Ethernet Midspan Current Balancing Circuit
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Solution Overview
Problem
The existing IEEE 802.3af standard for Inline Power delivery in Ethernet networks faces challenges in maintaining balanced current distribution across all four pairs of an Ethernet cable, leading to potential overcurrent conditions and incorrect detection of short circuits due to mismatches in direct current resistance, which can result in power shutdown.
Innovation Solution
The solution involves monitoring current levels and modulating the gate voltage of power FET switches to balance current flow between pairs, ensuring that no pair exceeds the 350 mA threshold, and implementing circuitry to dynamically adjust current levels to prevent overcurrent situations while maintaining power delivery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If power is delivered down all four pairs of an Ethernet cable, then the power delivery capability is improved, but over-current conditions occur due to resistance mismatches between pairs
Solution Approach 1:
The system performs preliminary classification of the powered device and allocates appropriate power levels before full power delivery begins. This prevents over-current conditions by establishing safe operating parameters in advance, allowing all four pairs to be utilized without triggering false short-circuit detections
Solution Approach 2:
The system continuously monitors current levels on each pair and provides feedback to the power sourcing equipment. When resistance mismatches cause current imbalance, the feedback mechanism allows the PSE to adjust power allocation dynamically, preventing over-current conditions while maintaining optimal power delivery across all four pairs
2Reliability
If current monitoring and control circuitry is added to balance current flow, then over-current conditions are prevented, but device complexity increases
Solution Approach 1:
The power sourcing equipment integrates multiple functions including classification, current monitoring, and control across all four pairs using a unified system architecture. This multi-functional approach prevents over-current conditions without requiring separate dedicated circuitry for each function, thereby limiting the increase in device complexity
Solution Approach 2:
The system uses the existing Ethernet infrastructure and embedded controllers to perform self-monitoring and self-regulation of current flow. The powered devices and power sourcing equipment work together autonomously to detect and correct current imbalances, reducing the need for additional external control circuitry
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 effectively prevents overcurrent conditions and maintains power delivery by balancing current flow between pairs, avoiding unnecessary shutdowns caused by resistance mismatches, thus ensuring reliable operation within the specified current limits.
Implementation Method 1
modulate the gate voltage of power FET switches
Implementation Method 2
employing existing integrated circuits to sense and adjust current levels
Data Source
AI summary
Methods and apparatus are disclosed for balancing power across all conductors of an Ethernet connection. Balancing circuitry is disclosed to allow an Ethernet midspan device to receive power from an Ethernet Power Sourcing Equipment (PSE) on the signal pairs of an Ethernet connection. The balancing circuitry is configured to sense the level of the received power, and generate a second power source substantially equal to the received power level. The received power is provided to an Ethernet Powered Device (PD) over the signal pairs of an Ethernet connection, and the generated power to the PD over the unused pairs of the Ethernet connection.