A Digitally Controlled Switching Regulator With Reduced Conductive EMI Spectra

This paper presents the use of a combined random pulse position modulation (RPPM)/digital pulsewidth modulation (DPWM) digital controller for a buck converter to simultaneously achieve low-conductive electromagnetic interference (EMI) and a fast transient response. An area-efficient RPPM/DPWM controller suitable for advanced system-on-chip integration is proposed and implemented in a field-programmable gate array-based prototype to verify its EMI-suppression capability. The experimental results for a 1.2-V digital buck converter show that the proposed digital switching regulator can switch between RPPM and DPWM modes smoothly and automatically. Closed-loop system measurements demonstrate that, compared to DPWM, up to 17.27 and 14.99 dB power spectra reductions are obtained in the input current and switching node, respectively.