A Highly Efficient and Adaptable Solar-Energy Harvesting Circuit for Batteryless IoT Devices

In this paper a new on-chip 2^nd generation solar energy harvesting DC-DC converter has been proposed for a battery-less Internet of Things (IoTs) Devices. The propose circuit is design to maximize the transfer efficiency and stability as well as enough high power supply to the back-end loads. Altogether the proposed circuit consists of a cross-coupled charge pump, a maximum power point tracking (MPPT) circuit, a timing control circuit and regulator. The range of input voltage is from 0.5V to 3V. Required boosted output voltage is in the range of 1V to 3.3V. The maximum transfer efficiency is more than 60% and the maximum throughout power is 200μW. A gated clock frequency modulation circuit has been designed and employed in the maximum power point tracking (MPPT) unit to lock the input resistance of the charge pump. In addition, to provide a stable voltage to the load a low dropout (LDO) regulator circuit is used. The experimental results show that the maximum power conversion efficiency (PCE) is 78% at 52μW input power condition.