Shunt-diode rectifier: a new scheme for efficient piezoelectric energy harvesting

Abstract

This paper highlights the interest of shunt-diode rectifiers to optimize the performances of piezoelectric vibration energy harvesters based on linear load adaptation. It provides, for the first time, a full analytical study of the input power and frequency bandwidth of such a system. We show that this architecture is well-suited for piezoelectric energy harvesting. In the presented approach, a so-called shunt diode is connected across the electrodes of the piezoelectric transducer, which makes the piezoelectric voltage unidirectional instead of alternating. Thus, DC-DC converters usually used for power optimization can be directly connected to the transducer. We show that weakly-coupled linear inertial piezoelectric energy harvesters generate higher power when connected to a shunt-diode rectifier than to a bridge rectifier. Moreover, the frequency bandwidth is enlarged by the use of the single-diode shunt rectifier, especially for strongly-coupled piezoelectric generators. The proposed architecture is also interesting for low piezoelectric voltages, at which voltage drops across the diodes used for AC-DC conversion critically degrade the power efficiency. Experimental results validate the presented analytical study and highlight the higher efficiency of the shunt-diode rectifier circuit. Compared to a standard bridge rectifier architecture, we demonstrate an increase of +43% output power on a weakly-coupled generator and an increase of +5% bandwidth on a strongly-coupled generator.

A review of energy harvesting using piezoelectric materials: state-of-the-art a decade later (2008–2018)

“…Brenes et al in 2018 [308] introduced the application of the shunt-diode method in piezoelectric energy harvesting along with an impedance matching circuit designed for generators with strong electromechanical coupling. The shuntdiode is directly connected to the piezoelectric transducer to provide a unidirectional voltage signal to be fed to a DC-DC converter designed for power optimization.…”

Maximum power point of piezoelectric energy harvesters: a review of optimality condition for electrical tuning

“…Among the existing topologies, a 2-stage load adaptation topology called "buck-boost topology without input filtering capacitor" [85,67,86] has been proposed. It is based on the use of rectifier architecture (either FB [87] or shunt [37]) directly followed a DC-DC converter whose switching frequency is significantly larger than the frequency of the piezoelectric vibration. If the buck-boost converter is in discontinuous conduction mode, its equivalent impedance is independent of the load placed at its output.…”

“…The case where the FB rectifier is replaced by a shunt-diode rectifier [37] is, though interesting, very complex to treat mathematically so that numerical computations are the only way to draw conclusions. Unfortunately, contrary to the FB technique, no simple and interpretable mathematical expression can be found for the 2-stage load adaptation shunt-rectifier technique [37]. Numerical simulations suggest that the condition to reach the maximum available power is 2 > 3.4 /4.…”

“…Examples of waveforms at the maximum power point are depicted in Figure 15. If > 1, one can simplify the expressions given in [50] into (37).…”

“…Integrated versions also exist for some of these techniques [35]. Following [36], other recent studies have replaced these bridge rectifiers by a shunt diode and studied the impact resulting from this change on the electromechanical energy conversion [37] [38]. Not only do such shuntdiode architectures improve the electrical power efficiency at low voltage levels but they also retroactively increase, under specific conditions, the amount of mechanical energy transferred into mechanical motion of the seismic mass, which brings larger amounts of energy into the electrical circuit.…”