Active-Clamped Flyback Converter for Bidirectional DC Power Flow

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Solution Overview

Problem

Existing DC-DC converters with active-clamped flyback topology are primarily designed for unidirectional power transmission from a higher voltage primary side to a lower voltage secondary side, lacking efficient mechanisms for bidirectional power flow without increasing circuit complexity.

Innovation Solution

A DC-DC converter with a control device that manages the switching of three switches to enable bidirectional power transmission by adjusting the timing of switch operations, allowing power to flow from the secondary side to the primary side with minimal additional electronic components, using a galvanically isolating transformer and actively clamped flyback converter circuit.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If the DC-DC converter uses active-clamped flyback topology with controlled rectifier for unidirectional power transmission from primary side to secondary side, then the circuit complexity is reduced, but the capability for bidirectional power transmission is lost

Engineering Contradiction:
Improvebidirectional power transmission capabilityVSAvoidcircuit complexity
Core Design Contradiction:
Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent applies universality by enabling the same active-clamped flyback converter circuit to perform both unidirectional (primary to secondary) and bidirectional (secondary to primary) power transmission functions. The controlled rectifier on the secondary side and the actively clamped primary side work together to allow power flow in both directions without requiring separate circuit topologies, thus achieving multi-functionality with a single circuit design.

Inventive Principle:
Principle #6Universality (Multi-functionality)

Solution Approach 2:

The patent implements inversion by reversing the conventional power flow direction. Instead of only allowing power transmission from the high-voltage primary side to the low-voltage secondary side, the controlled rectifier and active clamping mechanism enable power to be transmitted from the secondary side back to the primary side, effectively inverting the traditional unidirectional operation mode.

Inventive Principle:
Principle #13The other way round (Inversion)

2Adaptability or versatility

If additional electronic components are added to enable bidirectional power flow, then the bidirectional transmission capability is improved, but the circuit complexity increases

Engineering Contradiction:
Improvereverse power flow capabilityVSAvoidnumber of electronic components
Core Design Contradiction:
Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The existing controlled rectifier and active clamping components are made multi-functional by controlling them to operate in reverse mode. The same switches and control circuitry that enable primary-to-secondary power transmission are utilized to enable secondary-to-primary power transmission, eliminating the need for additional dedicated components for bidirectional operation.

Inventive Principle:
Principle #6Universality (Multi-functionality)

Solution Approach 2:

The converter uses its own existing components (controlled rectifier, active clamp circuit, switching devices) to enable bidirectional operation without requiring external assistance or additional specialized components. The control device orchestrates the existing hardware to perform reverse power flow, making the system self-sufficient for bidirectional transmission.

Inventive Principle:
Principle #25Self-service

3Adaptability or versatility

If the switching timing is adjusted to enable power flow from secondary side to primary side, then the bidirectional transmission is achieved, but the control complexity increases

Engineering Contradiction:
Improvepower transmission direction controlVSAvoidcontrol pattern complexity
Core Design Contradiction:
Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The control system dynamically adjusts the switching timing of the controlled rectifier and primary side switches based on the desired power transmission direction. The control device modifies duty cycles and switching sequences in real-time to enable flexible bidirectional operation, making the control pattern adaptive rather than fixed.

Inventive Principle:
Principle #15Dynamics

Solution Approach 2:

The patent changes operational parameters (switching timing, duty cycle, gate control signals) to transition between unidirectional and bidirectional power transmission modes. By adjusting these parameters, the same hardware can efficiently transmit power in either direction without requiring fundamental changes to the control architecture.

Inventive Principle:
Principle #35Parameter changes

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

Enables efficient bidirectional power transmission with reduced switching and conduction losses, allowing power to be transferred from the secondary side to the primary side without additional circuit complexity, while maintaining high efficiency and adaptability in power transmission direction.

Implementation Method 1

A DC-DC converter is provided for transmitting electrical power from a secondary side to a primary side of the DC-DC converter. The DC-DC converter comprises a galvanically isolating transformer with a primary coil on the primary side and a secondary coil on the secondary side.

Methodology Applied
Scientific EffectElectromagnetic induction: Electromagnetic Induction

Data Source

PatentEP3900172B1Direct-current voltage converter for bidirectional electrical power transmission from a primary side to a secondary side of the direct-current voltage converter or vice versa
Publication Date: 2024.02.28 ROBERT BOSCH GMBH
  • EP3900172B1 patent drawingFigure 1
  • EP3900172B1 patent drawingFigure 2a~2b

AI summary

The invention relates to a direct-current voltage converter (10) for electrical power transmission from a secondary side to a primary side of the direct-current voltage converter (10), which has on the primary side an actively clamped flyback converter circuit having a controlled first switch (1) and a controlled second switch (2), and the primary side is inductively coupled to the secondary side. The current of a secondary coil (6) on the secondary side, for inductive coupling to the primary side, is switched by a single controlled third switch (3) on the secondary side, and the direct-current voltage converter has a regulator (12) which, in parts of a regulating cycle, conductively connects the third switch (3) to the first switch (1).