A self-adaptive switched-capacitor voltage converter with dynamic input load control for energy harvesting

Abstract

This paper presents an implementation of a fully-integrated switched capacitor voltage converter with self-adjusting source loading. A charge control unit ensures improved load matching to the power source, which can be an RFID antenna or vibration energy harvesting generator. In conjunction with an adaptive stacking scheme voltage-up conversion is also realized leading to capacitor storage voltages which are higher than the generator voltage amplitudes. This and the improved load matching result in a higher generator output power. In addition, due to the switched capacitor charge pump no diode for rectification is necessary. The converter design is completely implemented and fully-integrated in a standard 0.35 µm twin-well CMOS process. Generator powers of up to 780 µW can be treated, and maximum conversion efficiency is close to 48%. Input voltage amplitudes are possible between 0.5 V – 2.5 V , while the supply voltage range is 0.9 V – 3.6 V.