Unified three-terminal switch model for current mode controls

Current mode controls including constant frequency peak-current mode control, valley-current mode control, charge control as well as variable frequency constant on-time control and constant off-time control, have been widely used in many power converter topologies. However, no unified model is available to provide an accurate and simple equivalent circuit for these control schemes. This paper presents a unified three-terminal switch model for current mode controls. By identifying the invariant three-terminal structure in current mode control PWM converters, which consists of active switch, passive switch, inductor and closed current loop, the terminal current and voltage relationships are studied and represented by an equivalent circuit. A small signal model for a current mode control PWM converter, which is good beyond half of switching frequency for forementioned control schemes, can be obtained by a simple cyclic permutation and substitution of the PWM switch with its equivalent circuit.