Power Sourcing Equipment Cable Resistance Determination
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Solution Overview
Problem
In Power over Ethernet (PoE) networks, imprecise determination of Ethernet cable resistance leads to inefficient power allocation, as Power Sourcing Equipment (PSE) may cease or reduce power to devices due to estimated power loss, resulting in suboptimal performance and potential underpowering of devices.
Innovation Solution
A Power Sourcing Equipment (PSE) with a current modulation circuit that applies different supply voltages through multiple pairs of wires in the Ethernet cable, using a variable resistance switch to create an offset voltage, allowing for accurate determination of cable resistance and precise power allocation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If time domain reflectometry is used to estimate cable resistance, then power loss can be determined, but the measurement precision is insufficient leading to imprecise power allocation
Solution Approach 1:
The patent changes the measurement parameters by applying multiple different voltage levels (first voltage, second voltage, third voltage) to the cable pairs and measuring the corresponding currents. This multi-parameter approach enables accurate resistance calculation through current modulation and offset voltage measurement, resolving the precision issue without requiring complex external measurement equipment.
Solution Approach 2:
The PSE uses its own power supply and current modulation circuits to perform resistance measurement, eliminating the need for separate measurement devices. The system serves itself by using the power delivery infrastructure to simultaneously perform both power allocation and resistance measurement functions.
2Reliability
If worst-case scenario estimation is used for power allocation, then power efficiency is maintained, but power allocation accuracy deteriorates causing underpowering of devices
Solution Approach 1:
The patent implements feedback by measuring the actual currents flowing through different cable pairs at multiple voltage levels, then using this measured data to calculate actual resistance values. This feedback mechanism replaces worst-case estimation with real-world measured data, ensuring reliable power allocation matched to actual cable conditions.
Solution Approach 2:
The resistance measurement is performed before final power allocation decisions are made. By conducting the measurement in advance using the current modulation technique, the system obtains accurate cable resistance data that informs subsequent power budgeting and allocation, preventing both underpowering and overpowering scenarios.
3Power
If all four pairs of wires are utilized for power application, then higher current support is achieved, but cable loss increases requiring more accurate resistance determination
Solution Approach 1:
The patent segments the power delivery measurement into three distinct voltage levels applied to different cable pair configurations. By measuring currents at each voltage level separately and calculating resistance for each segment, the system achieves precise characterization of power loss across all four cable pairs, enabling optimized power allocation that maximizes current capacity while minimizing energy loss.
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 method enables accurate resistance determination and improved power allocation, supporting higher currents with reduced cable loss, ensuring efficient power delivery to devices in PoE networks.
Implementation Method 1
a current modulation circuit offsetting所述第二电流 from所述第一电流 to create an offset voltage between所述第二 and所述第一 supply voltages to determine所述 resistance of所述 powered cable
Data Source
AI summary
An exemplary implementation of the present disclosure is a power sourcing equipment (PSE) for determining a resistance of a powered cable. The PSE includes a first supply voltage to cause a first current to flow through first and second output terminals of the PSE. The PSE also includes a second supply voltage to cause a second current to flow through third and fourth output terminals of the PSE. The PSE further includes a current modulation circuit offsetting the second current from the first current to create an offset voltage between the second and the first supply voltages to determine the resistance of the powered cable. The current modulation circuit can offset the second current from the first current utilizing a variable resistance switch to adjust the second current.