Multi-Level Converter Control Without Current Polarity Detection

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Conventional multi-level circuits face issues with unstable flying capacitor voltage due to misjudgment of current polarity, especially under light load and high-frequency switching, leading to potential circuit damage and reliability concerns.

Innovation Solution

A control method for multi-level conversion circuits that adjusts duty ratios and phase-shift angles without determining current polarity, using a control unit to balance flying capacitor voltage in continuous and discontinuous conduction modes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If current polarity detection is used to control flying capacitor voltage, then the control method is simple, but the reliability deteriorates due to misjudgment under light load and high-frequency switching

Engineering Contradiction:

Improvecontrol method simplicityVSAvoidflying capacitor voltage balance control reliability

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The patent replaces the mechanical/electronic detection of current polarity with a mathematical model-based control approach. By using duty ratio adjustment and phase-shift angle control, the system calculates and controls flying capacitor voltage balance without physically detecting current direction, thereby eliminating misjudgment issues while maintaining control simplicity.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the control parameters from current polarity detection to duty ratio and phase-shift angle. By adjusting these parameters, the system achieves flying capacitor voltage balance control without relying on current direction detection, thus improving reliability while keeping the control method straightforward.

Inventive Principle:

Principle #35Parameter changes

2Ease of operation

If current polarity detection is used to balance flying capacitor voltage, then the control logic is straightforward, but measurement precision deteriorates due to sampling error and current ripple

Engineering Contradiction:

Improvecontrol logic simplicityVSAvoidcurrent polarity detection precision

Core Design Contradiction:

Ease of operationVSMeasurement precision

Solution Approach 1:

The patent substitutes the imprecise current polarity detection system with a duty ratio and phase-shift angle control system. This replacement eliminates sampling errors and current ripple interference, achieving precise flying capacitor voltage balance control without compromising control logic simplicity.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces duty ratio and phase-shift angle as intermediary control parameters between the control unit and the flying capacitors. These intermediaries enable precise voltage balance control without directly detecting current polarity, thereby avoiding measurement precision issues while maintaining straightforward control logic.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Reliability

If duty ratio and phase-shift angle control is implemented, then flying capacitor voltage balance reliability is improved, but device complexity increases

Engineering Contradiction:

Improveflying capacitor voltage balance control reliabilityVSAvoidcontrol circuit complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent makes the control unit multi-functional by enabling it to simultaneously adjust duty ratios and phase-shift angles for multiple flying capacitors. This universal control approach improves voltage balance reliability across all capacitors while avoiding the need for separate control circuits, thus limiting the increase in device complexity.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The patent merges the control of multiple flying capacitors into a unified control scheme using duty ratio and phase-shift angle adjustments. By combining control functions into a single integrated approach, the system achieves improved reliability without proportionally increasing device complexity.

Inventive Principle:

Principle #5Merging (Combining)

Data Source

PatentUS12512768B2Multi-level conversion circuit and control method for flying capacitor voltage thereof

Publication Date: 2025.12.30 DELTA ELECTRONICS (SHANGHAI) CO LTD

AI summary

A multi-level conversion circuit and a control method for flying capacitor voltage thereof are provided. In the multi-level conversion circuit, each flying capacitor is connected between a common connection node of the lower switches connected therewith and a common connection node of the upper switches connected therewith. The control method includes steps of: (a) determining the main switch and synchronous rectification switch of the lower and upper switches; (b) acquiring an adjustment value corresponding to each flying capacitor; (c) adjusting a duty ratio of the main switch according to the adjustment value corresponding to the flying capacitor connected therewith; and (d) when the multi-level conversion circuit working in a CCM, increasing a phase-shift angle between the main switches by an angle to make a peak value or a valley value of an inductor current remain unchanged before and after adjusting the duty ratio.