Dynamic modeling of a hysteretic modulator

Hysteretic modulators have superior dynamic performance and they help in reducing the number of output capacitors without sacrificing the transient response. This paper discusses the dynamic modeling of hysteretic modulators with variable switching frequency. Small-signal characteristics of the modulator are derived. An easy-to-use, numerically-efficient model is developed to accurately predict the small- and large-signal behavior of the converter with hysteretic modulator. The model is able to predict the small-signal behavior up to half the switching frequency with sufficient accuracy. It also predicts the same large-signal responses as the real-time simulation, but at two orders of magnitude less in computation time. Laboratory tests on a 1.8-V/20-A single-phase prototype shows good correlation between experimental results and theoretical predictions both in frequency and time domain.