POE PSE MPS support for PSE voltage transients

Abstract

In one embodiment, an apparatus includes: a power over Ethernet (POE) interface for connection to a powered device (PD) through an Ethernet cable; and a control circuit. The control circuit is configured to: measure a voltage provided by the device through the Ethernet cable; determining that the voltage has dropped by at least a given voltage change; based on determining that the voltage has dropped by at least the given voltage change, determining whether a predetermined number of Maintenance Power Feature (MPS) signals have been missed within a given time frame; and determining that the PD is still connected to the device based on a determination that the predetermined number of MPS signals have not been missed within the given time frame.

Description

[0001] priority

[0002] This application claims priority to U.S. Provisional Patent Application No. 63 / 392,950, filed on July 28, 2022, the contents of which are hereby incorporated in their entirety. Technical Field

[0003] The present disclosure relates to Power over Ethernet (POE), and more particularly to POE PSE maintain power signature (MPS) support for power sourcing equipment (PSE) voltage transients. Background Art

[0004] POE can include delivering power as well as data over twisted pair Ethernet cabling. This can allow the cable to provide data connectivity and power from a power source (called a PSE) to a device (called a powered device (PD)). PD devices can include, for example, wireless access points (WAPs), Internet Protocol (IP) cameras, and Voice over Internet Protocol (VoIP) phones.

[0005] When the PSE is supplying power to the PD, the PSE may monitor the current drawn by the PD to ensure that the PD is still connected. The minimum current that the PD must draw to avoid being considered disconnected from the PSE is referred to as a maintain power signature (MPS) signal. A current spike or current instance drawn by the PD and observed by the PSE may be considered an MPS signal. This behavior may be defined by, for example, the IEEE 802.3bt standard, which further specifies the magnitude and duration of the MPS current drawn by the PD and observed by the PSE. For example, when the PSE has not seen an MPS signal for at least 400 milliseconds, the PSE may remove power from the POE cable connecting the PSE to the PD so that the cable disconnected from the PD does not remain powered.

[0006] The MPS signal can be defined as a current pulse received from the PD at the PSE that draws a certain amount of current in a minimum amount of time at a certain duty cycle. The amplitude, minimum pulse width, and duty cycle can be defined in various different POE standards or protocols and can vary with the assigned class, the ability of the PSE to support short (low duty cycle) or long (high duty cycle) MPS, and system characteristics such as cable resistance, DC / DC input capacitance, etc.

[0007] The inventors of the examples of the present disclosure have found that the PD may not issue MPS pulses in order to maintain power. Such devices may operate with relatively low power consumption compared to other PDs. Such devices may draw or absorb MPS pulses internally to maintain power. The PD device may have a current sink or resistor that the PD can control so as to appear to remain connected to the PSE. When such a circuit of the PD is activated but has a low load, the current generated may initially be mainly derived from the large-capacity capacitor of the PD. The inventors of the examples of the present disclosure have found that if the voltage supplied to the PD by the PSE (referred to as the PSE voltage) decreases rapidly during the MPS PSE, even if the PD, the diode bridge will be reverse biased and all current will be taken from the PD capacitor, and this can continue until the PSE and PD voltages become approximately equal. This can occur during a PSE power supply voltage transient, and in this case, even if the PD is supplying MPS current, the PSE can determine that there is no MPS current and the PSE can shut down the PD.

[0008] Examples of the present disclosure may address one or more of these issues.Examples of the present disclosure may address erroneous POE PSE port shutdowns in the event of a PSE voltage transient when the PSE is operating in MPS mode. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 An apparatus for POE according to an example of the present disclosure is illustrated.

[0010] Figure 2 is another illustration of an apparatus for POE according to an example of the present disclosure.

[0011] Figure 3 is another illustration of an apparatus for POE according to an example of the present disclosure.

[0012] Figure 4 is a diagram of a PD according to an example of the present disclosure.

[0013] Figure 5 is a timing diagram of the operation of a PD according to an example of the present disclosure.

[0014] Figure 6 is a graphical representation of example values ​​from experiments for a given cable, PD, and device 100 according to examples of the present disclosure.

[0015] Figure 7 is a graphical representation of how many allowed missed MPS pulses versus VPSE voltage drop may be allowed before determining that the PD should no longer be powered, according to an example of the present disclosure.

[0016] Figure 8is an illustration of an example method for POE MPS support for PSE voltage transients according to examples of the present disclosure.

[0017] Fig. 9 is an illustration of another example method for POE MPS support for PSE voltage transients according to examples of the present disclosure. DETAILED DESCRIPTION

[0018] Figure 1 An apparatus 100 for POE according to an example of the present disclosure is illustrated.

[0019] The device 100 may include an interface 102 configured to provide communication from the device 100 to any suitable electronic device, such as a PD 106. The interface 102 may be implemented in any suitable manner, such as by analog circuitry, digital circuitry, control logic, instructions executed by a processor in a memory, digital logic circuitry programmed by a hardware description language, an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), a programmable logic device (PLD), or any suitable combination thereof, whether in a single device or distributed across several devices. The interface 102 may be configured to provide communication in any suitable format, such as Ethernet. The PD 106 may be implemented as any suitable electronic device that receives its power from the device 100 at least in part via POE. The device 100 may be connected to the PD 106 via any suitable connection, such as an Ethernet cable 104.

[0020] The apparatus 100 may include a control circuit 108. The control circuit 108 may be implemented in any suitable manner, such as by analog circuitry, digital circuitry, control logic, instructions in a memory for execution by a processor, digital logic circuitry programmed by a hardware description language, an ASIC, an FPGA, a PLD, or any suitable combination thereof, whether in a single device or distributed across several devices.

[0021] The control circuit 108 may be configured to measure the voltage provided by the device 100 to the PD 106 and returned from the PD 106. The voltage provided by the device 100 to the PD 106 may be given as VPSE. Current may also be provided by the device 100 to the PD 106 and may be given as IPSE. Current may be returned from the PD 106 and may be given as IPSE. The voltage provided by the device 100 may be provided to the PD 106 via the interface 102 and the Ethernet cable 104. Similarly, the current returned from the PD 106 to the device 100 may be provided via the Ethernet cable 104.

[0022] The control circuit 108 may be configured to measure VPSE and IPSE by any suitable mechanism. An analog-to-digital converter (ADC) may sample VPSE. IPSE may be measured by a current sense resistor within the device 100.

[0023] The control circuit 108 may be configured to measure VPSE and determine whether VPSE has dropped by at least one given voltage change given by VTHRESHOLD. The voltage change may be given by VPSE1-VPSE2. The measurement may be performed periodically or on demand (such as every millisecond), but some sampling may occur faster or may occur every 1 millisecond-5 milliseconds. The voltage change may be a voltage drop. The first and second measurements of VPSE may be performed at any suitable time. The first and second measurements of VPSE may be continuous or may be non-continuous. The control circuit 108 may be configured to determine whether a predetermined number of MPS signals have been missed within a given time frame based on determining that a given voltage change has exceeded a threshold. The predetermined number may be given as MPS-THRESHOLD. The predetermined number of MPS signals may be greater than zero. The control circuit 108 may be configured to determine that the PD 106 is still connected to the device 100 based on determining that a predetermined number of MPS signals have not been missed within a given time frame.

[0024] The given time frame may have any suitable length. The voltage drop threshold may have any suitable value. The predetermined number of MPS signals that have been missed within a given time frame may have any suitable value. Furthermore, the predetermined number of MPS signals may be based on the value of the voltage drop and may vary depending on the value of the voltage drop.

[0025] Any suitable manner or mechanism may be used to determine the number of missed MPS signals. For example, a counter (not shown) may be used and the counter may be incremented by the control circuit 108 at each point in time when an MPS signal is expected but not received. If a predetermined number is reached, the control circuit 108 may make an appropriate determination. In another example, a wait time before determining whether a predetermined number of MPS signals have been missed may be equal to the predetermined number multiplied by the total cycle time of a given MPS signal. In such an example, the control circuit 108 may wait for such a wait time to determine whether an MPS signal has been received without explicitly counting the missed MPS signals, as such a wait time may implicitly reflect such a number of missed MPS signals.

[0026] Thus, even if MPS signals are missed, control circuit 108 may cause device 100 to continue to power PD 106, at least for a given count of missed MPS signals greater than zero. Additionally, control circuit 108 may measure VPSE and determine a voltage drop, and based on the value of the voltage drop, determine the number of MPS signals allowed to be missed at device 100 before powering down PD 106. Thus, device 100 may not erroneously shut down PD 106 in the event of a voltage drop.

[0027] Figure 2 is another illustration of an apparatus 100 for POE according to an example of the present disclosure.

[0028] The control circuit 108 may be configured to determine VPSE and VPSE. The control circuit 108 may be configured to determine whether VPSE has dropped by at least one given voltage variation given by VTHRESHOLD. The voltage drop may be given by VPSE1-VPSE2. The control circuit 108 may be configured to determine whether a predetermined number of MPS signals have been missed within a given time frame based on determining that a given voltage variation has exceeded a threshold. The predetermined number may be given as MPS-THRESHOLD. The predetermined number of MPS signals may be greater than zero. The control circuit 108 may be configured to determine that the PD 106 is disconnected from the device 100 based on determining that a predetermined number of MPS signals have been missed within a given time frame.

[0029] The given time frame may have any suitable length. The voltage drop threshold may have any suitable value. The predetermined number of MPS signals that have been missed within a given time frame may have any suitable value. Furthermore, the predetermined number of MPS signals may be based on the value of the voltage drop and may vary depending on the value of the voltage drop.

[0030] Any suitable manner or mechanism may be used to determine the number of missed MPS signals. For example, a counter (not shown) may be used and the counter may be incremented by the control circuit 108 at each point in time when an MPS signal is expected but not received. If a predetermined number is reached, the control circuit 108 may make an appropriate determination. In another example, a wait time before determining whether a predetermined number of MPS signals have been missed may be equal to the predetermined number multiplied by the total cycle time of a given MPS signal. In such an example, the control circuit 108 may wait for such a wait time to determine whether an MPS signal has been received without explicitly counting the missed MPS signals, as such a wait time may implicitly reflect such a number of missed MPS signals.

[0031] Figure 3is another illustration of an apparatus 100 for POE according to an example of the present disclosure. The apparatus 100 is illustrated with a counter 110 configured to count missed MPS signals. The counter 110 may be implemented in any suitable manner and may be implemented within the control circuit 108 or outside the control circuit.

[0032] The control circuit 108 may be configured to determine VPSE and VPSE. The control circuit 108 may be configured to measure VPSE1 and VPSE2 and determine whether VPSE has dropped by at least one given voltage change given by VTHRESHOLD. The voltage change may be given by VPSE1-VPSE2. The control circuit 108 may be configured to set the counter 110 to count missed MPS signals based on determining that a given voltage change has exceeded a threshold. If a given time cycle of an expected MPS signal from the PD 106 has expired without receiving an MPS signal, it may be determined that the MPS signal has been missed. After setting the counter 110 to count missed MPS signals, the control circuit 108 may be configured to determine whether additional MPS signals have been received. If such additional MPS signals are received, the control circuit 108 may be configured to determine that the PD 106 is still connected to the device 100. If no additional MPS signals have been received, control circuit 108 may be configured to determine whether counter 110 has reached a predetermined number of MPS signals that may be missed within a given time frame (given as MPSTHRESHOLD). If counter 110 has reached MPSTHRESHOLD, control circuit 108 may be configured to determine that PD 106 is disconnected from device 100. MPSTHRESHOLD may be greater than zero.

[0033] Figure 4 is a diagram of a PD 106 according to an example of the present disclosure.

[0034] PD 106 may include a front-end connector 402. Connector 402 may be configured to receive VPSE from device 100 and provide IPSE to device 100. These portions may include transformer pairs to which the remainder of PD 106 may be tapped. Connector 402 may include two ports. In this disclosure, for simplicity, only the first port is discussed.

[0035] PD 106 may include a diode structure 404 implemented with any suitable number, type, and arrangement of diodes. Diode structure 404 may function as a diode bridge.

[0036] PD 106 may include transistor 414. Transistor 414 may be implemented by any suitable transistor. Transistor 414 may be configured to isolate PD 106 from PD load 106 during PD detection and classification.

[0037] PD 106 may include PD controller 406. PD controller 406 may be implemented in any suitable manner, such as by analog circuitry, digital circuitry, control logic, instructions in memory for execution by a processor, digital logic circuitry programmed by a hardware description language, ASIC, FPGA, PLD, or any suitable combination thereof, whether in a single device or distributed across several devices. PD controller 406 may also include resistor 410, transistor 408, and transistor 414. PD controller 406 may be configured such that an MPS signal is periodically generated. The MPS signal may be provided directly or indirectly to device 100 (when connected). PD controller 106 may cause transistor 408 (implemented in any suitable manner) to turn on during the MPS signal on time. This may cause a voltage source (such as VPSE) to be provided through resistor 410. This may cause current to flow out to device 100 as IPSE, which may flow through resistor 410.

[0038] PD 106 may include a bulk capacitor 412 connected in parallel with the load of PD 106 (given by PD load 416 ) and in parallel with diode structure 404 .

[0039] In other implementations, it may be necessary to implement the PD with limited or reduced size for bulk capacitors where PSE voltage transients may occur. For example, the TEXAS INSTRUMENTS PD IC TPS2373 may specify a maximum capacitance of 300uF for PSE voltage step drops below 0.4V, or a maximum capacitance of 120uF for larger voltage step drops such as 57V-50V. This is despite the fact that the POE specification allows such capacitors to be up to 360uF capacity. Therefore, as a practical matter, in other implementations, the size of the bulk capacitor is not as large as it could be. By limiting the capacitance value, performance may be reduced, and there may be unwanted and unknown connection requirements between a given PSE and a PD. In contrast, the examples of the present disclosure can remove the dependency between the device 100 (operating as a PSE) and the PD 106, and allow the PD 106 to use any value of the capacitor regardless of any PSE voltage transients.

[0040] A minimum duty cycle for the MPS may be specified for various implementations of the PD 106. In addition, the MPS pulse amplitude and width may be measured at the device 100 assuming the use of a maximum cable length and worst-case capacitance. Thus, some required timing may reflect the time and amplitude of the IPSE to be observed at the device 100.

[0041] During a voltage transient that affects the available voltage supply in the PD 106, the diode bridge in the diode portion 404 of the PD 106 may become reverse biased, and the IPSE may not be generated by the VPSE within the PD 106, but rather by the bulk capacitor 412, which may otherwise cause the device 100 to believe that the IPSE is not present and shut down power to the PD 106. The PD 106 may include a current sink or resistor that it can control in the form of a resistor 410 and a transistor 408. When such a current sink or resistor is activated during a voltage transient, the current generated may initially be primarily derived from the bulk capacitor 412 rather than from the VPSE from the device 100 because the diode of the diode portion 404 is reverse biased. As the voltage of the bulk capacitor 412 drops, the PSE may draw more current from the device 100 until eventually the voltage from the bulk capacitor 412 and the VPSE have equalized and all current is drawn from the device 100. When VPSE drops rapidly in anticipation of an MPS signal, the device 100 may not see the associated IPSE spike because the diode bridge (such as the diode bridge in diode structure 404) may be reverse biased and all current may be drawn from bulk capacitor 412. Furthermore, this may continue until the voltage from bulk capacitor 412 and VPSE have equalized. This may describe a power supply voltage transient, and in this case, the MPS signal will not propagate to the device 100. In other implementations, the PSE will believe that there is no MPS current, and will shut down the PD even if the PD is still connected and sourcing MPS current. This may be a transient voltage spike or drop where the PD does not draw as much voltage from the PSE as the PD is actually using, and therefore may appear to be disconnected from the PD from the PD's perspective. This may cause the PSE to erroneously disconnect the PD from the power supply. However, the device 100 may avoid this problem by first detecting a voltage drop on the VPSE, and then allowing a certain number of missed MPS signals before determining to disconnect the PD 106 from the power supply.

[0042] Figure 5 is a timing diagram of the operation of a PD, such as PD 106 , according to examples of the present disclosure.

[0043] Graphs illustrating VPSE (as within PD 106), VPD (voltage across PD 106), the output of PD controller 406 or attempted MPS pulse, current through bulk capacitor 412, current IPSE output from PD 106 to device 100, PSE MPS detection at device 100, and an interpretation of whether an MPS signal has been received within a specified time frame.

[0044] As shown, the VPSE within the PD 106 may drop due to voltage transient conditions or due to changes in the total load VPSE on the power supply of the PSE. When VPSE drops, the bulk capacitor 412 may not allow the VPD to discharge suddenly, resulting in VPD being higher than VPSE and forcing the diode of the diode portion 404 to become reverse biased. The PD controller 406 may issue an MPS signal in the form of pulses. The time between such pulses may be less than a given constant. The constant may be given according to a specific standard followed by the device 100 or PD106 and may be given as tMPDO. The current through the bulk capacitor 412 may correspond to the pulses generated by the PD controller 406 output, but only when VPD is higher than VPSE minus the forward voltage of the diode portion 404. Such a forward voltage may typically be equal to twice the voltage drop (VD) of each diode of the diode bridge including the diode portion 404 (at least for passive diodes). The current drawn by the MPS generated in PD 106 may discharge bulk capacitor 412, causing VPD to decrease with each MPS pulse, corresponding to the MPS current magnitude and the bulk capacitor 412 capacitance value. The current IPSE applied to device 100 may follow the pulses generated to device 100 until VPD is discharged to an amount equal to VPSE minus the forward voltage of the diode of diode portion 404. As shown, the current applied to device 100 may not be performed after VPSE drops and until VPSE and VPD are again equal within VDB (the forward voltage of diode portion 404).

[0045] MPS detection on device 100 may detect the first pulse because the current applied from PD 106 to device 100 may match the amplitude or duration requirement. However, the next two pulses may be missed because no current may be applied from PD 106 to device 100. Two such time periods given by tMPDO may pass without receiving such current pulses at device 100. Therefore, in these time frames, MPS may be considered absent.

[0046] Once VPSE and VPD are equal within VDB, the diodes comprising diode bridge 414 will again become forward biased, and the MPS pulses provided by PD controller 406 may again cause current pulses to be emitted from PD 106 to device 100. Such current pulses may be received and detected at device 100, and MPS may be deemed to be present.

[0047] Thus, as shown, while PD 106 is still connected to device 100, MPS signals may be missed, and after some MPS signals are missed at device 100, MPS signals may return.

[0048] Figure 6 is a graphical representation of example values ​​from experiments for a given cable 104, PD 106, and device 100 regarding a drop in VPSE versus how much MPS signal may be missed before the MPS signal is restored from the PD 106 and device 100 according to an example of the present disclosure. Such analysis may be performed for other instances of cables 104, PDs 106, and devices 100, and Figure 6 The values ​​shown in are provided for demonstration purposes.

[0049] Each row shows a different possible voltage drop starting from the original value of VPSE, 56V. Figure 6 The arrangement of illustrates the behavior of additional rows of voltage drops of increasing magnitude, where each row increases the voltage drop by 0.2V. The second and third columns illustrate the VPSE values ​​and the associated VPSE voltage drops. The next five columns illustrate the durations of the next five MPS pulses received by the device 100. The next five columns illustrate whether the device 100 will miss such corresponding pulses. The next column is a repeat of the third column for reference. The last column records the missed pulses.

[0050] As shown in row 1, when VPSE is 56V and not falling, pulses may not be missed. Each pulse may be received at device 100 with a duration of 18.7ms and therefore may be detected and not missed. In row 1, pulses may not be missed.

[0051] Similarly, in row 2, the pulse may not be missed when VPSE is 56 V and drops 0.2 V. Even though the first pulse may have a shortened duration, it may be long enough to be detected.

[0052] However, in row 3, a pulse may be missed when VPSE is 56 V and drops 0.4 V. The duration of the first pulse may be shortened to 6.75 ms, which may be too short for detection.

[0053] In row 13, the second pulse may be missed when VPSE is 56 V and drops 2.4 V. The second pulse may be shortened to 5.32 ms, which may be too short for detection.

[0054] In row 23, when VPSE is 56 V and drops 4.4 V, the third pulse may be missed. The second pulse may be shortened to 3.47 ms, which may be too short for detection. In contrast, in row 22, immediately above row 23, when VPSE drops 4.2 V, the third pulse may have been 8.95 ms, which may have been long enough for detection.

[0055] Thus, according to such an example set, the control circuit 108 may be configured or programmed to determine how many MPS signals may be missed before disconnecting the PD 106, and the number of such MPS signals may be based on the voltage drop observed for the VPSE.

[0056] Figure 7 is a graphical representation of how many allowed missed MPS pulses versus VPSE voltage drop can be allowed before determining that the PD should no longer be powered, according to an example of the present disclosure. Figure 6 A collection of examples.

[0057] As shown, no missed MPS signal should be experienced for voltage drops between 0 V and 0.4 V. Thus, a missed MPS signal in the associated voltage drop should be handled in the normal manner, i.e., it should indicate to device 100 that PD 106 has been disconnected and power should be removed from PD 106.

[0058] For voltage drops between 0.4V and 2.4V, a single missed MPS signal may be experienced while PD 106 is still connected. Therefore, a single missed MPS signal with an associated voltage drop between 0.4V and 2.4V should not result in a determination that PD 106 has been disconnected, and only after detection of two missed MPS signals should it be interpreted at device 100 that PD 106 has been disconnected and power should be removed from PD 106.

[0059] For a voltage drop between 2.4V and 4.4V, two missed MPS signals may be experienced while PD 106 is still connected. Therefore, one or two missed MPS signals in the associated voltage drop between 2.4V and 4.4V should not result in a determination that PD 106 has been disconnected, and only after three missed MPS signals are detected should it be interpreted at device 100 that PD 106 has been disconnected and power should be removed from PD 106.

[0060] For voltage drops above 4.4 V, three missed MPS signals may be experienced while PD 106 is still connected. Thus, one, two, or three missed MPS signals with associated voltage drops above 4.4 V should not result in a determination that PD 106 has been disconnected, and only after detection of four missed MPS signals should it be interpreted at device 100 that PD 106 has been disconnected and power should be removed from PD 106.

[0061] Figure 8 800 is a diagram of an example method 800 for POE MPS support for PSE voltage transients according to an example of the present disclosure. The method 800 may be performed by any suitable mechanism or element (such as by the device 100 or the control circuit 108 therein). The method 800 may begin at any suitable step, such as 805. The steps of the method 800 may be repeated, omitted, performed in parallel, performed recursively, or performed in any suitable order relative to each other.

[0062] At 805, it may be determined whether a PD device, such as PD 106, is connected to a PSE apparatus, such as apparatus 100. If so, method 800 may proceed to 810. Otherwise, method 800 may return to 805.

[0063] At 810, VPSE (such as the VPSE supplied by a PSE device to a PD device) may be measured and averaged.

[0064] At 815, it may be determined whether the VPSE has dropped by at least a given amount. For example, the amount may be a range between ((n-1)*ΔV+offset) and ((n)*ΔV+offset). The possible range of VPSE may be divided into m segments, each segment being ΔV wide. The segments denoted by n are segments where one or more MPS signals may be missed without disconnecting or powering off the PD device. For example, in Figure 7 In the scenario identified in , ΔV may be 2V and the offset may be 0.4V. A drop between 0.4V and 2.4V may correspond to n=2. A drop between 2.4V and 4.4V may correspond to n=3. A drop above 4.4V may correspond to n=3. Out-of-range measurements above the set range may default to the case of n=3. For a given voltage drop, a lookup table or other similar data structure or mechanism may be used to determine the allowed number of missed MPS signals for a given voltage drop.

[0065] If yes, then method 800 may proceed to 850. Otherwise, method 800 may proceed to 820.

[0066] At 820, a typical MPS detection scheme may be employed. A timer may be started. At 830, it may be determined whether an MPS pulse or signal has been received. If so, the method 800 may proceed to 830. Otherwise, the method 800 may proceed to 840. At 840, it may be determined whether a specified time period (given as tMPDO) for an expected MPS pulse or signal has been reached. If so, the method 800 may proceed to 845. Otherwise, the method 800 may return to 830.

[0067] At 835 , it may be determined that the PD device is still connected. PSE operation and powering of the PD device may continue. Method 800 may return to 810 .

[0068] At 845 , it may be determined that the PD device is not connected. PSE operation and powering of the PD device may be shut down. Method 800 may return to 805 .

[0069] At 850, a modified MPS detection scheme may be employed in which one or more MPS signals may be missed without determining that the PD is disconnected. A timer may be set. A counter for counting missed MPS signals may be initialized.

[0070] At 855, it may be determined whether an MPS signal or pulse has been received. If so, method 800 may proceed to 835. Otherwise, method 800 may proceed to 860.

[0071] At 860, it may be determined whether a time period of an expected MPS signal has exceeded since the initialization or last update of the missed MPS signal count. The time period may be tMPDO, or may be tMPDO plus the expected duration of the MPS signal. The time period may be referred to as Tdelay. If yes, then method 800 may proceed to 865. Otherwise, method 800 may proceed to 870.

[0072] At 865, a count of missed MPS signals may be incremented.

[0073] At 870 , it may be determined whether the number of missed signals is n or more, or whether the total amount of time for n missed signals (given by (n+1)*Tdelay) has been exceeded. If so, method 800 may proceed to 845 . Otherwise, method 800 may return to 855 .

[0074] Method 800 may be modified so that specific values ​​or ranges of voltage drops associated with specific allowable missed MPS signals may be determined. For example, specific checks on ranges may be performed instead of the general form described in 815. These ranges may not be linearly spaced, so specific range checks associated with specific counts of MPS signals that may be safely missed may be used instead.

[0075] Fig. 9 8 is a diagram of another example method 900 for POE MPS support for PSE voltage transients according to an example of the present disclosure. Method 900 may be a more specific example of method 800. The example of method 900 may utilize Figure 6 Sample data for .

[0076] Method 900 may be performed by any suitable mechanism or element, such as by device 100 or control circuit 108 therein. Method 900 may begin at any suitable step, such as 805. The steps of method 900 may be repeated, omitted, performed in parallel, performed recursively, or performed in any suitable order relative to each other.

[0077] At 905, it may be determined whether a PD device, such as PD 106, is connected to a PSE apparatus, such as apparatus 100. If so, method 900 may proceed to 910. Otherwise, method 900 may return to 905.

[0078] At 910, a counter for missed MPS pulses or signals may be cleared or initialized.

[0079] At 915, VPSE (such as the VPSE supplied by a PSE device to a PD device) may be measured. The measurements may be averaged. The measurements may be compared to previous measurements to determine if the VPSE has dropped by a given amount.

[0080] At 920, it may be determined whether the voltage drop is within a first range. For example, it may be determined whether the voltage drop is between 0.4V and 2.4V. If so, method 900 may proceed to 925. Otherwise, method 900 may proceed to 930.

[0081] At 925, a threshold for missed MPS signals or pulses (such as MPS-THRESHOLD) can be set to one. This can enable a modified MPS detection scheme to be employed, where one or more MPS signals can be missed without determining that the PD is disconnected. The number of allowable missed MPS signals can be based on the voltage drop and can be determined by, for example, looking up a value in a lookup table. Method 900 can proceed to 955.

[0082] At 930, it may be determined whether the voltage drop is within a second range. For example, it may be determined whether the voltage drop is between 2.4V and 4.4V. If so, method 900 may proceed to 935. Otherwise, method 900 may proceed to 940.

[0083] At 935, a threshold for missed MPS signals or pulses (such as MPS-THRESHOLD) can be set to two. This can enable a modified MPS detection scheme to be employed, where one or more MPS signals can be missed without determining that the PD is disconnected. The number of allowable missed MPS signals can be based on the voltage drop and can be determined by, for example, looking up a value in a lookup table. Method 900 can proceed to 955.

[0084] At 940, it may be determined whether the voltage drop is within a third range. For example, it may be determined whether the voltage drop is greater than 4.4 V. If so, method 900 may proceed to 945. Otherwise, if no other ranges are considered, method 900 may proceed to 950.

[0085] At 945, a threshold for missed MPS signals or pulses (such as MPS-THRESHOLD) can be set to three. This can enable a modified MPS detection scheme to be employed, where one or more MPS signals can be missed without determining that the PD is disconnected. The number of allowable missed MPS signals can be based on the voltage drop and can be determined by, for example, looking up a value in a lookup table. Method 900 can proceed to 955.

[0086] At 950 , a typical MPS detection scheme may be employed by setting MPS-THRESHOLD to zero. Method 900 may proceed to 955 .

[0087] A timer may be started at 955. The timer may be set to a maximum time to wait for an MPS pulse or signal.

[0088] At 960, it may be determined whether an MPS pulse or signal has been received. If so, method 900 may proceed to 990. Otherwise, method 900 may proceed to 965.

[0089] At 965, it may be determined whether a specified time period (given as tMPDO) for an expected MPS pulse or signal has been reached, or where there has been a missed MPS signal. If so, method 900 may proceed to 970. Otherwise, method 900 may return to 960.

[0090] At 970, a missed MPS pulse counter may be incremented by one.

[0091] At 975, it may be determined whether a certain amount of MPS signals have been missed (or a time has passed since an MPS signal was received, such as a time equivalent to a certain amount of MPS signals). The number of MPS signals may be given by MPS-THRESHOLD, and may have been defined in 925, 935, 945, or 950. Thus, it may be determined whether a counter of missed MPS pulses or signals (or its equivalent time) is greater than or equal to MPS-THRESHOLD (or its equivalent time). If so, method 900 may proceed to 985. Otherwise, method 900 may proceed to 980.

[0092] At 980 , the MPS timer used to time the duration between MPS signals can be reset. Method 800 can return to 955 .

[0093] At 985 , it may be determined that the PD device is not connected. PSE operation and powering of the PD device may be shut down. Method 900 may return to 905 .

[0094] At 990 , it may be determined that the PD device is still connected. PSE operation and powering of the PD device may continue. Method 900 may return to 910 .

[0095] Examples of the present disclosure may include a device. The device may include a POE interface for connecting to a PD via an Ethernet cable. The device may include a control circuit. The control circuit may be communicatively coupled to the POE. The control circuit may be configured to measure a voltage provided by the device via the Ethernet cable. The voltage may be averaged. The voltage may be measured in subsequent measurements. The control circuit may be configured to determine that the voltage has dropped by at least a given voltage change. The control circuit may be configured to determine whether a predetermined number of MPS signals have been missed within a given time frame based on determining that the voltage has dropped by at least the given voltage change. The predetermined number of MPS signals may be greater than zero. The control circuit may be configured to determine that the PD is still connected to the device based on determining that the predetermined number of MPS signals have not been missed within the given time frame.

[0096] In conjunction with any of the above embodiments, the predetermined amount of the MPS signal may be based on the amount of the voltage drop.

[0097] In combination with any of the above embodiments, when the given voltage change is a first voltage change, the predetermined number of MPS signals may be a first MPS number, and when the given voltage change is a second voltage change, the predetermined number of MPS signals may be a second MPS number, wherein the first MPS number is less than the second MPS number, and the first voltage change is less than the second voltage change.

[0098] In combination with any of the above embodiments, when the given voltage change is a third voltage change, the predetermined number of MPS signals may be a third MPS number, wherein the third MPS number is greater than the second MPS number, and the third voltage change is greater than the second voltage change.

[0099] In conjunction with any of the above embodiments, the control circuit may be configured to determine that the PD is still connected to the device based on determining that a predetermined number of MPS signals have not been missed within a given time frame, wherein at least one MPS signal is missed within a given time frame.

[0100] In conjunction with any of the above embodiments, the control circuit may be configured to determine that a given voltage change is a transient voltage drop of the device based on determining that a predetermined number of MPS signals have not been missed within a given time frame.

[0101] In combination with any of the above embodiments, the control circuit can be configured to determine that a reverse biased diode in the PD prevents the MPS signal from reaching the device based on determining that at least one MPS signal is missed within a given time frame and a predetermined number of MPS signals have not been missed within a given time frame.

[0102] In combination with any of the above embodiments, when the given voltage change is a first voltage change, the given time frame may be a first duration, when the given voltage change is a second voltage change, the given time frame may be a second duration, and the first duration may be less than the second duration, and the first voltage change is less than the second voltage change.

[0103] In conjunction with any of the above embodiments, the control circuit may be configured to determine that the PD is disconnected from the device based on determining that a predetermined number of MPS signals are missed within a given time frame.

[0104] In conjunction with any of the above embodiments, the control circuit may be configured to count the missed MPS signals using a counter, thereby incrementing the count after an elapsed time for each MPS signal.

[0105] In combination with any of the above embodiments, the control circuit may also be configured to count the number of missed MPS signals according to the total time without the MPS signal.

[0106] In conjunction with any of the above embodiments, the control circuit may be configured to determine that the PD is still connected to the device based on determining that a predetermined number of consecutive MPS signals have not been missed.

[0107] Examples of the present disclosure may include a device having any of the elements of any of the embodiments described above. The device may include a counter configured to count missed MPS signals. The device may include a control circuit configured to determine that a voltage provided by the device to the PD has dropped by at least a given voltage change. The control circuit may be configured to set the counter to start counting missed MPS signals based on determining that the voltage provided to the PD has dropped by at least a given voltage change. The control circuit may be configured to determine whether additional MPS signals have been received. The control circuit may be configured to determine that the PD is still connected to the device based on determining that additional MPS signals have been received. The control circuit may be configured to determine whether the counter has reached a predetermined number of missed MPS signals based on determining that additional MPS signals have not been received. The control circuit may be configured to determine that the PD is disconnected from the device based on determining that the counter has reached the predetermined number of missed MPS signals.

[0108] Although examples have been described above, the present disclosure may have other variations and examples without departing from the spirit and scope of these examples.

Claims

1. A device, comprising: A Power over Ethernet (POE) interface, wherein the Power over Ethernet (POE) interface is used to connect to a powered device (PD) via an Ethernet cable; and A control circuit is communicatively coupled to the POE, the control circuit being configured to: measuring a voltage provided by the device through the Ethernet cable; determining that the voltage has dropped by at least a given voltage change; determining whether a predetermined number of maintain power signature (MPS) signals have been missed within a given time frame based on determining that the voltage has dropped by at least the given voltage variation, the predetermined number of MPS signals being greater than zero; and Based on determining that the predetermined number of MPS signals have not been missed within the given time frame, it is determined that the PD is still connected to the device. 2 . The apparatus of claim 1 , wherein the predetermined number of MPS signals is based on an amount of voltage drop.

3. The device according to any one of claims 1 to 2, wherein: When the given voltage change is a first voltage change, the predetermined number of MPS signals is a first MPS number; When the given voltage change is a second voltage change, the predetermined number of MPS signals is a second MPS number; and The first MPS number is smaller than the second MPS number, and the first voltage variation is smaller than the second voltage variation.

4. The device according to claim 3, wherein: When the given voltage change is a third voltage change, the predetermined number of MPS signals is a third MPS number; and The third MPS number is greater than the second MPS number, and the third voltage variation is greater than the second voltage variation.

5. The device of any one of claims 1 to 4, wherein the control circuit determines that the PD is still connected to the device based on determining that the predetermined number of MPS signals have not been missed within the given time frame, wherein at least one MPS signal is missed within the given time frame.

6. The device of any one of claims 1 to 5, wherein the control circuit determines that the given voltage change is a transient voltage drop of the device based on determining that the predetermined number of MPS signals have not been missed within the given time frame.

7. The device of any one of claims 1 to 6, wherein the control circuit determines that a reverse biased diode in the PD prevents the MPS signal from reaching the device based on determining that at least one MPS signal is missed within the given time frame and the predetermined number of MPS signals have not been missed within the given time frame.

8. The device according to any one of claims 1 to 7, wherein: When the given voltage change is a first voltage change, the given time frame is a first time duration; When the given voltage change is a second voltage change, the given time frame is a second time duration; and The first duration is less than the second duration, and the first voltage change is less than the second voltage change.

9. The device of any one of claims 1 to 8, wherein the control circuit determines that the PD is disconnected from the device based on determining that the predetermined number of MPS signals are missed within the given time frame.

10. A method comprising: Connect to the powered device (PD) via an Ethernet cable through the Power over Ethernet (POE) interface; measuring a voltage provided through the Ethernet cable; determining that the voltage has dropped by at least a given voltage change; determining whether a predetermined number of maintain power signature (MPS) signals have been missed within a given time frame based on determining that the voltage has dropped by at least the given voltage variation, the predetermined number of MPS signals being greater than zero; as well as Based on determining that the predetermined number of MPS signals have not been missed within the given time frame, it is determined that the PD is still connected to the device. The method of claim 10 , wherein the predetermined amount of the MPS signal is based on the given voltage change.

12. The method according to any one of claims 10 to 11, wherein: When the given voltage change is a first voltage change, the predetermined number of MPS signals is a first MPS number; When the given voltage change is a second voltage change, the predetermined number of MPS signals is a second MPS number; and The first MPS number is smaller than the second MPS number, and the first voltage variation is smaller than the second voltage variation.

13. The method according to claim 12, wherein: When the given voltage change is a third voltage change, the predetermined number of MPS signals is a third MPS number; and The third MPS number is greater than the second MPS number, and the third voltage variation is greater than the second voltage variation.

14. The method according to any one of claims 10 to 13, comprising: Based on determining that the predetermined number of MPS signals have not been missed within the given time frame, it is determined that the PD is still connected to the device, wherein at least one MPS signal is missed within the given time frame.

15. The method according to any one of claims 10 to 14, comprising: Based on determining that the predetermined number of MPS signals have not been missed within the given time frame, the given voltage change is determined to be a transient voltage drop of the device.

16. The method according to any one of claims 10 to 15, comprising: Based on determining that at least one MPS signal is missed within the given time frame and the predetermined number of MPS signals have not been missed within the given time frame, determining that a reverse biased diode in the PD blocks the MPS signal from reaching the device.

17. A method according to any one of claims 10 to 16, wherein: When the given voltage change is a first voltage change, the given time frame is a first time duration; When the given voltage change is a second voltage change, the given time frame is a second time duration; and The first duration is less than the second duration, and the first voltage change is less than the second voltage change.

18. The method according to any one of claims 10 to 17, comprising: Based on determining that the predetermined number of MPS signals are missed within the given time frame, it is determined that the PD has been disconnected from the device.

19. A device, comprising: A Power over Ethernet (POE) interface, wherein the Power over Ethernet (POE) interface is used to connect to a powered device (PD) via an Ethernet cable; and A control circuit is communicatively coupled to the POE, the control circuit being configured to: determining that a voltage provided by the device to the PD via the POE interface and the Ethernet cable has dropped by at least a given voltage variation; based on determining that the voltage has dropped by the given voltage change, determining whether a predetermined number of consecutive maintain power signature (MPS) signals have been missed, the predetermined number of MPS signals being greater than zero; and Based on determining that the predetermined number of consecutive MPS signals have not been missed, it is determined that the PD is still connected to the device.

20. A device, comprising: a counter for counting missed maintain power signature (MPS) signals; and A control circuit, the control circuit being used for: determining that a voltage provided by the apparatus to a powered device (PD) has dropped by at least a given voltage variation; setting the counter to begin counting missed MPS signals based on determining that the voltage supplied to the PD has dropped by at least a given voltage variation; determining whether an additional MPS signal has been received; determining that the PD is still connected to the device based on determining that an additional MPS signal has been received; determining whether the counter has reached a predetermined number of missed MPS signals based on determining that no additional MPS signals have been received; Based on determining that the counter has reached the predetermined number of missed MPS signals, it is determined that the PD is disconnected from the device.

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