TITLE:
Exact Dynamic Modeling of PWM DC-to-DC Power Converters—Part I: Continuous Conduction Mode
AUTHORS:
Justin Simmons, Richard Tymerski
KEYWORDS:
Describing Function, DC-to-DC Switching Power Converter, Small-Signal Modeling, Frequency Response
JOURNAL NAME:
Journal of Power and Energy Engineering,
Vol.9 No.5,
May
22,
2021
ABSTRACT: A general approach is presented by which the exact frequency response of
any transfer function of switched linear networks can be determined. This is
achieved with a describing function approach using a state space equation
formulation. This work presents a somewhat simplified set of equations to one previously given by one of the authors. To
demonstrate application of the general formulation, the frequency responses of
switched networks used as PWM DC-to-DC converters operating in
continuous conduction mode (CCM) under voltage mode control are derived. (The
accompanying paper, Part II, will present results for converters operating in
discontinuous conduction mode (DCM)). From the general sets of equations
developed here, both the control to output and input source variation to output
frequency responses are derived. The describing function approach enables exact
frequency response determination, even at high frequencies where the accuracy
using average models may be compromised. Confirmation of the accuracy of the
derived models is provided by comparing the responses with those obtained using
the commercial simulator PSIM on a PWM boost converter. The magnitude and phase
responses are shown to match perfectly over the full range of frequencies up to
close to half the switching frequency. Matlab code that implements the models
is given such that the user can easily adapt for use with other PWM converter
topologies.