A Bias-Flip Interface and Dual-Input DC-DC Converter for Piezoelectric and RF Energy Harvesting

Energy harvesting converts nonelectrical energy into electrical energy to power low-power integrated circuits for the Internet of Things and wearable devices. This paper presents an energy harvesting power management integrated circuit implemented in 180 nm SOI CMOS. The proposed system improves piezoelectric energy harvesting power extraction by using an improved bias-flip interface and increases power output by simultaneously scavenging multiple energy sources using a dual-input buck-boost converter. The implemented bias-flip interface, when using a 2.2 mH inductor and 6 switched capacitors, offers a bias-flip efficiency up to 95.1%. At 113.4 Hz vibration excitation of 0.6 g, the proposed interface provides a 7.62x, 2.47x, and 1.22x power extraction improvement when compared to an ideal full-bridge rectifier, and synchronized switch harvesting on inductor (SSHI) and on capacitor (SSHC) circuits, respectively. Furthermore, the bias-flip inductor is shared with the integrated dual-input DC-DC converter simultaneously scavenging high-voltage piezoelectric and low-voltage RF energy to increase output power and improve environmental adaptability of the system.