Dynamic Current Limits for PoE Power Sourcing Equipment
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Solution Overview
Problem
Power supplies in network devices can be overloaded by voltage spikes, leading to potential system shutdowns and data loss, especially in PoE and PoE+ configurations where devices draw excess current due to capacitor charging during rapid voltage changes.
Innovation Solution
Implement a method where Power Sourcing Equipment (PSE) allocates and provides power based on a worst-case current draw calculation, considering the capacitance of network devices and the maximum voltage slew rate, ensuring the remaining power capacity is sufficient to prevent overloading, and denying power if capacity is insufficient.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If per-port current is limited to 400 mA in traditional PoE, then power supply safety is maintained during voltage spikes, but the maximum power delivery capability is restricted
Solution Approach 1:
The patent implements dynamic current limiting that adjusts the per-port current threshold based on the total power consumed by all powered devices. When total power consumption is low, higher current thresholds are permitted; when total power consumption is high, lower current thresholds are enforced. This dynamic adjustment allows the system to safely handle voltage spikes while maximizing power delivery capability under normal operating conditions.
2Power
If PoE+ provides 720 mA continuous current per port, then power delivery capability is increased, but the system becomes vulnerable to overloading during voltage spikes
Solution Approach 1:
The patent calculates and tracks the worst-case current draw for each port in advance, considering the capacitance of connected devices and maximum voltage slew rates. This preliminary calculation establishes a safety margin before voltage spikes occur, allowing the system to allocate power aggressively during normal operation while automatically enforcing lower current thresholds when spikes are detected, thus preventing overloading.
3Device complexity
If power is allocated based on maximum specification limits, then simple allocation logic is used, but voltage spikes cause excess current draw and potential failures
Solution Approach 1:
The patent implements a feedback mechanism that continuously monitors total power consumption across all ports and adjusts per-port current thresholds accordingly. The system receives power consumption data from powered devices, calculates the remaining power capacity, and dynamically updates the current limiting thresholds. This closed-loop feedback allows the system to maintain reliability while optimizing power delivery, replacing static maximum-limit allocation with adaptive threshold adjustment.
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
Prevents system overloading and shutdowns by accurately determining the worst-case current draw during voltage spikes, allowing for safe operation of network devices without compromising the power supply capacity, thereby ensuring continuous functionality and data integrity.
Implementation Method 1
Because PDs typically contain capacitors, the rapid voltage change causes the capacitors to charge and therefore draw excess current
Data Source
AI summary
A method is provided for allocating and providing power to network devices. The method includes (i) receiving an electronic request to power a network device with a requested amount of power, (ii) establishing a worst-case current draw of the device in the event of a pre-defined maximum voltage slew rate, and (iii) selectively (a) allocating and providing power to the device when a remaining power capacity is greater than or equal to a provision voltage multiplied by the worst-case current draw of the device in the event of the maximum voltage slew rate, and (b) denying power to the device when the remaining power capacity is less than the provision voltage multiplied by the worst-case current draw of the device in the event of the maximum voltage slew rate. Apparatus are also provided for performing the method.