Abstract: An improved efficient energy harvesting integrated circuit is proposed for piezoelectric energy sources. By using the synchronized switch harvesting on capacitor (SSHC) interface circuit, the charge re-sharing is realized when the internal current source of the piezoelectric energy source crosses zero. The charge on the internal capacitance of the piezoelectric energy sources is transferred to the external capacitor, and then the charge on the external capacitor is reversed through switch control, and finally the reversed charge is transferred back to the internal capacitor. This method avoids the energy loss caused by the charge stored on the internal capacitance of the piezoelectric energy source being neutralized after the internal current source crosses zero, which achieves higher energy harvesting efficiency. The designed SSHC circuit is fabricated with standard 0.18 μm CMOS process, with an active area of about 0.06 mm². The post-simulation results show that when the open-circuit voltage (OCV) of the piezoelectric energy sources is 2.8 V, the maximum voltage flip rate of 81.8% can be achieved. Compared with the standard full bridge rectifying structure, the proposed structure achieves the maximum 8.1X improvement in energy harvesting capability.