Abstract:

When analyzing DC-DC converters, the PWM comparator should be taken into account firstly because it is one of the most importantnonlinear parts. In traditional, PWM comparators are considered as a linear amplifier, which is simple but questionable when approaching half of the switching frequency. The describing function method can obtain accurate model for PWM comparator, however, it takes a large amount of calculations and lacks of physical insight. To make the modeling accurate to describe the PWM comparator and avoid the complexity of describing function method, this paper proposes a sampling-based model and gives its matrix description. The PWM is calculated by an impulse-train sampling equivalent method to reduce the computation and a linear space concept is established to simplify the nonlinear PWM comparator as a linear model described by vectors and matrix. The proposed model has some advantages such as high accuracy, simple formula and definite physical meaning, the simulation and experimental results validate its accuracy and effectiveness.

Key words: Distributed power system, DC-DC converters, PWM comparator, sampling, matrix