Soft Switching Power Conversion Device

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Solution Overview

Problem

Matrix converters using multiphase AC power sources face high switching losses and stress on bidirectional switches due to hard switching, limiting the frequency of output voltage in practical ranges and reducing conversion efficiency.

Innovation Solution

A power conversion device employing soft switching with a resonant circuit and snubber capacitors to reduce switching losses, using a switching control circuit that controls bidirectional switches in zero current or zero voltage sequences, and configuring bidirectional switches with reverse parallel switching elements and snubber capacitors to minimize power loss and stress.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If hard switching is used for bidirectional switches, then the power conversion device structure is simple, but switching loss increases and conversion efficiency decreases

Engineering Contradiction:

Improvepower conversion device structureVSAvoidswitching loss

Core Design Contradiction:

Device complexityVSLoss of energy

Solution Approach 1:

A resonant circuit is introduced as an intermediary component between the power conversion circuit and the load. This resonant circuit enables soft switching by creating resonant conditions that allow bidirectional switches to turn on/off when current or voltage is zero, thereby reducing switching loss without significantly complicating the overall device structure

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The switching mode of bidirectional switches is changed from hard switching to soft switching by utilizing resonant conditions. This parameter change in the switching method reduces the switching loss and improves conversion efficiency while maintaining reasonable device complexity

Inventive Principle:

Principle #35Parameter changes

2Device complexity

If hard switching is used for bidirectional switches, then the device structure is simple, but stress on power semiconductor devices increases and reliability decreases

Engineering Contradiction:

Improvedevice structureVSAvoidbidirectional switch reliability

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The resonant circuit serves as a mediator that creates soft switching conditions, reducing the stress on power semiconductor devices during switching transitions. This improves the reliability of bidirectional switches without requiring a fundamentally different device structure

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

Snubber circuits are added to bidirectional switches to provide beforehand cushioning against voltage and current spikes during switching. This protective measure reduces stress on power semiconductor devices and improves reliability while maintaining relatively simple device structure

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

3Productivity

If output voltage frequency is increased, then the power conversion performance is improved, but switching loss increases and conversion efficiency decreases

Engineering Contradiction:

Improveoutput voltage frequencyVSAvoidswitching loss

Core Design Contradiction:

ProductivityVSLoss of energy

Solution Approach 1:

Soft switching enables continuous and smooth transitions of bidirectional switches without the abrupt changes characteristic of hard switching. This continuity reduces switching loss even at higher output voltage frequencies, allowing improved power conversion performance without the penalty of increased energy loss

Inventive Principle:

Principle #20Continuity of useful action

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

Significantly reduces switching losses, improves conversion efficiency, and enhances the reliability of bidirectional switches, allowing for higher output voltage frequencies within practical ranges.

Implementation Method 1

The resonant circuit is connected to an output side of the power conversion circuit. By the soft switching, either current or voltage rises from zero slowly at a switching timing of the switch

Methodology Applied

Scientific EffectResonance: Resonance

Implementation Method 2

The switching control circuit switches the states of the plurality of bidirectional switches relating to the switching, by soft switching. By the soft switching, either current or voltage rises from zero slowly at a switching timing of the switch, which reduces power loss calculated by the time integration of the voltage and the current

Methodology Applied

Scientific EffectSoft switching:

Data Source

PatentEP3104510B1Power conversion device

Publication Date: 2021.05.19 OMRON CORP

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AI summary

A power conversion circuit (2) uses a multiphase AC power source as an input and has a plurality of bidirectional switches each of which is connected to each phase of the multiphase AC power source. A switching control circuit (4) controls the states of the plurality of bidirectional switches and switches a combination of two phases of the multiphase AC power source, relating to interphase voltage to be outputted from the power conversion circuit (2) to a load side. A resonant circuit (3) is connected to an output side of the power conversion circuit. The switching control circuit (4), at a time of switching of the combination of the two phases that output the interphase voltage to the load side, switches the states of the bidirectional switches relating to the switching, by soft switching.