23.1 A 0.15V-input energy-harvesting charge pump with switching body biasing and adaptive dead-time for efficiency improvement

Design of low-voltage and efficient energy-harvesting circuits is becoming increasingly important, particularly, for autonomous systems. Since the amount of energy that can be harvested from the surrounding environment is limited, the available output voltage of a harvester is low. Therefore, the design of a low-input-voltage (low-V_IN) up-converter is critical to self-powered systems [1-3]. Moreover, the form factor is very constrained in applications such as wearable electronic devices and sensor networks. Recently, low-V_IN charge pumps (CPs) for energy harvesting has been compared with DC-DC converters using a large inductor [1-3]. CPs introduced in [1] and [2] use the advanced process technology to push V_IN down to the subthreshold region. The CP in [1] introduces a forward-body-biasing (FBB) technique, which improves the voltage conversion efficiency (VCE) for low V_IN but shows poor power conversion efficiency (PCE). The CP in [2] achieves the lowest operation voltage. However, the design with a 10-stage CP provides low output power. This paper presents a CP with switching-body-biasing (SBB), adaptive-dead-time (AD), and switch-conductance (SW-G) enhancement techniques to improve the PCE for low V_IN as well as to extend the maximum load current.