Ultra-Low Voltage Push-Pull Converter for Micro Energy Harvesting

Ultra-low power electronic devices, as by the way of example sensor nodes, can be powered by environmental energy harvesting. Thermo generators, solar cells, inductive generators, or radio frequency antennas provide an extremely low output voltage that must be amplified to generate a suitable power supply. This brief presents an autonomous self-starting ultra-low voltage DC-DC converter that starts operations at 9 mV. The circuit is inspired by the classical zero voltage switching push-pull Royer oscillator, suitably modified by using JFETs to operate at low voltages. Thanks to the soft switching of the transistors and to the symmetrical use of the transformer, it can reach high voltage gain, high frequency, and high efficiency. Theoretical and simulation-based optimizations were used to design the converter; the results were experimentally verified with several prototypes.