Phase Current Balancing in Multiphase Coupled Inductor Converters

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Solution Overview

Problem

Multi-phase buck converters face issues with current imbalance and excessive switching, leading to switch heating and reduced device lifetime, particularly during large voltage swings and in systems using coupled inductors.

Innovation Solution

A power conversion system that identifies the longest and second-longest inactive switching modules, swaps their firing orders to balance currents and avoid rapid switching, thereby reducing current imbalances and minimizing multiple switching events within a pulse-width modulated cycle.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If switches are commanded to cycle multiple times in a pulse-width modulated cycle to achieve large voltage swings, then the output voltage response is improved, but switch heating increases and device lifetime is reduced

Engineering Contradiction:

Improvevoltage response speedVSAvoidswitch temperature

Core Design Contradiction:

SpeedVSTemperature

Solution Approach 1:

The system dynamically adjusts the switching pattern by detecting when a switch has been commanded to cycle multiple times within a single pulse-width modulated cycle and selectively prohibiting additional switching events for that switch, thereby adapting the switching behavior to real-time conditions and preventing excessive heating while maintaining voltage response capability

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The controller proactively identifies switches that have already cycled once in the current pulse-width modulated cycle and preemptively prohibits them from cycling again, preventing the harmful effect of multiple switching events before they occur, thus avoiding switch heating and extended device lifetime

Inventive Principle:

Principle #10Preliminary action

2Temperature

If logic is inserted into the controller to prohibit multiple switching events for a given switch within the same pulse-width modulated cycle, then switch heating is reduced, but controller performance is significantly reduced

Engineering Contradiction:

Improveswitch temperatureVSAvoidcontroller performance

Core Design Contradiction:

TemperatureVSProductivity

Solution Approach 1:

The prohibition logic is applied locally and selectively only to specific switches that have already cycled once within the pulse-width modulated cycle, rather than globally prohibiting all switching events, thus maintaining controller performance while preventing switch heating in the affected switches

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The system applies a partial prohibition - allowing switches to cycle once but prohibiting a second cycle - which is sufficient to prevent switch heating without completely restricting switching operations, thereby maintaining adequate controller performance for normal voltage regulation

Inventive Principle:

Principle #16Partial or excessive action

3Temperature

If switch duty cycle is adjusted to prevent multiple switching events, then switch heating is reduced, but ripple on the output increases

Engineering Contradiction:

Improveswitch temperatureVSAvoidoutput ripple

Core Design Contradiction:

TemperatureVSObject-generated harmful factors

Solution Approach 1:

The system uses feedback from the output voltage and current measurements to dynamically adjust the switching assignments and duty cycles of individual switches, ensuring that multiple switching events are prevented while maintaining output voltage regulation and minimizing output ripple through real-time control adjustments

Inventive Principle:

Principle #23Feedback

4Reliability

If DC currents in coupled inductors are corrected with a control loop that adjusts pulse-widths, then current imbalance is reduced, but disturbances on the output are caused

Engineering Contradiction:

Improvecurrent balanceVSAvoidoutput disturbance

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The system uses an intermediary approach by introducing a current balance detection mechanism that monitors DC currents in coupled inductors and selectively adjusts switching assignments to balance currents, while the output disturbances are minimized through careful coordination of switching events and use of the coupled inductor structure itself as a current-balancing element

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS11563379B2Phase current balancing for multiphase coupled inductor converter

Publication Date: 2023.01.24 ADVANCED ENERGY IND INC

AI summary

This disclosure describes systems, methods, and apparatus for reducing current imbalances between phases in a multi-phase converter as well as reducing instances of particular phases switching twice within a single pulse-width modulated cycle, or other time period. Phases that have not switched for a longest period of time can be compared to see if swapping their firing patterns would reduce current imbalances, and if so, then those firing patterns can be swapped.