Optimization of AC-DC converter for magnetic energy harvesting device

In this paper, we propose the optimum condition of AC-DC converter for a magnetic energy harvesting device. When this device is used as an energy source for wireless sensor applications, the DC output voltage should be larger than 1.5 V. First of all, we investigate the basic properties of an AC-DC converter with a Cockcroft-Walton circuit. Experimental results reveal that the optimum conditions are related with the number of steps, input voltage, input resistance, and dummy load. From a magnetic field of 675 nT at 60Hz, the new magnetic energy harvesting device can provide a DC output voltage of 1.5 V. Compared with the previous device we developed, the required magnetic field is as low as 1/400 in amplitude. In contrast, the measured efficiency of the device is better than 80% when the magnetic field is larger than 20 μT.