Design Of The Low-Voltage Charge Pump With Wide Current Driving Capability For Energy Harvesting Applications

Rapid advances in nanoscale integration have resulted in a new class of miniaturized electronic systems such as smart dust sensors, bio-medical implants, etc.. Battery maintenance and replacement in these applications could be infeasible and prohibitively expensive. Harvesting energy from the surroundings using transducers such as thermoelectric generators (TEG), photovoltaic cells (PV), and piezoelectric sensors, represents an attractive approach to alleviate the energy supply challenge in these systems. However, the output voltage levels of these energy scavengers are lower and much less stable than the supply voltage required for ICs. Therefore, a regulated DC-DC step-up converter is needed. Inductor-based boost converters can achieve low input voltages and high efficiencies but usually require an off-chip inductor, while charge pumps can be fully integrated on chip. Thus, for extremely volume-constrained applications, capacitive charge pumps are preferred.Conventional charge pumping circuits usually have poor output characteristics for low-voltage applications. In this thesis, a low-voltage charge pump circuit with wide current driving capability is proposed. By introducing clock-boosting technique to over drive the charge transfer switches, the new design leads to a better actual conversion ratio and wider current driving capability with less number of stages. In particular, at0.3V supply voltage and1V output voltage, the output current of the present circuit is three times greater than the conventional ones. At last, pulse-skipping modulation is introduced to regulate the output voltage for loading current fluctuation.