Coupled-Inductor Buck Converter for Isolated High-Power Step-Down
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Solution Overview
Problem
Existing step-down converters face inefficiencies in achieving high efficiency while maintaining an inexpensive circuit design, particularly in converting input DC voltage to a lower output DC voltage with galvanic isolation and power limitations.
Innovation Solution
A voltage converter design featuring two buck converter circuit arrangements with coupled inductors and freewheeling diodes, transformer-coupled for voltage balancing and overvoltage protection, operating in a free-running mode to optimize switching times and magnetic flux elimination, ensuring efficient conversion with a common magnetic core and feedback voltage divider.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a flyback converter with transformer and capacitor bank is used, then galvanic isolation between input and output is achieved, but power is limited to approximately 250 W
Solution Approach 1:
The converter is divided into two separate buck converter circuit arrangements (first and second) with各自的 switching elements, inductors, and capacitors. Each arrangement processes a portion of the input voltage, allowing the system to handle higher total power while maintaining galvanic isolation through the coupled inductor configuration.
Solution Approach 2:
The patent employs a coupled inductor structure where the magnetic core of one inductor is nested within or integrated with the other, creating a compact transformer-like arrangement that provides galvanic isolation while enabling higher power transmission through coordinated magnetic coupling.
2Loss of energy
If two buck converter circuit arrangements with coupled inductors are used, then efficiency is improved, but device complexity increases
Solution Approach 1:
The patent merges two buck converter arrangements into a single integrated system with coupled inductors sharing a common magnetic core. The input capacitors are connected in series to share the input voltage, and the output capacitors are connected in parallel to provide combined output, reducing overall component count and complexity while improving efficiency through magnetic coupling.
Solution Approach 2:
The coupled inductor structure serves multiple functions simultaneously: it provides energy storage for both converter arrangements, enables magnetic coupling for efficient energy transfer, provides galvanic isolation, and allows voltage sharing through the series-connected input capacitors. This multi-functionality reduces the need for separate components.
3Manufacturing precision
If input capacitors are arranged in series to share input voltage, then voltage balancing is achieved, but overvoltage protection is required
Solution Approach 1:
The patent incorporates a feedback mechanism where the control device monitors the voltage across each input capacitor and adjusts the switching duty cycles of the respective switching elements to maintain balanced voltage distribution. This active feedback control ensures precise voltage sharing while preventing overvoltage conditions.
Solution Approach 2:
The coupled inductor configuration provides inherent overvoltage protection by allowing magnetic energy to be transferred between the two inductors when voltage imbalances occur. The magnetic coupling acts as a cushioning mechanism that prevents voltage spikes from damaging the capacitors before they can cause harm.
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 design achieves high efficiency and balanced output voltages across the converter circuit arrangements, effectively stepping down input DC voltage while minimizing power losses and maintaining galvanic isolation, suitable for applications like robot control systems.
Implementation Method 1
the first coupled inductor and the second coupled inductor are transformer-coupled to each other
Implementation Method 2
when the magnetic flux of the first coupled inductor and the second coupled inductor is completely dissipated
Data Source
Figure 1
Figure 2
AI summary
The invention relates to a voltage converter (1), which is designed as a step-down converter, for reducing an input direct voltage (Ue) to an output direct voltage (Ua) lower than the input direct voltage (Ue), comprising: a first step-down converter circuit arrangement (2), comprising a first semiconductor switching element (Qh) having a first control input (Ugh), a first coupled choke (Lsh) having a first freewheeling diode (Dh), and a first input capacitor (Cph) and a first output capacitor (Csh); a second step-down converter circuit arrangement (3), comprising a second semiconductor switching element (Ql) having a second control input (Ugl), a second coupled choke (Lsl) having a second freewheeling diode (Dl), and a second input capacitor (Cpl) and a second output capacitor (Csl). The invention further relates to an associated control device (12) for controlling a voltage converter (1) of this type.