An active rectifier with optimal flip timing for the internal capacitor for piezoelectric vibration energy harvesting

This paper presents an active rectifier, which aims to extract maximum power from piezoelectric generators for vibration energy harvesting. A nonlinear impedance matching scheme called Synchronized Switch Harvesting on Inductor (SSHI) is highly effective [1]. However, control of the internal capacitor flip timing is complicated to result in a complex controller or suboptimal flip timing. We proposed an active rectifier based on the series SSHI configuration [2]. It ensures an optimal capacitor flip timing, yet the controller is simple to dissipate low power and hence achieve high efficiency. One potential problem of the series SSHI scheme is a non-robust operation due to parasitics and a variety of characteristics of the piezoelectric generators. We present an improved rectifier, which address the problem. The improved rectifier is designed in 0.25 μm BiCMOS process. Post-layout simulation results indicate robust operation and high efficiency of 93%, which is comparable to the original design in [2] and far higher than other existing SSHI rectifiers reported.