This work proposes an energy harvesting platform that is able to convert power from both DC sources (photo-voltaic cells and TEGs) as well as piezo element sources. It does so only using a single input channel to which a single harvester can be connected. The proposed system is able to differentiate between the two source types and adjust the power converter configuration accordingly.For the DC sources, a novel switched-capacitor power converter (SCPC) is proposed, that is able to convert the energy from a harvester that has a maximum power point (MPP) output voltage of 170mV to 5V and a maximum power point output power of 10uW to 50mW. This DC-DC converter offers 119 different positive voltage conversion ratios, with a maximum voltage conversion ratio of 16, using four in-package capacitors. As a result of this high number of conversion ratios, the MPP output voltage of the harvester and the input voltage of the power converter are matched accurately, causing the harvesting efficiency to be very high. A maximum harvesting efficiency of 96.2% is found in simulations. For the piezo element sources, the concept of a flipping-capacitor rectifier (FCR) has been adjusted to work in harmony with the designed SCPC. In a steady-state condition, the capacitors of the SCPC reach specific voltages, such that they can create evenly spaced voltage steps for the flipping operation. With this technique, a voltage flipping efficiency of 0.9375 and a theoretical maximum output power improvement rate (MOPIR) of 32 can be reached. Due to losses in the system, simulation results show a MOPIR of up to 20.0, which is still significantly higher than the state-of-art. The system is designed to work with harvesters with a piezo capacitance of up to 100nF, an excitation frequency of 1Hz to 200Hz and an equivalent FBR maximum power point output power of 1uW to 50mW. An implementation of the proposed system is discussed and simulated. The total active silicon area for the designed system is 2.12mm2 in a 0.18 um TSMC technology.

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This thesis describes the design and prototyping results of a low power wireless power transfer (WPT) system. In particular the design and testing of a transmitter.

Firstly, existing research is discussed and it is found that a significant part of this discusses higher power transfer systems. Here lies the challenge for this thesis: to find an efficient way of transferring a low amount of power wirelessly, with a significant distance between the transmitter and the receiver. Also, existing WPT standards were investigated and their shortcomings are discussed.

Secondly, the design of the transmitter is discussed. It starts out with the fundamental and circuit theory behind wireless power transfer. With this, it is found that tuning capacitors can greatly increase the efficiency of the system. Next, the design of the components in the coupled coils system is discussed, with calculations on equivalent series resistance for different frequencies. Furthermore, the functional block diagram consists of an oscillator, gate driver and inverter circuit and its design choices are discussed. The design concludes with a frequency optimization and simulation results.

Lastly, the design has been built and tested. A transmitter efficiency of 93.4 % has been reached at a coupling of around 0.1. This is at a distance of 20 millimeters. Further improvements may be done with the gate-driver. Control techniques may also prove beneficial for future work. ... Read more