Backpack energy harvester managed by a modified fly-back converter

A backpack energy harvester (EH) managed by a modified fly-back converter is proposed. This modified fly-back converter is controlled by a constant-on time control (COT) algorithm, The COT is one of pulse frequency modulation schemes, which switches in boundary conduction mode. Due to the structure of the modified fly-back converter and the alternator, the energy delivery to battery is proportional to the voltage of coupled capacitor. As opposed to the conventional fly-back, the proposed modified fly-back has the metal–oxide–semiconductor field-effect transistor and the capacitor exchanged in roles to achieve input rectified voltage sensing. Moreover, the proposed modified fly-back converter utilizes the internal winding inductance of the alternator utilized as part of the fly-back converter, to save the size of the converter circuitry and lower the cost. With the COT control strategy, the output power is estimated by measuring the capacitor voltage, which is converted to digitals by a 10-bit analog-to-digital converter and a time-to-digital converter. The results show clearly the fair linearity between the rotational speed of alternator, capacitor voltage and output power. Finally, the control algorithm of boundary conduction mode (BCM) is utilized for tackling well the intermittent input power generated by the EH. The average output powers of 1.166 W for striding and 1.766 W for jogging are successfully achieved.