Flyback Converter Adaptive Power Factor Correction

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Solution Overview

Problem

Single-stage flyback converters face a trade-off between achieving high power factor correction and reducing output voltage ripple, with conventional methods either resulting in undesirable ripple or decreased power factor.

Innovation Solution

Implementing a mixed-mode control strategy in the flyback switching power converter, alternating between constant peak current and constant switch on time modes within each AC power main cycle to achieve a balanced power factor and reduced output voltage ripple.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If constant on time control is used for power factor correction, then power factor is improved, but output voltage ripple increases

Engineering Contradiction:

Improvepower factorVSAvoidoutput voltage ripple

Core Design Contradiction:

Loss of energyVSManufacturing precision

Solution Approach 1:

The control period is segmented into multiple sub-periods within each AC line cycle. During some sub-periods, constant on-time control is applied to maintain high power factor, while during other sub-periods, constant peak current control is applied to reduce output voltage ripple. This temporal segmentation allows the system to achieve both high power factor and low output ripple that cannot be achieved with a single control mode throughout the entire cycle.

Inventive Principle:

Principle #1Segmentation

2Manufacturing precision

If constant peak current control is used, then output voltage ripple is reduced, but power factor decreases

Engineering Contradiction:

Improveoutput voltage rippleVSAvoidpower factor

Core Design Contradiction:

Manufacturing precisionVSLoss of energy

Solution Approach 1:

The controller periodically alternates between constant on-time control mode and constant peak current control mode within each AC line cycle. By strategically selecting which sub-periods use which control mode, the system achieves periodic action that balances power factor correction with output voltage ripple reduction, optimizing overall converter performance.

Inventive Principle:

Principle #19Periodic action

3Manufacturing precision

If multi-stage approach is used with DC-DC converter, then output voltage regulation is improved, but device complexity and cost increase

Engineering Contradiction:

Improveoutput voltage regulationVSAvoidcontrol complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The flyback converter is designed to perform multiple functions through a single-stage architecture. By implementing mixed-mode control that combines power factor correction and output voltage regulation capabilities within the same converter stage, the system eliminates the need for separate DC-DC conversion stages, thereby reducing device complexity and cost while maintaining good output voltage regulation.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The patent merges the power factor correction function and output voltage regulation function into a single integrated flyback converter stage. The mixed-mode control strategy combines aspects of both constant on-time and constant peak current control within the same converter, achieving both high power factor and good voltage regulation without requiring separate conversion stages.

Inventive Principle:

Principle #5Merging (Combining)

Data Source

PatentUS9584008B2Switching power converter with adaptive power factor correction

Publication Date: 2017.02.28 DIALOG SEMICONDUCTOR INC

AI summary

A switching power converter is provided that provides an adaptive power factor correction using a peak constant current mode and also a constant on time mode during each cycle of an input voltage.