A 0.15 v input energy harvesting charge pump with dynamic body biasing and adaptive dead-time for efficiency improvement

A charge pump using 0.13-μm CMOS process for low-voltage energy harvesting is presented. A low-power adaptive dead-time (AD) circuit is used which automatically optimizes the dead-time according to the input voltage. A negative charge pump is also utilized for high efficiency at low input voltages V_IN. The AD circuit improves efficiency by 17% at V_IN of 0.2 V compared to the fixed dead time circuit as well as enables the charge pump to work at V_IN down to 0.15 V. Dynamic body bias (DBB) and switch-conductance enhancement techniques are applied to a unit stage of the three-stage charge pump. The reverse current flowing through the cross-coupled NMOS switches is prevented and the current transfer is also maximized. Together with the AD circuit and the DBB technique, the maximum output current was improved by 240% as compared to the conventional charge pump design using only the forward body bias.