is characterized in that an insertion position of a bypass capacitor or a snubber circuit is highlighted as necessary.
[0006]
According to such a configuration, the calculation time required for the rigorous analysis of the resonance frequency / resonance mode of the electromagnetic wave is only a few minutes, so the novelty of the invention is that the configuration incorporated in the layout CAD system is taken. And there is feasibility. The bulk capacitor insertion position indicated by this system can also be adopted as the insertion position of the snubber circuit, and the efficiency of EMI reduction design is greatly improved.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
As shown in FIG. 1, the system according to the present embodiment includes a bypass capacitor and snubber circuit insertion position diagnostic unit 1, a storage unit 2 that stores substrate data, and a display process for visually displaying analysis results. Part 3. (The basic part of the layout CAD system: explanation of CPU, memory and keyboard is omitted).
[0008]
(1) Bypass capacitor and snubber circuit insertion diagnosis unit 1 includes an interface unit 11 with a layout CAD system, a PCB ground outer shape extraction unit 12, a PCB ground outer periphery shape finite element method mesh automatic generation unit 13, a power plane ground Bypass capacitor and snubber circuit insertion position comprising an interplane resonance mode calculation unit 14 (using the finite element method), a bulk capacitor insertion position calculation unit 15 (using the resonance mode calculation result), and a bulk capacitor insertion position display unit 16 Diagnostic software.
[0009]
(2) When a ground is displayed on the layout CAD system and an arbitrary ground is designated, the layout CAD data of the ground passes through the interface unit 11 to the PCB ground outer peripheral shape extraction unit 12, and the outline of the ground is extracted. (Figure 2)
(3) The PCB ground outer periphery shape finite element method mesh automatic generation unit 13 automatically generates ground outer periphery shape finite element method mesh data from the ground outer shape data. (Figure 3)
(4) The power plane / ground plane resonance mode calculation unit 14 uses the finite element method mesh data of the outer periphery of the ground and the relative permittivity data of the dielectric to determine the resonance between the power plane and the ground plane as an eigenvalue problem (Helmholtz problem). To obtain the resonance frequency and resonance mode.
[0010]
(5) The bulk capacitor insertion position calculation unit 15 calculates the necessity of insertion of the bulk capacitance on the node of the finite element method by some algorithm.
(6) In the bulk capacitor insertion display unit 16, the insertion necessity obtained by the bulk capacitor insertion position calculation unit 15 is emphasized by color coding or the like so that a portion having a high insertion necessity is made conspicuous. (Fig. 4)
Based on this display, the layout CAD operator knows the insertion position of the bulk capacitor based on the drawing of the bulk capacitor insertion display unit 16 and inserts the bulk capacitor or the snubber circuit.
[0011]
【The invention's effect】
As described above, according to the present invention, since the calculation time required for the rigorous analysis of the resonance frequency and resonance mode of electromagnetic waves is only a few minutes, the optimum bulk capacitor insertion is performed at the time of layout design using the layout CAD system. The insertion position of the position-reducing snubber circuit can be pointed out, and the efficiency of the EMI reduction design can be greatly improved.
[Brief description of the drawings]
FIG. 1 is a block diagram according to an embodiment of the present invention.
FIG. 2 is an outline drawing of a PCB ground extracted from substrate data.
FIG. 3 is a diagram in which a finite element mesh is generated for analysis of the PCB ground outline.
FIG. 4 is a diagram showing a bulk capacitor insertion position (analysis result).
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Snubber circuit insertion position diagnostic part, 2 ... Memory | storage part, 3 ... Display processing part, 11 ... Interface part, 12 ... PCB ground outer shape extraction part, 13 ... PCB ground outer periphery shape finite element method mesh automatic generation part, 14 ... Power plane / ground plane resonance mode calculation section, 15... Bulk capacitor insertion position calculation section, 16... Bulk capacitor insertion position display section.

Claims (2)

In a system that supports the design of a printed circuit board (PCB) layout,
An interface unit for inputting data from the layout CAD system;
The data indicating the ground portion of the specified PCB in the layout CAD is input via the interface unit, and the PCB ground outer peripheral shape extraction section for extracting data of the outer shape of the ground portion,
A PCB ground outer shape finite element method mesh automatic generation unit that automatically generates finite element method mesh data of the ground outer shape from the data of the outer shape of the ground portion extracted by the PCB ground outer shape extraction unit;
Resonance between the power plane and the ground plane of the PCB from the finite element method mesh data of the ground outer periphery shape automatically generated by the PCB ground outer periphery shape finite element method mesh automatic generation unit and the relative permittivity data of the PCB dielectric. Resonance mode calculator between power plane and ground plane that calculates the mode as TM wave,
The power plane / ground plane resonance mode calculation unit includes a bulk capacitor insertion unit display unit that displays the insertion position of the bulk capacitor to be inserted between the power plane / ground plane based on the calculated resonance mode,
A computer-aided system for diagnosing the insertion position of a bypass capacitor or snubber circuit. A layout CAD display method for supporting layout design of a printed circuit board (PCB) , comprising a storage unit storing circuit board data and a bypass capacitor or a snubber circuit inserted between a power plane and a ground plane of the printed circuit board. An insertion position diagnosis unit for diagnosing an insertion position; and a display processing unit for visually displaying an analysis result by the insertion position diagnosis unit,
The data indicating the ground portion of the PCB that is specified in the layout CAD from the storage unit and input through the interface unit extracts data of the outer shape of the ground portion,
From the data of the peripheral shape of the extracted ground portion, a finite element method mesh data of the ground peripheral shape is automatically generated,
The resonance mode between the power plane and the ground plane of the PCB is calculated as a TM wave from the automatically generated ground outer peripheral shape finite element method mesh data and the relative dielectric constant data of the PCB dielectric,
Based on said calculated resonance mode, color-coded depending on the need of the insertion position of the bulk capacitor inserted between the power plane ground plane,
A layout CAD display method characterized in that, in the display processing unit, an insertion position of a bypass capacitor or a snubber circuit is highlighted as necessary.

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