The development of new technologies has led to an explosion of data, while the computation ability of traditional computers is approaching its upper limit. The dominant system architecture is the von Neumann architecture, with the processing and storage units working independently. The data migrate between them via buses, reducing computing speed and increasing energy loss. Research is underway to increase computing power, such as developing new chips and adopting new system architectures. Computing-in-memory (CIM) technology allows data to be computed directly on the memory, changing the current computation-centric architecture and designing a new storage-centric architecture. Resistive random access memory (RRAM) is one of the advanced memories which has appeared in recent years. RRAM can change its resistance with electrical signals at both ends, and the state will be preserved after power-down. It has potential in logic computing, neural networks, brain-like computing, and fused technology of sense-storage-computing. These advanced technologies promise to break the performance bottleneck of traditional architectures and dramatically increase computing power. This paper introduces the basic concepts of computing-in-memory technology and the principle and applications of RRAM and finally gives a conclusion about these new technologies.

Harvesting vibration energy to power wearable devices has become a hot research topic, while the output power and conversion efficiency of a vibration energy harvester with a single electromechanical conversion mechanism is low and the working frequency band and load range are narrow. In this paper, a new structure of piezoelectric electromagnetic coupling up-conversion multi-directional vibration energy harvester is proposed. Four piezoelectric electromagnetic coupling cantilever beams are installed on the axis of the base along the circumferential direction. Piezoelectric plates are set on the surface of each cantilever beam to harvest energy. The permanent magnet on the beam is placed on the free end of the cantilever beam as a mass block. Four coils for collecting energy are arranged on the base under the permanent magnets on the cantilever beams. A bearing is installed on the central shaft of the base and a rotating mass block is arranged on the outer ring of the bearing. Four permanent magnets are arranged on the rotating mass block and their positions correspond to the permanent magnets on the cantilever beams. The piezoelectric cantilever is induced to vibrate at its natural frequency by the interaction between the magnet on cantilever and the magnets on the rotating mass block. It can collect the nonlinear impact vibration energy of low-frequency motion to meet the energy harvesting of human motion.

This article presents an efficient piezoelectric (PE) energy harvesting (EH) circuit based on the techniques of series synchronized switch harvesting on inductor (Series-SSHI) and maximum power point tracking (MPPT). The MPPT is achieved using the proposed fractional normal-operation voltage (FNOV) method, which is based on the Series-SSHI operating principle. The FNOV method no longer disconnects the PE harvester from the load circuit to measure its open-circuit (OC) voltage. Instead, it measures the peak PE voltage during the normal Series-SSHI operation to enable the continuous EH process. The FNOV-MPPT circuit is implemented based on a variable width hysteresis controller for saving energy. In addition, the prototyped circuit can achieve the figure of merit factor of 2.68 and the maximum MPPT efficiency of 98.1% with the PE OC voltage ranging from 2 to 5 V. The measurements confirm the validity of the proposed FNOV-MPPT solution for the weakly coupled PE harvesters.

At present, most piezoelectric energy harvesters are developed based on a single piezoelectric transducer (PZT), but in practical applications, a vibration source can be equipped with piezoelectric transducer array in order to harvest more power. The time-sharing multiplexing scheme is mainly employed for multi-input piezoelectric energy harvesters. There is less study on the synchronized multi-input piezoelectric energy harvester. In this paper, a multi-input synchronous electric charge extraction (MI-SECE) interface based on buck structure for piezoelectric energy harvesting is proposed. Both theoretical analysis and experimental test results demonstrate the effectiveness of the proposed interface. The results show that the MI-SECE interface can extract energy from multi-PZTs simultaneously with any phase difference (0-2π).

An efficient self-powered synchronous electric charge extraction CMOS interface circuit dedicated to piezoelectric harvesters is proposed in this paper. Self-powered peak detection (PKD) and switch circuits are used to reduce quiescent current so that the backup or pre-charged power can be saved. A new low phase lag (LPL) PKD circuit is designed to improve the synchronous extraction efficiency, which only requires one detection capacitor to perform positive and negative PKD. The circuit can be set at general mode (G-mode) or LPL mode (LPL-mode). Under LPL-mode, the phase lag can be reduced typically by 50%, the synchronous extraction efficiency can obtained up to 94%, while the output power can reach 659 μW when the piezoelectric transducer original opencircuit voltage Voc,org = 5 V, which is 3.56 times of that of full-bridge rectifier standard energy harvesting circuit at the maximum power point. The minimum harvesting startup voltage is 1.7 V and is independent of the energy storage capacitor voltage VDC. The harvesting efficiency can still reach 71.3% at Voc,org = 5 V. The size of the active area is 0.5 mm2 in a 0.18-μm CMOS technology. Circuit may be invoked as a functional block for energy autonomous wireless sensor network node of the Internet of Things.