U.S. patent application number 10/370121 was filed with the patent office on 2003-07-03 for configurable power distribution circuit.
Invention is credited to Cruz, Claude A..
Application Number | 20030126482 10/370121 |
Document ID | / |
Family ID | 25539743 |
Filed Date | 2003-07-03 |
United States Patent
Application |
20030126482 |
Kind Code |
A1 |
Cruz, Claude A. |
July 3, 2003 |
Configurable power distribution circuit
Abstract
Briefly, in accordance with one embodiment of the invention, a
circuit includes: a physical arrangement of power transistors. The
circuit is adapted to couple a node to a power bus segment. The
physical arrangement of power transistors is electronically
configurable, based on externally derived electrical signals, to
sink power to the node from the power bus segment, source power
from the node to the power bus segment, and distribute power
through the node
Inventors: |
Cruz, Claude A.; (Hillsboro,
OR) |
Correspondence
Address: |
BLAKELY SOKOLOFF TAYLOR & ZAFMAN
12400 WILSHIRE BOULEVARD, SEVENTH FLOOR
LOS ANGELES
CA
90025
US
|
Family ID: |
25539743 |
Appl. No.: |
10/370121 |
Filed: |
February 18, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10370121 |
Feb 18, 2003 |
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08993598 |
Dec 18, 1997 |
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6539484 |
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Current U.S.
Class: |
713/300 ;
709/253 |
Current CPC
Class: |
G06F 1/26 20130101 |
Class at
Publication: |
713/300 ;
709/253 |
International
Class: |
G06F 001/26; G06F
015/16; G06F 001/28; G06F 001/30 |
Claims
1. A circuit comprising: a physical arrangement of power
transistors; said circuit being adapted to couple a node to a power
bus segment; said physical arrangement of power transistors being
electronically configurable, based on externally derived electrical
signals, to sink power to the node from the power bus segment,
source power from the node to the power bus segment, and distribute
power through the node.
2. The circuit of claim 1, wherein said arrangement of transistors
are also electronically configurable so that at least two power bus
segments are capable of being coupled to the node and
electronically isolated from each other at the node.
3. The circuit of claim 2, wherein said transistors comprise power
field effect transistors (FETs).
4. The circuit of claim 2, wherein said circuit is coupled to a bus
for transferring signals compliant with the 1394 specification.
5. The circuit of claim 1, wherein the power bus segment comprises
a power bus segment via which nodes with a particular set of power
sink/source relationships may be coupled.
6. The circuit of claim 5, wherein said particular set of power
sink/source relationships is time-varying.
7. The circuit of claim 1, wherein said node comprises at least a
physical layer and a link layer.
8. The circuit of claim 1, wherein said physical arrangement of
power transistors is embodied on an integrated circuit (IC)
chip.
9. A method for distributing power among a plurality of nodes via a
power bus, comprising: electronically isolating portions of the
power bus into at least two power bus segments; and configuring
particular sets of power sink/source relationships among the nodes
coupled to the respective power bus segments of said at least two
power bus segments.
10. The method of claim 9, wherein said nodes each comprise at
least a physical layer and a link layer.
11. The method of claim 9, wherein configuring particular sets of
power sink/source relationships among the nodes comprises
configuring time-varying power sink/source relationships among the
nodes.
12. The method of claim 9, wherein the nodes are also coupled by a
bus comprising a bus for transferring signals compliant with the
1394 specification.
13. The method of claim 9, wherein configuring particular sets of
power sink/source relationships among the nodes comprises applying
externally derived electrical signals to an electrically
configurable physical arrangement of power transistors.
14. A method for distributing power among a plurality of nodes via
a power bus coupling the plurality of nodes together, comprising:
configuring at least one particular set of power sink/source
relationships among the nodes coupled via the power bus.
15. The method of claim 14, wherein configuring at least one
particular set of power sink/source relationships comprises
configuring another particular set of power source/sink
relationships other than the at least one particular set of power
source/sink relationships.
16. The method of claims 15, wherein the two sets of particular
power source/sink relationships are electrically isolated and form
two power bus segments.
Description
RELATED APPLICATION
[0001] This patent application is related to U.S. patent
application Ser. No. 08/954,334, titled "Circuit and Method for
Power Distribution Management, filed Oct. 17, 1997, by Steven R.
Bard, assigned to the assignee of the present invention, and herein
incorporated by reference.
BACKGROUND
[0002] 1. Field of the Invention
[0003] The present invention relates to a power distribution
circuit and, more particularly, to a configurable power
distribution circuit.
[0004] 2. Background Information
[0005] In a variety of situations, it is desirable to have the
ability to transfer power between different systems or devices. It
might be desirable, for example, to have the capability for a
notebook computer to provide operating power to an attached
peripheral device, such as a camera or a scanner. Likewise, it
might be desirable for a personal computer (PC) docking station to
provide operating power to a notebook computer docked to that PC
docking station, such as via a power bus or power distribution
cable, for example.
[0006] This capability, however, introduces complexities related to
configuring the power source/sink relationships between a set of
devices or systems. Of course, in this context, power source/sink
relationships includes relationships in which power is neither
sourced nor sinked, such as in a "pass through" relationship, as
explained in more detail herein. (Likewise, the terms "source/sink"
and "sink/source" are used interchangeably.) It would be desirable
if a circuit or technique were available to address these power
distribution complexities.
SUMMARY
[0007] Briefly, in accordance with one embodiment of the invention,
a circuit includes: a physical arrangement of power transistors.
The circuit is adapted to couple a node to a power bus segment. The
physical arrangement of power transistors is electronically
configurable, based on externally derived electrical signals, to
sink power to the node from the bus segment, source power from the
node to the bus segment, and distribute power through the node.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] The subject matter regarded as the invention is particularly
pointed out and distinctly claimed in the concluding portion of the
specification. The invention, however, both as to organization, and
method of operation, together with objects, features, and
advantages thereof, may best be understood by reference to the
following detailed description, when read with the accompanying
drawings, in which:
[0009] FIG. 1 is a circuit diagram illustrating an embodiment of a
configurable power distribution circuit in accordance with the
invention;
[0010] FIG. 2 is a block diagram illustrating an embodiment of a
node complying with the IEEE 1394 specification that may employ an
embodiment of a configurable power distribution circuit in
accordance with the invention;
[0011] FIG. 3 is a schematic diagram illustrating an embodiment of
a network employing an embodiment of a configurable power
distribution circuit in accordance with the invention;
[0012] FIG. 4 is a table of possible configurations for the
embodiment of FIG. 1;
[0013] FIG. 5 is a circuit diagram illustrating an embodiment of a
configurable power distribution circuit in accordance with the
invention coupled to a generalized node; and
[0014] FIG. 6 is a schematic diagram illustrating power source
selection and associated relationships for a node.
DETAILED DESCRIPTION
[0015] In the following detailed description, specific details are
set forth in order to provide a thorough understanding of the
invention. However, it will be understood by those skilled in the
relevant art that the present invention may be practiced without
these specific details. In other instances, well-known methods,
procedures, components, and circuits have not been described in
detail so as not to obscure the present invention.
[0016] FIG. 1 is a circuit diagram illustrating an embodiment 100
of a configurable power distribution circuit in accordance with the
present invention. Of course, many embodiments are possible and the
invention is not limited in scope to the one illustrated. For
example, although the invention is not limited scope in this
respect, embodiment 100 is illustrated as embodied on an integrated
circuit (IC) chip. As illustrated in FIG. 1, embodiment 100
comprises a physical arrangement of power transistors, such as 160,
150, 130, 170, 180, 120, 1 10 and 130. The integrated circuit is
adapted to couple a node to; a power bus or power bus segment, such
as a power distribution bus or cable, here comprising power bus
segments 90, 105, and 95. Bus segment 105 comprises a
"pass-through" segment and is internal to the node in this
embodiment. In this context, a power bus or power distribution
cable includes a collection of power bus segments that are coupled
via intervening electrical circuitry. Likewise, in the context, a
power bus segment refers to an electrical connection or coupling
for transferring power between or via electrically isolated sink,
source or pass-through nodes. As illustrated in FIG. 1, the node in
this embodiment comprises at least a physical layer 190 and a link
layer 222, although the invention is not limited in scope in this
respect. In this context, the term node refers to a bus or bus
segment interface plus one or more coupled devices. As will be
explained in more detail hereinafter, the physical arrangement
of-power transistors is electronically configurable, based on
externally derived electronic or electrical signals, to sink power
to the node from a bus segment or segments, source power from the
node to a bus segment or segments, and distribute power through the
node, such as across a power bus segment or segments, to another
node or nodes. Furthermore, as will be explained in more detail,
the physical arrangement of power transistors are also
electronically configurable so that the power bus segments
comprising the power bus may be electrically isolated to form
"power domains", as explained in more detail hereinafter.
[0017] The IEEE 1394 specification, "IEEE Standard for a High
Performance Serial Bus", IEEE Std 1394-1995, Aug. 30, 1996,
available from Institute of Electrical and Electronics Engineers,
Inc. (IEEE), 345 East 47.sup.th Street, New York, N.Y. 10017,
(hereinafter 1394 specification), describes a high speed serial bus
that includes the capability for sourcing power from one "node" to
another over a power bus coupling the nodes. As previously
indicated, this power sourcing capability might be used, for
example, to allow a notebook computer to provide operating power to
an attached peripheral device, such as a camera or a scanner,
although the invention is not limited in scope to this example. It
might also enable a PC docking station to provide operating power,
via a 1394 specification compliant cable or bus, for example, to a
docked notebook computer. However, as previously indicated, this
power sourcing capability introduces potential complexities into
the process of configuring the power source/sink relationships
between a set of devices or systems, such as those coupled by a
1394 specification compliant bus. For example, at any given time,
one device should be providing or sourcing power and the remaining
devices should either consume power as a power sink, power
themselves, or act as a power "conduit" distributing power from the
power source to devices coupled to the power distribution bus or
cable (but not directly coupled to the power source).
[0018] This situation is made more complex because a 1394
specification compliant device or system may operate in any one of
several states ranging from full functionality to a powered-down
state with limited functionality. Depending on the particular
situation, this may result in a 1394 specification compliant bus
being effectively separated into disjoint power bus segments (e.g.,
the bus may become "fragmented"). In this context, the term
disjoint refers to power bus segments that are electrically
isolated from each other. This may result in problems for bus or
cable powered devices or systems located downstream relative to the
bus or cable power source. In other words, the power provided by
the power source might not be transferred to the bus segment that
is disjoint from the bus segment directly coupled to the power
source, thus rendering devices on such disjoint segments
non-functional.
[0019] Using the 1394 specification as one example only, a 1394
specification compliant interface has a tiered structure including
three layers: the PHY, link and transaction layers. In one
embodiment, the physical-interface layer, or PHY, may provide an
electrical interface to a 1394 specification compliant cable. The
PHY includes primarily analog circuitry, including per-port
functions, such as bus-port receivers, transmitters and
signal-level comparators, and functions which may be shared across
ports, such as bit-stream encoders, decoders, synchronization
circuits and clock-generation circuits (phase-locked loops). The
link layer may provide packetizing services, and may intervene
between the PHY and the higher-level transaction layer. The link
layer may comprise digital circuitry to perform data serialization
and deserialization, data framing and checking, isochronous (e.g.,
guaranteed-bandwidth) cycle control, and, perhaps, packet
buffering, for example. The transaction layer may comprise a
digital hardware and software structure which may provide three
types of packet-based transactions: read, write and lock (to allow
atomic, or indivisible, transaction sequences). For a 1394
specification compliant node, all higher-level 1394 protocols make
use of the transaction layer. Two low-power operating modes are
being proposed for inclusion in a new IEEE specification or
standard, being referred to informally as "the 1394 a
specification" and available in draft form, such as currently,
draft 0.9, from IEEE. A "standby" mode allows an interface to
continue to propagate bus traffic, while a device attached to the
bus through that interface is in a "sleep" state. The "suspend"
state or mode saves substantially more power, at the cost of not
permitting the bus to process packet traffic. Rather, in the
suspend state or made, nodes coupled to the bus are only able to
generate or receive "wake-up" events, such as changes in node
battery state, occurrence of a telephony "ring-indicate" signal,
etc. In a normal operating state, a 1394 specification compliant
node's PHY and link layer are both power on. This is not the case
in low-power states. In standby, for example, the PHY is powered,
but only portions of the link layer are on or operating. In
suspend, the link layer is off or not operating, and the PHY is
receiving low-current "trickle" power. In addition to varying the
current and voltage levels for a node's PHY and link layers, the
latter may draw power from either of two sources: either from a
1394 specification compliant cable, or from a power source located
within the node. A link layer's or PHY's power source may change
over time, such as when a battery-powered node switches to a just
acquired alternating current (AC) power source. Therefore, having
the capability to make this selection would be a desirable feature.
Of course, the 1394 specification is provided only as an example
and the invention is not restricted in scope to use with buses or
nodes that only comply with the 1394 specification.
[0020] FIG. 2 is a schematic diagram illustrating an embodiment of
a node coupled to a signal bus compliant with the 1394
specification. Of course, again, the invention is not restricted in
scope to use in this particular embodiment. Thus, again, the
invention is not restricted in scope to use in connection with a
1394 specification compliant bus. In this particular embodiment,
however, a 1394 specification compliant node includes at least a
physical layer (PHY) and a link layer, as previously indicated. A
physical layer is directly coupled to a bus signal path, such as
bus signal path 210 illustrated in FIG. 2. As illustrated in FIG.
2, physical layer 220 has one port. FIG. 2 illustrates analog
transceiver 230 coupled to bus signal path 210 via this port. In a
1394 specification compliant bus, each port is coupled to one other
port, resulting in a point-to-point structure; however, packets are
routed to all active nodes providing the ability for a node to
communicate with any other node. Physical layer 220 includes
typically operations, such as clock generation and signal encoding
and decoding. Therefore, the analog signals received via a signal
path 210 are decoded into digital signals to be provided to link
layer 240. Likewise, binary digital signals or bits provided in a
bit stream via link layer 240 to physical layer 220 are encoded by
physical layer 220 for transmission via bus signal path 210. As
indicated, the link layer performs packet processing typically,
such as bit serialization, bit deserialization, addressing, packet
assembly, and packet disassembly. Likewise, transaction layer 260
performs operations, such as reading, writing and atomic, or
indivisible, read-modify-write cycles, as described. In this
particular embodiment, 270 comprises an Open Host Controller
Interface (OHCI) specification compliant device which is coupled to
a host computer system 280, such as a personal computer (PC),
although the invention is not limited in scope in this respect.
[0021] Physical layer 220, in FIG. 2, does not handle the node's
power requirements in this embodiment; however, an embodiment of
the invention might be used in an environment where it includes
power switching circuits or input-output ports to support external
power switching signals. In this embodiment, however, a power
distribution network is separate from, but operates in parallel
with, the signal paths. In this context, a power distribution
network refers to the network coupling a self-contained or
independent set of power source/sink relationships between a
plurality of nodes coupled via a collection of power cable or power
bus segments, referred to here as a power cable or power bus. The
power-distribution network may either accept power into the node or
from the bus, it may feed power from the node onto the bus, it may
pass or distribute bus power through the node, enabling other nodes
or it may fragment the power network into independent "power
domains" at the node. However, as previously described a 1394
specification compliant node may be in any one of several
operational or power states. The node's power state affects the
operation of the device's physical layer, which provides an
electrical interface for transferring data and control, and its
link layer, which provides packet processing operations. A node's
PHY and link layer may have different and independent power
requirements in different power states. In addition, it may be
desirable to reconfigure a node's power bus based at least in part
on the node's state since the signal path capabilities of the node
may be employed for management of the power bus. Without this, for
example, the power network of a 1394 specification compliant
power,bus may effectively be divided into two disjoint or
electrically isolated bus segments, which may result in problems
for bus or cable-powered devices or systems located downstream of
the interrupting node relative to the present power source.
[0022] In another undesirable situation, a node coupling a power
source to a power consumer or sink may be in a low power or
"disabled" state. The power source will be unable to communicate
with the power consumer that is using or possibly even exhausting
supplied power. Likewise, power utilization by the power consumer
"behind" the disabled node (with respect to the power source) may
increase, resulting in a drain of even more power potentially.
Thus, scenarios exist in which the power utilized may become
effectively unmanageable.
[0023] The embodiment illustrated in FIG. 1 comprises a mechanism
or technique for performing configurable or reconfigurable power
distribution, such as over a 1394 specification compliant bus,
although the invention is not limited in scope to buses complying
with the 1394 specification. This embodiment includes the
capability to independently select the power sources for a 1394
specification compliant node's physical and link layers, by drawing
from an internal power source or a power source available via the
power bus. Likewise, it includes the ability for the 1394 compliant
power bus to be partitioned at the node, resulting in two
independently manageable, electrically isolated, power bus segments
or "power domains" on either side of the node. Therefore, each
resultant "bus segment" may include its own set of distinct or
particular power source/sink relationships. Likewise, this
particular embodiment includes the capability for a node to
selectively supply power to either or both of these two power bus
segments or to the power bus as a whole, forming a single power
domain from adjacent and electrically coupled power-bus
segments.
[0024] In FIG. 1, physical layer 190 and link layer 222 are
illustrated at the top of the figure along with an optional node
internal power source 212 which may be employed to supply power to
the power bus or to the node's PHY and/or link layer. Likewise,
although the invention is not limited in scope in this respect, the
configurable power distribution circuit is illustrated as embodied
on a separate integrated circuit. Physical layer 190 may be
configured to draw power either from the node's internal power
source 212 or from the power bus, more specifically from bus
segment 90, but observe that segment 90 may also be electrically
linked to power bus segments 105 and 95 through power transistors,
such as power field effect transistors (FETs) 110 and 120. Thus,
PHY 190 may draw power from bus segments 90 or 95, for example.
This may be accomplished in this embodiment by setting the control
signal of a physical layer selector switch, such as D;.to a "one"
or to a "zero" to select power from segment 90 or internal power,
respectively, assuming, for example, that 160 and 180 comprise
N-junction FETs and 130 and 150 comprise P-junction FETs. In this
embodiment, the physical layer selector switch is implemented as a
pair of power transistors and voltage signals having a voltage
signal level indicating a logical "one" or "zero" are applied to
the transistors' gates. Of course, power bipolar transistors might
alternatively be employed. Likewise, the control signal for
transistors 130 and 180 select the power source for the link
layer/device in a similar manner.
[0025] As illustrated, two field effect transistors (FETs) 110 and
120 are interspersed serially in the power bus. Control signals may
be applied to these FETs so that bus segments 90 and 95 of the
power bus couple to or electrically isolate from one another. In
addition, in this embodiment, FET 170 is employed to enable or
disable current flow from the node's internal power supply 212 to
internal bus segment 105. In this particular embodiment, a
sufficient voltage applied to the gate of transistor 110 enables
current flow across the associated FET and, likewise, for
transistor 120, from the node's internal power supply to the power
bus. Likewise, in this embodiment; a diode 140 is included in the
current flow path. In this embodiment, this protective diode is
employed to ensure that power does not flow into the node's
internal power source in the event that a higher voltage power
source is coupled to the power bus.
[0026] FIG. 4 is a table describing the operation of this
particular embodiment. The left portion of the table provides the
possible combinations of the five control signals that may be
applied to this particular embodiment. The right portion of the
table provides the physical layer and link layer power source
selections resulting from the associated control signal states as
well as the relationship of the bus segments. It should be noted
that the table includes some redundancy in that different applied
control signals provide the same results With respect to power
source selections. Therefore, the redundant rows may be eliminated
without a loss of capability in this particular embodiment. This is
illustrated in FIG. 4 by shading for the redundant rows. For
example, table rows 5, 9, and 17 implement the same switching
mechanism as that of row 1, and, thus, may be eliminated.
[0027] Based on the previous description, a situation might occur
in which a first node=3 s internal power source is enabled to
supply power to the cable, and the first node's physical layer and
link layer are configured to draw power from the-cable, yet the
first node's physical and link layers do not obtain power from the
first node's internal supply. For example, a higher voltage source
of a second node may also be coupled to the power bus. The second
node may actually supply the bus power including that drawn by the
first node's physical layer and link layer. In this situation, the
first node's protective diode prevents power from flowing into the
first node's internal supply.
[0028] Of course, the invention is not limited in scope to this
particular embodiment or to an embodiment that includes all of the
operational functionality previously described. Depending upon the
situation, it may be desirable to employ a node with less than full
functionality. For example, again, using the 1394 specification as
an example, the physical layer and link layer may be designed or
constructed to only obtain power from the power bus, and,
therefore, an internal supply may not be needed. Likewise,
depending upon the situation, it may not be desirable to employ
power transistors (e.g., 110 and 120 in FIG. 1) to provide separate
power domains. The advantages of these embodiments in which less
than full functionality is employed includes saving the cost of
power transistors and associated control logic. Likewise, it may
not be desirable for every node to include the functionality
previously described. It may depend, for example, on the particular
devices or systems coupled to the power bus. For example, some
nodes may comprise "smart" devices or systems, while some may
comprise "dumb" devices or systems. For example, the power bus may
be employed to couple a camera to a PC. Typically, a camera may not
be utilized as a cable power source, and therefore, the expense of
a configurable power distribution circuit may not be justified.
Alternatively, of course, a PC may typically include a variety of
operational states and including an embodiment of a configurable
power distribution circuit in accordance with the invention for a
PC node may be desirable.
[0029] This particular embodiment is adequate to provide support
for software control of all power configuration needs for a power
bus complying with the 1394 specification. This configuration
capability is particularly advantageous in mobile platform
implementations of the 1394 specification, so that a notebook
computer may switch between internal battery power, an alternating
current (AC) power "brick", or cable power. Devices may couple to
or decouple from the power bus at any time where this particular
embodiment or alternative embodiments are employed. Likewise, a mix
of bus-powered and self-powered devices may be coupled to the power
bus.
[0030] FIG. 3 is a block diagram illustrating an embodiment of two
nodes of a network employing the embodiment of FIG. 1. This
particular embodiment illustrates two nodes coupled to a power bus
that is divided or electrically isolated into three power bus
segments. As illustrated in FIG. 3, node 310 includes physical
layer 330 which is powered by node internal power source 340.
Likewise, link layer 350 for node 310 is powered by internal power
source 340. Internal power node source 340 is also providing power
to bus power segments 374 and 376. In contrast, physical layer 360
for node 370 is powered from power bus segment 376 (and, therefore
from node 310's internal power source under the prescribed switch
settings). Link layer 380 of node 320 is powered from segment 377.
Furthermore, the node internal power source of node 320 is inactive
or not providing power and power bus segment 376 is electrically
isolated from segment 377. Segment 375 is configured to be
electrically isolated from the power bus.
[0031] Although the previous embodiments have been described in
connection with the 1394 specification, any cable power
distribution system may make use of an embodiment of the invention.
For example, an embodiment of the invention may be employed in
connection with the Universal Serial Bus (USB) specification,
available from the Universal Serial Bus-Implementers Forum, 2111
N.E. 25th Ave., MS JF2-51, Hillsboro, Oreg. 97124. Likewise, one
embodiment of the invention may be employed for use with a variety
of different serial bus powering systems, including those compliant
with different specifications, such as USB or 1394. Furthermore,
this power distribution scheme may also be used with parallel
buses. As the previous embodiments and discussion illustrates, an
embodiment of a configurable power distribution circuit in
accordance with the invention provides a power distribution
capability and this capability is independent of the parallel or
serial signaling nature of the bus.
[0032] FIG. 5 is a circuit diagram illustrating an embodiment 500
of a configurable power distribution circuit in accordance with the
invention coupled to a generalized node 510. The diagram also
indicates the flow of power and the electrical coupling
relationships, such as between bus segments 520, 530, and 540. FIG.
6 alternatively is a schematic diagram depicting in a conceptual
fashion the power source selection and associated relationships for
a particular node. As illustrated, a particular node may select
either an internal source for power or external source for power,
depicted by power source selection 610. Likewise, either of these
power sources may be obtained via a power source selection made
between a variety of bus segments for the selection of an external
source, as for 620, or made between a variety of internal power
sources for the selection of an internal source, as for 630.
[0033] An embodiment of a configurable power distribution circuit
in accordance with the invention, such as previously described, may
be employed to implement an embodiment of a method for distributing
power in accordance with the invention as follows. In this
embodiment, power is distributed among a plurality of nodes.
Portions of the power bus may be electrically isolated into power
bus segments, such as at least two segments, such as by using an
embodiment previously described, for example. Of course, more than
two power bus segments may also be employed. Then, particular sets
of power sink/source relationships among the nodes may be
configured. In this embodiment, the particular nodes may be coupled
to the respective power bus segments previously described, for
example. Although the invention is not limited in scope to being
employed in connection with the 1394 specification or a 1394
specification compliant bus or node, where a 1394 specification
compliant bus or node is employed, each node comprises at least a
physical layer and a link layer, as previously described.
Furthermore, as previously described and illustrated, in
embodiments of a configurable power distribution circuit in
accordance with the present invention, the particular sets of power
sink/source relationships among the nodes includes relationships
that vary over time or are "time varying". In this particular
embodiment, a particular set of power sink/source relationships
among the nodes are configured by applying externally derived
electrical signals to an electrically configurable physical
arrangement of power transistors, such as-previously described. The
externally derived electrical signals may, for example, be provided
by a personal computer operating in accordance with software loaded
on the computer that provides the desired electrical signals to
configure the physical arrangement of power transistors as desired.
Of course, the invention is not limited in scope in this
respect.
[0034] In another embodiment of a method of distributing power in
accordance with the present invention, a plurality of nodes coupled
via a plurality of power bus segments may be configured to provide
at least one particular set of power sink/source relationships
among the coupled nodes. Therefore, in this embodiment, there may
be one particular set of power sink/source relationships. Likewise,
there may also be another particular set of power sink/source
relationships other than this one particular set of power
sink/source relationships. For example, the two sets of particular
source/sink relationships may be electrically isolated and formed
power bus segments, such as previously described.
[0035] While certain features of the invention have been
illustrated and described herein, many modifications,
substitutions, changes and equivalents will now occur to those
skilled in the art. It is, therefore, to be understood that the
appended claims are intended to cover all such modifications and
changes as fall within the true spirit of the invention.
* * * * *