Development of high-efficiency rectifier circuits for piezoelectric energy harvesting systems

Mahesh Edla

doi:10.25918/thesis.200

In modern days, high energy demand and consumption is one of the most pressing challenges faced by human beings. Thus, many scientists and researchers are perpetually searching for renewable energy resources, such as sunlight, wind, thermal, heat, and mechanical vibrations. Extracting energy from renewable energy sources is known as energy harvesting (EH). In addition, the EH process from renewable energy sources for the purpose of powering small scale power electronic devices is becoming increasingly prevalent. One of the simplest ways of converting vibrational energy sources into electrical energy is using a piezoelectric device (PD), also this topology is known as piezoelectric energy harvesting (PEH) systems. In the field of PEH, numerous improved and novel power electronic circuit methods that enable the most efficient power conversion circuits in terms of both linear and non-linear circuits have been proposed. However, most power electronic devices require a stable direct current/voltage (DC) and adequate power supply, whereas the PEH process produces a very low and erratic nature of electrical energy in the form of alternating current/voltage (AC). Thus, a conventional way of converting AC into direct current/voltage (DC) is by using a full bridge rectifier (FBR) circuit. However, the rectified voltage and power are low due to forward voltage drop across the diodes employed in the FBR circuit. In addition, the FBR circuit provides ripples in its output waveform. Therefore, to enhance the efficiency of the PEH systems, this thesis aims to address this challenge by investigating three methods: (1) reducing the forward voltage drop, (2) stabilising the output waveform of the FBR circuit, and (3) boosting the low ac voltage that is generated by the PD into high DC voltage at both high and low frequencies. To achieve the abovementioned methods, this thesis starts by proposing several improved and novel circuits, including (1) an improved self-powered H-Bridge circuit for voltage rectification at high frequency, and (2) an improved H-Bridge rectifier circuit (HBR) for voltage rectification and reduce the ripples at low frequency from human motion. It then improved (3) the HBR circuit into a dual-stage H-Bridge circuit (DSHBR) for improving the rectification process, stabilising the output waveform at both high and low frequencies. The ability of the DSHBR circuit to charge a solar battery was also investigated. It then investigated (4) a novel single-stage rectifier-less boost converter (SSRBC) for the conversion process from low AC voltage generated by the PD into high DC voltage and power. In this thesis, one additional study, namely (5) a non-linear switching circuit (INLSC) for active voltage rectification and ripple reduction, is also investigated to improve the efficiency of the PEH systems. The ability of the INLSC for powering a 7-segment display was then investigated. The outcome of this study showed that (1) using an H-Bridge circuit, maximum output power (2.01 μW), which is significantly higher than conventional circuit, was achieved with an input voltage of 0.5 Vac; (2) using an improved HBR rectifier circuit from human motion, maximum output voltage and output power (3.8 Vdc and 25.08 μW) was achieved with human walking; (3) using the DSHBR circuit, a dramatic increase in maximum output voltage and power (3.4 Vdc and 115.6 μW) was achieved with human motion-induced vibration test; (4) using a novel SSRBC circuit, a significant rise in both maximum output voltage and power (5.1 Vdc and 281.1 μW) was achieved with the input voltage of 0.5 VP. Besides, from the additional study, (5) using INLSC circuit, a dramatic increase in maximum output voltage and power (6.5 Vdc and 469.1 μW) was achieved with the input voltage of 0.45 Vac. Application-wise, the proposed dual-stage circuit is able to charge a battery (1.2 V, 4 mA) that is commonly used in solar garden lights, whereas the proposed non-linear switching circuit is able to power a manually connected 7-segment display that is commonly used for traffic applications. These advancements can contribute to the improvement in the future of piezoelectric energy harvesting systems. In addition, this is highly beneficial for the low-power electronics industry.

Development of high-efficiency rectifier circuits for piezoelectric energy harvesting systems

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Development of high-efficiency rectifier circuits for piezoelectric energy harvesting systems

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