Design Methodology for Coupled Inductors Aimed at Reducing Leakage Inductance, Proximity Effect, and Electromagnetic Interference in Quasi-Resonant Flyback LED Drivers

João R. C. Amado; Kalyl S. A. Ali; Giulia K. Grassi; Hentony A. Lobo; Renan Rodrigo Duarte; Marco  A. D. Costa

doi:10.18618/REP.e202607

Authors

João R. C. Amado Federal University of Santa Maria https://orcid.org/0009-0003-7923-5696
Kalyl S. A. Ali Federal University of Santa Maria https://orcid.org/0009-0002-4565-0376
Giulia K. Grassi Federal University of Santa Maria https://orcid.org/0009-0007-5430-4260
Hentony A. Lobo Federal University of Santa Maria https://orcid.org/0009-0004-7153-885X
Renan Rodrigo Duarte Federal University of Santa Maria https://orcid.org/0000-0001-8427-8621
Marco A. D. Costa Federal University of Santa Maria https://orcid.org/0000-0003-1233-6858

DOI:

https://doi.org/10.18618/REP.e202607

Keywords:

Coupled inductor, flyback, LED driver, leakage inductance, proximity effect

Abstract

This paper presents a comprehensive study on the influence of winding geometry on leakage inductance and proximity effect losses in coupled inductors applied to quasi-resonant flyback converters for LED drivers. Eleven coupled inductors were designed using the same PQ3220 core, varying the number of layers, interleaving level, and wiring geometry to evaluate their impact on performance. The leakage inductance of each inductor was calculated analytically and measured experimentally, showing strong correlation and validating the analytical method. Additionally, proximity effect losses were estimated through simulations based on winding temperature measurements, allowing the extraction of the AC resistance and proximity factor for each design. The experimental setup involved a 60 W quasi-resonant flyback LED driver operating at around 50 V output, where voltage spikes on the MOSFET, system efficiency, and critical component temperatures were analyzed. Results show that increasing the interleaving level significantly reduces leakage inductance, proximity losses, and electromagnetic emissions, leading to improved efficiency, lower thermal stress, and facilitated regulatory compliance. This study highlights the importance of magnetic design in achieving high-performance LED drivers and provides practical guidelines for minimizing parasitic effects in coupled inductors without increasing component count.

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Author Biographies

João R. C. Amado, Federal University of Santa Maria

was born in Cruz Alta, Brazil, in 1996. He received the B.S. degree in Control and Automation Engineering from the Federal University of Santa Maria (UFSM), Santa Maria, Brazil, in 2021, and the M.Sc. degree in Electrical Engineering from UFSM in 2025. He is currently a Ph.D. candidate, also at UFSM. He has been a member of GEDRE – Intelligence in Lighting Group at UFSM since 2018 and has collaborated with Zagonel Iluminação S.A. since 2021. His work focuses on magnetic components and power density optimization for LED drivers. His research interests include power electronics applied to lighting systems, magnetic component design, and lighting products and applications

Kalyl S. A. Ali, Federal University of Santa Maria

was born in Guaíra, Brazil, in 2003. He is currently pursuing a Bachelor’s degree in Electrical Engineering at the Federal University of Santa Maria (UFSM). Since 2023, he has been a member of GEDRE – Intelligence in Lighting Group, at UFSM. His research involves finite element simulations applied to power electronics, including magnetic component modeling and analysis. His interests include power electronics and finite element analysis.

Giulia K. Grassi, Federal University of Santa Maria

was born in Santa Maria, Brazil, in 2001.She received the B.S. degree in Electrical Engineering from the Federal University of Santa Maria (UFSM), Santa Maria, Brazil, in 2025. She is currently seeking the M.Sc. degree, also at the Federal University of Santa Maria. Since 2019, she has been a member of the GEDRE – Intelligence in Lighting Group, at UFSM. Her work has focused on high power density LED drivers and GaN semiconductors. Her main areas of interest are power electronic systems, LED drivers and artificial intelligence applied to lighting systems.

Hentony A. Lobo, Federal University of Santa Maria

was born in the city of Rio Grande, in the state of Rio Grande do Sul, Brazil, in 2001. He received his technical degree in Electrotechnics in 2020 from the Technical College of Santa Maria (CTISM). He is currently pursuing a Bachelor’s degree in Control and Automation Engineering at the Federal University of Santa Maria (UFSM). Since 2022, he has been a member of GEDRE – Intelligence in Lighting Group, at UFSM. His research involves inductor design, as well as the analysis of operation and control of converters. His interests include control of power electronic systems, artificial intelligence, and technological innovation in embedded systems design using artificial intelligence.

Renan Rodrigo Duarte, Federal University of Santa Maria

received the B.S., M.Sc., and Ph.D. degrees in Electrical Engineering from the Federal University of Santa Maria (2015, 2017, and 2022, respectively). He completed a curricular internship at Fraunhofer IZM in Berlin, Germany, in the RF Smart Sensor Systems department (2014-2015) and worked as a senior designer at Zagonel S.A., focusing on hardware and embedded firmware design and development (2020-2023). Since 2023, he has been a professor at the Federal University of Santa Maria (UFSM). His main research areas include artificial lighting systems, high-efficiency converters, and GaN semiconductors.

Marco A. D. Costa, Federal University of Santa Maria

received his B.S. and M.Sc. degrees in Electrical Engineering from the Federal University of Santa Maria, Brazil, in 2002 and 2004, respectively. He earned his Ph.D. degree (with honors) in Electrical Engineering from the University of Oviedo, Spain, in 2008. Since 2009, he has been serving as a Professor at the Federal University of Santa Maria, Brazil. Dr. Dalla Costa has co-authored over 240 journal and conference papers. His research interests include power electronics applied to lighting systems, LED drivers, LED modeling, horticultural lighting, and visible light communication systems. Since 2018, he has been serving as an Associate Editor for the IEEE Transactions on Industrial Electronics and the IEEE Journal of Emerging and Selected Topics in Power Electronics. Additionally, he chaired the IEEE Industry Applications Society’s ILDC (2019–2020) and MSDAD (2020–2021).

References

J. R. C. Amado, K. S. A. Ali, R. R. Duarte, H. Lobo, G. Grassi, M. A. D. Costa, Técnicas de Redução da Indutância de Dispersão em Indutores Acoplados Utilizados em Conversores Flyback Quase Ressonantes como Drivers de LEDs”, in Proceedings of the 16thSeminar on Power Electronics and Control (SEPOC), Santa Maria, Brasil, 2024, doi:10.53316/sepoc2024.019.

G. Z. Abdelmessih, J. M. Alonso, M. S. Perdigˆao, “Hybrid series-parallel PWM dimming technique for integrated-converter-based HPF LED drivers”, in 2016 51st International Universities Power Engineering Conference (UPEC), pp. 1–6, 2016, doi:10.1109/UPEC.2016.8113996.

H. van der Broeck, G. Sauerlander, M. Wendt, “Power driver topologies and control schemes for LEDs”, in APEC 07 - Twenty-Second Annual IEEE Applied Power Electronics Conference and Exposition, pp. 1319–1325, 2007, doi:10.1109/APEX.2007.357686.

J.-M. Wang, C.-W. Lin, K.-Y. Huang, J.-S. Wong, “The Novel Quasi- Resonant Flyback Converter With Autoregulated Structure for Parallel/Serial Input”, IEEE Transactions on Industrial Electronics, vol. 67, no. 2, pp. 992–1004, 2020, doi:10.1109/TIE.2019.2902827.

S. Dutta, D. Maiti, A. K. Sil, S. K. Biswas, “A Soft-Switched Flyback converter with recovery of stored energy in leakage inductance”, in 2012 IEEE 5th India International Conference on Power Electronics (IICPE), pp. 1–5, 2012, doi:10.1109/IICPE.2012.6450415.

J.-W. Kim, I.-O. Lee, G.-W. Moon, K.-B. Park, “Series input parallel output interleaved flyback converter with regenerative leakage inductance energy”, in Proceedings of The 7th International Power Electronics and Motion Control Conference, vol. 2, pp. 1347–1352, 2012, doi:10.1109/IPEMC.2012.6258993.

Z. Ouyang, J. Zhang, W. G. Hurley, “Calculation of Leakage Inductance for High-Frequency Transformers”, IEEE Transactions on Power Electronics, vol. 30, no. 10, pp. 5769–5775, 2015, doi:10.1109/TPEL.2014.2382175.

R. Prieto, J. Cobos, O. Garcia, P. Alou, J. Uceda, “High frequency resistance in flyback type transformers”, in APEC 2000. Fifteenth Annual IEEE Applied Power Electronics Conference and Exposition (Cat. No.00CH37058), vol. 2, pp. 714–719 vol.2, 2000, doi:10.1109/APEC.2000.822583.

T. Strous, G. Simonelli, “Improved Power Transformer Performance using Leakage Inductance Shielding”, in 2019 European Space Power Conference (ESPC), pp. 1–6, 2019, doi:10.1109/ESPC.2019.8932074.

Y.-K. Lo, J.-Y. Lin, “Active-Clamping ZVS Flyback Converter Employing Two Transformers”, IEEE Transactions on Power Electronics, vol. 22, no. 6, pp. 2416–2423, 2007, doi:10.1109/TPEL.2007.909285.

C.-S. Liao, K. M. Smedley, “Design of high efficiency Flyback converter with energy regenerative snubber”, in 2008 Twenty-Third Annual IEEE Applied Power Electronics Conference and Exposition, pp. 796–800, 2008, doi:10.1109/APEC.2008.4522812.

R. K. Kokkonda, R. Beddingfield, S. Bhattacharya, B. Carsten, B. Varga, “A Novel Transformer Leakage Energy Recovery Active Clamp Control Technique for High Power AC/DC Flyback Converters”, in 2023 IEEE Applied Power Electronics Conference and Exposition (APEC), pp. 1238–1245, 2023, doi:10.1109/APEC43580.2023.10131320.

G. N. Wooding, A. S. De Beer, “The effect of leakage inductance and snubbing on electromagnetic interference generated by a flyback converter”, in IEEE Africon ’11, pp. 1–5, 2011, doi:10.1109/AFRCON.2011.6072057.

C. Larouci, J.-P. Keradec, J.-P. Ferrieux, L. Gerbaud, J. Roudet, “Copper losses of flyback transformer: search for analytical expressions”, IEEE Transactions on Magnetics, vol. 39, no. 3, pp. 1745–1748, 2003, doi:10.1109/TMAG.2003.810411.

F. A. Holguin, R. Prieto, R. Asensi, J. A. Cobos, “Power losses calculations in windings of gapped magnetic components: The i2D method applied to flyback transformers”, in 2015 IEEE Energy Conversion Congress and Exposition (ECCE), pp. 5675–5681, 2015, doi:10.1109/ECCE.2015.7310457.

N. Y. Veretennikov, Y. V. Skitsky, “Loss Optimization Approach in Flyback Transformer Windings”, in 2024 IEEE 25th International Conference of Young Professionals in Electron Devices and Materials (EDM), pp. 1290–1293, 2024, doi:10.1109/EDM61683.2024.10615169.

W. Yuan, X. Huang, P. Meng, G. Zhang, J. Zhang, “An improved winding loss analytical model of Flyback transformer”, in 2010 Twenty- Fifth Annual IEEE Applied Power Electronics Conference and Exposition (APEC), pp. 433–438, 2010, doi:10.1109/APEC.2010.5433633.

T. Halder, “Improved coupled inductor loss optimization of the Flyback SMPS”, in 2013 International Conference on Power, Energy and Control (ICPEC), pp. 798–802, 2013, doi:10.1109/ICPEC.2013.6527764.

H. Onay, V. Süel, T. Özgen, A. Hava, “Comparative Power Loss Analysis of DCM Flyback Transformer Based on FEA, Numeric Simulation, Calculation and Measurements”, in 2019 21st European Conference on Power Electronics and Applications (EPE ’19 ECCE Europe), pp. P.1–P.10, 2019, doi:10.23919/EPE.2019.8915387.

C. Sullivan, T. Abdallah, T. Fujiwara, “Optimization of a flyback transformer winding considering two-dimensional field effects, cost and loss”, in APEC 2001. Sixteenth Annual IEEE Applied Power Electronics Conference and Exposition (Cat. No.01CH37181), vol. 1, pp. 116–122 vol.1, 2001, doi:10.1109/APEC.2001.911636.

Y. Panov, M. Jovanovic, “Adaptive off-time control for variable-frequency, soft-switched flyback converter at light loads”, IEEE Transactions on Power Electronics, vol. 17, no. 4, pp. 596–603, 2002, doi:10.1109/TPEL.2002.800958.

R. D. Stracquadaini, “Mixed Mode control (Fixed off Time Quasi Resonant) for flyback converter”, in IECON 2010 - 36th Annual Conference on IEEE Industrial Electronics Society, pp. 556–561, 2010, doi:10.1109/IECON.2010.5675222.

V. Vorperian, “Quasi-square-wave converters: topologies and analysis”, IEEE Transactions on Power Electronics, vol. 3, no. 2, pp. 183–191, 1988, doi:10.1109/63.4348.

J.-S. Yoo, J.-O. Baek, T.-Y. Ahn, “A High-Efficiency QR Flyback DC–DC Converter with Reduced Switch Voltage Stress Realized by Applying a Self-Driven Active Snubber (SDAS)”, Energies, vol. 16, no. 3, 2023, doi:10.3390/en16031068.

S. L. Jeng, M. T. Peng, C. Y. Hsu, W. H. Chieng, J. P. Shu, “Quasi-Resonant Flyback DC/DC Converter Using GaN Power Transistors”, World Electric Vehicle Journal, vol. 5, no. 2, pp. 567–573, 2012, doi:10.3390/wevj5020567.

T. Instruments, “Inductor and Flyback Transformer Design”, Texas Instruments, pp. 1–19, 2001.

H. Zenkner, “Coupled Inductors and their Applications”, in 2019 International Symposium on Electromagnetic Compatibility - EMC EUROPE, pp. 963–967, 2019, doi:10.1109/EMCEurope.2019.8871541.

T.-J. Liang, K.-H. Chen, J.-F. Chen, “Primary Side Control For Flyback Converter Operating in DCM and CCM”, IEEE Transactions on Power Electronics, vol. 33, no. 4, pp. 3604–3612, 2018, doi:10.1109/TPEL.2017.2709811.

D. Carey, “Isolated Switch-Mode Power Supplies: How to Choose a Forward vs. a Flyback Converter”, Analog Devices Techinical Articles, pp. 1–6, 2024.

B. Keogh, I. Cohen, “Flyback transformer design considerations for efficiency and EMI”, Texas Instruments, pp. 1–37, 2016.

K. Hashimoto, T. Okuda, T. Hikihara, “A Flyback Converter with SiC Power MOSFET Operating at 10 MHz: Reducing Leakage Inductance for Improvement of Switching Behaviors”, in 2018 International Power Electronics Conference (IPEC-Niigata 2018 -ECCE Asia), pp. 3757–3761, 2018, doi:10.23919/IPEC.2018.8507361.

B. Carsten, “High Frequency Conductor Losses in Switchmode Magnetics”, pp. 1–91, 1986.

P. L. Dowell, “Effects of eddy currents in transformer windings”, in Proceedings of the IEE, 1966, doi:10.1049/piee.1966.0236.

L. H. Dixon, “Deriving the Equivalent Electrical Circuit from the Magnetic Device Physical Properties”, Texas Instruments, pp. 1–7, 1994.

A. Ducluzaux, “Extra losses caused in high current conductors by skin and proximity effects.”, Cahier Technique no 83 Schneider Electric, pp. 1–22, 1983.

R. Ridley, “Flyback Snubber Design”, Switching Power Magazine, vol. 12, pp. 1–7, 2005.

International Electrotechnical Commission, “CISPR 15:2013 – Limits and methods of measurement of radio disturbance characteristics of electrical lighting and similar equipment”, IEC Standard, 2013.

J. Amado, Técnicas de Redução da Indutância de Dispersão em Indutores Acoplados e seu Impacto no Funcionamento de um Driver de LED Flyback Quase Ressonante, Master’s thesis, Universidade Federal de Santa Maria (UFSM), Santa Maria, RS, Brasil, 2025, available at: https://repositorio.ufsm.br/handle/1/34646.