Low-Power Energy Harvesting Solutions for Wiegand Transducers

This paper analyzes different circuit solutions employing Wiegand magnetic sensors as energy harvesters for supplying lowpower electronic equipment. Wiegand sensors release a ~10us voltage pulse several volts wide when subject to an external, time-varying magnetic field independently on the magnetic flux variation rate. When optimally loaded, a Wiegand device is capable of up to ~100nJ/pulse delivered energy. Due to the sharpness of the magnetic transition, pulse generation occurs regardless of how slow the magnetic field variation is, an attractive feature that enables its use in energy harvesting scenarios even when low-frequency sources are considered. Aim of this work is to investigate the use of Wiegand sensors as small scale energy sources, and discuss and compare low-power harvesting circuits for efficiently interfacing the sensor with a fixed DC bus with a typical voltage range of 3.3V to 5V.