Active Clamp Flyback Control Across a Galvanic Isolation Barrier

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Conventional flyback converters in USB power delivery systems face inefficiencies due to the lack of intelligence in primary-side controllers, leading to unnecessary active clamp FET engagement and energy wastage, as well as the need for additional components and increased costs for high-speed communication links across galvanic isolation barriers.

Innovation Solution

Implementing a secondary-controlled active clamp FET and primary-side FET control using a dual-level pulse transformer drive scheme, which allows the secondary-side controller to manage the active clamp FET and primary-side FET without additional external components, optimizing switching timing and reducing electromagnetic interference.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If a primary-side controller is used in conventional flyback converters, then the control simplicity is maintained, but the intelligence for optimizing active clamp FET engagement is insufficient leading to energy wastage

Engineering Contradiction:

Improveenergy wastageVSAvoidcontroller intelligence

Core Design Contradiction:

Loss of energyVSExtent of automation

Solution Approach 1:

The patent inverts the conventional control architecture by placing the intelligent controller on the secondary side instead of the primary side. The secondary-side controller now generates control signals that are transmitted back to the primary side through a pulse transformer to optimize the active clamp FET engagement, thereby reducing energy wastage while maintaining control simplicity through the existing transformer interface.

Inventive Principle:

Principle #13The other way round (Inversion)

2Speed

If additional communication links are added across galvanic isolation barriers, then high-speed control capability is improved, but device complexity and cost increase

Engineering Contradiction:

Improvecontrol signal speedVSAvoidcommunication link components

Core Design Contradiction:

SpeedVSDevice complexity

Solution Approach 1:

The patent makes the existing pulse transformer multi-functional by using it not only for power isolation but also for bidirectional control signal transmission. The secondary-side controller utilizes the transformer's primary winding to send control signals back to the primary side, eliminating the need for separate communication links and reducing overall device complexity while maintaining high-speed control capability.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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

This approach enhances efficiency by 3-4% and eliminates the need for extra components, improving power delivery while reducing costs and board space requirements.

Implementation Method 1

a pulse transformer coupled between the primary-side controller and the secondary-side controller

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Data Source

PatentUS12143023B2Drive scheme for secondary-controlled active clamp flyback (ACF) mode

Publication Date: 2024.11.12 INFINEON TECHNOLOGIES AMERICAS CORP

AI summary

Controlling an active clamp field effect transistor (FET) and a primary-side FET in a secondary-controlled active clamp converter is described. In one embodiment, an apparatus includes a primary-side FET coupled to a transformer and an active clamp FET disposed on a primary side of the transformer. A secondary-side controller is configured to control the active clamp FET and the primary-side FET across a same galvanic isolation barrier.