PoE Powered Device Cable Resistance Measurement
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Solution Overview
Problem
In Power over Ethernet (PoE) systems, there is a discrepancy between the power allocated by the Power Sourcing Equipment (PSE) and the power consumed by the Powered Device (PD), resulting in excess power loss due to cable resistance, which is not efficiently utilized as the PD lacks information on additional power availability, necessitating costly and complex data communication between PSE and PD.
Innovation Solution
A PoE power utilization arrangement that includes a current path, a return path, a voltage detector, and a control circuitry to detect voltage and current at different times, calculate the resistance of the twisted wire pairs, and output an indication of the resistance, allowing the PD to adjust its power consumption based on the determined resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the PSE allocates power based on maximum cable resistance, then power allocation is conservative and reliable, but excess power is lost due to resistance and cannot be utilized
Solution Approach 1:
The PD performs self-measurement of cable resistance using its existing power reception circuitry. By detecting voltage during different time periods (with and without current flow), the PD calculates cable resistance autonomously without requiring additional measurement devices or communication with the PSE. This self-service approach eliminates the need for complex data communication while enabling efficient power utilization.
Solution Approach 2:
The PD performs voltage detection and resistance calculation during the classification phase, before final power allocation is established. This preliminary measurement of cable resistance allows the system to determine the actual power delivery conditions in advance, enabling optimized power consumption settings before the PD begins normal operation.
2Productivity
If data communication is added between PSE and PD to share resistance information, then power utilization can be optimized, but system complexity and cost increase
Solution Approach 1:
The PD autonomously measures cable resistance using its existing power reception circuitry during the classification phase. By detecting voltage at different time periods and calculating resistance internally, the PD eliminates the need for additional communication protocols or devices. This self-service mechanism achieves efficient power utilization without increasing system complexity.
Solution Approach 2:
The existing power reception and voltage detection circuitry in the PD is used for dual purposes: both receiving power and measuring cable resistance. This multi-functionality approach allows the PD to perform resistance measurement without requiring dedicated measurement devices or additional communication infrastructure, thereby avoiding increased system complexity.
3Use of energy by moving object
If the PD consumes more power than its class rating, then excess power can be utilized, but safety and compliance with PoE standards are compromised
Solution Approach 1:
The PD dynamically adjusts its power consumption based on the measured cable resistance. Instead of using a fixed power consumption level based on class ratings, the PD modifies its power draw to match the actual power delivery capability determined by real-time resistance measurements. This dynamic adjustment ensures safe operation within actual delivery limits while maximizing utilization of available power.
Solution Approach 2:
The PD uses feedback from its own voltage detection and resistance calculation to control its power consumption. By continuously monitoring the voltage drop across the cable and calculating resistance, the PD receives feedback on actual power delivery conditions and adjusts its consumption accordingly, ensuring compliance with actual delivery capabilities while maximizing power utilization.
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
Enables efficient utilization of excess power by allowing the PD to adjust its power consumption according to the cable resistance, reducing power loss and optimizing power allocation without the need for additional data communication, thus overcoming the limitations of prior art PoE systems.
Implementation Method 1
detecting a first function of a voltage between a current path node and a current return path node during a first time period and during a second time period
Implementation Method 2
sensing a second function of a current flowing through the current path node and return path node during the second time period
Data Source
Figure 1
Figure 2A
Figure 2B
AI summary
A PoE power utilization method constituted of: detecting a first function of a voltage between a current path node (20) and a current return path node (30) during a first time period and during a second time period, the second time period different than the first time period; sensing a second function of the magnitude of a current flowing through the current path (70) during the second time period; responsive to the detected first time period voltage function, the detected second time period voltage function and the sensed second time period current magnitude function, determining a third function of a resistance seen by the current path (70); and outputting an indication of the determined resistance function.