Connection system for fast power supplies

In a low voltage, high current power supply having very fast transitions of the load current, as in certain power supplies for microprocessors, the circuit impedances, particularly the stray inductance of the connector, are a major problem. If the voltage regulator circuits are separated from the output capacitor and brought to separate contacts in the connector, only connecting together on the load side, the voltage regulator will be much better able to overcome the connector impedance. The connector may be a printed connector, in which the metal surfaces of the internal layers of a multilayer printed circuit card are extended successively and mate with a similar complementary printed connector. To overcome high frequency effects, the power bus is a multilayer interleaved bus. Vias conduct the high frequency component of the current much more effectively at the edge of a stack of foil layers, so the power bus is strongly digitated to increase the periphery.

BACKGROUND OF THE INVENTION

In a fast power supply that must provide low voltage, high current power with very fast current transitions and tight regulation, the inductance of the connection system is a serious problem. To drive fast transitions of current through the inductance of the connector requires a significant voltage across the connector, but that is incompatible with holding tight voltage regulation.

Often a fairly large capacitor is used on the output of the power supply. One function of this capacitor is to reduce the ripple voltage. Another is to provide a low impedance source for dynamic changes in the output current. However, the large output capacitor also suppresses the voltage that might drive fast current transitions through the connection system.

SUMMARY OF THE INVENTION

This invention teaches that the output capacitor of a fast power supply can be separated from the fast power supply but can be connected to it and the load through separate pins of the connector. The outputs of power supplies often have characteristics of controlled current sources, so there is ample voltage to drive the current through the connector to the load. The output capacitor can be placed on the power supply board, but it is connected to the load through separate pins so that it does not attenuate the driving voltage for the current transition.

This invention teaches that an interleaved multilayer circuit board can provide a very low impedance connection system for a fast power supply. Several layers of the multi-layer board are arranged in pairs having counter-flowing currents, to minimize the inductance.

This invention teaches using a number of layers of the multilayer board for current conduction because at very high frequencies, the penetration depth into the conductor of the very high frequency current is very small. It is taught to use multiple layers of wide conductors to that the total cross-sectional area available for conduction of the very high frequency current is sufficient.

This invention teaches that the multiple layers of wide conductors may extend to the edge of a circuit board, some extending further than others and all having an exposed area of uninsulated metal for connection with complementary exposed areas of uninsulated metal of a mating circuit board to comprise a connector.

This invention also teaches that pairs of conductors with counter-flowing current are preferably closely spaced with a dielectric film between them. It is preferred to use adjacent extended exposed uninsulated metal areas to connect pairs of conductors with their continuation on a second circuit board so that the spacing through the dielectric layer is consistent across the connector, to minimize impedance discontinuities at the connector.

This invention teaches that conventional vias are not adequate to carry very high frequency currents to buried layers of a multilayer circuit board. To be effective, the vias have to be at the edge of a stack of conductors. Accordingly, it is taught to interdigitate the conductors and to locate the vias on the edges of the interdigitated conductors.

This invention also teaches that alternate interdigitated conductors may connect to the output of the fast power supply and to the output capacitor and that the interdigitated conductors may extend to a connector, separately, and that they may be connected at the load side of the connector.

This invention also teaches that the interdigitated conductors may taper toward their ends so that the is not an abrupt ending of the conductor from which reflections could be reflected back, perhaps causing standing waves in the power bus.

DETAILED DESCRIPTION

FIG. 1shows a power supply system1comprising a power supply3connected through a connector13to an output load5shown as a microprocessor. There will likely be one or more decoupling capacitors11near the load. The power supply3comprises a power converter7shown as a voltage regulator as an illustration, not a limitation, and an output capacitor9. The voltage regulator7may be a buck regulator, as an example.

In this specification and the claims, a “power supply” is an assembly for providing power to a load. It is usually, but not necessarily, connected to the load through two or more contacts of a connector so that the power supply is a separate assembly and can be separated from the load by unplugging the connector. A power supply usually comprises a “power converter” and an “output capacitor”. In this specification and the claims, a “power converter” is a source of current, and may be either a voltage regulator or a controlled current source. Recitation of a “power converter” includes a voltage regulator, a controlled current source, or any other source of current that can be controlled to regulate voltage or current or both. The power converter will have at least two electrical output terminations, at least one positive output termination and at least one negative output termination.

In this specification and the claims, an “output capacitor” is a relatively large capacitor usually (but not necessarily) located near the power converter in the power supply, for smoothing the output ripple and storing energy. The output capacitor will have two or more electrical terminations, at least one positive output capacitor termination and at least one negative output capacitor termination. Because this invention relates to the way in which the power converter and the output capacitor are connected to each other and the load, they are defined separately. While a power converter may contain some capacitors for filtering, transient suppression, control or whatever, these capacitors are generally smaller than the output capacitor, and one skilled in the art of power supplies would distinguish between them readily in view of this definition and explanation.

In this specification and the claims, a “load” is a user of electrical power, in particular, a user of electrical power from the power supply. The load is usually, though not necessarily, connected to the power supply through a connector. The load will have at least two terminations, at least one positive load termination and at least one negative load termination. In some applications the load may momentarily be a source of electrical power and the power supply may sink the electrical power from the load.

In this specification and the claims, a “connection system” comprises a first connector and a second connector, the first and second connectors each having a plurality of electrical contacts which are complementary, that is, they will mate one to the other to comprise a plurality of electrical connections through the connection system. As an example, a first connector may be on a power supply and a second connector may be on a load. When the first connector is connected to the second connector, power may flow from the power supply to the load. In this detailed description, a connection system may be called a “connector”, and it is understood from the syntax that the connector comprises complementary mating first and second connectors.

FIG. 2shows an equivalent circuit21of the power supply system1ofFIG. 1. A power supply23comprises a controlled current source27and an output capacitor29. A stray inductance47is also shown. The power supply23is connected to a load25through a connector39. The load25is shown as two resistors31and33, and a switch35may switch the resistor33in and out of the circuit. The load of the resistor31represents the minimum load for the power supply23, and the parallel combination of the resistors31and33represent the maximum load. A practical power supply will likely accommodate any load between the minimum load and the maximum load, but this schematic shows the maximum possible step change of output current for normal operating conditions. The output load may have one or more decoupling capacitors37. Stray inductances43and45of the load are shown, as is the stray inductance41of the connector39. Although not shown, it is understood that there will be one or more sets of contacts in the connector39for the ground return as well.

Some power supply loads have very fast load current transitions, a microprocessor being an example. A microprocessor is capable of going from an idle current to full load in a few machine cycles, and back to idle current just as fast. Present power supplies cannot change current that quickly, so the microprocessor has the constraint of having to limit the rate of change of its input current. A representative microprocessor may have a voltage in the order of one volt and a full load current in excess of 100 amperes. A representative idle current may be in the order of 30 percent, or 30 amperes. The rate of load change may be constrained to one hundred amperes per microsecond, though it would be desirable to permit much faster transitions in current.

Many power supplies have characteristics of a controlled current source, because their regulating source is an inductor with a pulse width modulated (pwm) source voltage. One of the limitations of such a power supply is the rate at which the current can be increased in the output inductor. A new generation of power supply may avoid that limitation, but even with an ideal power supply, the problem of the output capacitor and the stray inductances makes it difficult or impossible to maintain output voltage regulation at the load with fast changes in the load current. Of particular concern is the stray inductance41of the connector39.

The problem of the stray inductance41of the connector39is exacerbated by the attenuating effect of the output capacitor29. Even if the controlled current source27is capable of a step change of current from minimum to maximum load, the current first must flow into the output capacitor29. As the voltage in the output capacitor29cannot change instantly, the voltage of the capacitor ramps up slowly. Meanwhile, the increased load current is dropping the voltage of the decoupling capacitor37, causing a negative spike in the output voltage. The current can only increase through the stray inductances47,41and43when there is sufficient voltage difference between the output capacitor29and the decoupling capacitor37to over come the stray inductances47,41and43.

FIG. 3shows a power supply system61that overcomes many of these problems. As inFIG. 2, a power supply63provides an output current to a load65through a connector79. The load is shown as two resistors71and73with a switch75. The power supply63comprises a controlled current source67and an output capacitor69, and the load65may have one or more decoupling capacitors77. Stray inductances81,83,89and91are also shown inFIG. 3. Note, however, that the output capacitor69is connected to the power supply system61through separate pins in the connector79. Although not shown, it is understood that there will be one or more sets of contacts for the ground return as well.

If the voltage regulation of the power supply63has the characteristics of a controlled current source67, then there will be a sufficient driving voltage at its output to drive a fast transition of current through the connector79, even with its stray inductance81. The attenuating effect of the output capacitor69is not a factor in this conduction path, as the output capacitor69is connected to the power supply system61through separate pins of the connector79.

Ideally, the output current of the power supply63equals the current of the load65, so ideally no current would flow into or out of the output capacitor69. Practically, there is some lag in the control of the power supply63, so some current flows out of the output capacitor69when the load is increased and the charge that is removed from the output capacitor69by this initial current must then be restored.

FIGS. 4athrough4fshow a representative power supply interconnection system100of this invention wherein a power supply circuit101provides power to a load circuit115, which may be a microprocessor (not shown), as an example, not a limitation. On the load circuit115, power is provided from the power supply101through a connector117. The connector117is shown as a standard printed circuit edge connector having a power connection119on the top of the load circuit115printed wiring board and having a return connection121on the bottom of the printed wiring board.

The power supply circuit101has a connector103which mates with the connector117of the load circuit115. When the connectors103and117are mated, a plurality of power connection contacts123—123,125—125make electrical contact with the power connection119on the top of the load circuit115printed wiring board. On the bottom, a return connection area113makes contact with the return connection121of the load circuit115. There may also be some extra connector contacts111for ancillary use, such as for monitoring and control.

Of the plurality of power connection contacts123—123,125—125, alternate contacts can be seen to be designated “I” (123—123) or “C” (125—125), and it should be understood that the contacts designated “I” (123—123) are connected to the voltage regulation circuit (not shown) of the power supply circuit101, whereas the contacts designated “C” (125—125) are connected to an output capacitor (not shown), and the output capacitor is connected to the voltage regulation circuit only when the power supply101is connected to the load circuit115, and that connection is through different contacts in the connector.

FIGS. 4a,4cand4eshow the connector103of the power supply circuit101as being plated on the inside surfaces of extended outer layers105and107of the printed wiring board on which the power supply circuit101is assembled. This construction is preferred as it has a lower leakage inductance than the prior art molded printed circuit connectors, however the teaching of this invention to use different contacts for the voltage regulator and the output capacitor is equally applicable to prior art molded printed circuit connectors. To provide proper spacing so that the connector117of the load circuit115is a slip fit into the connector103of the power supply circuit101, a spacer laminate109is sandwiched between the top layer105and the bottom layer107of the power supply circuit101. The spacer laminate109may comprise internal layers of a multilayer printed circuit board. The connectors103and117are preferably clamped tightly together with a clamp (not shown) to ensure a good electrical connection.

FIG. 5shows a prior art power supply system151comprising a multiphase buck converter153connected to a load155through a connector173. The multiphase buck converter153comprises four supply switches159a–159d, four return switches161a–161dand four inductors157a–157dconnected to an output capacitor163. The load155comprises two resistors165and167, one of which167has a switch169so that the load155may be maximum or minimum. Usually a power supply load could be any value between the maximum and the minimum load, but this arrangement is shows as an illustration only to represent the maximum possible load current transient condition. The output load155may have one or more decoupling capacitors171. Stray inductances177,175,179and181are also shown. As inFIG. 2, the output capacitor163attenuates the output voltage resulting from a current change in the inductors157a–157dso that there is very little driving voltage to drive a change in current through the stray inductances177,175,179and181, particularly the stray inductance175of the connector173. Although not shown, it is understood that there will be one or more sets of contacts for the ground return as well.

FIG. 6shows a power supply system201of this invention. A multiphase buck converter203is connected to a load205through a connector223a–223b. Leakage inductances215a,215b,217,219and215are shown. The multiphase buck converter203comprises four supply switches209a–209dand four return switches211a–211ddriving four inductors207a–207d. The load205comprises two resistors221and217, and a switch219can switch the resistor217. Usually a power supply load could be any value between the maximum and the minimum load, but this arrangement is shows as an illustration only to represent the maximum possible load current transient condition. The load205may have one or more decoupling capacitors211.

In contrast to the power supply system151ofFIG. 5, the output of the four inductors207a–207dand an output capacitor213are connected to the load205through separate contacts of the connector,223aand223brespectively. The outputs of the four inductors207a–207dwill have sufficient drive potential to overcome the inductance215aof the connector contact223a, as the drive potential will not be attenuated by the output capacitor213. Although not shown, it is understood that there will be one or more sets of contacts for the ground return as well.

FIG. 7shows a power supply system230of this invention. A switched current power converter231is connected through a connector234to a load240. The switched current power converter231comprises an indefinite integer n of inductors235a–235n. N supply side switches236a–236nandnreturn switches237a–237nare operated by a controller circuit (not shown) such that the currents in the n inductors235a–235nare regulated in a “constant current” mode. The current from the n inductors235a–235nis directed to the load240when any of the n load side switches238a–238nis closed to the load240, and it is directed to the return when any of the n load side switches238a–238nis closed to the return.

The load240is shown as two resistors241and242, and a switch243can switch the resistor242in and out of the load240. Usually a power supply load could be any value between the maximum and the minimum load, but this arrangement is shows as an illustration only to represent the maximum possible load current transient condition. The load240may have one or more decoupling capacitors245.

The connector234comprises an indefinite integer m of pairs of contacts232a–232mand233a–233mon the “high side”, and m pairs of contacts239a–239mand247a–247mon the “return side”. The high side of the switched current power converter231is connected to the load240through the m contacts232a–232m, and its return is connected through the m contacts239a–239m. The high side of an output capacitor244is connected to the load240through the m contacts233a–233m, and its return is through the m contacts247a–247m. Although the number of contacts in each group is shown as being equal to the indefinite integer m, as an illustration, this is the preferred arrangement and not a limitation, as it is not necessary for them to be equal. Also, there will very likely be additional contacts in the connector234for monitoring, control and so forth.

The contacts232a–232m,233a–233m,239a–239mand247a–247mare all shown with representative leakage inductance, representing that the leakage inductances of the contacts of the connector234are a serious problem in a power supply system in which there are very fast transitions of current. Note in particular that all of the high side contacts are brought to a common connection on the load side of the connector234, as are all of the returns, but connections to the power converter231and the connections to the output capacitor244are separated on the power supply side of the connector234.

Because the n load side switches238a–238ncan switch nearly instantaneously, there can be extremely fast transitions in the current to the load240. The currents in the inductors235a–235nwill have the characteristics of current sources, and will have sufficient potential to drive the current transition through the leakage inductance of the connector contacts232a–232mand the return contacts239a–239m. It may be desirable to use a small decoupling capacitor246to limit spiking on this node, and it is contemplated that the decoupling capacitor246would be of the same order of magnitude as the load decoupling capacitor245and that both would be small compared to the output capacitor244, as and illustration and a preferred embodiment, not a limitation.

FIG. 8shows a section through a connection system comprising a multilayer printed connector250. The connector250connects two multilayer printed wiring boards251and252. The details of construction for a multilayer printed connector are described in greater detail below. In the example of the connector250ofFIG. 8, eight layers of the printed wiring boards251and252make metal-to-metal contact at areas of complimentary exposed conductor surfaces253—253. There may be slots254extending from the contact area to give the circuit boards251and252greater resiliency in the area of the connector250so that a clamp260may compress the connector area tightly, to make a tight connection in all of the layers of the connector250. As an example, not a limitation, the clamp260may comprise a cam261, a moveable plate262, a fixed plate263(relative to the axis of rotation of the cam261) and resilient pads264,264. Any means for clamping the circuit boards251and252over the connector250would suffice.

FIG. 9shows a possible subassembly270for a printed wiring board having a printed connector. A first laminated layer271comprises an insulating substrate274having copper foil275,275bonded to its top and bottom surface. The copper foil may be “printed” in the usual manner of fabricating printed circuit boards, as by etching and plating. A second laminated layer272comprises an insulating substrate274with copper foil275bonded to its top surface, and a third laminated layer273comprises an insulating substrate274with copper foil275bonded to its bottom surface.

FIG. 10shows the laminates271,272and273bonded together to make a printed wiring board subassembly280. The first laminated layer271extends beyond the second and third laminated layers272and273to comprise a printed connector281. Because the first laminated layer271extends beyond the second and third laminated layers272and273, there is a strip of exposed copper on both sides, and the copper foils275,275of the second and third laminated layers272and273are also exposed.

FIG. 11shows a printed connector290comprising two of the printed wiring board subassemblies280,280making a nested contact in the areas of their respective printed connectors281,281. Where there is metal to metal contact, current can flow through the connectors281,281.

FIG. 12shows a printed connector300comprising a plurality of the subassemblies280ofFIG. 10in a nested interleaved arrangement so that contacts may be made between multiple internal layers of the resulting printed wiring boards. The exact arrangement of the several layers of the multilayer board will vary from application to application, and the various figures show examples, not limitations. There may be more or fewer layers overlapping, and the layers may be varied appropriately. As an example, not a limitation, the outer laminated subassemblies301,301have fewer layers than the internal laminated subassemblies280—280. To provide clearance so that the connector areas281—281are a slip fit one to another, spacer laminated layers302—302are used between the subassemblies280—280and301,301. These spacer laminated layers may be multilayer copper and insulating layers as well, as a printed wiring board likely will need runs and vias in addition to those going to the connector300.

InFIG. 12, ten copper foils275—275make contact with ten complementary copper foils on the other side of the connector300. In addition, the outer surface of both sides may also have copper foils275,275which may be printed with a suitable pattern for mounting components thereon in the usual manner of printed wiring board fabrication. Ten arrows labeled I show the current paths through the connector300. Note that the current may flow in five pairs of closely spaced layers with a fairly even dielectric spacing between them, even in the area where they pass through the connector. Thus there will be little discontinuity in the impedance of the circuits through the connector. Further, the distributed capacitance will be significant, and the distributed capacitance will have essentially no esl. The power buss may have characteristics of a transmission line, and reflections or standing waves would be undesirable.

FIGS. 9 through 12show the copper foils275—275extending the full width of the laminated layers. While it is entirely possible to use the connector with full width contacts, it is contemplated that the copper foils275—275would be printed in the manner of printing a printed wiring board with a pattern of conductors with insulating spaces between them and that they would interconnect within the finished printed wiring board to make a plurality of contacts on each layer.

InFIGS. 9 through 12, the scale is exaggerated to better show the construction of the printed connector. In actuality, the several layers of the printed wiring boards are very thin so when the whole is stacked with prepreg and bonded, the whole assembly is also thin. The finished assemblies may be as shown inFIG. 13.

FIG. 13shows a multilayer printed connector320for connecting first and second printed wiring boards321and322. There are ten surfaces329—329within the connector321where the internal layers of the multilayer printed wiring boards321and322may make direct metal-to-metal contact. To ensure a good electrical connection, a means for clamping may clamp the boards tightly in the area of the connector320. As an example, not a limitation, two plates324,324may be held in tight contact with the printed wiring boards321and322by a bolt327and nut328. To distribute the clamping pressure more evenly, the clamp may further comprise top plates325,325with resilient pads326,326under them. The bolt327and the nut328are preferably captive, and may be restrained by having a through hole in one of the circuit boards and a complementary notch in the other, as an example, not a limitation.

The multilayer printed wiring board321having the printed wiring connector must be fairly precise. Accordingly,FIG. 14shows that a fixture340comprising top and bottom plates may be used to compress and heat the printed wiring board321for bonding, and precision inserts343,343may be inserted into the connector area to ensure the correct spacing. Preferably the precision inserts343,343also provide a sealing function to minimize creepage of the prepreg onto the conductive surfaces.

Usually annealed copper is used for printed wiring board foils. However it is necessary that the edges of the connector have good mechanical integrity so that a good fit is ensured even if they are handled roughly. Accordingly, it may be desirable to fabricate the printed wiring board with a harder temper copper or even a harder material. Harder materials tend to have a higher resistivity, but that may not be important for this application. Because this connection is contemplated for use with a power supply having very fast current transients, high frequency effects must be taken into account, particularly the penetration depth. To get very low impedance for the high frequency components of the current transient, the conductors must have a very wide surface area, because the penetration of the current into the metal is very small at very high frequencies. Therefore the total area of the metal for dc currents will be more than adequate, and some slight increase in resistivity will be tolerable. The higher resistivity is not detrimental to the high frequency component, as a higher resistivity increases the penetration depth proportionally.

The use of a harder metal foil would also permit the outer layer of the connector to be unreinforced metal extended from the outer layer of the printed wiring board with no insulated substrate. The multilayer printed wiring board is a stack of laminate, foil, substrates, prepreg, and there is no reason that bare foil should not be used as well. It could be used internally for a full width connection, and it can be used as the outer layers and etched and plated after stacking and bonding, perhaps after the vias are drilled and plated, as illustrations, not limitations.

FIGS. 15 through 17show how to adapt the teachings ofFIG. 7to a multilayer printed connector. A representative finished printed wiring board350is shown inFIG. 15. For clarity, the same board is shown without its outer layers as a subassembly360inFIGS. 16 and 17, for illustration, not as its preferred finished construction.

Because the contemplated application is for a low voltage, high current power supply with very fast rates of change in the current, the bus for delivering the power is optimized for low inductance and reasonably low resistance at very high frequencies despite the penetration depth limitations. Accordingly, the basic structure ofFIG. 12is chosen, ten layers for the power bus configured as five pairs of interleaved power planes and returns. However, to terminate the output capacitor on separate connector pins, all of the layers are printed with an interdigitated pattern. Extensions of a power plane355are interdigitated with shorter conductors for the output capacitor, which is contemplated to be a large array of small capacitors to minimize its equivalent series inductance (esl). In a connector351, the power contacts357—357are brought to the edge of the printed wiring board350, each being a stack of ten layers, five power contacts interleaved with five returns. The capacitor contacts358—358are shorter and do not connect to the rest of the circuit within the printed wiring card350. Each of the capacitor contacts358—358is also a stack of ten layers, five power contacts interleaved with five returns. This implements the design concept of the connector234ofFIG. 7, as an example.

In this specification and the claims, “print”, “printed” or “printing” refer to the well known processes for making printed wiring boards. A “metal contact” may be printed on an extended exposed metal surface of a metal foil layer of a multilayer printed wiring board as by etching, plating or depositing metal using the normal processes of making multilayer printed wiring boards. Extended exposed metal contacts of a first connector on a first multilayer printed wiring board are defined as being complimentary with respective extended exposed metal contacts of a second connector on a second wiring board if, when the connectors are connected, the respective extended exposed metal contacts make face-to-face, metal-to-metal contact so that an electrical connection is established. It is understood that the respective extended exposed metal contacts are insulated from other extended exposed metal contacts by the insulating laminate and by the manner in which they are printed with spaces between adjacent metal contacts.

FIG. 18shows another problem with very high frequency currents.FIG. 18shows a stack of interleaved wide conductors371—371and372—372in a multilayer printed circuit board, with vias373and374to interconnect them, the via373connecting the layers372—372and the via374connecting the layers371—371. It is contemplated that the source of power is components placed on the surface of the printed wiring board, and it is desired to distribute the power throughout the layers. Although two vias are shown, it is contemplated that there would be a large number of them.

The penetration depth presents a significant problem, as the very high frequency components of the current cannot pass through the thickness of the metal. Nor can high frequency currents pass through the bore of the via. The very high frequency current will have to travel over the surface of the foil, over its edge and back along the bottom surface to the via. Then it can travel down the outside surface to the next layer, but again it cannot penetrate the foil, so once again it is forced to follow a surface path. A dense array of vias, as is sometimes used for high currents, will not be very effective, as the very high frequency current will not penetrate very well to the central vias.

FIG. 19shows that it is preferred to place the vias384—384and385—385at the periphery of the metal foil layers381—381and382—382. Accordingly, it is preferred to layout the printed wiring card so that there are long edges for the conductors so that vias can be placed there.

FIG. 20shows a representative multilayer printed wiring circuit400of this invention for a power supply.FIG. 21shows the printed wiring circuit400with components thereon connected to a load circuit401.

The dashed line shows the location of a multilayer interleaved power bus355that terminates in power contacts357—357in the connector351. In the region designated “A”, a surface layout is provided for mounting power components, contemplated as being modules mounted on the top and bottom of the circuit board,404—404inFIG. 21. The power buss355is digitated through all layers to provide peripheral contacts for a plurality of vias402—402to half of the layers comprising power conductors and a plurality of vias403—403to the other half of the layers comprising return conductors.

In as much as the current may not be equal in the various modules404—404, in a region “B” the multilayer interleaved power bus355spans the entire circuit board so that the current can spread evenly across the circuit board.

The region “B” can also be used for mounting components, perhaps for monitoring and control. A region “C” is where the output capacitors405—405are mounted on interdigitated stacks of interleaved conductors. The region “D” is the connector, and it may be clamped with a clamp402.

On the load card401, at the connector, once again all layers span the entire width of the printed circuit, and it is here that the output capacitor is connected to the power supply output. The surface layers in this region may also be used for components408. The load is shown as a microprocessor403, as an example, not a limitation, and the load may have a plurality of decoupling capacitors406—406. Note that the power buss is once again highly digitated under the decoupling capacitors406—406and the processor403, so that the vias may interconnect the multiple layers on their periphery. The digitations also provide spaces within which the other connections of the processor may be run and terminated.