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An adaptive energy harvesting system for high voltage piezoelectric generators is presented in this paper. Maximum power point tracking scheme is applied in the adaptive system. Low-power-consumption schemes are applied in the control system and harvesting circuit. A self-startup circuit is also applied to the system. Theoretical analysis was explored to determine optimal parameters for the harvesting system. Experiments were done to verify the theoretical analysis. The experimental results show that the harvesting system can achieve an efficiency of 17.5 ∼ 73.3% for piezoelectric generator with a peak open-circuit voltage of 6 ∼ 20 V. And the harvesting system can be self-powered from low input power as 25 μW. The average power consumption of the microcontroller can be low as 3.5 μW. [ABSTRACT FROM AUTHOR]

This paper presents a two-stage adaptive boost converter with low-voltage starter for low voltage piezoelectric energy harvester. The adaptive technique can deal with a range of input voltages from the piezoelectric generator for required output voltages. The parameters of the converter including inductance, switching frequency, duty cycles and the input/output voltage are studied for conversion efficiencies. The experiment results show that a two-stage adaptive boost converter can achieve a conversion efficiency of 84.3%∼91.3% for a piezoelectric harvester in the considered low voltage range to charge an 1.5Venergy storage device. [ABSTRACT FROM AUTHOR]

An automatic stage transition converter for an inductive power transfer system is presented in this paper. An effective control strategy with two working stages of independent energy injection stage and free resonance stage is employed in the proposed converter. With the automatic stage transition strategy, when the frequency of the resonance network changes, the ending time of the free resonance stage is automatically determined. At the same time, the phase angle of the free resonance stage is automatically set as half a resonant cycle. As the stage transition is not triggered by the switches, the switch motion can be executed in advance of the transition moments. Time margins are offered for every switch in the converter, which make the switching moments of the switches flexible and the control simple. Another feature of this converter is that during the energy injection stage, the energy is injected into the inductor independently. Therefore, the input power can be easily regulated by adjusting the energy injection time. A prototype for the converter and the inductive power transfer system was implemented experimentally. From the experimental results, the automatic stage transition and power regulation capability of the proposed converter are verified. The switches all operated at the soft switch condition. When the energy injection time was adjusted from 10 μs to 25 μs, the output power changed from 143 W to 740 W. [ABSTRACT FROM AUTHOR]

In a traditional inductive coupling power transfer (ICPT) system, the converter and the resonant network are strongly coupled. Since the coupling coefficient and the parameters of the resonant network usually vary, the resonant network easily detunes, and the system efficiency, power source capacity, power control, and soft switching conditions of the ICPT system are considerably affected. This paper presents an ICPT system based on a power converter decoupled from the resonant network. In the proposed system, the primary inductor is disconnected from the resonant network during the energy injection stage. After storing a certain amount of energy, the primary inductor is reconnects with the resonant network. Through this method, the converter can be decoupled from the resonant network, and the resonant network can be tuned under various coupling coefficients. Theoretical analysis was explored first. Simulations and experimental work are carried out to verify the theoretical analysis. The results show that the proposed ICPT system has the virtues of low power source capacity, independent power control, and soft switching operation under different coupling coefficients. [ABSTRACT FROM AUTHOR]