AC-DC Converter Inrush Current Limiting via Inductive Reactance
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Solution Overview
Problem
Existing AC-DC converters face challenges in limiting inrush current peaks during startup phases and require complex assemblies with resistive elements that increase losses, making them inefficient.
Innovation Solution
An AC-DC converter design incorporating a triac switch to control the conduction phase angle of a rectifying bridge, coupled with inductive elements forming a common mode filter, and a rectifying element to supply low voltage for control circuits, eliminating the need for resistive elements and enabling voltage doubling functionality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If resistive elements are used to limit inrush current, then inrush current peaks are reduced, but energy losses increase and efficiency decreases
Solution Approach 1:
The patent changes the physical parameter of the limiting element from resistive to inductive. The inductive element limits inrush current through its impedance characteristic (XL = 2πfL) rather than resistance, allowing current limiting without the continuous power dissipation associated with resistive elements. This parameter change resolves the contradiction by maintaining current limiting functionality while eliminating energy losses.
Solution Approach 2:
The patent substitutes the electrical resistance mechanism with an inductive reactance mechanism. Instead of using ohmic resistance to limit current, the invention employs inductive reactance, which limits current during transient conditions (startup) but does not dissipate continuous power during normal operation, thus resolving the energy loss issue.
2Reliability
If complex assemblies with resistive elements are used for inrush current limiting, then current peaks are controlled, but device complexity and design sophistication increase
Solution Approach 1:
The patent extracts and eliminates the resistive elements from the inrush current limiting assembly. By removing these components entirely and replacing them with a simple inductive element, the invention simplifies the overall assembly while maintaining current peak control functionality through the inductive reactance of the remaining components.
Solution Approach 2:
The patent makes the inductive element serve multiple functions: it acts as both the inrush current limiting element and part of the common mode filter. This multi-functionality reduces the number of separate components needed, thereby simplifying the overall device complexity while maintaining effective current control.
3Reliability
If resistive elements are used for inrush current limiting, then current control is achieved, but the converter cannot operate in voltage doubler mode
Solution Approach 1:
The patent introduces a switching element that dynamically reconfigures the circuit topology between follower mode and voltage doubler mode. The switch can connect or disconnect the inductive element and rectifying bridge in different configurations, allowing the system to adapt its operating mode based on requirements while maintaining inrush current control capability in both modes.
Solution Approach 2:
The patent segments the circuit into distinct functional blocks (inductive element, rectifying bridge, switching element) that can be independently controlled and reconfigured. This segmentation allows flexible topological changes enabling operation in multiple modes (follower and voltage doubler) while maintaining effective inrush current limiting through the inductive element.
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 solution effectively limits inrush current peaks without resistive elements, reducing losses and simplifying the converter design, while allowing operation in both follower and voltage doubler modes.
Implementation Method 1
at least one first inductive element, in series with a first switch, between one of the first and second terminals and one of the input terminals of the bridge
Implementation Method 2
a rectifying bridge whose input terminals are respectively coupled to the first and second terminals and whose output terminals are respectively connected to the third and fourth terminals
Data Source
Figure 1~2
Figure 3
AI summary
The invention relates to an AC-DC converter comprising: a first terminal (12) and a second terminal (14), intended to receive an alternating voltage (Vac); a third terminal (16) and a fourth terminal (18), intended to provide a first DC voltage (Vout); at least one first capacitive element (C1, C2) connecting the third and fourth terminals; a rectifier bridge (3) whose input terminals (32, 34) are respectively coupled to the first and second terminals and whose output terminals are respectively connected to the third and fourth terminals; and at least one first inductive element (L1), in series with a first switch (52), between one of the first and second terminals and one of the input terminals of the bridge.