This thesis presents a self-powered adaptive piling-up rectifier-less synchronized switch-harvesting-on-inductor (APReL-SSHI) interface for piezoelectric energy harvesting (PEH). The proposed interface introduces two distinct operational modes, energy transfer mode (ETM) and voltage piling-up mode (VPM), that adaptively select the optimal mode based on varying vibration excitation levels to maximize energy extraction. This adaptive piling-up mechanism effectively addresses the inherent limitation of the narrow optimal rectified voltage range (ORVR) seen in conventional S-SSHI rectifiers by enabling capacitor charging beyond standard thresholds. Experimental results demonstrate that the proposed APReL-SSHI circuit achieves up to 5.27 times the maximum output power compared to a full-bridge rectifier (FBR) and expands the ORVR by 4.16 times compared to a conventional S-SSHI circuit. Consequently, the APReL-SSHI delivers superior balance between these two key performance metrics relative to existing state-of-the-art rectifiers. Moreover, the circuit uniquely exhibits a secondary output power peak, reaching approximately 94\% of maximum power when operated above the standard maximum power point (MPP) voltage. Under constant input conditions, the voltage associated with this secondary power peak is easily adjustable, thereby facilitating direct voltage matching for diverse load requirements and achieving near-MPP tracking efficiency of 94\% without the need for an additional MPPT controller.