A Dual-Mode Hybrid Step-Up Converter with Stable Output for Vibration Energy Harvesting

A dual-mode hybrid step-up circuit for electromagnetic energy harvesting (EVEH) is proposed in this paper, with the merits of continuous output power delivery with and without external vibrations, simple architecture, and no need for extra circuits to start up. The proposed hybrid converter combines a multi-stage voltage multiplier (VM) with a boost regulator, which utilizes the winding inductance of the electromagnetic energy harvester as a boost inductor. With external vibration, the proposed circuit powers the load and stores energy in the super-capacitor through VM mode. When external vibration disappears, it automatically switches to boost mode and powers the load using the energy stored in the supercapacitor. For hybrid mode operation, the number of VM stages is optimized considering the following three aspects: sufficient voltage gains when vibration is on, time durations to provide constant power when vibration is off for as long as possible, and low losses at VM stage. A GaN-based dual-mode hybrid converter is built to verify the output regulation capability with an in-house-designed electromagnetic energy harvester. The outputs of the hybrid circuit achieve 4.05 V and 1.64 mW at a 100-Hz external vibration frequency and an acceleration of 0.7 g. The peak efficiency of the proposed hybrid converter reaches 60.7%. When external vibration disappears, the circuit is able to maintain a stable output for 13 s with a super-capacitor of 0.1 F.