(12) Unlted States Patent
`(10) Patent No.:
`US 7,061,142 B1
`
`Marshall
`(45) Date of Patent:
`Jun. 13, 2006
`
`USOO7061142B1
`
`.............. .. 324/547
`11/1994 Hamp et a1.
`. 379/10.02
`11/1994 Borbasetal.
`
`....... .. 340/568
`4/1995 Cummings et al.
`7/1996 Lau .......................... .. 375/258
`11/1996 Vander Mey et al.
`..... .. 375/204
`8/1997 Jones etal.
`..... ..
`.. 395/187.01
`..
`8/1997 Bell et al.
`370/496
`9/1997 Ito etal.
`.. 395/187.01
`11/1997 D
`tal.
`.. 395/187.01
`8/1998 1321:1121 al.
`............... 307/140
`8/1998 Lau .......................... .. 375/258
`9/1998 Natarajan et al.
`.
`370/255
`9/1998 Ceccherelli et al.
`323/282
`9/1998 Teperetal.
`.. 395/200.59
`6/1999 Brewer et al.
`......... .. 395/200.5
`
`
`
`5,365,177 A *
`5,369,680 A *
`5,406,260 A
`5,541,957 A
`5,574,748 A
`5,655,077 A
`5,659,542 A
`5,671,354 A
`5,684,950 A
`5,796,185 A
`5,799,040 A
`5,802,042 A
`5,811,962 A *
`5,815,665 A
`5,918,016 A
`
`(Continued)
`
`EP
`
`FOREIGN PATENT DOCUMENTS
`0412 422 A2 4
`“1990
`
`(Continued)
`OTHER PUBLICATIONS
`
`Kiss, Peter (candidate), “Chapter 3, Cascaded Delta-Sigma
`ADCs”, Thesis; “Politehnica” University of Timisoara;
`cover page plus pp. 45-71, Dec. 31, 1999.
`
`(Continued)
`
`Primary ExamineriLynn Feild
`Assistant ExamineriMichael Rutland_Wallis
`
`(74) Attorney] Agent] or FirmiBaker Bong LLB
`
`According to one embodiment of the invention, a method for
`providing power to a device coupled to a communications
`switch through a data line is provided. The method includes
`determining that the device includes a diode. The method
`also includes providing power to the device in response to
`the determination.
`
`22 Claims, 3 Drawing Sheets
`
`(54)
`
`INLINE POWER DEVICE DETECTION
`
`Inventor: Robert A_ Marshalla C}e0rget0vvna
`(Us)
`.
`.
`.
`(73) ASSlgnee‘ CI?" Techmk’gy’ Inc" san Jose’ CA
`(
`)
`.
`.
`.
`.
`.
`(*) Nome:
`SUbJeCFIO any (1150131111135 the term 01“th
`Patent IS extended or adJusted under 35
`U.S.C. 154(b) by 377 days.
`
`(21) Appl.No.:10/447,419
`
`(22)
`
`Filed:
`
`May 28, 2003
`
`(51)
`
`Int. Cl.
`(2006.01)
`H03K 3/00
`(52) US. Cl.
`..................................... .. 307/106;307/105
`(58) Field of Classification Search .............. .. 307/ 105,
`307/106
`See application file for complete search history.
`
`(56)
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`4,131,767 A
`
`12/1978 Weinstein .............. .. 179/1702
`
`....... .. 340/147 SY
`7/1979 Parikh etal.
`11/1980 Boatwright et al.
`.... .. 179/18 B
`8/1983 Howson
`370/105
`7/1985 Flores et al.
`................ .. 370/85
`
`7/1986 Welty ..................... .. 179/84 T
`12/1986 Damiano et al.
`..
`361/96
`
`
`
`. 379/26
`12/1987 Ahuja ............. ..
`. 379/93
`2/1988 Jones et al.
`.... .. 370/5
`3/1988 Puvogel
`375/36
`10/1989 Curtis
`.......... ..
`11/1990 Kanare et 31.
`.............. N 379/33
`7/1991 Bindels ..................... .. 379/98
`7/ 1991 Mizutani et a1.
`. 379/79
`10/ 1991 Kanare et 31~
`- - - ~~ 379/33
`4/1992 H9W50n
`370/105
`3/1993 Wllson
`375/104
`6/1993 Cums et al.
`333/12
`5/1994 Takato et al.
`.......... .. 370/110.1
`6/1994 Smith .......................... .. 333/1
`
`- - - - -
`
`0.)OJ>
`
`4,161,719 A
`4,232,199 A
`4,397,020 A
`4,532,626 A
`
`4,599,494 A
`4,626,954 A
`
`4,710,949 A
`4,723,267 A
`4,733,389 A
`4,875,223 A
`4,969,179 A
`5,029,201 A
`5,034,948 A
`5,056,131 A
`RE33a900 E
`5,199,049 A
`5,223,806 A
`5,311,518 A
`5,321,372 A
`
`GENERATE A SIGNAL
`
`
`MEASURE THE CURRENT THAT IS
`RETURNED FROM THE DEVICE
`
`
`
`
`
`
`
`
`PROVIDE INLINE
`POWER
`
`
`
`
`
`IS
`THERE A HARMONIC
`DISTORTION?
`
`IS INLINE
`NO
`
`POWER CURRENTLY BEING
`
`PROVIDED?
`
`
`
`
`TURN OFF INLINE POWER
`
`324
`
`Page 1 of 10
`
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`

`US 7,061,142 B1
`
`Page 2
`
`U.S. PATENT DOCUMENTS
`
`“Data Terminal Equipment (DTE) Power Via Media Depen-
`dent Interface (MDI)”, IEEE P802.3af/D3.01 ReVision of
`IEEE Std. 8023-2000), 55 pages, May 2002.
`“33. Data Terminal Equipment (DTE) Power Via Media
`Dependent Interface (MDI)”, Draft Supplement to IEEE
`Standard 802.3 (IEEE Draft P802.3af/D3.2), pp. 35-38, Sep.
`5, 2002.
`“Amendment: Data Terminal Equipment (DTE) Power Via
`Media Dependent Interface (MDI)”, IEEE Draft P802.3af/
`D4.3, (IEEE Standards Department, Draft Amendment 802-
`3-2002), 31 Pages , May 2003.
`Power
`Aggregate
`Hugh
`Barrass,
`“Multi-Pair
`Distribution”iU. S. Appl. No. 10/287,886, pp. 1-25, NOV.
`4, 2002.
`Jeffrey D. Pr0Vost, “Inline Power Control”iU.S. Appl. No.
`10/618,211, pp. 1-15, Jul. 11,2003.
`Daniel C. Biederman,
`“Inline Power Based DeVice
`Communications”iU.S. Appl. No. 10/651,596, pp. 1-27,
`Aug. 29, 2003.
`Cafiero, et al. “Method and Apparatus for Remote Powering
`of DeVice Connected to Networ ” iUS. Appl No.
`10/836,923, pp. 1-16, Apr. 29, 2004.
`Roger A. Karam , “Method and Apparatus for Detecting a
`Compatible Phantom Powered DeVice Using Common
`Mode Signaling”iU.S. Appl. No. 10/855.212, pp. 1-29,
`May 26, 2004.
`Schottkky Rectifier, “ International R Rectifier”, Bullentin
`PD-20558 reV. E, 5 pages, Jan. 2003.
`Lan Man Standards Committee of the IEEE Computer
`Soecity, “Amendment: Data Terminal Equipment (DTE)
`Power via Media Dependent Interface (MDI)” , IEEE Draft
`P802.3af/D4.01., 128 pages, Jan. 2003.
`
`* cited by examiner
`
`8/1999 He ........................... .. 713/201
`5,944,824 A
`...... .. 439/676
`9/1999
`5,947,773 A
`
`11/1999 Fisher et a1.
`......... .. 340/310.01
`5,994,998 A
`1/2000 Chau et a1.
`.......... .. 395/200.59
`6,011,910 A
`2/2000 Dutcher et a1.
`........... .. 713/202
`6,021,496 A
`4/2000 Hosoe . . . . . .
`. . . .. 713/201
`6,047,376 A
`7/2000 Reiche . . . . . . . .
`. . . .. 713/200
`6,092,196 A
`9/2000 De Nicolo
`379/413
`6,115,468 A
`10/2000 De Nicolo
`...... .. 713/300
`6,134,666 A
`10/2000 Fisher et a1.
`......... .. 340/310.01
`6,140,911 A
`4/2001 Katzenberg et a1.
`340/310.01
`6,218,930 B1
`9/2001 De Nicolo
`379/413
`6,295,356 B1
`10/2001 De Nicolo
`710/300
`6,308,240 B1
`10/2001 Karam . . . . . . . . . . . .
`. . . .. 361/764
`6,310,781 B1
`2/2002 Edwards et al.
`439/170
`6,347,949 B1
`6,459,275 B1 * 10/2002 Ewalt et a1.
`.............. .. 324/539
`6,535,983 B1
`3/2003 McCormack et al.
`..... .. 713/310
`6,541,878 B1
`4/2003 Diab ......................... .. 307/17
`6,762,675 B1
`7/2004 Cafiero et a1.
`.. 340/10.42
`6,804,351 B1
`10/2004 Karam . . . . . . . . . . . .
`. . . .. 379/413
`2002/0063584 A1
`5/2002 Molenda et a1.
`.
`........ .. 327/67
`2002/0180592 A1* 12/2002 Gr0m0V ........ ..
`340/310.01
`2003/0087670 A1*
`5/2003 Muir . . . . . . . .
`. . . . . . .. 455/557
`2004/0156496 A1
`8/2004 Karam ..................... .. 379/413
`
`
`
`
`
`
`
`FOREIGN PATENT DOCUMENTS
`
`WO
`
`WO99/553408
`
`10/1999
`
`OTHER PUBLICATIONS
`
`Daniel DOVe, Powepoint Presentation, “Power 0Ver the
`DTE,”30 pages, Jan. 2000.
`Robert Muir, Powerpoint Presentation: “Update on Diode
`Discovery Process,” 30 pages, May 2000.
`
`Page 2 of 10
`
`CHRIMAR 2052
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`
`CHRIMAR 2052
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`

`

`U.S. Patent
`
`Jun. 13, 2006
`
`Sheet 1 013
`
`US 7,061,142 B1
`
`
` COMMUNICATIONS
`
`SWITCH
`
`
`COMMUNICATIONS
`
`NETWORK
`PSE
`34
`
`
`
`180
`
`188
`
`
`
`03 01<
`
`
`
`‘04
`
`FIG. 2B
`
`54
`
`Page 3 of 10
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`

`

`U.S. Patent
`
`Jun. 13, 2006
`
`Sheet 2 013
`
`US 7,061,142 B1
`
`
`
`150
`
`
`
`IS
`THERE A HARMONIC
`DISTORTION?
`
`
`
`
`
`
`
`IS INLINE
`
`POWER CURRENTLY BEING
`
`PROVIDED?
`
`
`FIG. 4B
`
`
`
` TURN OFF INLINE POWER
`
`324
`
`Page 4 of 10
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`CHRIMAR 2052
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`

`

`U.S. Patent
`
`Jun. 13, 2006
`
`Sheet 3 013
`
`US 7,061,142 B1
`
`250
`x254
`
`
`
`
`INCREASE THE VOLTAGE TO
`THE POWER DEVICE TO A
`
`PREDETERMINED LEVEL
`
`
`
`
`MEASURE THE CHANGEIN THE
`LEVEL OF CURRENT THAT IS
`
`RETURNED FROM THE DEVICE
`
`
`
`
`IS THERE
`A NON—LINEAR CHANGE IN
`
`CURRENT LEVEL?
`
`
`258
`
`260
`
`
`
`
`DECREASE THE
`VOLTAGE TO
`INITIAL LEVEL
`
`
`
`WAIT FOR A
`PREDETERMINED
`LENGTH OF TIME
`
`
`
`YES
`
`274
`
`PROVIDE INLINE POWER
`
`WAIT FOR A PREDETERMINED
`PERIOD OF TIME
`
`
`
`DECREASE INLINE
`POWER VOLTAGE TO A
`PREDETERMINED LEVEL
`
`270
`
`
`
`MEASURE THE INLINE
`POWER CURRENT
`
`
`
`IS THE
`CHANGE IN INLINE
`
`POWER CURRENT NON-LINEAR RELATIVE
`
`TO THE CHANGE IN INLINE
`
`
`POWER VOLTAGE
`
`288
`
`NO
`
`
`
`290
`
`T RN FF INLINEP W R
`U
`0
`O
`E
`_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ ____I
`
`294
`
`FIG. 4A
`
`Page 5 of 10
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`

`

`US 7,061,
`
`142 B1
`
`1
`INLINE POWER DEVICE DETECTION
`
`TECHNICAL FIELD OF THE INVENTION
`
`This invention relates generally to the field of electronic 5
`devices and more particularly to inline power device detec-
`tion.
`
`BACKGROUND OF THE INVENTION
`
`A communications switch, such as an ethernet switch,
`allows a plurality of communications devices to communi-
`cate with each other. To establish a conduit for data between
`the communications switch and the communications device,
`a connector may be coupled to a printed circuit board
`(“PCB”) of the communications switch so that the commu-
`nications device may plug into the connector to establish a
`data conduit. Such a connector is often referred to as a
`
`“jack.” Some communications switches also provide power
`through the jack, eliminating the need for the communica-
`tions device to have a separate power source. Providing
`power through the jack is referred to as “inline power.”
`A communications device that is not configured to receive
`inline power relies on a separate AC or DC power source for
`power. Such a communications device may be damaged
`when the device is plugged into a jack that provides inline
`power. For example, ethernet inline power may destroy the
`bob smith termination resistors that are coupled to the center
`tap of isolation transformers in the communications device.
`SUMMARY OF THE INVENTION
`
`According to one embodiment of the invention, a method
`for providing power to a device coupled to a communica-
`tions switch through a data line is provided. The method
`includes determining that the device includes a diode. The
`method also includes providing power to the device in
`response to the determination.
`Some embodiments of the invention provide numerous
`technical advantages. Some embodiments may benefit from
`some, none, or all of these advantages. For example, in one
`embodiment, communications devices may be plugged into
`an inline power jack for data communication regardless of
`whether the device is configured to receive inline power. In
`one embodiment, the probability of damage to communica-
`tions devices that are not configured to receive inline power
`is reduced. In one embodiment, inline power is automati-
`cally turned on or olf depending on the power configuration
`of the communications device.
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`Other technical advantages may be readily ascertained by
`one skilled in the art.
`
`50
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`Reference is now made to the following description taken
`in conjunction with the accompanying drawings, wherein
`like reference numbers represent like parts, in which:
`FIG. 1 is a schematic diagram illustrating one embodi-
`ment of a communications system that may benefit from the
`teachings of the present invention;
`FIG. 2A is a schematic diagram illustrating one embodi-
`ment of a circuit of an inline power device detection system
`that may be used in conjunction with the system shown in
`FIG. 1;
`FIG. 2B is a schematic diagram illustrating one embodi-
`ment of a circuit of an inline power device detection system
`that may be used in conjunction with the system shown in
`FIG. 1;
`
`55
`
`60
`
`65
`
`2
`
`FIG. 3A is a graph illustrating a non-linear relationship
`between a voltage level and a current level that may be
`observed at the circuit of FIG. 2A when an inline power
`device is connected to an inline power jack;
`FIG. 3B is a graph illustrating a non-linear relationship
`between the voltage level and the current level that may be
`observed at the circuit of FIG. 2A when an inline power
`device is disconnected from an inline power jack;
`FIG. 4A is a flowchart illustrating one embodiment of a
`method for inline power device detection; and
`FIG. 4B is a flowchart illustrating one embodiment of a
`method for inline power device detection.
`
`DETAILED DESCRIPTION OF EXAMPLE
`EMBODIMENTS OF THE INVENTION
`
`Embodiments of the invention are best understood by
`referring to FIGS. 1 through 4B of the drawings,
`like
`numerals being used for like and corresponding parts of the
`various drawings.
`FIG. 1 is a schematic diagram illustrating one embodi-
`ment of a communications system 10 that may benefit from
`the teachings of the present invention. System 10 comprises
`network segments 18A through 18C that are coupled to each
`other over a communications network 24 and/or a commu-
`
`nications switch 14. Network segments 18A through 18C are
`jointly referred to as network segments 18. As shown in FIG.
`1, network segment 18A is coupled to network segment 18B
`over communications switch 14. Network segment 18C is
`coupled to network segments 18A and 18B over communi-
`cations network 24 and communications switch 14. More or
`
`less network segments 18 may be coupled to each other over
`communications network 24 and communications switch 14.
`
`Network segments 18A through 18C each comprise one
`or more communications devices 20. A jack unit 30 is
`coupled to communications switch 14 to provide one or
`more ports (not explicitly shown) that may be used to
`physically connect
`communications devices
`20. For
`example, a cable having plugs may be used to plug in
`communications devices 20 to jack unit 30. In some embodi-
`ments, switch 14 and network segments 18 may be devices
`that are capable of operating according to the ethernet
`network standard.
`
`Communications switch 14 may be operable to send and
`receive packets to and from communications devices 20
`according to the addresses of the packets. Upon receiving
`one or more packets from device 20, switch 14 sends the
`received packets to a particular communications device 20
`that is identified by the included address. Switch 14 may
`send and receive the packets over network 24, jack unit 30,
`or any other suitable conduit or a combination of conduits
`that couples switch 14 to communications devices 20. In
`some examples, a hub, a router, or any other suitable device
`may be used instead of switch 14. Communications device
`20 may be any communications device that is operable to
`communicate with other communications devices over a
`
`network architecture. Examples of communications device
`20 include a Voice over Internet Protocol (“VoIP”) phone
`and a computer. Communications device 20 may also be
`referred to as a powered device 20.
`Jack unit 30 may comprise one or more RJ-45 jacks;
`however, jack unit 30 may comprise other types of jacks.
`Where jack unit 30 comprises RJ-45 jacks, communications
`devices 20 may plug into jack unit 30 using cables having
`plugs that are adaptable to a RJ-45 jack. Jack unit 30 may
`also comprise one or more isolation transformers within its
`housing. An isolation transformer is a transformer that is
`
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`

`US 7,061,142 B1
`
`3
`operable to protect the components of switch 14, such as
`integrated circuit chips, against excessive common mode
`voltages from communications devices 20 and/or cables
`attaching devices 20 to switch 14. Jack 30 generally includes
`outwardly disposed pins that may be soldered onto the
`appropriate apertures of a printed circuit board of commu-
`nications switch 14, thereby electrically coupling the com-
`ponents of jack 30 to the components of communications
`switch 14. In some embodiments,
`isolation transformers
`may be positioned on communications switch 14.
`To send and receive packets from switch 14, communi-
`cations device 20 may establish a physical connection with
`switch 14. To that end, communications device 20 may plug
`into jack 30. Along with a physical connection to switch 14,
`communications device 20 may also require access to power
`in order to send and receive packets to and from switch 14.
`Power may be provided to communications device 20 in a
`variety of ways. For example, alternating current (“AC”)
`power may be provided to communications device 20 by
`plugging communications device 20 into a wall socket. In
`another example, communications device 20 may receive
`direct current (“DC”) power from a battery pack. Power may
`also be provided inline, which refers to transmitting power
`from switch 14 to communications device 20 over a jack unit
`and the physical cable that plugs into the jack unit. Such
`power is referred to as “inline power.” A communications
`device 20 that is configured to receive inline power may not
`need a separate power source at the physical location of
`device 20. Such a device is referred to as an inline power
`device 20.
`
`However, some communications devices 20 are config-
`ured to receive inline power through jack unit 30. Such a
`device is referred to as a non-inline power device 20. If
`non-inline power device 20 is plugged into jack unit 30 that
`provides inline power, components of the non-inline power
`device 20 may be damaged. For example, the bob smith
`termination resistors coupled to the center tap of the isola-
`tion transformers that are within non-inline power device 20
`may be damaged, because the resistors are designed to
`reduce electromagnetic interference, not dissipate inline
`power.
`
`According to some embodiments of the present invention,
`a method and a system are provided that allow detection of
`an inline power device and a non-inline power device. In one
`embodiment, accidental damage to a non-inline power
`device may be avoided by allowing any communications
`devices to be coupled to a jack unit regardless of the device’s
`power configuration. However, some embodiments of the
`invention may not benefit from this or other advantages
`associated with the teachings of the present
`invention.
`Additional details of example embodiments of the invention
`are described in greater detail below in conjunction with
`FIGS. 1 through 4B.
`in one embodiment of the
`Referring back to FIG. 1,
`invention, a power supply equipment (“PSE”) 34 that is
`operable to distinguish between inline and non-inline power
`devices 20 is provided. In one embodiment, PSE 34 is
`operable to detect the presence of a diode in powered device
`20, which is a signature component of inline power device,
`by detecting a non-linear relationship between the voltage
`and the current
`levels caused by the diode. In another
`embodiment, PSE 34 is operable to detect the presence of a
`diode by detecting a harmonic distortion caused by the
`diode. PSE 34 may also be operable to turn on or turn off the
`inline power depending on the presence of a diode in
`powered device 20.
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`4
`
`FIG. 2Ais a schematic diagram illustrating a circuit 58 for
`detecting a diode 60 in a circuit 54. Circuit 54 may be
`included in inline power device 20 shown in FIG. 1. Circuit
`58 may be included in PSE 34 shown in FIG. 1. Circuit 54
`represents some components of inline power device 20, and
`comprises a diode 60, a powered device capacitor 64, a
`powered device resistor 68, a hot swap circuitry 70, an input
`capacitor 74, and a load resistor 78. Diodes 60 allow
`directional current flow when the voltage exceeds a particu-
`lar level. Such a voltage level is also referred to as a forward
`bias voltage. Powered device capacitor 64 and powered
`device resistor 68 provide a signature impedance. Hot swap
`circuitry 70 is a voltage dependent switch that does not
`activate until the voltage comes up to a particular level,
`which allows devices to be swapped while power is acti-
`vated. Input capacitor 74 and load resistor 78 respectively
`represent the capacitance and load inherent to inline power
`device 20. As shown by FIG. 2A, diodes 60 and hot swap
`circuitry 70 are serially coupled, and capacitor 64, resistor
`68, capacitor 74, and load resistor 78 are coupled in parallel.
`Circuit 54 may represent other types of powered device. But
`these powered devices each comprise a diode, such as diode
`60.
`
`Circuit 58, which is a circuit that may be included in PSE
`34 in some embodiments of the invention, comprises a
`voltage ramp 80, a current sensor resistor 84, and a control
`circuit 88. Voltage ramp 80 is operable to ramp up the
`voltage to a level sufficient
`to forward bias diodes 60
`included in circuit 54. For example,
`in one embodiment
`where two diodes 60 are each rated at 0.85 volts, voltage
`ramp 80 may be operable to raise the voltage beyond 1.9
`volts. Because diodes 60 are present in circuit 54, a change
`in the level of current is detected after diodes 60 are forward
`
`biased. Current sensor resistor 84, which is coupled to
`voltage ramp 80, is operable to measure the level of current
`that is returned from circuit 54. In one embodiment, resistor
`84 has a resistance of approximately 45 k9; however,
`resistor 84 may have any other suitable levels of resistance
`depending on the specific design requirements imposed on
`circuit 58. When a change in current level is detected and the
`rate of change in current is determined to be non-linear
`compared to the rate of voltage change instigated by voltage
`ramp 80, control circuit 88 is operable to switch on inline
`power to inline power device 20 that may include circuit 54.
`By raising the voltage past the forward biasing voltage of
`diodes 60 and detecting a non-linear relationship between
`the increase in current and the increase in voltage, circuit 58
`is operable to detect the presence of diodes 60 in circuit 54.
`Additional details regarding the ramping up of voltage and
`the resulting non-linear change in current are provided
`below in conjunction with FIG. 3A.
`To turn off the inline power when inline power device 20
`is uncoupled from circuit 58 of communications switch 14,
`control circuit 88 may be operable to periodically ramp
`down the voltage of inline power and determine whether the
`resulting reduction in current level is non-linearly propor-
`tional with the reduction of voltage. If the relationship
`between the voltage and the current
`is non-linear,
`then
`control circuit 88 raises the voltage of inline power to a level
`prior to the ramp down and continues to allow inline power
`to be provided. This is because such a non-linear relation-
`ship is caused by diodes 60, which indicates that an inline
`power device is present. However, if a non-linear relation-
`ship is not observed, control circuit 88 may turn off the inline
`power because the lack of a non-linear relationship indicates
`that a lack of diodes, which in turn indicates that no inline
`power device is present. Additional details concerning the
`
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`US 7,061,142 B1
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`5
`non-linear relationship between the voltage level and the
`current level are provided below in conjunction with FIG.
`3B.
`
`FIG. 2B is a schematic diagram illustrating a circuit 104
`for detecting diode 60 in circuit 54. Circuit 54 may be
`included in inline power device 20 shown in FIG. 1. Circuit
`104 may be included in PSE 34 shown in FIG. 1. Circuit 104
`comprises a signal generator 108, and a current sensor
`resistor 110 that may be serially coupled to signal generator
`108 at a node 112. Circuit 104 also comprises a bandpass
`filter 114, a level detector 118, and a control circuit 120 that
`are coupled to current sensor resistor 110. In one embodi-
`ment, signal generator 108 is operable to generate a sinu-
`soidal signal to circuit 54 through current sensor resistor
`110; however, signal generator 108 may be operable to
`generate any suitable types of signal depending on the
`specific design requirements imposed on circuit 104. Cur-
`rent sensor resistor 110 allows a measurement of the level of
`current that is returned from circuit 54. In one embodiment,
`resistor 110 has a resistance of approximately 45 k9;
`however, resistor 110 may have any other suitable levels of
`resistance depending on the specific design requirements
`imposed on circuit 58. Bandpass filter 114 is operable to
`measure the voltage level at node 112. In one embodiment,
`bandpass filter 114 is operable to measure the voltage level
`at different harmonic orders of the signal generated by signal
`generator 108. For example, if the signal
`is at 100 HZ,
`bandpass filter 114 may be operable to measure the voltage
`level at any or all of the odd harmonics, which includes 300
`HZ, 500 HZ, 700 HZ, and 900 HZ. Level detector 118 is
`operable to determine whether the voltage measured at
`bandpass filter 114 exceeds a predetermined limit. Control
`circuit 120 is operable to adjust the level of inline power
`provided to an inline power device using the determination
`of level detector 118. In one embodiment, control circuit 120
`may turn on or turn off inline power using the determination
`of level detector 118.
`
`the current returning from circuit 54 is
`In operation,
`measured at node 112 and the measured result is sent to
`
`bandpass filter 114 and level detector 118. Bandpass filter
`114 measures the voltage level and sends the result to level
`detector 118 to determine whether the measured voltage
`exceeds a predetermined limit. The determination that the
`measured voltages exceeds a predetermined limit indicates
`that a harmonic distortion of the signal generated by signal
`generator 108 has occurred. A harmonic distortion of a
`signal occurs when the signal passes through a switch, such
`as diodes 60. If a harmonic distortion is detected by the
`combination of bandpass filter 114 and level detector 118,
`control circuit 120 is operable to turn on inline power for
`inline power device 20. However, if no harmonic distortion
`is detected, then control circuit 120 does not turn on inline
`power. In one embodiment, if a harmonic distortion that was
`previously present is no longer detected, control circuit 120
`may turn off the inline power.
`In one embodiment where signal generator 108 is a sine
`source, bandpass filter 114 measures the voltage at the third
`harmonic order. This is advantageous in some embodiments
`because the third order is the harmonic order where the
`
`harmonic distortion generated by diode 60 is the strongest,
`which allows circuit 104 to be less susceptible to noise and
`thus avoid false detection.
`
`FIG. 3A is a graph 150 illustrating a voltage ramp up and
`a resulting change in current. Graph 150 comprises a time
`axis 154 and a voltage/current axis 158, as indicated by “t”
`and “V/I,” respectively. Voltage is increased over a period of
`time, as indicated by a line 160. At a voltage level indicated
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`6
`by a point 164, which is reached at a time 168, one or more
`diodes are forward biased. In an example where diodes 60
`of FIG. 2A each have a forward bias voltage of 0.85 volts,
`voltage level indicated by point 164 is 1.9 volts. As shown
`in FIG. 3A, there is no change in the level of current prior
`to time 168. However, current rises in response to reaching
`a voltage (1.9 volts, for example) level that is sufficient to
`forward bias the diodes in an inline power device, as
`indicated by a line 170. Although the voltage sufficient to
`forward bias a diode is indicated as 1.9 volts, other levels of
`voltage may be used to forward bias different types of
`diodes. As shown in FIG. 3A, the voltage may be repeatedly
`raised to reach a forward bias voltage in order to confirm that
`a connected power device 20 is configured to received inline
`power. For example, at time 178, the voltage may be raised
`again to point 164 to forward bias one or more diodes, which
`increases the current level, as shown by a line 180.
`FIG. 3B is a graph 200 illustrating a non-linear relation-
`ship between voltage and current when the voltage of inline
`power is spiked down periodically to determine whether
`inline power device 20 has been disconnected from jack 30.
`Graph 200 comprises a time axis 204 and a voltage/current
`axis 208, as indicated by “t” and “V/I,” respectively. Lines
`indicated by reference numerals 210 and 214 respectively
`illustrate the voltage and current levels. Although inline
`power may be provided at 48 volts, as indicated in FIG. 3B,
`inline power may be provided at any suitable voltage level.
`The spike down of inline voltage level is shown by lines 218
`and 224. The beginning of the voltage spike down is
`indicated by a time 220 and the resumption of the initial
`inline power voltage occurs at a time 228. A curve 230 of
`line 214 indicates the decrease of current that corresponds to
`the decrease of voltage indicated by line 218. A curve 234
`of line 214 indicates an increase of the current level corre-
`
`sponding to the increase of voltage shown by line 224. In
`one embodiment, energy required by load 78 during the
`spike down may be provided by capacitor 74.
`Although the rate of voltage reduction is relatively con-
`stant, as shown by line 218, the rate of current reduction is
`not, as shown by potion 230. Analogously,
`the rate of
`voltage increase shown by line 224 is relatively constant, but
`the rate of the resulting current is not, as shown by curve
`234. When the relationship between the voltage and current
`levels is non-linear, as shown by FIG. 3B, the relationship
`indicates that an inline power device is still plugged into
`communications switch 14 and inline power continues to be
`provided. If a voltage spike down results in a change of
`current level that does not bear a non-linear relationship to
`the reduction of voltage level, such a detection indicates that
`the inline power device has been removed. In response to
`such a determination, inline power may be turned of.
`Repeated voltage spike downs may be used to continually
`check whether the inline power device is still plugged into
`jack 30. As shown in FIG. 3B, voltage spike downs may be
`spaced by a predetermined time period 238. In one embodi-
`ment, the predetermined time period may equal 250 micro-
`seconds; however, any suitable periods of time that allow
`normal operation of powered device 20 may be used as
`predetermined time period 238. Further, any suitable periods
`of time that allow normal operation of powered device 20
`may be used as the time period between time 220 and 228.
`FIG. 4A is a flowchart illustrating one embodiment of a
`method 250 for detecting an inline power device, such as
`inline power device 20. Method 250 starts at 254. Steps 258,
`260, and 264 are directed to determining whether a device
`coupled to a power supply equipment includes a diode. Steps
`258, 260, and 264 constitute one way of detecting a diode;
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`US 7,061,142 B1
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`however, any other suitable method to detect a diode may be
`used. At step 258, voltage to a powered device is increased
`to a predetermined level. In one embodiment, the predeter-
`mined voltage level
`is determined depending upon the
`voltage level sufficient to forward bias a diode or a set of
`diodes. At step 260, the change in the level of current that is
`returned from the powered device is measured. At decision
`step 264, whether the change in the measured current level
`is non-linear compared to the change in voltage is deter-
`mined. If no, then the “no” branch is followed to step 268
`where the voltage is decreased to an initial voltage level. At
`step 270, a predetermined length of time is allowed to pass.
`In one embodiment, the predetermined length of time equals
`approximately half a second; however, any other suitable
`length of time may be used. In one embodiment, after it is
`determined that the measured current level has not changed
`at decision step 264, method 250 may proceed back to step
`258 without performing steps 268 and 270.
`Referring back to decision step 264, if the change is
`non-linear, then the “yes” branch is followed to step 274
`where inline power is provided. At step 278, a predeter-
`mined period of time is allowed to pass. In one embodiment,
`the predetermined period of time may equal 250 microsec-
`onds; however, any other suitable periods of time that allow
`normal operation of an inline power device may be used. At
`step 280, the inline power voltage is decreased to a prede-
`termined level. In one embodiment, inline power voltage is
`decreased by an increment greater than the forward voltage
`drop of diode 60. For example, inline power voltage may be
`dropped from 48 volts to 46 volts. However, any other
`suitable drop in voltage level may be used. At step 284, the
`inline power current is measured.
`At decision step 288, whether the change in inline power
`current is non-linear relative to the change in inline power
`voltage is determined. If yes,
`then the “yes” branch is
`followed to step 278. If no, the “no” branch is followed to
`step 290 where inline power is turned off. In one embodi-
`ment, method 250 proceeds back to step 258. Method 250
`stops at step 294.
`FIG. 4B is a flowchart illustrating one embodiment of a
`method 300 for detecting an inline power device, such as
`inline power device 20. Method 300 starts at 304. Steps 308,
`310, and 314 are directed to determining whether a device
`coupled to a power supply equipment includes a diode. Steps
`308, 310, and 314 constitute one way of detecting a diode;
`however, any other s