Averaged Switch Modeling of Boundary Conduction Mode Dc-to-Dc Converters

Averaged switch approach is extended to the modeling of boundary conduction mode (BCM) dc-to-dc converters that operate at the boundary between continuous conduction mode (CCM) and discontinuous conduction mode (DCM). BCM dc-to-dc converters have smaller inductor size and reduced switching losses compared to CCM, and lower peak current compared to DCM. The large-signal BCM averaged switch model shows that several BCM converters with input voltage feedforward exhibit resistive or nearly resistive input characteristic, which is well suited for realization of power factor correctors. It is shown that BCM converters exhibit simpler dynamics compared to CCM current programmed control (CPM). Small-signal frequency responses predicted by the averaged switch model are verified by simulation and experiments.