GB2583752A

GB2583752A - Device and method for power supply control

Info

Publication number: GB2583752A
Application number: GB1906539.0A
Authority: GB
Inventors: Lagrange Pascal; Rousseau Pascal
Original assignee: Canon Inc
Current assignee: Canon Inc
Priority date: 2019-05-09
Filing date: 2019-05-09
Publication date: 2020-11-11
Also published as: GB201906539D0

Abstract

A method and controller for controlling powering of a Powered Device (PD), the controller comprising a first connection for receiving voltage and data from a Power Sourcing Equipment (PSE) and a second connection for supplying voltage to power the PD. The method comprising, when the controller is powered up after receiving voltage through the first connection: determining power requirements of the PD; and checking fulfilment of a powering condition for the PD, the powering condition is based on power requirements of the PD and of other PDs, if any, sharing a same power budget from the PSE with the PD; wherein supplying voltage over the second connection for powering the PD is performed only if the powering condition is fulfilled. Suitable for power over cable systems, such as Power over Ethernet (PoE) and Power over Coax (PoC), where the PSE is a device such as a network switch capable of providing (sourcing) power over a network cable. A plurality of PDs are interconnected by a cable segment and powered by a single PSE port, wherein the plurality of PDs share a same power budget from said PSE. Exchange of data is compliant with HomePlugRTM AV specifications.

Description

Intellectual Property Office Application No. GII1906539.0 RTM Date:22 October 2019 The following terms are registered trade marks and should be read as such wherever they occur in this document: HomePlug IEEE Intellectual Property Office is an operating name of the Patent Office www.gov.uk /ipo

DEVICE AND METHOD FOR POWER SUPPLY CONTROL

FIELD OF THE INVENTION

The present invention relates to a power over cable system. More specifically, the present invention relates to devices and methods for power supply management.

BACKGROUND OF THE INVENTION

In power over cable systems, such as Power over Ethernet (PoE) and Power over Coax (PoC), one or more devices are powered over network cables by a power sourcing equipment (PSE).

The PSE is a device such as a network switch capable of providing (sourcing) power over a network cable. A powered device (PD) refers to a device capable of being powered, and thus consumes energy when powered. Examples of powered devices include analog cameras, IP cameras including pan-tilt-zoom (PTZ) cameras, wireless access points (AP), and Vol P phones.

The power over cable technology avoids having separate data cables and power cables which would otherwise be needed to power the devices. This allows for more time and cost-efficient installation for installers. However, the power distribution over data cables suffers from limitations on the total power that can be carried, and from a significant power loss in the cables due to the relatively low carried voltage (e.g. a typical voltage being comprised between 48 and 56 V). As known in the art, the total power consumption on one network segment is the accumulation of the power consumption of each device and the power dissipated in the cable due to the resistivity of the cable (Joule effect).

A typical PoE PSE is an Ethernet switch device that connects and powers through one of its ports a single PD. As the PoE PSE knows exactly how much power it can deliver over the port, the PSE can check using the PoE protocol if it has enough power available to meet the power requirements of the PD attached to it.

However, when a plurality of PDs interconnected by a cable segment are powered by the PSE port, it's no longer possible to know the exact amount of power the PSE should deliver as the PSE cannot check individually the power requirements of each PD. Furthermore, as the dissipated power (aforementioned Joule effect) depends on the cable length, each PD receives different voltage, and hence different available power at its bounds.

Having in mind that the overall power budget for a given cable segment is limited (hence referring to a power segment), starting all the devices on the segment at once, without ensuring that this power budget is sufficient to meet the power needs of all the Powered Devices on the segment may lead to an unpredictable state, e.g. endless loop of shutdowns and reboots of the PDs, until one or more devices linked to the port is/are unplugged.

It may therefore be desired to prevent the system from entering such an unpredictable boot -that is to say, prevent an endless loop of shutdowns and reboots in case of a power overrun at the port level.

SUMMARY OF THE INVENTION

The present invention has been devised to address at least one of the foregoing concerns.

To that end, according to one aspect, the invention concerns a method performed by a controller for controlling powering of a Powered Device (PD) the controller comprising: a first connection for receiving voltage and data from a Power Sourcing Equipment (PSE); and a second connection for supplying voltage to power the PD; the method comprising, when the controller is powered up after receiving voltage through the first connection: determining power requirements of the PD; and checking fulfilment of a powering condition for the PD, the powering condition is based on power requirements of the PD and of other PDs, if any, sharing a same power budget from the PSE with the PD; wherein supplying voltage over the second connection for powering the PD is performed only if the powering condition is fulfilled.

The method thus allows for powered devices activation that reduces risks for causing unpredictable behaviors at system startup.

According to embodiments, checking fulfilment of the powering condition comprises: transmitting the PD power requirements to a master controller, the master controller collecting power requirements from PDs sharing a same power budget from the PSE; and receiving from the master controller a result of a power arbitration process indicating whether the powering condition is fulfilled or not.

In an implementation, the powering condition is fulfilled if the result of the power arbitration process indicates that the controller is allowed to supply voltage to the PD, and not fulfilled if the result indicates that the controller is not allowed to supply voltage.

According to embodiments, checking the powering condition comprises: transmitting the PD power requirements to controllers of other PDs sharing the same power budget of the PSE; receiving power requirements of the other PDs from their associated controllers; and running a power arbitration process considering the PD power requirements and the received power requirements of the other PDs; wherein the powering condition is fulfilled for the PD if a result of the power arbitration process indicates that the controller is allowed to supply voltage to the PD, and not fulfilled if the result indicates that the controller is not allowed to supply voltage.

In an implementation, a same power arbitration process is run by all controllers associated with PDs sharing the same power budget, thereby the controllers reach a same result in a distributed manner.

The method according to the first aspect wherein the transmitting and receiving are performed by exchanging data through the first connection. In an implementation, the exchange of data is compliant with HomePlug AV specifications.

According to embodiments, the exchange of data is performed using broadcast packets that propagate over a cable segment that connects all controllers with a port of the PSE, the controllers connected to the cable segment sharing a same power budget provided by the port of the PSE.

The method according to the first aspect wherein the second connection is a Power Over Ethernet (PoE) port that is configured to connect to an IEEE 802.3-2012-compliant PD.

According to embodiments, determining the PD power requirements comprises performing power classification of the PD according to the PoE classification routine.

According to embodiments, the power classification routine is preceded by a PoE detection routine to detect if the PD is connected to the second connection.

According to another aspect, the invention concerns a controller for controlling powering of a Powered Device (PD), the controller comprising: means for receiving voltage and data through a first connection from a Power Sourcing Equipment (PSE); means for supplying voltage over a second connection to power the PD; means for determining power requirements of the PD; and means for checking fulfilment of a powering condition for the PD, the powering condition is based on power requirements of the PD and of other PDs, if any, sharing a same power budget from the PSE with the PD; wherein supplying voltage over the second connection for powering the PD is performed only if the powering condition is fulfilled.

According to yet another aspect, the invention concerns a system comprising: a Power Sourcing Equipment (PSE) providing voltage and data over a first connection; a plurality of controllers connected through the first connection to the PSE and sharing a same power budget; a Powered Device (PD) connected to a controller through a second connection; wherein, when the controllers are powered up after receiving voltage through the first connection from the PSE, each controller is configured to: determine power requirements of the PD connected to the controller through the second connection; and check fulfilment of a powering condition for the PD, the powering condition is based on power requirements of the PD and of PDs connected to the other controllers; wherein supplying voltage over the second connection for powering a PD by a given controller is performed only if the powering condition is fulfilled by that given controller.

BRIEF DESCRIPTION OF THE DRAWINGS

Other particularities and advantages of the invention will also emerge from the following description, illustrated by the accompanying drawings, in which: Figure 1 schematically shows a power over cable system arrangement that is adapted to embed embodiments of the invention; Figure 2 is a functional block diagram illustrating an implementation example of a controller; Figure 3a is a flowchart illustrating operation of a controller according to embodiments of the invention; Figure 3b is a flowchart illustrating an exemplary implementation for checking fulfilment of the powering condition according to a distributed implementation; Figure 3c is a flowchart illustrating an exemplary implementation for checking fulfilment of the powering condition according to a centralized implementation; Figure 4 is a flowchart illustrating operation of a master controller according to general embodiments; Figure 5 is an exemplary implementation of an arbitration process; Figure 6 illustrates a group of messages that may be exchanged according to embodiments; and Figure 7a, 7b and 7c represent different exemplary arrangements of the power over cable system.

Note that same references are used across different figures when designating same elements.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

Figure 1 schematically shows a power over cable system arrangement 100 that is adapted to embed embodiments of the invention.

The system comprises a PSE 101 and a plurality of PDs 111, 121 and 131 connected to a port of the PSE 101 via controllers 110, 120 and 130 for controlling powering of the PDs. A controller may be embedded in a same device as its associated PD, or in a separate device, e.g. a PoC/PoE adapter.

The controllers have a first connection (port) for receiving voltage and data through cable 140 from the PSE and a second connection (port) for supplying voltage overs cables 150 to power the PDs.

The cable 150 between a controller and a PD may also transport data in combination with power. Cable 150 may be for example a CAT-5 cable for connecting Power over Ethernet (PoE) devices, e.g. compliant with IEEE 802.3-2012 specifications. Cable 150 may also take any other form or be of any other type, such as wires or conductive tracks if the controller and the PD are embedded in a same device or share a common printed circuit board.

The cable 140 may also be a CAT-5 cable for connecting Power over Ethernet (PoE) devices, or a Coax cable compliant with a similar or any other power over cable technology.

According to embodiments of the invention, the controllers act on behalf of the PSE to negotiate power requirements of the PDs and to control power delivery from each controller to its associated PD. Because all PDs draw their current from a same port of the PSE and share a same power budget, controllers are used to determine if enough budget is available to power the PDs and to arbitrate between PDs if necessary.

Controllers during their operation draw only low current and/or low voltage from the PSE so that only low power is necessary for them to operate and to determine which of the PDs in the system can be powered up.

Figure 2 is a functional block diagram illustrating an implementation example of a controller 200 corresponding to any one of the controllers 110 -130 of Figure 1.

The controller is capable of supplying voltage to an associated PD through a voltage and power connection for example. Control of the supplied voltage is performed by means of a CPU 210. The CPU 210 is also configured to exchange messages by means of a HomePlug AV bridge 230 with the associated PD, other controllers connected to the power segment and/or the PSE. A sensing Unit 220 may optionally be present to measure for example voltage and current at the first or the second connection. Figure 3a is a flowchart illustrating operation 300 of a controller according to embodiments of the invention.

At step S310, the controller may optionally detect the presence of a compatible PD. The detection feature eliminates powering and potentially damaging devices not intended for application of an operational voltage (e.g. a voltage in a range 48 -56 V) from the controller. The controller may first apply low test voltages (e.g. in a range 2 10 V), measure a reference resistance at the PD and, if a correct signature is presented, detect that the PD is capable of accepting power.

At step S320, the controller determines power requirements of the PD. Aim is to determine the necessary power to be allotted to the PD or range of powers acceptable by the PD to run its functions properly.

The power requirements may include a nominal power value for operating the PD, a minimal power value acceptable by the PD, an operational power range or a power class of the PD.

In a preferred implementation, determining the PD power requirements comprises performing power classification of the PD according to the PoE classification routine. For example, the classification routine applies a voltage between 14 V and 20 V to the input of the PD, which in turn draws a fixed current set by a resistance which value is dependent on the class. The controller measures the PD current to determine which of the available classes that the PD is signaling.

At step S330, the controller checks fulfilment of a powering condition for the PD. The powering condition is based on the determined power requirements of the PD and of power requirements of other PDs, if any, sharing, with the PD, a same power budget from the PSE. If the powering condition is fulfilled, the controller supplies voltage over the second connection for powering the PD (S340). Otherwise, the PD is not powered by the controller (S350).

Thus, according to embodiments of the invention, the controller does not automatically enable powering of the PD after the power requirements are determined, as it would be the case after a classification routine is performed in a conventional PoE system. This advantageously allows powering a plurality of PDs sharing a same power budget in a controlled manner, and prevents the system to enter into an unpredictable state. A further advantage is that, when using a PoE system, any conventional PoE PD can be used and controlled without a need for specific modifications; in fact, it may be sufficient to execute the flowchart 300 only at the controllers of a same power segment. Installation is made easier.

Checking fulfilment of the powering condition S330 may be performed by each controller 110 -130 (distributed approach) or for the set of controllers 110 -130 by a master controller (centralized approach), to which the power requirements are transmitted.

In a distributed implementation, the controller receives from other controllers of the power segment power requirements of the PDs associated with those other controllers, runs a power arbitration process considering the PD power requirements and the received power requirements of the other PDs, and decides whether the powering condition for the PD is fulfilled or not based on the result of the arbitration process. In a centralized implementation, the controller provides the determined power requirements to a master controller, the master controller collects power requirements from different controllers and arbitrates between PDs sharing a same power budget, and the master controller sends back to the controller the result of the arbitration indicating whether the powering condition is fulfilled or not.

Figure 3b is a flowchart illustrating an exemplary implementation for checking fulfilment of the powering condition (step S330) according to a distributed implementation.

At step S331, the controller receives power requirements of other PDs from associated controllers. The controllers that communicate the power requirements of their associated PDs are those that intend to power up the PD. In other words, if the PD will not be powered up, and thus no power will be drawn from the PSE, either no power requirements are transmitted for that PD or power requirements indicating a zero-power need is transmitted.

At step S332, the controller transmits power requirements of the PD to other controllers in a same power (cable) segment, i.e. sharing a same power budget from the PSE. This step allows these other controllers to collect power requirements of all PDs so that each controller can run locally the arbitration process and decide in a distributed manner if it should supply voltage to its associated PD or not.

Note that step S332 is optional. In fact, in an implementation of the invention, the PDs of a power segment sharing a same power budget may be divided into two groups; a first group of PDs that have to be powered anyway and a second group PDs that are powered only if there is enough power budget left. For example, the first group corresponds to all PDs that are already powered up and running and the second group corresponds to new PDs added to the power segment and not powered yet. While the controllers associated of PDs of the second group need to receive power requirements of all other PDs, it is enough to transmit the power requirements of the PD to the controllers associated with the other PDs of the second group, and if the second group contains only one PD, e.g. addition of only one PD, no transmission of the power requirements of the PD has to be performed.

Transmission and reception of power requirements may be performed via unicast or broadcast messages exchanged through the data network using for example HomePlug AV protocol (cf. Figure 6 for exemplary message formats).

At step S333, the controllers run an arbitration process to determine if the controller is allowed to supply voltage to its associated PD or not. An exemplary implementation of the arbitration process is provided with reference to Figure 5. If controller is allowed to supply voltage as a result of the arbitration process, the powering condition is considered fulfilled (step S335), otherwise the powering condition is considered as not fulfilled (step S336).

Figure 3c is a flowchart illustrating an exemplary implementation for checking fulfilment of the powering condition (step S330) according to a centralized implementation.

The master controller may be located at the PSE, in a dedicated device or elected among the controllers 110 -130 connected to the power segment.

If the master controller is elected among the controllers, any election method can be used that results into selecting one controller. For example, the controller (or associated PD) with the lowest or highest address can be selected as the master controller. In a variant, the controllers cooperate to determine the resistive structure of the power segment (for example using a method described in W02018007363A1), and the controller with the lowest cable resistance to the PSE or the lowest power drop is selected. In a further variant, each controller measures the voltage at its bounds (using for example sensing unit 220 in Figure 2) and determines an activation timeout based on the measured voltage. Because the voltage measured at the input of each controller is different due to the resistive nature of the network, so are the timeouts derived from these voltages. The first controller which timeout expires is elected as master controller. The elected controller then notifies to other controllers so that they identify the master controller and deactivate their timers.

After the master controller is elected, the controller transmits the determined power requirements of the associated PD to the master controller (step S337), and receives result of a power arbitration process in return from the master controller (step S338). An exemplary implementation of the arbitration process is provided with reference to Figure 5.

In a variant, the controller transmits the determined power requirements to the master controller after reception from the master controller of a trigger message that indicates the start of the power control process for all controllers.

Similarly to the distributed approach, if the controller is allowed to supply voltage as a result of the arbitration process (test at step 5334a positive), the powering condition is considered fulfilled (step S335a), otherwise (test at step S334a negative) the powering condition is considered as not fulfilled (step S336a).

Transmission of power requirements to the master controller, reception from the master controller of the power arbitration process result, and optionally the reception of the trigger message may be performed via unicast or broadcast messages exchanged through the data network using for example HomePlug AV protocol (cf. Figure 6 for exemplary message formats).

Figure 4 is a flowchart illustrating operation 400 of a master controller according to general embodiments.

Optionally, the master controller may first execute an initial step (not illustrated) of sending a trigger message to controllers of the power segment that indicates the start of the power control process for all controllers. Hence, some controllers may be intentionally excluded from the process by the master controller, for example if their associated PDs are not to be powered on.

At step S410, the master controller receives, from the controllers, power requirements of their associated PDs. The master controller uses then these collected requirements to run a power arbitration process (S420) and sends back to the controllers the result of the arbitration process (S430).

Figure 5 is an exemplary implementation of an arbitration process 500 that may be run either by the controllers in the distributed approach (step S333) or the master controller in the centralized approach (step S420). Either one of these controllers running the arbitration process is referred to as controller in the following description of the figure.

Aim of the arbitration process is to determine if there is enough power budget to power all PDs willing to power up, considering their power requirements. In addition, and optionally, a further aim of the process is to select a subset of PDs that can be powered if it is determined that not all PDs can be powered up.

At step S510, a test is performed to determine if all PDs can be powered. According to an implementation, the test comprises adding the maximum power consumption for all the PDs of the power segment, based on their power requirements, e.g. Power Class, and comparing the resulting maximum consumption to be consumed on the power segment to the global power budget available at the PSE.

In a variant, power dissipated into the power segment is considered, and the resulting maximum consumption is compared to a fraction of the global power budget available. The fraction may be fixed, e.g. 80% or 90%, or estimated based on the topology of the power segment, number of connected PDs and/or the resistance of the cable.

According to another implementation, the test comprises computing the cable resistance of the different parts of the power segment connecting the controllers (for example using the method described in W02018007363) and estimating the voltage drop that each PD powering would cause, and comparing if the remaining voltage sufficient to actually power the PDs, i.e. above a minimum voltage threshold for activating the PDs.

If test S510 is positive, indications are provided in the result of the arbitration process for indicating to each controller that it is allowed to supply voltage to its associated PD.

If test S510 is negative, the controller optionally selects a subset of PDs that can be powered (step S530), and indications are provided in the result of the arbitration process for indicating to each controller of the subset that it is allowed to supply voltage to its associated PD (step S540).

The subset selection may be arbitrary or performed according to predefined rules. For example, the controller may select the biggest subset of PDs, i.e. a subset that allows the maximum number of PDs to be powered on concurrently. In variant, the controller may select a subset of PDs that allows activating the PDs having the highest voltage at their input, i.e. the PDs that would be the less impacted by any sudden voltage drop that would occur on the power segment (due to new device insertion or to cable damage, for instance).

Figure 6 illustrates a group of messages 600 that may be exchanged according to embodiments.

In the embodiment shown in Figure 6, messages 610, 620 and 630 all comprise a source identification (ID) 601, a destination identification 602, and a message identification 603.

The source identification 601 identifies the entity emitting the message, such as the MAC or IP address of a controller or of the unit or device embedding the controller (such as the adapter unit).

The destination identifier 602 identifies the entity targeted by the message, such as the MAC or IP address of the controller or of the unit or device embedding the controller (such as the adapter unit).

The message identifier 603 uniquely identifies the type of the message.

It may be noted that in various embodiments, the source ID 601 or destination ID 602 may not be used, or a broadcast address is used.

Message 610 is used by a controller (source) to share the power requirements of its associated PD to another controller or to a master controller (destination).

Message 620 is used by a master controller (source) to share the result of the power arbitration to controllers (destination).

Message 630 is used by a master controller (source) to trigger start of the power control process at a controller (destination).

Figure 7a, 7b and 7c represent different exemplary arrangements of the power over cable system.

Figure 7a represents a power cable system 700a formed by one PoC (Powerover-Coax) power segment 710. The system 700a comprises a PSE 720 (also referred to as Receiver device, or rDEV) and PoC devices 730 connected to the power segment 710. The power segment 710 is connected to one port of the PSE. PoC devices 730 embed an adapter unit (also referred to as Adapter Edge device, or eDEV) and a powered device (PD) connected to the adapter unit by a PoE connection. Because the PoC device contains an adapter and a PD, it may also be referred to as an Edge system (eSYS). In this exemplary power cable system 700a, controllers according to embodiments of the invention are for example embedded in the adapter units.

Figure 7b represents a power cable system 700b formed by two PoC power segments 711 and 712. Power segment 711 has only one edge system connected to it (Adapter and PD) and although there is only one PD to be powered by the PSE over the segment, the adapter may still implement a controller according to embodiments of the invention. Only the power requirements of the PD are then considered. In a variant, the controller may check the number of other PDs present, and if no controller provides power requirements of other PDs, then the controller will use a conventional power negotiation. Power segment 712 has two PoC devices 731 and 732. PoC 732 is a native PoC device (also referred to as Terminal edge device) as it does not require a separate adapter to connect to the power segment. For this device 732, the controller according to the invention is embedded therein.

Figure 7c represents a power cable system 700c formed by two power segments; a PoE power segment 713 and a PoC power segment 714. A native PoE PD 25 733 is connected to the PoE power segment 713, and a PoC device (eSYS) 734 is connected to the PoC power segment 714.

Although the present invention has been described hereinabove with reference to specific embodiments, the present invention is not limited to the specific embodiments, and modifications which lie within the scope of the present invention will be apparent to a person skilled in the art. In particular different features from different embodiments may be interchanged, where appropriate. Many further modifications and variations will suggest themselves to those versed in the art upon referring to the foregoing illustrative embodiments, which are given by way of example only and which are not intended to limit the scope of the invention as determined by the appended claims.

Claims

CLAIMS1. A method performed by a controller for controlling powering of a Powered Device, PD, the controller comprising: a first connection for receiving voltage and data from a Power Sourcing Equipment, PSE; and a second connection for supplying voltage to power the PD; the method comprising, when the controller is powered up after receiving voltage through the first connection: determining power requirements of the PD; and checking fulfilment of a powering condition for the PD, the powering condition is based on power requirements of the PD and of other PDs, if any, sharing a same power budget from the PSE with the PD; wherein supplying voltage over the second connection for powering the PD is performed only if the powering condition is fulfilled.
2. The method of claim 1, wherein checking fulfilment of the powering condition comprises: transmitting the PD power requirements to a master controller, the master controller collecting power requirements from PDs sharing a same power budget from the PSE; and receiving from the master controller a result of a power arbitration process indicating whether the powering condition is fulfilled or not.
3. The method of claim 2, wherein the powering condition is fulfilled if the result of the power arbitration process indicates that the controller is allowed to supply voltage to the PD, and not fulfilled if the result indicates that the controller is not allowed to supply voltage.
4. The method of claim 1, wherein checking the powering condition comprises: transmitting the PD power requirements to controllers of other PDs sharing the same power budget of the PSE; receiving power requirements of the other PDs from their associated controllers; and running a power arbitration process considering the PD power requirements and the received power requirements of the other PDs; wherein the powering condition is fulfilled for the PD if a result of the power arbitration process indicates that the controller is allowed to supply voltage to the PD, and not fulfilled if the result indicates that the controller is not allowed to supply voltage.
5. The method of claim 4, wherein a same power arbitration process is run by all controllers associated with PDs sharing the same power budget, thereby the controllers reach a same result in a distributed manner.
6. The method of any one of claims 2 to 5, wherein the transmitting and receiving are performed by exchanging data through the first connection.
7. The method of claim 6, wherein the exchange of data is compliant with HomePlugAV specifications.
8. The method of claim 7, wherein the exchange of data is performed using broadcast packets that propagate over a cable segment that connects all controllers with a port of the PSE, the controllers connected to the cable segment sharing a same power budget provided by the port of the PSE.
9. The method of any one of above claims, wherein the second connection is a Power Over Ethernet, PoE, port that is configured to connect to an IEEE 802.3-2012-compliant PD.
10. The method of claim 9, wherein determining the PD power requirements comprises performing power classification of the PD according to the PoE classification routine.
11. The method of claim 10, wherein the power classification routine is preceded by a PoE detection routine to detect if the PD is connected to the second connection.
12. A controller for controlling powering of a Powered Device, PD, the controller comprising: means for receiving voltage and data through a first connection from a Power Sourcing Equipment, PSE; means for supplying voltage over a second connection to power the PD; means for determining power requirements of the PD; and means for checking fulfilment of a powering condition for the PD, the powering condition is based on power requirements of the PD and of other PDs, if any, sharing a same power budget from the PSE with the PD; wherein supplying voltage over the second connection for powering the PD is performed only if the powering condition is fulfilled.
13. A system comprising: a Power Sourcing Equipment, PSE, providing voltage and data over a first connection; a plurality of controllers connected through the first connection to the PSE and sharing a same power budget; a Powered Device, PD, connected to a controller through a second connection; wherein, when the controllers are powered up after receiving voltage through the first connection from the PSE, each controller is configured to: determine power requirements of the PD connected to the controller through the second connection; and check fulfilment of a powering condition for the PD, the powering condition is based on power requirements of the PD and of PDs connected to the other controllers; wherein supplying voltage over the second connection for powering a PD by a given controller is performed only if the powering condition is fulfilled by that given controller.