Flying Capacitor Buck Converter With Zero-Voltage Switching
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Solution Overview
Problem
Existing DC to DC voltage converters face challenges in accommodating large voltage variations, requiring complex control and EMI filtering, leading to high component stress, losses, and cooling requirements, which can limit their efficiency and lifespan.
Innovation Solution
The n-level flying capacitor multi-level buck converter employs a configuration with multiple pairs of switching elements and flying capacitors, operating in sequences to selectively apply input voltage across an output filter, utilizing zero-voltage switching (ZVS) and phase-shifted pulses to reduce switching losses and adjust active levels based on input and output voltages, thereby optimizing voltage stress and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional DC to DC voltage converters are used to accommodate large voltage variations, then voltage conversion capability is improved, but control complexity and EMI filtering requirements increase
Solution Approach 1:
The converter is divided into multiple independent switching cells, each handling a specific voltage level. This segmentation allows each cell to operate independently with simpler control logic, while collectively providing comprehensive voltage conversion capability across a wide range.
Solution Approach 2:
The converter dynamically adjusts the number of active switching cells based on the input voltage level. When input voltage is high, fewer cells are active; when input voltage drops, more cells are activated. This dynamic adaptation maintains optimal control complexity while accommodating large voltage variations.
2Adaptability or versatility
If conventional DC to DC voltage converters are used to accommodate large voltage variations, then voltage conversion capability is improved, but EMI filtering requirements increase
Solution Approach 1:
The EMI filtering burden is segmented across multiple switching cells operating at different voltage levels. Each cell generates less EMI individually, and their combined effect is reduced compared to a single converter handling the full voltage range, reducing overall EMI filtering requirements.
3Weight of stationary object
If voltage stresses across components are reduced, then component size can be reduced, but converter complexity increases
Solution Approach 1:
The voltage stress is segmented across multiple switching cells and flying capacitors. Each component within a cell experiences only a fraction of the total input voltage, allowing smaller component sizes. The segmentation distributes the electrical stress without requiring a completely complex redesign.
Solution Approach 2:
The voltage handling capability is extended by adding the dimensional aspect of multiple voltage levels through flying capacitors. Instead of using a single component rated for high voltage, the system uses multiple components at lower voltage levels arranged in series, achieving the same voltage handling with reduced individual component stress.
4Loss of energy
If losses are reduced in DC to DC voltage converters, then cooling requirements are reduced, but converter complexity increases
Solution Approach 1:
The converter dynamically optimizes the number of active switching cells based on operating conditions to minimize losses. By adapting the active cell count to match the input voltage level, the converter maintains high efficiency across different operating points while avoiding the constant complexity of managing all cells simultaneously.
Solution Approach 2:
The converter changes operational parameters such as switching frequency and cell configuration based on input voltage levels to optimize efficiency. At different voltage levels, different cells are activated with optimized switching parameters, reducing overall losses without requiring a fundamentally complex design.
5Weight of stationary object
If the weight of DC to DC voltage converter is reduced, then portability is improved, but component size reduction may increase voltage stress
Solution Approach 1:
The voltage handling is achieved by transitioning from a single high-voltage component to multiple low-voltage components arranged in series across different voltage levels. This dimensional approach to voltage handling reduces individual component stress while maintaining overall voltage conversion capability, enabling lighter weight without increasing voltage stress on any single component.
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 configuration reduces switching losses, prolongs component lifespan, minimizes cooling requirements, and stabilizes the converter's operation across varying input and output voltages, enhancing efficiency and reliability while reducing the weight and complexity of the converter.
Implementation Method 1
operate the first and second pairs of switching elements such that each switching element is switched on when a voltage across the switching element is zero
Data Source
AI summary
An n-level flying capacitor multi-level buck converter, for converting a DC input voltage into a DC output voltage provided at a load. The n-level flying capacitor multi-level buck converter is configured to: operate a first and second pairs of switching elements in a sequence to selectively apply a portion of the input voltage across the output filter; and operate the first and second pairs of switching elements such that each switching element turns on when a voltage across the switching element is zero.