Ultra-low-voltage low-power charge pump for solar energy harvesting systems

This paper exploits a new charge pump used in integrated solar energy harvesting systems to improve the power efficiency under ultra low supply of under 0.7 V supplied by on-chip photodiodes. Compared with conventional charge pumps, improvements of 20% in terms of output voltage gain and conversion efficiency can be achieved by using two symmetrical branches and PMOSFET-only transfer transistors per stage. The proposed circuit is implemented in UMC 0.18 mum standard CMOS technology.