STMicroelectronics AN1059 L6561 High-PF Flyback Converter Design Equations Application Note

About this manual

The document describes how to use the L6561 integrated circuit, typically designed for boost topology power factor correction circuits, to control high-power-factor (high-PF) flyback converters. It details three configurations of L6561-based flyback converters, highlighting that configuration c) is particularly suitable for AC-DC adapters and low-power SMPS applications due to its ability to achieve a power factor greater than 0.9.

What's inside

• Introduction
• High-PF Flyback Configuration
• Timing Relationships
• Energetic Relationships
• Internal Block Diagram of the L6561

Frequently asked questions

What is the minimum switching frequency required for correct TM operation?

The calculated minimum frequency must be greater than 14 kHz to ensure correct TM operation.

What happens when the load is so low that many cycles need to be skipped?

The amplitude of the drain voltage ringing becomes so small that it can no longer trigger the ZCD Block of the L6561.