United States Patent
`
`[19]
`
`[ii] Patent Number:
`
`6,115,468
`
`De Nicole
`
`[45] Date of Patent:
`
`Sep. 5, 2000
`
`US006l15468A
`
`54]
`
`P()W’ER FEED FOR ETHERNET
`TELEPHONES VIA ETHERNET LINK
`
`................ .. 375/204
`5,574,748 11/1996 Vander Mey et al.
`. . . .. 375/258
`5,799,040
`8/1998 Lau . . . . .. . ... . .. . . ..
`5,994,998 11/1999 Fisher et al.
`................... 340/310.01
`
`75]
`
`Inventor: Maurilio Tazio De Nicolo, Saratoga,
`Calm
`
`Assignee: Cisco Technology, Inc., San Jose, Calif.
`
`Pm-mary EXa,m~m,,_DaVid R. Hudspelh
`Assistant ExamiIter—Vijay B Cliawaii
`Attorney, Agent, or Firm—D’Alessandro & Ritchie
`[57]
`ABSTRACT
`
`APPL NO‘: 09/0489922
`Filed.
`Man 26’ 1998
`
`_
`Int Cl-’
`U.S. Cl.
`
`..................................................... .. H043 3/00
`................. ..
`379/413; 379/412; 379/900;
`379/324; 375/258; 375/257; 375/285
`Field of Search ................................... ., 379/413, 412,
`379/900, 324; 375/285, 257, 258
`
`References Cited
`
`497239257
`5,285,477
`5,311,518
`5,541,957
`
`................. N
`
`379/93
`2/1933 Jones at 31.
`375/258
`2/1994 Leonowich
`370/1101
`5/1994 Takato et 211.
`7/1996 Lau ....................................... .. 375/258
`
`_
`
`+
`—
`OUT
`
`+
`—
`OUT
`
`An Ethernet device power transmission system includes an
`input
`transformer, an output. transformer and ‘a pair of
`twisted pair conductors. The input transformer includes a
`pair of primaries for connection to a source of Ethernet data.
`The input transformer also includes a pair of secondaries,
`each having a center-tap. A first twisted pair conductor is
`connected across the first secondary, a second twisted pair
`conductor is connected across the second secondary and a
`DC—bias is provided between the respective center taps of
`the first and second secondaries. At the local end, the output
`:;:::?:;:::Ig;:1:;':::.§;:‘.::;'.:r.:i;“;.°::;:.:::’:‘::'::::.
`load device. The first and second primary center taps are
`connected to a power processor for extraction of DC power.
`
`17 Claims, 3 Drawing Sheets
`
`POWER
`POWER
`PROCESSOR T PROCESSOR T PROCESSOR
`
`;tN
`
`IIN
`
`SUPPLY
`
`Aerohive - Exhibit 1019
`
`

`
`U.S. Patent
`
`Sep. 5, 2000
`
`Sheet 1 of3
`
`6,115,468
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`FIG.1(PRIORART)
`
`POWERPROCESSOR
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`
`
`PROCESSORPROCESSOR
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`PHONEDATA3PHONEDATA2
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`

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`U.S. Patent
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`p..eS
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`00025:
`
`Sheet 2 of 3
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`6,115,468
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`

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`U.S. Patent
`
`Sep.5,2000
`
`3f034|.6EhS
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`6,115,468
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`mm>2a
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`kamsm
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`H+
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`6,115,468
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`1
`POWER FEED FOR ETHERNET
`TELEPI-IONES VIA ETHERNET LINK
`
`BACKGROUND OF THE INVENTION
`
`.
`
`l. Field of the Invention
`
`The present invention is directed to a method and appa-
`ratus which provide electrical power to ethernet—based tele-
`phones over an ethernet wire link.
`2. The Background Art
`Telephones require electrical power in order to operate.
`The power can be delivered over the telephone lines or via
`a separate power connection,
`typically through a power
`transformer connected to the electrical power grid. Tele-
`phones powered in the latter fashion will be inoperable
`during a power failure unless provision is made both locally
`at the telephone and at the PBX or local telephone switch for
`emergency power to be supplied. While it
`is normal to
`provide an uninterruptible power supply to an office’s PBX
`or telephone switch, it is not desirable for cost and other
`reasons to provide electrical power back up systems to each
`telephone location.
`In the past,
`the power problem was
`frequently solved by using an 8-wire telephone connection
`to the telephone switch. With 8 wires there is more than
`enough capability for analog audio digital and power con-
`nections to the telephone switch.
`The growth of the Internet and similar local and wide area
`networks based on Ethernet technology has created a poten-
`ial market for telephone systems which would connect
`directly to existing Ethernet connections. The Ethernet
`rotocol, however, does not provide a mechanism for pow-
`ering such telephones. A typical Ethernet connection to an
`office location would include a pair of unshielded twisted
`aair (UTP) lines for a total of four conductors—one pair for
`ransmit, one for receive. The transmit pair is dedicated to
`send packets of data over the Ethernet connection;
`the
`receive pair receives packets of data over the Ethernet
`connection. Simply placing a DC bias on two or more of
`hese conductors and using the bias to power a local Ethernet
`elephone is risky because the bias is not part of the Ethernet
`arotocol and might damage Ethernet compliant equipment
`not designed to handle such a bias.
`Turning to FIGS. 1 and 2, a prior art scheme for providing
`aower over a single twisted pair connection is shown. In the
`wrior art, system 10 and power supply 11 provides DC power
`over lines 12 (positive lead) and 14 (negative lead) to a
`series of ports on the network. Filter capacitor 16 and filter
`inductors 18 and 20 are preferably provided to insure a clean
`source of DC power and to avoid AC cross-talk between the
`network and the power supply. Each port 22, 24 and 26 of
`the network is coupled to a twisted pair link 28, 30 and 32,
`respectively, via a transformer, 34, 36, and 38, respectively.
`Transformer 34, for example, operates as follows: Data on
`port 1 (22) is applied to the primary 40 of transformer 34 and
`coupled to a pair of secondary winding 42, 44 of transformer
`34 through transformer core 46 in a conventional manner.
`One end 48 of secondary winding 42 is connected to twisted
`pair 28 and the other end 50 of secondary winding 42 is
`connected to the positive lead 12 of power supply 11. One
`end 52 of secondary Winding 44 is connected to twisted pair
`link 28 and the other end 54 of secondary winding 44 is
`connected to the negative lead 14 of power supply 11. Leads
`50 and 54 are AC-coupled to one another with capacitor 56
`as shown. This blocks DC current from flowing and allows
`a DC bias to be established over the two conductors of
`twisted pair link 28 while simultaneously allowing the flow
`of data over the li11k.
`
`2
`the telephone end of the twisted-pair link 28, a
`At
`similarly structured transformer 58 receives the data signal
`as well as the DC bias. First primary 60 and second primary
`62 are AC-coupled with capacitor 64 so as to be able to
`couple data signals from twisted-pair link 28 with trans-
`former 58 while holding off a DC bias. The DC bias of
`twisted-pair link 28 is applied to a power processor 66 and
`from there provides to local equipment to be powered by the
`twisted pair system. A typical embodiment of a power
`processor 66 is shown in FIG. 2. It comprises a filter 68, a
`rectifier 70, a filter capacitor 72 and a DC-DC converter 74.
`While lit for its intended purpose, the above-described
`system has some drawbacks which make it a less than ideal
`choice for an Ethernet environment. For example, each
`secondary 42 and 44 of transformer 34 and each primary 60
`and 62 of transformer 58 will experience a net current flow
`equal to the total amount of current drawn by the load at the
`distal end of the twisted-pair link. This current will affect the
`choice of transformer core size at each end of the link and
`will affect the choice of wire gauge used for the link.
`It would be desirable to provide an improved method and
`apparatus for powering Ethernet telephones over a 4-wire
`link. Such a system would be able to take advantage of
`existing wiring without the need to rewire the premises to
`install such devices. Furthermore, by providing power over
`the Ethernet connection, power transformers are not
`required at the device location, and a central uninterruptible
`power supply is made possible to provide power to the entire
`telephone system in case of a power failure.
`SUMMARY OF THE INVENTION
`
`An Ethernet device power transmission system provides
`electrical power to devices such as Ethernet telephones and
`related equipment over a 4-wire Ethernet connection without
`any need for rewiring premises having an existing 4-wire
`Ethernet system. The system eliminates any requirement for
`local power such as transformers to power such equipment
`as all power can be provided over the existing Ethernet
`wiring. A central uninterruptible power supply (UPS) is
`thereby made possible to provide back-up power to all such
`equipment. The system includes an input transformer, an
`output transformer and a pair of twisted pair conductors. The
`input transformer includes a pair of primaries for connection
`to a source of Ethernet data. The input transformer also
`includes a pair of secondaries, each having a center—tap. A
`first twisted pair conductor is connected across the first
`secondary, a second twisted pair conductor is connected
`across the second secondary and a DC-bias is provided
`between the respective center taps of the first and second
`secondaries. At
`the local end,
`the output
`transformer
`includes a first and second center-tapped primary and a first
`and second secondary for connection to the load device. The
`first and second primary center taps are connected to a power
`processor for extraction of DC power.
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`FIG. 1 is an electrical schematic diagram of a prior art
`telephone power distribution system for use over a two-wire
`twisted pair system.
`FIG. 2 is a11 electrical schematic diagram of a prior art
`telephone power extraction system or power processor.
`FIG. 3 is an electrical schematic diagram of an Ethernet
`telephone power distribution system according to a presently
`preferred embodiment of the present invention.
`DESCRIPTION OF THE PREFERRED
`EMBODIMENTS
`
`Those of ordinary skill in the art will realize that the
`following description of the present invention is illustrative
`
`

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`6,115,468
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`only and is not intended to be in any way limiting. Other
`embodiments of the invention will readily suggest them-
`selves to such skilled persons from an examination of the
`within disclosure.
`
`Turning now to FIG. 3, in accordance with a presently
`preferred embodiment of the present invention, a system
`including a plurality of data ports 80, 82, 84 is provided to
`transmit data on lines 86, 88, 90, 92, 94, 96 to and from load
`devices 1 (98), 2 (100) and 3 (102). Load devices 98, 100
`and 102 may be Ethernet telephones and/or other Ethernet
`devices requiring power to be transmitted to them in addi-
`tion to data over Ethernet twisted pair lines.
`Turning to Port 1 (80) as an example, data on lines 88 and
`86 is provided to transmitter 104 and from receiver 106,
`respectively. Transmitter 104 drives twisted pair 108.
`Receiver 106 receives from twistee pair 110. First trans-
`former 112 includes a first primary 114 and a second primary
`116. First primary 114 is connected o twisted pair 108 and
`second primary 116 is connected to twisted pair 110.
`At load 98 a similar arrangement exists. Second trans-
`former 118 includes a first secondary 120 and a second
`secondary 122. These are respective y connected to twisted
`pairs 124 and 126 which are,
`in turn, connected through
`receiver 125 and transmitter 127 to load device 98.
`
`Ethernet link 128 couples first and second secondaries
`130, 132 of first transformer 112 to irst and second prima-
`ries 134, 136 of second transformer 118. Ethernet link 128
`preferably comprises a pair of twisted pair conductors 128a
`and 12817 wherein twisted pair 128a connects first secondary
`130 to first primary 134 of the twis ed pair 128b connects
`second secondary B2 to several primary 136.
`Power coupling is provided as fo lows. Secondaries 130
`and 132 of first transformer 112 each include a center tap,
`138, 140 respectively. Center tap 138 is connected to the
`positive lead 142 of a power supply 144 and center tap 140
`is connected to the negative lead 146 of power supply 144
`which may preferably be an uninterruptible power supply
`(UPS). DC filtering components 1480, 14817, 148C may be
`provided as well known to those of ordinary skill in the art.
`Now the entire loop of twisted pair 128:; is at the potential
`of positive lead 142 while the entire loop of twisted pair
`128b is at
`the potential of negative lead 146. A power
`processor 149, as in FIG. 2, may preferably be attached to
`center taps 150, 152, respectively, of first and second pri-
`maries 134 and 136 of second transformer 118 so as to
`provide a DC power source to power processor 149. Power
`processor 149 performs any DC—DC power conversion and
`filtering required and provides power over leads 154, 156 to
`load 98 which may be an Ethernet telephone or other device.
`The present invention provides a number of advantages
`over the prior art. First, power delivered to the load device
`is split equally over four wires rather than two reducing the
`current carrying requirements of all four wires over a two
`wire system delivering the same amount of power. Second,
`because the transmitted power is applied at and removed at
`center taps, there is no net current flow due to the DC bias
`through either primary or secondary of each respective
`twisted pair 128:1, 128b. This reduces the size requirements
`for the transformer 112, 118 core over a system with a net
`current, as in the system of FIG. 1. This permits off—the—shelf
`transformers for Ethernet applications to be used maintain-
`ing compatibility with Ethernet systems not having this
`power delivery requirement. Note that if the prior art system
`of FIG. 1 were used with a load device lacking decoupling
`between the two primaries on the network side of the
`transformer, the power supply would be effectively shorted.
`
`4
`In the system according to FIG. 3, as long as the separate
`data channels are not shorted (which would not normally
`occur), any interface can be used on the load side of the
`network—whether it makes use of the power available there
`or not.
`Alternative Embodiments
`Although illustrative presently preferred embodiments
`and applications of this invention are shown and described
`herein, many variations and modifications are possible
`which remain within the concept, scope, and spirit of the
`invention, and these variations would become clear to those
`of skill
`in the art after perusal of this application.
`In
`particular, the use of the term primary and secondary in
`referring to transformer windings herein is for explanation
`only. As the links are bi-directional, the terms primary and
`secondary may be interchanged as would be known to those
`of ordinary skill in the art. The invention, therefore, is not to
`be limited except in the spirit of the appended claims.
`What is claimed is:
`1. A power feed system for Ethernet telephones, said
`system comprising:
`a first
`transformer including a first primary, a second
`primary, a first secondary with a first center—tap and a
`second secondary with a second center—tap, said first
`primary for coupling to a first pair of conductors, said
`second primary for coupling to a second pair of con-
`ductors;
`a second transformer including a first primary with a first
`center—tap, a second primary with a second center—tap,
`a first secondary and a second secondary, said first and
`second secondaries for coupling to an Ethernet tele-
`phone;
`an Ethernet link including a third pair of conductors is and
`a fourth pair of conductors, said third pair of conductors
`connecting said first secondary of said first transformer
`with said first primary of said second transformer and
`said fourth pair of conductors connecting said second
`secondary of said first transformer with said second
`primary of said second transformer;
`a direct current power supply having a first output poten-
`tial on a first line and a second output potential different
`from said first output potential on a second line, said
`first line connected to said first center—tap of said first
`transformer and said second line connected to said
`second center—tap of said first transformer;
`a first potential input of an Ethernet telephone coupled to
`said first ceiiter-tap of said second transformer; and
`a second potential input of an Ethernet telephone coupled
`to said second center—tap of said second transformer.
`2. Apower feed system for Ethernet telephones according
`to claim 1, wherein said third pair of conductors is a twisted
`pair.
`3. Apower feed system for Ethernet telephones according
`to claim 2, wherein said fourth pair of conductors is a twisted
`pair.
`4. Apower feed system for Ethernet telephones according
`to claim 3, wherein said first pair of conductors is a twisted
`pair.
`5. Apower feed system for Ethernet telephones according
`to claim 4, wherein said second pair of conductors is a
`twisted pair.
`6. A system for supplying DC power to a remote device,
`said system comprising:
`a first
`transformer including a first primary, a second
`primary, a first secondary with a first center—tap and a
`second secondary with a second center—tap, said first
`
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`6,115,468
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`5
`primary for coupling to a first pair of conductors, said
`second primary for coupling to a second pair of con-
`ductors;
`a second transformer including a first primary with a first
`center—tap, a second primary with a second center—tap,
`a first secondary and a second secondary, said first and
`second secondaries for coupling to the remote device;
`an Ethernet link including a third pair of conductors and
`a fourth pair of conductors, said third pair of conductors
`connecting said first secondary of said first transformer '
`with said first primary of said second transformer and
`said fourth pair of conductors connecting said second
`secondary of said first transformer with said second
`primary of said second transformer;
`a direct current power supply having a first output poten-
`tial oii a first line and a second output potential different
`from said first output potential on a second line, said
`first line connected to said first center—tap of said first
`transformer and said second line connected to said
`second center—tap of said first transformer;
`a first potential input of the remote device coupled to said
`first center—tap of said second transformer; and
`a second potential input of the remote device coupled to
`said second center—tap of said second transformer.
`7. A system according to claim 6, wherein said third pair
`of conductors is a twisted pair.
`8. Asystem according to claim 7; wherein said fourth pair
`of conductors is a twisted pair.
`9. A system according to claim 8, wherein said first pair
`of conductors is a twisted pair.
`10. A system according to claim 9, wherein said second
`pair of conductors is a twisted pair.
`11. A system for transmitting data and a DC signal
`simultaneously between a first device and a second device,
`said system comprising:
`a first
`transformer including a first primary, a second
`primary, a first secondary with a first center—tap and a
`second secondary with a second center—tap, said first
`primary for coupling to a first pair of conductors over
`which a first data signal is to be communicated with the
`first device, said second primary for coupling to a
`second pair of conductors over which a second data
`signal is to be communicated with the first device;
`a second transformer including a first primary with a first
`center—tap, a second primary with a second center—tap,
`a first secondary and a second secondary, said second-
`ary for coupling to a third pair of conductors over
`which said first data signal is to be communicated with
`the second device, and said second secondary for
`coupling to a fourth pair of first conductors over which
`said second data signal is to be communicated with the
`second device;
`a link including a fifth pair of conductors and a sixth pair
`of conductors, said fifth pair of conductors connecting
`said first secondary of said first transformer with said
`first primary of said second transformer and said sixth
`pair of conductors connecting said second secondary of
`said first transformer with said second primary of said
`second transformer;
`a direct current power supply associated with the first
`device having a first output potential on a first line and
`a second output potential different from said first output
`potential on a second line, said first line connected to
`said first center—tap of said first transformer and said
`second line connected to said second center—tap of said
`first transformer;
`
`6
`a first potential input of the second device coupled to said
`first center—tap of said second transformer; and
`a second potential input of the second device coupled to
`said second center—tap of said second transformer.
`12. A method for supplying a DC power connection and
`a bi-directional data connection to a remote device, said
`bi—directional data connection including a first data signal
`and a second data signal, said method comprising:
`transmitting the first data signal to a first primary winding
`of a first transformer;
`receiving the second data signal from a second primary
`winding of said first transformer;
`transmitting the first data signal from a first secondary
`winding of said first
`transformer to a first primary
`winding of a second transformer;
`transmitting the second data signal from a second primary
`winding of said second transformer to a second sec-
`ondary winding of said first transformer;
`transmitting the first data signal to the device over a first
`secondary winding of said second transformer;
`receiving the second data signal from the device over a
`second secondary winding of said second transformer;
`applying a DC signal between a center—tap of said first
`secondary winding of said first
`transformer and a
`center—tap of said second secondary winding of said
`first transformer;
`extracting a DC signal from a center—tap of said first
`primary winding of said second transformer and a
`center—tap of said second primary winding of said
`second transformer; and
`applying said DC signal to the remote device.
`13. A power feed system for Ethernet telephones, said
`system comprising:
`first coupling means for coupling a first conductor of a
`first pair of conductors to a first winding of a first
`transformer;
`second coupling means for coupling a second conductor
`of said first pair of conductors to a second winding of
`said first transformer;
`third coupling means for coup ing a first conductor of a
`second pair of conductors to a first winding of a second
`transformer;
`fourth coupling means for coup ing a second conductor of
`said second pair of conductors to a second winding of
`said second transformer;
`fifth coupling means for coualing a first and second
`conductor, respectively, of an Ethernet telephone to
`said first and second conductor of said second Jair of
`conductors;
`a first and second center-tappec winding disposed in said
`first
`transformer, each said winding having a
`irst
`conductor, a second conductor and a center—ta3 con-
`ductor;
`a first and second center-tappec winding disposed in said
`second transformer, each said winding having a irst
`conductor, a second conductor and a center-taa con-
`ductor;
`means for connecting said first conductor of said irst
`center-tapped winding of said first transformer 0 said
`first conductor of said second center-tapped winding of
`said second transformer;
`means for connecting said second conductor of said irst
`center-tapped winding of said first transformer 0 said
`second conductor of said second center-tapped wincing
`of said second transformer;
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`6,115,468
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`means for applying a power signal to said first center-tap
`conductor and said second center-tap conductor of said
`first transformer;
`means for extracting a power signal from said first center-
`tap conductor and said second center-tap conductor of
`said second transformer and for applying said extracted
`power signal to said Ethernet telephone.
`14. Asystem for supplying DC power to a remote device,
`said system comprising:
`first coupling means for coupling a first conductor of a
`first pair of conductors to a first winding of a first
`transformer;
`second coupling means for coupling a second conductor
`of said first pair of conductors to a second winding of
`said first transformer;
`third coupling means for coupling a first conductor of a
`second pair of conductors to a first winding of a second
`transformer;
`fourth coupling means for coupling a second conductor of
`said second pair of conductors to a second winding of
`said second trans former;
`fifth coupling means for coupling a first and second
`conductor, respectively, of the remote device to said
`first and second conductor of said second pair of ’
`conductors;
`a first and second center-tapped winding disposed in said
`first
`transformer, each said winding having a first
`conductor, a second conductor and a center-tap con-
`ductor;
`a first and second center-tapped winding disposed in said
`second transformer, each said winding having a first
`conductor, a second conductor and a center-tap con-
`ductor;
`means for connecting said first conductor of said first
`center-tapped winding of said first transformer to said
`first conductor of said second center-tapped winding of
`said second transformer;
`means for connecting said second conductor of said first
`center-tapped winding of said first transformer to said
`second conductor of said second center-tapped winding
`of said second transformer;
`means for applying a power signal to said first center-
`tapped conductor and said second center-tapped con-
`ductor of said first transformer;
`
`8
`means for extracting a power signal from said first center-
`tap conductor and said second center-tap conductor of
`said second transformer and for applying said extracted
`power signal to the remote device.
`15. A method for supplying DC power to a remote device
`over a 4-wire Ethernet connection having a first twisted pair
`of conductors for transmission of data packets from said
`remote device and a second twisted pair of conductors for
`reception of data packets at said remote device, the method
`comprising:
`applying a first polarity of the DC power to a center tap
`of a first transformer windi11g connected across a distal
`end of the first twisted pair of conductors;
`applying a second polarity of the DC power to a center tap
`of a second transformer winding connected across a
`distal end of the second twisted pair of conductors;
`extracting said first polarity from a center tap of a third
`transformer winding connected across a proximal end
`of the first twisted pair of conductors; and
`extracting said second polarity from a center tap of a
`fourth transformer winding connected across a proxi-
`mal end of the second twisted pair of conductors.
`16. A system for supplying DC power to a remote device
`over a 4-wire Ethernet connection having a first twisted pair
`of conductors for transmission of data packets from said
`remote device and a second twisted pair of conductors for
`reception of data packets at said remote device, the system
`comprising:
`means for applying a first polarity of the DC power to a
`center tap of a first transformer winding connected
`across a distal end of the first twisted pair of conduc-
`tors;
`means for applying a second polarity of the DC power to
`a center tap of a second transformer winding connected
`across a distal end of the second twisted pair of
`conductors;
`means for extracting said first polarity from a center tap
`of a third transformer winding connected across a
`proximal end of the first twisted pair of conductors; and
`means for extracting said second polarity from a center
`tap of a fourth transformer winding connected across a
`proximal end of the second twisted pair of conductors.
`17. A system according to claim 16 further comprising an
`uninterruptible power supply for sourcing the DC power.