Bidirectional DC-DC Converter With Capacitive Gain and Current Sharing
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Solution Overview
Problem
Existing bidirectional converters face issues such as low power density, complex control, high electromagnetic interference, and voltage stress on switches, particularly in applications requiring high input and low output voltages, with non-isolated converters having narrow duty ratios and isolated converters facing stability and reliability challenges.
Innovation Solution
A bidirectional power converter with high voltage gain and automatic current sharing, utilizing capacitive voltage division and interleaved control, featuring multiple switching circuits and clamping capacitors to achieve uniform current sharing without additional components or complex control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If isolated converters (DAB or resonant) are used to achieve electrical isolation and bidirectional power flow, then reliability is improved, but device complexity increases due to transformer size, circulating current, and complicated control circuits
Solution Approach 1:
The converter is divided into multiple modular units (first converter unit, second converter unit, third converter unit) that can be independently configured. Each unit contains switching circuits, clamping capacitors, and inductors that work together to achieve the desired power conversion while maintaining electrical isolation through capacitive coupling rather than traditional transformers.
Solution Approach 2:
Clamping capacitors are introduced as intermediary elements to provide electrical isolation and voltage transformation without requiring traditional transformers. These capacitors serve as mediators between different voltage domains, enabling bidirectional power flow while maintaining galvanic isolation and reducing circulating currents.
2Device complexity
If non-isolated bidirectional buck-boost converters are used to achieve simplicity, then device complexity is reduced, but adaptability decreases due to narrow duty ratio range and limited voltage conversion capability
Solution Approach 1:
The converter employs dynamic duty ratio control for each switching circuit independently. The control circuit adjusts the duty ratios of the first, second, and third switching circuits based on real-time voltage conditions, enabling the converter to adapt to a wide range of input-output voltage ratios while maintaining stable operation and avoiding the narrow duty ratio limitations of traditional buck-boost converters.
Solution Approach 2:
The invention changes the operating parameters by introducing multiple independently controllable switching circuits with different duty ratios. By varying the duty ratios of individual switching circuits and their phase relationships, the converter can achieve continuous adjustment of the overall voltage conversion ratio, significantly expanding the adaptability range compared to single-stage buck-boost converters.
3Power
If traditional high voltage gain converters are used to achieve high voltage conversion ratio, then voltage gain is improved, but voltage stress on switches increases leading to higher losses and component costs
Solution Approach 1:
The voltage gain function is segmented across multiple switching circuits rather than concentrated in a single stage. Each switching circuit operates at a moderate voltage stress level, and the overall high voltage gain is achieved through the cascaded effect of multiple circuits working in sequence with appropriate duty ratio coordination, thereby reducing the voltage stress on individual switches.
Solution Approach 2:
Clamping capacitors serve as intermediary energy storage elements that facilitate voltage multiplication without requiring switches to block the full output voltage. The capacitors accumulate and transfer energy between switching cycles, enabling high voltage gain while keeping the voltage stress on switching devices within acceptable limits, thus reducing switching losses and component costs.
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 converter achieves high voltage gain with low voltage stress on switches, reducing losses and costs, and supports applications like energy storage systems, on-board chargers, and data centers with efficient current sharing and expanded conversion ratios.
Implementation Method 1
the bidirectional power converter is suitable for bidirectional high voltage gain applications due to the capacitive voltage division
Implementation Method 2
a first inductor. A first end of the first inductor is connected between the second high-side switch and the first low-side switch
Data Source
AI summary
A high-voltage gain DC-DC bidirectional power converter with automatic current sharing function includes first, second, and third switching circuits and a control circuit. The first switching circuit includes a first high-side switch, a second high-side switch and a first low-side switch that are connected to a first voltage source, a first clamping capacitor and a second low-side switch that are connected between the first high-side switch and a first voltage source, and a first inductor. The second switching circuit includes a second inductor and a third high-side switch that are connected between a second voltage source and the first switching circuit, and a third low-side switch. The third switching circuit includes a third inductor, a second clamping capacitor and a fourth high-side switch that are connected between the second voltage source and the first switching circuit, and a fourth low-side switch.