Multi-Stage DC-DC Converter With Inductor-Coupled Soft Charging
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Solution Overview
Problem
Conventional DC-DC power converters face challenges in achieving high voltage conversion ratios (VCRs) with high efficiency, particularly in applications requiring large step-down conversions, such as data centers, electric vehicles, and mobile electronics, due to inefficiencies in semiconductor switches, inductor size, and energy losses in switched-capacitor topologies.
Innovation Solution
A multi-stage DC-DC power converter design that incorporates an inductor coupling current source between switched-capacitor stages, minimizing hard charge losses and reducing inductor current, allowing for high VCRs with improved efficiency by soft charging and discharging flying capacitors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple DC-DC converter stages are used to achieve large voltage step-down ratio, then the voltage conversion ratio is improved, but the overall power efficiency deteriorates due to energy conversion loss at each stage
Solution Approach 1:
The power conversion process is divided into two distinct stages: a switched-capacitor stage for initial voltage reduction and an inductor-based stage for final precision conversion. This segmentation allows each stage to operate optimally within its voltage range, reducing cumulative losses compared to using multiple identical converter stages.
Solution Approach 2:
A coupled inductor is introduced as an intermediary energy storage element between the switched-capacitor stage and the inductor-based converter stage. This coupled inductor serves as a mediator that transfers energy efficiently between stages while enabling soft-charging operations that reduce power losses.
2Adaptability or versatility
If conventional switched-capacitor topologies are used for high voltage conversion ratio, then the voltage conversion ratio is improved, but hard charge losses increase reducing efficiency
Solution Approach 1:
The coupled inductor performs preliminary energy storage and soft-charging of the switched-capacitor stage before the final conversion stage. This preliminary action prepares the energy in a controlled manner, avoiding the hard charging losses that would occur if the full voltage conversion were attempted in a single switched-capacitor stage.
3Power
If the inductor is placed at the output of the converter to handle full load current, then the power delivery capability is improved, but the inductor size and weight increase
Solution Approach 1:
The inductor function is segmented into a coupled inductor at the intermediate stage and a smaller output inductor. The coupled inductor handles the bulk of the energy transfer at higher voltages where current is lower, while the final output inductor only needs to handle the precision conversion at 1V output, significantly reducing its size and weight requirements.
Solution Approach 2:
Different inductors are positioned at different stages with different functional requirements. The coupled inductor is designed for high-voltage energy storage and transfer, while the output inductor is optimized for low-voltage precision current control. This local optimization of inductor properties at different system points reduces overall weight while maintaining power delivery capability.
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 VCRs with reduced inductor current and power losses, minimizing board space, component count, and weight, while extending the VCR range and improving efficiency over conventional methods.
Implementation Method 1
A multi-stage DC-DC power converter includes a first switched-capacitor stage driven by an input voltage. A second switched-capacitor stage is coupled to the first switched-capacitor by an inductor coupling current source.
Data Source
AI summary
A multi-stage DC-DC power converter includes a first switched-capacitor stage driven by an input voltage. A second switched-capacitor stage is coupled to the first switched-capacitor by an inductor coupling current source. A controller controls charging and discharging of a flying capacitor by the inductor coupling current source in each of the first and second switched-capacitor stages. The controller operates such that each of the flying capacitors of the first and second switched-capacitor stages is soft charged by the inductor coupling current source and a frequency of a switched voltage across the inductor coupling current source is maintained to be high enough to limit inductor current ripple to be negligible compared to its DC component and ensure average inductor current is effectively reduced by factor equal to a voltage conversion ratio of the second switched-capacitor stage.