OPEN-LOOP AND CLOSED-LOOP DC AND SMALL-SIGNAL CHARACTERISTICS OF PWM BUCK-BOOST CONVERTER FOR CCM

DC and small-signal circuit models of the PWM buck-boost converter for the continuous conduction mode (CCM) are derived. The models take int o account parasitic components, such as the equivalent series resistan ce (ESR) of the filter capacitor, the ESR of the inductor, the transis tor on-resistance, and the diode forward resistance and offset voltage . The component values and the parasitics were measured for a prototyp e converter. The de voltage transfer function and the efficiency of th e converter are derived from the de model. Small-signal open-loop tran sfer functions are derived from the small-signal model. The derivation of the transfer function for an integral-lead controller with the loa ding effect of the voltage divider network in the feedback loop is giv en. Small-signal closed-loop transfer functions are derived. Bode plot s are given for various transfer functions of the converter.