Abstract: Piezoelectric materials have good application prospects in the fields of vibration energy harvesting and structural vibration control due to their good electromechanical coupling characteristics. The piezoelectric interface control circuits based on synchronous switch and inductance can adjust the piezoelectric voltage amplitude and phase according to the working principle of oscillation circuit, optimizing the electromechanical energy conversion in piezoelectric vibration systems. The optimized synchronous electric charge extraction technique based on the interface control circuit mentioned above has realized the efficient piezoelectric energy conversion from vibration to electrical energy. This paper proposed a semi-active piezoelectric damping control circuit derived from the optimized synchronous electric charge extraction circuit. The energy conversion phenomenon between the primary and secondary sides of flyback transformer was unitized, the structure vibration suppression was then realized by transferring the electrical energy into the mechanical energy in piezoelectric vibration control systems. The new circuit which combines the piezoelectric electric charge energy extraction and the semi-active damping control approach realized the bidirectional control of piezoelectric vibration system, with a core of flyback transformer. The corresponding control circuit and its working principle were introduced, the piezoelectric vibration damping model under the new synchronized switch damping technology was also established. An experimental platform for the vibration control of a piezoelectric cantilever beam was built and the theoretical model is verified through experiments, the stability problem of the vibration control system was also solved through a simpler control approach.