Power over Ethernet system having multiple power source devices and control device thereof

A control device for a power over Ethernet system having a plurality of power source devices, comprising:

• a plurality of control circuits, each connected to a plurality of power supply devices and a plurality of port switches, each port switch controlling a power consumption state of at least one port for connection by a power consuming device;
• wherein each control circuit comprises:
• an input terminal for connecting a plurality of power source devices;
• a detection circuit connected to the input terminal for receiving a power supply state combination signal representing a combination of power supply state of the plural power source devices;
• a first look-up-table memory to store a first power supply to power consumption look-up-table defining a corresponding relation of a plurality of power supply state combination and a plurality of maximum power consumption values;
• and
• a control signal generating circuit connected to the detection circuit and the first look-up-table memory and configured to:
• upon receipt of a power supply state change signal from the detection circuit, generate a power consumption control signal corresponding to the received power supply state combination signal and a corresponding maximum power consumption value in the first power supply to power consumption look-up-table and provide the power consumption control signal to the plurality of port switches for turning ON or OFF the port switches;
• wherein the detection circuit is configured to:
• upon detection of a received power supply state combination signal different from a previously received power supply state combination signal, generate a power supply state change signal;
• and
• a signal bus connecting the plurality of control circuits;
• the control device further comprising a master controller, wherein the master controller is equipped with a second look-up-table memory for storing a second power supply to power consumption look-up-table;
• wherein the second power supply to power consumption look-up-table defines a corresponding relation of a plurality of power supply state combination signals and a plurality of maximum power consumption values, indicating an upper limit of sum of power consumption allowable for all ports in connection with the plurality of control circuits, corresponding to each power supply state combination signal.