Mechanism Model and Prediction Method of Common Mode Radiation for a Nonisolated Very-High-Frequency DC-DC Converter with Cables

Research on electromagnetic interference of high-frequency power converters remains a challenging and important topic, particularly in light of rapidly emerging wide band-gap power devices operating with ns level turn-on/turn-off times. Building on the substantial contributions that have been made on the formation mechanisms of common mode (CM) radiation, a new mechanism for an equivalent CM driving voltage source caused by imbalanced conductors or components is proposed. Applying this mechanism, the CM driving voltage source model of a nonisolated boost dc/dc power converter with input/output cables is introduced. The CM far-field electric strength algorithms of an asymmetric cable antenna are theoretically analyzed and derived in detail. Subsequently, a prototype for a low-power 30-MHz very-high-frequency boost power converter based on gallium nitride is built and its 10-m CM far-field radiation strength is predicted according to the proposed model. The radiation pattern characteristics are analyzed and several radiation suppression methods are also designed. The comparison with the measured radiation results shows that the proposed CM radiation model and the prediction method achieve good effect below 300 MHz.