Buck Converter Peak Current Rate Limiting for Wide-Input Stability

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Solution Overview

Problem

Buck converters with wide input voltage ranges (e.g., 90VDC to 600VDC) experience instability and susceptibility to load disturbances due to high forward control gain, which traditional methods fail to adequately address.

Innovation Solution

Implementing a control method that switches between normal and rate-limited switching modes based on predetermined voltage thresholds, with the rate-limited mode being enabled or disabled accordingly, and using a peak inductor current limiting function to manage current in the buck converter.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If the buck converter operates in normal switching mode with wide input voltage range, then the control gain is high, but the system becomes unstable and more susceptible to load disturbances

Engineering Contradiction:

Improvecontrol gainVSAvoidsystem stability

Core Design Contradiction:

PowerVSStability of the object's composition

Solution Approach 1:

The patent applies dynamics by implementing a mode-switching mechanism that transitions the buck converter between normal switching mode and rate-limited switching mode based on operating conditions. The controller dynamically adjusts the switching behavior by enabling rate limiting when specific conditions are detected, thereby adapting the system characteristics to maintain stability across varying input voltages and load conditions while preserving high control gain when applicable.

Inventive Principle:

Principle #15Dynamics

2Speed

If the buck converter operates in normal switching mode, then the response speed is fast, but the system is more susceptible to load transients

Engineering Contradiction:

Improveresponse speedVSAvoidload transient susceptibility

Core Design Contradiction:

SpeedVSObject-affected harmful factors

Solution Approach 1:

The patent applies preliminary anti-action by implementing rate limiting as a preventive measure against harmful load transients. The controller monitors operating conditions and proactively enables rate-limited switching mode before severe transients can occur, thereby preemptively counteracting their harmful effects. This approach allows the system to maintain fast response during normal operation while protecting against load transient susceptibility when conditions warrant.

Inventive Principle:

Principle #9Preliminary anti-action

Data Source

PatentEP4262070A1Peak current change rate limiting for buck converters

Publication Date: 2023.10.18 HAMILTON SUNDSTRAND CORP

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AI summary

A method of DC-DC power conversion includes converting a DC link voltage to a DC output voltage for a load that is lower than the DC link voltage using a buck converter. The method includes controlling the buck converter in a normal switching mode in response to the DC link voltage being below a predetermined high threshold. The method also includes controlling the buck converter in a rate limited switching mode in response to the DC link voltage being at or above the predetermined high threshold.