Shared-Inductor Pre-Charge Circuit for Avionics LRU EMC
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Solution Overview
Problem
Avionics LRUs for higher voltage applications face challenges in meeting electromagnetic compatibility (EMC) requirements while minimizing size, weight, and cost, often requiring larger and heavier inductors and capacitors to mitigate voltage spikes and inrush currents.
Innovation Solution
An electrical circuit design for LRUs that shares an inductor between an EMI filtering stage and an inrush current limiting active pre-charge circuit, incorporating a switching element, diodes, capacitive and inductive elements, and control circuitry to manage current flow, thereby reducing the number of components and weight.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If larger and heavier inductors and capacitors are used to mitigate voltage spikes and inrush currents in higher voltage applications, then electromagnetic compatibility (EMC) requirements are met, but the size, weight, and cost of the LRU increase
Solution Approach 1:
The patent combines the EMI filter inductor and the pre-charge circuit inductor into a single shared inductor. This merging of functions allows the system to meet EMC requirements while reducing the overall weight and component count, as the single inductor serves dual purposes rather than requiring separate components for each function.
Solution Approach 2:
The shared inductor is designed to perform multiple functions simultaneously: it acts as both the EMI filter inductor for electromagnetic compatibility and the pre-charge circuit inductor for inrush current limiting. This multi-functionality eliminates the need for separate dedicated components, thereby reducing weight while maintaining EMC compliance.
2Reliability
If larger and heavier inductors and capacitors are used to mitigate voltage spikes and inrush currents, then voltage spikes and inrush currents are suppressed, but the size and form factor of the LRU increase
Solution Approach 1:
The patent merges the EMI filtering function and the pre-charge circuit function into a single integrated circuit configuration that shares one inductor. This consolidation reduces the overall footprint and form factor of the LRU compared to using separate inductors and capacitors for each function, while still effectively suppressing voltage spikes and inrush currents.
3Reliability
If traditional separate EMI filter and pre-charge circuit designs are used, then each function is independently optimized, but the overall device complexity and component count increase
Solution Approach 1:
The patent integrates the EMI filter and pre-charge circuit into a single unified circuit design that shares one inductor, thereby reducing component count and circuit complexity while maintaining both functions. The switching element and control circuitry coordinate to enable the shared inductor to perform both filtering and pre-charge operations.
Solution Approach 2:
The circuit employs a switching element that dynamically changes the configuration of the shared inductor based on operational requirements. During different phases of operation, the switching element redirects current flow to enable the inductor to function as needed for either EMI filtering or pre-charge current limiting, adding dynamic control to manage the multi-functional operation.
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
The solution effectively limits inrush currents and voltage spikes while maintaining EMC compliance, reducing the overall size and weight of the LRU by sharing a single inductor across multiple functions.
Implementation Method 1
an inductive element coupled between the third node and the fourth node
Implementation Method 2
at least one capacitive element coupled between a fourth node and the second bus reference voltage node
Implementation Method 3
a first diode coupled between the third node and the second bus reference voltage node to enable current from the second bus reference voltage node to the third node
Data Source
Figure 1
Figure 2
AI summary
Electrical circuits and systems are provided for line replaceable units (LRUs) having an inductor shared between an electromagnetic interference (EMI) filtering stage and an inrush current limiting active pre-charge circuit. An exemplary circuit includes a first bus reference voltage node, a second bus reference voltage node, a switching element coupled between the first bus reference voltage node and a third node, a first diode coupled between the third node and the second bus reference voltage node to enable current from the second bus reference voltage node to the third node, at least one capacitive element coupled between a fourth node and the second bus reference voltage node, an inductive element coupled between the third node and the fourth node, and a second diode coupled between the fourth node and the first bus reference voltage node to enable current from the fourth node to the first bus reference voltage node.