Conventional SSHI (synchronized switch harvesting on inductor) has been
believed to be one of the most efficient interface circuits for piezoelectric
vibration energy harvesting systems. It employs an inductor and the resulting
RLC loop to synchronously invert the charge across the piezoelectric material
to avoid charge and energy loss due to charging its internal capacitor (CPβ).
The performance of the SSHI circuit greatly depends on the inductor and a large
inductor is often needed; hence significantly increases the volume of the
system. An efficient interface circuit using a synchronous charge inversion
technique, named as SSHC, was proposed recently. The SSHC rectifier utilizes
capacitors, instead of inductors, to flip the voltage across the harvester. For
a one-stage SSHC rectifier, one single intermediate capacitor (CTβ) is
employed to temporarily store charge flowed from CPβ and inversely charge
CPβ to perform the charge inversion. In previous studies, the voltage flip
efficiency achieves 1/3 when CTβ=CPβ. This paper presents that the voltage
flip efficiency can be further increased to approach 1/2 if CTβ is chosen to
be much larger than CPβ