Power distribution system

One aspect of the present invention provides a power distribution system comprising a first printed circuit board, a power supply, a processor, and a flexible cable connector. Both the power supply and the processor are mounted on the first printed circuit board. The flexible cable connector comprises a first end electrically connected to the processor and a second end electrically connected to the power supply. The flexible cable connector is configured with a length so that the power supply is in a spaced relationship relative to the processor. The flexible connector also extends between the power supply and the processor independent of the first printed circuit board. The flexible cable connector comprises a plurality of insulated power wires and a ground structure. The plurality of insulated power wires are arranged generally parallel to each other extending from the first end to the second end of the flexible cable connector. The ground structure includes a ground shield that surrounds the plurality of insulated power wires and extends from the first end to the second end of the flexible cable connector, with the ground structure configured to provide a return path for current between the processor and the power supply.

BACKGROUND

Computer technology continues to compress greater amounts of computing power, memory and input/output signals in smaller and smaller spaces. As the computing speed of processors, such as central processing units increases, larger amounts of power are required. In addition, the rate change and level of current entering and exiting these processors must be managed very closely. These power and current requirements of today's high-end processors challenge conventional computer circuitry design.

For example, at one time it was previously acceptable to locate a power supply remote from a processor, as in desktop computers where space is relatively generous. Many, if not virtually all, connections between respective circuit modules are made via a printed circuit board on which the modules reside. Accordingly, the power demands of today's high end processors are so high that the power supply for these high-end processors must be located immediately adjacent the processor to avoid disruptive inductance loops through the printed circuit board that are created if the power supply is located remotely from the processor.

While physical coplacement of the power supply and high-end processor on the printed circuit board alleviates an inductance problem, this arrangement introduces a whole set of challenges. For example, the large bulky power pod occupies an important space on a circuit board—the space immediately adjacent the processor. High-end processors have a large number of circuit traces, which require space on the circuit board immediately adjacent the processor. Memory is also sometimes located immediately adjacent the processor. Accordingly, the physical coplacement of the power supply with the processor takes a significant amount of space that otherwise would go to memory, circuit traces, and other circuit elements.

For these and other reasons, conventional ways of placing processors, power supplies, memory, and other functions on a printed circuit board fail to meet the challenges of today's computing power and form factors.

SUMMARY

One aspect of the present invention provides a power distribution system comprising a first printed circuit board, a power supply, a processor, and a flexible cable connector. Both the power supply and the processor are mounted on the first printed circuit board. The flexible cable connector comprises a first end electrically connected to the processor and a second end electrically connected to the power supply. The flexible cable connector is configured with a length so that the power supply is in a spaced relationship relative to the processor. The flexible connector also extends between the power supply and the processor independent of the first printed circuit board. The flexible cable connector comprises a plurality of insulated power wires and a ground structure. The plurality of insulated power wires are arranged generally parallel to each other extending from the first end to the second end of the flexible cable connector. The ground structure includes a ground shield that surrounds the plurality of insulated power wires and extends from the first end to the second end of the flexible cable connector, with the ground structure configured to provide a return path for current between the processor and the power supply.

DETAILED DESCRIPTION

Embodiments of the present invention are directed to a flexible cable connector that distributes power in a low inductance path between a power supply and a processor. In one embodiment, this flexible cable connector enables the power supply can be located remotely from the processor. In one embodiment, the flexible power connector also removes this path for power from some of the power and ground planes of the printed circuit board that support the processor. Moreover, the low inductance path provided by one embodiment of the flexible power connector enables other components, such as memory and other circuit traces and elements, to be located immediately adjacent the processor.

One exemplary embodiment of the present invention is shown generally inFIG. 1as system10. System10comprises power supply12, flexible cable connector14, processor16, memory17, and first printed circuit board30(e.g. motherboard), on which these system components are mounted. System10also comprises second printed circuit board20(e.g. daughterboard), which is mounted on first printed circuit board30, and which comprises capacitive coupler22including a plurality of capacitors23. However, in one aspect, power supply12is optionally located on a frame (e.g. chassis) remote from printed circuit board30, as will be described in more detail in association withFIG. 3.

Processor16comprises a microprocessor or central processing unit (CPU), particularly those used in high density computing. One example of processor16includes a high-end processor, which has high power requirements and stringent current requirements (e.g. high step current criteria), and which conventionally receives power from a power pod (e.g. power supply) located immediately adjacent to processor16. One example of processor16comprises a 64 bit Itanium processor from the Itanium Processor Family from Intel. Processor16is disposed on first printed circuit board30as part of a computer server, or workstation.

Power supply12is a power supply for operating processor16, as well as other components of first printed circuit board30or server environment. In one aspect, power supply12is a power supply for a rack server, or other computer server/workstation. In another aspect, power supply12is a power supply for a blade server that is disposed on a blade chassis, separate from printed circuit board30, for connecting to the blade server.

Second printed circuit board20comprises a mounting structure such as a daughterboard adapted for mounting processor16on first printed circuit board30, which acts as a motherboard. Capacitive coupler22comprises a plurality of capacitors23, such as high speed capacitors, adapted to provide capacitive coupling between flexible cable connector14and processor16. Capacitive coupler22maintains a stable voltage for processor16and facilitates meeting the high current step requirements of processor16.

Second printed circuit board20is optionally omitted from system10so that processor16is mounted directly to first printed circuit board30in an arrangement substantially to that shown inFIG. 5, such as system100, in which processor110is mounted directly to circuit card102. In this aspect of system10, capacitive coupler22is optionally mounted directly on first printed circuit board30for electrically coupling flexible connector14to processor16.

Flexible cable connector14provides a low inductance path for distributing power transmission among a plurality of insulated power wires and a plurality of return ground wires between processor16and power supply12. Each insulated power wire62is matched with its own ground wire60or a combination of ground wires60. Flexible cable connector14is flexible and resilient so that it can be manipulated into various curved structures.

Flexible cable connector14is independent (e.g. physically and electrically separated from) of first printed circuit board30(and second printed board20) on which processor16is mounted. This configuration enables achieving the low inductance path through the multi-wire rolled sheet configuration of flexible cable connector14while also saving space within first printed circuit board30and saving space immediately adjacent to processor16on the surface of first printed circuit board.

The low inductance feature of flexible cable connector14enables power supply16to be placed at a location remote from processor16since flexible cable connector14minimizes an inductance loop that otherwise occur using conventional power connection schemes over extended distances when supplying power to processor16. This feature enables memory17to be located immediately adjacent to processor16(as shown inFIG. 1), demonstrating physical separation of power supply12and processor16which are no longer co-located together on first printed circuit board30(or on second printed circuit board20).

FIG. 2Ais a sectional view of flexible cable connector14.FIG. 2Aillustrates flexible connector14being configured as a cable and comprising insulator jacket40and power distribution sheet42that has been manipulated into rolled configuration41A. Jacket40electrically insulates power distribution sheet42from a surrounding electrically active environment, such as first printed circuit board30and second printed circuit board20and any circuit elements disposed on first and second printed circuit boards30,20. Power distribution sheet42comprises first side edge43and second side edge44. As shown inFIG. 2A, first side edge43of sheet42is adjacent a cross-sectional center of flexible cable connector14and second side edge44of sheet42is adjacent an outer surface of flexible cable connector14. Power distribution sheet42is arranged in rolled configuration41A to permit sheet42to be more easily used as a cable by minimizing a cross-sectional profile of flexible connector14and by enhancing maneuverability of flexible connector14for routing over first printed circuit board30.

FIG. 2Billustrates another aspect of flexible cable connector14in which power distribution sheet42is manipulated into folded configuration41B instead of rolled configuration41A. However, in all other respects, flexible cable connector14shown inFIG. 2Bhas substantially the same features and attributes as flexible cable connector14shown inFIG. 2A. As shown inFIG. 2B, power distribution sheet42in folded configuration41B comprises first edge43, second edge44, fold lines47, and flaps48. Power distribution sheet42is folded from a generally flat configuration (FIG. 3) into folded configuration41B by folding flaps48relative to other portions of sheet42along fold lines47that extend generally parallel to a longitudinal axis of sheet42(see axis A inFIG. 3) and thereby generally parallel to a length of flexible cable connector14. Flaps48are folded to have a Chinese-fan configuration (as shown) in which flaps48are folded to be away from each other, or optionally can be folded like a letter so that flaps48rest on top of each other. Other folding configurations can be implemented with the resulting configuration yielding a smaller cross-sectional profile to reduce the diameter of flexible cable connector14and such that the configuration enhances flexibility and maneuverability of flexible cable connector14.

FIGS. 3 and 4illustrate power distribution sheet42in its unrolled configuration, i.e., at a point in time prior to being rolled into the rolled configuration that is shown inFIG. 2.FIG. 3is a plan view of power distribution sheet42with second ground shield52removed for illustrative purposes to reveal the structures seen inFIG. 3.FIG. 4is a sectional view ofFIG. 3as taken along lines4—4, and which illustrates second ground shield52in its original location (i.e., prior to its removal inFIG. 3for illustrative purposes). In addition,FIG. 4illustrates the elements of power distribution sheet42in an enlarged view to better illustrate each of the elements and their respective relationships. However, when fully assembled, elements of power distribution sheet42are compressed together to define a sheet-like low profile singular unit.

As shown inFIG. 3, power distribution sheet42is an elongate member comprising first end45and second end46, with first end44electrically connected to power supply12and second end46electrically connected to processor16. Second end of sheet42is optionally connected to processor16via optional daughter board20including capacitive coupler22(as shown inFIG. 1).

Power distribution sheet42of flexible cable connector14comprises ground structure50and a plurality of insulated power wire(s)62, and optional signal wire(s)64. Ground structure50acts a return path for current between processor16and power supply12. Ground structure50comprises a ground shield including first ground shield portion52B and second ground shield portion52A (FIG. 4), as well as optionally comprising a plurality of ground wires60. Later embodiments shown inFIGS. 10–11describe and illustrate an aspect of ground structure50that omits a plurality of ground wires60that are distinct from first and second ground shield portions52B,52A.

As shown inFIG. 4, first ground shield portion52B and second ground shield portion52A are made of a braided metal mesh, a solid metal material (e.g. thin metal foil), or other known flexible grounding materials. As shown inFIG. 4, first ground shield52B and second ground shield52A are defined as a single member. However, first ground shield portion52B and second ground shield portion52A are optionally removably separable along separation line51adjacent side edge53to form two physically separate portions. Moreover, as later shown inFIG. 7, first ground shield portion52B and second ground shield portion52A are also optionally defined as physically separate members rather than a single member that is separable into two distinct portions. In any case, whether physically separated or not, first and second ground shield portions52B,52A define a single ground shield for surrounding power wires62(and optionally ground wires60) and act as part or all of ground structure50to provide a return current path between processor16and power supply12.

As further shown inFIG. 4, power distribution sheet42further comprises first adhesive sheet54and optional second adhesive sheet55. As seen inFIG. 3, a portion of first adhesive sheet54is removed for illustrative purposes to reveal first ground shield52B.

As shown inFIG. 3, in this embodiment of flexible cable connector14, ground structure50includes ground shield portions52B,52A and ground wires60, which are aligned generally parallel to a longitudinal axis (A) of power distribution sheet42. Ground wires60also are aligned generally parallel to power wires62in a side-by-side alternating arrangement (e.g., ground, power, ground, power, etc.) so that each power wire60and ground wire62are spaced from each other by a fixed distance D. Ground wires60and power wires62are secured in this position by placement on first adhesive sheet54.

First adhesive sheet54(and second adhesive sheet55) comprises a thin, flexible sheet with two opposed surfaces with each surface bearing a pressure sensitive adhesive. For example, first and second adhesive sheets54,55comprise an insulative polyimide tape available as Kapton® tape available from E. I. du Pont de Nemours and Company.

Because first adhesive sheet54comprises two opposed adhesive surfaces, first surface54A of first adhesive sheet54secures power wires62and ground wires60to first adhesive sheet54while second surface54B of first adhesive sheet54secures first adhesive sheet54to first ground shield50. When second ground shield52is pressed downwardly onto power wires62, ground wires60, and first surface54A of first adhesive sheet54, then second ground shield52becomes secured to first adhesive sheet54upon pressing contact with exposed portions (e.g., first surface54A) of first adhesive sheet54. Securing second ground shield52to first adhesive sheet54in this manner further maintains power wires62and ground wires60in their generally parallel, side-by-side, alternating arrangement on first adhesive sheet54.

In addition, power distribution sheet42further optionally comprises second adhesive sheet55. Optional second adhesive sheet55comprises two opposed adhesive surfaces, first surface55A of second adhesive sheet55for additionally securing power wires62and ground wires60(in their generally parallel, side-by-side alternating arrangement) to second adhesive sheet55while second surface55B of second adhesive sheet55secures second adhesive sheet55to second ground shield52. However, even though second adhesive sheet55is added, power wires62and ground wires60are still secured to first adhesive sheet54. First and second adhesive sheets54and55are optionally provided as a single adhesive insulative sheet.

Optional signal wires64carry control and monitoring signals between processor16and power supply12, and also are aligned generally parallel to the set of power wires62and ground wires60in a side-by-side relationship.

Power wires62and ground wires60are arranged together in a side-by-side structure so that each power wire62has a complementary ground wire60to act as a ground return path for current. Signal wires64can be disposed at any location among multiple ground and power wires60,62. Finally more than one ground wire60can be placed between respective power wires62or signal wires64to provide each power plane with its own return ground return path.

To achieve a minimal inductance loop via power distribution sheet42of flexible connector(s)14, the number of power wires62, and ground wires60of flexible connector(s)14can be varied based on a length of flexible connector(s)42, the power and current requirements of processor16, and the characteristics and placement of power supply12, as well as the number and type of desired power planes. A greater number of power wires62and return ground wires60generally aids in further minimizing the inductance loop between power supply12and processor16.

Whether configured as a single member or separated, first ground shield portion52B and second ground shield portion52A electrically define the same or single ground reference, and act to shield power wires62(and optionally ground wires60) from external electrical environments such as electromagnetic forces (EMF) adjacent flexible cable connector14.

Other aspects of ground structure50, specifically including various combinations of ground wires60as implemented with power wires62of flexible cable connector14are later described and illustrated inFIGS. 7–11.

FIGS. 5 and 6illustrate an alternate embodiment for implementing flexible cable connector14as a low inductance path in which a power supply is not located on the same circuit card (e.g. motherboard, server card, etc) as the processor.

Circuit card102comprises a blade server, a brick server, or other circuit card that is removably insertable into chassis104wherein chassis104provides power to circuit card102from power supply120via buses114and122.

System100comprises substantially all of the same features and attributes of system10ofFIGS. 1–2, except that power supply120is not located on the same printed circuit board as processor110. In particular, flexible connector112comprises substantially all the same features and attributes of flexible cable connector14. In addition, processor110also optionally is mounted on daughterboard (such as second printed circuit board20inFIG. 1), which would in turn be mounted on circuit card102. Moreover, with or without a daughterboard, processor110is optionally connected to flexible connector112via a capacitive coupler, in a manner substantially similar to the use of capacitive coupler22, as described and illustrated in association withFIG. 1.

As shown inFIG. 5, first end130of flexible connector112is electrically connected to processor110and second end132of flexible connector112is electrically connected to bus114of circuit card102. Bus114includes a connector port for receiving second end132of flexible connector112. When circuit card102is removably connected to chassis104, bus114of circuit card102is electrically and mechanically connected to bus122of chassis104to thereby connect power supply120to processor110via flexible connector112.

Accordingly, flexible connector112enables a low inductance path for power between a processor and a power supply even when the power supply is not located on the same circuit card as the processor. This feature makes flexible cable connector14well suited for use in high density computing, such as blade server systems.

FIG. 6is a partial side view ofFIG. 5that illustrates the physical separation between flexible connector112and circuit card102. As shown inFIG. 6, flexible connector112extends between bus114and processor110. Flexible connector112is separate from and is spaced above a surface130of circuit card102(e.g. printed circuit board) so that power planes and return ground planes defined by power wires62and ground wires60, respectively, of flexible connector112do not pass through server card102between processor110and power supply114.

An alternate embodiment of flexible cable connector14comprises power distribution sheet140, which is shown inFIG. 7. Power distribution sheet140has substantially the same features and attributes as power distribution sheet42(FIG. 2–4) except for ground structure50including a different arrangement of ground wires60relative to power wires62. In this arrangement, power wires62are interspersed among a latticework of ground wires60such that ground wires60are disposed in between, over, and around power wires62. As before, both ground wires60and power wires62are secured in place by first adhesive sheet50and second adhesive sheet52.

FIGS. 8 and 9illustrate an alternate embodiment of flexible cable connector14comprising power distribution sheet154. As shown inFIGS. 8–9, power distribution sheet154has substantially the same features and attributes as power distribution sheet42(FIGS. 2–4) except that ground structure50comprises ground wires60of ground structure50being incorporated along with power wires62as twisted wire pairs158. Each twisted wire pair158comprises a single insulated power wire62and a single ground wire60assembled together in the form of a twisted pair. A twisted wire pair configuration for general purposes (e.g. telephone lines) is known to those skilled in the art. Physically coupling an insulated power wire62and a ground wire60in a pair insures that each power wire62has its own ground wire60for a ground return path for current, and also simplifies assembly of power distribution sheet154because multiple twisted pairs can be laid out on adhesive sheet54more simply than individual power wires62and ground wires60(as inFIG. 3–4). Moreover, each twisted pair158can carry a single voltage so that with a plurality of the twisted pairs158, several different voltages can be carried by flexible cable connector14. In addition, the twisted pair configuration including a dedicated ground path for each power wire62enables careful management of the voltage level and managing low power consumption. Finally, twisted pairs158of insulated power wires62and ground wires60reduce noise.

As shown inFIG. 8, twisted wire pairs158are aligned generally parallel to each other in a side-by-side relationship with a fixed distance D between respective twisted wire pairs158.

Accordingly, twisted wire pairs158can be combined with other aspects of flexible cable connector14such as the ground structure arrangements of FIGS.3,7, and10, so that multiple aspects of ground structure50are combined in a single flexible cable connector14. For example, twisted wire pairs158can be arranged as part of a power distribution sheet42(FIG. 3), power distribution sheet140(FIG. 7), or power distribution sheet180(FIG. 10) such that twisted wire pairs158are interposed amongst the generally parallel arrangement of power wires62and ground wires60(except for power sheet180which omits ground wires60). In this manner, a single flexible cable connector14can optionally include one or more carefully regulated, different voltage levels provided by one or more twisted pairs158, and the other insulated power wires62that are not in the twisted pair configuration.

FIGS. 10 and 11also illustrate an alternate embodiment of flexible cable connector14comprising power distribution sheet180. As shown inFIGS. 10–11, power distribution sheet180has substantially the same features and attributes as power distribution sheet42(FIGS. 2–4) except that ground structure50omits ground wires60from side-by-side placement next to power wires62and instead are embodied in first and second ground shield portions52B,52A. In particular, individual ground wires60are not placed on first adhesive sheet52adjacent to power wires62. Instead, first ground shield52B (and optionally second ground shield52A), which is itself an aggregation of ground wires in the form of a braided mesh, provides a return ground path of current for power wires62.

In this arrangement, insulated power wires62are still arranged in a side-by-side, generally parallel relationship with each other yet omitting an alternating relationship with ground wires60. Insulated power wires62are also maintained, by their fixation on first adhesive sheet52, at a fixed distance D from each other.

Like the embodiments of power distribution sheets42,140,154described and illustrated in association withFIGS. 3–4,7–9, respectively, power distribution sheet180extends between power supply12and processor16(and optionally daughter board20).

Embodiments of the present invention directed to a flexible cable connector provide a low inductance path between a power supply and a processor. The flexible cable connector enables locating the power supply remotely from the processor while still meeting the stringent power and current requirements of high end processors. Consequently, premium space that is closest to the processor can be used for memory, circuit traces, and other circuit elements instead of being used for a bulky power pod. Moreover, since the power supply no longer needs to be co-located with the processor, there is much greater freedom in laying out a printed circuit board to optimize placement of all the components of the printed circuit board.