System for transmitting power to a remote PoE subsystem by forwarding PD input voltage

The present disclosure describes a system 400 for transmitting power to a remote Power over Ethernet (PoE) subsystem by forwarding Powered Device (PD) input voltage where the subsystem includes a PD and a Power Sourcing Equipment (PSE) device. Included is a master PSE device 402, a first subsystem 410, and a second subsystem 428. The first subsystem 410 includes a first PD 418 that includes a first power switching device 426 and a first PSE device 424. The first power switching device 426 forwards the input power from the first PD 418 to the first PSE 424 without disturbing the PoE handshaking between the devices. The second subsystem 428 receives the power from the first subsystem's 410 first PSE device 424. And the second subsystem 428 operates in a manner similar to the first subsystem 410.

TECHNICAL FIELD

This disclosure relates to Power over Ethernet (PoE) technology. More specifically, this disclosure invention relates to transmitting power to a remote Power over Ethernet powered device by forwarding Powered Device input voltage.

BACKGROUND ART

Power over Ethernet (PoE) technology can be used to provide electrical power to multiple electronic devices and/or systems by establishing a PoE power chain. In a typical PoE configuration a Power Sourcing Equipment (PSE) unit is used to source power to a Powered Device (PD) unit. The PSE and the PD units typically reside in separate electronic devices separated by some physical distance and are connected together typically using a RJ-45 type Ethernet cable. The PD provides regulated power to the connected subsystem where the subsystem is located.

The current PoE technology is described in the following patents.

U.S. Pat. No. 9,209,981, entitled: “Power over Ethernet on data pairs and spare pairs” describes a method where a Power over Ethernet Power Sourcing Equipment device is connected to a pair of data wires and a pair of spare wires. When the PSE first powers up if it detects a Powered Device on the data wires it applies power to the data wires via a transistor switch. Next, if it detects a PoE PD device on the spare wires it proceeds to apply PoE power to the spare wires via a second transistor switch. This is a method for a PoE device powering up a PD device directly via a switch. U.S. Pat. No. 9,209,981 is incorporated by reference for all purposes into this specification. In contrast however, one embodiment of the disclosed invention is a method to power a Power Sourcing Equipment device with the output of another Power Sourcing Equipment device.

U.S. Pat. No. 9,203,628, entitled: “Method for apparatus for distributing power over communication cabling”, describes in general about allowing Power Sourcing Equipment devices to power up Powered Device devices “directly” based on the presence of a first or second optional load. This reference does not disclose any PSE devices powering other PSE devices. U.S. Pat. No. 9,203,628 is incorporated by reference for all purposes into this specification. Again, in contrast however, one embodiment of the disclosed invention is a method to power a Power Sourcing Equipment device with the output of another Power Sourcing Equipment device.

U.S. Pat. No. 8,873,370, entitled: “Power over Ethernet management devices and connections between Ethernet devices”, illustrates multiple embodiments that pass or repeat power from one Ethernet port to another. However, in all embodiments either a Power Sourcing Equipment device is powering a Powered Device or in the embodiment where a Powered Device is powering a Power Sourcing Equipment where there is a 48V power conversion. And, in contrast however, one embodiment of the disclosed invention is a method to power a Power Sourcing Equipment device with the output of another Power Sourcing Equipment device. U.S. Pat. No. 8,873,370 is incorporated by reference for all purposes into this specification.

One or more embodiments of the disclosed invention provide a unique and distinct way for applying input power to a PoE Power Sourcing Equipment device in a subsystem to turn on the PSE. One embodiment includes a feature that include local stepped up subsystem voltages, generated by the Powered Device, which are not used to power up the Power over Ethernet PSE. Instead, the input voltage to the subsystem's PD is used and forwarded to the input of the PoE PSE in a protocol timed manner in order not to interfere with PoE power up handshaking. Embodiments of the disclosed invention have numerous advantages over the prior art that include the following features: cost reduction, power heat dissipation reduction, and power efficiency improvement.

In another embodiment of the disclosed invention, a feature is that a PSE Powered Device powering a PD device is used to power a second PSE device. In the PoE protocol, Power Sourcing Equipment devices are intended to only power PD devices in a point to point topology and are not intended to power directly another Power Sourcing Equipment device in a PoE chain.

And in another embodiment of the disclosed invention, a feature is that the Power Sourcing Equipment output voltage of a first PSE is “forwarded” to the input of a second PSE via an intelligent switch that turns on when the first PSE and a PD connected to the first PSE finalize their power up handshake.

SUMMARY OF INVENTION

The present disclosure describes an apparatus and method of an embodiment of an invention that is a system for transmitting power to a remote Power over Ethernet (PoE) subsystem by forwarding PD input voltage where the subsystem includes a Powered Device (PD) and a Power Sourcing Equipment device. This embodiment of the system includes a master Power Sourcing Equipment device, a first subsystem, and a second subsystem. The first subsystem includes a first Powered Device that includes a first power switching device and a first Power Sourcing Equipment device where the first subsystem couples to the master Power Sourcing Equipment device through a first Ethernet cable and receives power to the first Powered Device and the first Power Sourcing Equipment device using Power over Ethernet using the Power over Ethernet handshaking protocol. The first power switching device forwards the input power from the first Powered Device to the first Power Sourcing Equipment without disturbing the PoE handshaking between the devices The second subsystem, said second subsystem includes a second Powered Device that includes a second power switching device and a second Power Sourcing Equipment device where the second subsystem couples to the first subsystem through a second Ethernet cable and receives power to the second Powered Device and the second Power Sourcing Equipment device using Power over Ethernet using the Power over Ethernet handshaking protocol. The second power switching device forwards the input power from the second Powered Device to the second Power Sourcing Equipment without disturbing the PoE handshaking between the devices The second subsystem receives the power from the first subsystem's first Power Sourcing Equipment device.

The above embodiment of the invention may include one or more of the following additional embodiments that may be combined in any and all combinations with the above embodiment. One embodiment of the invention describes where the first power switching device and/or the second power switching device uses an external switching device that further includes a Zener diode coupled with a FET transistor. Another embodiment of the invention describes where the first power switching device and/or the second power switching device uses an internal switching device that further includes a digital circuit using a MOSFET transistor. Another embodiment of the invention describes where the first subsystem and/or the second subsystem further includes an intelligent switch coupled to the power switching device. Another embodiment of the invention describes where the first Power Sourcing Equipment device and/or the second Power Sourcing Equipment device further includes a battery.

In addition, the present disclosure describes an apparatus and method of an embodiment of the invention that is a system for transmitting power to a remote Power over Ethernet (PoE) subsystem by forwarding PD input voltage where the subsystem includes a Powered Device (PD) and a Power Sourcing Equipment device. This embodiment of the system includes a master Power Sourcing Equipment device, a first subsystem, and a second subsystem. The first subsystem includes a first Powered Device that includes a first means for power switching and a first Power Sourcing Equipment device where the first subsystem couples to the master Power Sourcing Equipment device through a first Ethernet cable and receives power to the first Powered Device and the first Power Sourcing Equipment device using Power over Ethernet using the Power over Ethernet handshaking protocol. The first means for power switching forwards the input power from the first Powered Device to the first Power Sourcing Equipment without disturbing the PoE handshaking between the devices. The second subsystem, said second subsystem includes a second Powered Device that includes a second means for power switching and a second Power Sourcing Equipment device where the second subsystem couples to the first subsystem through a second Ethernet cable and receives power to the second Powered Device and the second Power Sourcing Equipment device using Power over Ethernet using the Power over Ethernet handshaking protocol. The second means for power switching forwards the input power from the second Powered Device to the second Power Sourcing Equipment without disturbing the PoE handshaking between the devices. The second subsystem receives the power from the first subsystem's first Power Sourcing Equipment device.

The above embodiment of the invention may include one or more of the following additional embodiments that may be combined in any and all combinations with the above embodiment. One embodiment of the invention describes where the first means for power switching and/or the second means for power switching uses an external switching device that further includes a Zener diode coupled with a FET transistor. Another embodiment of the invention describes where the first means for power switching and/or the second means for power switching uses an internal switching device that further includes a digital circuit using a MOSFET transistor. Another embodiment of the invention describes where the first subsystem and/or the second subsystem further includes a means for an intelligent switch coupled to the means for power switching. Another embodiment of the invention describes where the first Power Sourcing Equipment device and/or the second Power Sourcing Equipment device further includes a battery.

In addition, the present disclosure describes an apparatus and method of an embodiment of the invention that is subsystem in a system for transmitting power to a remote Power over Ethernet (PoE) subsystem by forwarding PD input voltage that includes a master Power Sourcing Equipment device where the subsystem includes a Powered Device (PD) and a Power Sourcing Equipment device (PSE). This embodiment of the first subsystem couples to the master Power Sourcing Equipment device through the first Ethernet cable and receives power. The Powered Device includes a power switching device that forwards the input power from the first Powered Device to the first Power Sourcing Equipment without disturbing the PoE handshaking between the devices. The second subsystem in the system couples to the first subsystem through a second Ethernet cable and receives the power from the first subsystem's Power Sourcing Equipment device using Power over Ethernet using the Power over Ethernet handshaking protocol.

The above embodiment of the invention may include one or more of the following additional embodiments that may be combined in any and all combinations with the above embodiment. One embodiment of the invention describes where the power switching device uses an external switching device that further includes a Zener diode coupled with a FET transistor. Another embodiment of the invention describes where the power switching device uses an internal switching device that further includes a digital circuit using a MOSFET transistor. Another embodiment of the invention describes where the first subsystem further includes an intelligent switch coupled to the power switching device. And another embodiment of the invention describes where the Power Sourcing Equipment device further includes a battery.

In addition, the present disclosure describes an apparatus and method of an embodiment of the invention that is subsystem in a system for transmitting power to a remote Power over Ethernet (PoE) subsystem by forwarding PD input voltage that includes a master Power Sourcing Equipment device where the subsystem includes a Powered Device (PD) and a Power Sourcing Equipment device (PSE). This embodiment of the first subsystem couples to the master Power Sourcing Equipment device through the first Ethernet cable and receives power. The Powered Device includes a means for power switching. The second subsystem in the system couples to the first subsystem through a second Ethernet cable and receives the power from the first subsystem's Power Sourcing Equipment device using Power over Ethernet using the Power over Ethernet handshaking protocol.

The above embodiment of the invention may include one or more of the following additional embodiments that may be combined in any and all combinations with the above embodiment. One embodiment of the invention describes where the means for power switching uses an external switching device that further includes a Zener diode coupled with a FET transistor. Another embodiment of the invention describes where the means for power switching uses an internal switching device that further includes a digital circuit using a MOSFET transistor. Another embodiment of the invention describes where the first subsystem further includes an intelligent switch coupled to the means for power switching. And another embodiment of the invention describes where the Power Sourcing Equipment device further includes a battery.

The present disclosure further describes an apparatus and method of an embodiment of the invention as described herein.

DISCLOSURE OF EMBODIMENTS

The present disclosure describes a system for transmitting power to a remote Power over Ethernet subsystem by forwarding PD input voltage. The disclosed embodiments are intended to describe aspects of the disclosure in sufficient detail to enable those skilled in the art to practice the invention. Other embodiments may be utilized and changes may be made without departing from the scope of the disclosure. The following detailed description is not to be taken in a limiting sense, and the scope of the present invention is defined only by the included claims.

Furthermore, specific implementations shown and described are only examples and should not be construed as the only way to implement or partition the present disclosure into functional elements unless specified otherwise herein. It will be readily apparent to one of ordinary skill in the art that the various embodiments of the present disclosure may be practiced by numerous other partitioning solutions.

In the following description, elements, circuits, and functions may be shown in block diagram form in order not to obscure the present disclosure in unnecessary detail. Additionally, block definitions and partitioning of logic between various blocks is exemplary of a specific implementation. It will be readily apparent to one of ordinary skill in the art that the present disclosure may be practiced by numerous other partitioning solutions. Those of ordinary skill in the art would understand that information and signals may be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the description may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof. Some drawings may illustrate signals as a single signal for clarity of presentation and description. It will be understood by a person of ordinary skill in the art that the signal may represent a bus of signals, wherein the bus may have a variety of bit widths and the present disclosure may be implemented on any number of data signals including a single data signal.

The various illustrative functional units include logical blocks, modules, and circuits described in connection with the embodiments disclosed herein so as to more particularly emphasize their implementation independence. The functional units may be implemented or performed with a general purpose processor, a special purpose processor, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general purpose processor may be a microprocessor, any conventional processor, controller, microcontroller, or state machine. A general purpose processor may be considered a special purpose processor while the general purpose processor is configured to fetch and execute instructions (e.g., software code) stored on a computer readable medium such as any type of memory, storage, and/or storage devices. A processor may also be implemented as a combination of computing devices, such as a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.

In addition, the various illustrative functional units previously described above may include software or programs such as computer readable instructions that may be described in terms of a process that may be depicted as a flowchart, a flow diagram, a structure diagram, or a block diagram. The process may describe operational acts as a sequential process, many of these acts can be performed in another sequence, in parallel, or substantially concurrently. Further, the order of the acts may be rearranged. In addition, the software may comprise one or more objects, agents, threads, lines of code, subroutines, separate software applications, two or more lines of code or other suitable software structures operating in one or more software applications or on one or more processors. The software may be distributed over several different code segments, among different programs, and across several memory devices. Similarly, operational data may be identified and illustrated herein within modules, and may be embodied in any suitable form and organized within any suitable type of data structure. The operational data may be collected as a single data set, or may be distributed over different locations including over different storage devices.

Elements described herein may include multiple instances of the same element. These elements may be generically indicated by a numerical designator (e.g.110) and specifically indicated by the numerical indicator followed by an alphabetic designator (e.g.,110A) or a numeric indicator preceded by a “dash” (e.g.,110-1). For ease of following the description, for the most part element number indicators begin with the number of the drawing on which the elements are introduced or most fully discussed. For example, where feasible elements inFIG. 3are designated with a format of 3xx, where 3 indicatesFIG. 3and xx designates the unique element.

FIG. 1illustrates a system100that uses a typical Power over Ethernet Technology. The system100includes a Master source102that includes a Master Power Sourcing Equipment (PSE)104. The Master PSE provides Power over Ethernet (PoE)106to other downstream devices typically over twisted pair wires of a standard RJ-45 cable typically used in connecting devices with Ethernet in a local area network system as illustrated in system100. There are currently several types of standards for PoE such as IEEE 802.3 Alternate A and Alternate B. These standards operate in one of two fashions, either the power is routed onto unused wires in the RJ 45 cable, or the power is routed onto wires used for the data connections. Earlier versions of the PoE 802.3 standard provided up to 15.4 W of DC power (minimum 44V DC and 350 mA) on each port with only 12.95 W of power assured to be available to the device. An updated version of the PoE 802.3 standard provides up to 25.5 W of power. And as of the date of this disclosure, there is discussion of yet another updated PoE 802.3 standard with the ability to provide even more power to downstream devices. The disclosed invention will operate on any current or future versions of the PoE standards or similar type standards.

Returning back toFIG. 1, included in the PoE system100is a first subsystem108that could be another device such as a hard drive, graphics device, or any other device that connects to the network over Ethernet and may use PoE using a cable such as an RJ-45 cable. The first subsystem108may include a Powered Device (PD)110such as previously described. The PD110may provide power to other components in the subsystem via subsystem voltages112. The PD110additionally may provide power to a switcher regulator114that may be used to power an included Power Sourcing Equipment (PSE)116device that is part of the first subsystem108.

The typical PoE system100may further include a second subsystem120that could be another device such as a hard drive, graphics device, or any other device that connects to the network over Ethernet and may use PoE using a cable such as an RJ 45 cable. The second subsystem120receives power from the PSE116from the first subsystem108. The second subsystem120may include a Powered Device (PD)122such as previously described. The PD120may provide power to other components in the subsystem via subsystem voltages124. The PD120additionally may provide power to a switcher regulator126that may be used to power an included Power Sourcing Equipment (PSE)128device that is part of the first subsystem108. The PSE128may provide PoE130to other downstream subsystems that may need or require Power over Ethernet.

FIG. 2illustrates a Power over Ethernet (PoE) power on handshake200. In a PoE subsystem, a switcher regulator or similar is required to step up the subsystem voltage to a level between 44 to 57 VDC in order to power up the subsystem Power Sourcing Equipment (PSE) device that is used to power up the next Powered Device (PD) in the PoE chain. In order to power a subsystem PSE device with the PD input voltage, it is necessary to create a switching mechanism that does not interfere with the PoE power up handshaking protocol which is implemented via the PoE DC voltage lines. When a PD and PSE are first connected, there is a time period where the PD communicates with the PSE via the voltage lines following a turn on protocol. The PSE gradually increases its output power until it fully turns on at the 44-57 V range. The Detection Period202is typically less than 500 ms. The Classification Period204is typically between 50 to 75 ms. The Startup Period206is typically greater than 15 microseconds. The Operation Period208will last as long as the device is in operation and is where the input line voltage coming into the PD is between 44 to 57 V for the currently PoE standards. This input line voltage may go higher with new and/or different standards. Finally, there is the Disconnection Period210, when the PD is no longer using the PoE and is the time when the output voltage of the subsystem's PSE device goes to 0 V.

There are many issues associated with using a switcher regulator that are typically found in all PoE subsystems, which include the following: the generation of heat in the subsystem card, switching regulator cost, and some loss in power efficiency. Embodiments of the disclosed invention offer a different approach to powering up the downstream subsystem PSE devices by using a transistor switch topology that replaces the switching regulator. This technique has several advantages that include and eliminating the buildup of heat as well as improving on cost and power efficiency. Typically, the power losses across a switching regulator can be on the low end of 5 to 10% of the transmitted power, and in some PoE systems in can be higher. Using a power switching technology as disclosed in this invention, the power losses are much less. In addition, the overall loss in a PoE system where all of the subsystems utilize switching regulators, the loss attributed to the regulator can be much higher as its multiplied by the number of subsystems in the overall system. Finally, using transistor technology as disclosed in this invention cost much less than building a switching regulator.

FIG. 3illustrates one embodiment of the Power over Ethernet (PoE) power switching device300. In this embodiment of the disclosed invention, a transistor switch with level detection is used to detect when the required 44 to 57 VDC input voltage310has been detected. The power switching device in this embodiment is a combination of a FET transistor302, a 30V Zener diode304, and two resistors306and308that connect between the input voltage310and ground312. The components are chosen so that when the threshold voltage has been reached, the power switching device will be biased open. The cathode side of Zener diode304is connected to the PoE 44-57 V at the input of the Powered Device (PD). The source of FET302is connected to the Power Sourcing Equipment (PSE) device (not shown) ground at the input of the PD (not shown). The drain of FET302is connected to the ground of the subsystem PSE. The PoE voltage lines between the master PSE and the PD in the subsystem will reach 44 to 57 VDC after the turn on handshaking protocol between these two devices is completed. At this point, FET302will turn on and connect the ground pin of the subsystem's PSE device to the PSE ground of the PD.

FIG. 4discloses one embodiment of a PoE system that uses the above embodiment of the power switching technology. The system400includes a Master source402that may include one or more processors, with associated memory and/or storage (not shown separately) to perform one or more functions associated with its purpose and/or the PoE technology. The Master source402may include a Master Power Sourcing Equipment (PSE) device404component that may also include one or more processors, with associated memory and/or storage (not shown separately) to perform its power functions. The Master PSE404provides Power over Ethernet (PoE) with power406and ground408to other downstream devices typically over the twisted pair wires of a standard RJ-45 cable typically used in connecting devices with Ethernet in a local area network system as illustrated in system400.

Returning back toFIG. 4, included in the PoE system400is a first subsystem410that could be another device such as a hard drive, graphics device, or any other device that connects to the network over Ethernet and may use PoE using a cable such as an RJ 45 cable. The first subsystem410may include one or more processors, with associated memory and/or storage (not shown separately) to perform one or more functions associated with its purpose. The first subsystem410may include a Powered Device (PD)418such as previously described. In addition, the PD418may include one or more processors, with associated memory and/or storage (not shown separately) to perform one or more functions associated with its purpose. The PD418receives power420and ground422through connector412that connects subsystem410to the Master source402. The PD418may provide power to other components in the subsystem via subsystem voltages416. The PD418additionally may provide power to a Power Sourcing Equipment device (PSE)424that is part of the first subsystem410. The PSE424may include one or more processors, with associated memory and/or storage (not shown separately) to perform one or more functions associated with its purpose.

This embodiment of the disclosed invention uses the power switching device300as illustrated inFIG. 3. InFIG. 4, the power switching device426is external to PD418and PSE424. The input of the power switching device426is connected internally to the PoE 44-57 V input voltage420at the input of the PD418. The source of the FET for the power switching device426is connected to PSE device424ground at the input of the PD418. The drain of the FET in the power switching device426is connected to the ground of the subsystem PSE device424. The PoE voltage lines between the master PSE404and the PD418in the first subsystem410will reach 44 to 57 VDC after the turn on handshaking protocol between these two devices is completed. At this point, the FET in the power switching device426will turn on and connect the PSE ground pin of the first subsystem's PSE424to the PSE ground of the PD418. The power switching device426allows the PSE424to be turned on without the need of having to step up the subsystem voltages such as when using a switching regulator in a typical PoE system. The power switching device426reuses or “forwards” the 44 to 57 VDC input voltage420at the first subsystem's PD418to the subsystem's PSE device424without disturbing the PoE handshaking protocol between the PSE's and the PD's.

The first subsystem410provides Power over Ethernet (PoE) with power450and ground452to other downstream devices such as a second subsystem428. When PSE device424in subsystem410turns on, the PoE power will be available from subsystem410to turn subsystem428on. PSE device424in subsystem410will turn on the PD436in subsystem428by following the PoE handshaking protocol. The second subsystem428could be another device such as a hard drive, graphics device, or any other device that connects to the network over Ethernet and may use PoE using a cable such as an RJ 45 cable. The second subsystem428may include one or more processors, with associated memory and/or storage (not shown separately) to perform one or more functions associated with its purpose. The second subsystem428may include a Powered Device (PD)436such as previously described. In addition, the PD436may include one or more processors, with associated memory and/or storage (not shown separately) to perform one or more functions associated with its purpose. The PD436receives power438and ground440through connector430that connects the second subsystem428to the first subsystem410. The PD436may provide power to other components in the subsystem via subsystem voltages434. The PD436additionally may provide power to a PSE device442that is part of the second subsystem428. The PSE device442may include one or more processors, with associated memory and/or storage (not shown separately) to perform one or more functions associated with its purpose. The power switching device444operates in a manner similar to the power switching device426as previously described. Finally, the second subsystem428may provide a PoE connection to another subsystem through connector432that transmits power438and ground430to the downstream subsystem. As previously described, PSE device442in subsystem428turns on, the PoE power will be available from subsystem428to turn a downstream subsystem on. PSE device442in subsystem428will turn on the downstream PD in the downstream subsystem by following the PoE handshaking protocol.

Another embodiment of the disclosed invention includes using an intelligent power switching device to control the transistor switch. In this embodiment, power switching device426and power switching device444would include one or more processors, with associated memory and/or storage (not shown separately) to perform one or more functions associated with its purpose. This embodiment provides that the appropriate subsystem410and subsystem428could control and monitor the power directly and even allow the power to be monitored and controlled by other devices throughout the network. An advantage to using an intelligent power switching device is that this allows one or more devices in the network to report whether subsequent devices added to the PoE chain will have sufficient power through the PoE connection to support them.

A further advantage to an intelligent power switching device is that it would allow upstream PoE devices to turn off, power down, or cycle down some functionality in order to reduce power consumption to allow for additional downstream devices to connect to the PoE chain. If there is not sufficient power for the downstream devices, then the upstream devices (or other devices on the network) can be notified that there is not sufficient power for additional devices in this PoE chain.

Another embodiment of the disclosed invention provides that a local power source such as a battery can be attached to or included with PSE devices424and/or442. A local power source attached to a PSE can be used to allow downstream devices to connect to the system. In addition, a mid-span PoE power supply can be added in to the PoE chain so that it can be extended with additional downstream devices.

FIG. 5discloses another embodiment of a PoE system that uses a different embodiment for the power switching technology. The system500includes a Master source502that may include one or more processors, with associated memory and/or storage (not shown separately) to perform one or more functions associated with its purpose and/or the PoE technology. The Master source502may include a Master Power Sourcing Equipment (PSE) device504component that may also include one or more processors, with associated memory and/or storage (not shown separately) to perform its power functions. The Master PSE504provides Power over Ethernet (PoE) with power506and ground508to other downstream devices typically over the twisted pair wires of a standard RJ-45 cable typically used in connecting devices with Ethernet in a local area network system as illustrated in system500.

Returning back toFIG. 5, included in the PoE system500is a first subsystem510that could be another device such as a hard drive, graphics device, or any other device that connects to the network over Ethernet and may use PoE using a cable such as an RJ 45 cable. The first subsystem510may include one or more processors, with associated memory and/or storage (not shown separately) to perform one or more functions associated with its purpose. The first subsystem510may include a Powered Device (PD)518such as previously described. In addition, the PD518may include one or more processors, with associated memory and/or storage (not shown separately) to perform one or more functions associated with its purpose. The PD518receives power520and ground522through connector512that connects subsystem510to the Master source502. The PD518may provide power to other components in the subsystem via subsystem voltages516. The PD518additionally may provide power to a Power Sourcing Equipment device (PSE)524that is part of the first subsystem510. The PSE524may include one or more processors, with associated memory and/or storage (not shown separately) to perform one or more functions associated with its purpose. Connected to PD518and PSE524is ground550.

The first subsystem510provides PoE with power560and ground562to other downstream devices such as subsystem528. When PSE524in subsystem510turns on, the PoE power will be available from subsystem510to turn subsystem528on. PSE524in subsystem510will turn on the PD536in subsystem528by following the PoE handshaking protocol. The second subsystem528could be another device such as a hard drive, graphics device, or any other device that connects to the network over Ethernet and may use PoE using a cable such as an RJ 45 cable. The second subsystem528may include one or more processors, with associated memory and/or storage (not shown separately) to perform one or more functions associated with its purpose. The second subsystem528may include a Powered Device (PD)536such as previously described. In addition, the PD536may include one or more processors, with associated memory and/or storage (not shown separately) to perform one or more functions associated with its purpose. The PD536receives power538and ground540through connector530that connects second subsystem528to the first subsystem510. The PD536may provide power to other components in the subsystem via subsystem voltages534. The PD536additionally may provide power to a Power Sourcing Equipment device (PSE)542that is part of the second subsystem528. The PSE542may include one or more processors, with associated memory and/or storage (not shown separately) to perform one or more functions associated with its purpose. Finally, the second subsystem528may provide a PoE connection to another subsystem through connector532that transmits power538and ground540to the downstream subsystem. As previously described, PSE542in subsystem528turns on, the PoE power will be available from subsystem528to turn a downstream subsystem on. PSE542in subsystem528will turn on the downstream PD in the downstream subsystem by following the PoE handshaking protocol. Connected to PD536and PSE542is ground550.

In contrast to the embodiment illustrated inFIG. 4that uses an external power switching device, this embodiment of the disclosed invention use a built-in digital circuit of the PD to provide the powered switching device. For example, PD518and/or536may contain a digital circuit that has one or more MOSFET's suitable for switching power in a PoE system. When the input voltage520rises above the on-voltage threshold for the PoE technology (such as 44-57 VDC), PD518connects the input PSE device524to ground pin via power switching device526, and likewise PD536connects the input PSE device542to ground pin via power switching device544.

The PoE voltage lines between the master PSE device504and the PD518in the first subsystem510will reach 44 to 57 VDC after the turn on handshaking protocol between these two devices is completed. The power switching device526allows the PSE device524to be turned on without the need of having to step up the subsystem voltages such as when using a switching regulator in a typical PoE system. The power switching device526reuses or “forwards” the 44 to 57 VDC input voltage520at the first subsystem's PD518to the subsystem's PSE524without disturbing the PoE handshaking protocol between the PSE's and the PD's. The power switching device544operates in a manner similar to the power switching device526as previously described.

Another embodiment of the disclosed invention includes using an intelligent power switching device to control the transistor switch. In this embodiment, power switching device526and power switching device542would be controlled by a processor in PD518and a processor in PDF536respectively. The use of an intelligent power switching device in this embodiment provides the same features and benefits as previously describe.

Another embodiment of the disclosed invention provides that a local power source such as a battery can be attached or included with PSE devices524and/or542with all of the same features and benefits as previously described. As before, a mid-span PoE power supply can be added in to the PoE chain so that it can be extended with additional downstream devices.

While the present disclosure has been described herein with respect to certain illustrated and described embodiments, those of ordinary skill in the art will recognize and appreciate that the present invention is not so limited. Rather, many additions, deletions, and modifications to the illustrated and described embodiments may be made without departing from the scope of the invention as hereinafter claimed along with their legal equivalents. In addition, features from one embodiment may be combined with features of another embodiment while still being encompassed within the scope of the invention as contemplated by the inventor. The disclosure of the present invention is exemplary only, with the true scope of the present invention being determined by the included claims.