Method of discrimination of a device as powerable through a LAN line and device for estimating electric parameters of a LAN line

摘要

PDs that can be supplied through the LAN line are discriminated from PDs that cannot be so supplied as a function of the resistance of the supply line and of the voltage drop caused by nonlinear elements in series therewith. The values of these two parameters are estimated by applying two distinct voltages to the supply terminals of the LAN line and sensing the relative steady-state currents absorbed by the power supply line, and by processing voltage and current values for estimating the resistance of the line and the voltage drop caused by nonlinear elements connected in series therewith.

主权项

1. A method of recognizing a device as being powerable through a local area network (LAN) line coupled thereto based upon electrical parameters seen from first and second terminals of the LAN line comprising:
applying a first voltage across the first and second terminals for a first time interval and sensing a first steady-state current; applying a second voltage different than the first voltage across the first and second terminals for a second time interval and sensing a second steady-state current; estimating a resistance of the LAN line based upon the first and second voltages, and the first and second steady-state currents; and switching a supply voltage of the LAN line from the second voltage to a third voltage and sensing a third steady-state current; estimating a capacitance of the LAN line seen from the first and second terminals, based upon the third steady-state current failing to reach a threshold, by at least sensing a duration of a time interval starting from the switching during which the third steady-state current is smaller than the first steady-state current, and estimating the capacitance based upon the time interval, the resistance of the LAN line, a voltage drop across a load coupled to the LAN line, and the second and third voltages; and recognizing the device as being powerable through the LAN line based upon the resistance of the LAN line, the capacitance of the LAN line, and the voltage drop across the load coupled to the LAN line.