Triboelectric nanogenerators (TENGs) have emerged as a promising solution for powering Internet of Things (IoT) sensor nodes and wearable electronics, owing to their use of low-cost, lightweight, and environmentally friendly materials. However, the distinctive characteristics of their electrical output, such as high voltage and time-varying internal capacitance, pose significant challenges for the design of efficient power management circuits (PMCs). The high output voltage of TENGs, which often exceeds the safe operating limits of integrated-circuit (IC) technologies, renders conventional IC-based PMCs unsuitable for optimal energy extraction. As a result, board-level PMCs, free from these voltage constraints, are essential for effectively managing the output power of TENGs. This article presents a comprehensive classification and critical review of recent board-level PMC designs tailored for TENG applications. Using a generic block diagram as a framework, various implementation strategies for each functional block are analyzed, highlighting their respective benefits and limitations. Particular focus is given to switching-stage configurations around the rectifier, which enable advanced techniques, such as synchronous electric charge extraction and synchronous switched harvesting on inductor. A comparative analysis of representative PMCs is conducted based on key mechanical and electrical performance metrics. Finally, unresolved challenges and promising research directions are discussed, providing insights into future development of high-efficiency TENG-based energy harvesting systems.

A bipolar quad-output regulating rectifier for wireless power transfer (WPT) is presented. Using only five power switches, it provides four independently regulated bipolar outputs. A coil-reused DC-DC mode sustains operation under heavy-load conditions beyond the RX input power limit. The rectifier achieves up to 173mW output power, 91% peak efficiency, and fast transient recovery.

This article presents a globally optimized radio frequency (RF) energy harvesting system that leverages the novel concepts of 3-D maximum power point tracking (3-D MPPT) and collaborative source reconfiguration to achieve high MPPT accuracy and a wide input power range. The proposed 3-D MPPT coordinates the energy sources, optimizes the rectifier outputs, and regulates the rectifier stages for global efficiency optimization. A multi-level regulating DC–DC converter integrated with a reconfigurable rectifier enables synchronized dual-band RF energy harvesting. The reconfigurable buck–boost converter employs hysteretic control to regulate each rectifier output voltage at its respective maximum power point (MPP) and delivers a stable output through pulse-frequency modulation (PFM) with adaptive inductor on-time. The DC–DC converter dynamically connects a rechargeable battery (emulated by a power source and a resistor) to either the source or the load, supplementing insufficient energy or recovering surplus energy, thereby significantly extending the input power range. Fabricated in a 180-nm CMOS process, the prototype dual-band RF energy harvesting interface achieves a peak end-to-end efficiency of 71%, a sensitivity of −24.1 dBm, and wide high-power conversion efficiency (PCE) input power ranges of 15.5 and 20.5 dB at 433 and 900 MHz, respectively.

A vibration piezoelectric energy-harvesting (PEH) sensor interface IC including high-efficiency power management and readout circuit for structural health monitoring is presented in this paper. The PEH interface consists of a parallel synchronized switched harvesting on inductor (SSHI) rectifier, and a novel duty cycle based maximum power point tracking (MPPT) circuit implemented with comparators and a switched capacitor. The comparators in both the SSHI and MPPT controllers are dynamically biased to provide fast response with low power. The switched capacitor based MPPT can tune the output voltage to suit the input effectively with a simple circuit structure. Moreover, the vibration frequency can be monitored to wake up the readout circuit when a certain threshold (20 Hz) is surpassed, indicating a possible catastrophic event. The readout circuit includes a low-power amplifier with dynamic bias, providing a programmable gain of 4/8/32/128 for the following 12-bit SAR ADC. The proposed system is implemented in a 55 nm standard CMOS technology. Experimental results show that a peak MPPT efficiency of 98.7% and up to 711% output power enhancement are achieved at 133 Hz resonance frequency. Moreover, the event driven wake-up of the readout circuit is successfully demonstrated. With a 11.3-bit ENOB achieved in the SAR ADC, the vibration frequency, temperature, and strain can be extracted from the proposed interface IC.

This work proposes a one-stage bidirectional rectifier with a pre-charge voltage (VPC) based perturb-and-observe (P&O) maximum power point tracking (MPPT) algorithm for triboelectric energy harvesting. The proposed VPC-based MPPT dynamically locates the true MPP while accounting for circuit non-idealities, using a simplified implementation compared to conventional P&O methods. Consequently, it achieves 93% MPPT efficiency and 8.86× energy enhancement compared to the full-bridge rectifier.

A single-link wireless power and full-duplex data transfer system is presented. Operating at 40.68MHz, it delivers >50mW maximum output power with 61.1% peak end-to-end efficiency while supporting 17Mb/s uplink using resonance-length keying (RLK) and 3.4Mb/s downlink using instant-carrier-suspension keying (Instant-CSK). The design removes ASK/LSK trade-offs and achieves an aggregate data rate of half the carrier frequency using 180nm TX/RX chips and 15-/8-mm-diameter coils.

This article analyzes the recently emerged resonant current-mode (RCM) topology and compares it with conventional voltage-mode (VM) rectifiers. Building upon prior RCM designs, a three-phase RCM rectifier is proposed to achieve a wider output power range and higher power efficiency, enabled by residual-free charge delivery through a bypass-capacitor-based mechanism. By incorporating a low-power freewheeling phase, the rectifier supports in situ output voltage regulation and inherently enables load-shift-keying (LSK)-based uplink data transfer, eliminating the need for additional voltage regulators or data links. A digitally assisted adaptive zero-voltage switching (ZVS) technique with fast delay compensation is implemented to minimize conduction losses in the power stage. Fabricated in a 180-nm CMOS process, the prototype occupies a silicon area of 0.4 mm². Measurement results demonstrate reliable hysteresis output regulation at 3.3V, while the output voltage can span a wide range from 2.2 to 4.4 V. The output power ranges from 0.4 to 209.4 mW. A peak power conversion efficiency (PCE) of 94.5% is achieved at 90.8-mW output power. The PCE remains above 80% for all tested output voltages (2.2, 3.3, 4.4 V) when the load current exceeds 1mA.

Due to the better performance of the Wide Band Gap (WBG) devices, there has been a paradigm shift toward WBG-based power modules for diverse applications like Electric Vehicles (EVs). However, the high parasitic inductance value of power modules hinders these devices from unlocking their full potential. Therefore, this paper comprehensively reviews SiC-based Single Side Cooling (SSC) power modules that benefit from low parasitic inductance. The paper also discusses the need to develop newer power modules using modern packaging methods. The surveyed power modules are categorized into three main groups, namely wire bonding, hybrid, and 3D packaging methods. This classification contains several vital parameters of the studied power modules, such as nominal and Double Pulse Tests (DPT) power ratings, parasitic inductance, size, etc. The main features and characteristics corresponding to the reviewed power modules' packaging methods and techniques are also briefly described. Finally, a thorough discussion about challenges and future trends is highlighted before concluding the paper.

This paper presents a thermoelectric energy harvesting (TEH) interface that realizes: 1) a multi-channel TEH for maximum power point tracking (MPPT) under uneven temperature conditions, improving efficiency by up to 39.6%; and 2) a tapped-inductor start-up functionality, which can begin operating at 62mV with no additional inductors or series switches. The overall design achieves a 90.51% peak end-to-end efficiency.

Triboelectric nanogenerators (TENGs) have emerged as a promising power solution for autonomous sensors, as they can be constructed using low-cost, lightweight, and environmentally friendly materials. However, the design of the ensuing power management circuit (PMC), intended to maximize energy extraction from the TENG, remains a challenge for circuit designers at both board and integrated circuit (IC) levels, especially due to the unique properties of the TENG output signal. Among the different circuit topologies proposed in the literature, this article focuses on the full-wave rectifier (FWR) with a dual output (DO). It is proposed to incorporate a switch at the input of the FWR-DO to increase the energy extracted from the TENG. The switch is instantaneously closed in synchronization with the maximum and minimum separation between electrodes, thereby generating a short circuit across the TENG. As a result of this short-circuit, the voltage at the two outputs of the FWR-DO can be adjusted independently to optimize energy extraction in both half cycles, which is not possible in conventional FWR-DOs. The proposed circuit, including the synchronized input switch, is evaluated theoretically, by simulations, and experimentally using an in-house fabricated TENG with a contact-separation topology. Additionally, its performance is compared with that obtained using conventional FWR and FWR-DO topologies. According to the results reported herein, the incorporation of the synchronized input switch generates an improvement in the energy extraction that depends on the symmetry of the voltage-charge plot related to the TENG. For the TENG under test, the energy improvement factor (with respect to FWR-DO) is 18% when the switch is incorporated.

This work presents a battery-powered hybrid resonant pulse-train generator for ultrasonic wireless power transfer (US-WPT) in implantable medical devices. The ASIC integrates adaptive resonance tracking, burst-mode power regulation, a switched-capacitor-resonant architecture, and residual energy harvesting. Fabricated in 0.18μm BCD, it achieves programmable US power, 68.6% Cp-loss reduction, and 21.7% end-to-end efficiency.

This article presents a step-up switched-capacitor (SC) sigma converter with fast transient, high efficiency, and high accuracy for light detection and ranging (LiDAR) receiver applications. The proposed sigma converter combines an unregulated SC converter in the high-voltage (HV) domain and a low-dropout (LDO) regulator in the low-voltage (LV) domain, achieving step-up voltage conversion through a series output connection. The unregulated SC converter operates in the HV domain, achieves high-efficiency power delivery, and boosts voltage in a very high density. At the same time, the LDO ensures fast transient response and accurate load regulation in the LV domain. The prototype achieves 5–16 V voltage boosting with a peak conversion efficiency of 94% at a maximum output power of 3.6 W and up to 152 mW/mm³ power density. The LDO regulator ensures accurate load regulation of 44 μV/mA (0.063% error with full load range) and fast load transient response of 180 ns during 0–200 mA load current transition.

This paper presents an on-chip switched-capacitor converter, named piggybacked SC-on-CSCR, featuring: 1) a power density of 5.67mW/mm2 enabled by eliminating high-voltage switches and jointly utilizing MOM and MOS capacitors; 2) a 12-to-60V input and 1.8-to-5V output achieved through a chip-level modular design; 3) 71.5% peak efficiency enabled by full soft-charging operation; and 4) fast high-voltage startup protection, verified under a 20V/ms power-on slope.

This paper proposes an on-chip sigma regulation system for the accurate and power-efficient control of piezoelectric resonator (PR)-based DC-DC converters to address the challenges of conventional off-chip controllers. A zero-standby sigma-mode is implemented for transient response/output power improvement. Peak efficiencies of 91.2% and 90.7% are achieved for the PR converter and the PR-sigma converter respectively.

This paper presents a 120V/230Vac to 5-to-12Vdc offline power converter consisting of a capacitor-drop AC-DC rectifier and a full-duty-cycle input-series dual-branch DC-DC converter for IoT devices. The proposed converter operates at full-duty-cycle with VCR of D/2 and reduces both the CREC volume and the voltage stress on components, while achieving high efficiency across a broad input and output voltage range. 87.2% peak efficiency, 2.15W output power, and 1088mW/cm3 power density are achieved.

Multiply-accumulators are key cornerstone arithmetic blocks for AI accelerators to achieve high energy efficiency, high accuracy and small silicon area, especially for edge accelerators (Fig. 1, left). The trend of edge accelerators is to use Analog and Mixed-Signal (AMS) domain circuits to improve energy efficiency by reducing voltage swing and integrating more operations into one computation unit [16]. Fig. 1 (right) shows the major issues in existing capacitor-based AMS domain Multiply-ACcumulator (MAC) designs: 1) High energy consumption brought by the high-switching-activity digital logic gates and high-voltage-swing charge-domain analog adders [3, 4]; 2) Significant accuracy loss due to the poor linearity from capacitor parasitic and device mismatch [3]; 3) Large area overhead caused by the parallel unit-capacitors in summation [4, 5].

This paper presents a monolithic single-stage, 4-phase switched-capacitor (SC) hybrid boost converter with 11-to- 20× voltage conversion ratios (VCRs). The 4-phase operating SC hybrid topology is proposed to achieve high VCRs with only three flying capacitors and one inductor. With the SC topology, the average inductor current and the inductor current ripple are much reduced, releasing both power loss and size requirement for the inductor. A four-phase pulse width modulation (PWM) controller is proposed. A successive ramp generation scheme ensures identical pulse widths across three consecutive phases. A driver-assisted auxiliary charge pump provides sufficient driving voltages for the high-side driver and simplifies the overall circuitry. The proposed hybrid boost converter was implemented in a 0.18 μm process. The measurement results show that the converter achieved a 20-24V output voltage range with a 1.2-1.8 V input voltage. 76.7%

A single transmitter source can power multiple ultrasound piezoelectric transducers to enhance the harvested power; however, the received ultrasonic signals vary in phase and amplitude across each element. This paper introduces a fully integrated, high-frequency SSHC rectifier tailored for miniaturized multi-piezo implants to efficiently harvest power at variable phase offsets with a compact form factor. The design incorporates a novel phase-splicing flipping capacitor-sharing technique between all four ultrasound piezoelectric transducers to improve area efficiency. The proposed 4-stage SSHC rectifier can harvest 5.94x more power than a full bridge rectifier operating at a high ultrasonic excitation frequency of 780 kHz. The proposed system was designed using 180-nm BCD process technology for a 2x2 piezoelectric transducer array, with each element featuring an internal capacitor (C_P) of 63.7pF.

A triboelectric nanogenerator (TENG) is a novel device that utilizes contact electrification and electrostatic induction to convert mechanical energy into electrical energy. Its characteristics include high energy density and flexibility, enabling self-powering of electronic devices by harvesting mechanical energy from the environment. Its applications include biomedical devices, wearable electronics, and Internet-of-Things (IoT) sensors. Despite these advantages, extracting electrical energy from TENG remains challenging due to its time-varying nature and low internal capacitance. Effective power-management techniques are essential for TENG energy-harvesting systems, yet research on dedicated integrated power-conversion methods is currently limited. Given the growing interest in TENG, a comprehensive exploration of energy-harvesting systems is critically necessary. This article synthesizes and compares current advancements in triboelectric energy-harvesting systems, emphasizing strategies to enhance output power through various power-conversion techniques. Additionally, it explores techniques employed in other energy-harvesting systems to inspire innovative approaches in TENG system design.

Triboelectric nanogenerator (TENG), advantageous in high energy density and flexibility, is promising as a sustainable energy source but can hardly be used to power edge devices directly due to its high-voltage AC output and varying capacitive impedance. To address it, this work proposes a power-conditioning interface with a fully integrated dual synchronous switch harvesting on capacitors (D-SSHC) rectifier for triboelectric energy extraction. Furthermore, a full digital duty-cycle-based (DCB) maximum power point tracking (MPPT) algorithm is developed to optimize the energy harvesting efficiency with simple implementation and continuous tracking. Designed and fabricated in a 0.18-μm BCD process, the proposed interface can extract energy at a maximum output voltage of 70 V. According to the measurement results, it achieves 99% MPPT efficiency and an energy extraction improvement of 598% compared to a full-bridge rectifier.