Parallel-Connected Resonant Converter Circuit for Current Balancing

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Solution Overview

Problem

Resonant DC/DC converters face challenges in achieving current balance among converters operating at the same switching frequency, leading to high power loss and large output filter volumes due to high ac current ripples in the output filter.

Innovation Solution

A parallel-connected resonant DC/DC converter circuit and controlling method where all input terminals are series-connected and output terminals are parallel-connected, allowing for automatic current balancing by adjusting input and output voltages and currents across resonant converters operating at the same frequency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If resonant converters operate at the same switching frequency, then frequency synchronization is achieved, but current balance among converters cannot be realized

Engineering Contradiction:

Improveswitching frequency synchronizationVSAvoidcurrent balance control

Core Design Contradiction:

Stability of the object's compositionVSEase of operation

Solution Approach 1:

The patent inverts the conventional control approach by series-connecting the input terminals instead of parallel connection. This inversion creates an automatic current balance mechanism where converters operating at the same frequency naturally share current proportionally to their input voltages, eliminating the need for complex current balancing control while maintaining frequency synchronization

Inventive Principle:

Principle #13The other way round (Inversion)

2Reliability

If traditional parallel connection is used, then converter redundancy is improved, but current balance cannot be achieved at same frequency

Engineering Contradiction:

Improveconverter redundancyVSAvoidcurrent balance control

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The patent applies series connection of input terminals (inversion of traditional parallel connection) to achieve both converter redundancy and automatic current balance. This configuration allows multiple converters to operate in parallel at the output while maintaining current balance through the series input connection, resolving the contradiction between reliability and ease of operation

Inventive Principle:

Principle #13The other way round (Inversion)

3Volume of stationary object

If interleaved control method is used, then output filter size is reduced, but current balance is difficult to realize in resonant converters

Engineering Contradiction:

Improveoutput filter sizeVSAvoidcurrent balance control

Core Design Contradiction:

Volume of stationary objectVSEase of operation

Solution Approach 1:

The patent uses series connection of input terminals to create an automatic current balance mechanism that works naturally with resonant converters operating at the same frequency. This eliminates the need for interleaved control methods while still achieving reduced output filter size through the inherent current balancing property of the series input configuration

Inventive Principle:

Principle #13The other way round (Inversion)

Data Source

PatentUS8842448B2Parallel-connected resonant converter circuit and controlling method thereof

Publication Date: 2014.09.23 DELTA ELECTRONICS INC(CN)

AI summary

The configurations of a parallel-connected resonant converter circuit and a controlling method thereof are provided in the present invention. The proposed circuit includes a plurality of resonant converters, each of which has two input terminals and two output terminals, wherein all the two input terminals of the plurality of resonant converters are electrically series-connected, and all the two output terminals of the plurality of resonant converters are electrically parallel-connected.