An Upconversion Management Circuit for Low-Frequency Vibrating Energy Harvesting

This paper proposes a high-efficiency small-size upconversion management circuit for low-frequency vibrating energy harvesting. Due to low vibrating frequency (32 Hz), the transformer of a traditional matching circuit has a large inductance (9171 H) and a large size (> 50 x 50 x 50 mm(3)). An upconversion matching circuit with a smaller inductance (25.3 H) and a smaller size (< 20 x 20 x 20 mm(3)) is developed. By using the smaller size upconversion matching circuit, higher charging power and ultimate charging voltage can be obtained at a higher frequency (3.28 kHz). The matching circuit can efficiently work at a wide vibrating frequency range. In order to drive the wireless sensor with a higher consumption power (110 mW), an instantaneous discharging circuit is developed that is suitable for weak vibrating energy harvesting (406 mu W). The instantaneous discharging circuit can accumulate weak energy from the vibrating transducer during a long period, and it can provide a higher power output in a very short time. While the voltage across the storing capacitor is over 0.36 V, the instantaneous discharge circuit can drive a wireless sensor with an output power of 110 mW at a distance of over 80 m. The small-size high-efficiency upconversion management circuit can be used in many other low-frequency energy harvesters.