A ΔIIN Self-Canceled SEPIC Power Converter for EMI CISPR 25 Compliance

In an effort to comply with stringent electromagnetic interference (EMI) standards for automotive electronics applications, this paper introduces a new SEPIC converter topology with significantly reduced di/dt switching dynamics for conducted EMI suppression. The converter employs a unique T circuit network, consisting of a coupled inductor and an auxiliary LC branch, to self-cancel its input current ripple ΔI <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">IN</inf> , thus minimizing associated di/dt. By doing so, the converter incurs no significant power density and efficiency penalties. Meanwhile, the converter requires no active control circuitry to ensure accurate ΔI <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">IN</inf> cancelation, simplifying the design complexity. To demonstrate the converter topology and design ideas, a converter prototype is designed, which accommodates a wide input supply voltage range of 4.5V to 40V and delivers an output of 12V, with seamless buck-boost conversion operation. Operating at 400kHz, it delivers a maximum power of 42W and achieves a peak efficiency of 86.8%. For the step-up conversion with 5V V <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">IN</inf> and 500mA load, the ΔI <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">IN</inf> self-canceled SEPIC topology achieves 9.6dB peak EMI reduction at the fundamental frequency. For the step-down conversion with 1.5A load, it reduces the peak EMI by 20.4dB and 13.9dB at V <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">IN</inf> of 24V and 40V, respectively, satisfying the CISPR25 Class 2 Standards.