A low start up voltage charge pump for thermoelectric energy scavenging

In this paper, an ultra-low-voltage charge pump is presented. Two techniques are used to reduce required number of stages and improve power efficiency, namely clock boosting and V_t cancellation. Clock boosting is employed to increase the output voltage per stage resulting in lower number of stages, and hence smaller output resistance. V_t cancellation is achieved by using an auxiliary circuit that enables the charge pump to operate at input voltages as low as 300mV. Compared to conventional charge pump techniques, the proposed technique is shown to offer higher power efficiency and voltage gain. The charge pump is designed using TSMC 0.25μm CMOS technology.