High-damping energy-harvesting electrostatic CMOS charger

Because small batteries store little energy, micro-scale systems often trade functionality or lifetime, or both, for integration. Harnessing ambient energy can abate the sacrifice, but only to the extent transducer and circuit efficiencies allow. Optimally adjusting the electrical damping force in the transducer is therefore as important as lowering power losses in the circuit. In kinetic electrostatic harvesters, raising the voltage across the moving parallel plates increases this force, which is what the energy-harvesting 0.35-μm CMOS charger proposed achieves with a 10-nF capacitor C_CLAMP. The system presented harnesses fifteen times (15-×) more energy at 16 V (with 15 nJ/Cycle) than at 4 V (with 1 nJ/Cycle) from 50 -- 250-pF, 60-Hz variations to generate (after discounting loses in the system) a net gain of 8.8 nJ/Cycle at 16 V.