Energy harvesting and wireless power transfer to power small, low-power and autonomous devices have recently attracted numerous research studies. Due to the lack of energy supplies, DC to DC converters with multiple inputs have been studied to harvest different energy sources simultaneously. In this paper, a proposed pulse skipping modulation method is used to control a multiple input buck boost converter with the output power from 7 μW – 700 μW. The DC to DC converter can achieve a high efficiency of 83.3% at 23.6 μA load current, and the highest efficiency is up to 89.1% at 255 μA current load. The control method offers the flexibility and adaptability in maximum power point tracking and input power contribution. The paper investigates a completed energy harvesting system including a solar cell and 915 MHz RF source and power management circuits.