Energy Harvesting Circuit for Road Speed Bumps Using a Piezoelectric Cantilever

This paper presents an energy harvesting circuit for road speed bumps, in which energy is generated from passing over vehicles. As a speed bump energy harvester is mostly idle and generates energy intermittently for a short period, a major design issue is reduction of static power dissipation during the idle time. To address the problem, the proposed circuit adopts sleep mode. A speed bump energy harvester based on a piezoelectric cantilever translates kinetic energy generated by a passing over vehicle into electrical energy. Upon detection of the voltage generated by the piezoelectric cantilever, the proposed circuit wakes up the converter and extracts maximum power from the piezoelectric cantilever through impedance matching. When the piezoelectric cantilever does not generate voltage, i.e., a vehicle is not passing over the speed bump, the circuit shuts down major power hungry blocks to reduce the static power dissipation. The proposed circuit is designed in a 0.18 μm CMOS technology. Simulation results indicate that the typical static power dissipation of the proposed circuit is only 443 pW for the vehicle speed of 20 km/h, while the power dissipation of the circuit without sleep mode is 16.3 μV, an increase by a factor of 36,800 times.