Multi-Stage Multilevel DC-DC Converter Voltage Stress Reduction

Solution Overview

Problem

Current 48V DC bus architectures in data centers face challenges with high voltage stress on switches and increased inductance values, leading to reduced power density and efficiency in server motherboards due to direct conversion from 48V to lower voltage levels using single-stage Buck converters.

Innovation Solution

The implementation of multi-stage multilevel DC-DC step-down converters with specific switch configurations and duty cycles reduces voltage stress on switches and inductors, allowing for smaller inductor sizes and improved efficiency by dividing the voltage reduction process across multiple stages.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If a single-stage Buck converter is used to convert 48V directly to lower voltage levels, then the conversion is simple and direct, but the voltage stress on switches increases and the inductance value increases

Engineering Contradiction:

Improveconverter structureVSAvoidvoltage stress on switches

Core Design Contradiction:

Device complexityVSStress or pressure

Solution Approach 1:

The patent divides the single-stage conversion into multiple stages (first stage Buck converter and second stage multilevel Buck converter). The first stage converts 48V to an intermediate voltage, while the second stage performs the final conversion to the target voltage. This segmentation reduces the voltage stress on individual switches in each stage compared to a single-stage converter handling the full 48V to low voltage conversion.

Inventive Principle:

Principle #1Segmentation

2Device complexity

If a single-stage Buck converter is used to convert 48V directly to lower voltage levels, then the conversion is simple and direct, but the inductance value increases

Engineering Contradiction:

Improveconverter structureVSAvoidinductance value

Core Design Contradiction:

Device complexityVSQuantity of substance

Solution Approach 1:

The patent divides the single-stage conversion into multiple stages (first stage Buck converter and second stage multilevel Buck converter). The first stage converts 48V to an intermediate voltage, while the second stage performs the final conversion to the target voltage. This segmentation reduces the voltage stress on individual switches in each stage compared to a single-stage converter handling the full 48V to low voltage conversion.

Inventive Principle:

Principle #1Segmentation

3Stress or pressure

If multi-stage multilevel DC-DC step-down converters are used, then voltage stress on switches is reduced and inductor size is reduced, but the converter structure becomes more complex

Engineering Contradiction:

Improvevoltage stress on switchesVSAvoidconverter structure

Core Design Contradiction:

Stress or pressureVSDevice complexity

Solution Approach 1:

The patent combines multiple Buck converter stages into a unified multi-stage multilevel architecture. The first stage Buck converter and second stage multilevel Buck converter are integrated to work together, sharing common components and control mechanisms where possible. This merging approach achieves voltage stress reduction while managing the overall system complexity through coordinated design.

Inventive Principle:

Principle #5Merging (Combining)

4Quantity of substance

If multi-stage multilevel DC-DC step-down converters are used, then inductor size is reduced and power density increases, but the converter structure becomes more complex

Engineering Contradiction:

Improveinductor sizeVSAvoidconverter structure

Core Design Contradiction:

Quantity of substanceVSDevice complexity

Solution Approach 1:

The patent divides the single-stage conversion into multiple stages (first stage Buck converter and second stage multilevel Buck converter). The first stage converts 48V to an intermediate voltage, while the second stage performs the final conversion to the target voltage. This segmentation reduces the voltage stress on individual switches in each stage compared to a single-stage converter handling the full 48V to low voltage conversion.

Inventive Principle:

Principle #1Segmentation

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 approach significantly reduces voltage stress on switches and inductors, increases power density, and enhances efficiency by allowing for smaller converter sizes and lower switching losses, making it suitable for high-power applications in data centers and server environments.

Implementation Method 1

a first inductor having a first terminal connected between the second and third switches and a second terminal connected to a first output terminal

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Implementation Method 2

a first capacitor connected in parallel with the second and third switches

Methodology Applied

Scientific EffectCapacitance: Capacitance

Data Source

PatentUS10468965B2Multi-stage multilevel DC-DC step-down converter

Publication Date: 2019.11.05 QUEENS UNIV

AI summary

Disclosed are multi-stage multilevel DC-DC step-down converters. Stages may include three or four switches, and switches of each stage are operated at selected duty cycles such that each stage reduces an input voltage by one-half and voltage stress on switches is reduced. In some embodiments only a single output inductor is used in an LC filter, and the inductor may be very small as compared with a conventional Buck converter. Thus, embodiments provide DC-DC step-down converters with high power density and efficiency.