On the Advantages of Δ-Σ Modulation in Current Ripple Driven Design of Filter Inductors for Dynamic Power Converters

Abstract:
This paper compares δ-σ modulation (DSM) to fixed-frequency pulse-width modulation (PWM) in dynamic power converters. Filter inductors usually account for a significant proportion of the volume in such converters, although modern fast-switching semiconductors enable high switching frequencies. We show that DSM permits higher instantaneous switching frequencies than PWM for a given switching loss budget. The current ripple under DSM maintains a constant amplitude. This allows for a reduction in converter filter inductance value and potentially inductor volume or losses. Our findings were validated through simulation and measurement, showing that DSM exhibits the same maximum current ripple amplitude and switching losses for a 50% smaller inductor than an equivalent PWM-driven setup. A data-based inductor loss analysis confirms that the savings in DC inductor losses enabled by DSM outweigh the additional AC losses.