Cascaded power-over-ethernet system

Abstract

A Power-over-Ethernet (PoE) device for use in a PoE system is described. The PoE device comprising a first PoE port for connecting the device to an upstream PoE device or a central control unit, a second PoE port for connecting the device to a downstream device or PoE device and a control unit for controlling data and/or power communication between the first and second PoE port. The control unit further comprises a first power input terminal connected to the first PoE port to receive electrical power for powering the control unit.

1 . A Power-over-Ethernet (“PoE”) device, the PoE device comprising:
 a first PoE port for connecting the device to an upstream PoE device or a central control unit; 
 a second PoE port for connecting the device to a downstream device or PoE device; 
 a control unit for controlling data and/or power communication between the first and second PoE port wherein the control unit comprises a first power input terminal connected to the first PoE port to receive electrical power for powering the control unit; 
 a power supply connected to the second PoE port for providing power to the downstream device and/or connected to a second power input terminal of the control unit for powering the control unit; 
 wherein a connection of the power supply to the second PoE port and/or a connection of the control unit to the first PoE port are controlled by the control unit; 
 wherein the control unit is arranged to operate the device in a first mode whereby the control unit is powered via the first PoE port and in a second mode whereby the control unit is powered by the power supply; and 
 wherein the power supply is disabled by the control unit when the device is operating in the first mode. 
 
     
     
         2 . The PoE device according to  claim 1  wherein the first PoE port is connected to the second PoE port for providing the electrical power to the second PoE port for powering the downstream device of PoE device. 
     
     
         3 . The PoE device according to  claim 1  wherein the device's operation in either the first or second mode is determined based on a power requirement of the device. 
     
     
         4 . The PoE device according to  claim 3 , wherein the control unit is arranged to operate the device in the first mode when the power requirement of the device is below a predetermined threshold. 
     
     
         5 . The PoE device according to  claim 1 , wherein the electrical power is provided as a power supply signal superimposed on a data signal. 
     
     
         6 . The PoE device according to  claim 5 , further comprising a first power splitter connected to the first PoE port and the control unit for separating the power supply signal from an input signal received at the first PoE port and providing the power supply signal to the first power input terminal. 
     
     
         7 . The PoE device according to  claim 6 , further comprising a second power splitter connected to the second PoE port and the control unit for combining the power supply signal and a further data signal to an output signal for the second PoE port. 
     
     
         8 . A PoE system for powering one or more devices, the system comprises:
 a central control unit having one or more output PoE ports;   one or more PoE devices according to any preceding claim, whereby the one or more output PoE ports are connected to resp. one or more first PoE ports of the one or more PoE devices.   
     
     
         9 . The PoE system according to  claim 8  wherein the central control unit is a server or a PoE device. 
     
     
         10 . Lighting application comprising:
 a PoE system according to  claim 8 ,   one or more lighting units connected to respective one or more second PoE ports of the one or more PoE devices.