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Designing for Efficiency 9 www.cadence.com As frequency increases, usable conductor cross-section decreases, raising resistance and heating. To mitigate this effect, designers use litz wire or parallel conductors arranged to equalize current distribution. Proper winding geometry reduces proximity effects and improves thermal performance. This becomes more important when SiC devices enable higher switching frequency, since magnetic losses can otherwise dominate total converter efficiency. 7.4 Leakage Inductance and Switching Stress Leakage inductance represents magnetic energy that is not coupled between primary and secondary windings. The stored energy is: During switching transitions, this energy appears as voltage overshoot and ringing. Faster SiC switching edges make converters more sensitive to leakage inductance. Reducing leakage requires tight magnetic coupling and careful winding layout. However, tighter coupling often increases interwinding capacitance, which can worsen EMI. Transformer design therefore involves balancing electrical stress against electromagnetic performance. 7.5 EMI and Interwinding Capacitance Capacitive coupling between windings creates common-mode current: SiC devices produce higher dv/dt, which increases this current and raises EMI risk. Shielding techniques and controlled winding spacing reduce capacitive coupling. Designers must balance EMI performance against efficiency and thermal constraints. 7.6 Thermal Considerations Total magnetic heating combines core and copper losses: Transformer temperature rise must remain within insulation limits to ensure reliability. Adequate core sizing, airflow, and thermal paths are essential. When semiconductor losses decrease, transformer heating becomes a larger fraction of total system temperature rise. Efficient magnetic design is therefore critical to realizing the full benefit of SiC devices. 7.7 Interaction Between Magnetics and Wide Bandgap Switching Wide bandgap devices shift the loss balance of the converter. Faster transitions and higher switching frequency place greater demands on transformer design. Poor magnetic optimization can erase semiconductor efficiency gains through increased core loss, copper heating, and EMI mitigation overhead. Conversely, a well-designed transformer allows the converter to fully exploit the advantages of SiC switching. Simulation-driven magnetic modeling enables engineers to explore these tradeoffs before hardware construction, reducing design iteration risk.