EMI Noise Reduction in GaN-based Full-bridge LLC Converter

In medium-to-high power converters, full-bridge LLC converter has been a common choice due to its high efficiency and power density. However, today, the EMI noise remains a significant obstacle due to high dv/dt and large parasitic capacitors in transformers and MOSFETs. Through eliminating displacement currents, the presented technique can help to maintain low-profile converter by avoiding the bulky CM chokes, so as to further increase power density. This paper analyses main sources of EMI noise in FB LLC converter and presents a cancellation technique to eliminate EMI noise without other passive components. A lumped simulation circuit Shows that the optimized converter generated above 50dB less EMI noise than a traditional converter.