Active Inrush Current Limiter for LED Networks
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Solution Overview
Problem
Existing inrush current limiting solutions for networks of power supplies are inadequate as they often rely on fixed time-based methods, are sensitive to voltage and frequency fluctuations, and consume power even when heated, failing to effectively manage inrush currents in LED lighting systems with multiple power supplies.
Innovation Solution
An active inrush current limiter that monitors line voltage and voltage drop across a current limiting resistance, using a microcontroller to detect patterns in power flow and bypass the resistance only when capacitors have completed charging, thereby eliminating the impact of voltage fluctuations and maximizing efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If a current limiting resistance is used to limit inrush current, then inrush current is suppressed, but power is consumed continuously even when heated
Solution Approach 1:
The patent uses an NTC (negative temperature coefficient) thermistor whose resistance dynamically changes with temperature. When cold, the thermistor presents high resistance to limit inrush current. As current flows and the thermistor heats up, its resistance automatically decreases, reducing power consumption while maintaining current limiting functionality.
Solution Approach 2:
The patent exploits the temperature-dependent resistance parameter of the NTC thermistor. By allowing the resistance parameter to change naturally with temperature during operation, the system achieves both inrush current limiting and reduced steady-state power consumption without active control.
2Productivity
If multiple power supplies are connected to the same AC source, then more power supplies are available, but the combined capacitance increases resulting in large inrush current
Solution Approach 1:
The patent places a single NTC thermistor in the common AC line before the power is distributed to multiple power supplies. This unified approach limits the inrush current for the entire group of power supplies simultaneously, avoiding the need for individual current limiting components for each power supply.
3Device complexity
If a fixed time-based method is used to bypass current limiting resistance, then the system is simple to control, but it is sensitive to voltage and frequency fluctuations
Solution Approach 1:
The NTC thermistor is a passive component that automatically adjusts its resistance based on its own temperature, which is determined by the actual current flow and power dissipation. This self-regulating behavior eliminates the need for external control circuits that would be sensitive to voltage and frequency variations.
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
Effectively limits inrush current to prevent stress on electrical components and reduce energy consumption by accurately determining when to bypass the current limiting resistance, ensuring safe and efficient power delivery to multiple power supplies.
Implementation Method 1
Existing current limiting modules may employ a negative temperature coefficient (NTC) resistor, whose resistance is initially high when the system is first turned on and the resistor is cool but decreases as the inrush current heats the NTC resistor
Implementation Method 2
The current limiting module includes a relay in parallel with the electronic switch and current limiting resistance, where closure of the relay contacts bypasses the current limiting resistance and connects AC power to the group of power supplies
Data Source
AI summary
An active inrush current limiter and method of limiting inrush current actively monitor line voltage and voltage drop across a current limiting resistance in a manner that eliminates the impact of fluctuations of line voltage on the decision of when to close a relay and bypass a current limiting resistance between the AC source and a group of power supplies. The active inrush current limiter includes a microcontroller connected to control the electronic switch and relay. The microcontroller is configured to sample the source AC power and detect a pattern of current flow through the electronic switch and current limiting resistance. A program executed in the microcontroller includes calculations that determine when to close the relay and bypass the current limiting resistance by detecting changes in power flow through the current limiting resistance that reliably correspond to a time when the capacitors in the power supplies have completed charging.