I read some paper about the energy harvest, and lots of paper said the induced voltage from, for example, the thermo-electric harvesting could be as low as tens of millivolts in a realistic case, so their input of boost or charge pump is less than 100 mV.
But in some paper, I found the author will set the input from 30 mV to 300 mV, some paper even set the input to 3V. Why? If the induced voltage is only tens of millivolts, then 100 mV should be unless, because you cannot have this high voltage, higher than 100 mV, to feed the boost or charge pump, then why do some authors still let the voltage be so high? Maybe induced voltage can be higher than 100 mV in some other kind of harvest. If so,can anyone give me an example?
Paper example 1(input 30mV~300mV):http://ieeexplore.ieee.org/document/6419064/
Paper example 2 (input 450mV~3V):http://ieeexplore.ieee.org/document/8234200/