Search

Design of low-voltage and efficient energy-harvesting circuits is becoming increasingly important, particularly, for autonomous systems. Since the amount of energy that can be harvested from the surrounding environment is limited, the available output voltage of a harvester is low. Therefore, the design of a low-input-voltage (low-VIN) up-converter is critical to self-powered systems [1-3]. Moreover, the form factor is very constrained in applications such as wearable electronic devices and sensor networks. Recently, low-VIN charge pumps (CPs) for energy harvesting has been compared with DC-DC converters using a large inductor [1-3]. CPs introduced in [1] and [2] use the advanced process technology to push VIN down to the subthreshold region. The CP in [1] introduces a forward-body-biasing (FBB) technique, which improves the voltage conversion efficiency (VCE) for low VIN but shows poor power conversion efficiency (PCE). The CP in [2] achieves the lowest operation voltage. However, the design with a 10-stage CP provides low output power. This paper presents a CP with switching-body-biasing (SBB), adaptive-dead-time (AD), and switch-conductance (SW-G) enhancement techniques to improve the PCE for low VIN as well as to extend the maximum load current.

An ac-dc rectifying system for vibration energy harvesting is proposed to generate outputs of four different voltage levels with a single power source. The proposed dual-output rectifier uses only four diodes, similar to a conventional single-output full-bridge rectifier. A switched-capacitor down-converter provides two output voltages from a single input from the voltage doubler by using the proposed load balancer with a low design complexity. The proposed system is implemented in a 0.35-μm CMOS process, and it occupies an area of 0.143 mm 2.

This paper presents a dc-dc boost converter with the maximum power point tracking (MPPT) technique for thermoelectric energy harvesting applications. The technique realizes variation tolerance by adjusting the switching frequency of the converter. A finely controlled zero-current switching (ZCS) scheme together with the accurate MPPT technique enhances the overall efficiency of the converter because of an optimal turn-on time generated by a one-shot pulse generator that is proposed. Moreover, the ZCS technique can deal with low- and high-temperature differences applied to the thermoelectric generator. This allows a wider range of conversion ratios compared to those of conventional converters used for thermal energy harvesting. Experimentally, the converter implemented in a 0.35-μm BCDMOS process had a peak efficiency of 72% at the input voltage of 500 mV while supplying a 5.62-V output.

This brief presents a regulated charge pump (CP) with an integrated optimum power point tracking (OPPT) algorithm designed for indoor solar energy harvesting. The proposed OPPT circuit does not require a current sensor that consumes power proportionally to the load. The solar cell voltage is regulated at the optimum power point; the CP output is regulated according to the target voltage. The controller of the OPPT circuit and CP dissipates only 450 nW; thus, the proposed technique is appropriate for indoor solar energy harvesting applications under dim lighting conditions.

This paper presents a boost converter with the maximum power point tracking (MPPT) technique for thermoelectric energy harvesting (EH) applications. The technique realizes variation tolerance by adjusting the switching frequency fSW of the converter. A finely controlled zero-current switching (ZCS) scheme together with the accurate MPPT technique enhances the overall efficiency (η) of the converter because of an optimal turn-on time generated by a one-shot pulse generator that is proposed. Moreover, the ZCS technique can deal with low and high temperature differences applied to the thermoelectric generator. Experimentally, the converter implemented in a 0.35 um BCDMOS process had a peak of 72% at the input voltage VIN of 500mV while supplying a 5.62V output.

This paper presents a regulated charge pump (CP) with an integrated optimum power point tracking (OPPT) algorithm designed for indoor solar energy harvesting. The proposed OPPT circuit does not require a current sensor that consumes power proportionally to the load. The solar cell voltage is regulated at the optimum power point; the CP output is regulated according to the target voltage. The controller of the OPPT circuit and CP dissipates only 450nW, so the proposed technique is appropriate for indoor solar energy harvesting applications under dim lighting conditions.