PoE PD Discrimination via Multi-Voltage Line Resistance Estimation
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Solution Overview
Problem
Existing Power over Ethernet (PoE) techniques often incorrectly recognize valid Powered Devices (PDs) as invalid or vice versa due to insufficient measurement of resistance at the Power Sourcing Equipment (PSE) outlet, particularly when nonlinear elements are connected, leading to errors in identifying whether a PD can be powered through the LAN line.
Innovation Solution
The method involves estimating the resistance and voltage drop of the LAN line by applying distinct voltages and sensing steady-state currents, and processing these values to determine the line's resistance and voltage drop caused by nonlinear elements, with an additional error term accounting for the linearity of the voltage-current characteristic, and also considering capacitance to reliably identify powerable PDs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If resistance measurement is performed by applying voltage and measuring current at PSE outlet, then power consumption is reduced and operation is simplified, but measurement precision deteriorates due to nonlinear elements causing erroneous PD identification
Solution Approach 1:
The measurement process is segmented into multiple distinct voltage application steps (e.g., first voltage level, second voltage level) rather than a single measurement. This allows the system to collect multiple data points (currents at different voltages) to characterize the nonlinear I-V curve, thereby improving measurement precision while maintaining low power consumption through controlled, sequential measurements
Solution Approach 2:
The system changes the voltage parameter across multiple measurement steps, applying different voltage levels to the LAN line and measuring the corresponding currents. By varying the voltage parameter and analyzing the resulting current responses, the system can distinguish between linear and nonlinear characteristics, improving PD identification accuracy without requiring continuous high-power operation
2Device complexity
If simple resistance measurement is used, then device complexity is reduced and operation is easier, but reliability deteriorates due to incorrect PD recognition
Solution Approach 1:
The system performs preliminary characterization measurements by applying multiple voltage levels and measuring currents before making the final PD validation decision. This preliminary action of collecting I-V data points allows the system to reliably detect nonlinear elements and correctly identify PDs, improving reliability without requiring complex real-time analysis hardware
Solution Approach 2:
The patent introduces an intermediary analysis step that processes the current measurements taken at different voltage levels. This intermediary processing (comparing measured currents with expected linear behavior) acts as a mediator between the simple measurement process and the final reliability decision, enabling accurate PD recognition through straightforward computational analysis
3Loss of time
If single voltage measurement is performed, then measurement time is reduced and productivity is improved, but measurement precision deteriorates due to inability to detect nonlinear elements
Solution Approach 1:
The measurement process uses periodic application of different voltage levels in a structured sequence (first voltage, then second voltage, etc.). This periodic action allows the system to efficiently collect multiple measurement points in a time-discretized manner, achieving precise nonlinear element detection through rapid sequential measurements rather than continuous monitoring
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances the reliability of recognizing powerable PDs by providing more accurate electrical parameter estimation, reducing incorrect identifications and ensuring compliance with PoE specifications, even for pre-standard devices and future voltage ratings.
Implementation Method 1
measuring the resistance seen across the terminals through which the PSE supplies the LAN line, for example by applying a voltage across the pair of power supply conductors of the LAN line and measuring the current absorbed
Implementation Method 2
the PSE supplies power to the PD devices connected to respective sockets through a dedicated pair of insulating wires of the connecting cable. In particular, the PSE verifies whether a PD is connected to a LAN line, and monitors the current delivered to the LAN line of the PD continuously
Data Source
AI summary
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.