Bidirectional Single-Inductor Dual-Supply Converter With Automatic State-Transition for IoT Applications

A single-inductor dual-supply dc-dc converter with bidirectional energy flow is proposed for the Internet-of-Things applications. This paper combines two dc-dc converters into one by sharing a single inductor, and it is capable of storing energy and powering output load by using the bidirectional inductor current. Besides, the voltage of the energy storage element is continuously monitored in the proposed converter, which eliminates the possibility of overcharging. Furthermore, the variations on the output voltage are typically negligible when the input voltage changes. In addition, a novel two-step startup procedure that does not require any on-chip/off-chip startup auxiliary circuit is proposed, which can significantly reduce the chip area. The proposed converter is fabricated by a 0.18-μm CMOS mixed-signal process. The voltage range of the storing element is 1.2-1.4 V, and the maximal output power of the proposed converter is 18 mW with its output voltage setting at 1.8 V.