# Patent

## Title
Method to control current imbalance between differential pairs providing a DC power feed

## Abstract

The present invention provides a method to at least partially power an Ethernet device from a plurality of balanced network power signals received through a network connection. This involves attaching the network device to the network, wherein network signals are received and contain both power signals and/or data signals. These network signals may be passed through surge protection and power-conditioning circuitry wherein the output of these circuits may be provided to a power absorbing circuit. This power absorbing circuit may separate the communication signal and power signal from the network signal. The communication signal may be passed to a network physical layer while the power signal may be passed to a power distribution module. Additionally, because certain embodiments may provide multiple pairs of network power signals to the power absorbing circuit, the current or power associated with each power signal must be sensed and balanced. This may be done with an active control circuit. The balanced power signals may then be supplied from the power absorbing circuit to the network-attached device in order to at least partially power the network-attached device.

## Background
CROSS REFERENCE TO RELATED APPLICATIONS
This application claims the benefit of priority to and incorporates herein by reference in its entirety for all purposes, U.S. Provisional Patent Application No. 60/665,766 entitled “SYSTEMS AND METHODS OPERABLE TO ALLOW LOOP POWERING OF NETWORKED DEVICES,” by John R. Camagna, et al. filed on Mar. 28, 2005. This application is related to and incorporates herein by reference in its entirety for all purposes, U.S. patent application Ser. No. 11/207,601 entitled “SYSTEMS AND METHODS OPERABLE TO ALLOW LOOP POWERING OF NETWORKED DEVICES,” filed Aug. 19, 2005 by John R. Camagna, et al.; Ser. No. 11/207,602 entitled “A METHOD FOR DYNAMIC INSERTION LOSS CONTROL FOR 10/100/1000/10000 MHZ ETHERNET SIGNALLING,” filed Aug. 19, 2005 by John R. Camagna, et al.; and Ser. No. 11/207,595 entitled “METHOD FOR HIGH VOLTAGE POWER FEED ON DIFFERENTIAL CABLE PAIRS,” filed Aug. 19, 2005 by John R. Camagna.


TECHNICAL FIELD OF THE INVENTION
The present invention relates generally to power distribution, and more particularly to balancing current distribution between differential pairs used to feed power within a high bandwidth network.
BACKGROUND OF THE INVENTION
Many networks such as local and wide area networks (LAN/WAN) structures are used to carry and distribute data communication signals between devices. The various network elements include hubs, switches, routers, and bridges, peripheral devices, such as, but not limited to, printers, data servers, desktop personal computers (PCs), portable PCs and personal data assistants (PDAs) equipped with network interface cards. All these devices that connect to the network structure require power in order to operate. The power of these devices may be supplied by either an internal or an external power supply such as batteries or an AC power via a connection to an electrical outlet.
Some network solutions offer to distribute power over the network in addition to data communications. The distribution of power over a network consolidates power and data communications over a single network connection to reduce the costs of installation, ensures power to key network elements in the event of a traditional power failure, and reduces the number of required power cables, AC to DC adapters, and/or AC power supplies which create fire and physical hazards. Additionally, power distributed over a network such as an Ethernet network may provide an uninterruptible power supply (UPS) to key components or devices that normally would require a dedicated UPS.
Additionally, the growth of network appliances, such as but not limited to, voice over IP (VoIP) telephones require power. When compared to their traditional counterparts, these network appliances require an additional power feed. One drawback of VoIP telephony is that in the event of a power failure, the ability to contact to emergency services via an independently powered telephone is removed. The ability to distribute power to network appliances or key circuits would allow network appliances, such as the VoIP telephone, to operate in a similar fashion to the ordinary analog telephone network currently in use.
The distribution of power over Ethernet network connections is in part governed by the IEEE Standard 802.3 and other relevant standards. These standards are incorporated by reference. However, these power distribution schemes within a network environment typically require cumbersome, real estate intensive, magnetic transformers. Additionally, power over Ethernet (PoE) requirements under 802.3 are quite stringent and often limit the allowable power.
There are many limitations associated with using these magnetic transformers. Transformer core saturation can limit the current that can be sent to a power device (PD). This may further limit the performance of the communication channel. The cost and board space associated with the transformer comprise approximately 10 percent of printed circuit board (PCB) space within a modern switch. Additionally, failures associated with transformers often account for a significant number of field returns. The magnetic fields associated with the transformers can result in lower electromagnetic interference (EMI) performance.
Additionally, the power fed to the PD may be limited. One solution provided by the next generation POE standard utilizes multiple twisted pairs to source current and multiple twisted pairs to return. Due to mismatches between the twisted pairs, most of the current may flow in one pair. This may causes an overload of the line that potentially damage or overheat the line and POE. Thus, there is a need for an improved approach to distributing power in a network environment that addresses limitations imposed by magnetic transformers while maintaining the benefits thereof.
SUMMARY OF THE INVENTION
Embodiments of the present invention provide a method with which to control current imbalances between differential pairs that are providing a DC power feed within a network attached device that substantially addresses the above-identified needs as well as others. More specifically, one embodiment of the present invention provides a method to at least partially power an Ethernet device from a plurality of network power signals received through a network connection.
This method involves attaching the network device to the network. Then, network signals may be received wherein the network signals may include both power signals and/or data signals. These network signals may be passed through optional surge protection and power-conditioning circuitry, such as switching/rectifying circuitry, wherein the output of these circuits may be provided to a power feed circuit. This power feed circuit may separate the communication signal and power signal from the network signal. The communication signal may be passed to a network physical layer (PHY) while the power signal may be passed to a power distribution module. Additionally, because certain embodiments may provide multiple pairs of network power signals to the power feed circuit, the current or power associated with each power signal must be sensed and balanced. This may be done with an active control circuit. The balanced power signals may then be supplied from the power feed circuit to the network attached device in order to at least partially power the network attached device.
Another embodiment provides an Ethernet powered device (PD) that receives new pairs of power signals, as well as the ability to receive communication signals, through an attached network. This Ethernet network PD utilizes and includes an Ethernet network connector, an optional surge protection circuit, an optional switching/rectifying circuit, an active control circuit to balance multiple power signals, and a power feed circuit. The Ethernet network connector physically couples the Ethernet network device to the Ethernet network and receives four twisted pairs. The optional surge protection circuit couples to the four twisted pairs and provides surge protection for downstream components against voltage spikes seen along the four twisted pairs. The switching/rectifying circuit receives the power signals wherein a power signal is associated with each twisted pair, and each power signal is passed to the power feed circuit. The power feed circuit senses a current or power level associated with each twisted pair and then actively balances the current associated with each twisted pair. Thus, the power circuit then passes balanced power signals to the power management module, which is then operable to at least partially power the circuits of the network attached device.
Another embodiment provides a power feed circuit operable to supply power to at least a portion of an Ethernet network (i.e. network-attached) PD. This power feed circuit includes multiple differential transistor pairs, multiple pairs of differential impedances, insertion loss control circuit(s), a common-mode feedback amplifier, a differential amplifier, and a pair of output nodes. The differential transistor pairs each are operable to receive and pass an Ethernet power signal. The differential impedances each individually couple to a differential transistor drain. The differential impedance passes the Ethernet power signal and produces an input signal to the differential amplifier. The insertion loss control circuit provides an insertion loss limit to a common-mode feedback amplifier. Then the common-mode feedback amplifier senses an average Ethernet power signal and produces a common-mode feedback signal. The differential amplifier receives the common-mode feedback signal and amplifies the differential voltage across the differential impedances. The differential amplifier then produces and applies a control or feedback signals to the gate of each transistor based on the differential voltage sensed by the differential amplifier and the common-mode feedback signal. This signal drives the Ethernet power signals passed by each transistor to of a differential transistor pair to be equal while also reducing the insertion loss to or below the insertion loss limit. A pair of output nodes wherein a single node is associated with each differential transistor pair is used to feed power from the power feed circuit to the network attached PD.
The insertion loss limit may be determined logically by higher layers of the Ethernet protocol and be based on the Ethernet communication signal or it may be determined based on the differential RMS of the received Ethernet power signals as seen by a differential transistor pair. When the insertion loss limit is determined based on the differential RMS, the insertion loss control circuit is operable to automatically reduce the insertion loss based upon transmission losses experienced between the power sending equipment (PSE) and network attached PD.
Yet another embodiment provides a method to at least partially power a network attached PD from a network power signal sent through the network connection. This involves receiving and balancing multiple Ethernet power signals that may be passed through differential transistor pairs. The gates of the differential transistor pairs are dynamically adjusted to limit the insertion loss and equalize power passed through individual differential transistors. Also, the power passed by differential pairs may be balanced to address current imbalances. This may be done by sensing a drain voltage at the drain of each transistor to produce a differential feedback signal to be applied. A common-mode feedback signal is produced by determining an insertion loss limit associated with the Ethernet power signal. This insertion loss limit is used to determine a common-mode feedback signal. The common-mode feedback signal combines with the differential feedback signal and then is applied as a control signal to the gate of the transistors. Wherein the control signal enables the individual transistors to equalize the power network power signals passed and limit the insertion loss associated with the network power signals. Then these network power signals feed to a power management circuit for the PD to be powered.



BRIEF DESCRIPTION OF THE DRAWINGS
For a more complete understanding of the present invention and the advantages thereof, reference is now made to the following description taken in conjunction with the accompanying drawings wherein:
FIG. 1A depicts current Ethernet network appliances attached to the network and powered separately and their separate power connections;
FIG. 1B depicts various Ethernet network powered devices (PDs) in accordance with embodiments of the present invention;
FIG. 2A shows a traditional real-estate intensive transformer based Network Interface Card (NIC);
FIG. 2B provides a traditional functional block diagram of magnetic-based transformer power supply equipment (PSE);
FIG. 3A provides a functional block diagram of a network powered device interface utilizing non-magnetic transformer and choke circuitry in accordance with embodiments of the present invention;
FIG. 3B provides a functional block diagram of a PSE utilizing non-magnetic transformer and choke circuitry in accordance with embodiments of the present invention;
FIG. 4A illustrates two allowed power feeding schemes per the 802.3af standard;
FIG. 4B illustrates the use of embodiments of the present invention to deliver both the power feeding schemes illustrated with FIG. 4A allowed per the 802.3af standard;
FIG. 5 shows an embodiment of a network powered device (PD) in accordance with an embodiment of the present invention that integrates devices at the IC level for improved performance;
FIG. 6 illustrates the technology associated with embodiments of the present invention as applied in the case of an enterprise VoIP phone;
FIG. 7 illustrates one embodiment of a power feed circuit in accordance with an embodiment of the present invention;
FIG. 8 illustrates one embodiment of a power feed circuit in accordance with an embodiment of the present invention;
FIG. 9 illustrates one embodiment of an insertion loss circuit in accordance with an embodiment of the present invention;
FIG. 10 illustrates one embodiment of a power feed circuit diagram in accordance with an embodiment of the present invention;
FIG. 11 illustrates one embodiment of a power feed circuit diagram in accordance with an embodiment of the present invention operable to support power distribution schemes provided by the PoE plus standard; and
FIG. 12 is a logic flow diagram in accordance with an embodiment of the present invention.



DETAILED DESCRIPTION
Preferred embodiments of the present invention are illustrated in the FIGS., like numerals being used to refer to like and corresponding parts of the various drawings.
The 802.3 Ethernet network Standards, which is incorporated herein by reference, allow loop powering of remote Ethernet network devices (802.3af). The Power over Ethernet (PoE) standard and other like standards intends to standardize the delivery of power over Ethernet network cables in order to have remote client devices powered through the network connection. The side of link that supplies the power is referred to as Powered Supply Equipment (PSE). The side of link that receives the power is referred to as the Powered device (PD).
Replacing the magnetic transformer of prior PoE systems while maintaining the functionality of the transformer has been subsumed into the embodiments of the present invention. In order to subsume the functionality of the transformer, the circuits provided by embodiments of the present invention, which may take the form of ICs or discrete components, are operable to handle these functions. These functions may include, in the case of an Ethernet network application:

    
    
        1) coupling of a maximum of 57V (SELV) to the IC with the possibility of 1V peak-peak swing of a 10/100/1000M Ethernet signaling, (2.8Vp_p for MAU device);
        2) splitting the signal; 57V DC to the 802.3af Power Control unit and AC data signal to the PHY (TX and RX), while meeting the high voltage stress.
        3) couple lower voltage (5v and 3.3v) PHY transceiver to high voltage cable (57V)
        4) Supply power of 3.3V or 12V through DC-DC converter;
        5) Withstand system-level lighting strikes: indoor lighting strike (ITU K.41); outdoor lighting strike (IEC 60590)
        6) Withstand power cross @60 Hz. (IEC 60590)
        7) Fully Supports IEEE 802.3af Specification

Other network protocols may allow different voltage (i.e., a 110 volt circuit coupling to the IC) data rates (i.e., 1 GBPS or higher), and power rating.

    
    


In a solid-state implementation, common mode isolation between the earth ground of the device and the cable is required. Fixed common mode offsets of up to 1500V are possible in traditional telephony systems. Embodiments of the present invention discussed herein may deliver power via cable where the earth ground is used solely for grounding of the PD chassis. As there is no electrical connection between the earth and PoE ground, large voltage offsets are allowable.
Second, another transformer function provides surge and voltage spike protection from lightning strike and power cross faults. Wires inside the building comply with the ITU recommendation K.41 for lightning strikes. Lines external to the building must comply with IEC60590. Lightning strike testing as specified in these Standards consists in a common mode voltage surge applied between all conductors and the earth or chassis ground. As embodiments of the present invention uses the earth ground only for chassis protection, minimal stress will occur across the device, thus simplifying the circuits required by embodiments of the present invention.
According to one 802.3.af power scheme, power is delivered via the center tap of the line side transformer to receive signal transformers for transformer based designs. In the next generation POE standard, 4 twisted pairs may be used to provide DC power feed to remote powered devices (PD). Two twisted pairs will source current, two will return. This will be discussed in more detail with reference to FIGS. 4A and 4B. The embodiments of the present invention may take up to 400 ma DC from the common mode of the signal pair without disturbing the AC (1 MHz-100 MHz) differential signals on the transmit/receive pairs. Further insertion power losses associated with the differential signal should be minimal in order to maximize useful power supplied via the network connection to the PD. Embodiments of the present invention may support PoE side applications as well.
Embodiments of the present invention are operable to support PoE side applications as well. As several functions are integrated together, the entire IC ground will track the Ethernet line ground. This means that the IC potential will vary significantly (1500V) from the chassis ground. As no power is necessary from the local supply, the voltage drop will occur across an air gap.
FIG. 1A illustrates exemplary devices where power is supplied separately to network attached client devices 12-16 that may benefit from receiving power and data via the network connection. These devices are serviced by LAN switch 10 for data. Additionally, each client device 12-16 has separate power connections 18 to electrical outlets 20. FIG. 1B illustrates exemplary devices where switch 10 is a power supply equipment (PSE) capable power-over Ethernet (PoE) enabled LAN switch that provides both data and power signals to client devices 12-16. The network attached devices may include VoIP telephone 12, access points, routers, gateways 14 and/or security cameras 16, as well as other known network appliances. This eliminates the need for client devices 12-16 to have separate power connections 18 to electrical outlets 20 as shown in FIG. 1A which are no longer required in FIG. 1B. Eliminating this second connection ensures that the network attached device will have greater reliability when attached to the network with reduced cost and facilitated deployment.
Specific embodiments of the present invention may be incorporated within various powered network attached devices or Ethernet network appliances. Such appliances include, but are not limited to VoIP telephones, routers, printers, and other like devices known to those having skill in the art. Such exemplary devices are illustrated in FIG. 1B.
FIG. 2A provides a typical prior art network interface card 30 for a PD that includes network connector 32, magnetic transformer 34, Ethernet PHY 36, power converter 38, and PD controller 40. Typically, these elements are all separate and discrete devices. Embodiments of the present invention are operable to eliminate the magnetic network transformer 34 and replace this discrete device with a power feed circuit such as the one provided in FIGS. 8A and 8B or one operable to perform the functions described with respect to the logic flow diagram of FIG. 9. This power feed circuit may be implemented within an integrated circuit (IC) or as discrete components. Additionally, embodiments of the present invention may incorporate other functional specific processors, or any combination thereof into a single IC.
FIG. 2B provides a typical PSE prior art device. Here, power sourcing switch 50 includes a network connector 32, magnetically coupled transformer 52, Ethernet physical layer (PHY) 54, PSE controller 56, and multi-port switch 58. Typically these elements are all separate and discreet devices. Embodiments of the present invention may eliminate the magnetically coupled transformer 52 and replace this transformer with discreet devices that may be implemented within ICs or as discreet devices that minimizes insertion loss in order to increase power fed to downstream components. Such power feed circuits are discussed with reference to FIG. 7 and following.
Although the description herein may focus and describe a system and method for coupling high bandwidth data signals and power distribution between the IC and cable that uses transformer-less ICs with particular detail to the 802.3af Ethernet network standard, these concepts may be applied in non-Ethernet network applications and non 802.3af applications. Further, these concepts may be applied in subsequent standards that supersede the 802.3af standard.
Embodiments of the present invention may provide solid state (non-magnetic) transformer circuits operable to couple high bandwidth data signals and power signals with new mixed-signal IC technology in order to eliminate cumbersome, real-estate intensive magnetic-based transformers 34 and 52 as pictured in FIGS. 2A and 2B.
Modern communication systems use transformers 34 and 52 to provide common mode signal blocking, 1500 volt isolation, and AC coupling of the differential signature as well as residual lightning or electromagnetic shock protection. These functions are replaced by a solid state or other like circuits in accordance with embodiments of the present invention wherein the circuit may couple directly to the line and provide high differential impedance and low common mode impedance. High differential impedance allows separation of the PHY signal form the power signal. The low common mode impedance removes the need for a choke. This allows power to be tapped from the line. The local ground plane may float in order to eliminate the need for 1500 volt isolation. Additionally through a combination of circuit techniques and lightning protection circuitry, it is possible to provide voltage spike or lightning protection to the network attached device. This eliminates another function performed by transformers in traditional systems or arrangements. It should be understood that the technology may be applied anywhere where transformers are used and should not be limited to Ethernet network applications.
FIG. 3A is a functional block diagram of a network interface 60 that includes network connector 32, non-magnetic transformer and choke power feed circuitry 62, network physical layer 36, and power converter 38. Thus, FIG. 3A replaces magnetic transformer 34 with circuitry 62. In the context of an Ethernet network interface, network connector 32 may be a RJ45 connector operable to receive a number of twisted pairs. Protection and conditioning circuitry may be located between network connector 32 and non-magnetic transformer and choke power feed circuitry 62 to provide surge protection in the form of voltage spike protection, lighting protection, external shock protection or other like active functions known to those having skill in the art. Conditioning circuitry may take the form of a diode bridge or other like rectifying circuit. Such a diode bridge may couple to individual conductive lines 1-8 contained within the RJ45 connector. These circuits may be discrete components or an integrated circuit within non-magnetic transformer and choke power feed circuitry 62.
In an Ethernet network application, the 802.3af standard (PoE standard) provides for the delivery of power over Ethernet cables to remotely power devices. The portion of the connection that receives the power may be referred to as the powered device (PD). The side of the link that provides the power is referred to as the power sourcing equipment (PSE). Two power feed options allowed in the 802.3af standard are depicted in FIG. 4A. In the first alternative, which will be referred to as alternative A, LAN switch 70, which contains PSE 76 feeds power to the Ethernet network attached device (PD) 72 along the twisted pair cable 74 used for the 10/100 Ethernet signal via the center taps 80 of Ethernet transformers 82. On the line side of the transfer, transformers 84 deliver power to PD 78 via conductors 1 and 2 and the center taps 86 and return via conductors 3 and 6 and the center taps 86. In the second alternative, conductors 4, 5, 7 and 8 are used to transmit power without transformers. Conductors 4, 5, 7 and 8 remain unused for 10/100 Ethernet data signal transmissions. FIG. 4B depicts that the network interface of FIG. 3A and power sourcing switch of FIG. 3B may be used to implements these alternatives and their combinations as well.
The next generation PoE standard, uses multiple (4) twisted pairs to feed DC power to remote PD). Two twisted pairs (1 and 2, and 4 and 5) will source current; two twisted pairs (7 and 8, and 3 and 6) will return. In this alternative, which will be referred to as PoE plus, PSE 66 feeds power to the Ethernet attached device, PD 62, along the twisted pair cables 74 used for the 10/100 Ethernet signal via the center taps 80 of Ethernet transformers 82. Conductors 4, 5, 7 and 8 are used to transmit power without transformers. However, other embodiments may use transformers or solid state PSE to supply power to any twisted pair. Data communications may be optionally used for Ethernet data signal transmissions.
Returning to FIG. 3A, conductors 1 through 8 of the network connector 32, when this connector takes the form of an RJ45 connector, couple to non-magnetic transformer and choke power feed circuitry 62 regardless of whether the first or second alternative provided by 802.3af standard is utilized. These alternatives will be discussed in more detail with reference to FIGS. 5A and 5B. Non-magnetic transformer and choke power feed circuitry 62 may utilize the power feed circuit of FIGS. 7, 8A and 8B to receive and separate the data signal portion from the power signal portion. This data signal portion may then be passed to network physical layer 36 while the power signal is passed to power converter 38.
In the instance where network interface 60 is used to couple the network attached device or PD to an Ethernet network, network physical layer 36 may be operable to implement the 10 Mbps, 100 Mbps, and/or 1 Gbps physical layer functions as well as other Ethernet data protocols that may arise. The Ethernet PHY 36 may additionally couple to an Ethernet media access controller (MAC). The Ethernet PHY 36 and Ethernet MAC when coupled are operable to implement the hardware layers of an Ethernet protocol stack. This architecture may also be applied to other networks. Additionally, in the event that a power signal is not received but a traditional, non-power Ethernet signal is received the nonmagnetic power feed circuitry 62 will still pass the data signal to the network PHY.
The power signal separated from the network signal within non-magnetic transformer and choke power feed circuit 62 by the power feed circuit is provided to power converter 38. Typically the power signal received will not exceed 57 volts SELV (Safety Extra Low Voltage). Typical voltage in an Ethernet application will be 48-volt power. Power converter 38 may then further transform the power as a DC to DC converter in order to provide 1.8 to 3.3 volts, or other voltages as may be required by many Ethernet network attached devices.
Non-magnetic power feed circuitry eliminates the use of magnetic transformers within integrated system solutions. These integrated solutions provide the opportunity to increase system density by replacing magnetic transformers with power feed circuitry in the form of an IC or discreet elements such as those described by circuits provided in FIG. 7 and following.
FIG. 3B is a functional block diagram of a power-sourcing switch 64 that includes network connector 32, Ethernet or network physical layer 54, PSE controller 56, multi-port switch 58, and non-magnetic transformer and choke power supply circuitry 66. FIG. 3B is similar to that provided in FIG. 2B, wherein the transformer has been replaced with non-magnetic transformer and choke power supply circuitry 66. This power-sourcing switch may be used to supply power to network attached devices in place of the power source equipment disclosed in FIG. 2B.
Network interface 60 and power sourcing switch 64 may be applied to an Ethernet application or other network-based applications such as, but not limited to, a vehicle-based network such as those found in an automobile, aircraft, mass transit system, or other like vehicle. Examples of specific vehicle-based networks may include a local interconnect network (LIN), a controller area network (CAN), or a flex ray network. All of these may be applied specifically to automotive networks for the distribution of power and data within the automobile to various monitoring circuits or for the distribution and powering of entertainment devices, such as entertainment systems, video and audio entertainment systems often found in today's vehicles. Other networks may include a high speed data network, low speed data network, time-triggered communication on CAN (TTCAN) network, a J1939-compliant network, ISO11898-compliant network, an ISO11519-2-compliant network, as well as other like networks known to that having skill in the art. Other embodiments may supply power to network attached devices over alternative networks such as but not limited to a HomePNA local area network and other like networks known to those having skill in the art. The HomePNA uses existing phone wires to share a single network connection within a home or building. Alternatively, embodiments of the present invention may be applied where network data signals are provided over power lines.
Non-magnetic transformer and choke power feed circuitry 62 and 66 eliminate the use of magnetic transformers with integrated system solutions that provide the opportunity to increase system density by replacing magnetic transformers 34 and 52 with solid state power feed circuitry in the form of an IC or discreet component such as the power feed circuit of FIG. 7 and following.
FIG. 5 provides an illustration of an embodiment wherein the non-magnetic transformer and choke power feed circuitry 62, network physical layer 36, power distribution management circuitry 54, and power converter 38 are integrated into a single integrated circuit as opposed to being discrete components at the printed circuit board level. Optional protection and power conditioning circuitry 90 may be used to interface the IC to the network connector.
The Ethernet PHY may support the 10/100/1000 Mbps data rate and other future data networks such as a 10000 Mbps Ethernet network. The non-magnetic transformer and choke power feed circuitry 62 will supply the line power minus the insertion loss directly to the power converter 38. This will convert the power first to a 12 v supply, then subsequently to the lower supply levels. This circuit may be implemented in the 0.18 or 0.13 micron process or other like process known to those having skill in the art.
The non-magnetic transformer and choke power feed circuitry 62 implements three main functions: 802.3.af signaling and load compliance, local unregulated supply generation with surge current protection and signal transfer between the line and integrated Ethernet PHY. As the devices are directly connected to the line, the circuit may be required to withstand a secondary lightning surge. The PD controller may provide control signals to the gates of differential transistors depicted in FIG. 7 and following. These control signals may limit the insertion losses associated with the AC differential signal as well as equalize the power fed through anyone differential transistor. Portions of this controller may be discussed in further detail with reference to FIG. 7 and following.
In order for the PoE to be 802.3af standard compliant, the PoE may be required to be able to accept power with either power feeding schemes illustrated in FIGS. 4A and 4B and handle power polarity reversal. A rectifier, such as a diode bridge, or a switching network, may be implemented to ensure power signals having an appropriate polarity are delivered to the nodes of the power feed circuit. Such a circuit may be referred to generically as being a switching/rectifying circuit. Any one of the conductors 1,4,7 or 3 of the network RJ45 connection can forward bias to deliver current and any one of the return diodes connected can forward bias provide a return current path via one of the remaining conductors. Conductors 2, 5, 8 and 4 are connected in a similar fashion.
The non-magnetic transformer and choke power feed circuitry when applied to PSE may take the form of a single or multiple port switch in order to supply power to single or multiple devices attached to the network. FIG. 3B provides a functional block diagram of power sourcing switch 64 operable to receive power and data signals and then combine these with power signals, which are then distributed via an attached network. In the case where power sourcing switch 64 is a gateway or router, a high-speed uplink couples to a network such as an Ethernet network or other like network. This data signal is relayed via network PHY 54 and then provided to non-magnetic transformer and choke power feed circuitry 66. The PSE switch may be attached to an AC power supply or other internal or external power supply in order to provide a power signal to be distributed to network-attached devices that couple to power sourcing switch 64. Power controller 56 within or coupled to non-magnetic transformer and choke power feed circuitry 66 may determine, in accordance with IEEE standard 802.3af, whether or not a network-attached device, in the case of an Ethernet network-attached device, is a device operable to receive power from power supply equipment. When it is determined in the case of an 802.3af compliant PD is attached to the network, power controller 56 may supply power from power supply to non-magnetic transformer and choke power feed circuitry 66, which is then provided to the downstream network-attached device through network connectors, which in the case of the Ethernet network may be an RJ45 receptacle and cable.
The 802.3af Standard is intended to be fully compliant with all existing non-line powered Ethernet network systems. As a result, the PSE is required to detect via a well defined procedure whether or not the far end is PoE compliant and classify the amount of needed power prior to applying power to the system. Maximum allowed voltage is 57 volts to stay within the SELV (Safety Extra Low Voltage) limits.
In order to be backward compatible with non-powered systems the DC voltage applied will begin at a very low voltage and only begin to deliver power after confirmation that a PoE device is present. In the classification phase, the PSE applies a voltage between 14.5V and 20.5V, measures the current and determines the power class of the device. In one embodiment the current signature is applied for voltages above 12.5V and below 23 Volts. Current signature range is 0-44 mA.
The normal powering mode is switched on when the PSE voltage crosses 42 Volts. At this point the power MOSFETs are enabled and the large bypass capacitor begins to charge.
The maintain power signature is applied in the PoE signature block—a minimum of 10 mA and a maximum of 23.5 kohms may be required to be applied for the PSE to continue to feed power. The maximum current allowed is limited by the power class of the device (class 0-3 are defined). For class 0, 12.95 W is the maximum power dissipation allowed and 400 ma is the maximum peak current. Once activated, the PoE will shut down if the applied voltage falls below 30V and disconnect the power MOSFETs (M1, M2, M3, M4) from the line.
The power feed devices in normal power mode provide a differential open circuit at the Ethernet signal frequencies and a differential short at lower frequencies. The common mode circuit will present the capacitive and power management load at frequencies determined by the gate control circuit.
FIG. 6 provides a functional block diagram of a specific network attached appliance 92. In this case, the network attached appliance is a VoIP telephone. Network connector 32 takes form of an Ethernet network connector, such as RJ45 connector, and passes Ethernet signals to power feed circuitry 62 and PD controller 40. Non-magnetic transformer and choke power feed circuitry 62 separates the data signal and power signal. The data signal is provided to network physical layer 36. Network physical layer 36 couples to a network MAC to execute the network hardware layer. An application specific processor, such as VoIP processor 94 or related processors, couples to the network MAC. Additionally, the VoIP telephone processors and related circuitry (display 96 and memory 98 and 99) may be powered by power converter 38 using power fed and separated from the network signal by non-magnetic transformer and choke power feed circuitry 62. In other embodiments, other network appliances, such as cameras, routers, printers and other like devices known to those having skill in the art are envisioned.
Additional circuits may be used to implement specific functions in accordance with various embodiments of the present invention. One embodiment of a power feed circuit diagram is provided in FIG. 7. FIG. 7 contains a power feed circuit 120 located within non-magnetic transformer and choke power feed circuitry 62. The Ethernet network (network) power signal is received and complies with both alternative A and/or alternative B of 802.3af. Switching/rectifying circuit 122 receives the power signal from the RJ45 connector. The switching/rectifying circuit may receive the output of a surge protection circuit (not shown) or network connector 32, such as the RJ45 connector and rectify or switch the power signal to ensure a power signal with a proper polarity is applied to power feed circuit 120 of a PD. Protection and switching/rectifying circuits may not be required in a back plane application where the polarity of the power signal is known. Switching/rectifying circuit 122 may take the form of a diode bridge or network of switches (i.e. transistors) that may be located within an IC or discrete components. The power signal is provided at nodes L1N and L1P on the receive side and on the transmit side L2N and L2P of the power feed circuit as shown in FIG. 7. The Ethernet power signals pass through differential transistor pairs. The differential transistor pairs are shown as pairs M1 and M2 as well as M3 and M4. Individual Ethernet power signals pass through differential transistor pairs M1 or M2 on the receive side and M3 and M4 on the transmit side. The transistors shown may be MOSFET transistors, bipolar transistors, or other like transistors known to those having skill in the art. The power signal then will pass through a sense impedance such as resistor R1 and R2 on the receive side or R3 and R4 on the transmit side. Although the sense impedance is shown as a purely resistive impedance, this impedance may be a resistor and inductor in parallel or series or other like complex impedances known to those having skilled in the art. At the base of the sense impedance are the two output nodes of the circuit VDD and Ground. Additionally, adaptive charging circuit 121 and capacitors C1 and C1A may be located between the two output nodes. The power converter will receive the power feed from these two nodes in order to power the network attached device.
Active control circuits 125 and 126 may be employed to ensure that the power signals passed through the transistors are of equal magnitude or balanced based on other criteria. Active control circuits 125 and 126 are operable to provide common mode suppression, insertion loss control, and current balancing by controlling the gate by control signals 105, 106, 111 and 112 which are applied to the gates of differential transistors M1, M2, M3 and M4. Additionally, the active control circuits may provide temperature and load control, or other signal conditioning functions.
The active control circuit may receive inputs 107, 108, 109, and 110 from the sense impedances, inputs from common mode suppression circuits 123 and 124, inputs from L1P, L1N, L2N and L2P. Common mode suppression circuits may be placed between conductors 1, 2, 3 and 6 as shown to sample signals 101, 102, 103 and 104 upstream of RX PHY 128 and TX PHY 127. Additionally this circuitry shows for an Ethernet network connection the connection of conductors 1 and 2 to receive side PHY and conductors 3 and 6 on the transmit side PHY with DC locking capacitors that act to only pass the AC portion of the signal. Power feed portion of the circuit as well as the splitting circuitry as exemplified by the DC blocking capacitors and the diode bridge network may be implemented within an integrated circuit. At a minimum the power feed circuit may be implemented as a discreet integrated circuit. Wherein the discreet or several discreet integrated circuits may be utilized on a printed circuit board in order to realize a network interface as provided by the embodiments of the present invention.
In the instance where a conductor associated with one transistor becomes an open circuit, existing solutions may balance the current associated with each transistor by forcing the current in the unaffected transistor to zero. The active control circuits of embodiments of the present invention may sense the open circuit by sensing the currents associated with each transistor and then appropriately load the available transistors, without creating an overload condition, to ensure power to the PD remains available. Additional circuits may be used to implement specific functions in accordance with various embodiments of the present invention. These circuits may absorb power sent on differential cable pairs.
A specific circuit diagram is provided in FIG. 8 that describes a portion of the power feed circuit 120 in more detail. Power feed circuit 120 is located within non-magnetic transformer and choke power feed circuitry 62. The Ethernet (network) power signal is received and complies with both alternative A and alternative B of 802.3af as shown in the FIG. 7. Power signals having a proper polarity are applied to the portion of power feed circuit 120 shown here in FIG. 8. The power signal is provided at nodes L1N and L1P on the receive side and on the transmit side L2N and L2P of the power feed circuit 120. The Ethernet power signals pass through differential transistor pairs. In these diagrams the differential transistor pairs are shown as pairs M1 and M2 as well as M3 and M4. Individual Ethernet power signals pass through differential transistor pairs M1 or M2 on the receive side and M3 and M4 on the transmit side. The transistors shown are MOSFET transistors. However, other transistors, such as bipolar transistors or other like transistors known to those having skilled in the art may be used in place of the MOSFET transistors shown. The power signal then will pass through a sense impedance such as resistor R1 and R2 on the receive side or R3 and R4 on the transmit side. Although the sense impedance is shown as a purely resistive impedance, this impedance may be a resistor and inductor in parallel or series or other like complex impedances known to those having skilled in the art. At the base of the sense impedance are the two output nodes of the circuit VDD and Ground. The power converter will receive the power feed from these two nodes in order to power the network attached device.
To ensure that the power signals passed by each transistor are of equal magnitude, amplifier A1 on the receive side and A2 on the transmit side each sense the voltage at the drain of each transistors of the differential transistor pair to which the amplifier is coupled. This voltage equates to the voltage dropped across the sense impedances R1 and R2 or R3 and R4 respectively. The amplifiers A1 and A2 are operable to amplify the difference in voltage between the two voltages and then apply a feedback signal to the gate of individual transistors M1. M2, M3 and M4. This feedback signal forces the Ethernet power signal passed by each transistor of a differential transistor pair to be equal. (i.e. the current of M1 and M2 (or M3 and M4) are equal.)
The power feed portion of circuit 120 as well as the splitting circuitry as exemplified by the DC blocking capacitors shown in FIG. 7 and the switching/rectifying and protection circuitry may be implemented within a single IC. At a minimum the portion of the power feed circuit 120 shown in FIG. 8 may be implemented as a discreet IC. Wherein the discreet or several discreet ICs may be utilized on a PCB in order to realize a network interface as provided by the embodiments of the present invention.
Other embodiment may include additional elements to further provide for dynamic insertion loss control. Minimizing insertion loss allows the delivered power to be maximized. This may be applied to 10/100/1000/10000 megahertz Ethernet signaling, as well as signaling for other network protocols. In one embodiment, the transistors of the differential pair may have a control signal applied to the gate dynamically adjusted depending on what type of signal of 10/100/1000/10000 megahertz. This may be implemented such that the minimal drop is realized from the source to drain of that device as experienced for that particular mode of operation. The insertion loss may be based on the actual received data signal or by determining the type of signaling and applying a predetermined insertion loss for a given type of signal. Mode detection may be performed within the higher level network protocol to determine the type of signal received and associated predetermined insertion loss.
The embodiment of power feed circuit 120 shown in FIG. 8 includes an insertion loss control circuit 129. Insertion loss control circuit 129 may determine the insertion loss limit to be provided based on a differential RMS or peak detection of the received Ethernet power signals as seen by a differential transistor pair. Alternatively, this may be done using the common mode suppression circuit 124 to provide an input to the insertion loss control circuit 129. This input to the insertion loss control circuit is based on sensing the differential RMS or peak voltage seen at L1P and L1N or from twisted pairs 1, 2 and 3, 6. Insertion loss control circuit 129 receives both the insertion loss limit determined from sampling the twisted pairs, nodes L1N, L1P, L2N, and L2P, or from a voltage determined by the Ethernet PHY and fed into insertion control circuit via a connection to PHY 36. These inputs are used to produce a desired common-mode voltage input (insertion loss limit input 132 of FIG. 9) to amplifier A3 of FIG. 10. Amplifier A3 compares the measured common mode input 139 sampled between common mode resistors r1 and r2 with the desired common mode voltage supplied by insertion loss control circuit 129 and adjusts the feedback loop such that they are equal by supplying common mode control signal 134A to amplifier A1 (signal 134B to amplifier A2).
To minimize insertion loss and ensure that the power signals are of equal magnitude amplifier A1 on the receive side and A2 on the transmit side each receive a common mode feedback signal and sense the drain voltages of each transistors of the differential transistor pair, and then produces a control signal which may be applied to the gates of the differential transistors in order to force the power signals passed by the transistors to be equal.
Minimizing insertion loss allows the delivered power to be maximized. This may be applied to 10/100/1000/10000 megahertz Ethernet signaling, as well as signaling for other network protocols. In one embodiment, the transistors of the differential pair may have a control signal applied to the gate dynamically adjusted depending on what type of signal of 10/100/1000/10000 megahertz. This may be implemented such that the minimal drop is realized from the source to drain of that device as experienced for that particular mode of operation. The insertion loss limit may be based on the actual received data signal or by determining the type of signaling and applying a predetermined insertion loss for a given type of signal. Mode detection may be performed within the higher level network protocol to determine the type of signal received and associated predetermined insertion loss. The input to amplifier A1 from the amplifier A3 determines the common mode output of amplifier A1.
FIG. 9 provides a functional block diagram of one embodiment of a dynamic insertion loss control circuit for a 10/100/1000/10000 megahertz Ethernet PD. Insertion loss control limit circuit 130 includes a differential to single ended amplifier 133, a rectifier 135, and a loop filter 137. Amplifier 133 receives a pair of network signals from nodes L1P and L1N or the twisted pairs within the RJ45 cable and converts the network signal into a single ended estimate 131. Rectifier 135 converts the signal into a power estimate that loop filter 137 uses to produce a common-mode control signal 134. Multiplexer (MUX) 136 can be selected to either pass the power estimate from the loop filter 137 or a voltage determined by the Ethernet PHY (insertion loss limit input 132) to the common mode amplifier A3 of in FIG. 10). Amplifier A3 will drive the common mode level of the power transistors (M1, M2, M3 and M4) to be equal to the rms signal power level. This will ensure that the power feed circuit has the minimal insertion loss to ensure proper functionality. This common mode feedback amplifier provides common mode suppression across a wide bandwidth and can implement the equivalent function to an EMI choke filter.
FIG. 10 illustrates one embodiment of a power feed circuit in accordance with an embodiment of the present invention where insertion loss control limit circuit 130 and associated amplifiers are used to provide both a common mode feedback signal and a differential feedback signal which is then applied to the gates of the transistors M1, M2, M3, and M4 of the differential transistor pairs. This circuit is similar to the circuits provided and discussed in FIGS. 7 and 8. However the active control circuits and insertion loss control circuit are presented in further detail. Here insertion loss control limit circuit 130 receives inputs either from twisted pair 1, 2 or L1P L1N nodes on the receive side and L2P L2N or twisted pairs 3, 6 on the transmit side. Additionally insertion loss control circuit limit 130 may receive an input from Ethernet PHY 36 to determine an insertion loss limit input 132. This insertion loss control limit is compared to the common mode signal 139 sampled between resistors R5 and R8. Amplifier A3 then is operable to produce a common mode control signal 134 which is then supplied to amplifier A1.
Amplifier A1 sensing the differential voltage at the drains of transistors M1 M2 as well as the common mode control signal 134 is able to generate appropriate control signals 105 and 106 which may then be applied to the gates of transistors M1 and M2. Thus the circuit is able to reduce, minimize, or control insertion losses as well as balancing the power signals seen on each of the individual transistors within a differential transistor pair. Additionally, the circuit may balance, or actively control, the current (load) passed by a first differential transistor pair with that passed by a second differential pair. The transmit side works similarly where A4 performs the functions that were previously described with reference to amplifier A3.
FIG. 11 is a schematic diagram that illustrates a power feed circuit 120 operable to support the power distribution scheme, PoE plus. Power signals are received from a switching/rectifying circuit if the polarity of the incoming power signals is unknown. These power signal are then distributed to four differential transistor power circuits 142, 144, 146 and 148. As each of these circuits operates in a similar manner, the operation of differential transistor power circuit 142 will be discussed in detail. Rectified power signals are received at nodes L1N and L1P on the receive side. The received Ethernet power signals pass through differential transistor pair M1 and M2. The power signal then will pass through sense impedance R3 and R4. Although impedances are shown as being purely resistive, these impedances may be a resistor and inductor in parallel or series or other like complex impedances known to those having skilled in the art. At the base of the sense impedance is output node VDD. To ensure that the rectified power signals passed within differential transistor pair (i.e. transistors M1 and M2) are of equal magnitude amplifier A3 senses the voltage at the drain of transistors M1 and M2 to produce a differential component of the feedback signals 105 and 106 which are applied by amplifier A3 to the gates of transistors M1 and M2. To ensure that the rectified power signals passed within differential transistor power circuits 142 and 144 are of equal magnitude amplifier A9 senses and compares the voltages at node N3 between impedances R5 and R6 of circuit 142 and node N4 between impedances R11 and R12 of circuit 144. Inequalities between these voltages will indicate an imbalance in the power passed by circuit 142 as compared to the power passed by circuit 144. Outputs 150 and 152 of amplifier A9 is provided to amplifier A5 which also receives a common mode input 139 as measured between impedances R1 and R2. The common mode input 139 may not necessarily be required to balance power feed circuits 142 and 144. However, this common mode input allows the insertion losses to be minimized as discussed previously.
Amplifier A5 forces the common mode, or insertion loss of between cmn1 and VDD to be equal to the voltage of n1. Amplifier A3 then applies individual control signals (i.e. 105 and 106) to the gates of transistors M1 and M2 in order to equalize power feed through the differential transistors within the pair and within the receive side of the power feed circuit (i.e. circuits 142 and 144). Differential transistor power circuits 146 and 148 function in a similar manner to balance the power fed through the individual transistors of the differential transistor pairs and the transmit side of the power feed circuit. Although not shown, splitting circuitry may separate the communication signal from the power signal and then relay this portion to a coupled Ethernet PHY.
FIG. 12 provides a logic flow diagram that illustrates processing associated with at least partially powering a network attached device such as an Ethernet device from an Ethernet or network power signal fed through a network or Ethernet connection. This method involves at Step 160 receiving a number of paired rectified network power signals. To support POE plus, a pair of rectified network power signals is received on the receive side and a pair of rectified network power signals is received on the transmit side. In Step 162, the rectified power signals are passed through differential impedances to provide a first differential input (i.e. the drain voltages within a differential transistor pair as sensed in Step 164). Additionally a second differential input results in Step 166 by comparing the average power passed by the rectified power signal of each differential transistor pair. This correlates to comparing the average differential drain voltage between differential transistor pairs within It is important to realize that this common mode feedback amplifier provides common mode suppression across a wide bandwidth and can implement the equivalent function to a EMI choke filter.
The first and second differential inputs are combined in Step 168 to produce and feed a control signal to the gates of individual transistors. These control signals may be unique to each differential transistor. The Ethernet power signal may then be passed from a pair of output nodes in Step 160 in order to feed power to an Ethernet or network attached device.
In summary, the present invention provides a method to at least partially power an Ethernet device from a plurality of balanced network power signals received through a network connection. This involves attaching the network device to the network, wherein network signals are received and contain both power signals and/or data signals. These network signals may be passed through surge protection and power-conditioning circuitry wherein the output of these circuits may be provided to a power feed circuit. This power feed circuit may separate the communication signal and power signal from the network signal. The communication signal may be passed to a network physical layer while the power signal may be passed to a power distribution module. Additionally, because certain embodiments may provide multiple pairs of network power signals to the power feed circuit, the current or power associated with each power signal must be sensed and balanced. This may be done with an active control circuit. The balanced power signals may then be supplied from the power feed circuit to the network attached device in order to at least partially power the network attached device.
As one of average skill in the art will appreciate, the term “substantially” or “approximately”, as may be used herein, provides an industry-accepted tolerance to its corresponding term. Such an industry-accepted tolerance ranges from less than one percent to twenty percent and corresponds to, but is not limited to, component values, integrated circuit process variations, temperature variations, rise and fall times, and/or thermal noise. As one of average skill in the art will further appreciate, the term “operably coupled”, as may be used herein, includes direct coupling and indirect coupling via another component, element, circuit, or module where, for indirect coupling, the intervening component, element, circuit, or module does not modify the information of a signal but may adjust its current level, voltage level, and/or power level. As one of average skill in the art will also appreciate, inferred coupling (i.e., where one element is coupled to another element by inference) includes direct and indirect coupling between two elements in the same manner as “operably coupled”. As one of average skill in the art will further appreciate, the term “compares favorably”, as may be used herein, indicates that a comparison between two or more elements, items, signals, etc., provides a desired relationship. For example, when the desired relationship is that signal 1 has a greater magnitude than signal 2, a favorable comparison may be achieved when the magnitude of signal 1 is greater than that of signal 2 or when the magnitude of signal 2 is less than that of signal 1.
Although embodiments of the present invention are described in detail, it should be understood that various changes, substitutions and alterations can be made hereto without departing from the spirit and scope of the invention.

## Claims

1. A method to at least partially power an Ethernet network device, with a plurality of power signals fed through an Ethernet network connection, comprising:
physically coupling the Ethernet network device to the Ethernet network;
receiving an Ethernet signal from the Ethernet network, wherein the Ethernet signal comprises the plurality of power signals and data signal(s);
passing the Ethernet signal to an integrated circuit (IC) wherein the IC comprises:
an Ethernet physical layer (PHY) module;
a power management module; and
a direct connection module that directly connects the Ethernet network device to the Ethernet network connection with no intervening magnetic transformer; p1 separating with the direct connection module, the data signal from the Ethernet signal, wherein the data signal is passed to the Ethernet PHY module of the IC;

separating with the direct connection module, the plurality of power signals from the Ethernet signal;
sensing a current associated with each power signal of the plurality of power signals;
balancing the plurality of power signals with an active control circuit and based on the sensed current associated with each power signal of the plurality of power signals, wherein balancing the plurality of power signals comprises:
receiving the Ethernet rower signals;
determining an amplitude property of the Ethernet rower signal;
determining an insertion loss limit based on the amplitude property;
comparing the insertion loss control limit to a sampled common mode signal; and
balancing the plurality of rower signals according to the comparison, wherein the balanced plurality of power signal are passed to the power management module; and

at least partially powering the Ethernet network device from the plurality of balanced power signal.

2. The method of claim 1, wherein the balancing the plurality of power signals with an active control circuit results in each sensed current not exceeding a reference current.

3. The method of claim 1, wherein:
an RJ45 connector physically couples the Ethernet network device to the Ethernet network, and wherein the RJ45 connector couples to twisted pairs that further comprise conductors 1 and 2; 3 and 6; 4 and 5; and 7 and 8; and
a switching/rectifying circuit that receives the power signal utilizing conductors 1, 2, 3, and 6; and conductors 4, 5, 7, and 8.

4. The method of claim 3, wherein the balancing the plurality of power signals with an active control circuit results in each sensed current not exceeding a predetermined current associated with twisted pair.

5. The method of claim 1, wherein each of the plurality of power signals does not exceed 57 volts.

6. The method of claim 1, wherein the Ethernet PHY module implements 10 Mbps, 100 Mbps and 1 Gbps physical layer functions.

7. The method of claim 1, wherein the IC further comprises an Ethernet media access controller (MAC) wherein the Ethernet PHY and Ethernet MAC implement hardware layers of an Ethernet protocol stack.

8. The method of claim 1, wherein the Ethernet network device comprises at least one device selected from the group consisting of:
a voice over internet protocol (VoIP) telephone;
an Ethernet router;
an Ethernet switch;
a printer;
a data server;
an Ethernet enabled camera;
a wireless access point;
a playback device;
a portable computing device;
a personal data assistant;
a wireless terminal;
a graphics display; and
an audio interface.

9. The method of claim 1, wherein the plurality of power signals is IEEE 802.3af compliant.

10. The method of claim 1, wherein comprising supplying the power signal to the Ethernet network from a power sourcing equipment (PSE), and wherein the PSE determines whether the Ethernet network device is IEEE 802.3af compliant.

11. The method of claim 1, wherein the direct connection module further comprises a power device controller.

12. The method of claim 1, wherein separating with the direct connection module, the data signal from the Ethernet signal utilizes direct current (DC) blocking capacitors that couple the Ethernet PHY module to the Ethernet signal.

13. The method of claim 1, wherein balancing the plurality of power signals with the active control circuit further comprises actively balancing currents associated within a twisted pair, wherein the twisted pairs conduct power signal(s).

14. The method of claim 1, wherein balancing the plurality of power signals with the active control circuit further comprises:
actively controlling the current passed within a twisted pair.

15. An Ethernet network device that receives a plurality of power signals and data signals through a coupled Ethernet network, comprising:
an Ethernet network connector that physically couples the Ethernet network device to the Ethernet network, wherein the Ethernet network connector receives four twisted pairs that carry the plurality of power signals, wherein the plurality of power signals comprise a first power signal and a second power signal;
an integrated circuit (IC) coupled to the Ethernet network connector, wherein the IC comprises:
an Ethernet physical layer (PHY) module;
a power management module;
a direct connection module that directly connects the Ethernet network device to the Ethernet network connector with no intervening magnetic transformer, wherein the direct connection module:
passes the received data signal(s) to the Ethernet PHY;
senses a current associated with each twisted pair;
actively balances the current associated with each twisted pair; and
passes the received plurality of power signals to the power management module, wherein the power management module at least partially powers the Ethernet network device from the received plurality of power signals, the direction connection module further comprising:
an insertion loss control circuit coupled to the direct connection module that determines an insertion loss limit based on an amplitude property of the Ethernet power signal; compares the insertion loss control limit to a sampled common mode signal; and balances the plurality of power signals according to the comparison.

16. The Ethernet network device of claim 15, wherein:
the Ethernet network connectors comprises an RJ45 connector; and
the four twisted pairs comprise conductors 1 and 2; 3 and 6; 4 and 5; and 7 and 8;
the first power signal utilizing conductors 1, 2, 3, and 6; and
the second power signal utilizing conductors 4, 5, 7, and 8.

17. The Ethernet network device of claim 15, wherein the first power signal and second power signal each do not exceed about 17 watts.

18. The Ethernet network device of claim 15, wherein the received power signal does not exceed 57 volts.

19. The Ethernet network device of claim 15, wherein the Ethernet PHY module implements 10 Mbps, 100 Mbps and 1 Gbps physical layer functions.

20. The Ethernet network device of claim 15, wherein the IC further comprises an Ethernet media access controller (MAC) wherein the Ethernet PHY and Ethernet MAC implement hardware layers of an Ethernet protocol stack.

21. The Ethernet network device of claim 15, wherein the Ethernet network device comprises at least one device selected from the group consisting of:
a voice over internet protocol (VoIP) telephone;
an Ethernet router;
an Ethernet switch;
a printer;
a data server;
an Ethernet enabled camera;
a wireless access point;
a playback device;
a portable computing device;
a personal data assistant;
a wireless terminal;
a graphics display; and
an audio interface.

22. The Ethernet network device of claim 15, wherein the plurality of power signals are provided to the Ethernet network from a power sourcing equipment (PSE), and wherein the PSE determines whether the Ethernet network device is IEEE 802.3af compliant.

23. The Ethernet network device of claim 15, wherein the direct connection module further comprises a power device controller.

24. The Ethernet network device of claim 15, wherein direct current (DC) blocking capacitors couple the Ethernet PHY module to the received signal.