Forced Bulk Capacitor Discharge in Powered Devices
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Solution Overview
Problem
In power distribution systems, especially those using Power over Ethernet (PoE), energy inefficiencies arise from minimum power consumption requirements for maintaining a 'keep alive' signal in standby mode, leading to power losses that accumulate significantly in large installations, as the low current drawn by devices may not be detectable by the power supply, potentially causing disconnection.
Innovation Solution
A method and device that measure the voltage over a capacitor in a Powered Device (PD) to control current draw, ensuring that a first current is drawn until the voltage decreases, then switching to a second current that meets the minimum requirements, ensuring power is drawn from the Power Sourcing Equipment (PSE) while minimizing losses, by using a controller to manage current pulses and voltage measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the minimum current draw requirement is set to a very low value to reduce power losses, then energy efficiency is improved, but the current becomes undetectable at the power supply side
Solution Approach 1:
The patent implements periodic Maintain Power Signature (MPS) current pulses instead of continuous current draw. The PD draws current in periodic pulses (e.g., 10 mA for 7.5 ms every 325 ms), allowing the system to meet minimum power consumption requirements while enabling detectable periodic signals at the PSE side for connection status monitoring.
Solution Approach 2:
The patent dynamically switches between drawing current from the bulk capacitor during voltage decrease and drawing current from the PSE when voltage stabilizes. This dynamic current sourcing strategy ensures that the PSE detects the minimum required current while minimizing continuous power losses from the PSE.
2Loss of energy
If current is drawn from the bulk capacitor instead of the PSE, then power losses at the PSE are reduced, but the PSE cannot detect the minimum current draw
Solution Approach 1:
The PD generates periodic MPS current pulses that are detectable by the PSE. These periodic pulses serve dual purposes: they maintain the electrical connection detectability at the PSE side and allow the PD to meet minimum power consumption requirements while sourcing power from the bulk capacitor during non-pulse periods.
Solution Approach 2:
The patent changes the current draw pattern from continuous to periodic pulsed current. By modulating the current in periodic pulses with specific amplitude and duration parameters, the system ensures detectability at the PSE while allowing bulk capacitor supplementation during intervals, thereby reducing overall PSE power losses.
3Reliability
If a keep alive signal is generated in standby mode to maintain connection, then connection reliability is improved, but power consumption increases
Solution Approach 1:
The keep alive signal is implemented as periodic MPS pulses rather than continuous current draw. This periodic signaling maintains connection reliability by periodically confirming the PD's presence and operational status to the PSE, while significantly reducing average power consumption compared to continuous signaling.
Solution Approach 2:
The bulk capacitor is pre-charged during active operation to store sufficient energy. During standby mode, this pre-stored energy in the bulk capacitor supplies the MPS pulses, eliminating the need for continuous PSE power delivery while maintaining connection reliability through periodic signaling.
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 reduces power losses by ensuring that the minimum current required to maintain the electrical connection is detectable at the power supply side, preventing disconnection and optimizing energy efficiency in PoE systems, particularly in lighting applications with many devices.
Implementation Method 1
a PD comprises a capacitor which stores power and under certain conditions when a MPS signal is generated current is drawn from the PD capacitor instead of from the PSE
Implementation Method 2
measuring a voltage over the at least one capacitor while the device is drawing current
Data Source
AI summary
A method, computer program product and device for generating a power signal are provided. In a power distribution system (e.g. PoE), a device (2) (e.g. PD) comprising at least one capacitor (e.g. bulk capacitor) parallel to a load (26) of the device, is powered by a power supply (1) (e.g. PSE). The power supply (1) is arranged for powering the device (2) when at least a minimum current (e.g. MPS) is drawn by the device (2) from the power supply (1). The device (2) determines, by measuring the voltage over the at least one capacitor, whether the current is drawn (partially) from the at least one capacitor. In which case the device (2) is controlled to draw current such that at least a minimum current is drawn from the power supply (1) and the power supply (1) remains powering the device (2).