Skip to main content
APEC 2025 Main banner
Back

Technical Dialogue

Parasitics Extraction and Optimization

D16.3 - Optimal Transformer Design with Additional Common-Mode Noise Reduction Winding for Flyback DC-DC Converters

Thursday, March 20, 2025
11:30 AM – 1:30 PM ET
Location: Level One, Hall A3
This paper proposes a method and theory for reducing conducted noise in the frequency range of 150 kHz to 30 MHz in accordance with CISPR16 for flyback converter circuits. Among conducted noise, we focus on common-mode noise, which is the most important to counteract. Common countermeasures include choke coils and Y capacitors, but they have the disadvantage of increasing the circuit volume. Therefore, we focused on transformers used in switching power supplies and confirmed that the volume can be reduced by 6% by adding shielded windings between the primary and secondary windings and designing the optimal number of turns. In other studies, the transformer structure is simplified and theorized in the analysis, but in this study, based on practical applications, the design is theorized so that it can be analyzed even with a complex structure and the variation of the transformer due to transformer design errors is taken into account. By using shielded windings, a 98.3% CM noise reduction was confirmed. In addition, the number of shielded windings turns optimal for common-mode noise suppression is shown through measurements on actual equipment in compliance with the CISPR standard.