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
IN
, 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
IN
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
IN
and 500mA load, the ΔI
IN
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
IN
of 24V and 40V, respectively, satisfying the CISPR25 Class 2 Standards.