Current-mode control, five different types, used with the three basic classes of power converters: Small-signal AC and large-signal DC characterization, stability requirements, and implementation of practical circuits

Current-mode control effectively eliminates the phase lag of the control function, associated with the output filter inductor or the energy-storage inductor. The several types of current-mode controllers differ slightly in their phase-lag characteristics, but they are all far superior to the commonly used PWM duty-ratio controllers. Unfortunately, industry has been slow to appreciate and exploit the considerable advantages of current-mode control. There seem to be two reasons for that: (a) the unavailability of integrated circuits which are well-suited to implementing current-mode controllers and (b) the lack of detailed, systematically organized, theoretical and practical information on current-mode controllers. The objective of this paper is to fill this gap by providing a well-organized compendium of useful information for the design engineer who wants to understand the operation of a current-mode-controlled power converter and to accomplish an optimal design. Five different control methods are considered, used with the three basic types of regulated rectangular-wave power converters.