Among the different topologies, buck (step-down) regulators are the most widely used, as they efficiently convert higher DC bus voltages (e.g., 12 V, 24 V, or 48 V) to the lower levels required by processors, sensors, and communication interfaces. Other topologies, such as boost, buck-boost, flyback, and SEPIC, extend this capability, offering step-up, inverting, or flexible input-output conversion ratios to meet application-specific requirements. However, the fast switching transitions inherent to these regulators introduce electromagnetic interference (EMI) and noise. Both conducted emissions (propagating through supply lines) and radiated emissions (coupling through space) can degrade system performance and jeopardize compliance with international standards such as CISPR 32 / IEC 55032. As a result, careful consideration of converter topology, passive component selection, PCB layout, and filter design is essential to balance efficiency, dynamic response, and EMC behavior.
In particular, the choice of capacitor technology, storage inductors, switching frequency, and semiconductors directly affects both efficiency and EMC. For regulators handling relatively high input and output currents, achieving a compact, reliable, and cost-effective solution requires striking a compromise between efficiency, size, damping, and filter performance. Additional input and output filtering is often required to meet emission limits, but these filters themselves can introduce losses or instability if not carefully designed.
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