Vibration Energy Conversion Power Supply Based on the Piezoelectric Thin Film Planar Array

Abstract

Vibration energy harvesting has received much attention as a new type of power solution for low-power micro/nano-devices. However, VEH (vibration energy harvester) based on PVDF (polyvinylidene fluoride) piezoelectric materials have a low output power and energy conversation efficiency due to the relatively low piezoelectric constant, coupling coefficient, and dielectric constant. For this reason, we design a vibration energy conversion power supply, which consists of a VEH with a PVDF piezoelectric thin film planar array vibration structure and an energy harvesting circuit for regulating the electric energy of multiple sources. Furthermore, our solution was validated by simulations of structural dynamics in COMSOL and equivalent circuits model in Multisim. From the circuitry simulation results, the output current and the charging period increase and decrease, doubling, respectively, for each doubling of the number of array groups of films. Moreover, the solid mechanics simulation results show that the planar array structure makes the phase and amplitude of the input vibration waves as consistent as possible so that the same theoretical enhancement effect of the circuitry model is achieved. An identical experimental test was implemented with vibration conditions of 75 Hz-2.198 g. The fabricated harvester quickly charged the 22 V-0.022 F ultracapacitor bank to 5 V in 24 min. The maximum open circuit voltage and output power, respectively, were 10.4 V and 0.304 mW. This maximum charging power was 11.69 times higher than that of a single film. This special power supply can replace batteries to power low-power electronics deployed in vibrating environments, thus reducing the maintenance costs of equipment and environmental pollution rates.

Keywords: PVDF piezoelectric material; ambient power; battery-less; energy harvesting interface circuit; energy scavenging; self-powered power supply; vibration energy harvesting.

Figure 1

Two Kinds of Typical Vibration Acquisition Structure: (a) Cantilever Beam. (b) Simply Supported Beam.

Figure 2

Vibration Mode of Piezoelectric Oscillator: (a) LE Model (b) TE Model (c) FS Model (d) TS Model.

Figure 3

Vibration Signal of the Vibration Motor: (a) Amplitude Spectrum; (b) Acceleration Amplitude of the Time Domain.

Figure 4

COMSOL 3D Model of the PVDF Piezo-film Vibration Energy Harvester Based on Motor-generated Vibration Signals.

Figure 5

Simulation Results of the Harvester under the Motor Vibration Excitation: (a) Frequency Response of the Output Voltage; (b) Frequency Response of the Output Power.

Figure 6

Photograph of Piezoelectric Thin Film.

Figure 7

Rectifier Output Wave for the Piezoelectric Film under Motor Excitation.

Figure 8

The Diagram of the Testbench.

Figure 9

A Circuit for the Control of Multiple Current Sources.

Figure 10

Diagram of the Charging Circuit of Parallel Multi-sources in Simulation Software.

Figure 11

Capacitor Charging Voltage for a Five Piezoelectric Film Parallel Equivalent Simulation Circuit.

Figure 12

Simulation Results of the Harvester of the Five Piezo-films Planar Array under the Motor Vibration Excitation: (a) Frequency Response of the Output Voltage; (b) Frequency Response of the Output Power.

Figure 13

VEH Based on the Vibration−Capturing Structure of the Piezo-film Planar Array.

Figure 14

Physical Product and the Energy Storage Test of Multi-source Charging Circuit: (a) Physical Product and Test Preparation of Multi-sources Charging Circuit; (b) Electric Circuit of Harvesting with Successfully Lit LED.

Figure 15

Equipment Setup of Vibration Energy Harvesting Testing.

Figure 16

Voltage Waveform in Charging Experiment: (A) Rectifier Output Wave; (B) The Voltage Waveform of the Supercapacitor in 0–3.5 V; (C) The Output Voltage of the Vibration Energy Harvesting Circuit; (D) The Voltage Waveform of the Supercapacitor for 3.5–5 V.