A 0.24mm2 Bridge-less Hybrid SSHI Interface Circuit for Piezoelectric Energy Harvesting with a Wide Load Range and Up to 1620% Power-Extraction Improvement

Abstract

Piezoelectric energy harvesting (PEH) which extracts ambient energy with piezoelectric transducers (PT) is a promising power solution for internet-of-things (loT) devices. As shown in Fig. 1, the interface circuit is a key part of a PEH system. Many interface circuits based on capacitive and inductive bias-flip rectifiers are proposed for maximum energy extraction from PT compared to full bridge rectifiers (FBRs) [1] –[3]. Among them, synchronized switch on inductor [1]–[2] or capacitor [3] (SSHI or SSHC) techniques are effective ways to obtain higher output power in certain load ranges (LRs). Multiple-step SSHI [4] –[6] or SSHC [3] techniques can help significantly decrease the energy loss during the bias flip. However, the output power of SSHI and SSHC drops quickly as the load deviates away from the maximum power point (MPP). Synchronous electric charge extraction (SECE) technique is a solution to keep MPP during the full LRs [7]. Nevertheless, SECE is limited to the maximum extraction level which is lower than SSHI and SSHC in most conditions. So, extracting energy with high efficiency in a wide LR is a challenge for most interface circuits in PEH.