Integrated synchronous electric charge extraction system for piezoelectric energy harvesters

This paper presents a self-powered interface circuit for micromachined piezoelectric energy harvesters (PEH). The system implements the Synchronous Electric Charge Extraction (SECE) technique. Micro- and millimeter-scale PEHs are usually limited to tens or hundreds of microwatts with output voltages that typically do not exceed 1-3 V. Through system- and circuit-level optimizations the proposed interface can operate from as little as 1.5 μW, and can cold-start from a completely discharged state with PEH open circuit AC voltages as small as 900 mV_pk. The system can operate up to 7 V_pk with extraction efficiency as high as 86%. The circuit is designed for the XFAB 0.35 μm CMOS process.