Analysis and modeling of peak-current-mode-controlled buck converter in DICM

This paper presents a unified method to obtain both small- and large-signal models for a peak-current-mode-controlled buck converter which accurately predict its behavior. The models show that the peak-current-mode transfer functions are effectively of first order, as can be expected due to the heavy bounding of inductor current. The large-signal behavior can be accurately predicted by using a simple algebraic equation including the mode limit of basic-switching-frequency operation as well as the input-output relations. It is also pointed out that a buck converter can have stable open-loop as well as closed-loop operation modes at basic switching frequency and at its even and odd harmonics. The subharmonic modes are, however, not controllable in a conventional way.