Multi-input energy harvesting interface for low-power biomedical sensing system

In order to capture the energy generated by solar cells and piezoelectric vibration generating elements, an energy harvesting interface circuit, being able to collect two kinds of environmental energies at the same time, is implemented by TSMC 0.35μm CMOS technology. An AC/DC converter with tremendous high conversion efficiency (80^%) is designed and implemented. It utilizes the technology of the full-wave rectification to convert the AC signal, generated by piezoelectric oscillation, into stable DC power. This DC power is combined with the output energy from the solar cell by using a designed switched-capacitor voltage combiner circuit. Finally, the combined voltage will be boosted to the supply voltage level of the following application circuit or to the voltage of rechargeable batteries by the designed PFM boost switching regulator, which has an efficiency of up to 82%.