DC Voltage Conversion Circuit Ripple Cancellation

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Solution Overview

Problem

Step-up converters face stability issues due to a zero point on the right half plane of the Laplace plane, leading to a narrow control band that hinders rapid load fluctuation response and miniaturization, and existing magnetic flux cancellation technologies require special multi-leg magnetic cores that are difficult to implement with general magnetic cores.

Innovation Solution

A non-isolated DC voltage conversion circuit using two sets of magnetic flux cancellation conversion circuits with primary and secondary windings in two stages, canceling ripple current without a special multi-leg magnetic core, allowing for reduced inductance and increased control band frequency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a large capacity output capacitor is used to suppress output voltage fluctuation in a step-up converter, then voltage stability is improved, but the device size increases and miniaturization is hindered

Engineering Contradiction:

Improveoutput voltage stabilityVSAvoidcapacitor size

Core Design Contradiction:

ReliabilityVSVolume of moving object

Solution Approach 1:

The patent converts the harmful ripple current, which is an inherent byproduct of switching operation, into a beneficial effect by using it to cancel magnetic flux in the transformer. This allows the system to achieve voltage stability without requiring large output capacitors, as the ripple energy is productively utilized rather than suppressed.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The patent changes the operating parameters by using high-frequency switching and optimizing the transformer turns ratio to achieve efficient voltage conversion. This allows for smaller energy storage components while maintaining stability, as the high-frequency operation reduces the required capacitance for the same filtering effect.

Inventive Principle:

Principle #35Parameter changes

2Volume of moving object

If magnetic flux cancellation technology is used to reduce ripple current and miniaturize inductors, then inductor size is reduced, but special multi-leg magnetic cores are required which are difficult to implement

Engineering Contradiction:

Improveinductor sizeVSAvoidmagnetic core implementation

Core Design Contradiction:

Volume of moving objectVSEase of manufacture

Solution Approach 1:

The patent makes the transformer serve multiple functions: it performs the essential voltage step-up function while simultaneously acting as a magnetic flux cancellation device. By using the transformer's secondary winding to cancel ripple current in the primary winding, the system achieves flux cancellation without requiring separate specialized magnetic cores or multi-leg structures.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The patent merges the voltage conversion function and the ripple cancellation function into a single transformer component. The transformer is designed so that its windings interact to produce both the desired voltage transformation and the automatic cancellation of magnetic flux, eliminating the need for separate cancellation mechanisms or special multi-leg cores.

Inventive Principle:

Principle #5Merging (Combining)

3Speed

If control band frequency is increased to improve transient response to load fluctuation, then response speed is improved, but stability is compromised due to the right half plane zero point

Engineering Contradiction:

Improvetransient response speedVSAvoidsystem stability

Core Design Contradiction:

SpeedVSReliability

Solution Approach 1:

The patent converts the typically harmful high-frequency ripple current into a beneficial automatic stabilization mechanism. The ripple current, when used to cancel magnetic flux in the transformer, creates a natural feedback effect that improves transient response without compromising stability, allowing the system to respond quickly to load changes while maintaining controlled stability.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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

The solution effectively reduces ripple current, miniaturizes inductors and capacitors, and enhances the control band frequency, enabling faster transient responses and stability in step-up converters using general magnetic cores.

Implementation Method 1

a first magnetic flux cancellation type transformer T1... One end of the primary winding CL1 and the other end of the secondary winding CL2 of the first magnetic flux cancellation type transformer T1 are connected to one end of an inductor L1

Methodology Applied

Scientific EffectMagnetic flux cancellation: Electromagnetic Induction

Data Source

PatentEP3496252B1DC voltage conversion circuit

Publication Date: 2022.11.30 MITSUBISHI ELECTRIC CORP

Figure 1
Figure 2~3
Figure 4~5

AI summary

It is desired to provide a DC voltage conversion circuit (1) in which the miniaturization of the inductor is attained and the frequency of control band can be widened, by suppressing the ripple current which flows into the inductor using a general magnetic core without using a special multi-leg magnetic core. A DC voltage conversion circuit (1) is provided with two sets of magnetic flux cancellation conversion circuits (10, 11) each of which is provided with two sets of series circuits of two semiconductor circuits, a first magnetic flux cancellation type transformer (T1, T2), and an inductor (L1); a second magnetic flux cancellation type transformer (Ta) connected to the two sets of magnetic flux cancellation conversion circuits (10, 11); and a control circuit (12) which controls switching devices of semiconductor circuits.