Power Converter Inductor Placement for Variable Speed Drive

Solution Overview

Problem

Existing variable speed drives for electric motors face challenges with inductors experiencing high current stress, leading to increased cost and size in power converters.

Innovation Solution

A power converter design that eliminates inductors between buck and boost stages by connecting them in a return-path configuration, reducing current stress and physical size, and utilizing a controller to manage operation modes and duty cycles for efficient motor drive.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If inductors are used between buck and boost stages in conventional converter topology, then the power converter can drive motors at variable speeds, but the inductors are subject to high current stress which increases cost and size

Engineering Contradiction:

Improvevariable speed drive capabilityVSAvoidinductor size

Core Design Contradiction:

Adaptability or versatilityVSWeight of stationary object

Solution Approach 1:

The patent inverts the conventional topology by moving the inductor from the high-current path between buck and boost stages to the output stage. This topological inversion places the inductor in a lower current stress position, reducing its size while maintaining the variable speed drive capability through the same converter stages.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent changes the dimensional arrangement of components by repositioning the inductor from a series position between converter stages to a parallel output position. This spatial reconfiguration alters the current distribution dimensions, allowing the inductor to operate at lower current levels while the converter stages handle the motor drive requirements.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Adaptability or versatility

If inductors are used between buck and boost stages in conventional converter topology, then the power converter can drive motors at variable speeds, but the inductors are subject to high current stress which increases cost

Engineering Contradiction:

Improvevariable speed drive capabilityVSAvoidconverter cost

Core Design Contradiction:

Adaptability or versatilityVSEase of manufacture

Solution Approach 1:

The patent inverts the conventional topology by moving the inductor from the high-current path between buck and boost stages to the output stage. This topological inversion places the inductor in a lower current stress position, reducing its size while maintaining the variable speed drive capability through the same converter stages.

Inventive Principle:

Principle #13The other way round (Inversion)

3Reliability

If inductors with high current capacity are used to withstand current stress, then reliability is improved, but device complexity and size increase

Engineering Contradiction:

Improveinductor current handling capabilityVSAvoidconverter structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent inverts the conventional topology by moving the inductor from the high-current path between buck and boost stages to the output stage. This topological inversion places the inductor in a lower current stress position, reducing its size while maintaining the variable speed drive capability through the same converter stages.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The converter stages act as intermediaries that condition the power before it reaches the inductor. By placing the buck and boost stages between the power source and the inductor, the system mediates the current characteristics, delivering controlled current to the inductor and reducing its stress requirements.

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentEP4224687A1Power converter

Publication Date: 2023.08.09 INFINEON TECH AUSTRIA AG

Figure 1
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AI summary

Disclosed is a power converter. The power converter includes first nodes (11, 12); a plurality of second nodes (13a, 13b, 13c); and a plurality of converter units (1a, 1b, 1c). Each of the plurality of converter units (1a, 1b, 1c) includes a first stage (2a, 2b, 2c) coupled to the first nodes (11, 12) and including a switch node (23a, 23b, 23c) of the first stage (2a, 2b, 2c), a second stage (3a, 3b, 3c) coupled to a respective one of the second nodes (13a, 13b, 13c) and including a switch node (33a, 33b, 33c) of the second stage (3a, 3b, 3c), and an inductor (4a, 4b, 4c). The switch node (23a, 23b, 23c) of the first stage (2a, 2b, 2c) is connected to the switch node (33a, 33b, 33c) of the second stage (3a, 3b, 3c), and the inductor (4a, 4b, 4c) is connected between an inductor node (32a, 32b, 32c) of the second stage (3a, 3b, 3c) and one of the first nodes (11, 12).