High efficiency MOS charge pumps based on exponential-gain structure with pumping gain increase circuits

Novel MOS charge pumps utilizing an exponential-gain structure and pumping gain increase (PGI) circuits with high voltage transfer efficiency to generate boosted output voltages are described. By using the PGI circuits, the threshold voltage problem of the MOSFET used as a switch is solved, and the limitation of the diode-configured output stage is removed. Thus, the boosted output voltage increases linearly as compared to the pumping stage number. An exponential-gain structure is also presented as a further application of the PGI circuit. By using this structure, fewer voltage pump stages are needed to obtain the required output voltage. For 1.5-V supply voltage operation, a four-time series (1.5 V-to-6 V) is demonstrated using the new techniques. Simulation and experimental results have shown that this design has good efficiency with a low-input supply voltage such as a one battery cell.