Two-Part Controller Design for Switched-Capacitor Based Buck–Boost Converter

Many of the buck–boost topologies have lower duty ratio range per unit voltage gain (DMR). In this article, controller design aspects, multi-mode operation of a switched-capacitor bridge based buck–boost converter (SCBDBBC) exhibiting better DMR is investigated. Presence of switched-capacitor bridge enhances the duty ratio range for bucking operation while the existence of two switches offers degree of freedom to realize multi-mode operations. These are: 1) buck–boost; 2) standalone boost; and 3) standalone buck operation. By exercising the degree of freedom associated with two switches, under the buck–boost operation three different multi-mode operations are feasible which are: 1) equal duty ratios with synchronized gate signals (DS1=DS2); 2) unequal duty ratios with synchronized gate signals (case-1:DS1>DS2); and 3) unequal duty ratios with synchronized gate signals (case-2:DS1DS2). Mathematical analysis is established for both the cases (case-1 and case-2). From voltage gain point of view both of these schemes result in identical gain, but theDS1DS2operation results in low source current ripple compared to equal duty ratio operation. Hence, detailed investigations are given for SCBDBBC under case-2 control. Since there are two controlling inputs (DS1,DS2) and one controlled output (vo), two controllers are designed using two-input single-output (TISO) control theory. To demonstrate the SCBDBBC operation and TISO based two-part controller design, a 48 to 24 V (in bucking)/ 60 V (in boosting) with power rating 24 ∼ 60 W is chosen for experiments. The SCBDBBC multi-mode operation in standalone buck and boost operations are demonstrated in addition to buck–boost conversion. The analytical findings are in close agreement with experimental observations.