Improved Rectifier Circuit With Backward Diodes for Low Power Source Harvesting

Most energy harvesting circuits use a Schottky diode rectifier as the first stage in the power conversion system. Schottky diodes are chosen for their low forward-voltage drop which can be as low as 0.15V. Further improvements toward enabling lower voltage sources may be accomplished by using active rectifiers with MOSFET transistors. However such circuits still require an initial start-up phase in which the source voltage needs to exceed the Schottky barrier voltage. As an alternative we propose using backward diodes to build a rectifier with much smaller barrier voltage compared to the Schottky solution. In the past, backward diodes were used in low-voltage diode detectors and are essentially a variation of tunnel diodes. This paper provides both simulation results and an experimental comparative study of the performance of Schottky and backward diodes. The relationship between optimal load, frequency and internal impedance of the voltage source will be discussed as well.