JP2019161857A - Power supply board - Google Patents

Abstract

To provide a power supply board that can avoid an increase in substrate area and reduce a parasitic capacitance compared with a prior art.SOLUTION: A power supply board according to the present invention is a power supply board including a support formed with a power supply circuit including a switching element, and comprises: a first electrode that is formed on a first surface of the support, wherein the potential changes over time according to the operation of the switching element; and a second electrode that is formed on a second surface of the support, wherein the potential does not change over time according to the operation of the switching element, wherein the second electrode has an opening formed in at least part of a portion facing the first electrode. The opening of the second electrode may be formed in a portion facing the first electrode. The opening of the second electrode may further be formed in a portion other than the portion facing the first electrode.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a power supply substrate such as a switching power supply substrate including a switching element for a power converter such as an inverter.

  In recent years, for example, switching power supply boards including switching elements for inverters and the like are used in various devices, but noise generated from the switching power supply boards is generated and is required to be suppressed. Specifically, due to the parasitic capacitance between the circuit pattern whose potential changes with time on the power supply board and the ground conductor, conduction noise (which is a noise component propagating on the path of the electric circuit, also called miscellaneous noise) is generated. Therefore, it has become necessary to take measures for noise and add additional members.

  In order to solve the above problems, various solutions have been proposed in the following patent documents.

  In Patent Document 1, the first and second electrodes are configured so that the parasitic capacitance between the first electrode and the ground conductor is equal to the parasitic capacitance between the second electrode and the ground conductor. Therefore, it has been proposed to suppress noise generated in the potential fluctuation pattern.

  In Patent Document 2, a noise filter is provided between the high-voltage switching circuit unit and the low-voltage switching circuit unit, and a metal plate that shields noise is formed between the substrate and the noise filter. It has been proposed to shield.

Furthermore, Patent Document 3 proposes a wiring board having the following configuration.
(1) A first wiring conductor for propagating a high-frequency signal of 5 GHz or more is formed on one main surface of the insulating substrate so that the distance from each other increases from the center to the outer periphery.
(2) Between the first wiring conductor on one main surface of the insulating substrate, the grounding or power supply conductor layer is opposed to the following second wiring conductor halfway from the outer periphery toward the center. It is formed so that there is no conductor layer at the site.
(3) A second wiring conductor is formed on the other main surface of the insulating substrate from the central portion to the outer peripheral portion.
Here, the high-frequency signal is prevented from being reflected and attenuated by suppressing the impedance of the wiring applied to the second wiring conductor from changing in the middle.

JP 2009-261044 A JP 2014-033531 A JP 2005-191142 A

  However, the above conventional example has the following problems.

  In Patent Document 1, there is a problem that the formation of the second electrode increases the substrate area, and the parasitic capacitance itself cannot be reduced.

  Moreover, in patent document 2, although radiation noise is shielded and reduced with a metal plate, there existed a subject that a structure became complicated and cost increased.

  Further, in Patent Document 3, although a high-frequency signal can be reflected and attenuated, there is a problem that the substrate area becomes large and the parasitic capacitance itself cannot be reduced.

  An object of the present invention is to solve the above-described problems, and to provide a power supply substrate capable of avoiding an increase in substrate area and reducing parasitic capacitance as compared with the prior art.

A power supply board according to one embodiment of the present invention is provided.
A power supply substrate including a support on which a power supply circuit including a switching element is formed,
A first electrode formed on the first surface of the support, the potential of which varies with time according to the operation of the switching element;
A second electrode formed on the second surface of the support, the potential of which does not change with time by the operation of the switching element,
The second electrode has an opening formed in at least a part of a portion facing the first electrode.

  In the power supply substrate, the opening of the second electrode is formed in a portion facing the first electrode.

  In the power supply substrate, the opening of the second electrode is further formed in a portion other than the portion facing the first electrode.

  Further, in the power supply substrate, the power supply substrate further includes a third electrode formed on the first surface of the support so as to surround the first electrode.

  Still further, in the power supply substrate, the switching element is connected to the first electrode and the third electrode.

Still further, in the power supply board,
The second electrode is formed on the inner layer of the support,
The first electrode is connected to a fourth electrode through a via conductor formed in the support.

  Therefore, according to the power supply substrate according to the present invention, it is possible to reduce conduction noise by avoiding an increase in the substrate area and reducing the parasitic capacitance as compared with the prior art.

It is a longitudinal cross-sectional view which shows the structural example of the power supply board concerning a basic example. FIG. 2 is a circuit diagram illustrating a circuit example including a switching element used in the power supply substrate of FIG. 1. It is a longitudinal cross-sectional view which shows the structural example of the power supply board concerning a prior art example. FIG. 4 is a circuit diagram illustrating a circuit example including a switching element used in the power supply substrate of FIG. 3. 6 is a graph showing a characteristic example of a conduction noise level with respect to a parasitic capacitance Cp in the circuit of FIG. 6 is a configuration example of a power supply board according to the first embodiment, and is a longitudinal sectional view taken along line A-A ′ of FIG. 6B. FIG. It is a top view of the power supply board of FIG. 6A. It is a longitudinal cross-sectional view which shows the structural example of the power supply board concerning the modification of Embodiment 1. It is a graph which shows the example of a characteristic of the parasitic capacitance Cp with respect to length la of FIG. FIG. 9B is a configuration example of the power supply board according to the second embodiment and is a longitudinal sectional view taken along line B-B ′ of FIG. 9B. It is a top view of the power supply board of FIG. 9A. It is a bottom view of the power supply board of FIG. 9A. FIG. 10 is a configuration example of a power supply board according to Modification 1 of Embodiment 2, and is a longitudinal sectional view taken along line C-C ′ of FIG. 10B. It is a top view of the power supply board of FIG. 10A. It is a bottom view of the power supply board of FIG. 10A. It is a longitudinal cross-sectional view which shows the structural example of the power supply board concerning the modification 2 of Embodiment 2. FIG. It is a longitudinal cross-sectional view which shows the structural example of the power supply board concerning Embodiment 3. FIG. It is a basic example, a prior art example, it is a graph which shows the parasitic capacitance Cp, as a simulation result of the power supply board concerning Embodiment 1 and 2. FIG. It is a basic example, a prior art example, and the simulation result of the power supply board concerning Embodiment 1 and 2, Comprising: It is a graph which shows the electric field strength Ep. It is a photographic image which is a simulation result of the power supply board concerning a basic example, a prior art example, and Embodiments 1 and 2, and shows electric field strength Ep.

  Hereinafter, a comparative example and an embodiment according to the present invention will be described with reference to the drawings. In the following embodiments, the same or similar components are denoted by the same reference numerals.

  The present inventors are studying countermeasures against conduction noise and radiation noise in a power supply board such as a switching power supply board including a switching element for a power converter such as an inverter. It has been found that there is a big problem with noise and radiation noise. As a countermeasure, the solution according to the present embodiment was considered. In particular, the present inventors have increased radiation noise in a power converter using a switching element of a new material (GaN) device, and electric field radiation is generated particularly from an edge of a circuit pattern in which potential fluctuation occurs by simulation. It was confirmed. On the other hand, it has been found that the conduction noise increases when the circuit pattern of the potential fluctuation and the parasitic capacitance of the ground potential are large, and the power supply substrate according to the following embodiment has been devised as a technique for solving these problems. In the power supply board according to the present embodiment, noise countermeasures can be reduced by changing the pattern shape so that the conduction noise from the circuit pattern is reduced. Details will be described below.

  FIG. 1 is a longitudinal sectional view showing a configuration example of a power supply board according to a basic example. FIG. 2 is a circuit diagram showing a circuit example including a switching element used in the power supply substrate of FIG.

  In FIG. 1, an electrode 11 is formed on a dielectric substrate (power supply substrate) 10 which is a support. The booster circuit shown in FIG. 2 includes an inductor L1, a diode D1, and a power supply circuit including a switching element SW1 such as a MOSFET. In the booster circuit of FIG. 2, the potential of the circuit portion A varies depending on the switching operation of the switching element SW1. In such a case, an alternating electric field E is generated between the electrode 11 corresponding to the circuit portion A provided on the dielectric substrate 10 and a surrounding metal part such as a housing for housing the booster circuit or a heat sink, As a result, the radiation noise to the outside of the housing is increased.

  FIG. 3 is a longitudinal sectional view showing a configuration example of a power supply substrate according to a conventional example. 4 is a circuit diagram showing a circuit example including a switching element used in the power supply substrate of FIG.

  As a method of suppressing the radiation electric field from the power supply substrate, it is conceivable to provide an electrode 12 with a stable potential (for example, a ground potential) in the vicinity of the electrode 11 as shown in FIG. In this case, the spread of the radiation electric field generated from the electrode 11 is suppressed by coupling with the nearby electrode 12. However, since the parasitic capacitance Cp of the electrode 11 and the electrode 12 becomes large, it is considered that the conduction noise component generated through the parasitic capacitance Cp increases.

  FIG. 5 is a graph showing a characteristic example of the conduction noise level with respect to the parasitic capacitance Cp in the circuit of FIG. As is apparent from FIG. 5, when the parasitic capacitance Cp between the electrode 11 whose potential varies and the grounded electrode 12 is large, the current component flowing in the electrodes 11 and 12 increases when the potential of the electrode 11 varies. Here, the current component that flows to the ground-side electrode 12 due to the potential fluctuation flows back through another part of the electric circuit, resulting in an increase in the conduction noise component that flows through the path due to switching of the switching element. there were.

Embodiment 1. FIG.
6A is a configuration example of the power supply substrate according to the first embodiment, and is a longitudinal sectional view taken along line AA ′ of FIG. 6B. FIG. 6B is a plan view of the power supply substrate of FIG. 6A.

  6A and 6B, a rectangular electrode 11 is formed on the upper surface of the dielectric substrate 10, and a rectangular opening having a substantially the same size is positioned on the lower surface of the dielectric substrate 10 in a position range facing the electrode 11. An electrode 12 having a portion 12C is formed. Thereby, the electrode 12 has a rectangular ring shape. That is, in the present embodiment, the electrode 12 having the ground potential that is not connected to the switching element and does not change in potential is formed in a plane facing the electrode 11 that is connected to the switching element and changes in potential with time. It is characterized by that. Here, at least a part of the electrode 12 has a structure that protrudes outward from the electrode 11, and the opening 12 </ b> C is formed in at least a part of the part directly facing the electrode 11 in the vertical direction.

  In the power supply substrate configured as described above, since the electrode 12 having the ground potential is in the vicinity of the electrode 1, the radiated electric field generated from the electrode 11 is electromagnetically coupled to the electrode 12, and the dielectric substrate 10 By being confined and suppressed, the radiation field component to the outside is reduced. Further, since the radiation electric field from the electrode 11 is particularly strong at the edge portion, the diffusion of the radiation electric field can be effectively reduced by making the contour size of the electrode 12 larger than that of the electrode 11.

  In addition, you may comprise so that the opening part 12C of the electrode 11 and the electrode 12 may not be a structure which mutually opposes mutually. In this case, by providing the opening 12C, the parasitic capacitance Cp between the electrode 11 and the ground potential electrode 12 can be reduced as compared with the structure that completely faces each other as described above. As a result, the current change caused by the potential fluctuation is not so large, and the conduction noise component in the circuit of the power supply substrate that is increased by providing the electrode 12 can be suppressed.

  In the first embodiment, the opening 12 </ b> C of the electrode 12 may be formed in at least a part of the portion facing the electrode 11.

  A comparison of the parasitic capacitance Cp between the power supply substrate of the conventional example and the power supply substrate of the first embodiment will be described later with reference to FIG. 12, but the parasitic capacitance Cp of the conventional example is 1.49 pF. The parasitic capacitance Cp is 1.18 pF, which is about 20% reduced.

Modified example of the first embodiment.
FIG. 7 is a longitudinal sectional view showing a configuration example of a power supply substrate according to a modification of the first embodiment. FIG. 8 is a graph showing a characteristic example of the parasitic capacitance Cp with respect to the length la in FIG.

  The power supply substrate of FIG. 7 is characterized in that the size of one side of the rectangle of the opening 12C of the electrode 12 is increased by the length + 2la, compared to the power supply substrate of FIG. 6A. That is, as shown in FIG. 7, the opening 12 </ b> C has a rectangular shape that is larger by a length + la on each side from the rectangular portion when the electrode 11 is projected onto the formation surface of the electrode 12. This length + la is a gap of a predetermined length between the electrode 11 and the electrode 12 when the electrode 11 is projected onto the formation surface of the electrode 12.

  For example, in the present modification, as is apparent from FIG. 8, it can be seen that by setting the length la = 4 mm, the parasitic capacitance Cp can be suppressed and the electric field strength Ep can also be suppressed to a certain level or less.

Embodiment 2. FIG.
FIG. 9A is a configuration example of the power supply substrate according to the second embodiment, and is a longitudinal sectional view taken along line BB ′ of FIG. 9B. 9B is a top view of the power supply board of FIG. 9A, and FIG. 9C is a bottom view of the power supply board of FIG. 9A.

  The power supply substrate in FIG. 9A is rectangular with a predetermined opening 13C (rectangular ring-shaped gap) outside the electrode 11 on the front surface of the dielectric substrate 10 as compared with the power supply substrate in FIG. 6A. A ring-shaped electrode 13 (floating electrode) is formed so as to surround the electrode 11. Here, the electrode 13 has a constant potential around the electrode 11 in the same plane as the electrode 11. Thereby, the electric field component generated on the upper side from the electrode 11 is coupled to the electrode 13, whereby the electric field radiated on the upper side is further suppressed. Here, since it is necessary to keep the insulation distance between the electrode 13 and the electrode 11, the inner size of the opening 13C of the electrode 13 is larger than the inner size of the opening 12C of the electrode 12.

  According to the simulation results of the second embodiment by the present inventors, in addition to the structure of the first embodiment, an electrode 13 having a width of 2 mm is provided around the electrode 11 with a gap of lb = 3 mm from the end of the electrode 11 in the periphery. In this case, it was found that the radiation electric field from the upper surface of the dielectric substrate 10 was further suppressed than in the first embodiment. This is because the structure is such that radiation from the edge of the electrode 11 is more likely to be coupled to a nearby ground plane.

  The effects of the simulation results of the examples configured as described above are shown in Table 1 below.

  Here, x indicates the influence of conduction noise or radiation noise, and the evaluation is low (low evaluation). ○ indicates that there is almost no influence of conduction noise or radiation noise, and the evaluation is relatively high (high evaluation). A indicates that the evaluation is very high without being affected by conduction noise or radiation noise (high evaluation). In addition, (triangle | delta)-* shows the evaluation between intermediate evaluation which is evaluation between low evaluation and high evaluation, and high evaluation, and (circle)-(◎) shows evaluation between high evaluation and the highest evaluation.

  As is apparent from Table 1, it is expected that the parasitic capacitance Cp is reduced and the conduction noise is improved by the power supply substrate of the first embodiment. Furthermore, the power supply board of Embodiment 2 is also expected to improve radiation noise. In general, the parasitic capacitance Cp and the electric field strength Ep are in a trade-off relationship.

Modification 1 of Embodiment 2
FIG. 10A is a configuration example of a power supply board according to the first modification of the second embodiment, and is a longitudinal sectional view taken along the line CC ′ of FIG. 10B. 10B is a top view of the power supply board of FIG. 10A, and FIG. 10C is a bottom view of the power supply board of FIG. 10A.

  The power supply board of FIG. 10A is characterized in that a switching element 14 having two terminals connected to the electrode 11 and the electrode 13 is mounted on the electrodes 11 and 13 as compared with the power supply board of FIG. 9A. In this example, in order to surround the electrode 11 with the electrode of the switching element 14, a missing portion is generated in the electric field radiated from the electrode 11, but the periphery can be completely surrounded by using the electrode of the switching element 14.

Modification 2 of Embodiment 2
FIG. 10D is a longitudinal sectional view illustrating a configuration example of a power supply substrate according to the second modification of the second embodiment. The power supply board of FIG. 10D is characterized in that the rectangular ring-shaped electrode 13 is deleted as compared with the power supply board of FIG. 10A, and may be configured in this manner. In other words, the power supply substrate of FIG. 10D is characterized in that the switch element 14 is provided as compared with the power supply substrate of FIG. 6A.

  FIG. 11 is a longitudinal sectional view illustrating a configuration example of a power supply substrate according to the third embodiment.

  In the power supply substrate of FIG. 11 according to the third embodiment, it is assumed that a heating element 14 </ b> A of an active element such as a switching element or a diode is provided in the vicinity of the electrode 11. In FIG. 11, the electrode 12 is provided on the inner layer surface of the dielectric substrates 10 and 10A. Reference numeral 30 denotes a housing sheet metal for confining a radiation electric field radiated from the power supply substrate. A plurality of electrodes 15 extending in the thickness direction from the electrode 15 formed on the lower surface of the dielectric substrate 10A via the dielectric substrate 10, the opening 12C of the electrode 12 and the dielectric substrate 10A and connected to the electrode 11 are connected. The via conductor 16 is provided. Thereby, the via conductor 16 can connect the electrode 11 to the electrode 15, thereby improving the heat dissipation from the back surface of the substrate.

  Actually, the electrode 15 is connected to the heat radiating portion 20 through a thermal interface material (hereinafter referred to as TIM (Thermal Interface Material) 21), and the dielectric substrates 10 and 10A extend in the vertical direction from the heat radiating portion 20. Are supported by a plurality of support members 22.

  According to the power supply substrate according to the third embodiment configured as described above, it is possible to achieve both suppression of the radiation electric field and heat dissipation of the substrate.

  In the third embodiment described above, the via conductor 16 may be formed of an inlay or the like. Moreover, since TIM has high thermal conductivity and desirably has a relatively large thickness (that is, the parasitic capacitance with the heat radiation portion is small), it is made of a material such as ceramic such as silicon nitride.

  Hereinafter, the simulation results of the present inventors will be described.

  FIG. 12 is a graph showing the parasitic capacitance Cp, which is a simulation result of the power supply substrate according to the basic example, the conventional example, and the first and second embodiments. As can be seen from FIG. 12, the parasitic capacitance Cp in the first and second embodiments is reduced as compared with the conventional example.

  FIG. 13 is a graph showing electric field strength Ep, which is a simulation result of the power supply substrate according to the basic example, the conventional example, and the first and second embodiments. As can be seen from FIG. 13, the electric field strength Ep in the first and second embodiments is reduced as compared with the conventional example.

  FIG. 14 is a photographic image showing electric field strength Ep, which is a simulation result of the power supply substrate according to the basic example, the conventional example, and the first and second embodiments. As apparent from FIG. 14, in the conventional example, the radiation electric field is concentrated in the vicinity of the electrode 11, but in Embodiments 1 and 2, it is dispersed and reduced without being concentrated in the vicinity of the electrode 11. Recognize.

  Therefore, according to the power supply substrate according to the present invention, it is possible to reduce conduction noise by avoiding an increase in the substrate area and reducing the parasitic capacitance as compared with the prior art. The power supply board according to the present invention can be applied to a power conversion device such as a power controller, an in-vehicle power supply, a general-purpose power supply, or a UPS (Uninterruptible Power Supply).

10, 10A ... dielectric substrate,
11, 12, 13 ... electrodes,
12C, 13C ... opening,
14 ... switching element,
14A ... heating element,
15 ... electrodes,
16 ... via conductor,
20 ... heat radiation part,
21 ... Thermal interface material (TIM),
22: Support member,
30 ... Upper housing sheet metal,
A ... Electrode part,
Cp: parasitic capacitance,
D1 ... diode,
L1 ... inductor,
SW1 is a switch element.

Claims (6)

A power supply substrate including a support on which a power supply circuit including a switching element is formed,
A first electrode formed on the first surface of the support, the potential of which varies with time according to the operation of the switching element;
A second electrode formed on the second surface of the support, the potential of which does not change with time by the operation of the switching element,
The power supply substrate, wherein the second electrode has an opening formed in at least a part of a portion facing the first electrode.   2. The power supply substrate according to claim 1, wherein the opening of the second electrode is formed in a portion facing the first electrode.   2. The power supply substrate according to claim 1, wherein the opening of the second electrode is further formed in a portion other than the portion facing the first electrode. The power supply board further includes
The power supply according to claim 1, further comprising a third electrode formed on the first surface of the support so as to surround the first electrode. substrate.   The power supply board according to claim 4, wherein the switching element is connected to the first electrode and the third electrode. The second electrode is formed on the inner layer of the support,
The power supply substrate according to claim 1, wherein the first electrode is connected to a fourth electrode through a via conductor formed in the support.

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