A Fully Integrated Clocked AC-DC Charge Pump for Mignetostrictive Vibration Energy Harvesting

This paper describes a clocked AC-DC charge pump to enable full integration of power converters into a sensor or radio frequency (RF) chip even with low open circuit voltage magnetostrictive vibration energy transducer operating at a low resonant frequency of 10 Hz to 1 kHz. The frequency of the clock to drive an AC-DC charge pump was up-converted with an on-chip oscillator to increase output power of the charge pump without significantly increasing the circuit area. A model of the system including the charge pump and vibration energy transducer is shown. It was validated by HSPICE simulation and measured, resulting in a prototype chip with an area of 0.11 mm(2) fabricated in a 65 nm 1 V CMOS process. The fabricated charge pump was also measured together with a magnetostrictive transducer. The charge pump converted the power from the transducer to an output power of 4.2 mu W at an output voltage of 2.0 V. The output power varied below 3% over a wide input frequency of 10 Hz to 100 kHz, which suggests that universal design of the clocked AC-DC charge pump can be used for transducers with different resonant frequencies. In a low-input voltage region below 0.8 V, the proposed circuit has higher output power compared with the conventional circuits.