Power supply structure

A load board includes an electronic component and first wiring connected thereto. A power supply board includes a DC/DC converter and second wiring connected thereto. A bus block includes prismatic block-shaped conductors arranged with a gap interposed therebetween and fixed. The bus block is held between the first plate member and the second plate member such that the end faces of the block-shaped conductors are in contact with the load board and the power supply board. The bus block is connected to the first wiring and the second wiring such that current flows in a direction from the power supply board to the load board in one of two adjacent block-shaped conductors and that current flows in a direction from the load board to the power supply board in the other block-shaped conductor.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority of the prior Japanese Patent Application No. 2016-087264, filed on Apr. 25, 2016, the entire contents of which are incorporated herein by reference.

FIELD

The embodiments discussed herein are related to a power supply structure.

BACKGROUND

Conventionally, power supply to the central processing unit (CPU) and memory inside a server apparatus is implemented by supplying electric power generated from a power supply generation circuit in the same printed circuit board to electronic components including the CPU and memory using copper foil on the printed circuit board.

However, with demands for higher speed of CPUs and higher density, increase in current consumption and increase in power supply types are in demand. With the increase in power supply types, the number of power supply generation circuits is steadily increasing. Now that many power supply generation circuits are installed, installing power supply generation circuits and other electronic components on the same printed circuit board has reached a limit.

There is a power supply scheme that divides a board into a load board including electronic components serving as loads and a power supply board including power supply generation circuits for power supply and couples the load board and the power supply board to each other by bus bars.

Specifically, a bus bar for power feeding is brought into contact and fixed with a screw to a pad for supplying electric power generated by a direct current (DC)/DC converter disposed on the power supply board, and a bus bar for GND is brought into contact and fixed with a screw to a pad connecting to the ground (hereinafter abbreviated as GND). The bus bar for power feeding and the bus bar for GND are reinforced by fittings for preventing displacement and fixed to each other. The bus bar for power feeding and the bus bar for GND are brought into contact with the pads disposed on the load board and fixed with screws. Two clamps fixed to bus bars connecting to loads are inserted into the bus bar for power feeding and the bus bar for GND. The structure that couples the load board and the power supply board to each other with bus bars is thus completed. In this case, current flows from the bus bar for power feeding to the bus bar connecting to loads via the clamp to supply power to the load board. Current output from the loads then flows from the bus bar connecting to the loads to the bus bar for GND via the clamp and flows to the GND.

There is a conventional technique for supplying power from the power supply board to the load board, in which power is supplied through a power supply block disposed between a printed circuit board populated with semiconductor devices and a power supply bar extending from the back surface of the printed circuit board.

There is another conventional technique for keeping the space between boards by inserting a metal spacer between printed circuit boards and fixing the spacer with screws. In yet another conventional technique, a block with low-melting metal surrounded with an insulator is inserted between a semiconductor board and a mount board, and the boards are joined to each other by melting the low-melting metal. Conventional examples are described in Japanese Laid-open Patent Publication No. 63-152196, Japanese Laid-open Patent Publication No. 2001-156221, and Japanese Laid-open Patent Publication No. 2000-59000.

Unfortunately, when the power supply board is connected with the power feed board by bus bars, disposing the bus bars at the ends of the boards and fixing the C-shaped bus bars with screws increase the length of the power feed path and increase the resistance value of the power feeding conductor. It is therefore difficult to conduct appropriate power feeding due to a voltage drop and heat generation when large current is supplied.

Moreover, since the power feed path is long and the distance between the bus bar for power feeding and the bus bar for GND is wide, a large inductance component is produced on the power feed path. When the resistance and the inductance are large, the impedance of the power feed path is high. The amount of fluctuation of voltage supplied to the load increases in proportion to the amount of fluctuation of current and the impedance. Since the voltage fluctuation causes power supply noise, the greater impedance increases the noise at the load end. While the operating voltage of electronic components is decreasing year by year, the effect of power supply noise on the operation of electronic components is a serious problem, and reducing power supply noise is desired. A possible method for suppressing voltage fluctuation is to mount a large amount of capacitors. This method, however, increases the number of components and makes it difficult to reduce space and costs.

SUMMARY

According to an aspect of an embodiment, a power supply structure includes: a first plate member that includes a load, and has first wiring connected to the load; a second plate member that includes a power supply unit that supplies electric power to the load and has second wiring connected to the power supply unit; and a block member that has includes prism-shaped conductive members arranged with a gap interposed therebetween and fixed, is held between the first plate member and the second plate member such that end faces of the conductive members are in contact with the first plate member and the second plate member, is connected to each of the first wiring and the second wiring such that current flows in a direction from the second plate member to the first plate member in one of two adjacent conductive members of the conductive members and that current flows in a direction from the first plate member to the second plate member in the other of the two adjacent conductive members.

DESCRIPTION OF EMBODIMENTS

Preferred embodiments of the present invention will be explained with reference to the accompanying drawings. It is noted that the power supply structure disclosed in the present application is not limited by the following embodiments.

FIG. 1is a perspective view of the power supply structure according to an embodiment. A power supply structure3includes a load board1, a power supply board2, and bus blocks100A and100B.

The load board1is populated with electronic components10such as memory and the CPU, which are an example of the load.FIG. 1illustrates dual data rate (DDR) memory as an example of the electronic component10. The load board1is, for example, a motherboard.

The power supply board2contains a power supply unit such as a not-illustrated DC/DC converter. The power supply board2may additionally contain a heat sink and other components. The power supply unit outputs low-voltage and large-current power. The low voltage is, for example, 1.2 V. The large current is, for example, 120 A.

The bus blocks100A and100B are held between the load board1and the power supply board2. The bus blocks100A and100B are fixed to the load board1with screws101. The bus blocks100A and100B are fixed to the power supply board2with screws102. The bus blocks100A and100B are hereinafter simply referred to as “bus block100” unless otherwise specified.

The bus block100provides a conducting path for GND for sending current supplied from the power supply unit mounted on the power supply board2to the electronic components10on the load board1and passing current from the electronic components10to GND. AlthoughFIG. 1illustrates two bus blocks100called bus blocks100A and100B, the number of bus blocks100is preferably determined in accordance with the magnitude of supply current and the number of power source types. For example, when supply current is large, it is preferable that more bus blocks100are disposed. When there are a number of power source types, it is preferable that more bus blocks100are disposed.

FIG. 2is a perspective view of the bus block according to an embodiment. The bus block100includes block-shaped conductors111to122. The block-shaped conductors111to122are conductors having a quadratic prism shape formed of copper. All the block-shaped conductors111to122have the same structure.

In the present embodiment, the block-shaped conductors111to122are arranged in a row. In the bus block100, the block-shaped conductors111to122are put together so as to be each surrounded by an insulator130on the periphery. That is, the bus block100has a gap between each of the block-shaped conductors111to122, and the insulator130is disposed in the gap such that the block-shaped conductors111to122are not in contact with each other.

FIG. 3is a perspective view of the block-shaped conductor. Since all the block-shaped conductors111to122have the same structure, the structure of the block-shaped conductor111will be described here, by way of example.FIG. 3illustrates the block-shaped conductor111removed from the bus block100. The block-shaped conductor111has a quadratic prism shape, as illustrated inFIG. 3. The block-shaped conductor111has two faces113and114in contact with the load board1and the power supply board2. These faces113and114are an example of “one end face” and “the other end face”.

A screw hole115extends from the face113in the direction toward the face114. Although not illustrated inFIG. 3, a screw hole extends similarly from the face114in the direction toward the face113. The screw hole in the face114may be connected with the screw hole115or may be separate from the screw hole115. In the present embodiment, the screw hole in the face114is connected with the screw hole115, by way of illustration. That is, the screw hole115is present in both faces113and114.

Here, the block-shaped conductor111is shaped in a quadratic prism so that the adjacent face that is a surface facing the adjacent block-shaped conductor121is quadrangular. This shape increases the area facing the block-shaped conductor121.

FIG. 4is a diagram for explaining a connection state of the block-shaped conductors. As illustrated inFIG. 4, the block-shaped conductors111to122are sandwiched between the load board1and the power supply board2. The block-shaped conductors111to122each have one end face in contact with the load board1and the other end face in contact with the power supply board2. The power supply board2inFIG. 4is depicted so as to expose the surface on the side in contact with the screw102, for convenience of explanation.

In the state in which the bus block100is sandwiched between the power supply board2and the load board1, power supply pads21connecting to the wiring (wiring pattern) between the power supply board2and the load board1are disposed on the surface of the power supply board2on the side in contact with the block-shaped conductors111to122. This power supply pad21is an example of “electrode”.

The power supply pad21disposed on the power supply board2is a member for ensuring connection between the block-shaped conductors111to122and the wiring laid on the power supply board2. The power supply pads21disposed on the power supply board2are in contact with the respective faces114of the block-shaped conductors111to122. The power supply pads21in contact with the block-shaped conductors111and112connect to the power supply. The power supply pads21in contact with the block-shaped conductors121and122connect to GND. The wiring on the power supply board2for connecting the power supply and the ground to the power supply pad21is an example of the “second wiring”.

In a state in which the bus block100is sandwiched between the power supply board2and the load board1, power supply pads connecting to the wiring (wiring pattern) between the power supply board2and the load board1are arranged also on the surface of the load board1on the side in contact with the block-shaped conductors111to122, in the same manner as in the power supply board2. The power supply pads on the load board1are in contact with the respective faces113of the block-shaped conductors111to122. The power supply pads on the load board1in contact with the block-shaped conductor111and112connect to the power supply terminals of the electronic components mounted on the load board1. The power supply terminals include an “input terminal”, which is a terminal for supplying electricity to the electronic component, and an “output terminal”, which is a terminal outputting electricity from the electronic component. The power supply pads on the load board1in contact with the block-shaped conductors121and122are connected to the GND terminals of the electronic components mounted on the load board1. The wiring on the load board1for connecting the electronic component with the power supply pad is an example of “first wiring”.

That is, the block-shaped conductors111and112are power supply components for the electronic components on the load board1, and the block-shaped conductors121and122serve as GND paths connecting to GND for the electronic components on the load board1. In the following, for easy understanding of the respective roles of the block-shaped conductors111to122, the block-shaped conductors111and112serving as power supply components may be referred to as “power feed blocks111and112”. The block-shaped conductors121and122serving as GND paths may be referred to as “GND blocks121and122”.

The power feed blocks111and112and the GND blocks121and122are disposed between the load board1and the power supply board2so as to be alternately arranged. That is, in the bus block100according to the present embodiment, the power feed block111and the power feed block112as well as the GND block121and the GND block122are disposed so as not to be continuously arranged. Also between the bus block100A and the bus block100B, the power feed blocks111and112and the GND blocks121and122are disposed so as to be alternately arranged. That is, when the bus block100A and the bus block100B are disposed such that the block-shaped conductors111to122are arranged in a row, the GND block122of the bus block100A is arranged adjacent to the power feed block111of the bus block100B.

This arrangement state can be translated into a connection relation as described below. That is, the power feed blocks111and112connected such that current flows from the power supply board2to the load board1and the GND blocks connected such that current flows from the load board1to the power supply board2are alternately arranged.

The power feed blocks111and112as well as the GND blocks121and122have the screws101inserted from the respective screw holes115from the load board1to be fixed to the load board1. The power feed blocks111and112as well as the GND blocks121and122have the screws102inserted in the respective screw holes115from the power supply board2and fixed to the power supply board2.

FIG. 5is a schematic cross-sectional view for explaining the power supply path.FIG. 5illustrates the power feed block111and the GND block121fixed to the load board1and the power supply board2.

A power feed layer12and a GND layer13are disposed in the load board1. In addition, the electronic component10is mounted on the load board1. A power feed layer22and a GND layer23are disposed in the power supply board2. In addition, a DC/DC converter20is mounted on the power supply board2.

A power supply pad11A is disposed between the screw101and the load board1, and a power supply pad11B is disposed between the load board1and the power feed block111and between the load board1and the GND block121. A power supply pad21A is disposed between the screw102and the power supply board2, and a power supply pad21B is disposed between the power supply board2and the power feed block111and between the power supply board2and the GND block121. The power supply pads11A,11B,12A, and21B are formed of a corrosion-resistant and conductive material such as copper and gold plating.

The power supply pads11B and21B are disposed in order to increase the contact area of power supply vias14and24and GND vias15and25described later with the power feed block111and the GND block121. If the GND vias15and25are directly in contact with the power feed block111and the GND block121, the contact area is small and the contact resistance is high, possibly causing a voltage drop or heat generation at the contact point. By contrast, arranging the power pads11B and21B can increase the contact area and reduce the contact resistance.

The DC/DC converter20mounted on the power supply board2is connected to power supply pads241and242. The power supply pad241is connected to the GND layer23through the GND via25. The power supply pad242is connected to the power feed layer22through the power supply via24. The power feed layer22is connected to the power feed block111through the power supply via24with the power supply pad21B interposed therebetween. The GND layer23is connected to the GND block121through the GND via25with the power supply pad21B interposed therebetween.

The electronic component10mounted on the load board1is connected to power supply pads141and142. The power supply pad141is connected to the GND layer13through the GND via15. The power supply pad142is connected to the power feed layer12through the power supply via14. The power feed layer12is connected to the power feed block111through the power supply via14with the power supply pad11B interposed therebetween. The GND layer13is connected to the GND block121through the GND via15with the power supply pad11B interposed therebetween.

Electricity generated by the DC/DC converter20is fed to the electronic component through the power supply path. The power supply path is constructed with a power feed path from the DC/DC converter20to the electronic component10and a conducting path from the electronic component10to GND.

In the present embodiment, the power supply pad242, the power supply via24, the power feed layer22, the power supply via24, the power supply pad21B, the power feed block111, the power supply pad11B, the power supply via14of the load board1, and the power feed layer12are disposed on the power feed path. In the present embodiment, the power supply pad141, the GND via15, the GND layer13, the GND via15, the power supply pad11B, the GND block121, the power supply pad21B, the GND via25of the power supply board2, the GND layer23, the GND via25, the power supply pad241, and the DC/DC converter20are disposed on the conducting path.

Current output from the DC/DC converter20then passes through the power supply pad242and the power supply via24and flows into the power feed layer22. Current flowing to the power feed layer22passes through the power supply via24and the power supply pad21B and flows into the power feed block111. Current flowing to the power feed block111passes through the power supply pad11B and the power supply via14of the load board1and flows into the power feed layer12. Current flowing to the power feed layer12passes through the power supply via14and the power supply pad142and flows into the electronic component10.

Subsequently, current output from the electronic component10passes through the power supply pad141and the GND via15and flows into the GND layer13. Current flowing into the GND layer13passes through the GND via14and the power supply pad11B and flows into the GND block121. Current flowing into the GND block121passes through the power supply pad21B and the GND via25of the power supply board2and flows into the GND layer23. Current flowing into the GND layer23passes through the GND via25and the power supply pad241and flows into the DC/DC converter20and finally to GND.

In this way, power supply is supplied to the electronic components10via the power feed blocks111and112and is released to GND via the GND blocks121and122. That is, low-voltage and large-current power supply output from the DC/DC converter20is supplied to the electronic components10using the power feed blocks111and112as well as the GND blocks121and122.

Here, the direction in which current flows in the power feed blocks111and112is opposite from that in the GND blocks121and122. The power feed blocks111and112and the GND blocks121and122through which current flows in opposite directions are arranged alternately to cancel out a magnetic field produced by current. This arrangement can reduce the inductance component produced by the power feed path, namely, the power feed blocks111and112as well as the GND blocks121and122.

Here, the relation of the impedance of the power feed path with the resistance and the inductance of the power feed path is represented by Equation (1) below:
Z=R+j⋅L(1)

where Z is the impedance of the power feed path, R is the resistance of the power feed path, and L is the inductance of the power feed path. That is, the greater the resistance and the inductance of the power feed path are, the greater the impedance of the power feed path is.

The relation of the impedance of the power feed path with the amount of fluctuation of voltage and the amount of fluctuation of current supplied to the electronic component10is represented by Equation (2) below:
ΔV=ΔI*Z(2)

where ΔV is the amount of fluctuation of voltage supplied to the electronic component10, and ΔI is the amount of fluctuation of current supplied to the electronic component10. That is, the amount of voltage fluctuation increases in proportion to the amount of current fluctuation and the impedance of the power feed path. The voltage fluctuation causes power supply noise. In order to suppress power supply noise, it is preferable to suppress voltage fluctuation.

Based on this, suppressing the inductance of the power feed path can alleviate power supply noise. As in the present embodiment, the power feed blocks111and112and the GND blocks121and122through which current flows in opposite directions are arranged alternately to suppress the inductance of the power feed path and alleviate power supply noise.

The power feed blocks111and112as well as the GND blocks121and122have a quadratic prism shape. Because of this shape, the adjacent faces of the power feed blocks111and112as well as the GND blocks121and122are in such a state that quadrangular surfaces are opposed to each other.

The inductance of parallel flat plates301and302depicted inFIG. 6will now be described.FIG. 6is a diagram for explaining the inductance of parallel flat plates. The parallel flat plates301and302depict part of two flat plates opposed to each other with infinite extent. The parallel flat plates301and302depicted inFIG. 6have a conductor width L1and a conductor length L2. The distance between the parallel flat plates301and302is a distance L3. In the parallel flat plates301and302, current flows in the opposite directions in the direction in which the conductor length L2extends inFIG. 6. That is, current flows in the directions of arrows Q1and Q2. In this case, the inductance of the parallel flat plates301and302is represented by Equation (3) below:
L=μ*L3*L2/L1  (3)

where μ is the permeability of the insulator130, and L1, L2, and L3are the lengths depicted inFIG. 6. As illustrated by Equation (3), the longer the conductor width L1is, the smaller the inductance is, and the shorter the conductor length L2is, the smaller the inductance is. The shorter the distance L3is, the smaller the inductance L is.

Referring now toFIG. 7, the inductance of the quadratic prism-shaped power feed block111and GND block121will be described.FIG. 7is a diagram for explaining the effect of the shape of the adjacent face on the inductance. As illustrated inFIG. 7, the distance d is, for example, the distance between the respective opposing faces of the power feed block111and the GND block121. The height h is the length of the side in the direction in which electricity flows in the respective opposing faces of the power feed block111and the GND block121held between the load board1and the power supply board2. The width w is the side orthogonal to the height h of the respective opposing faces of the power feed block111and the GND block121.

We will now examine the minute surface closer to the center in the respective opposing faces of the power feed block111and the GND block121inFIG. 7. This minute surface can be considered as a state almost identical to the state of the parallel flat plates301and302inFIG. 6, and the inductance can be considered to approximate to the inductance in the parallel flat plates301and302. That is, the width w can be considered as the conductor width L1, the height h can be considered as the conductor length L2, and the distance d can be considered as the distance L3. In this case, the inductance produced in the power feed block111and the GND block121can be approximated by Equation (3).

That is, the shorter the distance d is, the smaller the inductance L is. Here, in the bus block100according to the present embodiment, the insulator130is sandwiched between the power feed block111and the GND block121and can prevent short-circuiting due to displacement when the power feed block111and the GND block121are arranged close to each other. In the bus block100according to the present embodiment, therefore, the distance between the power feed block111and the GND block121can be reduced. This reduction in distance can reduce the inductance and alleviate power supply noise.

The shorter the height h is, the smaller the inductance is, and the longer the width w is, the smaller the inductance is. Here, it is preferable to minimize the length in the longitudinal direction in order to reduce the electricity transmission distance in the power feed block111and the GND block121. It can be said that when the height h is determined to be the shortest distance, the inductance decreases as the area of the respective opposing faces of the power feed block111and the GND block121increases, that is, as the adjacent area of the power feed block111and the GND block121increases. Here, the power feed block111and the GND block121are shaped in a quadratic prism and have a larger adjacent area, compared with, for example, a cylinder. The power feed block111and the GND block121shaped in a quadratic prism therefore can suppress inductance and alleviate power supply noise.

Referring now toFIGS. 8 to 12, the inductance in the case where the power supply structure3according to the present embodiment is used will be described in comparison with the inductance in the case of another configuration.FIG. 8is a diagram for explaining a configuration in which the quadratic prism-shaped GND block and power feed block are alternately arranged.FIG. 9is a diagram for explaining the case where the quadratic prism-shaped GND blocks are arranged side by side and the quadratic prism-shaped power feed blocks are arranged side by side.FIG. 10is a diagram for explaining the comparison of inductance between the side-by-side arrangement of the quadratic prism-shaped GND blocks and the quadratic prism-shaped power feed blocks and the alternate arrangement of the GND blocks and the power feed blocks.FIG. 10illustrates the result of simulation using the configurations inFIG. 8andFIG. 9.

FIG. 11is a diagram for explaining the configuration in which the cylinder-shaped GND blocks and power feed blocks are alternately arranged.FIG. 12is a diagram for explaining the comparison of inductance between the use of quadratic prism-shaped blocks and the use of cylinder-shaped blocks.FIG. 12illustrates the result of simulation using the configurations inFIG. 8andFIG. 11. In the example described here, the voltage is 1.2 V, and the current is 135 A. It is assumed that the temperature increase is 20° C. when power supply is conducted.

InFIG. 10, the vertical axis represents the magnitude of inductance. The horizontal axis represents frequency. The line201represents the inductance corresponding to the frequency in the case of the configuration inFIG. 8. The line202represents the inductance corresponding to the frequency in the case of the configuration inFIG. 9.

That is, when the inductance is as represented by the line201, the configuration is as follows. As illustrated inFIG. 8, the power feed blocks111and112as well as the GND blocks121and122each have a quadratic prism shape with a height L12of 7 mm and a conductor diameter of 8 mm. The power supply pad21B of the power supply board2is disposed so as to correspond to each of the power feed blocks111and112as well as the GND blocks121and122. The similar power supply pads are disposed also on the load board1. The power feed blocks111and112and the GND blocks121and122are fixed to the load board1with the screws101and fixed to the power supply board2with the screws102. The power feed blocks111and112as well as the GND blocks121and122have a distance L11of 12 mm between the center axes, in the same manner. In other words, the power feed blocks111and112as well as the GND blocks121and122have a distance between conductors of 4 mm.FIG. 8illustrates an example of the configuration described in the embodiment.

When the inductance is as illustrated by the line202, the configuration is as follows. As illustrated inFIG. 9, a power feed block31has a quadratic prism shape with a height L22of 7 mm and a conductor diameter of 8 mm. A power feed block32as well as GND blocks33and34each have a quadratic prism shape similar to the power feed block31. The power feed block31and the power feed block32are disposed so as to be adjacent to each other. The GND block33and the GND block34are disposed so as to be adjacent to each other. A power supply pad35of the power supply board2is singly disposed so as to be in contact with both of the power feed blocks31and32, and another power supply pad35is singly disposed so as to be in contact with both of the GND blocks33and34. In this case, since the power feed paths are adjacent to each other and the GND paths are adjacent to each other, a single power supply pad35is provided for the adjacent paths. Similar power supply pads are disposed also on the load board1. The power feed blocks31and32as well as the GND blocks33and34are then fixed to the load board1with the screws101and fixed to the power supply board2with the screws102. The power feed blocks31and32as well as the GND blocks33and34are disposed such that the distance L21between the center axes is 12 mm. In other words, the power feed blocks111and112as well as the GND blocks121and122have a distance between conductors of 4 mm. That is, the configuration inFIG. 8and the configuration inFIG. 9differ in that the power feed blocks31and32are adjacent and the GND blocks33and34are adjacent, or power feed blocks41and42and GND blocks43and44are alternately arranged.

As illustrated inFIG. 10, the inductance of the configuration inFIG. 8as represented by the line201is smaller than the inductance of the configuration inFIG. 9as represented by the line202. That is, when the power feed blocks41and42and the GND blocks43and44are alternately arranged, the production of a magnetic field is suppressed and the inductance is smaller, compared with when the power feed blocks31and32are adjacent and the GND blocks33and34are adjacent. Specifically, when currents flow next to each other in the same direction, the magnetic field is cancelled between the power feed blocks31and32as well as the GND blocks33and34but is increased on the periphery, and therefore the magnetic field as a whole is increased. By contrast, when adjacent currents flow in opposite directions, the magnetic field is increased between the power feed blocks41and42as well as the GND blocks43and44but is cancelled on the periphery, and therefore the magnetic field as a whole is reduced. In particular, the power supply structure3according to the present embodiment can suppress an increase in magnetic field since the gap between the power feed blocks111and112and the GND blocks121and122is minimized.

The inductance with a different shape of the power feed blocks41and42as well as the GND blocks43and44will now be described. Here, the description will be given by comparing the configuration inFIG. 8with the configuration inFIG. 11.

In the configuration inFIG. 11, a power feed block41has a cylindrical shape with a height L32of 7 mm and a conductor diameter of 8 mm. A power feed block42as well as the GND blocks43and44each have a cylindrical shape similar to the power feed block41. A power supply pad45on the power supply board2is disposed to correspond to each of the power feed blocks41and42as well as the GND blocks43and44. Similar power supply pads are disposed also on the load board1. The power feed blocks41and42as well as the GND blocks43and44are fixed to the load board1with the screws101and fixed to the power supply board2with the screws102. The power feed blocks41and42as well as the GND blocks43and44are disposed such that a distance L31between the center axes is 12 mm, in the same manner as inFIG. 7. In other words, the power feed blocks111and112as well as the GND blocks121and122have a distance between conductors of 4 mm. That is, the configuration inFIG. 8and the configuration inFIG. 11differ in shape of the power feed blocks111and112as well as the GND blocks121and122, namely, a quadratic prism or a cylinder.

As illustrated inFIG. 12, the inductance of the configuration inFIG. 8as illustrated by the line201, that is, the inductance of the configuration as an example of the present embodiment is smaller than the inductance of the configuration ofFIG. 11as illustrated by the line203. That is, when the quadratic prism-shaped power feed blocks111and112and GND blocks121and122are used, the inductance is smaller than when the cylindrical power feed blocks41and42and GND blocks43and44are used. That is, the quadratic prism shape of the power feed blocks111and112as well as the GND blocks121and122can increase the adjacent area and thereby can reduce inductance. In this way, the result of simulation with the adjacent area changed also suggests that the larger adjacent area reduces the inductance. That is, the inductance in the case of the power feed blocks111and112as well as the GND blocks121and122can be approximated by Equation (3) representing the inductance of the parallel flat plates301and302.

In this way, in the power supply structure3according to the present embodiment, the quadratic prism-shaped power feed blocks111and112and GND blocks121and122are alternately arranged to further reduce inductance and reduce power supply noise.

As described above, in the power supply structure according to the present embodiment, the bus block fixed in a state in which the power feed blocks and the GND blocks are arranged in a row is used for power supply from the power supply board to the load board. In this arrangement, the power feed block and the GND block are not adjacent, so that the directions of currents flowing through the adjacent paths are opposite. Thus, the magnetic fields produced by current can be cancelled out to reduce inductance and reduce power supply noise.

When the power feed block and the GND block shaped in a quadratic prism are compared with those shaped in a cylinder with the same power feeding distance, the quadratic prism shape can increase the adjacent area and can reduce inductance to reduce power supply noise. Even when large current is supplied, the quadratic prism shape can increase contact resistance, compared with a cylindrical shape, and thus can reduce the effects of voltage drop and heat generation. The prism shape is not limited to the quadratic prism as illustrated in the drawings and may be modified as appropriate as long as the prism shape can increase the adjacent area.

In addition, the integrated structure including the power feed blocks and the GND blocks put together with an insulator can avoid short-circuiting between adjacent blocks due to displacement.

When a bus bar is used as in a conventional example, the bus bar may be disposed at an end portion of the board, and this arrangement increases the length of the power supply path to the electronic component. When the bus bar is arranged inside the board, it is difficult to populate the board densely with electronic components, because a large area is allocated for fixing the bar with screws. By contrast, when the bus block according to the present embodiment is used, the block can be arranged in a narrow space inside the board, because the block is fixed on the top and the bottom with screws. This arrangement enables power supply through a shorter power supply path to the densely populated electronic components, thereby reducing heat generation in power supply to the densely populated electronic components, and reducing a voltage drop.

Here, the power source types for the power feed block111and the power feed block112may be the same or may be different.FIG. 13is a diagram for explaining a power supply destination of the bus block according to the embodiment. InFIG. 13, V1, V2, and V3denote different voltages. InFIG. 13, G denotes the GND block. For example, as in a bus block151inFIG. 13, the power feed blocks111and112may supply the same voltage V1. Alternatively, as in a bus block152, the power source types may be different in such a manner that the voltage supplied by the power feed block111is V2and the voltage supplied by the power feed block112is V3. Thus, the electronic component10, which is a power supply destination of the power feed block111and the power feed block112, may be the same component or may be different components.

Modification

In the present embodiment, the power feed blocks and the GND blocks are alternately arranged in series. However, they are not necessarily arranged in series because the magnetic field can be cancelled out if the power feed blocks and the GND blocks are alternately arranged.

FIG. 14is a diagram illustrating another arrangement example of the power feed blocks and the GND blocks. InFIG. 13, V denotes a power feed block, and G denotes a GND block.

For example, as in an arrangement160, a power feed block and a GND block may be arranged side by side. Also in this case, the magnetic fields produced by current are cancelled out, thereby reducing inductance and reducing power supply noise.

Alternatively, for example, as in an arrangement170, the power feed blocks and the GND blocks may be arranged in a checkerboard pattern. Also in this case, the magnetic fields produced by current are cancelled out, thereby reducing inductance and reducing power supply noise.

The block may be formed in any shape other than a quadratic prism that can increase the adjacent area. The adjacent area can be increased if the adjacent face is quadrangular. For example, as in an arrangement180, blocks each shaped in a sector prism having a quadrangular side surface may be arranged into a ring. Also in this case, the magnetic fields produced by current are cancelled out thereby reducing inductance, and in addition, the larger adjacent area can reduce inductance and reduce power supply noise.

Alternatively, for example, as in an arrangement190, a GND block may be arranged at the center of the arrangement180. Also in this case, the magnetic fields produced by current are cancelled out, thereby reducing inductance and reducing power supply noise.

As long as the directions in which current flows are opposite between the adjacent block-shaped conductors, a power feed block and a GND block used for the same power source may be adjacent to each other, or a power feed block and a GND block used for different power sources may be adjacent to each other.

As described above, the configuration may be in a different arrangement as long as power feed blocks and GND blocks are alternately arranged. Also in such a case, inductance can be suppressed, and power supply noise can be reduced. Even when the block is not shaped in a quadratic prism, the adjacent face shaped in a quadrangle can reduce inductance and can reduce power supply noise.

An aspect of the power supply structure disclosed in the present application achieves the effect of reducing power supply noise at a time of large current supply to a board densely populated with electronic components.