This paper presents a self-powered interface circuit to rectify and manage the AC output of the piezoelectric energy harvesters (PEH) by utilizing Self-Investing Synchronous Electric Charge Extraction technique (SI-SECE). The system invests charges from the battery to PEH to improve the electromechanical coupling factor and consequently the energy extraction by utilizing only one external component. The circuit was implemented in 180 nm CMOS technology where high voltage (HV) MOS transistors are utilized to tolerate high open circuit output voltages of PEHs. MEMS PEH with 4.7 nF inherent capacitance has been used to charge a 1 mu F storage capacitor. Proposed interface circuit extracts 18.55 mu W that is 33 % more than traditional SECE (13.95 mu W) for 250 Hz PEH excitation frequency and 2.3 V piezoelectric open circuit voltage amplitude. At the output power of 48.5 mu W, maximum power conversion efficiency of 62.4% is achieved as charge investment and corresponding conduction and switching losses on investing transistors. SI-SECE delivers power with 4.5x relative performance improvement over on-chip full-bridge rectifier.