Maximum energy transfer condition for piezoelectric energy harvesters with single pulsed vibration inputs

The optimal capacitive load condition is derived for a passive bridge rectifier to harvest the maximum amount of energy when a piezoelectric generator (PG) receives a single vibration pulse (e.g. a button press). When the PG is modelled as a current pulse generator with an internal shunt capacitance (C_P), it is shown that an ideal bridge rectifier collects the maximum energy when its output capacitance is set to 3·C_P. The impacts of the nonzero turn-on voltage and on-resistance of the diodes are also discussed. The experimental results with a 300 mm² lead magnesium niobate-lead titanate PG and a Schottky-bridge rectifier with 0.22 V turn-on voltage demonstrate that the maximum energy transfer occurs at a capacitance ratio of 3.3, collecting 117 μJ from a single button press.