Flyback Converter Rectification for Secondary-Side ZVS Switching

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Existing flyback converters are inefficient, bulky, and generate significant EMI emissions due to hard switching modes and lack of optimal design for size and cost.

Innovation Solution

The implementation of a flyback converter topology that includes a primary side control unit and a secondary side valley synchronizer unit, utilizing Zero Voltage Switching (ZVS) and regenerative clamp techniques to improve efficiency and reduce EMI.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If hard switching mode is used in rectifier section, then device complexity is reduced, but efficiency deteriorates due to high losses in turn on and turn off of primary side MOSFET

Engineering Contradiction:

Improveswitching control complexityVSAvoidswitching losses

Core Design Contradiction:

Device complexityVSLoss of energy

Solution Approach 1:

The patent changes the switching parameter from hard switching to Zero Voltage Switching (ZVS) by introducing a valley synchronizer that detects the resonant valley and triggers the MOSFET gate signal accordingly. This parameter change eliminates switching losses while maintaining relatively simple device complexity through automated valley detection and synchronization.

Inventive Principle:

Principle #35Parameter changes

2Object-generated harmful factors

If EMI filters are increased in size to reduce EMI emissions, then harmful emissions are reduced, but device volume increases

Engineering Contradiction:

ImproveEMI emissionsVSAvoidfilter size

Core Design Contradiction:

Object-generated harmful factorsVSVolume of stationary object

Solution Approach 1:

The patent converts the harmful EMI emissions into a beneficial signal by using the resonant valley (which would normally be a source of EMI) as a timing reference for ZVS synchronization. The valley synchronizer detects the resonant valley and uses it to trigger the MOSFET gate signal, thereby eliminating the source of EMI while reducing the need for large EMI filters.

Inventive Principle:

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

3Volume of stationary object

If converter size is reduced for compactness, then device volume decreases, but efficiency deteriorates due to compromised design optimization

Engineering Contradiction:

Improveconverter sizeVSAvoidconversion efficiency

Core Design Contradiction:

Volume of stationary objectVSLoss of energy

Solution Approach 1:

The patent implements a universal ZVS control mechanism that works across different converter sizes and power levels. The valley synchronizer and resonant control approach can be applied to both compact and larger converters, ensuring optimal efficiency regardless of size. This multi-functionality allows the same control strategy to maintain efficiency in space-constrained applications.

Inventive Principle:

Principle #6Universality (Multi-functionality)

4Device complexity

If conventional flyback topology is used, then device complexity is low, but efficiency deteriorates due to lack of optimal design for various load conditions

Engineering Contradiction:

Improvetopology complexityVSAvoidconversion efficiency

Core Design Contradiction:

Device complexityVSLoss of energy

Solution Approach 1:

The patent introduces dynamic control to the conventional flyback topology by implementing a valley synchronizer that adapts to varying load conditions. The system dynamically adjusts the switching timing based on real-time resonant valley detection, maintaining optimal ZVS operation across different load levels while preserving the simplicity of the basic flyback topology.

Inventive Principle:

Principle #15Dynamics

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 the efficiency and reduces the size of flyback converters while minimizing EMI emissions, thereby addressing the limitations of existing designs.

Implementation Method 1

the lowest drain voltage valleys generated by the resonance between the primary inductance and parasitic capacitance of the circuit

Methodology Applied

Scientific EffectResonance: Resonance

Implementation Method 2

a secondary side valley synchronizer unit, configured to detect a voltage valley of the secondary winding

Methodology Applied

Scientific EffectVoltage valley detection:

Implementation Method 3

utilizing Zero Voltage Switching (ZVS) and regenerative clamp techniques to improve efficiency and reduce EMI

Methodology Applied

Scientific EffectEnergy recovery:

Data Source

PatentUS20250149994A1Improved performance of a flyback converter

Publication Date: 2025.05.08 EGGTRONIC ENG SPA

AI summary

A flyback converter comprising: a transformer having a primary side winding and a secondary side winding; a primary side switch located at the primary side of the transformer; two secondary side switches located at the secondary side of the transformer; in which the two secondary side switches are connected in parallel and have different characteristics; and a control unit configured to generate a rectification signal and a Zero Voltage Switching (ZVS) pulse and to drive the two secondary side switches; in which a secondary side switch is driven by the rectification signal and the other secondary side switch is driven by the ZVS pulse. At the end of a switching cycle, before turning on the primary side switch: the control unit is configured to generate the ZVS pulse in the secondary side winding such that the parasitic capacitor of the primary side switch is discharged, and to consequently turn on the primary side switch in ZVS conditions or near ZVS conditions.