A Tri-Mode Reconfigurable DC-DC Converter With Photovoltaic Energy Harvesting for Miniature IoT Batteries

This brief proposes a reconfigurable DC-DC converter for an energy-harvesting system with a tri-mode recharging method for miniature Internet of Things (IoT) batteries operating at various temperatures. The proposed system and IoT battery operate at temperatures as low as – $5~^{\circ }$ C with an internal resistance $(R_{INT})$ of up to 1.9 k $\Omega $ . The proposed recharging method utilizes a low-dropout regulator and DC-DC converter with a negative inductor current to rapidly recharge a storage capacitor $(C_{STOR})$ and isolate the IoT battery from the $C_{STOR}$ . With a 180 nm CMOS process, the charge of the $C_{STOR}$ can be restored rapidly with the aid of the IoT battery, which reduces the ratio of the activation time $(t_{\mathrm {ACT}})$ to the recharging time $(t_{\mathrm {RCHG}})$ to 0.27 at – $5~^{\circ }$ C.