Isolated Bidirectional DC Converter With Sampled Synchronous Rectification

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Solution Overview

Problem

Traditional bi-directional DC converter circuits struggle to balance stability, size, and cost, making it difficult to meet the higher requirements for safety, compactness, and cost in electric vehicles with 800V battery packs.

Innovation Solution

An isolated bi-directional DC conversion circuit with a transformer, primary-side and secondary-side rectification bridges, and a controller that performs switch control based on sampled voltages of sampling resistors to achieve synchronous rectification, minimizing conduction losses and avoiding stability issues.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If traditional bi-directional DC converter circuit designs are used, then the circuit can perform bidirectional power conversion, but the circuit fails to balance stability, size, and cost effectively

Engineering Contradiction:

ImprovestabilityVSAvoidcircuit design complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent implements self-service through body diode synchronous rectification where the body diodes of the switching devices perform rectification functions automatically during specific operation phases. The control system utilizes the inherent body diodes rather than requiring separate rectification components, allowing the circuit to serve its own rectification needs and reducing overall system complexity while maintaining stability

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The switching devices in the patent serve multiple functions: power switching, synchronous rectification through body diodes, and bidirectional power flow control. This multi-functionality eliminates the need for separate rectification components, reducing device complexity while maintaining reliable bidirectional operation

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Ease of manufacture

If traditional bi-directional DC converter circuit designs are used, then the circuit can perform bidirectional power conversion, but the circuit size and cost increase

Engineering Contradiction:

ImprovecostVSAvoidconduction losses

Core Design Contradiction:

Ease of manufactureVSLoss of energy

Solution Approach 1:

The patent converts the typically parasitic body diodes of switching devices into beneficial rectification elements. By utilizing the inherent body diodes for synchronous rectification during specific operation phases, the design eliminates the need for separate rectification diodes or transistors, reducing component count, circuit size, and manufacturing cost while minimizing conduction losses through optimized current paths

Inventive Principle:

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

3Volume of moving object

If traditional bi-directional DC converter circuit designs are used, then the circuit can perform bidirectional power conversion, but the circuit lacks compactness

Engineering Contradiction:

Improvecircuit sizeVSAvoidstability

Core Design Contradiction:

Volume of moving objectVSReliability

Solution Approach 1:

The patent merges the rectification function into the switching devices themselves by utilizing their body diodes. This consolidation eliminates the need for separate rectification components and reduces the overall circuit footprint. The control system coordinates the switching devices to perform both power switching and rectification functions, achieving compactness without sacrificing bidirectional operation stability

Inventive Principle:

Principle #5Merging (Combining)

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 reduces conduction losses, avoids stability problems, and achieves miniaturization and cost-effectiveness in bi-directional power conversion circuits.

Implementation Method 1

a transformer with at least one first energy storage element

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Implementation Method 2

each of the multiple first power switching devices and the second power switching devices having a body diode in inverse parallel connection therewith

Methodology Applied

Scientific EffectDiode conduction: Diode

Data Source

PatentUS12463545B2Isolated bi-directional DC conversion circuit and method for controlling the same

Publication Date: 2025.11.04 APTIV ELECTRIC SYST CO LTD

AI summary

An isolated bi-directional DC conversion circuit and a method for controlling the same are provided. The DC conversion circuit includes a transformer with a first energy storage element and a primary-side rectification bridge coupled to the primary side of the transformer and a second energy storage element and a secondary-side rectification bridge coupled to the secondary side of the transformer. The primary-side rectification bridge consists of multiple first power switching devices. The secondary-side rectification bridge consists of multiple second power switching devices. Each of the multiple first and the second power switching devices have a body diode in inverse parallel connection therewith. The DC conversion circuit further includes multiple first sampling resistors provided on each bridge arm of the secondary-side rectification bridge and a controller configured to perform switch control on the multiple second power switching devices based on a sampled voltage of the multiple first sampling resistors.