An LC-RC Filter for Multi-Phase Interleaved Buck Converter to Generate High Stability Magnetic Field

Nuclear magnetic resonance (NMR) and specific heat measurements demand a high-stability flat-top pulsed magnetic field (FTPMF). The multi-phase Interleaved Buck Converter (IBC), with its high power density and swift transient response, emerges as a promising solution for a compact FTPMF system. Yet, the PWM usage in IBC introduces output current ripple, limiting FTPMF's stability. This research introduces an LC-RC filter for ripple cancellation in IBC under magnetic loads. The proposed filter ensures cost-effective ripple cancellation in IBC with fewer passive components and reduces load oscillation risks. We present a frequency-domain model for IBC with an LC-RC filter, analyze its transient response, and deploy an optimization algorithm for LC-RC parameters selection. We take the variation of the passive components into account and propose a frequency correction method to further reduce the ripple. Simulations and experiments highlight the benefits of the filter as well as the feasibility of the frequency correction scheme.