Discrete-time modeling of multi-state DC-DC converters

The discrete-time models obtained from state-space average models are accurate only in the low frequency region and are not suitable for predicting the high frequency behavior. This limitation becomes more severe particularly in the multi-state dc-dc converters. To improve the accuracy the discrete-time models applicable for multi-state dc-dc converters are developed in this paper. To enhance the closed-loop converter system stability limits the digitally controlled multi-state dc-dc converters are driven with either leading-edge or trailing-edge pulse-width modulated gating signals with ON/OFF-time sampling. The proposed discrete-time modeling methodology is also takes the effect of modulation type and sampling instant. In order to demonstrate the usefulness and validity of the developed models a two-input multi-state boost dc-dc converter is taken as an example in this paper. The discrete-time models accuracy is compared with the results generated from PSIM simulator. Taking these discrete-time models digital voltage/current-mode controllers are designed and then verified both in simulation and experiment. The simulation and experimental results are close agreement with each other.