The forthcoming scenario of the wireless sensor network and the so called pervasive computing would greatly boost if all electronic systems involved in their deployment could feature some sort of energy self-sufficiency. In this application an aggressive power management solution is required in order to collect a sufficient amount of energy in storage elements in general from different power sources. This paper is focused on the development of the power supply systems, in particular on switching converters for energy harvesting applications. Its main goal is the development of high efficiency conversion systems, featuring the minimum number of conversion stages and of magnetic components, and the optimization of the power management. In particular the paper is focused on multi-input/multi-output dc-dc converters, enabling the connection of one or more sources of energy (solar, vibrational, RF, etc.), of some energy accumulation devices (micro-batteries, capacitors, supercapacitors), and several loads (microcontroller, transmitter, sensors, etc.). The modulation techniques and the power management are also discussed, to comply with multi-source/multi-load conditions.