Small-signal Laplace-domain analysis of uniformly-sampled pulse-width modulators

As the performance of digital signal processors has increased rapidly during the last decade, there is a growing interest to replace the analog controllers in low power switching converters by more complicated and flexible digital control algorithms. Compared to high power converters, the control loop bandwidths for converters in the lower power range are generally much higher. Because of this, the dynamic properties of the uniformly-sampled pulse-width modulators used in low power applications become an important restriction for the maximum achievable bandwidth of control loops. After the discussion of the most commonly used uniformly-sampled pulse-width modulators, small-signal frequency- and Laplace-domain models for the different types of uniformly-sampled pulse-width modulators are derived theoretically. The results obtained are verified by means of experimental data retrieved from a test setup.