Universal Controllers for PWM Converters: a Normalized Approach

Linear controllers based on small-signal models are widely used in Pulse-Width-Modulated (PWM) converters due to their simple implementation. Several compensator tuning methods for the three fundamentals DC-DC PWM converters have been developed to achieve desired closed-loop performance. However, most of the existing procedures develop compensator coefficients that depend on the actual parameters of the converter, requiring recalculation of the coefficients for different parameter combinations. This paper introduces a powerful and straightforward normalized control design tool for PWM converters. The proposed normalization technique leads to converter's models and compensator coefficients that are independent on the filter parameters, as well as the voltage and power ratings. The design of linear controllers in the normalized domain enables the direct application of the same controller to any combination of converter's parameters. A unified normalized model for the three fundamental PWM topologies is derived. A normalized controller design example for a voltage mode synchronous buck converter is shown. Simulation and experimental results for two different buck converters are presented to validate the normalization concept and highlight the strong contribution to the field made by this approach, which results in a significant asset for practicing engineers.