Consideration forAbnormal Phenomenon in Common-Source typeActive-clamped Forward Converter withSelf-drivenSynchronous Rectifier

Many switching converters use soft-switching techniques withan active-clamp snubberso as toreduce switching surgeandcommon-modenoise. Inparticular, the common-source typeactive-clamped forwardconverter is knownasaneffective circuit topology forcommon-modenoise reduction. On theotherhand,replacing theoutputrectifying diodes withsynchronous rectifier circuits, thepowerefficiency canbeimproved intheDC-DCconverter withlow-voltage and large-current output. Furthermore, theself-driven synchronous- rectifier circuits aregenerally usedbecause ofisolation and simple structure oftheir gate-driving circuits. However,forthiscommon-source typeactive-clamped forward converter withself-driven synchronous rectifiers, ithas beenrecently noticed thatanabnormal phenomenon suchasthe inductor-current oscillation andtheacoustic noise generation in thetransformer occurinsomeconditions. Thispaperdiscusses theabove-mentioned abnormal phenomenon.The causeoftheabnormalphenomenon is examined andits occurrence condition isclarified.