We proposed a vertical vibratory energy harvester using polymer electret and dielectric. A proof mass consists of counter electrode and dielectric beneath it, which faces with electret on base electrode on a substrate. Since dielectric prevents discharge from electret to counter electrode, a narrow gap between mass and electret is feasible. The device can generate the power as far as the input acceleration is enough for the mass to reach the electret surface, even at the frequency apart from the resonant one. It leads to high output power for broad frequency bandwidth. There is almost no hysteresis between the up sweep curve and down sweep one. Thus, the device can generate a stable output against frequency change.
