HK1120686B - Method and system for power supply of ethernet - Google Patents

Description

Ethernet power supply system and method

Technical Field

The present invention relates to network cable systems and methods, and more particularly, to the discovery of channel blockage in power over ethernet (PoE) applications.

Background

The ieee802.3afpoe standard provides an architecture for transferring power from a Power Sourcing Equipment (PSE) to a Powered Device (PD) over an ethernet cable. In the PoE process, detection of active devices is first performed. The detection process confirms whether a valid device is connected to ensure that power is not applied to non-POE devices.

After a valid PD is found, the PSE may optionally perform a power class. For PD devices, ieee802.3af defines 5 power classes. Completion of the power classification process enables the PSE to manage power to transfer power to different PDs connected to the PSE. If a particular power class is determined for a particular PD, the PSE may allocate the appropriate power to that PD. If no power classification is performed, a default classification will be used, i.e. the PSE supplies the entire 15.4W of power to a particular port.

Management of power budgets for different PDs connected to the PSE is important for efficient operation of the PSE. Management of power allocation is more important in PoE extension (Broad Reach) applications, where the PD is connected to the PSE over an ethernet cable of more than 100 meters (e.g., 300 and 500 meters). Typically, the total amount of power that can be allocated to different PDs is limited to the capacity range of the PSE. Therefore, a mechanism is needed to enable the PSE to determine the exact amount of power supplied to each port.

Disclosure of Invention

A system and/or method for controlling power to a powered device, substantially as shown in at least one of the figures, as set forth more completely in the claims.

According to an aspect of the present invention, there is provided a power over ethernet system comprising:

a powered device detection component to detect a presence of a powered device connected to a power device port by an Ethernet cable;

a cable detection component for measuring electrical characteristics of the Ethernet cable; and

a power controller for controlling power distribution to the power equipment ports based on the presence of the Ethernet-over-cable intermediate connector, wherein the presence is represented by the measured electrical characteristic.

Preferably, the cable detection component measures a break in the ethernet cable.

Preferably, the power controller controls the power distribution based on the type of cable, the length of the cable, and the presence of the connector.

Preferably, the power controller controls the power distribution based on a resistance of the ethernet cable, wherein the resistance of the ethernet cable is determined using the type of the ethernet cable.

Preferably, the power controller controls power distribution based on availability of the ethernet cable.

Preferably, the power supply controller determines the power allocation allocated to the port.

According to one aspect of the present invention, there is provided a method of power over ethernet, comprising the steps of:

determining, based on the measured electrical characteristic, whether a connector is present in the middle of the Ethernet cable on a connection by a powered device to a power device port via the Ethernet cable;

allocating power to the power source device port, the allocated power based on the determining step.

Preferably, the determining step comprises measuring an interruption in the ethernet cable.

Preferably, the power distribution of the distribution is based on cable type, cable length, and presence of the ethernet cable intermediate connector.

According to one aspect of the present invention, there is provided a method of power over ethernet, comprising the steps of:

determining whether a connector is present in the middle of an Ethernet cable based on the measured electrical characteristics of the Ethernet cable, the Ethernet cable connecting a powered device to a power device;

determining whether to supply power to the powered device based on the connector determining step.

Preferably, the power determining step is used when the ethernet cable is greater than 100 meters.

Preferably, the power determining step is used when a category 3 cable is used in an ethernet enhanced application.

Preferably, the power supply determining step is also based on the type and length of the ethernet cable.

Preferably, the determining step is based on determining the interruption in the ethernet cable.

Drawings

The various advantages, aspects, novel features, and details of embodiments of the invention may be more completely understood with reference to the following description and drawings. The present invention is illustrated by way of example, and therefore is not to be limited by the specific embodiments disclosed herein, which are described in further detail below with reference to the accompanying drawings and examples, wherein:

FIG. 1 is a schematic diagram of one embodiment of a Power over Ethernet (PoE) system of the present invention;

FIGS. 2A and 2B are circuit schematics of an analog PoE system of the present invention;

FIG. 3 is a flow chart of the PoE process of the present invention;

FIG. 4 is a schematic diagram of an example of a connector intermediate to the media dependent interface links of the present invention;

FIG. 5 is a schematic diagram of one embodiment of a PoE system of the present invention that may send cable characteristic information from a PHY to a PSE;

FIG. 6 is a flow chart of the process of the present invention for transmitting cable characteristic information from the PHY to the PSE.

Detailed Description

Various embodiments of the invention will be discussed in detail below. Although specific implementations are discussed, it is understood that this is by way of example only. It will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the spirit and scope of the invention.

Fig. 1 is a schematic diagram of a power over ethernet (PoE) system according to an embodiment of the present invention. As shown, the PoE system includes a power source device (PoE)120 that transmits power to a Powered Device (PD) 140. The power sent by the PSE to the PD is provided by an applied voltage across the center taps (taps) of a transformer connected to a pair of Transmit (TX) and a pair of Receive (RX) lines loaded within the ethernet cable. The two pairs of TX and RX lines enable data to be transmitted between ethernet PHYs 110 and 130.

As further shown in fig. 1, the PD 140 includes an 802.3af module 142. The module includes electronics that enable the PD 140 to communicate with the PSE 120 in the ieee802.3af standard. The PD 140 also includes a Pulse Width Modulation (PWM) DC: DC controller 144, which controls a power FET 146, which in turn provides constant power to a load 150. Generally, there are two types of loads: a purely resistive load (e.g., a light bulb) and a constant power load fed by a DC: DC power controller. The current application is mainly a constant power load fed by a DC: DC power controller.

The power transfer from the PSE 120 to the load 150 may be simulated using the circuit model shown in fig. 2A. As shown, the power supply provides a voltage V for a circuit_PSEThe circuit comprises a first pair of parallel resistors (R)₁、R₂) Load resistance R_LOADAnd a second parallel resistor pair (R)₃、R₄). Wherein the first parallel resistor pair R₁、R₂Representing the resistance of the TX wire pair, and a second parallel resistance pair R₃、R₄Representing the resistance of the RX wire pair.

Resistance R₁、R₂、R₃And R₄Depending on the type and length of the ethernet cable. In particular, the resistance R₁、R₂、R₃And R₄Has a certain resistance/length that depends on the type of ethernet cable (e.g., category 3, 5, 6, etc.). For example, for a class 5 Ethernet cable, the resistance R₁、R₂、R₃And R₄Having a resistance of about 0.1 omega/meter. Thus, for a 100 meter class 5 Ethernet cable, the resistance R₁、R2. Each of R3, and R4 has a resistance of 10 Ω. In this example, the parallel resistors R1 and R2 have a resistance of 5 Ω, and the parallel resistor R₃And R₄With a resistance of 5 omega. In combination, the Ethernet resistance (R) can be determined_cable) The total resistance is 5 Ω +5 Ω to 10 Ω. The simplified PoE circuit model can include a single cable resistor value R as shown in fig. 2B_cable。

As further shown in FIG. 2B, the circuit model also includes a series resistor R_con. The series resistor R_conRepresenting the resistance added due to the connectors present in the middle of the Media Dependent Interface (MDI) link. As shown in fig. 3, the connectors in the middle of the MDI link are introduced by including a cross-connect system, a wall outlet, or similar device in the middle of the MDI link.

Note the above resistance R of a category 5 cable_cableApproximately 0.1 omega/meter. For 100 meters of category 5 cable, resistance R_cableAnd thus 10 omega. It should be noted that this approximation includes the resistance of the cable itself, as well as the resistance of the two terminal connectors. The resistance value contributed by the two terminal connectors to the cable is approximately 0.5 omega.

Since the cable includes additional connectors in the middle of the MDI link, resistors are further added to the circuit model. The contribution value of the resistance to the total resistance is represented as R in the circuit model of FIG. 2B_con. For a load system including connectors in the middle of an MDI link, R_conCan reach about 2.5 omega. Understandably, R_conCan be expressed as a true contribution to the MDI link. In particular, by calculation for 100 meters of category 5 cable, when 10 Ω R is added_cableR of 2.5. omega_conThe total link resistance will be increased by 25%.

In the ieee802.3af standard, the PSE may optionally perform a classification step to determine the power class of the PD. Table 1 below shows the 5 PD classes supported by the ieee802.3af standard.

Grade	Use of	Minimum power output of PSE	Maximum power input at PD
				0	By default	15.4W	0.44 to 12.95W
1	Can select	4.0W	0.44 to 3.84W
				2	Can select	7.0W	3.84 to 6.49W
3	Can select	15.4W	6.49 to 12.95W
				4	Retention	As rank 0	Retention

TABLE 1

As shown, class 0 (default) and class 3 PDs specify a minimum output power of 15.4W for the PSE. For low power PDs (e.g., class 1 and class 2 devices), the PSE minimum output power is specified to be 4.0W and 7.0W, respectively. Although optional, confirming the correct PD power class enables the PSE to supply only as much power as it needs for each port. This effectively increases the ability of the PSE to power a group of PDs connected thereto.

It is a feature of the present invention that one or more characteristics of the ethernet cable are measured for affecting the operation of the PoE system. In an embodiment, the measured characteristics are used to determine one or more types of ethernet cables, lengths of ethernet cables, and presence of MDI link intermediate connectors. The determined type and length of the ethernet cable, and the presence of the connector, may then be used to estimate the resistance of the ethernet cable. The estimated resistance of the ethernet cable may then be used to estimate the power loss in the cable that affects the allocation of power to a particular PSE port.

Fig. 4 illustrates the general process of the present invention. As shown, the process begins at step 402, which measures one or more characteristics of the Ethernet cable. In one embodiment, this measurement step is performed as part of the PHY analysis of the electrical characteristics of the ethernet cable. For example, the measurement step is performed as part of an echo cancellation convergence process (echo cancellation convergence process) performed by the PHY.

In an embodiment of the present invention, the one or more characteristics of the ethernet cable measured at step 402 may enable the PoE system to better estimate the resistance of the ethernet cable. Here, the estimated actual cable resistance may cause the PoE system to estimate the actual power loss of the cable. In one embodiment, the PHY is designed to measure characteristics to enable determination of insertion loss, crosstalk, length, and discontinuities in the ethernet cable.

After measuring one or more characteristics of the ethernet cable, the PoE system then determines the type, length, and presence of link intermediate connectors of the ethernet cable at step 404. The type of ethernet cable may be determined based on the measured insertion loss, crosstalk, and length of the ethernet cable. These measurements on the ethernet cable may cause the PoE system to determine, for example, whether the ethernet cable is a category 3, 5, 6, or 7 ethernet cable. In an embodiment, the presence of a link intermediate connector is determined based on an interruption identified using Time Domain Reflectometry (TDR).

It will be appreciated that different types of cables have different resistances associated therewith. It is noted that category 3 cables have a resistance of about 0.2 Ω/meter, while category 5 ethernet cables have a resistance of about 0.1 Ω/meter. The presence of the link intermediate connectors also increases the effective cable resistance. Once it is determined that the type, length, and presence of connectors in the middle of the link of the ethernet cable at step 404, the PoE system next determines the relevant impact on the PoE system at step 406.

As will be described in greater detail below, a particular effect on a PoE system can vary depending on the application involved. Here, a feature of the present invention is: during dynamic configuration and operation, the PoE system can use cable type, cable length, and presence information of connectors. For example, cable type, cable length, and connector presence information may be used to diagnose the ethernet cable, determine whether a PD may be powered, determine adjustments to power allocation for a given PSE port, and so forth.

To demonstrate the different ways in which cable type, cable length, and presence information of connectors affect a PoE system, consider the first application associated with a conventional PoE system supported by the ieee802.3af specification. In this application, the cable type and lengthThe determination may be used to determine the resistance R_cableAnd determination of the presence of a connector in the middle of a link may be used to determine the resistance R_con(see FIG. 2B).

In the circuit model of FIG. 2B, the PD includes a DC-DC converter, a load R_LReceiving constant power R_LThe voltage applied to its input terminal is V_L. Because of P_LFixed at the load, P_L＝I*V_LWhere I is the current flowing through the entire circuit. The power loss of the cable is P_loss＝I²*(R_cable+R_con)。

The ieee802.3af standard assumes that when the PD is connected to the PSE using 100m class 3 cable, the worst case link resistance is 20 Ω, so a minimum output power of 15.4W is specified for the PSE. At a current limit of 350mA, the worst-case power loss for the cable is P_loss＝(350Ma)²20 Ω ═ 2.45W. The 2.45W worst-case power loss is the difference between the PSE's minimum output power and the maximum power achieved by the PD (e.g., 15.4W-12.95W — 2.45W).

The worst-case power allocation to the PSE port may be adjusted based on the determined ethernet cable type. In particular, the determination of the type of ethernet cable may result in a more accurate assessment of power loss when other characteristics of the PoE system are not known. For example, assume that the measured characteristics represent: the PD is connected to the PSE using a class 5 line instead of a class 3 line. Further assume that a load system is present (i.e. a connector in the middle of the link) and that a worst-case cable length of 100 meters and a current of 350mA are assumed, when the cable resistance is estimated as: 12.5 Ω for category 5 cable; rather than 20 omega for a category 3 cable. The determined resistance is reduced, so that the power loss can be reduced to P_loss＝(350mA)²12.5 Ω to 1.53W. The worst-case power losses can be compared, with a difference of 2.45W-1.53W-0.92W. The saved 0.92W of power may reduce the power allocation to the ports, thus effectively increasing the capabilities of the PSE.

By determining the cable length and cable type, more accuracy can be achievedThe power loss is estimated. In one embodiment, the cable length is determined using TDR. Together with the supplementary cable length information, the estimated cable resistance can be further reduced from a worst case 100 meter load system. For example, assume that the cable type is determined to be category 5, and further that the cable length is determined to be 50 meters. In this example, R_cableIt can be reduced by half to 5 omega. For a load link with 50 meters of category 5 cable, the power loss is P_loss＝(350mA)²(5 Ω +2.5 Ω) ═ 0.92W. The corresponding power savings is 2.45W-0.92W-1.53W, which may reduce the power allocation to the ports. It should be noted that determining the cable type alone may also result in the power savings described above. While prior systems have attempted to use cable length determination in typical PoE applications (e.g., less than 100 meters), use of cable length determination in PoE applications greater than 100 meters is a unique feature of the present invention.

According to the present invention, by additionally determining the presence (or absence) of a connector in the middle of a link, power loss can be estimated more accurately. If it is determined that there is no connector in the middle of the link, the resistance of the link may be further reduced to R_con0. In particular, for a 50 meter class 5 cable unloaded link, the power loss may be P_loss＝(350mA)²(5 Ω +0 Ω) ═ 0.61W. The corresponding power savings is 2.45W-0.61W ═ 1.84W, which indicates: more power supply is saved for the port.

Generally, certain factors (e.g., cable type, cable length, and presence of a link intermediate connector) may be used to reduce power distribution. Notably, these benefits can be achieved without knowledge of any additional information of the PoE system. More detailed power loss calculations can also be obtained if additional information is available.

The voltage drop across the cable may be defined as V_PSE-V_L＝I*R_totalWherein R is_total＝R_cable+R_con. For voltage V at PD_LThe equation is solved as:

V_PSE-V_L＝I*R_total

V_PSE-V_L＝(P_L/V_L)*R_total

V_PSE*V_L-V_L ²＝P_L*R_total

V_L ²-V_PSE*V_L+P_L*R_total＝0

V_L＝[V_PSE+/-SQRT(V_PSE ²-(4*P_L*R_total))]/2

if V is known_PSEIs 48V, P_L12.95W (maximum power to PD), and R_total＝R_cable+R_con5 Ω +2.5 Ω -7.5 Ω (resistance of the load system of 50 meters of category 5 cable), then V_L＝(48+/-SQRT(48²-4 × 12.95 × 7.5))/2 ═ (48+/-43.77)/2 ═ 45.89V. V can then be used_PSE-V_L＝I*R_totalThe current, i.e., 48V-45.89V ═ I × 7.5 Ω, was calculated, resulting in I ═ 0.281A. The total power output of the PSE is 12.95 times the power loss in the cable. In this example, the power loss in the cable is I²*R_total＝(0.281A)²7.5 Ω ═ 0.59W. In this example, the total power allocation for the PSE port is 12.95W +0.95W — 13.54W. The power savings is then allocated to 15.4W-13.54W-1.86W.

As these examples show, using the assumed worst case cables will result in unnecessary waste in the port power supply. When all of the PSE ports are aggregated, the waste in power supply unnecessarily reduces the actual power supply capacity of the PSE.

A second application in accordance with the principles of the present invention is PoE + applications, such as those supported by the future ieee802.3at specification. PoE + applications are designed to support more powerful PDs and assume the use of class 5 wires or better ethernet cables. For a dual pair PoE + system, up to 30W of PD can be considered; whereas for a 4-pair PoE + system, a PD of up to 56W may be considered. It will be appreciated that the same principle can be applied for the dual and 4-pair systems. Generally, higher power PDs using PoE + will become possible, such as WiMAX transmitters, pan-tilt-zoom cameras (pan-zoom cameras), video phones, and thin clients (thin clients).

In this application, the principles of the present invention are first used as a diagnostic tool to identify the ethernet cable connected to a PSE port. In one embodiment, the diagnostic tool will confirm one or more characteristics of the ethernet cable and use the obtained information to determine how to operate the PoE + PD device. For example, designing a PSE to enable intelligent decisions on how much power allocation a port can make.

For the existing 802.3af device, the worst-case power loss in the cable is P_loss＝(350mA)²20 Ω ═ 2.45W. The worst case power loss is based on the current limit per PD350mA and the resistance of the class 3 ethernet cable 20 Ω due to the limitations of the cable and patch panel. In current doubled PoE + devices, for example, the power loss for class 5 cables is P_loss＝(700mA)²*10Ω＝4.9W＝2*P_loss. As this simple calculation shows, the power loss per meter in PoE + devices is twice that of existing 802.3af devices, even with a 50% reduction in cable resistance. This power loss is greater for load systems that include connectors in the middle of the link. For this reason, the length confirmation of category 5 cables and the presence of connectors in the middle of the link represent more important factors, whereby more accurate decisions can be made regarding the power allocation to the ports than those based on estimating the worst-case power loss in the cable. For example, in an unloaded system, a cable length of 25 meters is determined, and then at a current of 700mA, the power loss is calculated to be (700mA)²2.5 Ω ═ 1.225W. This is much lower than the power loss of a 100 meter class 5 cable in a loaded system, which calculates the power loss as (700mA)²(10 Ω +2.5 Ω) ═ 6.125W. Of course, if the information V such as the correlation information is used_PSE、P_L、V_LAnd R_totThe estimated power loss in the cable will be further reduced by estimating the actual current.

For example, assume a 100 meter class 5 cable load system with connectors in the middle of the link. Wherein if V_PSEIs 50V, P_LIs 20W, R_tot＝R_cable+R_conWhen 10 Ω +2.5 Ω is 12.5 Ω, V can be calculated_L＝(50+/-SQRT(50²-4 × 20 × 12.5))/2 ═ (50+/-38.73)/2 ═ 44.36V. Followed by the use of V_PSE-V_L＝I*R_totThe current was calculated, i.e. 50V-44.36V-I12.5 Ω, resulting in I-0.451A. Here, the estimated power loss of the cable is I²*R_tot＝(0.451A)²12.5 Ω -2.54W, which can then be used to estimate the total power allocation to the ports: 20W + 2.54W-22.54W.

In another embodiment, assume P_LIs 20W, R_totDetermined as 5 omega (50 meters, 5 lines, no load), known V_LIs 48V. It will be appreciated that V may be transmitted using different communication methods, e.g. some forms of layer 2 communication_LFrom the PD to the PSE. In this example, the current I ═ P can be calculated_L/V_L20W/48V-0.417A. The estimated power loss of the cable is I²*R_tot＝(0.417A)²5 Ω -0.87W, which can then be used to estimate the total power allocation 20W + 0.87W-20.87W to the ports.

In addition, for PoE + devices, information on the cable type can also be obtained, which facilitates the calculation of power loss. Here, determining that an ethernet cable is better than a category 5 cable (e.g., a category 6 or 7 ethernet cable) may reduce the estimation of the cable resistance, thus further reducing the estimated power loss.

A third application in accordance with the principles of the present invention is PoE-extension (PoE-BR) applications. In PoE-BR applications, more than 100 meters of ethernet cable may be used to connect the PD to the PSE. For example, PoE-BR applications are defined to support distances of 500 meters and more.

In PoE-BR applications, determining the type of ethernet cable may be helpful to extend existing PoE applications. Consider, for example, a worst case 802.3af application that powers a PD over a 100 meter class 5 cable. In this worst case application, the resistance of the cable is about 20 Ω. If a category 5 cable is used instead, the lower resistance of the category 5 cable may allow the use of a longer category 5 cable, maintaining a resistance of 20 Ω. For example, assume a worst case category 5 cable, i.e., having a connector in the middle of a link. In this case, the resistance of the ethernet cable is about 12.5 Ω. Under this estimate, the length of a category 5 cable can be extended to 100m by 20 Ω to 160m, and matched to a resistance of 20 Ω. Further, if it is determined that there are no connectors in the middle of the link, the length of the category 5 cable may be extended to 100m by 20 Ω/10 Ω to 200m, and matched to a resistance of 20 Ω. Thus, without knowledge of PoE system operation information, certain factors (such as cable type and presence of link intermediate connectors) may cause a PD to be powered at lengths in excess of 100 m.

Generally, an increase in the distance between the PSE and the PD (e.g. up to 500m) may create a wider range for potential operation in a PoE-BR system. This operating range makes it more difficult to provide system specifications using worst case operating parameters. For example, assume that the PoE-BR specification supports class 3 cables. In dealing with this, the resistance of the cable may be specified to be 20 Ω to 100 Ω. Clearly, assuming a 100 Ω worst case cable resistance, it would not be feasible to determine a power distribution (such as that listed in table 1). Since the cable resistance is specified to be 10 Ω to 50 Ω, the same is true for the category 5 cable specification.

Therefore, one feature of the present invention is: PD powering in PoE-BR applications is based at least in part on the consideration of a particular port device. For example, suppose V is known_PSEIs 51V, the PD will consume constant power 12.95W, and the voltage of the PD is 37V. In this example, the calculated current is I ═ P_L/V_L12.95W/37V-0.34A. Then, the maximum resistance of the cable is calculated as R_tot＝(V_PSE--VL)/I＝(51V-37V)/0.34A＝41Ω。

Plus the maximum resistance R_tot41 Ω, the PoE-BR system can determine whether a particular port can fit the device. For example, if it is determined that a category 3 cable is used, the PD can be powered up to a distance of about 205 meters. Similarly, if it is determined that a category 5 cable is used, assuming a no-load system, the PD can be powered up to a distance of about 410 meters.

Determining the presence of a link intermediate connector may also affect these acknowledgements. For example, if a category 5 cable is used, then the maximum resistance R_totCan be decomposed into R_cableAnd R_con. If R is_con2.5 Ω, then the maximum resistance is resolved to R_cableWill be 41 Ω -2.5 Ω -38.5 Ω. In this example, when a category 5 cable is used, the PD can be powered up to a distance of about 385 meters.

The cable length and presence information of the connector may also be used to determine the power loss of the cable. For example, if it is determined that a category 5 cable is 375 meters in a load system, the resistance of the cable will be approximately 37.5 Ω +2.5 Ω -40 Ω. The power loss can then be calculated as P_loss＝(340mA)²40 Ω -4.62W. The total power allocation to the ports is 12.95W + 4.62W-17.5W.

Note that as above, the power allocation of the ports is very different due to the range of distances served by the PoE-BR application. For example, if a 120m category 5 cable is used in an unloaded system, the resistance of the cable is approximately 12 Ω. Then, the power loss is calculated as P_loss＝(340mA)²12 Ω ═ 1.39W. The total power supply to the port is 12.95W + 1.39W-14.34W. The difference between the power supplies in both cases (i.e. 17.57W-14.34W) is 3.23W, which helps to understand the relevant factors (e.g. cable type, cable length, and presence of link intermediate connectors) rather than relying on basic worst case assumptions.

Since the range of cable resistances is large in PoE-BR applications, the minimum voltage of the PD is smaller compared to the existing 802.3 afPoE. For example, assume that the minimum voltage of the PD is as low as 30V. This 30V value can be used to validate a given port device when the cable type information, cable length information, and the presence of the link intermediate connectors are known. It should be noted that PDs have higher requirements on the docking voltage than the minimum voltage. This is because the PD does not get all the energy during the turn-on process, and therefore the voltage of the PD is almost the same as the PSE.

Suppose V_PSE＝50V、P_L12.95W, and R_tot45 Ω (425 m category 5 cable in the load system). For this set of operating parameters, V is calculated_LI.e. V_L＝(50+/-SQRT(50²-4 × 12.95 × 45))/2 ═ 48+/-13)/2 ═ 30.5V. In calculating V_LThereafter, based on the minimum voltage, the PoE-BR system can determine whether the calculated voltage V is_LIs permissible. In this example, V_L30.5V, i.e. greater than the minimum threshold, the PoE-BR system can therefore validate the port under these operating conditions. With respect to power allocation to ports, V is used_PSE-V_L＝I*R_cableThe current was calculated so that 50V-30.5V ═ I × 45 Ω resulted in I ═ 0.433A. The power loss I in the cable can be calculated²*R_cablc＝(0.433A)²45 Ω -8.44W. In this example, the total power allocation of the PSE ports is 12.95W +8.44W — 21.39W.

In accordance with the principles of the present invention, the excessive penalty effect of using worst case resistance in a PoE-BR link can be minimized. First, savings in power allocation to a particular port may be realized, thereby increasing the overall capabilities of the PSE. Second, the PSE may make the port device valid, but not including the case when using worst case cable resistance estimation.

A fourth application in accordance with the principles of the present invention may be applied to general diagnostics of cable infrastructures. The diagnosis is completely unrelated to the PoE application. Generally, diagnostic tools are applicable to the cable infrastructure to determine the capabilities of the cable infrastructure for a given application. In the previously discussed application, a diagnostic tool is used to determine the cable infrastructure's ability to handle PoE-BR applications. In the same manner, diagnostic tools may be used to determine the capabilities of the cable infrastructure to handle an application, such as 10GBASET as defined by ieee802.3 an. Here, 10GBASET requires a type 7 ethernet cable. In accordance with the principles of the present invention, the diagnostic tool may determine all category 7 ethernet cables, and all below category 7 ethernet cables (e.g., category 5 or 6), so that 10GBASET communications may be handled. Also, by determining the presence of a connector, the diagnostics can determine if there are multiple cables in the link. The determination may further determine whether the cable link can handle a particular application.

Note that as above, measuring one or more characteristics of the ethernet cable may enable the PoE system to estimate the resistance of the ethernet cable link, and ultimately the actual power loss of the ethernet cable link. To facilitate this estimation, the PoE system can measure characteristics such as insertion loss, crosstalk, length, and interruption of the ethernet cable, among others. Measurements of insertion loss, crosstalk, length, and interruptions of an ethernet cable may represent examples of characteristics that may be used to estimate cable resistance, and therefore power loss in the cable.

In one embodiment, the cable length and break can be determined directly using TDR. In another embodiment, the length of the cable may be determined indirectly based on data generated when the insertion loss is measured using a reciprocating injection signal. Here, the time interval between the start and the reception of a pulse is linearly proportional to the cable length. Multiplying the propagation velocity by the time interval can calculate the cable length and then dividing by 2 yields the round trip delay. It will be appreciated that the presence of a connector can be inferred based on high frequency TDR measurements to identify a break (or obstruction) in the cable.

As described, different cable characteristics may be used to determine the cable type, cable length, and presence of a link intermediate connector. These factors enable the resistance and power loss of the cable link to be determined. It will be appreciated that other characteristics than those described above may be used in the PoE system to determine the resistance and power loss of the cable link. Regardless of which measurement data is used, it is important that the PoE system can use these data to dynamically adjust the configuration or operation of the PoE system. As previously described, the features of the present invention have application in a variety of contexts.

Fig. 5 is an embodiment of a PoE environment 500 capable of implementing the principles of the present invention. As shown, environment 500 includes PHYs 530-1 through 530-N, respectively, coupled to Ethernet switch 520. Although the PHY may include one or more Ethernet transceivers, only a single transceiver is shown connected to PHY 530-N. Each PHY is also connected to CPU 510, but for simplicity only one connection from CPU 510 to PHY530-N is shown. In one embodiment, CPU 510 is integrated with Ethernet switch 520 and PHYs 510 through 510-N onto a single chip. In another embodiment, the Ethernet switch 520 and PHYs 510-1 through 510-N are integrated onto a single chip and separate from the CPU 510, which communicates with the CPU 510 through a serial interface. In the PoE environment 500 as shown, the PSE 540 provides power via the center tap of the illustrated converter. As shown, PSE 540 may also be connected to CPU 510. In one embodiment, PSE 540 is connected to CPU 510 through opto-isolator 550, wherein opto-isolator 550 simplifies the isolation boundary.

To illustrate the operation of PoE environment 500 embodying the principles of the present invention, reference is now made to the flow chart of fig. 6. As illustrated in the flow chart of FIG. 6, beginning at step 602, a transceiver in PHY530-N measures the linear characteristics of an Ethernet cable connected to PHY 530-N. In one embodiment, measurements are taken during echo canceller (echo canceller) convergence performed by an echo canceller (echo canceller) module under control of CPU 510 to determine insertion loss, crosstalk, cable length, and interrupts. The linearity measurements made by the transceiver may then be sent to the CPU 510 at step 604.

Next, at step 606, CPU 510 uses the linear characteristic measurement data to determine the cable type, cable length, and the presence of connectors in the middle of the link. The cable type information, cable length information, and information about the presence of the intermediate connectors of the link are then sent to the PSE 540 at step 608. Here, it should be noted that the PSE may also use the linearity characteristic measurement data to determine the cable type, cable length, and presence of a connector.

Regardless of where the cable type, cable length, and presence of link intermediate connectors are determined, as long as available to the PSE 540, the PSE 540 may be caused to determine the relevant impact on PoE system configuration and/or operation. The determination of this effect may take into account the cable type, cable length, and presence of the link intermediate connector to derive the cable resistance and to other PoE system parameters such as V_PSE、P_L、V_LAnd so on. It will be appreciated that any system element that can diagnose an ethernet cable, determine whether to power a PD, determine power supply adjustments to a given PSE port, etc. can perform this impact analysis. Typically, the impact analysis is based on one or more parameters, such as cable link resistance, cable current, V_PSE、P_L、V_LThese parameters may be transmitted, discovered, and assumed by an appropriate system element. For example, one or more parameters may be obtained from one or more calculations using measurement data (e.g., cable resistance derived by determining cable type and length) or from knowledge of the parameters (e.g., V sent to the PSE by the PD) based on system specifications (e.g., IEEE802.3af)_L) Receives the above parameters.

While the invention has been described with reference to certain embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the spirit and scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.

Claims (7)

1. A power over ethernet system, comprising:

a powered device detection component to detect a presence of a powered device connected to a power device port by an Ethernet cable;

a cable detection component for measuring electrical characteristics of the Ethernet cable to determine the type of Ethernet cable, the length of the Ethernet cable, and the presence of an Ethernet cable intermediate connector;

a power controller for estimating the resistance of the Ethernet cable based on the type of Ethernet cable, the length of the Ethernet cable, and the presence of the Ethernet cable intermediate connector to assess the power loss of the cable to control the power distribution to the power equipment ports.

2. A power over ethernet system according to claim 1, wherein said cable detection component further measures a break in said ethernet cable.

3. A power over ethernet system according to claim 1, wherein said power controller controls power distribution based on the availability of said ethernet cable.

4. A method of power over ethernet, comprising the steps of:

determining, based on the measured electrical characteristics, a type of ethernet cable, a length of the ethernet cable, and a presence or absence of a connector in the middle of the ethernet cable, on a connection by the powered device to the power device port via the ethernet cable;

based on the type of ethernet cable, the length of the ethernet cable, and the presence of the ethernet cable intermediate connector, the resistance of the ethernet cable is estimated to evaluate the power loss of the cable to distribute power to the power source equipment ports.

5. The method of claim 4, wherein the determining step comprises measuring an interruption in the Ethernet cable.

6. A method of power over ethernet, comprising the steps of:

determining whether a connector is present in the middle of an Ethernet cable based on the measured electrical characteristics of the Ethernet cable, the Ethernet cable connecting a powered device to a power device;

determining whether to supply power to the power receiving apparatus based on the connector determining step;

based on the type of ethernet cable, the length of the ethernet cable, and the presence of the ethernet cable intermediate connector, the resistance of the ethernet cable is estimated to evaluate the power loss of the cable to distribute power to the power source equipment ports.

7. The method of claim 6, wherein the power determining step is used when an ethernet cable is greater than 100 meters.