Backflow Prevention Circuit With Commutation for Recovery Current Loss

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Solution Overview

Problem

Existing power converting devices face challenges in reducing recovery electric current during backflow, leading to increased losses and noise, especially when handling high-power applications, due to the limitations of wide band-gap semiconductors with high voltage resistance but low current-carrying capacity.

Innovation Solution

Incorporating a backflow preventing element connected between the power supply and load, along with commutating means that perform a commutation operation to redirect electric current to a different path, reducing recovery electric current and associated losses, and using a commutation rectifying element with low current-carrying capacity to minimize conduction losses.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If wide band-gap semiconductors with high voltage resistance are used as rectifiers, then voltage resistant characteristics are improved, but current-carrying capacity remains low leading to increased recovery electric current losses

Engineering Contradiction:

Improvevoltage resistant characteristicsVSAvoidrecovery electric current losses

Core Design Contradiction:

StrengthVSLoss of energy

Solution Approach 1:

The invention divides the rectifier function into two separate components: a voltage-resistant rectifying element (using wide band-gap semiconductors) and a commutating element. The voltage-resistant element handles only the rectification function with minimal recovery current, while the commutating element handles the commutation function. This segmentation allows each component to be optimized for its specific function, reducing overall energy losses.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention introduces a commutating element as an intermediary component between the power supply and the load. This commutating element assumes the role of handling recovery electric current during commutation, thereby protecting the voltage-resistant rectifying element from excessive recovery current losses and enabling the system to achieve both high voltage resistance and low energy loss.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Quantity of substance

If elements with large electric-current capacity are used, then current-carrying capacity is improved, but costs increase and crystal defects occur

Engineering Contradiction:

Improveelectric-current capacityVSAvoidmanufacturing cost and crystal quality

Core Design Contradiction:

Quantity of substanceVSEase of manufacture

Solution Approach 1:

The invention segments the functional requirements by assigning the voltage-resistant rectification function to wide band-gap semiconductor elements (which have limited current capacity) and the commutation function to separate commutating elements. This allows the use of smaller, cheaper, and higher-quality semiconductor elements for the rectification function, while the commutating elements can be sized appropriately for their specific role, overall achieving large effective current capacity without the drawbacks of using oversized elements throughout the system.

Inventive Principle:

Principle #1Segmentation

3Loss of energy

If recovery electric current is reduced, then conduction loss and noise are reduced, but device complexity increases due to additional commutating means

Engineering Contradiction:

Improveconduction lossVSAvoidcircuit structure

Core Design Contradiction:

Loss of energyVSDevice complexity

Solution Approach 1:

The invention merges the commutation function with the existing rectifier circuit by integrating commutating elements into the rectifier structure. The commutating elements are connected in parallel with the voltage-resistant rectifying elements, allowing the combination to perform both rectification and commutation functions. This merging approach reduces overall device complexity compared to implementing separate commutation circuits.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The commutating elements serve multiple functions: they provide commutation action to reduce recovery electric current, they can assist in voltage clamping, and they contribute to the overall current-carrying capacity of the system. This multi-functionality reduces the need for additional dedicated components, thereby limiting the increase in device complexity while achieving significant reductions in conduction loss and noise.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS9225258B2Backflow preventing means, power converting device, and refrigerating and air-conditioning apparatus

Publication Date: 2015.12.29 MITSUBISHI ELECTRIC CORP

AI summary

For example, backflow preventing means is provided, which reduces a recovery electric current occurring in the event of backflow of an electric current so as to ensure high efficiency, high reliability, etc. The backflow preventing means includes a backflow preventing element, such as a rectifying element, which is connected between an alternating-current power supply and a load and prevents the electric current from flowing backward from the load toward the alternating-current power supply; and commutating means for performing a commutation operation for causing the electric current to flow toward a different path that is connected in parallel with the backflow preventing element, whereby a conduction loss and a loss caused by the electric current can be reduced.