Pulse-Width Fault Power Control for Human-Safe Energy Limiting
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Solution Overview
Problem
As power levels increase in applications like Power over Ethernet (PoE) and Powered Fiber Cable (PFC), there is a need to limit the energy delivered into a fault without reducing the amplitude of current pulses, to ensure safety and compliance with standards that prevent let-go or ventricular fibrillation.
Innovation Solution
A fault managed power system that progressively reduces the duration of current pulses instead of their amplitudes upon fault detection, using a predefined number of consecutive pulses or a maximum allowed fault interval, to limit cumulative effects below a predefined threshold.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If power levels are increased in PoE and PFC applications, then power delivery capability is improved, but the energy delivered into a fault increases creating safety hazards
Solution Approach 1:
The system uses periodic current pulses to deliver power over the cable. Upon fault detection, the controller modifies the pulse width (duration) of these periodic pulses, progressively reducing them over a predefined number of pulses while maintaining the periodic nature of power delivery. This allows continued power delivery at reduced energy levels during the fault condition.
Solution Approach 2:
The system changes the pulse width parameter of the current pulses in response to fault detection. The controller progressively reduces the pulse width from an initial value over a predefined number of pulses, thereby reducing the energy delivered into the fault while maintaining the same pulse amplitude and frequency, thus resolving the contradiction between power delivery and fault safety.
2Object-affected harmful factors
If the amplitude of current pulses is reduced to limit fault energy, then safety is improved, but power delivery capability deteriorates
Solution Approach 1:
The system dynamically adjusts the pulse width parameter based on fault detection and the current pulse number. The pulse width is progressively reduced over a predefined number of pulses and then restored to normal after the fault condition is resolved. This dynamic adjustment allows the system to maintain full power delivery capability under normal conditions while automatically limiting fault energy when needed.
Solution Approach 2:
The system is designed with predetermined parameters including the number of pulses over which to reduce pulse width, the reduction percentage, and the criteria for fault detection. These parameters are configured in advance to ensure that when a fault occurs, the system can immediately begin the pulse width reduction sequence to limit energy delivery before significant damage or harm occurs.
3Object-affected harmful factors
If pulse width is progressively reduced over multiple pulses, then fault energy is limited, but the system complexity increases
Solution Approach 1:
The system employs a feedback mechanism where the controller continuously monitors for fault conditions and adjusts the pulse width accordingly. When a fault is detected, the controller implements a predefined pulse width reduction sequence over a specific number of pulses. After the reduction sequence completes or the fault is resolved, the system restores normal pulse width. This feedback-based approach automates the complexity, making the control mechanism manageable despite the multi-step response.
Solution Approach 2:
The system is configured with predetermined parameters for fault response including the number of pulses for reduction, the reduction percentage, and restoration criteria. These actions are prepared in advance, so when a fault occurs, the controller simply executes the pre-planned sequence rather than calculating complex responses in real-time. This preliminary configuration reduces the operational complexity of the control mechanism.
Data Source
AI summary
A fault managed power system (FMPS) and method therefor can limit the cumulative effects of repeated current pulses on the human body during a fault without changing the amplitudes of the current pulses. Upon detection of a fault, the fault managed power system progressively reduces the durations of the current pulses (i.e., ON intervals) instead of the amplitudes to limit the cumulative effects of the current pulses. The fault managed power system can perform the progressive pulse width reductions in increments or steps that limit the cumulative effects of the current pulses to below a predefined energy level. In some embodiments, the predefined level is a level that could prevent let-go or cause ventricular fibrillation in a human body. Such a fault managed power system advantageously provides a simple and efficient way to limit the energy delivered into a fault without having to change the amplitudes of the current pulses.