International Rectifier IRIS40xx Application Note

About this manual

The document provides a detailed guide for engineers designing flyback transformers used with the IRIS40xx series SMPS ICs. It defines required power‑supply parameters such as input voltage, output power, minimum frequency and maximum duty cycle before proceeding to calculations.

Key topics include transformer design methodology, selection of magnetic core types, wire‑gauge tables, winding ratio calculations, and a list of recommended component suppliers. Safety and creepage requirements are also addressed, with references to UL1950 and EN60950 standards. This manual is written in Chinese.

What's inside

• Introduction to Flyback Transformer Design
• Power Supply Design Standards
• Transformer Design Steps
• Transformer Structure
• Magnetic Core Types
• Wire Gauge Table
• Reference Materials
• Transformer Component Sources

Specifications

Frequently asked questions

What is the recommended maximum duty cycle for IRIS40xx designs?

The application note recommends a maximum duty cycle of 0.5.

Which magnetic core is suggested for a 0‑10 W IRIS40xx flyback transformer?

For power levels of 0‑10 W, the note suggests using an EFD15 core.

What wire gauge should be used for the primary winding?

The primary winding should use wire no larger than 26 AWG to keep the winding capacitance low.

What safety standards apply to the transformer design?

The design follows UL1950 in the United States and EN60950 (IEC950) in Europe.