In order to comply with the stringent electromagnetic interference (EMI) requirements for automotive electronics applications, this paper presents a new SEPIC topology and operation that significantly reduces di/dt switching dynamics at the converter input for conducted EMI suppression. The proposed converter employs a unique T-passive network, consisting of a coupled inductor and an auxiliary LC branch to self-cancel ΔI_IN and thus minimize associated di/dt without significant power density and efficiency penalty. Meanwhile, it does not require active control circuits to achieve accurate ΔIIN cancellation, simplifying the design complexity. Operating at 400kHz, an experimental prototype of such a converter regulates a nominal output at 12V with a 42W power range and a peak power efficiency of 86.8%, accommodating a wide input voltage ranging from 4.5V to 40V. The experimental results verify a peak EMI reduction of 20.4 dB and 13.9dB for the 24V/12V and the 40V/12V power conversion, respectively.
