A Flying-Capacitor-Assisted Single-Mode Buck-Boost Converter for Battery-Powered Applications

A single-mode buck-boost converter that generates a 3.3-V power supply from a variable input voltage ( ${V} _{\mathbf {IN}}$ ) range of 2.7–4.2 V for mobile li-ion battery applications is presented. The proposed buck-boost converter employs a switched-capacitor-based buck-converter operation, in which the voltage switching operation is followed by an LC filter. This ensures continuous output current delivery and reduces conduction loss in the inductor. An efficient power-stage structure and its operation are introduced, wherein only one resistive component is connected in series with the inductor during all operation phases. The proposed buck-boost converter has been implemented in a 180-nm BCDMOS process and regulates an output voltage of 3.3 V from a ${V} _{\mathbf {IN}}$ range of 2.7–4.2 V by single-mode step-up/down operation. The peak efficiency of 93.4% is achieved at 2.7-V ${V} _{\mathbf {IN}}$ , and the peak efficiency above 90% is obtained over the entire ${V} _{\mathbf {IN}}$ range.