U.S. patent application number 11/563349 was filed with the patent office on 2008-05-29 for method and system for detecting transformer saturation in a communication interface.
Invention is credited to Neven Pischl.
Application Number | 20080122448 11/563349 |
Document ID | / |
Family ID | 39493166 |
Filed Date | 2008-05-29 |
United States Patent
Application |
20080122448 |
Kind Code |
A1 |
Pischl; Neven |
May 29, 2008 |
Method and System for Detecting Transformer Saturation in a
Communication Interface
Abstract
A method and system for detecting transformer saturation in a
communication interface is provided. The method may include
detecting a change in impedance resulting from transformer
saturation of at least one isolation transformer utilized in a
network path of a network. The network may conform to an IEEE
802.3af specification where power may be delivered through the
network. The method may further comprise generating a pulse at a
one end of the network and measuring a reflection at that end to
detect the transformer saturation. In response to the impedance
change, a transmitter signal may be pre-distorted in order to
compensate for the detected transformer saturation, or the power
delivered over the network may be disabled.
Inventors: |
Pischl; Neven; (Santa Clara,
CA) |
Correspondence
Address: |
MCANDREWS HELD & MALLOY, LTD
500 WEST MADISON STREET, SUITE 3400
CHICAGO
IL
60661
US
|
Family ID: |
39493166 |
Appl. No.: |
11/563349 |
Filed: |
November 27, 2006 |
Current U.S.
Class: |
324/600 |
Current CPC
Class: |
G01R 27/06 20130101;
H04L 25/0266 20130101; H03F 3/24 20130101; H04B 1/0475 20130101;
H04L 25/0288 20130101; H04B 2001/0408 20130101 |
Class at
Publication: |
324/600 |
International
Class: |
G01R 29/00 20060101
G01R029/00 |
Claims
1. A method for processing signals in a communication system, the
method comprising: detecting a change in impedance resulting from
transformer saturation of at least one transformer utilized in a
network path of a network.
2. The method according to claim 1, comprising generating at least
one pulse at a first end of said network path and measuring at
least one reflection at said first end.
3. The method according to claim 1, comprising pre-distorting a
signal in response to said detecting.
4. The method according to claim 1, comprising delivering power
through said network path via said at least one transformer.
5. The method according to claim 4, comprising disabling said
delivered power in response to said detecting.
6. The method according to claim 1, wherein said at least one
transformer is an isolation transformer.
7. The method according to claim 1, wherein said impedance change
is related to a saturation level of said transformer.
8. The method according to claim 1, wherein said network conforms
to an IEEE 802.3af specification.
9. The method according to claim 1, comprising generating a signal
to compensate for said transformer saturation upon said
detecting.
10. A machine-readable storage having stored thereon, a computer
program having at least one code section for processing signals in
a communication system, the at least one code section being
executable by a machine for causing the machine to perform steps
comprising: detecting a change in impedance resulting from
transformer saturation of at least one transformer utilized in a
network path of a network.
11. The machine-readable storage according to claim 10, wherein
said at least one code section comprises code that enables
generating at least one pulse at a first end of said network path
and measuring at least one reflection at said first end.
12. The machine-readable storage according to claim 10, wherein
said at least one code section comprises code that enables
pre-distorting a signal in response to said detecting.
13. The machine-readable storage according to claim 10, wherein
said at least one code section comprises code that enables
delivering power through said network path via said at least one
transformer.
14. The machine-readable storage according to claim 13, wherein
said at least one code section comprises code that enables
disabling said delivered power in response to said detecting.
15. The machine-readable storage according to claim 10, wherein
said at least one transformer is an isolation transformer.
16. The machine-readable storage according to claim 10, wherein
said impedance change is related to a saturation level of said
transformer.
17. The machine-readable storage according to claim 10, wherein
said network conforms to an IEEE 802.3af specification.
18. The machine-readable storage according to claim 10, wherein
said at least one code section comprises code that enables
generating a signal to compensate for said transformer saturation
upon said detecting.
19. A system for processing signals in a communication system, the
system comprising: one or more circuits that enables detecting a
change in impedance resulting from transformer saturation of at
least one transformer utilized in a network path of a network.
20. The system according to claim 19, wherein said one or more
circuits enables generating at least one pulse at a first end of
said network path and measuring at least one reflection at said
first end.
21. The system according to claim 19, wherein said one or more
circuits enables pre-distorting a signal in response to said
detecting.
22. The system according to claim 19, wherein said one or more
circuits enables delivering power through said network path via
said at least one transformer.
23. The system according to claim 22, wherein said one or more
circuits enables disabling said delivered power in response to said
detecting.
24. The system according to claim 19, wherein said at least one
transformer is an isolation transformer.
25. The system according to claim 19, wherein said impedance change
is related to a saturation level of said transformer.
26. The system according to claim 19, wherein said network conforms
to an IEEE 802.3af specification.
27. The system according to claim 19, wherein said one or more
circuits enables generating a signal to compensate for said
transformer saturation upon said detecting.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS/INCORPORATION BY
REFERENCE
[0001] Not Applicable.
FIELD OF THE INVENTION
[0002] Certain embodiments of the invention relate to network
communication systems. More specifically, certain embodiments of
the invention relate to a method and system for detecting
transformer saturation in a communication interface.
BACKGROUND OF THE INVENTION
[0003] Computer networks are continually being enhanced to improve
the ways in which people communicate. For example, the Internet has
enabled people to gain access to vast amounts of information.
Besides the Internet, networks are utilized to facilitate the
transfer of files between computers as well as to connect computers
to printers, scanners, cameras and a whole host of other devices.
The physical characteristics of the network can take on many
different characteristics. For example, the actual connections may
be made through coax or twisted pair cables. Routers and hubs may
be utilized to connect multiple computers to one another and to
direct network traffic. The protocol utilized by the network may
vary. For example, the protocol may be TCP/IP, IPX/SPX, or
AppleTalk.
[0004] Although most often thought of as a means for computers to
communicate with one another, networks are now being utilized for
other forms of communications. For example, in a security system,
security cameras may communicate to a server computer via an IP
network rather than stream analog video information over a video
cable. This may make it easier to add security systems where an IP
network already exists. Furthermore, in a networking environment,
the computer and camera could be a great distance apart whereas the
distance may be much shorter if the analog video were transferred
directly over a cable.
[0005] Some network systems allow for the transfer of power over
the network cable, by coupling DC voltages and currents to the
conductors. For example, one way to transfer power may be to
utilize unused conductors in the network cable. Another method may
be to transfer the power utilizing the same conductors, but
superimposing the power by utilizing isolation transformers. The
second method may conform to IEEE 802.3af. This method may work
well for most situations. However, under certain conditions the
characteristics of the transformers may change and thus impede the
transfer of data.
[0006] Further limitations and disadvantages of conventional and
traditional approaches will become apparent to one of skill in the
art, through comparison of such systems with some aspects of the
present invention as set forth in the remainder of the present
application with reference to the drawings.
BRIEF SUMMARY OF THE INVENTION
[0007] A system and/or method is provided for detecting transformer
saturation in a communication interface substantially as shown in
and/or described in connection with at least one of the figures, as
set forth more completely in the claims.
[0008] These and other advantages, aspects and novel features of
the present invention, as well as details of an illustrated
embodiment thereof, will be more fully understood from the
following description and drawings.
BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS
[0009] FIG. 1 is a block diagram of an exemplary arrangement for
distributing power over an Ethernet connection, which may be
utilized in connection with an embodiment of the invention.
[0010] FIG. 2A is a block diagram of an exemplary circuit for
communicating data via a transformer where the transformer is also
utilized for power distribution, which may be utilized in
connection with an embodiment of the invention.
[0011] FIG. 2B is an exemplary graph of a hysteresis curve for a
transformer, which may be utilized in connection with an embodiment
of the invention.
[0012] FIG. 3 is an exemplary system for detecting faults in a
network cable, in connection with an embodiment of the
invention.
[0013] FIG. 4 is a block diagram of an exemplary arrangement for
detecting transformer saturation in a communications interface, in
accordance with an embodiment of the invention.
[0014] FIG. 5 is a block diagram of an exemplary flow diagram for
detecting transformer saturation, in accordance with an embodiment
of the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0015] Certain embodiments of the invention may be found in a
method and system for detecting transformer saturation in a
communication interface. The method may include detecting a change
in impedance resulting from transformer saturation of at least one
isolation transformer utilized in a network path of a network. The
network may conform to an IEEE 802.3af specification where power
may be delivered through the network. The method may further
comprise generating a pulse at a one end of the network and
measuring a reflection at that end to detect the transformer
saturation. In response to the impedance change, a transmitter
signal may be pre-distorted in order to compensate for the detected
transformer saturation, or the power delivered over the network may
be disabled.
[0016] FIG. 1 is a block diagram of an exemplary arrangement for
distributing power over an Ethernet connection, which may be
utilized in connection with an embodiment of the invention.
Referring to FIG. 1, there is shown a computer 100, a router 101,
and two cameras 102. The computer 100 may comprise suitable logic,
circuitry, and/or code that may enable communicating data over a
network connection. For example, the computer 100 may comprise a
network card and the network card may communicate utilizing an
Ethernet standard, such as IEEE 802.3a. The network card may
comprise suitable logic, circuitry, and/or code that may enable
sending power over the same Ethernet connection. For example, the
Ethernet connection may conform to IEEE 802.af. In this regard, the
physical network connection may comprise a category 5 cable. This
cable may, for example, have a total of 8 conductors or 4 twisted
pair conductors. Two of the twisted pair conductors may be utilized
for data communication and the other two may be unused. In some
embodiments the unused conductors may, for example, be utilized to
transfer power. In this regard, an output voltage of the power
supply may be 48 volts DC. In other embodiments, the power may be
distributed over the data lines.
[0017] The router 101 may comprise suitable logic, circuitry,
and/or code that may enable routing data between a plurality of
devices. For example, the router 101 may route data packets from
the computer 100 to various end devices, such as the cameras 102
shown in FIG. 1. In this regard, the connection between the
computer 100 and the router 101 and the router 101 and the cameras
may be an Ethernet connection as described above. To facilitate
data transfers, the router 101 may require a power source. The
router 101 may, for example, receive power from a power adapter
plugged into a wall. The router 101 may also be capable of
utilizing power transferred from the network card in the computer
100 and may be capable of outputting power for end devices, such as
the cameras 102 shown in FIG. 1.
[0018] The cameras 102 may comprise suitable logic, circuitry,
and/or code that may enable capturing images and transferring those
images over an Ethernet connection. In this regard the cameras 102
may be coupled to the router 101. The cameras 102 may be capable of
operating from power delivered over the Ethernet connection. In
this regard, the cameras 102 may comprise additional logic,
circuitry, and or code that may enable converting the power
delivered over the Ethernet into voltages more suitable for
powering each of the cameras 102 during operation.
[0019] FIG. 2A is a block diagram of an exemplary circuit for
communicating data via a transformer where the transformer is also
utilized for power distribution, which may be utilized in
connection with an embodiment of the invention. Referring to FIG.
2A, there is shown a data TX 200, a transformer 201, a data RX 203,
a magnetic flux (H) within the transformer core 202, and a DC
source 204.
[0020] FIG. 2B is an exemplary graph of a hysteresis curve for a
transformer, which may be utilized in connection with an embodiment
of the invention. The central area of the curve may correspond to
the "linear region" of the transformer 201. H 202 may be
proportional to the current in the transformer winding.
[0021] In operation, it may be necessary that the transformer 201
operate in the linear region. That is, it may be necessary that the
signal-current operating point is around "zero" and that the
maximum amplitude of the signal-current does not reach the area of
saturation. When this is the case, the output signal on the
secondary of the transformer 201 going to the data RX 203 may be
linearly proportional to the TX signal from the data TX 200.
[0022] If the signal-current reaches into the saturation area,
distortions may occur, and transmission may not work properly. This
may, for example, happen when the signal current-amplitude is too
large. That is, this could occur even without a DC bias from the DC
source 204 when the signal amplitude is too large. This may also
occur, when the operating point of the transformer 201 is moved
toward or into the saturation area by applying a DC-current to the
transformer winding from the DC source 204. A DC bias superimposed
on one of the data-windings may also move the operating point of
the transformer 201 toward saturation area, possible resulting in a
distorted signal at the output of the transformer 201.
[0023] FIG. 3 is an exemplary system for detecting faults in a
network cable, in connection with an embodiment of the invention.
Referring to FIG. 3, there is shown a TDR (time domain
reflectometer) 300, a network cable 302, and an interface 301. The
TDR 300 may work on the same principle as radar. A pulse of energy
may be transmitted down a network cable 302. When that pulse
reaches the end of the network cable 302, or a fault along the
cable, part or all of the pulse energy may be reflected back to the
TDR 300. The TDR 300 may measure the amount of time it takes for
the signal to travel down the network cable 302, reflect off an
impedance discontinuity, and reflect back. It may also compare the
waveform of the launched pulse and the received reflection. The TDR
300 may then convert this time to distance, as well as the
reflected waveform, and display the information as a location and
magnitude and type of impedance (real, capacitive, inductive)
discontinuity along the network cable 302.
[0024] A TDR 300 may measure a change in impedance, which may be
caused by a variety of reasons. For example, the change in
impedance may be related to network cable 302 damage, change in
cable type, or improper installation. The change in impedance may
also be the result of defective manufacturing. In this regard, the
impedance of the cable may be determined by the spacing of the
conductors from each other and the type of dielectric utilized. If
the conductors are manufactured with exact spacing and the
dielectric is, for example, exactly constant, the cable impedance
may be constant. The cable impedance may vary along the line if,
for example, the conductors are kinked, the spacing between the
conductors is changed, or a component with improper impedance is
connected anywhere along the line.
[0025] The TDR 300 may operate by sending electrical pulses down
the cable and sampling the reflected energy. Any impedance change
may cause some energy to reflect back toward the TDR 300 and may be
displayed on the TDR 300. The characteristics of the reflected
signal may be utilized to determine the amount of change in
impedance.
[0026] FIG. 4 is a block diagram of an exemplary arrangement for
detecting transformer saturation in a communications interface, in
accordance with an embodiment of the invention. Referring to FIG.
4, there is shown a power sourcing device (PSD) 400, a network
cable 406, and a powered device (PD) 409. Referring to the PSD,
there is shown a PSD transmitter 405, a PSD receiver 408, an
isolation transformer 402, a power supply 410, and a TDR 401.
Referring to the PD 400, there is shown a PD transmitter 404, a PD
receiver 407, and a DC/DC converter 411.
[0027] The PSD 400 may comprise suitable logic, circuitry, and or
code that may enable communication of data over an interface as
well as delivering power over the same interface. For example, the
PSD 400 may be a network interface card (NIC) in a computer 100
(FIG. 1). The PSD transmitter 405 may comprise suitable logic,
circuitry, and/or code that may enable conversion of data to a
suitable transmission format so that it may be transferred long
distances. For example, a computer 100 may input data bits into the
PSD transmitter 405 and the PSD transmitter 405 may output a
differential voltage corresponding to the data bits. The PSD
receiver 408 may comprise suitable logic, circuitry, and/or code
that may enable converting data communicated from a remote
transmitter back into a format suitable for a computer. The PSD
transmitter 405 and PSD receiver 408 may be coupled to the PSD
isolation transformers 402.
[0028] The PSD isolation transformers 402 and the PD isolation
transformers 403 may comprise several windings and a core that may
enable isolation of DC voltages that may be present on the primary
and secondary. The isolation transformers 402 may have
characteristics similar to the transformer shown in FIG. 2A. The
windings of the isolation transformers 402 may be center tapped. In
the PSD 400, the center taps may be coupled to the DC power supply
410. In the PD 409, the center taps may be coupled to the DC/DC
converter 411. The other taps may be coupled to the network cable
406.
[0029] The network cable 406 may comprise several conductors that
may enable communication of data as well as delivery of power. The
network cable 406 may correspond to a category 5 cable. In this
regard, the network cable 406 may comprise 4 sets of twisted pair
cables. Two of the twisted pair cables may be utilized to
communicate data between, for example, the PSD 400 and the PD 409.
The same twisted pair cables may also be utilized to deliver power
from the PSD 400 to the PD 409. The ends of the network cable 406
may be coupled to the isolation transformers 402 in the PSD 400 and
the isolation transformers 403 in the PD 409.
[0030] The PD transmitter 404 may comprise suitable logic,
circuitry, and/or code that may enable conversion of data to a
suitable transmission format so that it may be transferred over
long distances. For example, a computer may input data bits into
the PD transmitter 404 and the PD transmitter 404 may output a
differential voltage corresponding to the data bits. The PD
receiver 407 may comprise suitable logic, circuitry, and/or code
that may enable converting data communicated from a remote
transmitter back into a format suitable for a computer. The PD
transmitter 404 and PD receiver 407 may be coupled to the PSD
isolation transformers 403.
[0031] The power supply 410 may comprise suitable logic, circuitry,
and/or code that may enable the generation of power to power a
remote device. In this regard, the power supply 410 may generate,
for example, 48 volts. The power supply 410 may be coupled to the
center taps on the secondaries of the PSD isolation transformers
402 in the PSD 400.
[0032] The DC/DC converter 411 may comprise suitable logic,
circuitry, and/or code that may enable the conversion of voltage
from one DC voltage to another DC voltage. In this regard, the
DC/DC converter 411 may input 48 volts and may output a voltage
sufficient to power the PD 409. For example, the output of the
DC/DC converter 411 may be 5 volts or 12 volts. The output may also
be greater than the input voltage. The DC/DC converter 411 may be
coupled to the center taps on the secondaries of the PSD isolation
transformers 403 in the PD 409.
[0033] The TDR 401 may comprise suitable logic, circuitry, and/or
code that may enable the detection of faults in a communication
path. In this regard, the TDR 401 may correspond to the TDR shown
in FIG. 3. The TDR 401 may reside within the PSD 400 and may be
coupled to the primary side of the PSD isolation transformers 402.
The TDR may transmit a pulse through the PSD isolation transformers
402 and measure the reflections caused by changes in impedance
between the PSD 400 and the PD 400. In this regard, the TDR may be
capable of detecting changes in the impedance of the isolation
transformers 402 and 403 as well as defects in the network cable
406 or whether or a component with improper impedance is connected
anywhere along the line.
[0034] In operation, the power supply 410 in the PSD 400 may be
utilized to supply power to a PD 409. The power may be transferred
via the same twisted pair cables utilized for communication between
the PSD 400 and the PD 409. The power may be superimposed on the
communication signals by inserting the power into the center taps
on the secondaries of the PSD isolation transformers 402. As a
result, the signals traveling over the twisted pair may take on a
DC bias equal to the power supply 410 voltage. This DC bias may be
removed by PD isolation transformers 403.
[0035] In certain instances, DC current through the transformer may
cause the transformer core to saturate by, for example, the
mechanism shown FIG. 2A and FIG. 2B. This may happen even if the
level of the DC current is within the operating specification for
the PSD 400 and PD 409. It may depend on the transformer, contact
resistance of the connector utilized and resistance of the
conductors in the cable.
[0036] The TDR 401 may be utilized to detect when the transformer
impedance changes. For example, it may be utilized to detect
relative changes in the impedance of the isolation transformers 402
and 403 before and after a DC current has been applied. For
example, the TDR 401 may detect if the DC current is saturating the
core and thus causing an impedance drop, which may have a negative
impact on the quality and possibility of data transmission through
the isolation transformers 402 and 403. It may do this by
generating pulses on either the PSD 400 or PD 409 side of the
isolation transformers 402 and 403 and then measure the reflection
off the isolation transformers 402 and 403. If saturation is
detected then, for example, a CPU may reduce or eliminate the
current delivered to PD or flag an error and/or warning signal that
the data transmission may be affected.
[0037] In another embodiment of the invention, the signal may be
intentionally pre-distorted when, for example, saturation is
detected. For example, the PSD transmitter 405 may pre-distort the
output signals so that when they pass through the saturating
isolation transformers, the signals appear proper at the receiving
end. The PSD transmitter 405 may also be capable of pre-distorting
the signal in proportion to an amount of detected saturation.
[0038] In yet another embodiment of the invention, a TDR 401 may
reside within the PD 409 and be coupled to the primary side of the
isolation transformers 403. This may enable the PD 409 to detected
transformer saturation as well.
[0039] FIG. 5 is a block diagram of an exemplary flow diagram for
detecting transformer saturation, in accordance with an embodiment
of the invention. At step 500, the TDR 401 may generate a pulse so
that reflections may be measured. The optimal pulse characteristics
may depend on the characteristics of the isolation transformers 402
and 403, the location of the transformer relative to the
transceiver and on the characteristics of the interconnects used
for the signal transmission, which may include PCB traces and other
cables that may be utilized. At step 501, the TDR 401 may measure
the reflections and at step 502, the TDR 401 may compare the
measurements to baseline measurements. For example, during initial
setup, the TDR 401 may have measured the impedance of the
connection between the PSD 400 and the PD 409. This measurement may
take into account the impedance of the isolation transformers 402
and 403 as well as the impedance of the network cable 406. The TDR
401 may store this information so that it may be utilized as a
baseline measurement for later measurements.
[0040] At step 503, the TDR 401 may check if the connection between
the PSD 400 and PD 409 matches the base line impedance. If the
values don't match, then one or more of the isolation transformers
402 and 403 may be in saturation. The result of the comparison may
be communicated to a CPU so that the CPU may take appropriate
action.
[0041] If saturation has been detected then, at step 505 the CPU
may shutdown communication and disable the power supply 410. The
CPU may also report an error to the user so that the user may take
care of the problem. In another embodiment of the invention, if
saturation has been detected, then at step 504 the amount of the
impedance mismatch may be determined. Then at step 506, this amount
of mismatch may be utilized to dynamically pre-distort the signals.
The pre-distortion may take place within the PSD transmitter 405.
In this manner PSD 400 may compensate for the saturation.
[0042] Another embodiment of the invention may provide a method for
performing the steps as described herein for detecting transformer
saturation in a communication interface. For example, a change in
the impedance of an isolation transformer 402 utilized in a
network, resulting from transformer saturation may be detected by
generating a pulse at one end of the network and measuring the
reflection that corresponds to the isolation transformer 402. The
network may conform to an IEEE 802.3af specification where power
may be delivered through the network be DC power supply 410. In
response to the impedance change, a transmitter signal may be
pre-distorted by a transmitter 405 in order to compensate for the
detected transformer saturation, or the power delivered over the
network may be disabled.
[0043] Accordingly, the present invention may be realized in
hardware, software, or a combination of hardware and software. The
present invention may be realized in a centralized fashion in at
least one computer system, or in a distributed fashion where
different elements are spread across several interconnected
computer systems. Any kind of computer system or other apparatus
adapted for carrying out the methods described herein is suited. A
typical combination of hardware and software may be a
general-purpose computer system with a computer program that, when
being loaded and executed, controls the computer system such that
it carries out the methods described herein.
[0044] The present invention may also be embedded in a computer
program product, which comprises all the features enabling the
implementation of the methods described herein, and which when
loaded in a computer system is able to carry out these methods.
Computer program in the present context means any expression, in
any language, code or notation, of a set of instructions intended
to cause a system having an information processing capability to
perform a particular function either directly or after either or
both of the following: a) conversion to another language, code or
notation; b) reproduction in a different material form.
[0045] While the present invention has been described with
reference to certain embodiments, it will be understood by those
skilled in the art that various changes may be made and equivalents
may be substituted without departing from the scope of the present
invention. In addition, many modifications may be made to adapt a
particular situation or material to the teachings of the present
invention without departing from its scope. Therefore, it is
intended that the present invention not be limited to the
particular embodiment disclosed, but that the present invention
will include all embodiments falling within the scope of the
appended claims.
* * * * *