This paper presents a hybrid buck-boost DC-DC converter structure to address the limitations of single-output and low conversion ratios (CR) in traditional energy harvesting systems. To reduce the CR of the inductive boost and enhance the total CR of the converter while improving efficiency, the proposed converter cascades a boost circuit with a reconfigurable switched capacitor (SC), and also includes a supercapacitor. The advantage of this architecture is the ability to use low-voltage low-threshold transistors with lower parasitic capacitance and on-resistance, which achieve high-voltage output while reducing switching and conduction losses. The supercapacitor can store energy under a light load and provide additional energy replenishment in buck mode under heavy load. The reconfigurable SC circuit can enable a 2V or 3V output by configuring the switch array. Adaptive switching frequency control was used to achieve a balance between load capability and switching loss. The proposed DC-DC converter is designed with a 0.18 µm CMOS process and has maximum conversion efficiencies of 91.83%, 89.42%, and 88.09% for the inductive boost stage, 2V SC output stage, and 3V SC output stage, respectively. The output voltage ripple is less than 20 mV at 1V output and less than 30 mV at 2V output and 3V output. The input voltage of the converter is as low as 20 mV. The converter features multi-output, high-conversion-ratio, and enhanced efficiency, which are suitable for energy-harvesting applications.