Secondary-Side Peak Current Flyback Control for Faster Transients

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Solution Overview

Problem

Existing secondary-side controlled flyback converters operate in voltage mode, leading to complex stabilization and reduced transient response, which results in inefficiencies and increased component stress, especially in power adapters where power factor correction (PFC) is not necessary at lower power modes.

Innovation Solution

Implementing secondary-side peak current controlled flyback converters that operate in current mode, allowing for improved transient response and reduced complexity by generating PWM signals based on derived line and load parameters, eliminating the need for type-3 compensation and reducing the number of external components.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If secondary-side controlled flyback converters operate in voltage mode, then the control is stable, but the transient response is reduced and the complexity of stabilization increases

Engineering Contradiction:

Improvecontrol stabilityVSAvoidstabilization complexity

Core Design Contradiction:

Stability of the object's compositionVSDevice complexity

Solution Approach 1:

The patent changes the control parameter from voltage mode to current mode operation. By controlling the peak current on the secondary side rather than using voltage feedback, the system achieves both stability and improved transient response. The current mode control inherently provides cycle-by-cycle current limiting and simplifies the compensation network requirements.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent replaces the complex voltage-mode stabilization mechanism with a simpler current-mode control mechanism. By using current sensing and control on the secondary side, the system eliminates the need for complex type-3 compensation networks and associated components required in voltage-mode operation.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Stability of the object's composition

If secondary-side controlled flyback converters operate in voltage mode, then the control is stable, but the transient response is reduced

Engineering Contradiction:

Improvecontrol stabilityVSAvoidtransient response

Core Design Contradiction:

Stability of the object's compositionVSSpeed

Solution Approach 1:

Inventive Principle:

Principle #35Parameter changes

3Stability of the object's composition

If type-3 compensation is used for stabilization, then the control is stable, but the number of external components increases

Engineering Contradiction:

Improvecontrol stabilityVSAvoidnumber of external components

Core Design Contradiction:

Stability of the object's compositionVSQuantity of substance

Solution Approach 1:

The patent extracts and eliminates the type-3 compensation network from the system by transitioning to current-mode control. This removes the need for multiple external components (resistors, capacitors) that would otherwise be required to implement type-3 compensation, while maintaining stability through the inherent current-mode control mechanism.

Inventive Principle:

Principle #2Taking out (Extraction)

4Object-generated harmful factors

If power factor correction is implemented, then the power factor improves, but the device complexity and cost increase

Engineering Contradiction:

Improvepower factorVSAvoiddevice complexity

Core Design Contradiction:

Object-generated harmful factorsVSDevice complexity

Solution Approach 1:

The patent makes the secondary-side controller universal by enabling it to perform both power factor correction and primary-side controller functions. This multi-functionality eliminates the need for a separate PFC circuit, reducing device complexity and cost while maintaining improved power factor performance through the same current-mode control mechanism.

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, reduces resource consumption, and increases flexibility, allowing for smaller footprints and lower manufacturing costs while maintaining high power delivery performance comparable to primary-side controlled designs.

Implementation Method 1

A flyback transformer separates the primary side from the secondary side to enable galvanic isolation and prevent direct current flow from the primary side to the secondary side

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Data Source

PatentUS20240388213A1Secondary side peak current controlled mode flyback converter

Publication Date: 2024.11.21 INFINEON TECHNOLOGIES AMERICAS CORP

AI summary

Secondary side peak current control mode flyback converters are described. In one embodiment, an apparatus includes a flyback converter including a flyback transformer and a signal transformer, a primary side including a primary-side controller coupled to a power switch, the flyback transformer and the signal transformer, and a secondary side including a secondary-side controller coupled to the flyback transformer and the signal transformer. The secondary-side controller is configured at least to operate in a current control mode to cause a pulse width modulation (PWM) signal to be generated based on a set of parameters to control operation of the primary-side controller.